Soil N:P Ratio and Its Regulation Factors in Alpine Wetlands Across the Three Rivers Source Region

Although the ratio of nitrogen (N) and phosphorus (P) could significantly influence ecosystem services and functions, their characteristics and controlling factors are not well-known in the Three Rivers Source Region alpine wetlands. Using data from 32 sites, we estimated the soil N:P ratio. Ordinary least square method, partial correlation analysis, variation partitioning analysis, and structural equation modeling were used to estimate the effects of controlling factors on soil N:P ratio. The soil N:P ratio was on average 8.91 ± 5.04. Soil characteristics, including soil total N, soil moisture, soil pH, NH 4 + -N, and NO 3 — N, played an important role in determining soil N:P ratio. The mean annual precipitation exhibited a stronger positive correlation with soil N:P ratio than the mean annual temperature. Belowground biomass had a stronger influence on soil N:P ratio than aboveground biomass. Meanwhile, the soil N:P ratio also positively correlated with soil microbial biomass. Variation partitioning analysis revealed that abiotic and biotic factors explained 83.54% of the total soil N:P ratio variation. Abiotic factors explained more of the variation in soil N:P ratio than biotic factors, 46.13% of the total variation. And, soil factor was the most significant factor in determining soil N:P ratio. Our finding presented evidence that climate factors of mean annual temperature and mean annual precipitation can affect N content in plant, then regulate microbial biomass C, and finally control soil total N and soil N:P ratio in the Three Rivers Source Region alpine wetlands, which contributed to understanding soil nutrient element dynamics in the terrestrial ecosystem.