Jiangxi Agricultural University
为探究磷输入如何调节大气氮沉降对土壤团聚体有机碳含量以及碳与磷之间的关系的影响，在常绿阔叶林土壤建立长达6年（2015-2021年）的养分添加长期监测试验平台，包括4个处理：对照（P0+N0，0 kg P ha-1 a -1+0 kg N ha-1 a -1）、氮添加（P0+N100，0 kg P ha-1 a -1+100 kg N ha-1 a -1）、磷输入（P50+N0，50 kg P ha-1 a -1+0 kg N ha-1 a -1）以及氮磷同时输入（P50+N100，50 kg P ha-1 a -1+100 kg N ha-1 a -1），3个重复，共计12个样地。于2021年8月采集样地0-10 cm土壤样品，测定基础理化性质、土壤粒径分布规律、不同粒径土壤团聚体磷组分以及有机碳（SOC）含量。研究结果表明：（1）P0（无P输入下，0 kg P ha-1 a -1）处理下，氮添加显著增加大团聚体占比，减少黏、粉粒含量，提高各团聚体粒径中SOC含量；氮添加分别显著降低和增加团聚体黏、粉粒中易分解态磷组分（LP）和难分解态磷组分（RP）含量。（2）P50（有P输入下）处理下，氮添加显著提高土壤团聚体平均几何直径（GMD），；对各粒径团聚体中磷组分和SOC含量均无显著影响。（3）P0处理下，土壤团聚体SOC与难分解态磷呈现正相关关系；P50处理下，土壤团聚体SOC与各功能磷组分无显著相关。由此推断，P0处理下，氮添加通过提高常绿阔叶林土壤团聚体黏、粉粒径中难分解态磷而增加土壤有机碳的固持；P50处理下，氮添加对各粒径中有机碳的影响可能受到生物因素的调节，与磷的有效性无关。总之，氮沉降对常绿阔叶林土壤团聚体中碳磷内在关系的影响受到磷的调控，该研究结果为森林土壤碳循环应对全球气候变化提供数据支撑。
In order to explore how phosphorus input regulates the effects of atmospheric nitrogen deposition on soil aggregate organic carbon content and the coupling relationship between carbon and phosphorus, a long-term monitoring test platform for nutrient addition for 6 years (2015-2021) was established in the soil of evergreen broad-leaved forest, including 4 treatments: Control (P0+N0, 0 kg P ha-1 a -1 +0 kg N ha-1 a -1), nitrogen addition (P0+N100, 0 kg P ha-1 a -1 +100 kg N ha-1 a -1), phosphorus input (P50+N0, 50 kg P ha-1 a -1 +0 kg N ha-1 a -1) and nitrogen and phosphorus were simultaneously input (P50+N100, 50 kg P ha-1 a -1 +100 kg N ha-1 a -1), 3 replicates were performed, and a total of 12 plots were obtained. 0-10 cm soil samples were collected from the sample site in August 2021 to determine the basic physical and chemical properties, soil particle size distribution, phosphorus components of soil aggregates of different particle sizes, and organic carbon (SOC) content. The results showed that: (1) Under P0 (0 kg P ha-1 a-1 without P input) treatment, nitrogen addition significantly increased the proportion of large aggregates, reduced the content of clay and powder particles, and increased the SOC content of each aggregate particle size. Nitrogen addition significantly decreased and increased the content of LP and RP components in aggregate clay and powder, respectively. (2) Under P50 (50 kg P ha-1 a-1 with P input) treatment, nitrogen addition significantly increased the mean geometric mass diameter (GMD) of soil aggregates, and increased the proportion of large aggregates while decreased the proportion of small aggregates. Nitrogen addition had no significant effect on the content of phosphorus and SOC in aggregates of different particle sizes. (3) Under P0 treatment, soil aggregate SOC showed a positive correlation with refractory phosphorus. Under P50 treatment, SOC of soil aggregates had no significant correlation with all functional phosphorus components. It is concluded that under P0 treatment, nitrogen addition can increase soil organic carbon retention by increasing the insoluble phosphorus in aggregate viscosity and powder particle size of evergreen broad-leaved forest. Under P50 treatment, the effect of nitrogen addition on organic carbon in each particle size may be regulated by biological factors and has nothing to do with the availability of phosphorus. In conclusion, the effect of nitrogen deposition on the coupling relationship between carbon and phosphorus in soil aggregates in evergreen broad-leaved forests is regulated by phosphorus. The results of this study provide data support for the response of forest soil carbon cycling to global climate change.