Variations in soil properties rather than functional gene abundances dominate soil phosphorus dynamics under short-term nitrogen input

Microorganisms play a vital role in regulating soil phosphorus (P) dynamics in terrestrial ecosystems. Here, we investigated the response of soil microbial P cycling potential traits to nitrogen (N) addition via metagenomics and the relationship between microbial potentials and soil P dynamics. Topsoil (0–10 cm) samples were collected from experimental soil that had been maintained for 3 years with low and high level of N addition in an alpine meadow of the Qinghai-Tibet Plateau. Soil microbial functional genes and P fractions were determined. The soil available P and microbial biomass P were significantly affected by N inputs and significantly associated with soil properties (including soil pH, alkaline phosphatase activity, and soil total N and NO3−-N contents). Meanwhile, high N input decreased the relative abundance of the pstS gene, and low N input reduced the relative abundances of phoB, ugpQ and C-P lyase genes. We further found that the pstS gene was a determinant of soil microbial biomass P and significantly correlated with soil pH. Moreover, Alphaproteobacteria with C-P lyase and Actinobacteria related to alkaline phosphatases and phosphate-specific transport were the most abundant taxa but not affected by N input. Short-term high N input could alter soil P dynamics and microbial functional genes. Although there were relationships between the pstS gene, microbial biomass P and soil pH, the microbial functional gene abundance was less important than soil properties in regulating soil P dynamics.