Ecological stoichiometric characteristics of soil carbon, nitrogen, and phosphorus in Alpine Marsh wetlands of Qinghai Qilian Mountain National Park and their driving factors

The alpine marsh wetland in the Qilian Mountain National Park of Qinghai is an important component of the Qinghai-Tibet Plateau ecosystem. The ecological stoichiometric characteristics of soil carbon (C), nitrogen (N), and phosphorus (P) in this region are crucial for understanding alpine wetland ecological processes and nutrient cycling mechanisms. This study focuses on typical alpine marsh wetlands in the area, collecting 54 soil samples from different degrees of degradation and soil depths. One-way ANOVA was used to evaluate the effects of degradation degree and soil layer depth on C, N, and P content and their ecological stoichiometric ratios. Additionally, multiple regression and hierarchical segmentation methods were employed to explore the driving mechanisms of topography, climate, soil, and vegetation factors on ecological stoichiometric characteristics. The results indicate: 1) As wetland degradation intensifies, soil organic carbon, total nitrogen, and total phosphorus content decrease by 28.1%, 36.6%, and 36.3%, respectively, with C/P and N/P ratios decreasing and C/N ratios increasing. Both element content and stoichiometric ratios decrease with increasing soil depth. 2) The C/N and N/P ratios suggest nitrogen limitation in the soil, while the C/P ratio indicates relatively sufficient phosphorus. 3) Soil ecological stoichiometric characteristics are driven by multiple factors, with C/N primarily influenced by soil properties (35.19% contribution), C/P regulated by vegetation-soil interactions (29.12% and 28.17%), and N/P mainly controlled by climate factors (34.78%). This study elucidates nutrient element cycling characteristics in alpine marsh wetland ecosystems, providing important insights into the coupled relationships of C, N, and P in alpine wetland ecosystems, nutrient limitation mechanisms, and ecological responses.