Microbial diversity is especially important for supporting soil function in low nitrogen ecosystems

Total nitrogen (N) content is one of the most important factors limiting soil function in terrestrial ecosystems. One of the most important roles of microbial diversity is to provide tools to boost N mineralization making N available for plants and microbes. However, how N content interacts with microbial diversity in explaining soil function remains virtually unknown. Here, we combined two independent regional and global field surveys with a controlled microcosm experiment, and found that as N content decreases, it increases the dependence of multiple soil functions (e.g., nutrient cycling, climate regulation, and soil fertility) on microbial diversity, especially in soils with low N content (soil total N content < 1.00 g kg-1). Meanwhile, diversity of fungi, especially mycorrhizal fungi played an important role in maintaining soil function compared to bacteria in low N ecosystems. Our study emphasizes the need to protect microbial diversity in future management practices to support function in ecosystems with low levels of N content.