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HUANG Yahao, JIA Zhenjiang, LI Wangcheng, WU Yangyang, MA Dongxiang, Lü Hang, ZHANG Yifan, GAO Susu
2025,39(2):1-11, DOI: 10.13870/j.cnki.stbcxb.2025.02.010
Abstract:
[Objective] To systematically categorize， summarize， and analyze the current understanding of synergistic interactions among rocks，soil，and plants，discuss the mechanisms of plants' adaptation to lithified soil environments，in order to provide theoretical support and scientific evidence for the growth of vegetation and ecological environment restoration in stony habitats. [Methods] From different dimensions such as the content and burial depth of internal rock fragments， external vegetation types， and rainfall and climatic conditions， a comprehensive analysis of the effects of rocky soil on plant growth was conducted to reveal the adaptive strategies of plants at the morphological，physiological，and molecular levels in the rocky habitats. [Results] The regulatory effect of stony soil on plant growth is closely related to factors such as rock shape，content，burial depth，climatic conditions，and plant types. The main limiting factors for plants in stony soil are soil moisture and nutrient scarcity. Under such circumstances，plants will better cope with environmental stress by regulating their own growth traits and physiological metabolism. [Conclusion] The following three aspects can be expanded and deepened in the future. 1） The synergistic effects of different types of microorganisms in rocky soil on plant growth and development，as well as the genetic adaptation mechanism of plants. 2）Seeking the optimal combination of rock fragment parameters suitable for plant growth in rocky soil environments. 3）Future research should focus on optimizing and screening suitable plants for specific regions，selecting plant varieties with strong stress resistance to promote stable plant colonization in the area，and gradually improving and enhancing the quality of the ecological environment.
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WANG Tingting, SHEN Haiou, LIANG Yushi, LIU Jianxiang, ZHAO Qiang, WANG Xueying, TIAN Li
2025,39(2):12-20,29, DOI: 10.13870/j.cnki.stbcxb.2025.02.016
Abstract:
[Objective] To investigate the characteristics of rill erosion on slopes under different slope gradients and rainfall-runoff conditions. [Methods] Continuous simulated rainfall and upper slope inflow tests were conducted to study the erosion processes on slopes with two slope gradients（5° and 10°）and across three rainfall-runoff stages （rainfall，inflow，and rainfall＋inflow）. [Results] The volumes of slope runoff and erosion increased with slope gradient. Under rainfall conditions at a 5° slope，the runoff and erosion volumes were 1.06 and 2.23 times of those under inflow conditions，respectively，while at a 10° slope，the runoff and erosion volumes were 1.26 and 3.34 times of those under inflow conditions. The runoff rate initially increased over time and then tended to stabilize. The initial runoff production time occurred earlier with increasing rainfall frequency and slope gradient，with both the stable runoff rate and sediment yield rate increasing correspondingly. Under the same slope gradient，the contribution rates of slope runoff and erosion under continuous rainfall conditions decreased with each additional rainfall event. Under continuous inflow conditions，the contribution rate of slope runoff was the highest during the first event，reaching 56.40%，while the contribution rate of slope erosion was the highest during the third event， being 87.50%. Correlation analysis revealed that slope runoff and erosion were highly significantly correlated with the rainfall inflow treatments and the interaction between slope gradient and rainfall inflow treatments（p<0.001）. Variance analysis indicated that the effects of rainfall inflow treatments on slope runoff and erosion were highly significant（p<0.001），while the effects of slope gradient were moderately significant（p<0.01）. Rill erosion accounted for 37.69%—85.45% and 53.99%—90.65% of the total slope erosion at the two slope gradients， respectively，with rill erosion increasing as the gradient increased. [Conclusion] The findings contribute to a deeper understanding of the mechanisms of rill erosion and hold significant implications for soil and water conservation efforts in the black soil region of Northeast China.
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ZHANG Xinyin, DAI Quanhou, YAN Youjin, XU Xiaojin
2025,39(2):21-29, DOI: 10.13870/j.cnki.stbcxb.2025.02.023
Abstract:
[Objective] By studying the influence of the morphology and spatial distribution of exposed bedrocks on soil erosion on karst slopes，it is helpful to deepen the understanding of erosion laws under natural rainfall conditions on karst slopes，and to provide a reference for rocky desertification control in karst areas. [Methods] Through the monitoring of natural rainfall，the effects of natural rainfall，the morphology and spatial distribution of outcropping bedrock on the sediment production of karst slopes were studied by taking different rock-soil covered slopes as the research objects. [Results] 1）The change in the morphology of exposed bedrock could significantly affect surface runoff，and such effect was rain-intensity dependent. 2）The morphology of exposed bedrock was one of the key factors in the dynamic changes of soil flow，and the spatial distribution of bedrock significantly affected the formation of soil flow under different rainfall intensities. Among them，the aggregation distribution（R-type）was the most conducive to the generation of soil flow. 3）The change of bedrock morphology mainly affected the underground runoff under the conditions of light rain and moderate rain，while in large-scale rainfall events（such as rainstorm and heavy rainstorm），the spatial distribution pattern of bedrock was closely related to the formation of underground runoff. 4）The morphology and spatial distribution of exposed bedrock played an important role in soil erosion and sediment transport during extreme rainfall events. [Conclusion] The morphological changes of exposed bedrock significantly affect the trends of surface runoff and soil flow，and such effects vary with rainfall intensity. In the future，soil erosion control measures should be taken according to different rainfall types.
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LIU Qing, SHEN Donghui, HE Jijun, LIU Zhuangzhuang, SUN Liying, CAI Qiangguo
2025,39(2):30-39,47, DOI: 10.13870/j.cnki.stbcxb.2025.02.033
Abstract:
[Objective] To explore the variation patterns and cross-sectional distribution characteristics of rill erosion and its morphological features. [Methods] Indoor artificially simulated rainfall experiments and 3D laser scanning were conducted to analyze the distribution of runoff，sediment yield and rill morphological characteristics of rill erosion under different rainfall and slope conditions. [Results] 1）When the rainfall intensity increased，the runoff and sediment yield increased significantly. When the rainfall intensity was 90 mm/h，the contribution rate of rill erosion to total erosion could reach more than 90%. 2）Rill width，depth，width-to-depth ratio and rill splitting degree were significantly affected by rainfall intensity，and all showed varying degrees of increase. Rill splitting degree and the maximum depth of rill showed a significant positive correlation with the amount of rill erosion. 3）Rill cross section varied greatly along the slope direction，the collapse of the gully wall was obvious. When the rainfall intensity was 60 mm/h，the rill cross section was mostly distributed in a "narrow and shallow" shape，When the rainfall intensity was 90 mm/h，the head and bottom of the rill were "narrow and shallow"，the middle of the rill was "wide and deep" in general. The rill erosion in the middle was more severe. 4）When the rainfall intensity was 60 and 90 mm/h，the overall value range of rill cross-sectional index were 0.46—0.79 and 0.41—0.85，respectively. When the rainfall intensity was 60 mm/h，the volatility of rill cross-sectional index increased with the increase of slope gradient，indicating that spatial differentiation of rill cross section was more obvious，and variation of the rill cross section tended to be irregular. [Conclusion] The research results can provide some theoretical support for rill erosion prevention and control.
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LIU Junyang, ZHOU Zhengchao, HAN Weixiao
2025,39(2):40-47, DOI: 10.13870/j.cnki.stbcxb.2025.02.027
Abstract:
[Objective] To explore the effects of roots on soil consolidation and erosion reduction under different planting densities. [Methods] Typical herbaceous plants， including ryegrass （Lolium perenne） and alfalfa （Medicago sativa）on the Loess Plateau were selected as the research objects. By setting three planting densities， i. e. 100，300 and 500 plants/m2，the effects of plant root growth on soil resistance to erosion were studied experimentally. [Results] During the observation period，the root characteristics showed a trend of rapid increase at first and then slow decrease，with those of ryegrass and alfalfa being the best in medium and high planting-density plots，respectively. Driven by root growth，soil organic matter content showed an increasing trend，with that of ryegrass and alfalfa increasing the most in medium and high planting-density plots，which increased by 2.44 g/kg and 1.84 g/kg，respectively. Under the combined influence of changes in root and soil characteristics，rill erodibility index decreased rapidly at first and then showed a fluctuating change during the observation period，while soil critical shear stress did not show a stable trend. Ryegrass roots had the best erosion reduction effect in the medium planting-density plot，where rill erodibility index decreased by 18.86 s/m. Alfalfa roots had the better erosion reduction effect in the medium and high planting-density plots，where rill erodibility index decreased by 13.42 s/m and 10.82 s/m， respectively. [Conclusion] Considering the effect of planting density on roots and soil characteristics，the medium density（300 plants/m2）and high density（500 plants/m2）planting patterns are suitable for soil erosion control by growing ryegrass and alfalfa，respectively.
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WANG Pu, REN Zongping, MA Xiaoni, WANG Kaibo, DONG Pengbei, HE Guokai
2025,39(2):48-56,64, DOI: 10.13870/j.cnki.stbcxb.2025.02.017
Abstract:
[Objective] The implementation of soil and water conservation measures has led to a notable reduction in the loss of soil carbon pools，while simultaneously facilitating effective control of soil erosion. However，there is a paucity of systematic understanding of the processes of carbon loss，flux characteristics and the factors that influence them under different soil and water conservation measures. [Methods] In this study，a comparative analysis of the characteristics and influencing factors associated with the loss of dissolved organic carbon（DOC） and inorganic carbon（DIC）from loess slopes under different soil and water conservation measures was conducted. These measures included terraces，grasslands，upper terraces and lower grasslands，and the upper terraces and lower bare soil. To this end，a simulated rainfall test in the field was employed to quantify the benefits of the above-mentioned soil and water conservation measures in reducing the loss of dissolved carbon from the slopes. [Results] The dissolved carbon concentration on the slope surface under each soil and water conservation measure remained relatively constant throughout the rainfall process. However，the flux of dissolved carbon loss was significantly lower than that observed on bare ground（p<0.05）. Furthermore，the loss of dissolved inorganic carbon contributed to 79.5%—83.1% of the total carbon loss. The retention benefits of grassland，the upper terraces and lower grasslands，the upper terraces and lower bare soil measures for dissolved carbon on slopes were 76.9%，56.3%，47.6% and 18.0%，respectively. The volume of flow production on the slope surface was identified as the determining factor affecting the flux of dissolved carbon loss. Furthermore，the flux of carbon loss was found to be significantly positively correlated with the flow volume. [Conclusion] This study enhances our understanding of the mechanisms through which soil carbon loss is mitigated by diverse soil and water conservation measures. It offers a scientific foundation for evaluating the carbon sink benefits of soil and water conservation on the slopes of the Loess Plateau.
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TIAN Yongsheng, MA Rui, LIU Teng, MA Yanjun
2025,39(2):57-64, DOI: 10.13870/j.cnki.stbcxb.2025.02.001
Abstract:
[Objective] To explore the effects of different sand control measures on soil physicochemical properties and enzyme activity in sand blocking and stabilization zones，and their relationships，in order to provide technical support for measure selection and benefit evaluation. [Methods] Using mobile sand dunes and Haloxylon ammodendron （CK）as the control group，and ecological cushion sand barrier+Haloxylon ammodendron（ES），nylon mesh sand barrier+H. ammodendron（NS），woven bag sand barrier+H. ammodendron（WS），grass square grid sand barrier+H. ammodendron（GS），and clay sand barrier+H. ammodendron（CS）as the test groups，physical and chemical properties and enzyme activities of soil within 0~60 cm depth for six different sand control measures were analyzed. [Results] Compared with CK，there were significant changes in soil physicochemical properties and enzyme activities among the other five different sand control measures. 1）Within the depth range of 0~60 cm，there was no significant change in soil pH，but soil moisture content（SWC）increased with increasing soil depth. The mass fractions of soil organic carbon（SOC），total nitrogen（TN），total phosphorus（TP），and total potassium （TK）decreased with increasing soil depth. Compared with CK，the other five different sand control measures had a significant increase in soil nutrient content，with NS showing the most significant increase. 2）Under different desertification control measures，soil enzyme activities of NS measure were the highest，followed by that of GS，and that of CS were the lowest. Within the depth range of 0~60 cm，soil enzyme activities showed a decreasing trend. 3）There were significant correlations between soil physicochemical properties and soil enzyme activities. The contribution of soil physicochemical properties to soil enzyme activities varied under different desertification control measures，and soil enzyme activities were mainly influenced by TK，SOC，and SWC. [Conclusion] Five different sand control measures have varying degrees of promoting effects on soil physicochemical properties and enzyme activities，among which NS sand control measures have the best ecological benefits and long-term stability.
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WANG Jie, ZHENG Hao, LI Zihan, REN Shaocong, WANG Shuoguo, LIAN Qijie, WEI Yujie, CAI Chongfa
2025,39(2):65-73,81, DOI: 10.13870/j.cnki.stbcxb.2025.02.015
Abstract:
[Objective] The effective mixing depth is an essential parameter for quantifying and predicting solute loss. It is of great significance to quantify the effective mixing depth of texture-differentiated soils and investigate the response of effective mixing depth to soil erosion，and solute loss in the modeling of agricultural non-point source pollution. [Methods] The topsoils of five texturally distinct dry croplands in the Danjiangkou Reservoir Region were selected as the research object. The bromine ion tracer method was employed to quantify the effective mixing depth and its dynamic changes in texturally distinct soils. Simulated rainfall tests were conducted according to different bromine application depths[0（soil surface），0.5，1，2 and 5 cm]to determine the process of soil erosion and solute loss and analyze their responses to the effective mixing depth. [Results] Under the experimental conditions established in this study，the effective mixing depths during rainfall exhibited a range of 0.32—0.72， 0.11—0.57， 0.44—2.41， 0.11—1.04， and 0.13—0.28 cm. The effective mixing depths were found to be significantly affected by the clay content and soil texture（F=39.27，p<0.001）. However，the effective mixing depths of different textured soils were significantly affected due to the differences in infiltration and flow production processes of different soil textures. Consequently，a significant linear relationship was not observed between the two. Furthermore，the effective mixing depth demonstrated a dynamic variation during the rainfall process，and exhibited a pronounced power function relationship with rainfall duration（R2 >0.80）. Furthermore，a notable distinction was observed in the soil erosion and sand production processes across varying effective mixing depths （F>12.068，p<0.001）. Regression analysis demonstrated that the mean effective mixing depth exhibited a significant linear correlation with cumulative soil runoff and cumulative bromine loss（R2>0.92），as well as a significant exponential function relationship with sand production rate，sediment concentration，and cumulative sand production（R2>0.94）. [Conclusion] The effective mixing depths of various textured soils exhibit notable disparities. A substantial linear or exponential correlation exists between the effective mixing depth，soil erosion， and solute loss indices. This correlation can be inverted through the runoff generation and sediment yield characteristics of the effective mixing depth，thereby enhancing the precision of the solute loss model.
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ZHANG Hanyu, LI Jiaqian, ZHAO Yajie, LI Jingjiang, LIU Zhihua, FANG Nufang, LIU Qianjin
2025,39(2):74-81, DOI: 10.13870/j.cnki.stbcxb.2025.02.002
Abstract:
[Objective] Research on the effects of the duration of straw returning on rill erosion resistance can provide scientific evidence for rill erosion modeling and controlling in sloping farmland. [Methods] Taking straw returning durations of 0 years（CK），3—4 years（R1），5—6 years（R2），7—8 years（R3），9—10 years（R4）， 15 years（R5），and 20 years（R6）as the study subjects，soil samples were collected and analyzed. Partial least squares regression analysis was applied to identify the main controlling factors of soil erosion resistance under straw returning conditions. [Results] 1） With the increase of straw returning duration， rill erodibility（Kd） first decreased，then increased，and decreased again. The Kd values of R2，R3，R5，and R6 were significantly lower than that of CK[170.38 cm3/（N·s）]. With the increase in the duration of straw returning，soil critical shear stress （τc）showed a trend of first increasing and then decreasing，with the pattern of R1=R3>R2>CK>R4>R6> R5，although the differences among treatments were not significant. 2）Compared to CK，all straw returning treatments reduced soil bulk density（BD），the content of water-stable aggregates >0.25 mm（WG0.25），and exchangeable sodium ions，while increasing total porosity and soil saturated moisture content（SWC），although the effects on soil properties varied across treatments. 3）Among all the main controlling factors of Kd，Kd decreased with the increases in exchangeable magnesium ions，soil organic matter，humic substances，fulvic acid （FA），humin，and exchangeable calcium ions，but increased with the increase in WG0.25. Among all the main controlling factors of τc，τc was positively correlated with FA，dry-sieved aggregates >0.25 mm，and BD，and negatively correlated with soil moisture content and SWC. [Conclusion] Straw returning for 5—8 years or 15—20 years significantly reduced Kd，helped to improve soil erosion resistance and can effectively control rill erosion.
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YANG Tao, CHEN Yuanhua, CHEN Feng, XU Changxu, ZHUANG Yanhua, TU Xiangming, CHEN Jingrui
2025,39(2):82-91, DOI: 10.13870/j.cnki.stbcxb.2025.02.003
Abstract:
[Objective] This study aimed to clarify the characteristics of soil nutrient accumulation and nitrogen and phosphorus loss for the greenhouse vegetable in Jiangxi Province，thereby providing scientific data for the accurate evaluation on pollution risk and promoting the healthy development of vegetable industry in this province. [Methods] Multipoint sampling was used for analysis cumulative amount of nutrients within the 0—100 cm depth soil layer in greenhouse vegetable throughout 11 cities and districts of this province，and in situ monitoring was used to analyze the characteristics of nitrogen and phosphorus loss. [Results] 1）The soil was severely acidified. The soil layers within 0—20 and 20—40 cm under surface showed pH values of 5.44 and 5.56，respectively. 2）The soil nutrient content in 0—20 cm soil layer was at the medium fertility level，and the soil nutrient increased with the extension of planting time when the planting years were less than 10 years，and began to decline when the planting years were 11— 20 years（except for available phosphorus）. 3）The runoff from greenhouse vegetable is mainly driven by rainfall and has the characteristics of high volume and low concentration；runoff occurs in the period from February to June accounts for more than 75% of the annual runoff amount and more than 60% of the annual nitrogen and phosphorus loss. [Conclusion] The 6—10 years might be a“turning point”for the cumulative contents of nutrients in greenhouse vegetable plots. Excessive use of nutrients after 6—10 years could not increase the storage capacity of the soil，but it might increase the risk of pollution caused by the accumulation of available nutrients. Due to the degenerated function of regulation，storage and purification of ditches and ponds，the generation of short-term，high-flow and low-concentration runoff water from greenhouse vegetable is difficult to be consumed in farmland ecosystem locally in at present. Therefore， the construction of greenhouse vegetable-single season rice composite farming model may be an effective means to solve the non-point source pollution of from greenhouse vegetable in red soil areas in southern China.
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JIANG Yudi, YU Yang, WANG Zhengkun, LIU Dianjun
2025,39(2):92-101,110, DOI: 10.13870/j.cnki.stbcxb.2025.02.004
Abstract:
[Objective] Conducting research on lake area changes on the Inner Mongolia Plateau is of great significance for deep understanding of regional water resource changes. [Methods] The Google Earth Engine （GEE）platform and Landsat image data were used to obtain annual lake area data on the Inner Mongolia Plateau from 1988 to 2021，and methods such as trend testing and hierarchical segmentation were used to analyze the spatiotemporal change characteristics of lakes and their influencing factors. [Results] 1）From 1988 to 2021，the area and number of lakes in Inner Mongolia showed a trend of first reduction and then recovery. On an inter-annual scale，the lake area was the largest in 2021，reaching 4 363.63 km2，and the smallest in 2002，only 1 915.61 km2. In terms of the number of lakes，the number of lakes larger than 1 km2 increased from 71 in 2002 to 458 in 2021. 2）Between 2012 and 2021，the area of lakes on the Inner Mongolia Plateau gradually recovered，and mainly concentrated in Alxa League，Xing’an League and Hulunbuir City. 3）The changes in lake area on the Inner Mongolia Plateau were mainly affected by climate change and human activities. From 1988 to 2012，human activities were the main driving force of lake area changes，and lake area was significantly positively correlated with precipitation. There was a significant negative correlation between lake area and irrigation，grazing and coal production. After 2012，climate factors were the main factors affecting changes in lake area. [Conclusion] The results elucidate the relationship between lake area changes，climate and human activities on the Inner Mongolia Plateau，and provide a scientific basis for ecological protection and restoration of plateau lakes.
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MA Dawei, MA Yanjun, GUO Yongchun, ZENG Yu, MA Rui, ZHU Jiangang
2025,39(2):102-110, DOI: 10.13870/j.cnki.stbcxb.2025.02.040
Abstract:
[Objective] To explore the changes of soil physical and chemical properties and enzyme activities of four vegetation types in desert saline-alkali lands in the Hexi Corridor and their influencing factors，and to provide a theoretical basis for soil nutrient cycling and regulation mechanism in desert saline-alkali lands. [Methods] Taking the desert saline-alkali soil in the Hexi Corridor as the research object，four typical vegetation types，including Lycium ruthenicum Murr. single community（HH），L. ruthenicum and Phragmites australis community（HL）， L. ruthenicum and Alhagi camelorum Fisch. community（HT），L. ruthenicum and Tamarix chinensis Lour. community（HC），were selected. Three replicate plots were set up for each vegetation type. Through the combination of field investigation and indoor analysis，soil physical and chemical properties（including organic carbon，total nitrogen，total phosphorus）and enzyme activities（including urease，alkaline phosphatase，nitrate reductase，nitrite reductase）of the four vegetation types were measured. Variance analysis and redundancy analysis were used to evaluate the differences in soil physical and chemical properties and enzyme activities，and the influencing factors were analyzed. [Results] In the soil of the four different vegetation types in the Hexi Corridor，organic carbon content increased with the increase of soil depth，being the highest in HC and the lowest in HH，and the difference was significant（p<0.05）. Total nitrogen content decreased with the increase of soil depth，being the highest in HH and the lowest in HC，and the difference was significant（p<0.05）. There was no significant change in total phosphorus（p>0.05）. The activities of urease，alkaline phosphatase，nitrate reductase and nitrite reductase decreased with the increase of soil depth，showing the phenomenon of surface aggregation. The activities of alkaline phosphatase，nitrate reductase and nitrite reductase were significantly different among different vegetation types（p<0.05），being the highest in HL，HH and HT，and the lowest in HT，HC and HH， respectively. Total nitrogen content was significantly positively correlated with urease and nitrate reductase activities（p<0.05）. In the 20—40 cm soil layer，organic carbon content was significantly negatively correlated with urease and nitrate reductase activities（p<0.05）. [Conclusion] The changes of different vegetation types and soil layers cause significant changes in soil physical and chemical properties，and then regulate the changes and distribution of soil enzyme activities. Soil total nitrogen and organic carbon contents are the key factors affecting soil enzyme activities，and can better explain the distribution and change characteristics of soil enzyme activities.
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ZHU Wanting, ZHU Yonghua, WANG Qimeng, Lü Haishen, LIU Mingwen, WANG Yining, LU Wen, PENG Yujie, XU Haiting, FANG Yimin
2025,39(2):111-124, DOI: 10.13870/j.cnki.stbcxb.2025.02.014
Abstract:
[Objective] The sources and quantitative characteristics of soil moisture in the root zone of crops in the Huaibei Plain from 1990 to 2022 were explored to provide scientific guidance for crop irrigation management and water resource utilization. [Methods] The contribution of precipitation and groundwater to soil water in the root zone was calculated by Pearson correlation analysis and multiple regression，and soil water quantitative simulation was performed using multiple linear regression and long short-term memory network（LSTM）model. [Results] 1）For summer corn，in the 0—10 cm soil layer，except for the 55% contribution of precipitation during the seedlingjointing period，the contribution of groundwater in other stages could reach 61%—68%；in the soil layer below 10 cm，the soil water in the root zone mainly came from soil water in the adjacent upper layer，accounting for more than 74%. In the later stage，the root system gradually growed to 100 cm，especially in the 40—80 cm soil layer， the contribution of groundwater to soil water increased significantly，accounting for 9%—22%. 2）For winter wheat，in the 0—10 cm soil layer，except for the sowing-seedling period and the greening-jointing period，the contribution of groundwater in other stages could reach 54%—73%；in the soil layer below 10 cm，the soil water in the root zone mainly came from soil water in the adjacent upper layer，accounting for more than 63%. However，in the 40—80 cm soil layer，the contribution of groundwater and precipitation increased. 3）The LSTM model was more stable and accurate than multiple linear regression in quantitatively simulating soil water. The model evaluation index could reach R2>0.6 and MSE<10，which could better reflect the dynamic changes of soil moisture. The application of the above simulation results at other stations in the Huaibei Plain further verified the feasibility of the model. [Conclusion] The main source of soil water in the 0—10 cm layer for summer corn is groundwater，and the main source of soil water in the 0—10 cm layer for winter wheat is precipitation；the main source of soil water below 10 cm is soil water in the adjacent upper layer（including precipitation，irrigation water， etc.）. Performing quantitative simulation based on the sources of soil water in the root zone at different growth stages，and dynamically adjusting the irrigation plan through the changing trend of soil moisture in the root zone of the crop is helpful to optimize irrigation management and improve water resource utilization efficiency.
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ZHENG Lixuan, WU Fuzhong, YANG Qiao, PENG Yan, AN Nannan, JIANG Hualing, ZHENG Yuchen, YUE Kai
2025,39(2):125-134, DOI: 10.13870/j.cnki.stbcxb.2025.02.032
Abstract:
[Objective] In order to investigate the effects of forest type conversion on the hydrophysical characteristics of forest soils. [Methods] The effects of forest type conversion on soil porosity，permeability，and matric potential，using subtropical natural evergreen broad-leaved forests and the secondary forests were compared，Castanopsis carlesii artificial forests，and Cunninghamia lanceolata artificial forests derived from them as research subjects. [Results] 1）After forest type conversion，total soil porosity in the lower soil layer of secondary forests significantly increased by 5.43% compared to natural forests. Soil matric potential also significantly increased in C. lanceolata artificial forests during the dry season by 5.01 kPa compared to natural forests. However，the variation of soil permeability in different forest types was not significant. 2）In the 0~40 cm soil layer of the four forest types，soil particles were mainly dominated by sand particles， but only clay particles and silt particles showed a significant correlation with total soil porosity，and soil particle composition was not the controlling factor for soil water-holding indicators under forest type conversion. 3）The main controlling factors for soil water-holding indicators were soil bulk density and soil moisture，with significant correlations between soil bulk density and each water-holding indicator，while forest conversion leaded to changes in soil bulk density and soil moisture，thereby causing changes in soil water-holding performance. [Conclusion] Forest type conversion has a significant impact on the hydrophysical parameters of subtropical region soils，with the conversion from natural forests to secondary forests being beneficial for water conservation or soil retention，and conversion to C. lanceolata artificial forests requiring soil amelioration measures to optimize their water retention and permeability. The results can provide a theoretical basis and data support for sustainable management of subtropical forests and water conservation.
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2025,39(2):135-143,154, DOI: 10.13870/j.cnki.stbcxb.2025.02.018
Abstract:
[Objective] To thoroughly investigate the effects of extreme climate events on the net primary productivity（NPP）of vegetation in the Qinba Mountain area. [Methods] Using the Qinba Mountain area as an example area，161 meteorological station observations from 1960 to 2023 and MOD17A3 dataset from 2001 to 2020 were used，and fitted regression，ridge regression and other analytical methods were applied to study the spatial and temporal evolution of the two and to quantify the contribution of extreme climate indices to the trend of NPP change. [Results] 1）the overall development of NPP in the study area was favourable，with an average annual growth rate of 5.02 g/（m2·a）（calculated by C）. 2）Extreme warm events significantly increased and extreme cold events significantly decreased in the Qinba Mountain area from 1960 to 2023，whereas the changes in extreme precipitation events were not obvious. 3）Changes in the CSDI，ID，TN10p，CDD，R10，R2p>0 and TR had a positive impact on the NPP trends，with the greatest contribution from the TN10p；changes in the Rx5day negatively affected the NPP trends. [Conclusion] The study can provide data or theoretical support for the conservation of terrestrial ecosystems in the Qinba Mountain area under the background of climate warming and for coping with extreme climate events.
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ZENG Hong, DONG Tianfu, YANG Jing, ZHANG Jun, NIE Yunpeng, CHEN Hongsong
2025,39(2):144-154, DOI: 10.13870/j.cnki.stbcxb.2025.02.011
Abstract:
[Objective] The strong dissolvability of carbonate rock leads to the spatial distribution of karst soil and bedrock，and the outcroppings of bedrock are common，but the mechanism of their influence on hydrological processes is still unclear. In order to investigate the influence of outcropped bedrock on soil water infiltration，the soil infiltration rate at different distances of outcropped bedrock was measured by single-loop infiltration method. [Methods] Taking the soil 20 and 100 cm away from the bedrock as the research objects，the characteristics of preferential flow were studied by the bright blue staining and tracing method. [Results] The capillary porosity and organic matter content of non-bedrock soil were significantly higher than those of bedrock soil（p<0.05），but the soil bulk density was significantly lower（p<0.05）. The infiltration parameters（initial，stable and average infiltration rate） of non-bedrock soil were higher than that of bedrock soil. The area of staining area and preferential flow path increased with the distance from the exposed bedrock. These results indicate that the infiltration capacity and preferential flow frequency of non-bedrock soils are stronger than those of bedrock soils. Rock surface roughness was an important factor affecting soil water infiltration process，and soil infiltration rate increased with the increase of rock surface roughness，and there was a very significant positive correlation between soil roughness and soil infiltration characteristics（p<0.01）. Kostiakov Model（R2=0.89），Horton Model（R2= 0.80）and Philip Model（R2=0.72）are the best fitting models for soil water infiltration process considering the influence of bedrock outcrop. [Conclusion] This study identifies the influence of exposed bedrock on soil infiltration characteristics and emphasizes the controlling role of rock surface roughness.
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2025,39(2):155-166, DOI: 10.13870/j.cnki.stbcxb.2025.02.009
Abstract:
[Objective] The impact of land use change on the evolution of ecological profit and loss under multiscenario simulation in Chaoyang was explored to provide a reference for the land space planning and ecological environment protection of the agro-pastoral ecotone in Northeast China. [Methods] Based on the land use data of Chaoyang in 2000，2010 and 2020，the Markov-PLUS model and ecological footprint model were used to analyze and predict the evolution characteristics of land use structure and ecological profit and loss of Chaoyang under four scenarios from 2000 to 2030. On this basis，the response of ecological profit and loss to land use change were explored by using the ecological elasticity model. [Results] 1）The land use change in Chaoyang from 2000 to 2020 was quite drastic. Cultivated land and grassland were the main types of land use，accounting for more than 80% of the total land area. 2）From 2000 to 2020，Chaoyang showed a change from ecological deficit to ecological surplus，with an overall increment of 273.07×104 hm2，showing a spatial distribution pattern of high in the west and low in the east. The rapid increase of ecological carrying capacity of grassland，woodland and water area was the main reason for the increase of ecological surplus in Chaoyang. 3）Under four scenarios from 2020 to 2030，the ecological surplus of Chaoyang increased significantly，with ecological priority scenario（99.66×104 hm2）> cultivated land protection scenario（98.93×104 hm2）> natural development scenario（98.02×104 hm2）> urban development scenario（97.87×104 hm2）. The high-value area of ecological surplus migrated and expanded from west to east，while the low value-area concentrated in the urban center. 4）The ecological profit and loss of Chaoyang was elastic to land use change，and the ecological elasticity coefficient showed an increasing trend. [Conclusion] Land use change significantly affects ecological profit and loss. Optimizing land use structure can effectively improve regional ecological environment.
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SUN Guangru, QIU Guoqiang, JIANG Xiaojun, WANG Xuewei, WANG Jing
2025,39(2):167-178,190, DOI: 10.13870/j.cnki.stbcxb.2025.02.031
Abstract:
[Objective] As newly constructed river and lake system interconnection projects，canals change the connectivity pattern of the river and lake system interconnection network. Furthermore，it affects the pathways of material，energy and risk across the network，but the mechanism by which newly constructed canals affect the the river and lake system interconnection network is not yet clear. [Methods] The area around Laizhou Bay was selected as the study area. The SWAT+model and graph theory method were employed to analyze the hydrological connectivity of the river and lake system interconnection network under two scenarios，with and without the canal. This was done to explore the differences in the impacts of canals on the various river basins，as well as on different types of water bodies，such as lakes，low-flow streams and high-flow streams. [Results] In comparison to other river basins，the hydrological connectivity of the Weihe River Basin and the Mihe River Basin is greater under the no-canal scenario，with the lowest degree of influence from the canal. The Yellow River-the Guangli River Basin and the Dagu River-the Jiaolai River Basin are influenced by the canal，and the greatest improvement is observed，with the values of betweenness centrality and closeness centrality indicators both increasing by more than 20 times. The impact of canals on the hydrological connectivity of diverse basins is largely contingent upon river network structure，the number and the location of canal connections. Low-flow streams exhibited the highest value of closeness centrality indicator，which is 3.4 times and 1.5 times the average value of lakes and high-flow streams，respectively. Lakes is the most affected by the canal，while low-flow streams are the least affected. This suggests that the lower the disturbance-resistant capacity of the water body，the more sensitive it is to the canal's response. The impact of canals on different water body types is dominated by the distance of the water body from the central water bodies of the network. [Conclusion] The planning of regional river and lake system interconnection networks should take into account growth mechanisms，including' preferential attachment' of betweenness centrality and anti-'preferential attachment' of closeness centrality. This will enable a more appropriate avoidance of the risk of unintended growth in hydrological connectivity.
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Variation of Extreme Precipitation and Its Influence on Sediment Transport in Xiangjiang River Basin
KANG Zihan, MO Shuhong, WANG Jingjing, JIANG Kaixin, JIANG Yubo
2025,39(2):179-190, DOI: 10.13870/j.cnki.stbcxb.2025.02.022
Abstract:
[Objective] To explore the variation of extreme precipitation in Xiangjiang River basin and its influencing factors on sediment transport. [Methods] Daily precipitation data from 13 meteorological stations in Xiangjiang River basin and its surrounding areas during 1965—2018 were collected， and seven extreme precipitation indices were selected and calculated using the RClimDex model. The spatial distribution characteristics were analyzed by linear fitting method and five-year moving average method，and the Cv value of each index，Spearman correlation coefficients and Kendall correlation coefficients were calculated. The temporal characteristics were observed from the linear exponential change and the five-year moving average process line. M-K mutation test，Lee-Heghinian test and ordered clustering method were used to test the mutation of the average annual sediment transport in Xiangjiang River basin. The contribution rate of extreme precipitation index to the variation of sediment transport during this period was quantitatively analyzed by double accumulation curve. [Results] 1）The interannual variation trend of extreme precipitation indices in the basin during 54 years showed an increasing trend except for CWD（consecutive wet days）. The duration of extreme precipitation events was prolonged，and the precipitation and precipitation intensity increased significantly. 2）The spatial distribution of each precipitation index was basically consistent with the topographic characteristics， and the trend was gradually increasing from the southwest to the northeast of the basin，and the maximum values of the seven indices were found at Nanyue Station. 3）Abrupt changes occurred in 1984 and 1997. During 1985—1997，the extreme precipitation index R99P（extremely wet days）had the greatest impact on the reduction of sediment transport in the basin，with a contribution rate of 10.5%. During 1998—2018，the same extreme precipitation index R95P（very wet days）had a change in the reduction of sediment transport. The contribution rate was 18.1%，but the influence of extreme precipitation index on sediment transport reduction was less than 20%. [Conclusion] Extreme precipitation has a certain effect on the reduction of sediment transport in the basin，but human activities are still the main factor leading to the reduction of sediment transport.
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WANG Peng, MA Yilun, CHENG Jing, XU Mingxiang, SU Shengliang, PU Yong, HAN Lei, YANG Fang
2025,39(2):191-199, DOI: 10.13870/j.cnki.stbcxb.2025.02.029
Abstract:
[Objective] To assess the water conservation capacity of the upper Yellow River region，and to provide a scientific basis for the ecological protection and high-quality development of the Yellow River basin. [Methods] Taking Ningxia Province as a case area，the spatial and temporal evolution trend of the water conservation capacity of Ningxia Province from 1990 to 2020 was calculated based on the InVEST model，the Hurst index and the geodetector model， and its key influencing factors were identified. [Results] The land use pattern of Ningxia Province changed significantly，except for the unused land，all other land use types showed different degrees of increasing trends. The water conservation volume of Ningxia showed an increasing trend from 1990 to 2020，with an increase of about 0.009 mm/a. The spatial distribution pattern of the water conservation capacity showed a trend of“low in the north and high in the south”，and had a significant spatial clustering characteristic. The change of water conservation function in Ningxia was not sustainable，and would face the risk of degradation in the future. Precipitation was the main factor affecting the water conservation capacity of Ningxia，followed by elevation and slope，while vegetation cover and evapotranspiration had the lowest degree of influence. [Conclusion] The water conservation function and its sustainability of Ningxia Province recovered during the study period，but further enhancement of water conservation capacity is still needed to cope with future risk of degradation. The results of the study can provide a scientific basis for the construction of a pioneer area for ecological protection and high-quality development in the Yellow River Basin.
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YANG Chenggaoge, WANG Haipeng, TIAN Peng, TANG Chongjun, XIE Meixiang, BI Bo, ZHAO Guangju, GENG Ren, ZHOU Lu, YOU Junjian
2025,39(2):200-208,217, DOI: 10.13870/j.cnki.stbcxb.2025.02.019
Abstract:
[Objective] The aim of this study was to investigate the spatial and temporal variation of sediment transport in the Ganjiang River Basin，and to explore the contribution of climate change and human activities to sediment changes of the basin quantitatively，in order to provide a reference for soil erosion control，water and sediment resource management. [Methods] Data of sediment transport monitoring and precipitation history from 1960 to 2020 at 15 main hydrological observation stations located in upper，middle and lower reaches of the Ganjiang River Basin were collected. The spatial and temporal changes of sediment transport were analyzed by the linear trend method，Mann-Kendall trend test and Pettitt mutation test were used in combination with double mass curve to quantitatively analyze the contribution of the influencing factors. [Results] 1）Annual sediment transport in the upper，middle and lower reaches of the Ganjiang River Basin showed a significant decreasing trend from 1960 to 2020（|Z| >2.58）. The reduction rate of Waizhou，Xiajiang and four stations of the upper reaches were 2.143×105，1.661×105 and 0.812×105 t/a，respectively，and there were mutations in sediment transport in 1994， 1992 and 1998. 2）The multi-year average sediment transport modulus of the sub-basins were high in the south and low in the north，and the temporal variation showed a trend of increasing first and then decreasing in the upper reaches，and decreasing in the middle and lower reaches. Compared with 1960—1987，the average sediment transport modulus in the upper，middle and lower reaches decreased by 51.32%，104.95% and 105.03%，respectively from 2001 to 2020. 3）The temporal and spatial variation of sediment load in the basin was affected by the topography，soil and water conservation measures，etc. Human activities were the leading factor for the reduction of sediment transport in the Ganjiang River Basin. [Conclusion] The sediment production from erosion in the Ganjiang River Basin has significantly reduced，but the upper reaches are still the key areas for soil erosion control in the future.
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HE Pingsheng, LI Jinlin, HE Xiubin, TANG Qiang, WU Shengjun, HUANG Ping
2025,39(2):209-217, DOI: 10.13870/j.cnki.stbcxb.2025.02.028
Abstract:
[Objective] To investigate the elevation-based differentiation in moisture and nutrients of sedimentary layer in the water-level fluctuation zone（WLFZ）and provide a scientific basis for reservoir management. [Methods] The WLFZ of the Three Gorges Reservoir was selected as the research object and layered sample were collected from a representative slope. The particle size distribution，nutrient concentration，and moisture content were measured，and the differences in sediment properties at different elevations were analyzed. [Results] 1）The particles of the sediment in the WLFZ were relatively fine，with a median particle size ranging from 6.1 to 13.5 μm and an average of 8.7 μm. No significant difference in median particle size was observed among sediments at varying elevations（p>0.05）. The particle size distribution of the sediments was dominated by silt，with an average volume content of 82.7%，and the contents of clay and sand were 14.2% and 3.1%，respectively. 2）The mean total organic carbon（TOC），total nitrogen（TN），and total phosphorus（TP）contents of the sediments in the WLFZ were 18.82，1.24 and 0.75 g/kg， respectively. The stoichiometric ratios of carbon，nitrogen，and phosphorus（C∶N，C∶P，and N∶P）were 15.25， 25.26 and 1.68，respectively. Significant differences were observed in the overall trends of nutrient content changes with elevation. Specifically，TOC and TN contents increased significantly with increasing elevation（p<0.05），while TP content did not show a clear trend. The stoichiometric ratios of C∶P and N∶P in the sediments increased with increasing elevation，while the C∶N ratio showed no significant trend（p>0.05）. 3）The average mass water content of the sediments in the WLFZ was 28.63%，and no significant elevation-based spatial differentiation was observed（p> 0.05）. 4）The particle size distribution，nutrient content，and moisture content of sediments in the WLFZ were distributed in striated layers formed by alternating high and low values along the profile. [Conclusion] There is a significant elevation-based differentiation in the nutrient content of the sediments in the WLFZ of the Three Gorges Reservoir，but there is no significant spatial differentiation in particle composition and mass water content.
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FU Li, PENG Shuangyun, GONG Luping, HUANG Bangmei, MA Dongling, ZHU Ziyi
2025,39(2):218-229, DOI: 10.13870/j.cnki.stbcxb.2025.02.005
Abstract:
[Objective] Taking the Pearl River source region，a typical karst area，as the research object，this study aimed to construct a reasonable ecological security pattern，analyze the evolution of the ecological security pattern from 1990 to 2020，and provide scientific support for strengthening biodiversity conservation and ecological restoration in karst regions. [Methods] Based on the evaluation of ecosystem service importance and ecological sensitivity，in combination with methods such as MSPA，MCR，and the gravity model，the ecological security pattern of the Pearl River source region from 1990 to 2020 was constructed，and its spatial-temporal evolution characteristics were analyzed. [Results] 1）Ecological sources were concentrated in the southern part of Qujing City and the border with Wenshan Prefecture，while they were scattered in the western part of Yuxi City，the border of Kunming City with Qujing City and Honghe Prefecture，the southern part of Honghe Prefecture，and the northeastern part of Qujing City. From 1990 to 2020，the area of ecological sources showed a trend of increasing first and then decreasing，and reaching a maximum in 2000. 2）The comprehensive resistance surface exhibited obvious spatial heterogeneity，and the area and range of high-resistance zones had been continuously expanding from 1990 to 2020. 3）In 1990 and 2000，55 ecological corridors were identified，which decreased to 45 in 2010 and 2020. Important ecological nodes were mainly distributed in ecologically sensitive areas such as the border of Qujing City，Yuxi City，and Honghe Prefecture. 4）The overall structure of the ecological security pattern in the Pearl River source region was consistent with the direction of rivers，but due to human activities，the ecological security pattern in the Nanpan River Basin was fragile. [Conclusion] Urbanization，land use change，and increased intensity of human activities are the main factors affecting the evolution of the ecological security pattern in the Pearl River source region. In the future，focus should be placed on protecting key ecological sources， restoring and constructing ecological corridors， developing eco-friendly industries， and establishing a comprehensive ecological monitoring network to improve the stability and sustainability of the karst ecosystem.
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FANG Baihan, LI Yueyao, YANG Maoqi, GUO Xiaowen, YE Yang, GUO Huijuan, MIN Wei
2025,39(2):230-237,249, DOI: 10.13870/j.cnki.stbcxb.2025.02.034
Abstract:
[Objective] Based on the rational utilization of cotton straw resources，this study studied the effects of different amounts of cotton straw returning on soil physicochemical properties，nitrate-nitrogen leaching，nutrient invertase activity and cotton growth，in order to provide a theoretical basis for soil fertility improvement and sustainable agriculture development in drip-irrigated cotton fields in arid areas. [Methods] Four treatments were set up，including no returning（CK），half returning of cotton straw（50%ST），full returning of cotton straw （100%ST），and double returning of cotton straw（200%ST）. [Results] The proportion of large aggregates in soil was significantly increased by different rates of cotton straw returning to the field，and the increase under cotton straw returning to the field by 88.44% to 126.80% compared with no return. Meanwhile，cotton straw returning significantly increased the mean mass diameter and geometric mean diameter of aggregates， and enhanced the stability of aggregates. 50%ST，100%ST and 200%ST significantly decreased soil bulk density， increased soil porosity and soil water content，compared with CK，with soil water content being increased by 22.83% to 42.06%. Cotton straw returning to the field significantly increased the contents of soil organic matter， total nitrogen，alkali-hydrolyzed nitrogen，available phosphorus and available potassium. Compared with CK， 100%ST and 200%ST significantly decreased nitrate-nitrogen leaching in the 0—100 cm soil. The activities of soil urease and alkaline protease were significantly increased with the increase of cotton straw returning rate. 50%ST significantly increased cotton plant height， SPAD， Chl value， and dry matter weight. 50%ST， 100%ST，and 200%ST significantly increase the absorption of nitrogen，phosphorus，and potassium by cotton， thereby promoting the growth and development of cotton. Cotton straw returning significantly increased seed cotton yield by 4.61% to 12.59%，and nitrogen-use efficiency was significantly increased by 7.41% to 17.52%，compared with CK. [Conclusion] Cotton straw returning to the field can increase the proportion of large aggregates，reduce soil bulk density，increase soil porosity and water content，improve soil physical structure，and increase soil nutrient content，reduce nutrient leaching，thereby increasing the activities of soil nutrient convertases，promoting the growth and nutrient absorption of cotton，and improve the yield of seed cotton and nitrogen-utilization efficiency.
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ZHONG Yun, HUANG Zhikun, ZHU Shijiang, HAO Kun, ZHU Zirong, ZHANG Wei, CHEN Hongde
2025,39(2):238-249, DOI: 10.13870/j.cnki.stbcxb.2025.02.036
Abstract:
[Objective] This study investigated the effects of regulated deficit irrigation on leaf nutrient levels （nitrogen，phosphorus，and potassium），enzyme activities（superoxide dismutase，peroxidase，and catalase），and root-zone soil nutrients（nitrate-nitrogen，available phosphorus，and available potassium）during the fruit expansion （Ⅲ）and coloration-sugar accumulation stages（Ⅳ）of citrus in western Hubei Province. [Methods] Six-year-old “Ehime 28”citrus trees in the western Hubei region were selected as the research subjects. Full irrigation served as the control（CK：daily irrigation volumes of 4.0 and 2.5 L during the fruit expansion stage（Stage Ⅲ ）and coloration-sugar accumulation stage（Stage Ⅳ ），respectively）. Four deficit irrigation treatments were applied during both Stage Ⅲ and Stage Ⅳ ，including mild deficit（LD：70% of CK），moderate deficit 1（MD1：55% of CK），moderate deficit 2（MD2：40% of CK），and severe deficit（SD：30% of CK）. The aim was to explore the response patterns of soil nutrients，citrus leaf nutrients，antioxidant enzyme activities，and root-zone soil nutrients to water stress under drip irrigation across different growth stages. [Results] 1） The Ⅳ -MD1 treatment significantly promoted the increase in leaf nitrogen，phosphorus，and potassium contents，with their respective mass fractions increasing by 8.05%，2.13% and 12.42% compared to the control group. Moreover，this treatment achieved the highest rates of nutrient accumulation and growth in the leaves. 2）The Ⅲ-MD1 treatment effectively enhanced the antioxidant defense capacity of citrus trees，with the activities of superoxide dismutase（SOD）and peroxidase（POD）increasing by 63.3% and 104.5%，respectively. 3）The Ⅲ-MD1 treatment markedly enhanced nitrate nitrogen and available phosphorus contents in the upper and middle soil layers，with respective increases of 74.54% and 17.61% in the upper layer，and 73.53% and 43.58% in the middle layer. Additionally，the IV-MD1 treatment significantly improved the vertical distribution of soil nutrients，effectively reducing nutrient leaching losses. This treatment also increased the available potassium content in the upper and middle soil layers by 59.23% and 51.67%，respectively. 4）Canonical correlation analysis revealed significant relationships between soil and leaf nutrient elements. Leaf phosphorus and potassium contents were positively correlated with available potassium in the soil，while they were negatively correlated with soil nitrate-nitrogen，available phosphorus，and leaf nitrogen. [Conclusion] The Ⅳ -MD1 treatment effectively promotes the accumulation of soil and leaf nutrients and enhances the activity of protective enzymes，making it a suitable water-saving management strategy for drip irrigation for citrus cultivation in western Hubei. The findings provide a theoretical basis for optimizing citrus irrigation practices and improving fruit quality.
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LIANG Qing, ZHANG Tibin, CHENG Yu, GAO Weiqiang, KUANG Yuxin, FENG Hao
2025,39(2):250-259, DOI: 10.13870/j.cnki.stbcxb.2025.02.039
Abstract:
[Objective] We conducted a field experiment to investigate the effects of intercropping green manure crops and their combination with ground fabric mulching on soil moisture，fertility，and apple yield. [Methods] The main treatments included intercropping ryegrass（NGR），oilseed rape（NGO），and alfalfa（NGA），the sub-treatments included combining these intercropping modes with mulching ground fabric under apple trees（GR/GO/GA），and the control treatment was traditional clean tillage（CK）. Additionally，15N labeled microplots were set up within the main and control treatments. The responses of soil moisture，nutrients，and fruit yield were explored under the apple-green manure intercropping system. [Results] All treatments reduced soil water content（SWC）compared to CK，among which the decreasing range of GR（1.7%）was the smallest. Soil water difference ratio（SWDR）in the main treatments were all negative，among which NGR and NGA had the smallest（0.5%）and largest（4.7%） absolute value，respectively. All treatments increased evapotranspiration（ET）compared to CK，among which the increasing range of GR（0.3%）was the smallest. All treatments reduced soil nitrate-nitrogen（SNN）content， compared to CK. Compared to the sub-treatments，SNN and soil ammonium-nitrogen（SAN）contents in the main treatments increased by 6.8% and 5.4% on average. Intercropping green manure（NGR，NGO，and NGA） reduced 15N loss by an average of 56.4%（p<0.05），compared to CK，with alfalfa and ryegrass showing the highest （39.4%） and lowest （19.7%） 15N utilization efficiency， respectively. Compared to CK， ryegrass intercropping treatments（NGR and GR）increased SOM and TN contents by an average of 1.5% and 0.2%， respectively. In contrast，alfalfa（NGA and GA）intercropping treatments decreased SOM and TN contents by an average of 15.2% and 15.4%，compared to CK. Ryegrass intercropping treatments（NGR and GR）showed the highest fruit yield and water use efficiency，with an average increase of 12.1% in yield and 8.8% in water use efficiency，compared to CK（p<0.05）. [Conclusion] Adopting the binary mulching pattern（ground fabric mulching under apple trees+ryegrass intercropping between rows ）is beneficial to decreasing water consumption， nutrient loss，and increasing fruit yield and water use efficiency.
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MA Yunlei, HAN Lei, WANG Nana, MA Jun, WANG Yuan, MA Shijie
2025,39(2):260-268, DOI: 10.13870/j.cnki.stbcxb.2025.02.035
Abstract:
[Objective] Robinia pseudoacacia，as the main afforestation tree species in China，plays an important role in improving the ecological environment and increasing carbon storage to alleviate climate change. This paper predicts the spatial and temporal changes of the suitable area distribution and carbon storage of Robinia pseudoacacia forest under different emission scenarios in the future， and analyzes its carbon sequestration potential， so as to provide scientific basis for regional plantation development planning and sustainable management. [Methods] Based on the MaxEnt model，this study predicted the potential suitable area of Robinia pseudoacacia under future climate scenarios， and the potential geographic distribution and area of Robinia pseudoacacia were studied quantitatively in the future. By analyzing the contribution rate of comprehensive environmental factors and the importance of substitution， the influencing factors restricting the potential geographical distribution of Robinia pseudoacacia plantation were clarified. The spatial distribution of carbon storage in 2090 s Robinia pseudoacacia forest was estimated and analyzed by using the volume stand age model and the volume biomass method. [Results] 1）Temperature factor was the most critical climatic factor affecting the distribution of potential suitable areas of Robinia pseudoacacia， with a contribution rate of 64.4%， precipitation factor came second. 2）Under the current climatic conditions，the potential suitable areas of Robinia pseudoacacia were mainly distributed in the Yellow River Basin，the Huaihe River Basin and the upper reaches of the Yangtze River，and the high suitable areas were mainly distributed in the northern part of China，accounting for about 4.2% of the total land area. Under the future climate change，the concentration of Robinia pseudoacacia loss area will increase under the SSP245 and SSP370 scenarios，mainly located in the Sichuan Basin. The expansion area was mainly distributed in the surrounding area of the stable zone，showing the characteristics of distribution fragmentation. 3）In the future，the carbon storage and carbon density of Robinia pseudoacacia forest will increase under the four climate scenarios. By 2100，the carbon storage will reach the maximum under the SSP585 scenario. [Conclusion] Under the high emission scenario，the medium-high value area of carbon storage moves northwestward and is concentrated in the eastern part of Northwest China.
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MA Jun, HAN Lei, LIU Lili, WANG Nana, MA Yunlei, MA Shijie, WANG Yuan
2025,39(2):269-278, DOI: 10.13870/j.cnki.stbcxb.2025.02.025
Abstract:
[Objective] Research on the characteristics of sap flow velocity and its responses to environmental factors in plantations with different degrees of degradation is helpful to reveal the mechanisms of forest degradation，and can provide a scientific basis for structure adjustment and management of regional plantations. [Methods] Taking Robinia pseudoacacia plantations in the east area of Yellow River in Ningxia as the research objects，the stem sap flow velocities of R. pseudoacacia with different degrees of degradation were measured by TDP thermal diffusion sap flow meter from May to October，2023，and the environmental variables were monitored at the same time. The response relationships between environmental variables and the stem sap flow velocities of non-degraded R. pseudoacacia plantation（NDPP），moderately degraded R. pseudoacacia plantation（MDPP）and heavily degraded R. pseudoacacia plantation（HDPP）were studied. [Results] 1）The daily average sap flow velocity of NDPP ，MDPP and HDPP were 2.32，0.84 and 0.45 cm/h respectively. 2）With the aggravation of degradation，the response threshold of R. pseudoacacia sap flow velocity to atmospheric temperature（Ta） and saturated water pressure deficit（VPD） increased，while the response threshold to solar radiation（Sr）decreased. The critical response thresholds of sap flow velocity of R. pseudoacacia with different degradation degrees to environment variables were 29.6，30.3 and 32.7 ℃ respectively in Ta，1.14，1.93 and 2.39 kPa respectively in VPD and 428，314 and 222 W/m2 respectively in Sr. 3）The sap flow velocity of R. pseudoacacia decreased significantly with the decrease of soil water content， and the sensitivity of sap flow velocity to the change of soil water content decreased with the aggravation of degradation. 4）The contribution of environmental variables to sap flow velocity in stands with different degrees of degradation was different. With the aggravation of the degradation degree，the total effect of Sr，VPD and soil moisture on sap flow velocity decreased. [Conclusion] For degraded R. pseudoacacia forests，appropriate thinning could be used to reduce stand transpiration，improve rhizosphere soil moisture environment and increase the response sensitivity of trees to drought environment.
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DENG Tong, QIAN Haiyan, ZHOU Yangming, XIE Dongming
2025,39(2):279-288, DOI: 10.13870/j.cnki.stbcxb.2025.02.037
Abstract:
[Objective] Investigating the ecological stoichiometry of soil nutrients and the driving mechanisms in wetlands can provide key insights into soil nutrient cycling processes and the internal driving factors. [Methods] This study focused on the wetlands of Banghu（semi-controlled lake）and Sizhoutou（open-water area）in the National Nature Reserve of Jiangxi Poyang Lake. Based on correlation analysis and structural equation modeling（SEM）， the ecological stoichiometric characteristics of surface soil carbon（C），nitrogen（N），and phosphorus（P）and their key influencing factors under different elevation gradients from 2017 to 2019 were analyzed. [Results] The mean concentrations of soil organic carbon（SOC），total nitrogen（TN），and total phosphorus（TP）in the Banghu wetland（9.33，1.18 and 0.43 g/kg，respectively）were significantly higher than those in the Sizhoutou wetland（2.65，0.31 and 0.19 g/kg，respectively）（p<0.05）. At the same elevation gradient，SOC，TN，and TP concentrations in both wetlands did not vary significantly over the years（p>0.05）. Although the mean soil C∶N ratio in the Banghu wetland（9.24）was significantly lower than that in the Sizhoutou wetland（10.19），the mean C∶P and N∶P ratios in the Banghu wetland（53.18 and 6.23，respectively）were significantly higher than those in the Sizhoutou wetland（40.90 and 4.05，respectively）（p<0.05）. Elevation gradient had no significant effect on the C∶N ratio in either wetland（p>0.05）. However，C∶P and N∶P ratios exhibited an increasing – decreasing trend along the elevation gradient. At the same elevation，C∶P in the Banghu wetland showed a significant interannual variation（p<0.05），while there was no significant change observed in the Sizhoutou wetland（p> 0.05）. Both wetlands exhibited significant positive correlations of C∶P and N∶P ratios with the aboveground biomass（AGB）and electrical conductivity（EC），and significant negative correlations with pH（p<0.05）. Soil alkaline nitrogen （AN）， ammonium-nitrogen （NH4+-N）， and AGB had direct effects on soil ecological stoichiometry of both wetlands. In addition，the ecological stoichiometric characteristics in the Banghu wetland were directly influenced by soil bulk density（BD）and pH，while those in the Sizhoutou wetland were influenced by soil volumetric water content（SWC）and EC. In the Banghu wetland，AGB was the key factor influencing C∶N，while AN was the primary determinant of C∶P and N∶P. In the Sizhoutou wetland，NH4+-N was the main controlling factor for C∶N，and AGB was the critical factor affecting C∶P and N∶P. [Conclusion] Vegetation biomass and soil nitrogen play crucial roles in the ecological stoichiometric characteristics of soil carbon，nitrogen， and phosphorus in the Poyang Lake wetlands. The soil stoichiometric values in the semi-controlled Banghu wetland are primarily driven by AGB and AN，whereas those in the open-water Sizhoutou wetland are mainly influenced by NH4+-N and AGB. Therefore，technical model of vegetation restoration and reconstruction in wetlands could be considered to promote ecological restoration and protection of Poyang Lake wetland in the future.
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LIU Ruhua, MA Yali, CUI Erliang, QIAO Jiangbo, JIA Xiaoxu, ZHU Yuanjun, SHAO Mingan
2025,39(2):289-297,308, DOI: 10.13870/j.cnki.stbcxb.2025.02.012
Abstract:
[Objective] The Loess Plateau is the largest apple-producing area in China. Due to serious aging of apple trees in recent years，the single variety structure，and the instability of China's grain market，it has become a common phenomenon for orchards to be transformed into farmlands on the Loess Plateau to ensure national food security. In order to study the response characteristics of the ecological stoichiometric ratios to conversion of orchards into farmlands. [Methods] Farmlands of 0 year（30 years orchard），1 year，3 years and 5 years old was selected as the research objects in this study，with farmlands cultivated with food crops set as the control group（CK）. Soil organic carbon（SOC），total nitrogen（TN），and total phosphorus（TP）contents in the soil of 0—100 cm depth （10 cm per layer，a total of 10 layers.）were measured，and their ecological stoichiometric ratios were calculated， and the influencing factors of the ecological stoichiometric ratios were analyzed. [Results] 1）With the increase of conversion years，the mean values of SOC and TN in 0—100 cm soil after orchards returning showed a trend of decreasing first and then increasing，and were higher than that in CK，but the mean value of TP in soil showed a decreasing trend. There was no significant change in C∶N in soil，but C∶P and N∶P increased gradually，while the mean values of C∶P and N∶P in farmlands after 5 years of tillage were higher than that in CK. 2）With the increase of soil depth，SOC，TN and TP in the soil of orchards with different returning years showed a downward trend as a whole. The C∶P and N∶P generally increased first and then decreased，while C∶N showed no obvious change pattern. 3）The soil particle composition was the main factor affecting soil nutrients and ecological stoichiometric ratios in the study area. [Conclusion] These results revealed the changed pattern of C，N and P in the soil of orchards of different ages after conversion into farmlands. The results will provide an important reference for ecological environment protection and sustainable development in the loess tableland area.
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ZHANG Zhongzhi, ZHAO Junsan, CHEN Guoping, WANG Lin, LIN Yilin, ZHANG Dandan
2025,39(2):298-308, DOI: 10.13870/j.cnki.stbcxb.2025.02.024
Abstract:
[Objective] Clarifying the changes in net primary productivity（NPP）and the driving factors is of great significance to measure the carbon sequestration capacity of vegetation and support carbon sink trading. [Methods] Net primary productivity data were obtained based on MODIS-NPP data，and combining the Theil-Sen Median trend analysis，Mann-Kendall test，and the characteristics of spatiotemporal variation of NPP in Kunming from 2001 to 2020 were revealed. The optimal parameters-based geographical detectors（OPGD）model was adopted to explore the fluencing mechanisms of climate，topography and anthropogenic factors on NPP. [Results] 1）The annual mean distribution of vegetation NPP in Kunming City was spatially and temporally heterogeneous，with a distribution pattern higher in the west and lower in the east，and increased significantly at an average annual growth rate of 7.08 g/（m2·a）（C-based）. 2） The fragmentation degree of the vegetation landscape increased；the fragmentation degree was mismatched with vegetation NPP in terms of space，and it had a significant negative effect on the spatial and temporal distribution of vegetation NPP. 3）Changes in vegetation NPP were the result of the combined effects of climatic， anthropogenic and topographic factors； the kernel Normalized Difference Vegetation Index（kNDVI），land surface temperature，and vegetation landscape fragmentation had stronger explanatory power than factors such as temperature，precipitation，and slope；and the interactions between the factors better explained the spatial and temporal changes in vegetation NPP. [Conclusion] The vegetation NPP in Kunming showed an increasing trend from 2001 to 2020 in general. However，the ecological situation in certain areas of the main urban districts is not optimistic. In the future，comprehensive planning should be implemented to scientifically promote the coordinated development of ecological protection and social economy.
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SUN Jiaxing, XU Guorong, CHENG Xindong, WANG Yuyuan, WU Jiangqi
2025,39(2):309-317,347, DOI: 10.13870/j.cnki.stbcxb.2025.02.030
Abstract:
[Objective] To explore the effects of grazing on soil enzyme activities in salinized grasslands during the freezing period under the background of global warming. [Methods] Taking salinized grasslands in the Hexi Corridor as the research objects，four treatments were set up，including control（CK），grazing（FCK），warming （W），and warming + grazing（FW），in order to explore the variation law and spatial distribution characteristics of soil enzyme activities under different treatments. [Results] Compared with CK， the FCK treatment significantly increased soil water content and total nitrogen content，and decreased soil organic carbon content. The W treatment reduced soil water content and increased soil organic carbon content and total nitrogen content by 97.61% and 16.89%，respectively. The FW treatment significantly increased soil water content，organic carbon content and total nitrogen content， while total phosphorus content of the FW treatment was significantly （40.81%）lower than that of CK. The FCK treatment significantly increased the activities of β-glucosidase， amylase，urease and phosphatase；the W treatment significantly increased the activities of amylase，urease and nitrite reductase，while the FW treatment increased the activities of β -glucosidase，amylase，urease and nitrate reductase. Compared with other treatments，the stoichiometric ratios of soil enzymes in W and FW treatments were significantly increased. Through vector analysis，it was found that the study area was significantly limited by nitrogen. [Conclusion] Warming and grazing treatments directly or indirectly affect soil enzyme activities through soil physicochemical properties，of which SOC is one of the key factors affecting soil enzyme activities in salinized grasslands in Hexi Corridor.
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ZHAI Jie, YANG Shuqing, LIU Yue, CHEN Yu
2025,39(2):318-324, DOI: 10.13870/j.cnki.stbcxb.2025.02.021
Abstract:
[Objective] To investigate the effects of microbial fertilizer application under brackish water irrigation on salt ion content in saline soil and on the growth of Lycium barbarum，as well as to elucidate the relationship between soil salt ions and Lycium barbarum growth indices. [Methods] A series of field experiments were conducted on moderately saline soils in the Hetao Irrigation Area. Four different application rates of microbial fertilizer were tested under brackish water irrigation conditions：F1（45 kg/hm2），F2（75 kg/hm2），F3（105 kg/hm2），and F0（0 kg/hm2，as control）. [Results] Soil salt ion levels declined with increased microbial fertilizer application. Notably，compared to F0，the F3 treatment significantly reduced Na+ ，K+ and Cl - levels by 49.22%，40.20%，and 47.80%， respectively，throughout the reproductive period（p<0.05）. Additionally，plant height，ground diameter，canopy width，and new branch growth rate in LBP significantly increased with higher microbial fertilizer levels（p< 0.05），with the F2 treatment yielding the greatest improvements. During the flowering stage—a period highly sensitive to growth—the plant height growth rate in F2 exceeded that of F0 by 3.27%. In the spring growth period，the growth rates of plant height，canopy width，and new branches all peaked，while the growth rate of ground diameter reached its highest in the fruit expansion stage. The Lycium barbarun yield in the F2 treatment was 46.33% higher than that in F0（p<0.05），with a fertilizer partial productivity of 0.61 kg/kg. Correlation analysis indicated a negative relationship between soil Na+ ，K+ and Cl - concentrations and Lycium barbarum growth parameters. [Conclusion] In summary，to optimize soil conditions and promote Lycium barbarum growth in saline soils under brackish water irrigation in the Hetao Irrigation District，a microbial fertilizer application rate of 75~105 kg/hm2 is recommended.
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2025,39(2):325-337,377, DOI: 10.13870/j.cnki.stbcxb.2025.02.038
Abstract:
[Objective] To reveal the spatiotemporal evolution，distribution dynamics，spatial differences，and convergence characteristics of land green use efficiency in resource-based cities，in order to clarify the land use status，optimize the national spatial development pattern，and provide a reference for comprehensive green transformation of economic and social development. [Methods] Based on data from 114 resource-based cities in China from 2006 to 2020，the spatial and temporal characteristics，distribution dynamics，spatial differences，and convergence features of land green use efficiency in resource-based cities were analyzed by using the super efficiency SBM model to measure land green use efficiency，in combination with Kernel density estimation， Dagum Gini coefficient，coefficient of variation，and fixed effects model. [Results] 1）Overall，the land green use efficiency in resource-based cities showed a fluctuating upward trend，with an average annual growth rate of 1.363% during the investigation period. From a regional perspective，the land green use efficiency showed a pattern of regional differences in most years，with the eastern region>northeast region>central region>western region. From the perspective of growth stages，there was a gradient difference characteristic of regenerative type> maturity type>growing type>declining type. From the perspective of spatial distribution，the land green use efficiency of most resource-based cities was in the middle to low range，and showed obvious spatial agglomeration and non-equilibrium characteristics. 2）In terms of dynamic evolution，the core density curves of cities in the overall and various growth stages were fluctuating to the right，with a decrease in height and an increase in width of the main peak，a significant right tail，and a gradually emerging multi-peak shape，indicating an improvement in land green use efficiency. However，there was significant downward pressure，increasing inequality，and a certain degree of divergence and polarization. 3）From the perspective of spatial differences，the spatial differences in land green use efficiency within and between resource-based cities at different growth stages were on the rise. Regional differences and over-density were the two main sources of overall differences. 4）According to the convergence test，during the investigation period，the overall and different growth stages of resource-based cities' land green use efficiency did not show σ-convergence，indicating that regional differences were expanding. However，at the same time，there was a significant trend of absolute β-convergence and conditional β-convergence，that is，the growth rate of land green use efficiency tended to converge and gradually develop towards a steady state. [Conclusion] In the future，we should scientifically understand the connotation，scope，and practical value of land green use efficiency， optimize land use policies， coordinate and adapt to local conditions， in order to comprehensively improve the land green use efficiency of resource-based cities.
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GENG Haopeng, XU Ziyi, GUO Yu, ZHANG Jian
2025,39(2):338-347, DOI: 10.13870/j.cnki.stbcxb.2025.02.008
Abstract:
[Objective] To construct a comprehensive multi-temporal landslide inventory across the Eastern Himalayan Syntaxis and quantify landslide-driven erosion rates，thereby revealing the geomorphological significance of landslide processes in this region. [Methods] The Particle Swarm Optimization（PSO）algorithm was employed to detect the change of the Normalized Difference Vegetation Index（NDVI）from remote sensing images，and a multitemporal landslide inventory for the Eastern Syntaxis from 1987 to 2021 was constructed. The landslide erosion rate was calculated using an empirical landslide area-volume relationship. Additionally，the factors inducing landslide processes by considering climatic and topographic parameters were explored. [Results] A total of 1 323 landslides were identified in the study area between 1987 and 2021，with the highest occurrence of 389 landslides recorded between 2017 and 2021. The landslides predominantly occurred on both sides of the river valleys near the Yarlung Tsangpo River's Great Bend. The landslide erosion rates in the study area ranged from 0 to 76.06 mm/a，with an average rate of 0.44 mm/a. These rates showed a decreasing trend from the Great Bend section of the Yarlung Tsangpo River outward. The erosion rates were comparable to the exhumation rates of geological-scale rock bodies and the millennial-scale basin-wide average erosion rates. Landslide occurrences were associated with rainfall events and seismic activities，primarily developing on south-facing slopes and clustering within an elevation range of 1 500 to 3 000 meters and slopes of 35° to 45°. [Conclusion] Landslides represent the dominant erosion process in the Eastern Himalayan Syntaxis. Rainfall is influenced by the windward slope effect and concentrates on southfacing slopes，and drives the concentrated distribution of landslides on these slopes. Moreover，precipitation also triggers landslides by enhancing river incision，which steepens the adjacent slopes.
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ZHANG Le, LI Chunyue, GAO Chuanyu, GUO Huan, LI Yifan
2025,39(2):348-356, DOI: 10.13870/j.cnki.stbcxb.2025.02.007
Abstract:
[Objective] To explore the impact of different vegetation types on soil health in the Qinling region，to assess the relationship between aboveground plants and soil health，and construct a comprehensive soil quality health evaluation model. [Methods] Five vegetation types were selected，including poplar forest（RY），pine forest（RP），mixed forest （RM），privet forest（RL），and vineyard（CK）. Soil samples were collected from different depths（0~20 cm and 20~ 40 cm），and the analysis was conducted using the Minimum Data Set（MDS）method combined with 35 soil physical， chemical，and biological indicators，along with the contents of four heavy metals. [Results] 1）The Minimum Data Set （MDS）was established for soil fertility evaluation，eight biological and non-biological indicators were included，i.e.，field moisture capacity（FMC），physical clay content，pH，soil organic carbon（SOC），microbiological total PLFA， eukaryotic microbial PLFA，nitrogen acquisition enzyme（NAG），and microbial biomass nitrogen（MBN）. Potential Ecological Risk Index（RI）was used to assess the pollution risk of four heavy metals for soil environmental risk evaluation. Soil health was assessed by combining MDS and RI. 2）Soil fertility of RY was significantly higher than that of RP and RM. The lower SOC，NAG，FMC，and eukaryote significantly limited soil fertility，while the higher heavy metal pollution risk in CK severely restricted its soil health rating. 3）There were significant differences in soil health at different depths，indicating that the diversity of surface herbaceous plants increased soil fertility and reduced heavy metal pollution，significantly impacted soil health. [Conclusion] Reasonable reclamation measures and increased diversity of surface vegetation can significantly improve soil health. The restoration of reclamation vegetation can help improve soil fertility and reduce heavy metal pollution. It is recommended to strengthen the diversity of herbaceous plants in future reclamation processes and increase fertilization to improve soil ecosystem functions and health levels.
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JIANG Liyuan, SUN Minghui, WANG Bo, LIU Wenting, WANG Youbao
2025,39(2):357-364,377, DOI: 10.13870/j.cnki.stbcxb.2025.02.020
Abstract:
[Objective] To investigate the effect of applying Pteroceltis tatarinowii biochar on the remediation of soil with combined contamination of Cu and Pb by Chlorophytum comosum. [Methods] Taking the farmland soil with combined contamination of Cu and Pb around the copper tailings in Laoyaling，Tongling City as the research object，pot planting test method was used to grow C. comosum in the soil with different mass ratios of Pteroceltis tatarinowii biochar（1%，3%，5%，7% and 10%）. The pots without adding P. tatarinowii biochar were taken as the blank group，and the pots without planting C. comosum were set as the control group. The effects of different mass ratios of P. tatarinowii biochar on remediation of Cu- and Pb-contaminated soil by C. comosum were studied，and the potential of P. tatarinowii biochar in enhancing the remediation of Cu- and Pb-contaminated soil was evaluated. [Results] Plant height，root length and underground fresh weight of C. comosum were significantly increased by adding P. tatarinowii biochar. Soil pH， organic matter， total nitrogen， available phosphorus and available potassium were significantly increased. The mass fractions of available Cu and Pb in soil were significantly decreased，and the uptake of Cu and Pb by C. comosum was significantly increased. The maximum increases of Cu and Pb in the above-ground part are 51.39% and 59.77%，respectively，and the maximum increases of Cu and Pb in the undergroud part are 15.63% and 45.46%，respectively. The maximum enrichment and transfer coefficients were 0.61 and 0.40 for Cu and 0.37 and 0.68 for Pb，respectively. The relative abundances of Acidobacteria and Proteobacteria were decreased，while the relative abundances of Chloromycetes and Bacteroidetes were increased，and the soil nutrient metabolism was promoted. [Conclusion] Combined application of P. tatarinowii and C. comosum has better remediation effect.
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ZHANG Yujie, ZHANG Xiaoping, SUN Weinan, GENG Wenliang, AN Zefeng, CHEN Qingwei
2025,39(2):365-377, DOI: 10.13870/j.cnki.stbcxb.2025.02.026
Abstract:
[Objective] This study aimed to investigate the spatiotemporal changes and trade-offs/synergies of ecosystem services within the Beiluo River basin to provide a scientific foundation for rational resource allocation and sustainable development. [Methods] Utilizing multi-source data and models，such as InVEST and CSLE，to quantitatively assess and analyze the spatiotemporal variations and trade-offs/synergies of three key ecosystem services-water yield，soil conservation，and carbon storage-across different periods. These periods include the relatively stable land use period from 1970 to 1990，the transitional period around 2000，and the ecological restoration period from 2010 to 2020. [Results] 1）The overall water yield of the basin initially showed an increasing trend，followed by fluctuating decline，bottoming out in the 2000. During the first period，the average water yield was 10.16×108 m3（37.75 mm），which decreased by 36.9% during the second period and by 25.53% during the third period compared to the initial period. Among the three land use types of forests，cropland，and grassland，the total water yield and water yield depth of cropland are always the highest，while the water yield depth of forest was always the lowest. 2）The total soil conservation displayed an upward trend with fluctuations， peaking in the 2010. Over the first period，the average annual soil conservation was 305.62×106 t（113.57 t/ hm2），which increased to 364.52×106 t in the transition period and significantly increased to 426.19×106 t （157.75 t/hm2）during the third period. The soil conservation capacity of forests was significantly greater than that of cropland，and the construction of terraces and other engineering measures have greatly enhanced the function of cropland. 3）The total carbon storage remained stable and then continued to increase，with a notable increase from the 2000 onwards，and a 24.09% increase in the 2020 when compared with the 1970. Forests were the main carbon reservoirs，with their carbon storage significantly increasing，whereas that in grassland and cropland have decreased due to the reduction in their areas. 4）Regarding changes in the spatial pattern，the areas experiencing a decrease in water yield and an increase in soil conservation and carbon storage were mainly concentrated in the high plateau and gully areas，as well as the hilly and gully regions. 5）At the basin scale，there was a trade-off between water yield and soil conservation，as well as carbon storage. Soil conservation and carbon storage，however， exhibited a synergistic relationship. The degree of synergy between soil conservation and carbon storage decreased over time，while the trade-off between water yield and the other two remained relatively stable. [Conclusion] With the restoration of vegetation，the three key ecosystem service exhibited significant temporal and spatial variation characteristics，possessing relatively stable trade-off and synergistic relationships. The research results can provide a scientific basis for enhancing the comprehensive benefits of ecosystem services on the Loess Plateau.
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ZHU Wanjing, WANG Keqin, SONG Yali, MA Jiangang, LIU Xinyi, WANG Zhenchao, ZHAO Yangyi
2025,39(2):378-389, DOI: 10.13870/j.cnki.stbcxb.2025.02.013
Abstract:
[Objective] The investigation of temporal and spatial variations in soil erosion and its influencing factors in Yunlong County is of great significance for the advancement of featured agriculture，management and restoration of ecological environment，and soil erosion control in alpine and canyon regions. [Methods] The GIS and RUSLE model were employed to simulate the spatiotemporal evolution characteristics of soil erosion in Yunlong County from 2000 to 2020. The relationship between featured agriculture and soil erosion was analyzed. By considering influential factors such as elevation，slope，annual average rainfall，vegetation coverage，and land use type，the quantitative attribution of soil erosion was examined using a geographic probe model. [Results] 1）From 2000 to 2020，the average erosion modulus in Yunlong County exhibited a decreasing trend across five stages（each stage included five years），being 1 644，1 085，878，661 and 467 t/（km2·a），respectively，and the overall soil erosion shifted from moderate to mild intensity. 2）Over the past 20 years，there was a significant increase in proportion of the area where soil erosion had been improved，with an increase of 48.45%，while the proportion of area experiencing soil erosion deterioration only increased by 4.23%， indicating an overall trend of decline and improvement in erosion grades. 3）Soil erosion in Yunlong County was predominantly concentrated within the elevation range of 2 000~2 500 m and slopes between 15°~25° . 4）The soil and water conservation capacity of typical featured agriculture in Yunlong County followed the order of pickled walnut>Chinese herbal medicine under the forest>ecological green tea>Maidiwan pear. 5）The influencing factors for soil erosion in Yunlong County ranked as the order of vegetation coverage > altitude > slope > annual average rainfall>land use type， with the corresponding q values being 0.401 0，0.142 0，0.117 5，0.115 9 and 0.046 6，respectively. Notably，the interaction between vegetation coverage and slope exhibited the strongest explanatory power with a q value of 0.82. [Conclusion] Overall soil erosion in Yunlong County has shown effective improvement over a span of two decades. During this period，there had been a weakening trend in soil erosion accompanied by an increase in vegetation coverage. Future attention should be directed towards monitoring changes in soil erosion within altitudes ranging from 2 000~2 500 m and slopes between 15° ~25° in Yunlong County while ensuring proper implementation of measures to develop featured agriculture and restore the microtopography on slopes to mitigate risks associated with further deterioration of soil erosion.
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MA Liguo, LIU Jianwei, PANG Xiaoteng, JING Haihua
2025,39(2):390-400, DOI: 10.13870/j.cnki.stbcxb.2025.02.006
Abstract:
[Objective] To reveal the characteristics of the response of runoff to land use and climate change in the Tao'er River basin，and to predict the future evolution of runoff in the basin. [Methods] Taking the Tao'er River basin as the study area，the runoff response process of the watershed was quantitatively analyzed based on the SWAT model with the CMIP6 climate model and PLUS model driving meteorological and land use changes， respectively，to project development scenarios for 2025—2100. [Results] 1）The SWAT model had an R2>0.75 and an NSE>0.65 for both the rate period and the validation period. The overall accuracy of the PLUS model was > 0.85，and the Kappa coefficient was > 0.80，and the two models had good applicability in this watershed. 2）Relative to the baseline period（1990—2022），the Tao'er River Basin received higher precipitation under all three future scenarios than during the historical period，as shown by SSP126 > SSP585 > SSP245，and higher temperatures under all three future scenarios than during the historical period，as shown by SSP585 > SSP245 > SSP126. 3）During the period of 2025—2100，the areas of cropland，watersheds，and unutilized land in the Tao'er River Basin increased significantly，while the area of forested land increased slowly，and the areas of grasslands and built-up lands continued to decrease. 4）The average annual runoff in the future period would exceed the level of the base period under the SSP126 scenario，while it would be lower than the level of the base period under the SSP245 and SSP585 scenarios，and the average multi-year runoff under the three scenarios would be 11.17×108，9.00×108 and 9.34×108 m3/s. [Conclusion] The Tao'er River basin's future runoff change presents the trend of continuous growth，therefore should enhance the flood control consciousness when the annual average runoff reaches the maximum value in three level years，the results can provide certain reference basis for reasonable development and construction of the Tao'er River basin in the future.
Volume 39, 2025 Issue 2
综述评论
基础研究
技术方法
数据科学
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Investigating Trade-offs, Synergies, and Attributions of Ecosystem Services in the Yarlung Zangbo River Basin
Abstract:
[Objective] The ecological environment of the Yarlung Zangbo River Basin is fragile. Revealing the spatiotemporal changes in the ecological service functions of the river basin and the trade-off and synergy of dominant functions can provide scientific and technological support for the ecological protection and restoration of the river basin. [Methods] Five critical ecosystem services (habitat quality, water production, soil conservation, carbon sequestration and food supply) were quantitatively assessed within Yarlung Zangbo River Basin using InVEST model. To analyze the spatiotemporal dynamics of ecosystem service functions across various altitudinal gradients and scales, and uncovers the tradeoffs and synergies among these services, Spearman non-parameter correlation analysis and geographical weighted analysis were employed. [Results] (1) From 2000 to 2020, the high values of five ecosystem services supply primarily concentrated in the lower reaches. The Yarlung Zangbo River Basin exhibited higher habitat q
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Health assessment of forest ecosystem in mountainous area of Beijing
Abstract:
[Objective] To reveal the spatial and temporal evolution characteristics of the health status of forest ecosystems in the mountainous areas of Beijing from 2005 to 2020, and to analyze the regional differences and the explanatory power of the influencing factors.[Methods] We constructed a forest ecosystem health evaluation model with “geographic environment-vegetation structure-ecological pressure-vegetation function” as the criterion layer, and applied the entropy weight-TOPSIS method to calculate the weights of the indicators and evaluate the forest ecosystem health of the mountainous regions of Beijing year by year, and analyze the characteristics of the changes in the forest ecosystem health in 2005, 2010, 2015, 2020, and the changes in the forest ecosystem health of the mountainous regions of Beijing. We analyzed the changes of forest ecosystem health in 2005, 2010, 2015 and 2020.On this basis, spatial autocorrelation analysis and K-means clustering analysis were used to explore the spatial aggregation and regional differences in ecosystem health, and the explanatory power of each indicator factor on the spatial distribution of forest ecosystem health was quantified by using the single-factor detection and interaction detection modules in Geographical detector model.[Results]:(1) From 2005 to 2020, the health level of forest ecosystems in the mountainous areas of Beijing will show an upward trend year by year.At this stage, the forest ecosystems in the mountainous areas of Beijing are mainly moderately healthy and relatively healthy, with the proportion of the area in the two areas being 41% and 48%, respectively.The spatial pattern of spatial differentiation is high in the far urban areas and low in the near urban areas. (2) The health status of forest ecosystems in the Beijing mountainous area has been improving year by year, and the change was especially obvious from 2015 to 2020, with the proportion of excellent healthy areas rising from 2.43% to 18.65%.The Moran index in the study area showed a decreasing and then increasing trend from 2005 to 2020, exhibiting significant global spatial autocorrelation and local spatial autocorrelation clustering characteristics.The spatial types of significance were dominated by positive correlation, with 41.8% and 30.8% of HH and LL types, respectively, accounting for 79.6% of the total number of significance types. (3) Soil conservation, LAI, NDVI, tree cover, and population density were the dominant factors of forest ecosystem health in the mountainous areas of Beijing, and the interactions among the factors showed nonlinear enhancement and two-factor enhancement;Forest ecosystem health in Beijing"s mountainous areas was dominated by GDP and soil retention in 2005, by LAI and soil retention in 2010-2015, and by air purification and soil retention in 2020.[Conclusions] From 2005 to 2020, the health of forest ecosystems in the mountainous areas of Beijing has continued to improve, but 27.27% of the area is still in poor or moderate ecological health, with some room for improvement. The spatial distribution of areas with poor health and low-low catchment areas is basically the same, and the construction of ecological protection and restoration projects in forest belts should be strengthened in order to safeguard the ecological health of regional forests.In future forest management and care, the enhancement and maintenance of forest ecosystem services need to be fully considered.
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Effects of scutellaria-residue organic fertilizer on soil bacterial diversity and function in potato fields with continuous cropping on sandy land.
Abstract:
[Objective]Exploring the effects of scutellaria-residue organic fertilizer on the basic characteristics and microbial community diversity and function of continuous potato soil can provide theoretical references for the resource utilization of Scutellaria-residue and the soil improvement of continuous cropping potato fields. [Methods] Three kinds of organic fertilizer systems were constructed with the bulk medicinal herb Scutellaria-residue and sheep manure (mass ratio 1:4) as the base material, which were 3% of bacterial additive (F1), 5% of bacterial additive (F2), and 10% of bacterial additive (F3). The effects of three Scutellaria-residue organic fertilizer systems on the chemical properties, soil bacterial diversity and community structure of potato surface soils in continuous cropping were analyzed in conjunction with a controlled field trial.[Results](1)Compared with the control group,all three scutellaria-residue organic fertilizer systems significantly increased the available phosphorus and available potassium contents of the soil at the maturity stage by 8.12~12.00 mg.kg-1 and 65.63~88.36 mg.kg-1, respectively;(2) and the total number of bacterial flora in the potato topsoil was increased by 60.96% in both F1 and F2 treatments, 23.19%, and enriched with beneficial genera such as Sphingomonas, Pseudoxanthomonas and Flavobacterium; (3)LEfSe analysis showed that the application of scutellaria-residue organic fertilizers suppressed the absolute abundance of pathogenic bacteria such as Pectobacterium in the soil, and enriched more beneficial bacterial communities with soil carbon and nitrogen cycling functions at significantly higher absolute abundances;(4) the three kinds of scutellaria-residue organic fertilizer systems were able to change the function of the soil bacterial mediated carbon and nitrogen cycle, and increase the soil bacterial flora on the organic matter decomposition potential of soil flora.[Conclusion] The application of scutellaria-residue organic fertilizer can improve the soil available phosphorus and potassium nutrient content, the abundance of beneficial bacterial genera and bacterial functional activity.
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Radar Detection Analysis of the Effect of Land Preparation Measures on Soil Moisture in Hilly Sloping Farmland in Guangxi
Abstract:
[ Objective ] Soil preparation is a key measure in agricultural production in hilly and mountainous areas. It is of great significance to clarify the response relationship between the change of soil properties after soil preparation and the spatial variation characteristics of soil moisture in the field for improving the efficiency of agricultural production.[ Method ] Two typical land preparation measures of horizontal and reverse slopes in hilly and mountainous areas of Guangxi were taken as the research objects. The field radar detection experiment was combined with the indoor soil analysis experiment, and the effects of land preparation measures on the variation characteristics of soil moisture in sloping farmland were discussed in depth by means of image analysis and statistical analysis. [ Result ] Under the same external water supply conditions, the spatial variation of soil moisture after horizontal soil preparation significantly occurred in the range of 0-30 cm soil depth. The reverse slope preparation was concentrated in the range of 20-40 cm soil depth, and the slope farmland ran through the whole range of 0-50 cm soil depth. The spatial distribution of soil moisture in the field of horizontal soil preparation was the strongest ( average deviation degree was 0.0519 ), and the change degree of soil preparation on the reverse slope was the weakest. The spatial movement of soil moisture in the field of horizontal land preparation was stable ( reflection coefficient 0.33, instantaneous power change rate 8.41×1011 dB/ns ) and relatively uniform ( radar structure similarity index 0.78 ), while the degree of soil moisture movement in the field of reverse slope land preparation and slope farmland was relatively intense, and the spatial movement state changed greatly. The spatial variation of soil moisture in slope farmland was the largest ( comprehensive index 1.45 ), followed by reverse slope preparation ( comprehensive index 1.53 ), and the spatial variation of soil moisture in horizontal preparation was the smallest ( comprehensive index 1.57 ), and the soil moisture environment was relatively stable. Compared with slope farmland, the soil silt content after soil preparation has the greatest influence on the spatial variation of soil moisture. [ Conclusion ] Under the same external water supply environment, the soil moisture condition in the field after horizontal and reverse slope land preparation is better than that in the slope farmland, and the soil moisture storage condition in the field after horizontal underground preparation is relatively better.
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Progress in the study of the effect of mycorrhiza on soil respiration
Abstract:
As a bridge between plants and soil, mycorrhizal play a crucial role in regulating the balance of soil carbon (C) pools. Mycorrhizae, by absorbing mineral nutrients from the soil in exchange for C fixed by plant photosynthesis, also contribute to soil C loss through respiration.S The role of mycorrhizal in soil carbon input, carbon stability, and carbon sequestration is well understood; however, knowledge of the effects of mycorrhizal on soil respiration is relatively limited. A review of the effects of mycorrhizal on soil respiration and their regulatory factors is presented. Using the mesh exclusion method, researchers have successfully isolated and quantified mycorrhizal respiration, and found that it accounted for an average of 16.8% of soil respiration. Specifically, arbuscular mycorrhizal respiration and ectomycorrhizal respiration contribute 18.4% (2.5%-32.0%) and 15.1% (3.0%-62.1%) to soil respiration, respectively. Inoculated mycorrhizal plants increased soil respiration by an average of 26.0% compared to mycorrhizal-free plants. The response of mycorrhizal respiration to soil temperature and soil moisture varied in different ecosystems, with mycorrhizal respiration appearing to be more sensitive to changes in soil moisture. Soil nutrient availability regulates the symbiotic relationship between mycorrhizal fungi and plants by affecting the nutrient acquisition strategies of plants, and then regulates mycorrhizal respiration. Biological factors such as fine root biomass, extraradical hyphal length density, and plant-supplied substrates also significantly influence mycorrhizal respiration. As an important component of both soil respiration and autotrophic respiration, mycorrhizal respiration contributes substantially to soil C loss, which cannot be overlooked. More precise methods are needed to isolate and quantify mycorrhizal respiration to accurately assess the dynamics of soil carbon cycling and provide scientific insights for global C management and climate change mitigation.
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Microtopographic Changes of Slopes under Different Planting Patterns and The Responses to Rill Development in the Alpine Canyon Areas of Western Sichuan
Abstract:
Rill erosion constitutes a significant mode of erosion in slope farmlands. To elucidate the impact of diverse planting patterns on the morphological characteristics of rills, this study aims to identify appropriate planting strategies for specific regions.In order to investigate the characteristics of rill erosion on slopeSfarmland with various planting patterns in alpine canyon areas, this study selected several primary planting configurations as research subjects: Zanthoxylum +Plum+Candian fleabane, Zanthoxylum+Cherry +Artemisia indica,SZanthoxylum+SGreenSbean,SPlum+Soybean,San dSthe bare slope was used as a control. The erosion evolution and morphological parameters of hillslope rills underSdifferentSscour dischargeSratesS(6,S10SandS14SL.min-1,Srespe ctively) were analyzed utilizing in situ runoff plot scour tests combined with the Structure from Motion (SfM) technique. STheSresultSshowedSthat (1) Under conditions of rill erosion, the eroded area of the slope and the proportion of grid in the southern slope direction for various planting patterns are smaller than those observed on bare slopes. Under conditions of small to medium flow, the surface roughness exhibited a decreasing trend. Additionally, the proportion of grids within the range of 15° to 25° has increased, while the proportion of grids in the range of 60° to 90° has decreased. (2) Compared to the bare slope, the confluence morphology exhibited by various planting patterns is dendritic in nature and displays distinct fractal characteristics. With the exception of the 10 L.min-1 flow rate, the slope fractal dimension D for the Zanthoxylum+Plum+Candian fleabane exhibited the highest value. It has a good sand reduction effect. The rill density across all planting patterns surpassed that of the bare slope, while the ratio of rill width to depth was lower than that observed in the bare slope, except for the combinations of Zanthoxylum+SGreenSbean and Plum+SoybeanSunder a scour flow rate of 10 L.min-1. Rill morphology is characterized as“broad and shallow.” (3) In comparison to micro-aspect and micro-slope, the surface roughness associated with different planting patterns exhibited a stronger correlation with rill morphology (P < 0.01). Stepwise regression analysis indicated that surface roughness is the primary factor influencing the width-to-depth ratio of rills, as well as the density and fractal dimension of various planting patterns. The findings of this research can offer a theoretical foundation for the rational allocation of soil and water conservation measures, as well as for the effective prevention and control of soil and water loss in sloping farmland located in alpine canyon regions.
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Spatial Network and Zoning Governance of Carbon Ecological Compensation in Anhui Province Oriented Towards SDGs
Abstract:
[Objective] Under the dual-carbon goals and sustainable development framework, the development of regional carbon eco-compensation mechanisms plays a pivotal role in reconciling the conflict between economic growth and ecological preservation during land development. [Method] Focusing on Anhui Province, this study establishes an integrated “spatiotemporal differentiation-network connectivity-compensation zoning” framework. Through combined application of network analysis, carbon eco-compensation modeling, entropy weight-TOPSIS method, and K-means algorithm, a differentiated carbon compensation scheme based on Sustainable Development Goals (SDGs) was established. [Result] 1) Significant spatial heterogeneity in net land-use carbon emissions, exhibiting distinct north-south and east-west gradients with higher emissions concentrated in northern and eastern regions during the study period. 2) Emergence of a hierarchical carbon network structure with Hefei as the core node and Wuhu, Ma’anshan, and Huainan as intermediary hubs, demonstrating enhanced network connectivity and core-periphery configuration over time. 3) The spatial difference of carbon compensation value is obvious, the total carbon payment and carbon compensation amount are 109.89×108 yuan and 25.23×108 yuan respectively, and 7 payment zones and 10 compensation zones are identified. 4) Combined with the sustainable development of the city, 7 types of carbon integrated ecological compensation management zones are formed, and the differentiated carbon ecological compensation suggestions of "gradient compensation - collaborative governance" are proposed for each type of area. [Conclusion] The analytical framework and policy recommendations offer critical references for optimizing cross-regional ecological compensation mechanisms and advancing low-carbon spatial governance paradigms. Particularly noteworthy is the novel integration of complex network theory with multidimensional zoning methodology, providing a replicable model for regional carbon management in developing economies.
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Comparative analysis of the differences, enhancement effects, and implications of aggregates in saline-alkali soil versus non-saline-alkali soil
Abstract:
[Objective] Aggregates serve as crucial indicators of soil fertility, and their stability directly influences the physical, chemical, and biological characteristics of the soil. Under salinization and alkalization conditions, aggregates are impacted by the high salinity and strong alkalinity of the soil, which readily give rise to soil structure degradation and functional deterioration, severely constraining agricultural production. [Methods] This article aims to summarize the disparities in aggregates between saline - alkali soil and non - saline - alkali soil, analyze the factors influencing the formation and stability of aggregates under salinization and alkalization circumstances, and explore the methods and strategies for enhancing the aggregate structure in saline - alkali soil, as well as how research on non - saline - alkali soil aggregates can enlighten that of saline - alkali soil. [Results] Comprehensive analysis indicates that the saline - alkali environment undermines the soil structure, reduces microbial diversity and activity, resulting in a decrease in the quantity of large aggregates, an increase in the proportion of micro - aggregates, and poor stability of aggregates. In non - saline - alkali soil, both the number of large aggregates and micro - aggregates are relatively high, with a distinct distribution hierarchy, rich biodiversity, and high stability of aggregates, mainly attributed to the abundant organic matter content and vigorous microbial activities. [Conclusion] To improve the aggregate structure of saline - alkali soil, it is necessary to comprehensively employ hydraulic, physical, chemical, and biological measures to lower the soil salinity and alkalinity content, regulate the pH value, ameliorate the soil structure, enhance the water retention capacity, and increase the nutrient availability. Future research should focus on developing new technical approaches for assessing the aggregate structure, optimizing the improvement techniques, integrating multi - scale data, etc., to facilitate the gradual improvement of the characteristics of saline - alkali soil and the sustainable development of agriculture.
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Study on the spatial variation of soil organic carbon and its control factors in a typical karst county
Abstract:
[Objective] The karst and non-karst areas in Southwest China are interlaced with strong spatial heterogeneity. Assessing the spatial differentiation and storage of soil organic carbon (SOC) in this region at the county scale is of great significance for achieving regional "dual carbon" goals. [Methods] Taking Wenshan County, a typical karst county in southeast Yunnan Province, as an example, we employed a grid sampling method to conduct the spatial differences in SOC content and storage in top soil(0-20 cm) and deep soil(0-200 cm). Furthermore, we used the semi-variogram function and geographical detector to analyze the impact of external environmental factors on the spatial differentiation of SOC. [Results] The average SOC content in the top soil and deep soil was 17.80 g/kg and 5.18 g/kg respectively, with a total storage of 3770.89×104 t. The distribution pattern revealed higher SOC content in the topsoil of the western region and lower in the central and northern regions, while the deep soil exhibits higher SOC content in the central and western regions and lower in the northeastern region in Wenshan County. In non-karst areas, the SOC content in the topsoil and deep soil was 20.88 g/kg and 6.12 g/kg, respectively, which was 27.94% and 32.75% higher (P<0.01) than in karst areas. The semi-variogram model indicates that the nugget effect value of SOC ranges from 14.62% to 59.93%, indicating that structural factors dominate the spatial differentiation of SOC in Wenshan County. According to the analysis of the geographical detector, temperature and altitude are the main controlling factors affecting SOC in the top soil layer in karst areas. As the temperature decreases and the altitude increases, the SOC content in Wenshan County shows an increasing trend. However, the SOC content in karst areas is generally lower than that in non-karst areas due to their lower altitudes, severe rocky desertification, and relatively poor vegetation growth. For the deep soil, precipitation is the main controlling factor affecting SOC in karst areas. The leaching effect caused by precipitation may combine dissolved calcium with organic matter to form humic acid calcium, promoting the accumulation of SOC in deep soil. In non-karst areas, stratigraphic chronology plays a leading role. The soil developed from Permian basalt parent material may have higher soil clay and macro-aggregate contents, which helps to maintain the physical protection and stability of SOC in deep soil. [Conclusion] This study will provide a reference for the precise assessment of SOC and the regulation of soil carbon pools in the southwestern karst region.
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Soil-microbe-exoenzyme C:N:P Stoichiometric Characteristics in Artificial Pure Forests of Four Tree Species in the Hilly Region of Central Hunan
Abstract:
Abstract: [Objective] The contents of soil carbon (C), nitrogen (N) and phosphorus (P) along with their stoichiometric ratios, were changed due to the varying nutrient uptake and utilization strategies among various tree species plantations, which in turn affected soil microbial activity. However, whether soil microorganisms adapt to these changes by adjusting their biomass and extracellular enzyme stoichiometric ratios remains uncertain. This study aims to explore the effects of various tree species plantation on soil-microbe-exoenzyme C:N:P stoichiometric ratios and to investigate the correlations among soil-microbe-exoenzyme stoichiometry. [Methods] we conducted an investigation into the contents of C, N and P, as well as microbial biomass C (Cmic), N (Nmic), P (Pmic), and the activities of C (β-1,4-glucosidase + β-D-cellosidase, BG + CBH), N (N-acetyl-β-glucosaminidase, NAG), and P (acid phosphatase, ACP) acquiring extracellular enzymes for microorganisms at depths 0-40 cm in four native tree species plantations. These plantations include conifers Pinus massoniana, deciduous broad-leaved Liquidambar formosana, evergreen broad-leaved Schima superba, and Elaeocarpus decipiens, located in the hilly region of central Hunan province and share a common soil development and management history. [Results] (1) Different tree species plantations significantly affected soil C, N, P content, microbial biomass, extracellular enzyme activity, Cmic:Nmic:Pmic and EEAC:N:P. Cmic:Pmic ratios in the P. massoniana plantations and the L. formosana plantations were significantly higher than those in the S. superba plantations and the E. decipiens plantations, indicating that microorganisms compete with plants for soil available P and a low utilization rate of soil P, especially evident in the L. formosana plantation. NAG and EEAN:P in the S. superba plantations were the highest, suggesting that the microorganism was obviously limited by N. ACP in the E. decipiens forest was higher, EEAC:N and EEAC:P were also higher than those in other tree species plantations, while EEAN:P was the lowest, indicating that the microorganisms were most restricted by C and P. (2) There were no significant correlation between soil C:N:P and microbial biomass, extracellular enzyme C:N:P, while only Cmic:Nmic and EEAC:N, Cmic:Pmic and EEAC:P showed significant negative correlation, indicating no covariance between soil C:N:P and microbial biomass C:N:P. There was a significant positive correlation between soil C:N:P and C:Pimb, a significantly negatively correlation between Cmic:Nmic:Pmic and C:N:Pimb, and a significant positive correlation between C:Nimb and EEAC:N, which confirmed the influence of C, N and P differences between soil and microorganisms on the stoichiometric ratio of extracellular enzymes. (3) Existing biomass of litter layer had significant effects on soil C, N, P content, Pmic, Cmic:Pmic, Nmic:Pmic, BG+CBH, NAG, and EEAC:P. [Conclusion] By influencing the contents of soil C, N and P, plantations composed of different tree species modulated microbial biomass and extracellular enzyme activity. Microorganisms can adapt to diverse nutrient limitations by regulating their biomass C:N:P ratios and synthesizing specific extracellular enzymes, thereby substantiating the microbial resource allocation theory.
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Effects of Different Logging Residue Treatments on Acid Hydrolyzed Soil Organic Carbon Fractions and Soil Microbial Communities in a Chinese Fir Plantation
Abstract:
[Objective] Acid hydrolyzed soil organic carbon fractions are important in soil, and their changes of contents will affect soil microbial community composition.To study the response of acid hydrolyzed soil organic carbon fractions and soil microbial communities to different logging residue treatments. [Methods] Three treatments of residue removed (R), residue burnt (RB) and residue retained (RR) were applied to a Chinese fir plantation in the Castanopsis kawakamii Nature Reserve in Sanming Fujian, and soils in different soil layers (0-10 cm, 10-20 cm) were collected three years after planting young Chinese fir to study acid hydrolyzed soil organic carbon fractions (labile fraction Ⅰ, Ⅱ and recalcitrant fraction) and microbial community. [Results] (1) Different logging residue treatments had no significant effect on acid hydrolyzed soil organic carbon fractions in the 0-10 cm soil layer (p>0.05). In the soil layer of 10-20 cm, the content of labile fraction Ⅰ (LP Ⅰ) was significantly higher in the RR (7.2 g·kg-1) and R (6.8 g·kg-1) treatments than in the RB (4.7 g·kg-1) treatment, and the contents of labile fraction II ( LP II, 1.06 g·kg-1) and recalcitrant fraction (RP, 3.59 g·kg-1) in the RB treatment were significantly lower than those in the R treatment (1.32 g·kg-1 and 7.79 g·kg-1, respectively) (p<0.05). The contents of acid hydrolyzed soil organic carbon fractions in the 0-10 cm soil layer of the RB treatment were all significantly higher than those in the 10-20 cm soil layer (p<0.05). (2) The microbial biomass carbon content of the RB treatment in the 0-10 cm soil layer (335.1 mg·g-1) was significantly lower than that of the RR (540 mg·g-1) and R (453.7 mg·g-1) treatments(p<0.05), but there was no significant difference in soil microbial biomass nitrogen in each soil layer between the different treatments (p>0.05). Soil microbial biomass phosphorus content and total PLFAs in two soil layers were significantly higher in RR treatment than in RB treatment (p<0.05). In the 0-10 cm soil layer, the F:B ratio was significantly higher in RB treatment than in RR and R treatments, while GP:GN ratio was significantly higher in RR treatment than in RB and R treatments (p<0.05). (3) There were significant positive correlations between acid hydrolyzed soil organic carbon fractions and total microbial biomass and PLFAs content of each microbial taxon (p<0.05). [Conclusion] Retention of logging residue treatments facilitated the maintenance of different soil organic carbon fractions at high levels and had a positive effect on soil microbial biomass and soil microbial community composition. This study is of great significance for taking reasonable management measures of Chinese fir plantations and improving soil productivity.
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Response Characteristics of Soil Saturated Hydraulic Conductivity after returning orchard to farmland in Loess Plateau
Abstract:
[Objective] As the largest apple producing area in China, the Loess Plateau has faced the problems of aging apple trees and simplification of varieties in recent years. In addition, in order to ensure national food security, many orchards in the Loess Plateau have been converted into farmland. In order to explore the change rule and influencing factors of soil saturated hydraulic conductivity ( Ks ) after returning orchard to farmland. [Methods] In this study, mature apple orchards ( AO ) and orchards with different tillage years ( 2a, 4a, 6a, 10a ) in the Loess Plateau were selected as the research objects, and the original farmland ( CK ) was used as the control. The Ks and soil basic properties of 0-200 cm in different plots were measured. Pearson correlation analysis and structural equation model were used to analyze the response characteristics and influencing factors of Ks after returning orchard to farmland in the Loess Plateau. [Results] With the increase of returning years, the average soil water content, clay and silt content in 0-200 cm of farmland showed a decreasing trend. The average sand content showed an increasing trend. The order of Ks mean values in different plots is 2.25±1.19 cm/h(6a)＞1.60±0.71 cm/h(AO)＞1.49±0.29 cm/h(4a)＞1.46±0.44 cm/h(2a)＞1.40±0.40 cm/h(CK)＞1.04±0.61 cm/h(10a). On the whole, with the increase of returning years, the average value of Ks increased first and then decreased. With the increase of soil depth, Ks in different plots showed a decreasing trend. The direct influencing factors of Ks were soil bulk density and organic matter content, and the indirect influencing factors were tillage years and soil depth. [Conclusion] The research results can provide theoretical support for the response law of soil water movement to land use change in loess tableland area, and provide scientific basis for promoting the prevention and control of soil erosion and the rational use of land in this area.
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Influence Mechanism of Carbon transport and sequestration with carbon source addition in purple soil slope farmland under Natural Rainfall
Abstract:
[Objective]Degradation of purple soil is critical, water loss is serious, and it is difficult to increase and sequester carbon in the soil. In order to explore the impact of carbon source addition on the carbon sequestration of purple soil farmland。[Methods]Purple soil slope cropland in Sichuan Province was selected as the study. Six treatments were set up on 10° purple soil slopes: no fertilization (CK), fertilizer + straw returning (T1), fertilizer + straw biochar (T2), fertilizer + cow dung (T3), fertilizer + organic soil matrix (T4), fertilizer + biochar cow dung and mushroom slag compost (T5), each treatment was repeated 3 times. Analyze the change characteristics of runoff, sediment and carbon content under rainfall and different carbon sources.[Results]The results showed that (1) rainfall over 30 mm and short-term heavy rainfall (16.1 mm·h-1) could lead to surface runoff. The addition of carbon sources notably decreased surface runoff. In comparison with the CK , the flow reduction benefits of T2, T3, and T5 reached 38.64%, 38.61%, and 62.95%, respectively. The sediment erosion in different treatments was observed to follow the order: T1>T4>CK>T2>T3>T5, with the highest reduction of 58.99% compared to the CK . (2) The loss of organic carbon through surface runoff was primarily attributed to sediment organic carbon, which accounted for 67.47~90.43% of the total organic carbon loss. Treatments T2, T3, and T5 were effective in reducing the migration of organic carbon, resulting in a total organic carbon loss reduction of 21.74%, 19.40%, and 49.28%, respectively, compared to the CK treatment. Furthermore, the carbon fractions of T5 treatment, including dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), dissolved total carbon (DTC), and sediment organic carbon, exhibited a reduction in migration fluxes by 70.88%, 70.92%, 37.52%, and 60.07%, respectively, compared to the CK treatment. (3) PLS-PM showed that the C sequestration of soil organic carbon was influenced to varying degrees by rainfall characteristics, soil physicochemical properties, and the addition of different carbon sources.[Conclusion]Carbon sources (T2, T3, T5) reduces the total amount of organic carbon loss. T5 processing organic carbon sequestration stock increases, T2 and T3 reduce the loss of each carbon component of surface runoff, while its organic carbon sequestration stock decreases. It shows that the addition of carbon source can increase the carbon content and reduce the carbon migration, but that the solid stock is reduced, which needs to be verified by long-term experiments. This study holds significant importance in enhancing the fertility of purple soil, maintaining soil carbon balance, and reducing soil carbon loss.
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A new method to estimate the cover management factor on the Loess Plateau in China: A case study using millet field.
Abstract:
[Objective]The●present●study●attempted●to●investigate●the●combined●effect●of●crop●cover●and●crop●management●practices●on●preventing●soil●loss●and●improving●the●accuracy●of●C-factor estimation.[Methods]●Six●millet●plots●with●different●treatments,（i.e.,●crop●plot●(C1),●crop-roughness●plot●(C2),●crop-crust●plot●(C3),●bare●plot●(B1),●roughness●plot●(B2),●crust●plot(B3))●were●established●and●the●soil●loss●at●four●growth●stage●was●determined●by●simulated●rainfall.●The●C●factor●was●calculated●using●soil●loss●ratio●(SLR).●The●major●factors●affecting●SLR●were●also●analyzed●and●their●correlations●with●SLR●were●then●regressed●through●numerical●simulation●using●MATLAB.●Subsequently●the●SLR●estimation●models●designed●for●soil●erosion●prediction●on●the●Loess●Plateau●could●be●built.●Finally,●the●C●factor●could●be●calculated●using●the●proposed●SLR●estimation●model●combined●with●the●distribution●curve●of●rainfall●erosivity.[Results]●Surface●roughness●and●soil●crust●can●reduce●soil●loss●in●crop●plot.●Compared●with●,●the●mean●decreasing●of●●and●●was●21%,●16.5%,●respectively.●The●model●formulas●of●crop●plot,●crop-roughness●plot,●crop-crust●plot●were●obtained,●through●validating●by●field●soil●and●water●loss●data●conducted●at●Chunhua●county,●the●model●formulas●can●achieve●accurate●prediction,●the●estimated●C●values●for●the●whole●growth●stage●were●0.30,●0.25,●0.25,●respectively,●with●the●Nash●coefficients●were●0.96,●0.87,●0.75,●respectively.[Conclusion]●These●results●could●provide●some●insights●for●estimating●C●values●at●national●scales.
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The Applicability Evaluation of Multisource Precipitation Data for Runoff Simulation in a Typical Basin on the Tianshan Mountains
Abstract:
[Objective] In order to explore the difference of precipitation characteristics for multisource precipitation products and their applicability for runoff simulation in an alpine basin on the Tianshan Mountains. [Methods] A comparative analysis of the spatiotemporal characteristics of precipitation is conducted in the upper reaches of the Manas River Basin, based on the datasets CN05.1, GPM, AIMERG, CMFD, and ERA5. Subsequently the accuracy of different products is evaluated based on observed precipitation, and their applicability for runoff simulation is assessed by means of HBV hydrological model. [Results] The spatial pattern for all the precipitation products is characterized by the increase and then decrease from the north to south, whereas only AIMERG and CMFD are able to display higher precipitation in the glacier area. Consistent seasonal variation are detected, but large difference in summer precipitation are shown. At summer, ERA5 is twice as much as CN05.1, and GPM is lower than the other precipitation products. GPM underestimates the monthly precipitation, especially in winter and spring (64%～76%). While the monthly precipitation is overestimated by CMFD, ERA5 and AIMERG. The overestimation of ERA5 is the most serious, especially in summer and autumn (134%～206%), and CMFD slightly overestimates the monthly precipitation. AIMERG has the higher correlation with the observed monthly precipitation and greater critical success index in both rainy season and the non- rainy season. AIMERG, CMFD and CN05.1 have the greatest ability to reproduce daily runoff, with the higher NSE (0.81～0.82) and lower relative error (＜6%). Moreover, the former two products show higher performance in reproducing extreme runoff when compared with CN05.1.[Conclusion] AIMERG and CMFD show great potential in runoff simulation of the upper Manas River. The results can serve as data references for runoff simulation and soil erosion prevention research in the Tianshan region, where meteorological data is limited.
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Transpiration characteristics of common trees and their response to meteorological factors in Karst slope secondary forest
Abstract:
[Objective] To explore the transpiration characteristics of common trees and their response to meteorological factors in karst slope secondary forest. [Methods] Heat diffusion probe method (TDP) was used to monitor Broussonetia papyrifera, Koelreuteria paniculata, Triadica sebifera, Ailanthus altissima, Melia azedarach, Toona sinensis, and Rhus chinensis in Puding Karst Ecosystem Observation and Research Station of Chinese Academy of Sciences, and to study the relationship between tree transpiration characteristics and meteorological factors. [Results] (1) The average daily transpiration of Broussonetia papyrifera, Koelreuteria paniculata, Triadica sebifera, Ailanthus altissima, Melia azedarach, Toona sinensis, and Rhus chinensis were: (4 409.97±3 260.63) g/d, (6 611.27±5 629.57) g/d (3 956.32±2498.50) g/d (2984.98±2039.09) g/d (6 300.25±4 637.71) g/d, (780.69±738.80) g/d, (2320.73)±1717.18) g/d.(2) The fluid flow rates of Broussonetia papyrifera, Koelreuteria paniculata, Triadica sebifera, Ailanthus altissima, Melia azedarach, Toona sinensis, and Rhus chinensis were the highest in sunny days, followed by cloudy days, and the lowest in rainy days. (3) The influence of atmospheric temperature (T) and saturation water vapor pressure difference (VPD) on Broussonetia papyrifera, Koelreuteria paniculata, Triadica sebifera, Ailanthus altissima, Melia azedarach, Toona sinensis, and Rhus chinensis under sunny weather was the greatest, followed by relative humidity (RH) and total irradiance (Eg). [Conclusion] The transpiration of common trees in secondary forest of karst slope is limited by special water environment. Different deciduous trees have different water use strategies, and the liquid flow rate is mainly affected by VPD and Eg.
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Analysis of the Dynamic Relationship between Runoff and Phosphorus Transport in the Menglianggu Small Watershed
Abstract:
[Objective] To investigate the characteristics of runoff-phosphorus loss hysteresis relationship under different rainfall types. [Methods] This study focused on the Menglianggu small watershed in the rocky mountainous area of northern China. Using data from 32 rainfall events recorded between 2010 and 2012, C-Q (concentration-discharge) loops and Pearson correlation analysis were applied. [Results] (1) During torrential rain, a large amount of phosphorus was released after soil saturation, causing the phosphorus concentration peak to lag behind the runoff peak. In the case of heavy rain, dissolved phosphorus was released from nearby sources, while particulate phosphorus was transported from distant sources to the runoff. During moderate rain, the transport of DIP (dissolved inorganic phosphorus), PP (particulate phosphorus), and TP (total phosphorus) was mainly influenced by surface runoff, whereas DP (dissolved phosphorus) was affected by soil and sediment. Light rain showed rapid transport of dissolved phosphorus and slower transport of particulate phosphorus. (2) The C-Q loops of phosphorus transfer exhibited various patterns during the runoff process. PP and TP often showed a clockwise lag, accounting for 18%~23%, mainly due to the strong scouring of surface runoff. The counterclockwise lag appeared in 12%~18% of the phosphorus components, resulting from the slow release of soil phosphorus and the resuspension of riverbed sediments. DP loss mainly exhibited a figure-eight positive loop, accounting for 16%, while DIP loss showed a figure-eight negative loop, accounting for 19%. Linear lags were less frequent, and complex lags ranged between 31% and 45%. (3) Under torrential and heavy rain conditions, DIP and DP had weak or negative correlations with runoff (Q), attributed to the rapid surface scouring, which caused particulate phosphorus to be more easily lost, while dissolved phosphorus was adsorbed by the soil or diluted by the runoff. In moderate rain, the appropriate runoff scouring force enhanced the releases of dissolved phosphorus. In light rain, runoff primarily transported particulate phosphorus attached to loose soil particles. PP and TP were consistently highly correlated across different rainfall types, indicating that TP mainly originates from PP. [Conclusion] The Menglianggu watershed needs to be protected against phosphorus loss for different rainfall conditions.
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Characteristics and drivers of spatial and temporal soil erosion in Anshun City, Karst region
Abstract:
[Objective] To explore the spatial and temporal evolution of soil erosion, driving factors and the interaction between driving factors in Anshun City, a karst area in southwest China, which can help the management of rock desertification and soil and water resources in the area. [Methods] The optimised RUSLE model was used to estimate soil erosion in Anshun City from 2005 to 2020, while the Random Forest Model (RF) was used to reveal the driving factors of soil erosion, and to estimate the effects of driving factor interactions on soil erosion in Anshun City from 2005 to 2020. [Results] (1) from 2005 to 2020, soil erosion in Anshun City generally shows that low-intensity soil erosion is distributed in the central, southeastern and eastern regions, while high-intensity soil erosion is distributed in the northern and southwestern regions. From the time point of view, soil erosion in Anshun City as a whole shows a trend of improvement, most of the areas of soil erosion grade mainly from high to micro-intensity erosion transfer, but there are local areas of erosion exacerbation phenomenon. (2) Rocky desertification has a greater impact on soil erosion in Anshun. The soil erosion intensity of Anshun is positively correlated with rocky desertification in the area accounting for 59.3% of the total area, which is highly correlated. Soil erosion with the increase of rocky desertification intensity shows the trend of increasing and then decreasing. (3) The most important land use types in Anshun City where soil erosion occurs are forest land, arable land and grassland, and the overall rate of soil erosion is in the order of forest land < grassland < arable land. (4) The analysis of the driving factors of soil erosion showed that the vegetation cover and management factor had the strongest explanatory power for the spatial and temporal dynamics of soil erosion in the study area, followed by the factor of soil and water conservation measures and the intensity of rock desertification. The results of driver interaction showed that the interaction between vegetation cover and management factor and soil and water conservation measures factor was the dominant factor, and the top ranked interactions all had the participation of vegetation cover and management factor. [Conclusion] Soil erosion intensity in Anshun City showed an overall trend of improvement from 2005 to 2020, but there was an increase in erosion in some areas. Vegetation cover, rock desertification intensity and land use have the strongest influence on soil erosion in Anshun City. Therefore, the future soil and water management process needs to focus on vegetation cover, rock desertification intensity and land use changes.
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Morphological Characteristics and Spatial Evolution Laws of rural settlements at Peak-cruster Depressions in Rocky Desertification Areas
Abstract:
[Objective]In order to explore the morphological characteristics and spatial evolution patterns of rural settlements in the rocky desertification area of the Peak Tree Depression, it is of great significance for the optimisation of the spatial layout of the rural settlements and the promotion of the urban-rural integration and sustainable development.[Methods] Based on the PLUS model, we predicted the distribution of rural settlements under the economic development scenario, natural development scenario and ecological protection scenario in 2035, identified the morphological features of rural settlements using the morphological spatial analysis (MSPA) method, and adopted the landscape pattern index, landscape integrated dynamic attitude and Ripley"s K-function method to realise the analysis of the morphological features and spatial evolution patterns of rural settlements in the past-now-future. The morphological characteristics and spatial evolution patterns of rural settlements in the past, present and future were analysed. [Results] (1) The area of rural settlements showed an upward trend from 1990 to 2022, with an increase of 6.09km2 in area and an increase in the number from 366 to 1253. The core and the edge are the dominant rural settlement types in the study area, with an increase in their areas of 1.90km2 and 1.51km2 respectively, which are mainly located in the central part of the study area, and the islands and branches are mainly located in the northern and northeastern parts of the study area. distributed in the northern and north-eastern parts of the study area and their areas increased by 1.07km2and 1.15km2 respectively.(2) The complexity, richness and fragmentation of rural settlement types show an overall increasing trend; the development of rural settlement types is the most gentle in 1990-2000, and the development is the most drastic in 2010-2022, and the expansion of rural settlement types mainly occurs in Xingjie and Laojie villages and the surrounding areas; rural settlement types show a tendency of agglomeration in the study scale. The rural settlement types show a tendency of agglomeration in the study scale, and with the increase of the spatial scale, the aggregation characteristics of the spatial distribution of rural settlements are weakened and the spatial scale of the urbanisation process is narrowed.(3) Under all three scenarios, the area of rural settlements shows an upward trend, and its area is 11.42km2, 7.68km2 and 9.14km2 respectively; the core is the absolutely dominant type in the study area, and its area increases by 4.02km2, 2.60km2 and 3.14km2 respectively, and the types of rural settlements show a clustered distribution on the spatial scale, and the ecological protection scenario will inhibit the rural The ecological protection scenario will inhibit the expansion of rural settlements.[Conclusion] Rural settlements in the study area are in the stage of rapid development, and the expansion of rural settlements is mainly manifested in the core expansion, while the expansion of isolated islands is exacerbating the complexity of the spatial distribution of rural settlements, and the process of urbanisation has gradually aggregated rural settlements in a smaller spatial scale.
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Liu Ping an, Hu Xiaomin ,Chen Siyu, Tian Ye, Ma Yutong, Luo Xinyu, Zhuang Zhuo rui，Zhang Min, Zhang Wenrui, Feng Zhibang, Li Zeli, Chen Qi*, Zhang Min*, Liu Zhiguang
Abstract:
[Purpose] Controlled release potassium chloride can achieve slow release of potassium ions synchronized with crop absorption, while ensuring the effectiveness of potassium ions in the soil, meeting the potassium demand of crops in the later stages of growth, and significantly improving potassium fertilizer utilization efficiency. Exploring the effects of long-term application of controlled release potassium chloride and its mixed fertilizers on maize yield and quality, providing technical support for achieving high-quality maize production. [Method] A field long-term positioning experiment based on the application of controlled release potassium chloride to summer maize (Zea mays L., Zhengdan 958) was conducted (starting from 2014). Six treatments were set up, including no potassium fertilizer (CK), constant ordinary potassium chloride (K), controlled-release potassium chloride (CRK1), reduced potassium amount by 1/3 polyurethane coated potassium chloride (CRK2), constant mixed potassium chloride (BBF1), and reduced potassium amount by 1/3 mixed potassium chloride (BBF2). Relevant indicators such as maize growth, soil potassium supply level, potassium absorption capacity, and photosynthesis were calibrated during the tasseling period, and corn quality and agronomic benefits were measured during the mature period. Measurement. [Results] (1) The corn yield, aboveground biomass, and economic benefits of BBF1 treatment were the highest, at 12157 kg/hm2, 19954 kg/hm2, and 19183 yuan/hm2, respectively. Under equal potassium conditions, compared with other potassium application treatments, they significantly increased by 5.68% to 16.06%, 1.11% to 10.44%, and 10.39% to 28.37%, respectively. Compared with BBF1 treatment, BBF2 significantly increased potassium fertilizer utilization by 9.44%. (2) The potassium ion content in CRK1 and BBF1 was significantly increased by 19.93% and 13.89% compared to K, and significantly increased by 16.05% and 19.03% compared to CRK2 and BBF2, respectively. After reducing by one-third, CRK2 and BBF2 were not significantly higher than K. CRK1 significantly increased SPAD value by 7.32%, LAI value by 7.04%, and net photosynthetic rate by 18.58% compared to K. After reducing by one-third, CRK2 was not significantly higher than CRK1 and K. (3) Compared with K treatment, CRK1 treatment increased the crude protein, starch, and oil content of corn kernels by 4.23%, 4.46%, and 5.65%, respectively; After reducing potassium by one-third, CRK2 still increased the crude protein, starch, and oil content of corn kernels compared to K treatment. The mixed application of controlled release potassium chloride and ordinary potassium chloride (BBF1) further increased the crude protein, starch, and oil content per unit area of corn kernels compared to K treatment, but the difference was not significant compared to CRK1 treatment; After reducing potassium by one-third, there was no significant difference in starch and oil content per unit area of corn kernels between BBF2 treatment and CRK1 and BBF1 treatment. [Conclusion] Controlled release potassium chloride can meet the potassium requirements for maize growth and quality formation, improve maize growth, optimize the quality traits of maize grains, significantly increase maize yield and potassium fertilizer utilization efficiency, reduce fertilizer input costs, and achieve the goal of reducing yield without reducing yield and quality.
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Spatial-temporal patterns and factors of soil moisture in the Middle Yellow River under changing environments
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[Objective] To identify the main driving factors of soil moisture in the middle reaches of the Yellow River, to analyze the impact of land cover and climate change on soil moisture changes in the middle reaches of the Yellow River, and to provide a theoretical basis for regional ecological environmental protection and high-quality development. [Methods] The SiB2 model was used to simulate the surface soil moisture (SSM) and root zone soil moisture (RZSM) in the middle reaches of the Yellow River for the years 2000, 2005, 2010, 2015 and 2020, and to analyze their spatial and temporal distribution patterns; the main driving factors were analyzed by combining the GeoDetector, Random Forest, and SHAP; and the contribution of land cover and climate change to the changes of SSM and RZSM was analyzed by using scenario-setting method. [Results] (1) The SiB2 model can better simulate the soil moisture in the middle reaches of the Yellow River after the parameter calibration. (2) Soil moisture in the middle reaches of the Yellow River showed overall spatial distribution characteristics of high in the south and low in the north, and there were differences in the distribution characteristics of SSM and RZSM under different ecological zones, different seasons and different land cover types. (3) Precipitation, soil type and downward shortwave radiation are the main drivers of SSM in the middle reaches of the Yellow River, and precipitation, soil type and land cover type are the main drivers of RZSM in the middle reaches of the Yellow River, and there are differences in the drivers of soil moisture in different ecological zones. (4) The effect of land cover type conversion on RZSM in the middle reaches of the Yellow River is regionally different, and the main direction of change is the decrease of RZSM due to the increase of LAI. (5) Compared to 2000, the decline in SSM and RZSM in 2020 is dominated by differences in climate change and land cover change, respectively. [Conclusion] Land cover changes in the middle reaches of the Yellow River from 2000 to 2020 led to a decline in soil moisture in the root zone, and precipitation magnitude had an important effect on changes in soil moisture after land cover type conversion.
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Study on spatial and temporal changes of vegetation cover and its driving factors in Panzhihua City, 1990-2020
Abstract:
[Objective] To investigate the spatial and temporal variation characteristics and driving factors of vegetation cover in Panzhihua City, and to provide theoretical basis for Panzhihua City to formulate regional ecological environmental protection programs and maintain regional ecological balance. [Methods] Based on Landsat-EVI data, combined with natural and socio-economic data, we analyzed the characteristics and driving factors of vegetation cover in Panzhihua City during the period of 1990-2020 with the help of like element dichotomous model, Sen+MK trend, partial correlation and optimal parameter geographic detector model. [Results] (1) The spatial distribution of vegetation cover (FVC) in Panzhihua City was characterized by “low in the south and high in the north”, with high-grade vegetation cover dominating. In the past 30a, the FVC ranged from 0.635-0.792, with the area of degraded area accounting for 17.70% and the area of improved area accounting for 44.97%. (2) The area proportion of areas where FVC was positively correlated with precipitation and air temperature is 61.87% and 57.40%, respectively. (3) Land use, elevation, and air temperature are the main influencing factors of spatial differentiation of FVC, with the influence above 0.2; most of the interactions among the factors were shown to be enhanced, among which, the influence can be increased to 43% after the coupling of slope direction and air temperature; the influences of the driving factors on the growth of vegetation in the study area have their appropriate ranges. [Conclusions] In the past 30a, FVC showed an overall upward trend, but the vegetation degradation is obvious in some areas. In the future, regional vegetation construction needs to focus on the terrain distribution pattern and climate change when optimizing the land-use pattern, in order to cope with the challenges of sustainable development of vegetation ecosystems under environmental evolution.
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Characteristics of Soil Saturated Hydraulic Conductivity and Its Influencing Factors at Different Landscape Positions in a Small Peak-Cluster Depression Watershed of Karst Region
Abstract:
[Objective] Peak-cluster depression is one of the important karst landform types. Exploring the influence of different landscape positions on soil saturated hydraulic conductivity (Ks) can provide a reference for further understanding of the hydrological processes in this area. [Methods] Ks and the corresponding soil physical and chemical properties of different soil depths in slope and depression were measured. By measuring Ks and soil physical and chemical properties of different soil depths in slope and depression, the distribution characteristics of Ks and the corresponding influencing factors were studied according to variance analysis, regression analysis and path analysis. [Results] Landscape position and soil depth had significant influence on Ks distribution (p<0.05). The influence of landscape position was mainly identified at 0—10 and 20—30 cm soil depths, and the influence of soil depth was primarily occurred in the slope. The effect of land use on Ks was not significant (p>0.05). The influence of landscape position on soil particle composition and total phosphorus was not obvious (p>0.05), but organic carbon, total nitrogen and bulk density changed significantly with landscape position (p<0.05). Ks of slope location was significantly positively correlated with silt, sand, organic carbon and total phosphorus (p<0.05), and significantly negatively correlated with clay and bulk density (p<0.05). There was a significant positive correlation between Ks of depression location and bulk density (p<0.05). Path analysis indicated that bulk density and organic carbon were the primary factors affecting Ks in both slope and depression. The regression equations of Ks in slope and depression were established based on multiple stepwise regression, and the variance explanation rates of influencing factors were 76.2% and 32.6%, respectively. [Conclusion] The results showed that the difference in geomorphic features had a major impact on the distribution of soil hydrological parameters. It can provide a scientific basis for the study of soil and water processes in small peak-cluster depression watershed of karst region.
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Effect of hydropower station on vegetation temporal and spatial change in the middle reaches of Jinsha River
Abstract:
[Objective] To explore the effects of hydropower stations on the temporal and spatial changes of vegetation, clarify the response relationship of vegetation changes to hydropower station construction and climate factors, and provide a reliable scientific basis for regional sustainable development and sustainable operation of hydropower stations. [Methods] In this paper, the normalized vegetation index (NDVI) was used to reflect vegetation change. Google Earth Engine (GEE) was used as the computing platform, coupled with ModTrendr algorithm, Theil Sen-MK, contribution degree analysis and partial correlation analysis methods to explore the effects of hydropower stations in the middle reaches of the Jinsha River on the spatial-temporal changes of vegetation during 2000-2022. And analyze the effect of climate in it. [Results] (1) The negative mutations were concentrated from 2011 to 2014, and the mutation area was concentrated in the catchment area. The forward mutation was concentrated in 2015 and 2017, and the mutation area was concentrated within the 5-km buffer zone of the riverbank. The time for vegetation to produce positive response was 1-4 years after impounded water, and the mutation intensity gradually weakened along the riverbank. (2) The vegetation NDVI around each hydropower station presents an overall upward trend (0.0002-0.0028/a), and an upward (gentle) -- downward -- upward trend before, during and after construction; (3) The regional vegetation change is mainly caused by the joint action of human activities (hydropower station construction) and climate change, and the explanation degree is 69.12%. The contribution of human activities is much higher than the contribution of climate change. (4) The partial correlation coefficients of temperature, precipitation and NDVI are -0.28 and -0.29, respectively. The partial correlation coefficients of temperature and precipitation differ greatly in different stages of hydropower station, indicating that hydropower station will affect regional climate. [Conclusion] Hydropower station has a negative impact on vegetation during construction and a positive impact on vegetation after operation. The impact of hydropower station construction on vegetation is higher than that of climate change, and the construction of hydropower station may affect local climate, and the overall correlation between temperature and precipitation and vegetation NDVI decreases.
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Response of Soil Moisture to Typical Rainfall at Different Stands and Slope Sites in Qiaoshan Forest Region
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[Objective]Rainfall is the main source of soil water supply, which directly affects the distribution characteristics of soil water, and then affects the growth of vegetation. [Methods]This study took the Qiaoshan forest area in the southern Loess Plateau as the research object. Through monitoring the rainfall and soil moisture at different depths of typical stands (broadleaf pure forest and mixed forest), the response characteristics of soil moisture at different layers to rainfall patterns under different vegetation cover and slope location conditions were explored. [Results](1) Rainfall during the study period was mainly concentrated in August, September and October, with the highest rainfall of 251.7mm in September. The seasonal difference of soil moisture in the same soil layer at different points was significant (p≤0.05), and the average soil moisture in different soil layers was the lowest in summer. (2) During moderate rainfall events, only shallow soil moisture content responded to rainfall, and the response intensity of soil moisture content to rainfall in mixed forest was greater than that in broad-leaved pure forest. (3) In the event of heavy rain, the response of soil moisture to rainfall was greater in the mixed forest than in the pure broad-leaved forest, and the response relationship was as follows: the shallow layer was lower slope > middle slope > upper slope, and the deep layer was upper slope > middle slope > lower slope. (4) In the event of heavy rainfall, the response of soil moisture to rainfall was greater in broad-leaved pure forest than in mixed broad-leaved forest, and the response relationship was as follows: in shallow layer, it was lower slope > middle slope > upper slope, and in deep layer, it was upper slope > middle slope > lower slope. (5) In the three rainfallings, the supplement amount of the mixed forest was 1.087, 1.653 and 1.004 times that of the pure broad-leaved forest, respectively. [Conclusion]It is of great significance to study the response of soil moisture to rainfall and the process of shallow soil moisture movement in Qiaoshan forest area for optimal allocation of rainfall resources and sustainable restoration of forest ecosystem.
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Study on Urban Landscape Ecological Risk Measurement and Influencing Factors in the Yellow River Delta
Abstract:
[Objective]The Yellow River Delta, a typical ecological fragile area, faces prominent landscape ecological risk (LER) due to multiple factors. Systematic understanding of landscape risk is crucial for optimizing landscape patterns and effectively addressing ecological challenges.[Methods] Taking Dongying, a typical city of the Yellow River Delta as the study area to construct a assessment framework of ecosystem service value and the probability of landscape ecological damage in terms of “stress-vulnerability-resilience”. The ESDA and Geographic detector were used to explore the spatial heterogeneity and influencing factors of LER at the grid scale.[Results](1) The average value of LER in Dongying is 0.15, generally shows a spatial pattern of “high in the north and east, low in the middle and southwest”. The total value of ecosystem services is about 3 175.99 billion yuan (93% of GDP), indicate unsustainable economic growth, showing a pattern of gradual diminution form the north and eastern coast to the southwestern. The probability of ecological damage is 0.43, showing a pattern of “staggered distribution of high and low in the north and east, and overall low in the southwest part”.(2) It is found that the LER showed significant clustering in spatial distribution, with a global Moran’s I index of 0.747. In terms of agglomeration zoning, the HH risk agglomeration area accounts for 32.48% of the area of the risk zone, which is mainly distributed in the continuous distribution zone formed by the coastal zone in the north and east of Dongying.(3) The LER of Dongying is mainly dominated by factors of socio-economic foundation and environmental location conditions. In the citywide area, the determinant of coastline distance was 0.43, which was the primary factor dominating the urban LER. In contrast, in the urban area, the determinant of population density was 0.38, which was the decisive factor influencing the urban LER.[Conclusions] This study enriches the LER assessment method theoretically, and provides empirical support for ecological protection and risk management in the Yellow River Delta.
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Effects of organic fertilizer substitution and aggregation on microfauna communities in red soils
Abstract:
[Objective] Red soil is a typical soil in southern China, and organic substitution is an important way to improve the physicochemical properties of red soil. This study aims to explore the effects of different organic substitution materials and aggregation on the microfauna communities in red soil. [Methods] In this study, five long-term fertilization treatments were collected: application of inorganic nitrogen, phosphorus, and potassium (NPK) fertilizer alone (I), NPK + peanut straw (IPS), NPK + rice straw (IRS), NPK + radish (IR), and NPK + pig manure (IPM). Soil aggregates were fractionated, and high-throughput sequencing was used to determine the microfauna communities within the aggregates. [Results] Compared to I, IPM and IRS significantly increased soil organic matter content, while IPS and IR had relatively smaller effects. IPM also significantly increased soil pH, total nitrogen, and available phosphorus content. Organic substitution had no significant effect on the diversity of soil microfauna but significantly influenced their community structure. Nematodes were the most abundant soil microfauna in upland red soil, with a relative abundance of 93.0% in I. IPM and IRS significantly reduced their relative abundance to 62.2% and 70.0%, respectively, while IPS and IR had smaller effects. Aggregate size significantly affected the Shannon and Chao1 indices of soil microfauna, with the diversity indices of 53-250 μm and <53 μm aggregates significantly higher than those of 250-2000 μm and >2000 μm aggregates, indicating that smaller particle sizes are more conducive to increasing soil microfauna diversity. Aggregate size also significantly affected soil microfauna community structure, but its impact was weaker than that of organic substitution. [Conclusion] Both organic substitution and aggregate size could significantly affect soil microfauna communities, with pig manure and rice straw having greater effects than peanut straw and radish. The aggregation process reduced microfauna diversity in red soils.
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Extracellular Enzyme Stoichiometric Characteristics of Subtropical Forest Soil under Forest Fire Disturbance
Abstract:
Forest fire, as the main natural and human disturbance process of subtropical forest ecosystem, seriously affects the soil biochemical cycle. However, the response of soil extracellular enzyme activities to the restoration process after forest fire disturbance is still unclear. In this study, the soils of subtropical secondary forests at different restoration stages after forest fire disturbance were selected as the research object, and the subtropical forest soils in seven restoration stages of secondary forest were selected by using the method of spatial substitution time series, and the soil was divided into old forest (60-70 years), middle-aged forest (30-40 years) and young forest (<20 years). Through the determination of soil carbon (C), nitrogen (N), phosphorus (P) related invertase activities, to reveal the forest fire disturbance of subtropical forest soil extracellular enzyme activity and its stoichiometric characteristics succession rule. The results showed that the activities of soil cellulose hydrolase (CBH) and β-N-acetylglucosaminidase (NAG) increased significantly with the time of succession, while the activities of other enzymes did not change significantly. The results of correlation analysis and redundancy analysis showed that soil C and N contents were the key factors affecting the change of soil extracellular enzyme activity. In addition, the ratios of soil extracellular enzyme C, N and P in young, middle and old forests were 1:0.94:1.53, 1:1.02:1.63 and 1:0.99:1.47, respectively, indicating that the growth of forest soil microorganisms in subtropical areas was limited by P, and improves gradually with the increase of restoration years after forest fire disturbance. In summary, after forest fire disturbance, the extracellular enzyme activity of forest soil showed an increasing trend with the restoration time, and the stoichiometric characteristics of soil extracellular enzyme gradually tended to be stable, indicating that soil health status of subtropical forest was gradually improved with the restoration process of forest fire disturbance.
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Spatial and Temporal Correlation Analysis and Prediction of Land Use Ecological Risk and Carbon Stock in Yunnan Province
Abstract:
[Objective]To explore the correlation between land use ecological risk and carbon storage, in order to improve the regional ecological risk prevention and carbon sequestration capabilities, so as to effectively guide the formulation of environmental management policies.[Methods] The landscape pattern index, PLUS and InVEST models were used to analyze and predict the spatial and temporal changes of land use ecological risk and carbon storage in Yunnan Province under scenarios of natural development, economic development, and ecological protection. Spearman correlation analysis and spatial autocorrelation analysis were used to explore the correlation characteristics.[Results] (1) Land use in Yunnan Province is dominated by forest land, exceeding 57% of the total area.(2) From 2000 to 2020, the ecological risk in Yunnan Province decreased slowly, with lower and medium-risk areas exceeding 50%, the spatial distribution remained relatively stable, the change of risk mainly occurred between adjacent levels, and the high-level risk area transferred to the low-level risk area by 39 675.06 km2.(3) Carbon storage in Yunnan Province initially increased and then decreased, with a total reduction of 2.257×107 t over 20 years. Forest land contributed the most to carbon storage, while large-scale conversion of cropland, grassland, and forest land into construction land was the main reason for the reduction in carbon storage.(4) The ecological risk and carbon storage of Yunnan Province will decrease under all three scenarios in 2030. Under the ecological protection scenario, forest land area increased by 895.83 km2 compared to 2020, high and higher ecological risks significantly decreased, and the reduction in carbon storage was suppressed, indicating that this is the optimal scenario for the future development of Yunnan Province.(5) Ecological risk and carbon storage in the study area are negatively correlated, with spatial distribution mainly characterized by low-high and high-low aggregations.[Conclusion] The study provides various recommendations based on the spatial aggregation characteristics of ecological risk and carbon storage in Yunnan Province, offering a scientific basis for preventing ecological risks and enhancing carbon storage in the region.
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Effects of Water and Nitrogen Management on Soil Nitrogen Metabolism Enzyme Activity and Wheat Nitrogen Utilization
Abstract:
[Objective] To explore the effects of water and nitrogen management on soil nitrogen metabolism enzyme activity and wheat nitrogen utilization under irrigation based on soil moisture. [Methods] The experiment adopted a two-factor split zone design, and the main plot was three irrigation levels: the relative water content of 0-40 cm soil layer at jointing and anthesis stages of wheat was supplemented to 65% (W1), 75% (W2) and 85% (W3). Four nitrogen application rates were applied as the subplot: pure nitrogen 0 (N0), 150 (N1), 180 (N2) and 210 (N3) kg/hm2. Soil nitrogen metabolism enzyme activity, nitrogen accumulation and translocation, nitrogen nutrition index (NNI), residual amount of nitrate nitrogen, grain yield, water- and nitrogen-use efficiencies were measured and analyzed in two wheat growing seasons from 2022 to 2024. [Results] (1) Supplementing irrigation to 75% and applying 180 kg/hm2 nitrogen (W2N2 treatment) could significantly improve the activities of soil urease and protease, reduce the activity of soil nitrate reductase, facilitated the transformation of soil nitrogen into crop absorbable forms. According to the results of variance analysis, the effects of irrigation level, nitrogen application rate and their interaction on soil nitrogen metabolism enzyme activity reached a very significant level (p<0.01). In addition, W2N2 treatment significantly reduced the residual amount of nitrate nitrogen in the 60-120 cm soil layer, and reduced the risk of soil nitrogen leaching. (2) Both W2N2 and W2N3 treatments could significantly increase nitrogen accumulation of vegetative organs, nitrogen translocation and grain nitrogen accumulation, and had the best NNI, which could meet the nitrogen requirements of wheat. The effects of irrigation level, nitrogen application rate and their interaction on NNI, nitrogen accumulation and transport of wheat reached a significant level (p<0.01). (3) The highest grain yield could be obtained by W2N2 treatment, while further increasing water and nitrogen input had no significant effect on grain yield. Different irrigation levels and nitrogen application rates had significant effects on grain yield, and the interaction between the two factors reached a very significant level (p<0.01). The decision coefficient of irrigation level and nitrogen application rate on grain yield was 0.313 and 0.485, respectively. (4) W2N2 treatment has a high water- and nitrogen-use efficiencies, that would be easy to cause a significant decrease under the continuous improvement of irrigation level and nitrogen application rate. The effects of irrigation level, nitrogen application rate and their interaction on water- and nitrogen-use efficiencies of wheat reached a significant level (p<0.01). Compared with W2N2 treatment, the two year average nitrogen fertilizer agronomic efficiency of W2N3, W3N2 and W3N3 treatment was reduced by 13.02% to 26.34%, the nitrogen utilization rate was reduced by 9.77% to 23.64%, and the irrigation water use efficiency was reduced by 2.88% to 38.10%. [Conclusion] The soil relative water content of 0-40 cm soil layer at the jointing and anthesis stages of wheat was supplemented to 75%, and nitrogen was applied at 180 kg/hm2 could significantly improve wheat grain yield, water- and nitrogen-use efficiencies, nitrogen accumulation, nitrogen translocation in vegetative organs and grain nitrogen accumulation, and had the best soil nitrogen metabolism enzyme activity and NNI. It is the best water and nitrogen management for wheat with high yield and high efficiency in Huang-Huai-Hai region.
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Soil Priority Flow Characteristics in Coal Mine Subsidence Area Under Different Rainfall Duration
Abstract:
Abstract:[Objective] The research on the preferential flow characteristics triggered by cracks in the coal mining subsidence area can provide support for the scientific and rational development of water resource management and ecological management practice in the mining area. [Methods] Three cracks of the same width (3 cm) were selected in the coal mining subsidence area of Shenfu-Dongsheng Coal Field to carry out the staining tracer test with the same rainfall intensity and different rainfall durations. Processing software such as Adobe Photoshop 2020, Image Pro Plus 6.0, SketchUp Pro 2019, and Auto CAD 2019 were used to analyze the preferential flow characteristics of cracks under different rainfall calendars. [Results] (1) the soil volumetric water content, porosity, and saturated hydraulic conductivity in the priority flow occurrence area of the Shenfu-Dongsheng coal mining collapse area were greater than those in the non-priority flow area, and the volumetric weight and field water-holding capacity were less than those in the non-priority flow area zone; (2) When the rainfall duration was 10min, 20min and 30min, the corresponding depths of substrate flow were 5cm, 8cm and 10cm, respectively; and the depths of preferential flow were 26.4cm, 47.7cm and 44.3cm, respectively. the longer the rainfall duration, the deeper the development of substrate and preferential flow; (3) In general, the staining area ratio at each test site showed a decreasing trend with the increase of soil layer depth, and the morphology showed an S shape. When the rainfall duration was short, the magnitude of change in the coloring area ratio with soil layer depth was small; when the rainfall duration was long, the fluctuation of the coloring area ratio curve increased. (4) In general, with the increase of soil depth, the number of wide staining paths was decreasing, the number of fine staining paths was increasing, and the total number of staining paths showed a tendency of increasing and then decreasing. And the longer the rainfall duration, the wider the soil staining paths at the same depth, and the number of wide paths was more. [Conclusion] The f indings can provide scientific basis for land reclamation and ecological management in coal mining areas.
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Response of soil microbial diversity, community structure, and functional potential to primary forest conversion in northwestern Hunan province
Abstract:
[Objective] We explore the impact of primary forest conversion on soil microbial community structure and predicting soil microbial functions, and provide theoretical reference for soil health preservation. [Methods] The subtropical typical primary evergreen broad-leaved forest and the adjacently converted conifer plantation, orchards, sloping tillage, and rice paddy were chosen in northwest Hunan province. We assessed the response of bacterial and fungal genomic diversity, community structure, and predicted functions to the primary forest conversion. [Results] Comparing to the primary forest, the bacterial diversity was decreased by 29%-34% in the cultivated lands, whereas fungal diversity was decreased by 42%-49% in the orchards. The response direction and magnitude of soil bacterial and fungal predicted function depended on the specific soil function and converted land-use type. Comparing to the primary forest, the relative abundance of global and overview maps, carbohydrate metabolism, and metabolism of cofactors and vitamins were 9%-25% higher in orchards and croplands, whereas the relative abundance of membrane transport, signal transduction, cellular community?prokaryotes were 11%-27% lower in orchard and croplands. The relative abundance of endophyte-litter saprotroph?soil saprotroph in sloping tillage were 32%-42% lower than those in the primary forest; however, the animal pathogen and plant pathogen were 10%-397% higher than those in the primary forest. No significant differences of >50% of the relative abundance of predicted microbial functions were found between the primary forest and plantations. The labile C and total N contents decreased by 25%-70% following the primary forest conversion, resulting in a 10%-86% reduction in the relative abundances of variibacter and bradyrhizobium, which was the main pathway regulating the predictive functions of soil bacteria. In addition, the predicted bacterial function is mainly regulated by soil moisture and labile organic C content, whereas the predicted fungal function is mainly regulated by soil pH, quantity of labile organic C, and nutrient availability. [Conclusion] This study suggests that the conversion of primary evergreen broad-leaved forest to Cunninghamia lanceolata plantation is relatively conducive to the maintenance of soil health and functional potential, whereas the conversion to sloping tillage can increase the risk of soil-borne diseases on crops. Our findings provide a theoretical basis for prediction regional soil health evolution and rational land planning.
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The Spatial Differentiation and Correlation of Ecological Stoichiometry Characteristics of Cynodon dactylon and Soil in the Water-Level Fluctuation Zone of the Three Gorges Reservoir Area
Abstract:
[Objective]Cynodon dactylon is important component and dominant species in ecosystem of the water-level fluctuation zone (WLFZ) of the Three Gorges Reservoir, which is the largest hydropower project in the word. Investigation on the spatial distribution patterns and correlations of nutrient and stoichiometric characteristics between C.dactylon and its periradical soil holds significant importance in comprehending nutrient cycling as well as species adaptation features within the WLFZ.[Methods]This study conducted a field investigation of C.dactylon and its periradical soil across 16 sections in the WLFZ of the Three Gorges Reservoir Area from Banan to Yichang. The carbon, nitrogen, and phosphorus contents in plant organs (roots, stems, leaves) and soil were analyzed to explore the spatial heterogeneity and interrelationships of the ecological stoichiometry characteristics between C.dactylon and soil.[Results](1) The soil in the WLFZ associated with C.dactylon demonstrated a distinct "nitrogen-poor and phosphorus-rich" characteristic with significant spatial variations in nutrient contents and stoichiometric ratios. Specifically, soil organic carbon, total nitrogen, total phosphorus, C/N ratio, and C/P ratio exhibited a consistent increase from upstream to downstream sections. while, N/P ratio showed relatively stable, indicating synchronized spatial changes in nitrogen and phosphorus contents in the soil. (2) From upstream to downstream of WLFZ, the carbon contents in various organs of C.dactylon exhibited a decreasing trend, while nitrogen and phosphorus contents showed significant increasing patterns. This trend could be attributed to intensified sedimentation and resultant higher soil nutrient supply levels in the downstream WLFZ with the prolonged flooding time. Notably, the nitrogen content in the leaves demonstrates a degree of spatial stability, suggesting that C.dactylon could absorb nitrogen efficiently and meet its leaf nitrogen requirements prioritizly under nitrogen-deficient conditions. (3) Generally low variations in the stoichiometric ratios in organs of C.dactylon were found. However, the variability in C/N and C/P ratios in roots and stems were slightly strong than that in leaves, suggesting that C.dactylon has evolved a strategy maintaining stable physiological functions in leaves. (4) There were significant correlations of the nutrient contents between C.dactylon and soil, with the nitrogen supply of soil being the key factor influencing the variation of nutrient contents in C.dactylon. The correlations of stoichiometric ratios between C.dactylon and soil is relatively weak. (5) C.dactylon in the WFLZ generally exhibited strong homeostasis with the homeostasis index decreasing from upstream to downstream.[Conclusion]In the context of changing water inundation patterns, the nutrient contents in C.dactylon and soil exhibit significant spatial variations and cooperative association, implying that the spatial evolution of soil nutrients has a profound impact on the ecological stoichiometry characteristics of C.dactylon. While, the C.dactylon exhibits limited spatial differentiation in stoichiometry, indicating its strong adaptability to the heterogeneous soil conditions through adjustments in nutrient demand strategy. The feedback relationships of stoichiometry between C.dactylon and soil may exhibit instability under periodic waterlogging stress in WFLZ.
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Elementary Study on Gully Classification on the Qinghai-Tibet Plateau
Abstract:
[Objective] Traditional gully classification systems focus on agricultural landscapes. However, on the Qinghai-Tibet Plateau, where human activity is limited, gullies primarily occur in natural landscapes. Therefore, it is necessary to propose a tailored gully classification system that is suited to the natural landscapes of the Qinghai-Tibet Plateau. [Methods] Extensive field investigations were conducted in typical regions of the Qinghai-Tibet Plateau, including the Yarlung Zangbo River and its two tributaries, the Southeast Tibet, the Qiangtang Plateau, the Three-River Headwaters region, the Hehuang Valley, the Qaidam Basin, and the Qilian Mountains. These field studies were complemented by indoor interpretations using sub-meter high-resolution remote sensing imagery. [Results] Various landforms that resemble but are not gullies in terms of genesis or morphology were identified and distinguished. The gullies were classified based on multiple criteria, including scale, genesis, the landform in which they developed, and morphology. The gullies were classified by scale into small, medium, large, and giant gullies; by genesis into rainfall-runoff gullies, snowmelt-mudflow gullies, glacial gullies, permafrost thermal gullies, and human activity gullies; by the landform in which they developed into steep-slope gullies, valley-bottom gullies, gentle-slope gullies, cliff gullies, terrace gullies, tableland-edge gullies, and tableland-surface gullies; and by morphology into straight gullies, curved gullies, spoon-shaped gullies, strip-shaped gullies, widened gullies, narrow-long gullies, wide-short gullies, radial gullies, parallel gullies, and dendritic gullies. [Conclusion] This paper preliminarily proposes a comprehensive gully classification system based on multiple criteria suitable for the characteristics of the Qinghai-Tibet Plateau. It suggests using scale as the primary basis for comparison with gully classification systems in other regions, such as the Loess Plateau. This provides support for soil erosion research and ecological environment protection on the Qinghai-Tibet Plateau.
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Spatial Coupling Pattern of Soil Layer and Upper Epikarst Zone in a Dolomite Hillslope
Abstract:
Based on the in-depth geotechnical trench excavation tests on the full slope scale of typical dolostones, the spatial coupling development characteristics between the soil and upper epikarst zone on dolostone slopes have been preliminarily clarified combined with the field measured data,. The results indicate that: 1) The thickness of soil and upper epikarst zone on dolomite slopes gradually increases down the slope. The average thickness of the upper epikarst zone on a slope scale is 50 cm, with an average volume of 0.47 m3/m2, accounting for 43.9% of the total volume of the soil profile, indicating that the ecological function of epikarst in karst regions is extremely important; (2) The geotechnical structure of the dolomite slope exhibits strong spatial heterogeneity. The spatial heterogeneity of the underlying upper epikarst zone (C+C0 is 18.88) is significantly higher than that of the overlying soil layer (C+C0 is 15.84) ; (3) The overall soil thickness,,especially the thickness of soil layer B, is significantly positively correlated with the degree of weathering in the epikarst, indicating that the increase in soil thickness promotes the weathering of the underlying epikarst, and there is a clear coupling and collaborative development relationship between soil and upper epikarst zone The soil and upper epikarst zone in karst regions have evolved in a mutually reinforcing manner, with the epikarst below the soil layer potentially acting as an essential substrate for the karst ecosystem. The soil thickness and the depth of its B horizon exhibit a significant positive correlation with the thickness of the epikarst, which may be critical parameters for predicting epikarst depth on karst slopes. The evaluation of karst water and soil resources demands a holistic approach that encompasses both soil and the underlying bedrock weathering layer.
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Effects of no-tillage with mulching during fallow on soil physical characteristics and potato yield in different precipitation years
Abstract:
[Objective] Aiming at the problems of equal emphasis on spring drought and spring cold in the southern mountainous areas of Ningxia, and shallow effective soil surface. [Method] From 2014 to 2016 three different no-till mulching modes were set up after autumn crops were harvested for three consecutive years: No-tillage straw mulching (NJ), no-tillage mulching film (ND), no-tillage no mulching (NB), and no-tillage no mulching as control (CK). The effects of no-tillage with mulching mode on soil moisture retention, precipitation utilization characteristics and potato yield under different precipitation years in arid region of south Ningxia were analyzed. [Result] The soil water storage and water storage efficiency in fallow period were the highest under ND treatment, which increased by 7.60% and 140.35% compared with CK, respectively. NJ treatment was the highest in normal year and dry year, which was increased significantly by 11.18% and 65.43% and 28.42% and 122.72% compared with CK, respectively. NJ treatment had the highest soil water storage in normal and dry years, which was increased by 10.51%, 12.89% and 20.04%, respectively, compared with CK treatment. ND treatment significantly increased soil water storage by 11.42% compared with CK at seedling stage in the relatively dry year. The decrease of soil water storage in ND treatment was 22.26% and 36.57% higher than CK treatment in early growth stage (sow-budding stage) and middle growth stage (budding stage - expanding stage) of relatively dry years, respectively. NJ treatment significantly increased by 1.21 times, 7.14 times and 13.91%, respectively, compared with CK treatment, in the late growth period (expanding to harvest period) and middle and late growth period (emerging bud to harvest period) of the relative drought years and drought years, respectively. Potato yield was the highest in NJ treatment, which was significantly increased by 51.80% compared with CK treatment. In normal year and dry year, ND treatment significantly increased by 6.35% and 71.36% compared with CK treatment, respectively. Correlation analysis showed that the decrease of soil water storage from tuber formation to tuber expansion played an important role in potato yield, yield composition and water use efficiency. The annual precipitation use efficiency, precipitation use efficiency and water use efficiency in growth period were better under NJ treatment than CK, which were significantly increased by 51.79%, 51.80% and 50.52%, respectively. ND treatment significantly increased by 35.14%, 36.14% and 21.61% compared with CK treatment in normal year and dry year, respectively. [Conclusion] no-tillage combined with mulching can effectively improve soil water storage and soil moisture retention during fallow period and growth period, and significantly improve potato yield and water use efficiency. The no-tillage and straw mulching mode can realize continuous potato yield and water use efficiency.
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Transpiration and soil hydrothermal studies of orchards based on dynamic parameterization of leaf area index
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[Objective] As a key parameter in the simulation study of ecosystem water cycle process, the rapid dynamic simulation of the Leaf Area Index (LAI) can solve the limitation that the coupled soil water-vapor-heat-air model STEMMUS (Simultaneous Transfer of Energy, Mass and Momentum in Unsaturated Soil) can only use fixed or measured as an input parameter. [Methods] In this paper, the "plant leaf area development sub-module" in EPIC model was coupled with the STEMMUS model, and the model was calibrated and validated using the measured fruit tree transpiration, soil moisture and soil temperature data under the apple growth conditions in the mountain apple Experimental demonstration base of Zizhou County in 2019 and 2020, so as to evaluate the applicability of the coupled model on the Loess Plateau. [Results] The results showed that by optimizing the plant growth parameters, the coupled leaf area development sub-module of the STEMMUS model significantly improved the simulation accuracy of the transpiration and water consumption process of apple trees, with the normalized root mean square error (NRMSE) of the calibration and validation years increasing from 40.2% and 61.9% in the original model to 30.0% and 33.2% in the coupled model, and the mean absolute error (MAE) increasing from 0.52 mm d-1 and 0.64 mm d-1 to 0.42 mm d-1 and 0.38 mm d-1. Meanwhile, the coupled model can better simulate the soil hydrothermal dynamic processes in apple orchards, and the NRMSE of simulated soil water content and soil temperature at the calibrated period and validation period ranged from 1.4% to 32.9% and 2.9 to 9.5%, and the MAE ranged from 0.13 to 4.26 cm3 cm-3 and 0.34 to 1.49°C, respectively. [Conclusion] The high agreement between the simulated and measured values indicates that the coupled model can accurately describe the dynamic growth process of fruit tree leaf area and the ecohydrological process of orchard in the Loess Plateau, and this study can provide technical support for the research of the ecohydrological process of orchard in Loess area.
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Mechanisms of Soil Physical Crust Crack Formation
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[Objective] Soil physical crusting is a common obstructive phenomenon on exposed surfaces, leading to shrinkage cracks as the soil dries, directly affecting soil moisture retention and utilization. This study aims to clarify the development patterns of cracks in physical crusts. [Method] Artificial rainfall was employed to simulate the formation of different types of physical crusts, followed by crack formation during the drying process. Parameters such as crack area, perimeter, length, and width were measured using a paraffin filling method, and the geometric characteristics and spatial variations of cracks in depositional crusts (DC) and structural crusts (SC) under different conditions were quantitatively analyzed. [Results] The results indicate that (1) cracks in depositional crusts (DC) exhibit significantly higher geometric parameters compared to those in structural crusts (SC); (2) with increasing rainfall duration, the crack shape coefficient and density decrease, while the average crack width increases; (3) three types of lateral shrinkage cracks were identified: penetrating shrinkage (PS), interlocking shrinkage (IS), and suspended shrinkage (SS). As rainfall duration increases, the proportion of PS increases, while IS and SS proportions decrease; (4) as soil depth increases, cracks in depositional crusts display a stepped decrease and a brief increase under different rainfall durations, while cracks in structural crusts show an initial sharp decrease followed by a gradual decline. [Conclusion] The type of crust and rainfall duration are crucial factors influencing crack development. This study highlights the impact of crusting on crack formation, suggesting timely field management practices to modify water infiltration and evaporation, providing technical support for effective field management.
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Spatial and Temporal Changes and Dynamic Driving Forces of Soil Water Erosion in Arid and Semi-arid Regions of China from 1990 to 2020
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[Objective] The ecological environment in China''s arid and semi-arid regions is highly vulnerable, with soil erosion posing a significant challenge. In light of climate warming, investigating the current state of soil water erosion in these areas is of critical importance.[Methods] This study based on the RULSE model to calculate the model factors and soil water erosion modulus for China''s arid and semi-arid regions for the years 1990, 2000, 2010, 2015, and 2020, and conducts an accuracy validation (R2 = 0.60).Establishing on these calculations, the optimal parameter geographic detector is utilized to analyze the dynamic driving forces and changes associated with both single and interaction factors.[Results] The key findings are as follows: (1) From 1990 to 2020, the average annual soil water erosion in China''s arid and semi-arid regions amounted to 4.71×1010 kg , exhibiting a slight upward trend in the soil water erosion modulus at a rate of 0.0007 t·hm?2·a?1. (2) The intensity of soil water erosion is predominantly characterized by slight to moderate erosion. The proportion of areas experiencing increases and decreases in soil water erosion intensity is both rising, while the proportion of areas with stable soil water erosion intensity is declining. (3) Slope, precipitation, and precipitation erosion force are identified as the primary single driving factors of soil water erosion in these regions from 1990 to 2020, with these three factors alternating as the main dominant factor throughout the study period. Interactions between any two selected factors enhance the explanatory power regarding soil water erosion, with the interaction between slope and precipitation erosion force consistently serving as the primary dominant interaction factor during the study period.Overall, the soil water erosion situation in China''s arid and semi-arid regions is experiencing slight deterioration.[Conclusion] To effectively address this issue, it is crucial to consider topographical and precipitation characteristics concurrently when implementing management measures aimed at improving soil water erosion conditions in arid areas.
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Effects of tillage disturbance on the slope shape and micro-topographic features on typical sloping cropland slopes of southwestern alpine-canyon area
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[Objective] The objective of this study is to investigate the effects of various tillage operations on slope shape and micro-topographic features on typical sloping cropland slopes of southwestern alpine-canyon area. [Methods] 50-time conventional tillage and contour tillage events were applied to rectangular plots (5 m × 20 m) with a slope of 15° to examine the impacts of tillage disturbance on the slope shape and micro-topographic features by combining the stylus method and 3D laser scanning technology. [Results] After 50-time conventional tillage, the slope shape gradually evolved from a linear slope to a “”-type composite slope, while contour tillage evolved to a “”-type . After 50- time successive tillage, the range of soil loss under conventional tillage and contour tillage accounted for 15% and 11%, and the range of accumulated soil accounted for 13% and 6% on the whole slope, respectively. The two kinds of tillage disturbance patterns caused significant changes in the surface roughness and topographic undulation on the slope, and the degree of change of conventional tillage was greater than that of contour tillage. The average thickness of the soil loss by conventional tillage and contour tillage were 1.17 and 0.45 cm/time, respectively. The indirect effect of tillage disturbance patterns on soil loss was the largest, while the direct effect of tillage frequency on soil loss was the largest. [Conclusion] Tillage frequency and tillage pattern were the most important factors affecting slope shape and micro-topographic features. As the frequency of tillage increased, and the amount of soil loss gradually increased.
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Effect of freezing on wind erosion resistance of sand dune soil
Abstract:
To investigate the effect of winter soil freezing on soil erodibility and anti-erodibility in the Yellow River section of the Ulan Buh Desert. we conducted particle size screening experiments on dry, wet, and frozen sand on the windward slope of mobile dunes, along with shear strength tests before and after freezing. The results show that sand particle sizes at three positions on the dunes increased due to the bonding effect of water. The particle size peak shifted from 0.15~0.2 mm to 0.3~0.355 mm, with approximately 35.12% of fine sand particles bonding to form larger, medium sand particles. After freezing, very coarse sand emerged, and the particle size peak shifted to 0.5~0.6 mm.Sand particles bonded and coarsened, forming coarse and very coarse sand (52.02%). The proportion of highly erodible particles decreased to 23%～36%, while moderately erodible particles increased to 53%～63%, and hard-to-erode particles increased to 2%～17%. As soil moisture in the dunes increased, the cohesion of frozen soil significantly increased (p < 0.05), along with shear strength and erosion resistance (p < 0.01). Freezing coarsened sand bonds in dune soil, increasing the proportion of moderately and hard-to-erode particles (up to 70%), shear strength by 0.14%～13.07%, and erosion resistance by 0.6%～2.2%. Freezing can effectively improve the corrosion resistance of sand dune soil and inhibit wind erosion. The research results can provide a theoretical basis for the wind erosion resistance of dune wind erosion '' bare spot '' in freezing period.
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Macro-micro evolution characteristic function of stabilized-loessunder dry-wet cycle effects
Abstract:
Dry-wet cycles significantly impact the stability of loess slopes. To understand the durability of stabilized-loess slope protection materials under dry-wet cycles, experiments on direct shear, permeability, and microscopic properties were conducted. Macroscopic properties evolution and microscopic structural damage were studied, leading to the establishment of characteristic functions describing the relationship between macroscopic and microscopic properties. Results showed that biopolymer content mitigated mechanical property deterioration in stabilized-loess, with its effectiveness positively correlated to dosage. Biopolymer content also influenced permeability changes, inversely proportional to dosage. Dry-wet cycles led to loess cementation failure, particle damage, and pore enlargement, mitigated by biopolymer which delayed damage and altered pore development. Prediction accuracy of characteristic functions exceeded 95%, highlighting porosity and large pores (>32μm) as significant factors impacting mechanical properties and permeability, respectively.
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Study on Landscape Ecological Security Assessment and Zoning Management of Karst Mountainous Landscape in Southwest China
Abstract:
Wenshan City, situated in the southwest of China, exhibits a typical karst mountain terrain. It constitutes a crucial ecological function area in China, featuring a fragile ecological environment and a high susceptibility to ecological variations. Grounded on the attributes of the karst mountain landscape, this paper has erected a target-comprehensive-project-index assessment index system for landscape ecological security. By employing the geometric mean and the InVEST model, the ecological sensitivity and significance of system services were appraised at two comprehensive levels. Subsequently, the ecological security target level was evaluated, ecological functional zones were demarcated, and differentiated management measures were proffered. The findings suggest that: (1) The regions highly susceptible to soil erosion, geological disasters, and rocky desertification are predominantly distributed in the eastern and southern areas; Water conservation, soil conservation, and biodiversity conservation were generally inadequate, and the regions of greater significance were mainly situated in the southwest. (2) The outcomes of the integrated ecological sensitivity and significance of system services disclosed that the ecological quality of the southwest region surpassed that of other regions; The overall level of landscape ecological security is low, with a general tendency of being high in the southwest, low in the east and south, and mediocre in the north. (3) The ecological function zone of Wenshan City was categorized into four types of ecological function zones, namely the rock desertification ecological function restoration zone, the urban ecological coordination construction zone, the biodiversity functional protection zone, and the water conservation and soil conservation function enhancement zone. Rational management measures and suggestions were advanced based on the ecological predicaments of each region.
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Analysis of Soil Erosion Intensity Change Trajectories and Their Driving Factors in Yunnan Province Based on an Improved Stability Mapping Method
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[Objective] This study aims to elucidate the change trajectories of soil erosion intensity in Yunnan Province from 1990 to 2022, analyze the types of changes and their driving factors, and provide a scientific foundation for effective soil erosion control strategies. [Methods] Quantitatively assess soil erosion intensity conditions in Yunnan Province based on the RUSLE model and capture dynamic characteristics by introducing interannual change rates. Use an improved Stability Mapping Method (STD), combining change rates and frequencies to identify soil erosion intensity change trajectory types. Analyze the contribution of driving factors using the Random Forest model and compare the characteristics of driving factors across different trajectory types. [Results] The interannual change trend of soil erosion in Yunnan Province was mainly stable, with significant changes observed in areas of substantial decrease and increase. Soil erosion intensity change trajectories exhibited significant spatial differentiation, with cyclical trajectories being the most prevalent (53.90%), followed by non-continuous stepwise (14.78%) and fluctuating types (14.08%). Precipitation, slope, population density, GDP, and vegetation cover were the main driving factors affecting soil erosion intensity trajectory changes, with contributions of 17.92%, 14.56%, 12.52%, 12.67%, and 9.41%, respectively. There were differences in driving factors across different trajectory types. Areas with cyclical and non-continuous stepwise trajectories had higher precipitation and slopes, while stepwise trajectory areas had higher farmland coverage and lower forest coverage. [Conclusion] The characteristics of soil erosion intensity trajectory changes in Yunnan Province are significant, with spatial heterogeneity in driving mechanisms. Therefore, soil erosion control strategies should reflect regional differentiation and specificity, and adopt location-specific measures based on regional characteristics. The STD trajectory partitioning method based on change rates effectively captures the dynamic changes in soil erosion, providing new insights for monitoring, early warning, and partitioned control of soil erosion.
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Greenhouse Gas Mitigation and Yield Response to Biochar-Microbial Amendment in Saline Soil
Abstract:
To investigate the effects of combined application of biochar and microbial fertilizer on greenhouse gas emissions and sunflower yield in saline-alkali soil under plastic film mulching and drip irrigation. Field experiments were conducted in saline-alkali soil in the Hetao Irrigation Area of Inner Mongolia, with different combinations of biochar (0, 7.5, 15 t/hm2) and microbial fertilizer (0, 112.5, 225 kg/hm2). Greenhouse gas emissions were monitored using static chamber-gas chromatography method. Changes in soil physicochemical properties, global warming potential (GWP), and sunflower yield were analyzed. The results showed that: (1) Compared with the control treatment (0 t/hm2 biochar + 0 kg/hm2 microbial fertilizer), the treatment of 7.5 t/hm2 biochar + 225 kg/hm2 microbial fertilizer increased soil organic carbon, available phosphorus, and available potassium contents by 63.9%, 155.7%, and 46.8%, respectively. (2) Compared to the control treatment, the treatment with 7.5 t/hm2 biochar + 225 kg/hm2 microbial fertilizer reduced cumulative CO2 emissions from 4373 kg/hm2 to -394.3 kg/hm2, increased cumulative CH4 emissions from -0.08 kg/hm2 to 0.1 kg/hm2, reduced cumulative N2O emissions from 0.23 kg/hm2 to -0.09 kg/hm2, and decreased GWP from 4438.3 kg/hm2 to -417.2 kg/hm2. (3) Under the treatment of 15 t/hm2 biochar + 225 kg/hm2 microbial fertilizer, sunflower yield reached 4137.5 kg/hm2, increased by 39.4% compared with the control treatment (2968 kg/hm2). (4) Mantel test analysis revealed that sunflower yield was extremely significantly correlated with soil physicochemical properties (p < 0.01); CO2 emissions were significantly correlated with ammonium nitrogen and moisture content, N2O emissions were significantly correlated with nitrate nitrogen, and CH4 emissions were extremely significantly correlated with nitrate nitrogen (p < 0.05). The combined application of biochar and microbial fertilizer can simultaneously improve saline-alkali soil, reduce greenhouse gas emissions, and increase sunflower yield, with 7.5 t/hm2 biochar + 225 kg/hm2 microbial fertilizer being the optimal combination. This technique provides a new strategy for reducing greenhouse gas emissions and increasing crop yields in saline-alkali agricultural production.
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Soil Quality Assessment of Five Typical Forest Stands in the Dianchi Lake Basin Based on MDS
jinzhehao, Liu Zhiqin, Wang Keqin
Abstract:
Soil quality is a critical indicator of ecosystem health and sustainable land management. The Dianchi Lake watershed, as a key ecological area in the southern plateau of China, has recently faced threats to soil quality due to changes in land use practices. This study aims to assess the soil quality of five typical land use types in the watershed and investigate the effects of different vegetation types on soil physicochemical properties. The minimal dataset method (MDS) and principal component analysis (PCA) were employed to process the data and identify key soil quality indicators.The results indicate that: (1) A comparative analysis of the physicochemical properties of soils in five typical forest types in the Dianchi Lake watershed revealed that the soil quality of mixed forests, pure forests of Chinese pine, and pure forests of Eucalyptus deglupta significantly surpassed that of artificial eucalyptus forests. The mixed forest exhibited higher organic matter and total nitrogen content, while the Eucalyptus deglupta forest demonstrated strong water retention capacity. The pure Chinese pine forest performed well in nutrient supply and fertility maintenance. The soil quality of shrub forests was intermediate, with zmoderate levels of organic matter and total nitrogen. (2) The MDS was used to evaluate the soil quality index (SQI) across three soil layers for different forest types. Results showed that the SQI was highest in the pure Chinese pine forest at the 0-20 cm layer, in the Eucalyptus deglupta forest at the 20-40 cm layer, and in both the Eucalyptus deglupta and mixed forests at the 40-60 cm layer. The average SQI values were as follows: Eucalyptus deglupta (0.60) > Chinese pine (0.54) > mixed forest (0.47) > shrub forest (0.33) > artificial eucalyptus (0.20). (3) The MDS analysis demonstrated a strong correlation with the total dataset (TDS), with a fitting performance of R2 = 0.69, confirming the effectiveness of MDS in soil quality assessment.The findings provide a scientific basis for soil management in the Dianchi Lake watershed, recommending the promotion of Eucalyptus deglupta mixed planting in water conservation areas and regions severely affected by soil degradation to maintain soil organic matter and improve water retention capacity. Additionally, it is suggested to implement mixed planting and rational irrigation measures for artificial eucalyptus forests to restore soil quality, while enhancing the coverage and soil conservation capacity of shrub forests to sustain soil fertility and ecological functions.
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Multi scenario simulation of land use and carbon stock assessment in the Pearl River Basin in the next decade
Abstract:
[Objective]The temporal and spatial changes of land use and carbon storage in the Pearl River Basin in the past 20 years and the next 10 years were analyzed, in order to provide a reference for the optimization of land use pattern and ecosystem carbon sequestration management in the Pearl River Basin. [Methods]Based on the land use data of 2002, 2012 and 2022, this paper analyzes the changes of land use types, uses the PLUS model to simulate the land use pattern under the natural development scenario, cultivated land protection scenario and ecological protection scenario in 2032, and uses the InVEST model to evaluate the changes of ecosystem carbon storage under the three scenarios. [Results]The results show that the land types in the Pearl River Basin have changed greatly in the past 20 years, and the one-way conversion of cultivated land to construction land and the two-way conversion between cultivated land and forest land are the main characteristics of land use change in the Pearl River Basin. During the same period, the carbon storage of terrestrial ecosystems showed a downward trend as a whole, with a decrease of 0.52%. The carbon storage projection in 2032 shows that the carbon storage under the ecological protection scenario is significantly higher than that under the cultivated land protection scenario and the natural development scenario, which are4.84×106 ton和10.22×106ton higher, respectively. [Conclusion]Therefore, when formulating land use planning in the future, decision-makers should consider the balance between economic development and ecological protection, strengthen the concept of ecological protection and green development in river basins, increase the function of land carbon storage, and help achieve the "double carbon" goal and regional sustainable development.
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The Effect of Wind Speed on the Characteristics of Rill Erosion on Windward Slope under Rainfall Conditions
Abstract:
[Objective]To elucidate wind-induced rill erosion characteristics on the windward slope, artificial simulated wind-driven rain experiments were conducted.[Methods] The study investigated changes in water and sediment processes as well as rill morphology under different wind speed conditions (0, 3, 5, and 7 m/s).[Results] Results indicated that, compared to slopes without wind, the windward slope exhibited a 20.59%～47.06% increase in flow generation time and a 33.10%～137.78% increase in the occurrence of falling ridges. The average slope flow velocity decreased by 12.86%～22.53%. Runoff and sediment production rates notably decreased with increasing wind speed(p<0.05).The runoff production rate on windward slopes followed a similar trend under different wind speeds, gradually increasing with rainfall before stabilizing over time, with no significant differences observed among stages at different wind speeds. Sediment yield rates increased rapidly with prolonged rainfall duration, followed by a gradual decrease and stabilization. Nodes of sediment yield rate changes aligned closely with the occurrence of falling ridges.Rill dimensions (width, depth, fluctuation degree) decreased with rising wind speed. The width-depth ratio and rill inclination ranged from 1.4 to 1.69 and 13.47 to 14.76 degrees, respectively, increasing with higher wind speeds. Under various wind speed conditions, rill volume, splitting degree, and density ranged from 4.39 to 10.27 m3, 0.024 to 0.042, and 2.03 to 2.92 m/m2, respectively, all decreasing with increasing wind speed.[Conclusion]The volume, density, and degree of fragmentation of rills are all significantly positively correlated with the amount of slope erosion, making them the preferred indicators for characterizing the morphology of rills on windward slopes.
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Spatial and temporal variation and potential of NPP in terrestrial ecosystems in Shaanxi Province from 2000 to 2020
Abstract:
In the context of the "dual- carbon" goal, accurately assessing the status, rate and potential of carbon sequestration in terrestrial ecosystems is crucial for achieving “carbon neutrality”. Shaanxi province, which spans three climatic zones and have a large difference in climate between north and south, with abundant vegetation types. In recent years, the vegetation coverage in Shaanxi has been further improved due to the implementation of various ecological projects (Grain for Green, Three-North Shelterbelt, etc.). Its vegetation coverage reach up to 60.7%, what resulted in huge carbon sequestration capacity. Net primary productivity (NPP), as one of the most important indicator to reflect the carbon sequestration capacity of vegetation, there are few studies on spatial and temporal dynamic changes of NPP and the spatial distribution of NPP potential in the future in Shaanxi Province. Based on these, we evaluated the temporal and spatial distribution characteristics of vegetation NPP and its potential in Shaanxi Province through CASA model and neighborhood similarity spatial distribution method. The results showed that: (1) Total carbon sequestration by vegetation increased by 333Tg, with an increase of 48.5% from 2000 to 2020 in Shaanxi Province. (2) NPP was higher in the south and lower in the north, with the highest or lowest value in the middle. The average value in 2000 and 2020 were 333.2 g C/m2 and 494.8 g C/m2, respectively, with a total increasement of 161.6 gC/m2, and the increase amplitude shows a distribution trend of high in the north and low in the south in Shaanxi. (3) The carbon sequestration potential was 2304 Tg which increased by 41.30% compared with the 2020. The spatial distribution trend is gradually decreasing from south to north, and the spatial distribution characteristics show high spatial autocorrelation characteristics, but the local differences are large. This study calculated the spatial and temporal dynamic changes and predicted potential spatial distribution characteristics of NPP in the regional scale ecosystem in Shaanxi, which can provide a evaluation systematic and theoretical reference for scientific evaluation and improvement of regional carbon sink capacity.
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Identification of key areas for ecological restoration and division of restoration zones in Qinghai Province
Abstract:
[Objective] Identifying priority spaces for ecological restoration and curbing ecological degradation based on the governance idea of "holistic protection, systematic restoration and comprehensive management" is an important measure for the coordinated development of regional socio-economics, the construction of a firm ecological security barrier and the promotion of ecological civilization.[Methods] This paper takes Qinghai Province as the study area, reflects the urbanisation process through land use intensity and land use centre of gravity shift, quantitatively evaluates seven ecosystem services, ecological sensitivity and habitat degradation from 2005 to 2020, and proposes to identify the priority space for ecological restoration based on the cluster of ecosystem services, ecological sensitivity and habitat degradation. We proposed to identify ecological restoration priority spaces based on "ecosystem service cluster, ecological sensitivity and habitat degradation degree", and combined internal defects and external coercion to delineate five types of ecological restoration priority zones and propose corresponding restoration strategies.[Results] The depth of water production in Qinghai Province from 2005 to 2020 will be 125.1 mm, 106.9 mm, 80.0 mm and 135.4 mm respectively, and the depth of water retention will be stabilised at about 15 mm. Grain output will increase from 1.42 t/hm2 to 2.02 t/hm2, wind and sand control capacity will increase from 2.42 t/hm2 to 4.59 t/hm2, and soil conservation capacity will decrease from 85.9 t/hm2 to 65.3 t/hm2; The ecosystem service clusters in Qinghai Province were classified into five categories: Harmony of Habitat, Harmony of Soil and Water, Conservation of Ecological Sources, Restoration of Natural Ecology, and Functional Cluster of Wind and Sand Conservation. Based on the results of bivariate autocorrelation to identify the ecological restoration priority points, it can be seen that the key ecological restoration points and natural ecological restoration points are the main ones in Qinghai Province, accounting for 5.26% and 2.55% of the area, respectively, in which the key ecological restoration points and ecological livability clusters increase the area of the spatial distribution of the basic coincides with each other.[Conclusion] The priority areas for ecological restoration in Qinghai Province are concentrated in the ecologically fragile northwestern desert areas, high-altitude mountainous areas, water sources and river coasts and the river valley where human activities are more frequent, and in the area around Tianjun County and Xinghai-Mado-Qumalai County.
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Spatial and temporal variation characteristics of vegetation greenness in rocky desertification and non-rocky desertification areas of Chongqing
Abstract:
The investigation of temporal and spatial variations in vegetation greenness and its response to different land use types in karst rocky desertification and non-rocky desertification areas in Chongqing is crucial for guiding ecological restoration efforts in karst regions. This study utilizes vegetation leaf area index (LAI) data and land use type information to conduct trend analysis and Hurest index calculations, aiming to analyze the temporal and spatial evolution characteristics of vegetation greenness in both rocky desertification and non-rocky desertification areas. Additionally, a land use transfer matrix is employed to quantitatively assess the impact of land use changes on vegetation greenness. The findings reveal that: (1) Vegetation greenness exhibits an increasing trend in both rocky desertification and non-rocky desertification areas, reaching maximum values of 1.36 and 1.69 respectively, with average annual growth rates of 0.014 and 0.012. (2) The dynamic changes observed in vegetation greenness within these areas demonstrate positive trends, with improvement trends accounting for 86.84% (rocky desertification)and87 .04%(non-rock ydesertificatio n). Furthermore, anti-continuous improvement trends are observed at rates of52 .82%(rock ydesertifi cation)a nd80 .29%(non-ro ckyde serti fication), indicating the primary change trajectory for future vegetation greenness. (3) The main land use types in both rocky and non-rocky desertification areas are woodland and cropland, and cropland converted from woodland is the main occurrence of degradation of vegetation greenness, while woodland converted from cropland, shrubs and grassland is the main occurrence of improvement of vegetation greenness. (4) The conversion of land use types with high Leaf Area Index (LAI) to those with low LAI resulted in a decrease in LAI and vegetation greenness, while the conversion from low LAI land use types to high LAI land use types led to an increase in LAI. In areas affected by stony desertification and non-stony desertification, the maximum reduction in total LAI transfer was 1.19×104 and 4,442.18 respectively, whereas the maximum increase was 1.50×104 and 1.71×104 respectively. The impact on total LAI from construction land, water area, and bare land area was minimal and not significant. These research findings contribute to understanding the change characteristics of vegetation greenness and its response mechanism towards land use changes in ecologically fragile areas. Furthermore, they provide a scientific basis for controlling rock desertification, ensuring ecological security, and promoting sustainable economic development in karst areas of Chongqing.
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Comparison of erosion monitoring methods in the Pisha sandstone areas of the Chinese Loess Plateau based on UAV-SfM data
Abstract:
Detection of soil erosion in complex terrain and steep slopes has always been a challenge. The 3D point clouds achieved by the Unmanned Aerial Vehicle-Structure from Motion (UAV-SfM) technology provides an efficient and cost-effective method for obtaining large-scale terrain data, making it an important data source for monitoring land surface changes. However, there is a lack of comprehensive research on UAV-SfM terrain change monitoring algorithms, limiting its application in the study of soil erosion and sediment transport processes. This study assessed the accuracy of four commonly used geomorphic change detection algorithms in the Pisha sandstone area of the Loess Plateau, including Digital Elevation Model of Difference (DoD), Cloud to Cloud (C2C), Cloud to Mesh (C2M), and Multiscale Model to Model Cloud Comparison (M3C2). . Point cloud data employed to operate the four algorithms were produced using the SfM technique based on images acquired by UAV between July 2022 and March 2023. The impact of point density changes in the accuracy of the employed algorithms was also investigated. Results showed that all four algorithms were capable of effectively monitoring large surface changes. Among them, the M3C2 algorithm performed the best with the highest accuracy (R2 = 0.953, p <0.01) and the lowest error (MAE = 0.0161m, MRE = 3.37%, RMSE = 0.0194m), followed by the C2M algorithm. The DoD algorithm was only suitable for flat areas and yielded overestimated results for steep sloping areas. The M3C2 and C2C algorithms were sensitive to point cloud density, while the C2M and DoD algorithms were lesssensitive. The study provided a useful reference for the selection of erosion monitoring methods for the Pisha sandstone areas.
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Influence of Headcut Height on the Developmental Processes of Downstream Plunge Pool on a Granite Red Soil Slope
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The development of plunge pool is a key process of headcut erosion. To clarify the effect of headcut height on the developmental processes and dynamical mechanisms of plunge pool. The study investigated the developmental processes and dynamical mechanisms of plunge pool under different headcut heights (25 cm, 50 cm, 75 cm, 100 cm, and 125 cm) on a granite red loam slope. The results show that: (1) As the height of the headcut increases, the Re, τ, ω and the jet parameters: Vbottom, , Ekbottom, and show an increasing trend. (2) After the laterite soil layer scouring to form a "V" type of small plunge pool mainly, with the increase in the flow of the form of plunge pool gradually increased, but it is difficult to form a large area of the plunge pool, and the laterite soil layer is more stable than the sandy soil layer. During the scouring process of the sandy soil layer, the development of headcut bed drop points was more obvious, and when the flow rate increased to 120 L/min, the degree of headcut bed fragmentation was gradually drastic, and the outline of the drop points was gradually clearer, and the cross-sectional area increased (3) The study characterizes the degree of erosion of drop caves through cross-sectional area. Random forest algorithm and Shapley values are used to construct the model and characterize the relationship between the parameters. The results showed that in the laterite layer, Fr, ω, Ekbrink, and Re were negatively correlated with the cross-sectional area; and in the sandy soil layer, Fr and were negatively correlated with the cross-sectional area. Higher accuracy of predictive models constructed by the random forest algorithm (LCCC=1.02, R2adjusted=0.876 and 0.868). The study provides a theoretical basis for revealing the mechanism of plunge pool development, improving the theoretical system of gully erosion, and preventing and controlling soil erosion in the red soil area.
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Effect of Rock Strata Dip on Soil Detachment Capacity of Different Land Use Types in karst Trough Valley Area
Abstract:
Abstract: [Objective] This study aims to explore the influence mechanism of rock strata dip on soil erodibility in karst gorge areas, and provide reference for preventing and controlling water and soil erosion in karst trough valley area. [Methods] The study focuses on the dip/anti-dip slope of Qingmuguan karst trough valley area in Chongqing City. Through flume erosion experiments, we analyze the differences in soil erodibility between different land use types on dip/anti-dip slopes, and investigate the impact of soil physicochemical properties on soil erodibility.[Results] (1) Both dip/anti-dip slopes shows a significant negative correlation with organic matter content, >0.25 mm water-stable aggregates content, and total nitrogen content (P<0.05). In particular, anti-dip slope have higher organic matter content, >0.25 mm water-stable aggregates content, and total nitrogen compared to dip slope. (2) Soil erodibility is higher on dip slope than anti-dip slope for all four land use types studied. Additionally, grassland has lower comprehensive scores of soil erodibility than pepper fields, cornfields, and bare land on both dip/anti-dip slopes. (3) Based on stepwise multiple regression analysis results, prediction models for soil erodibility on dip/anti-dip slopes were established using organic matter content and >0.25 mm water-stable aggregates content as predictors with determination coefficients R2 of 0.77 and 0.85 respectively.[Conclusion] In summary, grassland has the lowest soil erodibility among all land use types studied regardless of dip/anti-dip slopes in karst trough valley. Therefore, in order to prevent soil erosion and promote ecological restoration in karst trough valley, it is necessary to cultivate the land reasonably and increase grassland coverage appropriately, thus enhancing the soil''s resistance against erosion.
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Transformation of Chemical Forms and Migration Characteristics of Cadmium and Selenium During Soil Formation on Black Rock Series
Abstract:
Black rock series contains high amounts of cadmium and selenium. During weathering and soil formation on the rocks, the chemical form transformation and release of cadmium and selenium from the rocks can have an impact on the surrounding ecological environment. In this study, a black rock series distribution area of Hetang formation of the Lower Cambrian was selected in Northwest Zhejiang. By collecting horizonal soil samples from soil profiles along different parts of the terrain (hill upslope, hill middle slope, hill downslope, inter hill valley bottom and valley terrace), the quantity and chemical form transformation patterns of cadmium and selenium during the process of weathering soil formation and weathering material migration of the black rock series were discussed. The results showed that total cadmium and total selenium in the soils decreased from parent rock to soil. The loss of cadmium and selenium in the weathered matter of black rock series increased with the increase of transportation distance along the hilly slope, and the loss of cadmium and selenium in the process of evolution from slope deposit to diluvium was greater than that from residual to slope deposit. The cadmium and selenium lost from the weathered materials could affect the content of cadmium and selenium in the topsoil derived from the alluvial of the downstream river in the way of water diffusion, but the degree of influence decreased with the increase of distance. With the increase of the transportation distance of weathered materials and the evolution of soil, the transformation of carbonate bound cadmium and residual cadmium to water-soluble cadmium, exchangeable cadmium, organic matter bound cadmium and oxide bound cadmium occurred. The residual selenium was gradually activated and transformed into exchangeable selenium, organic matter bound selenium and oxide bound selenium. The results also showed that soil water-soluble cadmium, exchangeable cadmium (selenium) and organic matter bound cadmium (selenium) increased toward the surface. The organic enrichment of selenium and topsoil was more obvious than that of cadmium. The results indicates that the weathering of black rock series could not only directly affect the content of soil cadmium and selenium in its distribution area through residue, but also affect the content of soil cadmium and selenium in the surrounding area through water diffusion.
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Spatial Variation Characteristics and Influencing Factors of Black Soil Quality in Typical Water-Eroded Sloping Croplands
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[Objective] To clarity the role of sedimentation and erosion in shaping the spatial pattern of soil quality in black soil slope croplands, this study focused on a typical water erosion area in Northeast China. [Methods]The research aimed to evaluate the spatial characteristics of soil quality at the slope scale by using soil attributes from 110 sample points. The assessment utilized the Soil Quality Index (SQI) based on a minimum dataset, while the effects of slope gradient, slope position, and soil depth were determined using Generalized Linear Models (GLMs). [Results] The findings are as follows: (1) Opposing patterns of soil nutrient content and spatial characteristics were observed between the surface and subsurface layers in sloping croplands. Most nutrient indicators exhibited significantly higher content in the tillage layer compared to the subsurface layer. However, the surface layer showed lower spatial heterogeneity and weaker correlation with related physicochemical indexes comparing with the subsurface layer (p＜0.05). (2) Erosion and sedimentation significantly influenced the spatial distribution characteristics of soil quality. The SQI was significantly lower in slopes with severe erosion compared to up-slope areas with weakly eroded regions and down-slope areas in depositional areas (p＜0.05). Compared with the upper position, the SQI of middle postion was 26.2% and 31.6% lower at surface and subsurface soil layers, respectively. Sedimentation did not improve the soil quality of severely eroded slope croplands, and there were no significant differences in SQI between down-slope and up-slope areas (p＞0.05). (3) Soil depth, slope position, and slope gradient emerged as key factors influencing the variability of SQI in slope croplands. The GLM results demonstrated that, for the same soil horizon, slope, aspect, and their interactions explained over 95-% variation in SQI. Among them, the explanatory degree of slope position was 68%, and that of slope gradient was 22%. Considering the factor of soil depth, the explanatory degrees of soil depth, slope position, and slope gradient on the variation of SQI in the range of 0-40 cm were 39%, 31%, and 10%, respectively..[Conclusion] In this study, the combined method of SQI and GLM was used to clarify the shaping role of erosion-sedimentation process in the spatial differentiation of black soil quality in sloping cropland, and the research results can provide technical support for the evaluation and management of the quality of eroded degraded black soil in typical water-eroded areas.
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Simulation of Soil Water Storage and Analysis of Influencing Factors in Weihe River Basin under Changing Environment
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With the intensified influence of climate change and human activities, the climate and underlying surface conditions of the basins have changed. Accurately simulating the process of soil moisture change and analyzing its influencing factors are of great significance for regional water resources management and vegetation construction. In this study, the Weihe River Basin in the Loess Plateau was taken as the research object. Based on the ABCD hydrological model, the EFAST method was used to analyze the parameter sensitivity of the model, and the constant parameter and time-varying parameter models were constructed. The runoff depth and soil water storage simulation accuracy of different parameter models were compared. The effects of climate change and vegetation restoration on soil water storage changes in the Weihe River Basin were discussed, and the dominant factors of soil water storage changes were clarified. The results show that: 1)The proportional parameter of soil water layer recharge groundwater c is the most sensitive, followed by the groundwater storage coefficient d, the upper limit parameter b of the sum of actual evapotranspiration and soil water storage, and the tendency parameter a of runoff before soil is completely saturated is the least sensitive. 2) Compared with the ABCD constant parameter model, the time-varying parameter model increased the values of NSE, KGE, and R2 of the runoff depth simulation results by 19%, 10%, and 19%, respectively, and the NSE, KGE, and R2 of the verification period increased by 7%, 7%, and 9%, respectively. The time-varying parameter model significantly improved the runoff depth simulation results. 3) The correlation between soil water storage and ERA5-Land 0~100cm soil water storage in Weihe River Basin based on time-varying parameter model simulation is the strongest, and the change process of the two agree well. 4) The degree of different influencing factors on the change of soil water storage in the Weihe River Basin from strong to weak is potential evapotranspiration > precipitation > NDVI. The research results provide scientific basis for water resources planning and management and vegetation construction in this area, and also provide reference for soil water storage research in other similar areas.
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Effects of vegetation restoration patterns on soil water-stable aggregates composition and their stability in the water level fluctuation zone of the Heilongtan Reservoir
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[Objective]In order to elucidate the effects of different vegetation restoration modes on soil water-stable aggregates and stability in the water level fluctuation zone(WLFZ).[Methods]The characteristics of soil water-stable aggregates and their stability indexes were determined and analyzed by the wet sieve method on the soil under artificially and naturally restored vegetation in the WLFZ in the hilly region of central Sichuan Basin.[Results]The content of >0.25 mm water-stable macroaggregates in WLFZ soils was 4.21% lower compared to unflooded area. The soil water stability macroaggregates content decreased by 12.27% under naturally restored vegetation and increased by 3.84% under artificially restored vegetation compared to unflooded area; With the rise of water elevations, the soil water stability macroaggregates content showed an increasing trend, the microaggregates content showed an overall decreasing trend, and the soil aggregate stability gradually increased with the rise of water elevations; The soil water-stable aggregates composition differed significantly (p < 0.05) among the different restoration modes, and the soil water-stable aggregates particle size increased overall under the artificially restored vegetation, in which the content of soil water-stable macroaggregates under the artificially restored vegetation (69.48%) was significantly higher than that of the natural restoration mode (43.20%); Decrease in soil water-stable aggregates stability in WLFZ with increasing flooding time, the values of R0.25, MWD, and GMD in the artificial recovery mode were greater than those in the natural recovery mode, and the values of D, K, and PAD were smaller than those in the natural recovery mode, Soil water-stable aggregates stability and soil erosion resistance were higher in the artificial restoration model than in the natural restoration model.[Conclusion]The soil aggregate stability of WLFZ decreased after inundation, but the artificial restoration mode can effectively improve the soil aggregate structure, and the results of the study can provide a scientific basis for the evaluation of soil structure stability and vegetation restoration of the WLFZ.
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Effects of vegetation community characteristics under different grazing intensities on soil aggregates in Xilamuren grassland
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[Objective] Vegetation community is an important factor affecting soil aggregates. However, the impact of changes in vegetation communities on soil aggregates under grazing pressure is still unclear. [Method] Taking Xilamuren Desert Steppe as the research object, the characteristics of vegetation community and soil aggregates under light grazing (LG), moderate grazing (MG), heavy grazing (HG) and no grazing (CK) and their relationship were analyzed by field investigation and indoor analysis. The effects of plant community changes on soil aggregates were revealed. [Results] (1) The number of plant community species increased with the increase of grazing intensity. The Shamnon-Wiener diversity index (H") and Simpson dominance index (D) of LG community were significantly lower than those of other grazing intensities (P<0.05). The aboveground biomass decreased with the increase of grazing intensity, and the aboveground biomass of HG was significantly lower than that of other grazing intensities (P<0.05). The underground biomass under different grazing intensities was significantly different, and the underground biomass of different soil layers was the highest in LG. (2) The change trend of mean weight diameter (MWD) and geometric mean diameter (GMD) was consistent with the content of macroaggregates. In 0-5 cm and 5-10 cm soil layers, it increased first, then decreased and then increased with the increase of grazing intensity (LG was the highest and MG was the lowest). (3) The community Shamnon-Wiener diversity index (H"), Pielous evenness index (J"), aboveground biomass, bulk density, organic carbon and total nitrogen content were significant factors affecting macroaggregate content, MWD and GMD (P<0.05). [Conclusion] The research results can provide theoretical support and scientific basis for rational grazing and ecological restoration in Xilamuren grassland.
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Response of Soil detachment capacity of Citrus Orchard Covered with Green Fertilizer to Concentrated Hydrodynamic Parameters
Abstract:
[Objective]To explore the relationship between the soil detachment capacity of green manure cover and the hydraulic characteristics of concentrated water flow in typical sloping orange orchards in the Three Gorges Reservoir area, so as to provide data support for further clarifying the hydraulic characteristics of land upflow in typical sloping orange orchards during soil erosion. [Methods]Through the concentrated flow erosion test, the soil detachment capacity between bare slope and green manure (Trifolium repens, Poa annuaL, and Vicia sepium L) under the gradient hydrodynamic conditions of different slopes (10°~25°) and flow (18~126L/min) was analyzed, and the soil detachment capacity and water flow dynamic parameters (water flow shear force, water flow power), flow pattern parameters (Reynolds number, Freud number), and resistance parameters (Darcy-Weisbach resistance coefficient, Manning coefficient) and establish a corresponding mathematical model. [Results]The results showed that green manure mulching could significantly reduce soil soil detachment ability (P < 0.01). The soil detachment capacity of bare slope and green manure cover was positively correlated with the parameters of water flow dynamics and flow pattern (P < 0.05), and negatively correlated with the parameters of water flow resistance (P < 0.05). The prediction effect of water flow shear force on soil detachment capacity is better than that of water flow power. The Reynolds number predicts soil detachment capacity better than the Freud number. The prediction of the Darcy-Weisbach drag coefficient is better than that of the Manning coefficient. Overall, the shear force of water flow had the best effect in predicting soil detachment ability and had the highest accuracy (R2=0.957, NSE=0.963).
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Effects of Grazing Intensity on Soil Microbial Community Characteristics in Desert Steppe
Abstract:
Abstract： [Objective] Investigating the response mechanism of soil microbial communities to changes in grazing intensity can provide scientific theoretical and technical support for ecological protection and restoration of desert steppe. [Methods] Taking the desert steppe in Inner Mongolia as the research object, we studied the effects of different grazing intensities (no grazing, light grazing, medium grazing, high grazing) on soil physicochemical properties and the composition and diversity of soil microbial communities at different soil depths (0-20 cm and 20-40 cm), The interactions between soil physicochemical properties and soil microbial communities were analyzed. [Results] The results showed that, compared to no grazing, medium grazing significantly (p<0.05) reduced the soil total nitrogen (TN) content (by 17.99%) and soil organic carbon (TOC) content (by 19.23%) at 0-20cm depth. The maximum value of soil bulk density (SBD) appeared under high grazing conditions. The soil physicochemical properties at 20-40cm depth showed no differences (p>0.05) under different grazing intensities. In addition, grazing decreased the abundance and diversity of bacterial communities at 20-40cm depth, while increased the abundance and diversity of bacteria communities at 20-40cm depth. Under light and moderate grazing conditions, the abundance and diversity of soil fungal communities at 0-20cm depth increased, with no significant effect (p>0.05) on the abundance and diversity of soil fungal communities at 20—40cm depth. [Conclusion] Mantel tests showed that total nitrogen of desert steppe soil is the primary factor influencing the change of desert steppe soil bacterial abundance with grazing intensity. The research results contribute to understanding the ecological sensitivity of soil microbes and offer scientific guidance for achieving sustainable management in desert steppe ecosystems.
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Optimization of Water And Nitrogen Regimes Based on AquaCrop Model for Drip Irrigation Cotton under Nitrogen-reducing Conditions in The Northern Border Region
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[Objective] To optimize the nitrogen application system for drip irrigation cotton under reduced nitrogen fertilization. [Methods] Sampling field experiment and AquaCrop model were combined to carry out the study. [The results showed that the highest cotton yields of 5.496×103kg·hm2 and 5.126×103kg·hm2 were obtained from W2Nck (10% reduction in irrigation with normal N application) or W1Nck (10% increase in irrigation with normal N application) treatments, and the highest yields of 5.496 t·hm2 and 5.126 t·hm2 were obtained from W2N1 (10% reduction in irrigation with 30% reduction in N application) or W1N1 (10% increase in irrigation with 30% reduction in N application). 10% paired with 30% reduction in N application) treatments had the lowest cotton yields of 3.933×103kg·hm2 and 3.625×103kg·hm2, and the combined effect of water and nitrogen stresses negatively affected cotton yields; compared with single measures, increasing or decreasing the irrigation volume at normal nitrogen application levels could result in a yield-increasing effect; appropriately decreasing the irrigation volume or increasing the nitrogen application was more conducive to increasing the water use efficiency and reduce nitrogen residue in the soil. The AquaCrop model was calibrated with two years of experimental data, and the calibrated parameters were used to simulate cotton yield and water and nitrogen utilization under 300-600 mm irrigation quota under nitrogen reduction conditions 0.94; biomass evaluation index R2>0.947, NRMSE<40.58, ENS>0.72, yield evaluation index R2>0.91, NRMSE<4.29%, ENS>0.85; and water use efficiency evaluation index R2>0.87, NRMSE<4.22%, ENS>0.81, which indicated that the AquaCrop model had a better effect on the water-nitrogen treatment in cotton fields has good applicability. [Conclusion] Model simulation of 240 nitrogen and irrigation combinations, combined with the analysis of yield, water use efficiency and nitrogen bias productivity indexes, the combination of 10% nitrogen reduction and 360 mm irrigation quota can be used as a preferred solution to achieve stable yield and reduce economic costs under efficient water and nitrogen utilization. The optimization of cotton irrigation and nitrogen application system under the premise of stable yield of cotton under drip irrigation under membrane in Northern Xinjiang can be used as a reference basis for improving water and nitrogen utilization efficiency during cotton cultivation in arid areas.
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Effects of aeration on tomato growth and soil enzyme activity under the condition of topdressing fertilizer reduction
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[Objective]To explore the effects of aeration on crop growth characteristics and soil environmental characteristics in rootzone under reduced topdressing conditions. [Methods]the present paper takes the field cultivated tomato in Yinbei irrigation area of Ningxia as the research object. Four groups of micro-nano gas aeration ratios (0%, 5%, 10%, 15%) and three topdressing (urea-triple superphosphate-potassium sulfate) levels (180-400-480 kg/hm2, 135-300-360 kg/hm2, 90-200-240 kg/hm2) were set up for the two-year field experiment conducted in 2019 and 2020. [Results]The results showed that with the same topdressing level, the dry matter and nutritional elements (N, P, K) accumulation in the plant increased with the increase of aeration ratio, and increasing the aeration ratio was beneficial to the accumulation of phosphorus in roots during flowering-fruit setting period and the potassium accumulation at fruit expansion stage. With the same topdressing level, the tomato yield increased by 14 %-44.2 % as the aeration ratio increased by 5%-15%. With the same aeration ratio, the tomato yield increased by 0.4%-9.1% as the topdressing level was appropriately reduced (-25%) compared with the traditional fertilization. The increase of the aeration ratio and topdressing level was beneficial to increase the soil enzymes (catalase, alkaline phosphatase and urease) activity significantly during the flowering-fruit setting period and fruit enlargement period of tomato. With the same topdressing level, increasing the aeration ratio by 5%-15% corresponded to an increase of the soil enzyme activity by 27.5%-122.9%. [Conclusion]It was suggested that, to promote tomato plant growth, stabilize tomato yield and improve the soil enzymes activity in the Yinbei irrigation district, the suitable topdressing level of “urea-triple superphosphate-potassium” was 135-300-360 kg/hm2 (25% lower than the traditional topdressing amount), and the suitable micro-nano aeration ratio was 10%.
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Accuracy assessment of multi-source land use products in the loess hilly and gully region
Abstract:
Evaluating the accuracy of multi-source land use products is essential for obtaining reliable surface information, supporting land planning and management, and promoting regional ecological protection and high-quality development. However, the capability of existing land use products to accurately depict the surface cover characteristics in complex terrains or fragmented habitats, such as the loess plateau hilly and gully regions, remains uncertain. Taking the Guanchuan River Basin, a secondary tributary of the Yellow River, as an example, this study assessed the accuracy of six land use products with spatial resolutions of 10 m and 30 m (WorldCover 10 m, ESRI 10m, GLC_FCS30-2020, GlobleLand30, CNLUCC, and CLCD) in the loess hilly and gully region using high-precision GCLUCC land use data. This GCLUCC data, with an overall accuracy exceeding 95%, was derived from GF-2 (0.8m), DEM (5m), and 6400 field sampling points, employing the object-oriented method and manual visual interpretation. The evaluation results showed that (i) In terms of classification characteristics, most products could extract main land categories, yet significant differences existed in extraction efficiency and accuracy, especially regarding the spatial distribution of terraced fields, forest lands, and construction lands; (ii) For area consistency, there were significant discrepancies in land category areas between various products and GCLUCC. For instance, the grassland area in some products was more than twice that of GCLUCC, while forest and water areas accounted for only 0.13%-12.11% and 1.03%-5.86% of GCLUCC, respectively; (iii) In terms of overall accuracy, GlobleLand30 and WorldCover 10m demonstrated relatively higher accuracy, reaching 58.21% and 50.19%, respectively. The accuracy of CLCD and CNLUCC was comparatively lower, with notable classification confusion between forests and grasslands, terraced fields and grasslands, and construction lands and terraced fields; (iv) Significant spatial discrepancies existed between various products and the actual ground surface, particularly in accurately classifying forests, shrubs, bare land, and water bodies. In conclusion, current land use products still face notable challenges in precisely describing surface cover characteristics in the loess plateau hilly and gully regions. Future product development should place greater emphasis on topographical and geographical features and strengthen the recognition of specific land use types like forests, shrubs, bare land, and water bodies to enhance data accuracy and decision-making reliability.
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Impacts of Rainfall Characteristics and Vegetation Cover Patterns on Hillslope Runoff and Sediment Yields in the Three Gorges Reservoir Area
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[Objectives] The Three Gorges Reservoir area is an important ecological barrier in the upper reaches of the Yangtze River and a national key area for soil and water erosion control. With the implementation of major ecological restoration projects, the effectiveness of vegetation construction has been obvious, but the water regulation and soil conservation effects of restored vegetation lack in situ observation and quantitative research. The prominent contradiction between man and land and the development of rural industries have put forward new demands for the optimal utilization of understory land resources, and their impact on the water conservation and soil erosion control functions is not yet clear. [Methods] Taking a typical fallow forest in the Three Gorges Reservoir Area as the research object, four runoff plots with full-slope herbaceous cover (QF), upper-slope bare ground + lower-slope herbaceous cover (XF), equidistant herbaceous strip cover (TF), and full-slope herbless coverage (WF), were set up to carry out field observation of slope runoff and sand production in 24 erosive rainfall events and to identify the effects of erosive rainfall and vegetation cover patterns on hillslope runoff and sediment yields. [Results] The results show that:(1) The 24 erosive rainfall events were classified into three categories, including A-type (small rainfall, heavy rainfall intensity, and short duration), B-type (large rainfall, heavy rainfall intensity, and short duration), and C-type (small rainfall, light rainfall intensity, and long duration). A-type is the rain type with the highest frequency, with a frequency of 45.83%. The cumulative rainfall of B-type is the largest, accounting for 63.44% of the total rainfall. (2) The cumulative runoff depth and cumulative erosion volume of the four vegetation cover patterns generally showed QF
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Analysis on The Spatial and Temporal Changes and Driving Mechanism of Cultivated Land Conversion in Central Yunnan Urban Agglomeration From 1990 to 2020
Abstract:
[Objective]By analyzing the evolution path, spatiotemporal variation characteristics, and driving mechanisms of farmland non agriculturalization in the central Yunnan urban agglomeration over the past 30 years, theoretical basis is provided for the protection and precise management of farmland resources in the central Yunnan urban agglomeration.[Methods] Based on the land use data and statistical yearbook data of the Central Yunnan urban agglomeration, the paper uses methods such as gravity displacement model, change trajectory model, spatial autocorrelation analysis, and principal component analysis to reveal the process and spatial distribution characteristics of farmland conversion to non-agricultural uses in the Central Yunnan urban agglomeration from 1990 to 2020, as well as the main driving factors.[Results] The results indicate that:(1) From a temporal perspective, the non agricultural area of cultivated land in the central Yunnan urban agglomeration has shown a fluctuating downward trend, with the most drastic changes affected by policies, economy, and urbanization around 2000. From a spatial perspective, the non-agricultural conversion of cultivated land is concentrated in the central, eastern, southeastern, and northeastern regions of the central Yunnan urban agglomeration.(2) Over the past three decades, farmland converted to non-agricultural land in the Central Yunnan Urban Agglomeration has tended to be balanced in spatial distribution, with smaller differences in farmland conversion between regions and a stable spatial pattern overall, generally exhibiting a trend of migration to the southwestern region.(3) The main destinations for farmland converted to non-agricultural land in the central Yunnan urban agglomeration are forestland and grassland, with a small portion converted into construction land, mainly in the central, northern, and southeastern parts as well as in some local areas of the northwest.(4) There is a significant spatial clustering effect in the non-agricultural transformation of cultivated land in the central Yunnan urban agglomeration, mainly characterized by high high clustering and low low clustering. High high clustering is mainly distributed in the central, northern, and southeastern regions, while low low clustering is mainly distributed in the northwest, western, and southwestern regions.(5) The non agriculturalization of cultivated land in the central Yunnan urban agglomeration is influenced by both socio-economic and natural conditions. The state-owned fixed asset investment, agricultural population, and urbanization rate are the main driving factors for the non-agricultural expansion of farmland in the social economy, while natural factors such as annual precipitation and temperature play a crucial role in the spatial distribution and expansion process of non-agricultural farmland.[Conclusion] The results have revealed the spatiotemporal change characteristics, evolution path, and driving mechanisms of farmland converted to non-agricultural land in the central Yunnan urban agglomeration over the past 30 years. The research results reveal the spatial and temporal characteristics, evolution path, and driving mechanism of cultivated land conversion in the Central Yunnan Urban Agglomeration over the past 30 years. It plays an important role in rational utilization and protection of arable land resources and ensuring food security in Yunnan Province, and to a certain extent, it can provide decision-making reference for the protection and optimization of arable land layout in the Central Yunnan Urban Agglomeration.
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Analysis of Hydrological Characteristics and Influencing Factors of Typical Lakes in the Qinghai Tibet Plateau from 1985 to 2021
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The lakes of the Tibetan Plateau are important indicators of climate change, and their expansion or contraction also has an important impact on the natural environment of the Tibetan Plateau. Three typical lakes (Qinghai Lake, Yangzhuoyong Lake, and Ulan Ula Lake) located in different climatic sub-zones of the Qinghai-Tibet Plateau were selected and remote sensing monitoring methods were used to study the temporal and spatial variation of the hydrological characteristics of the three typical lakes from 1985 to 2021, reveal the role of key climatic factors, and further explore the influence of glaciers and frozen soil on typical lakes. The results show that the area and water level of Qinghai Lake show a significant upward trend during the study period. The area increased by 238.68km2, the water level increased by 1.32m, and the space showed a trend of expansion in the east-west direction; the area of Yangzhuoyong Lake showed a trend of first fluctuating and then decreasing, decreasing by 16.316km2 and 3.25 meters respectively, and the overall spatial situation showed a shrinking trend from all sides to the center; the area and water level of Ulan Ula Lake showed a significant upward trend, increasing by 125.575km2 and 8.12 meters respectively, and the expansion area was mainly concentrated in the south. The analysis of key climatic factors showed that precipitation change was the key factor affecting the area change of Qinghai Lake and Yanghu Lake, and the area change and precipitation lagged. The main reason for the rise in the water level of Ulan Ula Lake is the seasonal thawing of the frozen soil caused by the increase in temperature. Exploring the changes of lake area on the Qinghai-Tibet Plateau is of great guiding significance for in-depth study of global climate change and surface water resources assessment.
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Effects of organic fertilizers and other nitrogen replacements for chemical fertilizers on growth, yield and water and fertilizer use efficiency of spring maize
Abstract:
To investigate the effects of organic fertilizers and other nitrogen replacements for chemical fertilizers under different nitrogen application rates on the growth, yield and water-fertilizer use efficiency of spring maize in the dry zone of northern Shaanxi, multiple regression analysis and three-dimensional fitting models were used to establishing an optimal nitrogen management model for spring maize cultivation in northern Shaanxi. In this experiment, three nitrogen application levels were (N1: 240 kg/hm2, N2: 180 kg/hm2 and N3: 120 kg/hm2) and five organic fertilizers and other nitrogen replacements for chemical fertilizers ratios were (R0: 100% fertilizer nitrogen, R12.5: 12.5% organic fertilizer nitrogen + 87.5% chemical fertilizer nitrogen, R25: 25% organic fertilizer nitrogen + 75% chemical fertilizer nitrogen, R37.5: 37.5% organic fertilizer N + 62.5% chemical fertilizer N and R50: 50% organic fertilizer N + 50% chemical fertilizer N), a total of 15 treatments. During the main reproductive period of spring maize, spring maize growth and yield and yield components were measured, and water consumption (ET), water use efficiency (WUE), nitrogen fertilizer partial productivity (NPFP) and economic benefits were calculated. The results showed that the ????????????? Logistic function had a high fit for dry matter accumulation in spring maize, the R12.5 treatment delayed the start, the end and the appearance of the maximum value of the period of rapid dry matter accumulation, and the N2 treatment enhanced the maximum daily growth rate of dry matter accumulation. Nitrogen application and replacement ratio significantly affected dry matter accumulation, yield and components, ET, NPFP and economic efficiency of spring maize (P<0.05), and the interaction significantly affected ear length, ear coarse and ET (P<0.05). The average dry matter accumulation, yield, ET, and net income of N2 treatment were higher than that of N1 and N3 treatment 5.58 and 15.80%, 4.25% and 16.76%, 4.96% and 3.41%, 8.76% and 29.42%, respectively. R25 treatment significantly enhanced dry matter accumulation, yield and components, ET, WUE, NPFP, net income and input/output. WUE continued to increase with increasing N application while NPFP continued to decrease. Treatment N2R25 had the highest dry matter accumulation and ET, and treatment N2R37.5 had the highest yield, net income and input/output. Spring maize yield was significantly and positively correlated with dry matter accumulation, ET, WUE, net income and input/output. Taking into account the dry matter accumulation, yield, WUE and net income of spring maize, the nitrogen fertilizer management was optimized, and the nitrogen application rate and replacement ratio range were 160~230 kg/hm2 and 8~38%, respectively, spring maize dry matter accumulation, yield, WUE and net income can all reach more than 95% of the optimal value while the NPFP under the this combined treatment was 66.68 ~ 93.98 kg/kg.
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The impacts of extreme climate events on vegetation dynamics in the Qinling-Daba Mountains
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Global warming has contributed to extreme climate events that have had a significant impact on vege-tation. However, the spatio-temporal changes in extreme climate and its influence on vegetation remain unclear in the Qinling-Daba Mountains (QBMs). Based on satellite-derived Normalized Difference Vegetation Index (NDVI) and meteorological datasets, we analyzed the spatio-temporal variations of the NDVI and its response to 19 extreme climate indices in the QBMs. Geographic detector was used to identify the contribution rate of extreme climate indices and their influence on the NDVI. The results indicated that the NDVI significantly increased in the majority of the QBMs (80.34%) and decreased in only a few regions (1.09%) from 2000 to 2020. Noticeable warming was observed in the QBMs from 1960 to 2020, with the temperature increasing more at night than during the day, and regions with a larger change in the extreme temperature events were mostly found in the Western Qinling Mountains (WQMs). During the study period, extreme precipitation events showed weak changes, extreme precipitation intensity increased in the southwestern QBMs, while in the eastern QBMs, extreme precipitation intensity decreased but extreme precipitation frequency increased. Additionally, significant spatial variations were observed in the NDVI reaction to extreme climate indices in the QBMs. The correlations between extreme precipitation indices and the NDVI were higher than those between extreme temperature indices in the WQMs, whereas inverse relationship were observed in the Qinling Mountains (QMs) and Daba Mountains (BMs). We also found that the influence of extreme climate indices on NDVI was not independent, and the interaction between the extreme climate indices amplified the influence of a single index on NDVI in both double-factor or nonlinear ways. The paper can establish scientific evidence for the protection and restoration of vegetation in the QBMs in response to global climate change.
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Multi-scenario Simulation and Water Resource Effects of Integrated Utilization of Saline-alkali Land in Western Jilin Province
Abstract:
[Objective] The integrated engagement of saline-alkali land remains a quintessential stratagem to enhance grain yield whilst embracing the principle of Greater Food. The current simplistic reclamation approaches and the intensive water demands, however, call for a thorough investigation of diversified management strategies and interventions that take into account the impact on water resources.[Methods] The study selected the western part of Jilin Province as the study area and adopted the FLUS model to forecast the utilization patterns of saline-alkali land resources until 2030 under four scenarios: natural progression, grain security, integration of grain and forage production, and ecological protection. The InVEST model is then applied to evaluate the variations in water yield across these scenarios.[Results] (1)From 2000 to 2020, 1 540.18 km2 of saline-alkali land in the study area was put to use, predominantly restored to grassland or reclaimed as cultivated land, with a substantial risk of secondary salinization in drylands. (2)Under all scenarios, the reclamation of saline-alkali land for agriculture prevails. In the grain security scenario, the paddy fields and dry lands account for 67.48% and 4.23%, respectively. When compared with the natural progression scenario, the grassland area is set to expand by 60.76 km2 in the integration of grain and forage production scenario, and ecological land will increase substantially under the ecological protection scenario. (3)By 2030, water yield is projected to decrease in all four scenarios relative to the baseline period, with the ecological protection scenario facing the steepest reduction at 3.71×108 m3. Conversely, the integration of grain and forage scenario offers a well-balanced solution, ensuring the output of crops and forage while easing the water pressures initiated by the management of saline-alkali land.[Conclusion] Utilization of saline-alkali land in the Songnen Plain requires a balanced and strategic approach that supports both grain and forage production. Efforts should be made on maintaining the equilibrium between the supply of agricultural and fodder resources whilst ensuring food and ecological security. The overarching goal is to regulate the ecological restoration of our territorial space and utilization of degraded lands following the concept of Greater Food.
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Regulatory mechanisms of nitrogen and phosphorus transformation and maize growth in soils of the black soil zone: based on field experiments
Abstract:
[Objective] To investigate the effects of different tillage patterns and biochar application on soil nitrogen and phosphorus transformation and maize growth and development in farmland in the black soil area. [Methods] In this paper, 10 different treatments were set up through a field experiment: deep tillage + 0t/hm2 biochar (DCK), deep tillage + 3t/hm2 biochar (D3), deep tillage + 6t/hm2 biochar (D6), deep tillage + 9t/hm2 biochar (D9), deep tillage + 12t/hm2 biochar (D12), shallow tillage + 0kg/mu biochar (SCK), shallow tillage + 3t/hm2 biochar (S3), shallow tillage + 6t/hm2 biochar (S6), shallow tillage + 9t/hm2 biochar (S9), and shallow tillage + 12t/hm2 biochar (S12), to investigate the combined effects of different tillage patterns and biochar application on soil nitrogen and phosphorus fractions, enzyme activities, and physiological characteristics of maize. [Results] The results of the study showed that: (1) deep tillage and shallow tillage in combination with biochar application could effectively improve soil structure, increase the geometric mean diameter of agglomerates and reduce the percentage of damage, and the deep tillage treatment was more effective than the shallow tillage treatment; (2) the application of biochar improved soil nitrogen-phosphorus fractions, urease activity, and alkaline phosphatase activity, and the effect of applying biochar at the rate of 9t/hm2 was the best, which was more pronounced in the deep tillage treatment; (3) deep tillage The application of biochar up to 9t/hm2 under deep plowing treatment increased the total nitrogen and phosphorus contents and glutamine synthetase activity of leaves, and decreased the acid phosphatase activity; (4) the yield of corn under deep plowing condition with the application of 9t/hm2 of biochar was as high as 17.37t/hm2, which was increased by 28.9% compared with that of the CK group. [Conclusion] The deep-tillage treatment and application of 9t/hm2 biochar provided a reference for the nutrient environment and crop growth in agricultural fields in the black soil area.
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Spatiotemporal distribution and hot spots analysis of ecosystem services in Beijing and Tianjin sandstorm source region
Abstract:
In order to assess the ecological benefits and ecological impacts after the implementation of the ecological project in the Beijing-Tianjin wind and sand source area, based on the remote sensing, meteorological, soil, and land use data of the Beijing-Tianjin wind and sand source area from 2000-2017, the CASA (Carnegie-Ames-Stanford approach) model, the InVEST ( Integrated valuation of ecosystem services and trade offs) model, RWEQ (Revised wind erosion equation) model, and RUSLE (Revised Universal Soil Loss Equation) model, respectively. The water yield, soil conservation, carbon sequestration and wind and sand services were estimated respectively, and the Getis-Ord Gi* statistical index method was used to identify the ecosystem services hot and cold spots in the Beijing-Tianjin wind and sand source area. The results showed that (1) each ecosystem service function showed an increasing trend from 2000 to 2017, and the high value areas of the four ecosystem service functions were concentrated in the southeast of the study area, and the low value areas were concentrated in the northwest of the study area. (2) All four ecosystem services showed a significant hotspot area increase in the Ordos Plateau sandy land management area in the southwestern part of the Beijing-Tianjin wind and sand source from 2000 to 2017; the area of hotspot for carbon sequestration services increased significantly, of which the sandy land management area in the Hunshandak-Khorqin sandy area and the hilly mountainous area of the Damshang Plateau and northern North China The hotspot area of water production service has not changed significantly, and the hotspot area is mainly concentrated in the southern part of the study area in the Damshang Plateau and the hilly and mountainous water conservation management area in northern China, and the distribution of the hotspot area is more scattered; the coldspot area of windbreak and sand fixation service has increased in area; the area of the coldspot area of soil conservation service has a small percentage and not much change, and the regional capacity of soil conservation and supply is relatively average. The regional soil conservation supply capacity is relatively average. (3) The results of multiple ecosystem services show that the southeastern region of the study area is able to provide two or more high-value ecosystem service functions, and belongs to the key ecosystem service function supply area, accounting for about 15.5% of the whole study area. (4) The four ecosystem service hotspot areas of forest land accounted for a relatively high percentage of the area from 2000 to 2017, and the hotspot areas of carbon sequestration service functions of grassland and forest land increased significantly, and forest land can provide a high level of integrated ecosystem service functions. The implementation of the Beijing-Tianjin Wind and Sand Source Control Project has improved the overall ecosystem service function in the region, and the results of the study can provide scientific data for assessing the effectiveness of the restoration of the Beijing-Tianjin Wind and Sand Source Control Project, and ultimately realize the sustainable development of the ecological environment in the Beijing-Tianjin region.
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Soil microbial biomass and ecological stoichiometric characteristics of typical land use types in loess hilly region
Abstract:
[Objective]To investigate the effects of the typical ecological management model of "upward retreat and downward push" on soil-microbial C, N and P and their ecological stoichiometric ratios in loess hilly areas.[Methods] In this study, typical land use types (artificial forest land, terrace, and Chuanland) in the loess hilly area of Ningxia were selected to study the response of soil-microbial C, N and P contents to land use changes and to analyze the ecological stoichiometric ratios, microbial entropy (qMBC, qMBN, and qMBP), and stoichiometric imbalances (C:Nimb, C:Pimb, and N:Pimb) among the Relationship.[Results] (1) Under the three typical land use types, SOC, C:P and N:P in artificial forest land were higher than those in terraced and Chuanland, while TP content in agricultural land (terraced and Chuanland) was higher than that in artificial forest land. (2) The contents of soil microbial biomass C, N and P ranged from 51.56 to 133.19, 7.97 to 21.98, and 4.63 to 12.81 mg/kg, respectively. Among them, soil microbial biomass C, N and P were in the order of artificial forest land > terrace land > Chuanland. The ratio of microbial biomass C, N, P, C:Nimb, C:Pimb, N:Pimb, had certain characteristics of internal stability, and had no significant difference among different land use types. (3) The three typical land use types have significant effects on microbial entropy, with the qMBC ranking as terraced land > artificial forest land > Chuanland, while the qMBN and qMBP ranking as artificial forest land > terrace land > Chuanland. Combined with RDA analysis, it was concluded that microbial biomass C:P (R2=0.75, p<0.01) and C:Pimb (R2=0.74, p<0.01) were the key factors affecting the change of qMB.[Conclusion] In summary, the typical ecological management mode of "upward retreat and downward push" caused significant changes in soil C, P and microbial C, N and P contents, and the soil-microbial C, N and P and their stoichiometric ratios were mainly influenced by phosphorus under the typical land-use types.
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Effects of Soil Organic Carbon and Moisture on Different Vegetation Restoration Types in the Mu Us Sandy Land
Abstract:
Vegetation restoration is one of the most effective measures to improve the fragile ecological environment in arid regions. Extensive vegetation restoration in the Mu Us Sandy Land has significantly influenced the soil carbon and water cycling within the area. Investigating the responses of soil organic carbon and moisture content to vegetation restoration holds crucial significance for the sustainable development of the ecological system in this region. This study focused on the natural restoration grassland and different vegetation restoration types, including Artemisia desertorum, Salix psammophila, A. desertorum-S. psammophila mixed(shrub-shrub mixed), Pinus sylvestris, S. psammophila-P. sylvestris mixed(tree-shrub mixed), in the Mu Us Sandy Land. A bare sandy area was used as the control. The aim was to investigate the effects of different vegetation restoration types on soil carbon and moisture content within the 0-5 m soil profile. The results showed that:(1)Vegetation restoration increased, with S. psammophila-P. sylvestris mixed, P. sylvestris, Grassland, A. desertorum-S. psammophila mixed, A. desertorum-S. psammophila mixed, and A. desertorum showing decreasing trends, with significant accumulation effects observed within the 0-20 cm soil depth. As soil depth increased, the organic carbon content of all vegetation types gradually decreased. Within the depth range of 80-220 cm, A. desertorum, S. psammophila, and A. desertorum-S. psammophila mixed exhibited carbon loss.(2)Different vegetation restoration types showed varying degrees of soil moisture deficit in deep soil layers, primarily concentrated at 1-3 m, with S. psammophila-P. sylvestris mixed showing the most severe deficit, followed by P. sylvestris, A. desertorum-S. psammophila, S. psammophila, Grassland, A. desertorum.(3)Root were identified as the main factors influencing soil organic carbon content and moisture consumption. Soil organic carbon content exhibited a negative correlation with soil moisture within the 0-5 m soil depth range. Vegetation carbon storage was achieved at the expense of consuming deep soil moisture, with S. psammophila-P. sylvestris mixed exhibiting the least water consumption per unit of fixed carbon. The study suggests that S. psammophila-P. sylvestris mixed exhibits favorable effects in vegetation restoration from the perspective of soil carbon retention and water retention in the Mu Us Sandy Land.
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Estimation and Prediction of Water Conservation Capacity in Shaanxi Province Based on InVEST-PLUS Model
Abstract:
The InVEST model and PLUS model were coupled to calculate the water conservation amount in Shaanxi Province from 2000 to 2020 and predict the water conservation amount under land use changes in the future in 2030. The results indicate that the average water conservation amount in Shaanxi Province from 2000 to 2020 was 132.25mm, with a spatial distribution characteristic of gradually increasing water conservation amount from north to south.From the perspective of vegetation types,forest land is the main body of water conservation in Shaanxi Province. The average annual water conservation amount is 199.55×108m3. From the administrative region, Ankang City (308.96mm) has the largest water conservation amount. The total amount of water source conservation in 2030 is 285.16×108m3,8.68×108m3 less than in 2020..
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Modeling and Analysis of Hydraulic Erosion in Slope Farmland Using Gradient Lifting Tree Model
Abstract:
Based on the Gradient Lifting Tree Model (GBDT), a hydrological experimental dataset from the Zizhou Runoff Experimental Station in the Yellow River Basin was used to model and analyze hydraulic erosion on sloping farmland. The results showed that: 1. The coefficient of variation for secondary rainfall erosion (0-122.72 t/km2), runoff depth (0.02-17.20 mm), rainfall duration (2-1410 min), and average rainfall intensity (0.02-4.63mm) in the dataset are all greater than 1, indicating high variability. Most variables exhibit a right-skewed distribution.2. When dividing the dataset into training and testing sets, the model''s accuracy in predicting soil erosion during secondary rainfall (R2=0.81) is slightly higher than that of the runoff depth prediction model (R2=0.80). However, the number of layers in the secondary erosion model (8 layers) exceeds that of the runoff depth prediction model (5 layers), suggesting a more complex erosion mechanism compared to the runoff mechanism. 3. The prediction results are not ideal for small secondary erosion amounts and runoff depths due to limitations in feature extraction. Future research should explore additional combinations of independent variables to identify more relevant factors. 4. The main influencing variables differ between the erosion runoff and sediment production processes. Precipitation characteristics play a major role in runoff production, while erosion sediment production is mainly influenced by the combined effects of precipitation and terrain-related independent variables. This study, being data-driven, provides insights into the erosion mechanism of slope farmland in the Loess Plateau and serves as a scientific basis for sustainable regional development.
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The Impact of Flexible Vegetation on Surface Runoff Hydraulic Characteristics and Erosion
Abstract:
There is limited research on the influence of near-surface coverage of flexible vegetation on reducing runoff and erosion yields, as well as on regulating the hydraulic characteristics of surface runoff. Based on the principles of fluid mechanics and hydraulics, this study conducted indoor drainage experiments under five coverage levels, five slopes, and three flow rate combinations. The erosion patterns and hydrodynamic characteristics under flexible vegetation cover conditions were systematically investigated. The results indicate: (1) The distribution of erosion volume initially rises and then falls with increasing slope, with flow rate having a more significant impact on the erosion process at higher slopes. (2) As the coverage of flexible vegetation increases, erosion volume decreases initially and then increases, with 50% coverage as the turning point. (3) The average flow velocity (v) decreases with increasing coverage, and the decreasing trend becomes less steep as coverage increases. The variation trend of the Froude number (Fr) is similar to that of the average flow velocity. The resistance coefficient (f) is linearly correlated with coverage, and with increasing slope, the value of the resistance coefficient gradually decreases. Reynolds number (Re) is more sensitive to soil erosion than Fr, v, and f. (4) With increasing vegetation coverage, morphological shear force increases (particle shear force decreases), and morphological shear force plays a decisive role in the variation of total shear stress, which is positively correlated with vegetation coverage. This study lays a theoretical foundation for understanding the erosion patterns of vegetated slopes, and promotes the extension of open channel hydraulics theory in slope surface flow.
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Relationship between soil infiltration and crust under continuous and intermittent precipitation
Abstract:
The Loess Plateau, one of the ecologically vulnerable regions in China, experiences concentrated and intense precipitation, characterized by significant topographical variations and fragmented landscapes. With sparse vegetation cover, the area faces prominent issues of soil erosion. Soil crusts, characterized by high bulk density and low porosity, are a common soil structural feature in the Loess Plateau formed under the impact of precipitation, runoff compaction, or irrigation. The formation of soil crusts severely affects water infiltration and runoff generation, hindering efficient water resource utilization and impeding the conversion between surface water and groundwater. To investigate the relationship between soil crust and infiltration performance under continuous and intermittent precipitation conditions, three typical cultivated soils from the Loess Plateau were selected. Indoor simulated precipitation experiments were conducted, utilizing three precipitation drop diameters (2.67 mm, 3.39 mm, and 4.05 mm), continuous precipitation durations of 10, 20, and 30 minutes, and 1-2 episodes of intermittent precipitation. The study analyzed the relationship between crust strength, cohesion, and soil infiltration performance under different precipitation conditions. Furthermore, variations in the content of soil aggregates of different particle sizes in the topsoil under different precipitation conditions were examined, along with their influence on infiltration performance. Finally, using grey relational analysis, the study summarized the weights of various factors affecting infiltration performance and ranked their significance. The results revealed that infiltration performance decreased with the increase in continuous precipitation duration and the number of intermittent precipitation episodes. Under equivalent precipitation duration and intensity, intermittent precipitation exhibited a greater reduction effect on infiltration compared to continuous precipitation. Crust strength and cohesion increased with prolonged continuous precipitation duration and a higher number of intermittent precipitation episodes. Infiltration performance of chestnut soil and black loam soil exhibited a significant linear correlation with crust strength and cohesion (P<0.05). As the duration of continuous precipitation and the number of intermittent precipitation episodes increased, the generated crust strength and cohesion also increased, consequently resulting in a greater reduction in infiltration efficiency. In contrast, the infiltration performance of sandy loam soil demonstrated a nonlinear correlation with crust strength and cohesion (P<0.05). Experimental results indicated that with an increase in the number of intermittent precipitation episodes, soil aggregates became more fragmented. Moreover, as precipitation intensity increased with precipitation duration, the efficiency of degrading large aggregates (>0.25 mm) into smaller aggregates (<0.25 mm) also increased. Comparative analysis of the changes in Mean Weight Diameter (MWD) and Geometric Mean Diameter (GMD) of soil crusts under different precipitation conditions revealed that a smaller MWD and GMD corresponded to poorer infiltration performance and a greater reduction in infiltration efficiency. Grey relational analysis further emphasized the significance of MWD and GMD as the most influential factors affecting infiltration performance, with higher correlation observed for intermittent precipitation compared to continuous precipitation. This study provides valuable insights for mitigating soil erosion and promoting effective water resource management in the Loess Plateau.
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Multi-scenario prediction of land use change and carbon stock in Shaanxi Province based on SD-PLUS coupled model
Abstract:
Studies have shown that different land use modes have significant effects on regional ecosystem carbon stocks. In this paper, using the SD-PLUS coupled model and the coupled shared socio-economic route and representative concentration route (SSP-RCP) scenario proposed by the International Coupled Model Comparison Program Phase 6 (CMIP6), the land use changes in Shaanxi Province in 2030 were projected, and then the different future scenarios simulated by the InVEST model were used to predict the Shaanxi Province"s carbon storage and its spatial distribution under different future scenarios simulated by the InVEST model. The results show that;(1)The SD model constructed was tested historically, and its error was less than 5%, and the Kappa index of land use in 2020 simulated by the PLUS model was 0.86, and the accuracy and reliability of the model generally met the requirements;(2) Under the three scenarios, the area of future construction land increases, and the scenarios with the lowest to highest growth rates are: SSP126, SSP245, SSP585; under all scenarios, the area of forest land increases, and the area of watersheds remains stable; the area of grassland has a small increase under the SSP126 scenario, and decreases in other scenarios; and the area of arable land decreases in all three scenarios;(3) Carbon stock in Shaanxi Province decreases under all three scenarios, with the decrease in carbon stock in the Guanzhong Plain being the main reason for the decrease in carbon stock in Shaanxi Province. The area of ecological land occupied by the expansion of construction land is the smallest under the SSP126 scenario, which takes into account both socio-economic development and the need for ecological protection, and can provide a reference model for the future protection of land resources and high-quality development in Shaanxi Province.
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Response of vegetation NPP to multiscale meteorological drought in southwest China
Abstract:
[Objective] Since the beginning of the 21st century, the frequent occurrence of extreme drought events in southwest China has had a serious negative impact on vegetation growth. It is of great significance to study the response mechanism of vegetation to drought at different time scales.[Methods] Based on vegetation net primary productivity (NPP) data with a spatial resolution of 500m from 2001 to 2019 and standardized precipitation Evapotranspiration index (SPEI) data on a continuous scale from 1–24 months in Southwest China, Correlation analysis, maximum synthesis method and significance test were used to analyze the responses of NPP of different geomorphic types and vegetation types to multi-scale SPEI in Southwest China.[Results] (1) In the annual scale, seasonal scale and growing season, the responses of vegetation NPP and SPEI at 1-24 months are dominated by the January-March scale, and vegetation NPP has a good response to short-term drought changes, but a relatively poor response to medium and long-term drought changes. (2) The response of NPP to SPEI at 1-24 month scale showed significant spatial heterogeneity and seasonal differences. The correlation between NPP and SPEI at 1-24 month scale in summer was significantly negative in the five major geomorphic regions. The response area of NPP in spring to SPEI at July-September scale was larger than that in other seasons. The area of vegetation NPP positively correlated with SPEI from 1 to 24 months in autumn and winter was larger, reaching 72% and 79.4%, respectively. In the correlation analysis between vegetation NPP and SPEI from 1 to 24 months in growing season, the area with the largest positive correlation was Guangxi Hills, while the area with the largest negative correlation was Hengduan Mountain. (3) The responses of NPP to SPEI from 1–24 months were different among different vegetation types. Although the response characteristics of grassland, scrub and forest land to SPEI were basically similar, the trend of negative correlation between NPP and SPEI became stronger with the scales of SPEI decreased in summer for all types of vegetation. This suggests that all types of vegetation are more susceptible to drought under high temperature and drought conditions in summer.[Conclusion] The research results provide effective scientific support for the protection and restoration of the ecosystem in Southwest China, and provide important theoretical basis for disaster prevention and reduction and coping with climate change, and help formulate more targeted policies and measures to promote the sustainable development of Southwest China.
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Temporal and Spatial Changes of Soil Erosion and Its Response to Landscape Pattern in Dabie Mountains of Western Anhui in Recent 30 Years
Abstract:
[Objective]The Dabie Mountain area in western Anhui Province is an important ecological transition area between the Yangtze River Basin and the Huaihe River Basin in Anhui Province. The study on the landscape pattern and soil erosion and their relationship in this area is helpful to provide reference for the regulation of landscape pattern and soil erosion control in this area.[Methods]The RULSE model was used to calculate the soil erosion modulus in the Dabie Mountains of western Anhui in the past 30 years. The changes of landscape pattern were described by landscape index, and the influence of landscape index on soil erosion was explored by partial least squares regression (PLSR).[Result]In recent 30 years, the soil erosion modulus showed the trend of decreasing first and increasing later. The areas with serious soil erosion are mainly concentrated in the central and western regions and the southern mountainous areas. In most areas, the soil erosion intensity is mainly slight and mild, and the erosion intensity of different land use types has obvious difference, which is grassland > cultivated land > forest land.The land use type and landscape pattern are generally stable. The change of landscape pattern is mainly manifested in the reduction of landscape fragmentation and the improvement of landscape heterogeneity and connectivity. Shannon’s Diversity Index (SHDI), boundary Edge Density Index (ED), Proportion of Like Adjacencies (PLADJ) and Landscape Shape Index (LSI) have significant explanatory significance for Dabie Mountain area in west Anhui Province. Shannon’s Diversity Index (SHDI), Edge Density Index (ED) and Landscape Shape Index (LSI) had significant positive effects on soil erosion, while Proportion of Like Adjacencies (PLADJ) had significant negative effects on soil erosion.[Conclusion]In the Dabie Mountains of western Anhui, the increase of landscape fragmentation and the decrease of landscape connectivity will significantly promote soil erosion.
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Spatio-Temporal Response of Supply-Demand Balance of EcosystemServices based on Land Use Change in the Middle Reaches of the Yangtze River
Abstract:
[Objective] Taking the middle reaches of the Yangtze River as the research area and the period from 2000 to 2018 as the research period, this study aims to reveal the spatio-temporal characteristics of supply-demand balance of ecosystem service, and further to explore the dual effects of land use change on the supply-demand balance of ecosystem service and its influencing mechanism. [Methods] The methods of quantitative matrix of supply-demand of ecosystem service, and contribution rate of land use change were employed. [Results] (1) During the research period, the supply-demand balance of ecosystem services in the middle reaches of the Yangtze River is deteriorating, which is mainly caused by the large-scale expansion of construction land and the large-scale reduction of cultivated land and forest land, resulting in the decrease of ecosystem service supply capacity and the increase of consumption demand. (2) The relationship between ecosystem service supply has changed from trade-off to synergy in time scale, and the synergy between demand and supply-demand balance has been further enhanced in time scale, but the trade-off or synergy between supply, demand, and supply-demand balance is highly heterogeneous in spatial scale. (3) Land use change in the MRYR has dual effects on the supply-demand balance of ecosystem services, and the deterioration effect is significantly greater than the improvement effect, but the types of land use change that cause the improvement and deterioration of supply- demand of ecosystem services and their sub-services have temporal heterogeneity. [Conclusion] Clarifying the qualitative and quantitative relationship among supply and demand of ecosystem services, and land use change, which helps to achieve the improvement of ecological environment by by rationally regulating the transformation of land use types.
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