ObjectiveCynodon dactylon is an important component and the dominant species in the ecosystem of the water-level fluctuation zone (WLFZ) of the Three Gorges Reservoir, 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 is of significant importance in comprehending nutrient cycling as well as species adaptation features within the WLFZ.MethodsA 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 was conducted. The carbon, nitrogen, and phosphorus contents in plant organs (roots, stems and leaves) and soil were analyzed to explore the spatial heterogeneity and interrelationships of the ecological stoichiometric characteristics between C. dactylon and soil.Results1) 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 the upstream to the downstream sections, while N/P ratio was relatively stable. 2) From the upstream to the downstream of WLFZ, carbon contents in various organs of C. dactylon exhibited a decreasing trend, while nitrogen and phosphorus contents showed significant increasing patterns, likely due to intensified sedimentation and the resultant higher soil nutrient supply levels in the downstream WLFZ with the prolonged flooding time. Notably, nitrogen content in the leaves demonstrated a degree of spatial stability, suggesting that C. dactylon could absorb nitrogen efficiently and meet its leaf nitrogen requirements preferentially 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 stronger than that in leaves, suggesting that C. dactylon has evolved a strategy for 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 were relatively weak. 5) C. dactylon in the WFLZ generally exhibited strong homeostasis with the homeostasis index decreasing from the upstream to the downstream.ConclusionIn 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 stoichiometric characteristics of C. dactylon. 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.