Elevation explains variation in soil microbial diversity and community composition under experimental warming and fertilization treatments in mountain meadows

Climate warming and atmospheric nitrogen deposition threaten plant biodiversity in mountain ecosystems; however, their influences on soil microbial diversity and community composition remain poorly understood. We conducted randomized block factorial experiments in three mountain meadows of different elevations on Yulong Snow Mountain, China. These include open-top chambers and urea fertilization to simulate climate warming and nitrogen deposition, respectively. Using Next-generation sequencing (NGS) technology, we measured soil microbial diversity and community composition for archaea, bacteria, and fungi. In addition, we measured plant diversity, plant aboveground biomass, soil chemical characteristics, air temperature, and rainfall as quantitative predictors. We determined the most parsimonious relationships with soil microbial diversity and community composition for each predictor based on generalized linear mixed-effect models and distance-based redundancy analyses, respectively. Elevation explained the majority of the variation associated with microbial diversity under short-term warming and fertilization. Microbial diversity decreased with increasing elevation, and the tendency was strongest for bacteria. Fertilization decreased bacterial diversity at the highest elevation but increased fungal diversity across the elevational gradient; microbial community composition was weakly affected by elevation. Climatic factors, especially air temperature, were the most important determinants of soil microbial diversity and composition. Taken together, the results presented here contribute to our understanding of how future global climate change may impact the belowground diversity of mountain ecosystems.