Soil C, N, and P and C:N:P stoichiometry associated with environmental factors in two typical alpine grasslands in northern Tibet

Purpose Soil nutrient stoichiometry and their environmental control are critical for assessing biogeochemical cycling, maintaining ecosystem function, and sustainable development. This study investigated how soil chemical measurements such as soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) vary with soil depth in northern Tibet, and how they regulate various grassland ecosystems. Materials and methods Normalized difference vegetation index (NDVI), soil physicochemical properties, and geo-climatic factors data were collected from 57 sampling sites. Using analysis of variance and rank-sum test, we studied differences in SOC, TN, and TP contents and their stoichiometry between alpine meadows (AM) and alpine steppe (AS), and among four soil layers (0–10 cm, 10–20 cm, 20–30 cm, and 30–50 cm depth), using Spearman correlation analysis and redundancy analysis (RDA) to determine the dominant environmental factors. Results and discussion AM soil always had more SOC, TN, and TP than AS soil. The C:N (R CN ) and C:P ratios (R CP ) differed mainly in response to the type of alpine grassland in the uppermost soil layer, whereas differences in the N:P ratios (R NP ) were not significant throughout all strata. These nutrients and ratios decreased with increasing soil depth, and the differences between the uppermost and deepest soil layers were significant. Correlation analysis revealed that soil properties and geo-climatic factors were more closely related to SOC, TN, and TP and their stoichiometry in AM than in AS. RDA revealed that soil factors mainly contributed to soil nutrients and stoichiometry in uppermost soil layer while geo-climate did in deeper three soil layer. Conclusions Our research, which highlights how soil C:N:P ratios in northern Tibet depend on background soil characteristics, can be used to optimize soil stoichiometry for ecosystem functions and sustainable development.