Precipitation alleviates microbial C limitation but aggravates N and P limitations along a 3000-km transect on the Tibetan Plateau

Soil microbial resource limitations, which reflect the imbalance between microbial demand and soil resource supply, critically control microbial metabolism and biogeochemical processes. However, disentangling the confounding effects of climatic, edaphic, plant, and microbial factors on microbial resource limitation at broad spatial scales remains challenging. Here, we used the ecoenzymatic vector model to investigate patterns of soil microbial carbon (C) and nitrogen/phosphorus (N/P) limitation across alpine grasslands along a 3000-km aridity gradient on the Tibetan Plateau. We further linked these patterns to plant characteristics (e.g., plant biomass, coverage, and root biomass), soil nutrient properties (e.g., total soil C, N, and P), nutrient stoichiometry (e.g., C:N, C:P, and N:P ratios, and microbial attributes (e.g., microbial biomass C and N) to identify key drivers of variation in microbial resource limitation. Our results highlight a predominant co-limitation by N and P nutrients in microbial metabolism for alpine grasslands, with a notable shift from relative N limitation in alpine deserts to P limitation in alpine meadows, coinciding with the increasing precipitation. Furthermore, soil nutrient availability and stoichiometry were more influential than plant and microbial factors in shaping patterns of microbial relative N/P limitation. In contrast, microbial relative C limitation decreased with increasing precipitation from alpine deserts to meadow ecosystems, primarily driven by soil nutrient availability and plant characteristics. These findings underscore distinct patterns and drivers of microbial C versus N/P limitation in alpine ecosystems, advancing our understanding of microbial-mediated soil C, N, and P recycling.