Turnover and Nestedness Explained Differently on Soil Fungi, Bacteria, and Archaea Community Beta Diversities After Nitrogen Addition

Soil microbes are sensitive to nitrogen enrichment, but the mechanisms shaping beta diversity along and within nitrogen gradients may differ among microbial communities. In a seven-year nitrogen addition experiment in the Qinghai-Tibet alpine meadow, we calculated overall beta diversity of soil fungal, bacterial and archaeal communities, partitioning into turnover and nestedness components. Beta diversity was compared along nitrogen addition treatment distance (0, 5, 10, and 15 g N m^-2 yr.^-1) and within-treatment community dispersion (i.e., variation among replicates under the same nitrogen level). We found nitrogen addition altered community composition of soil fungi and bacteria, but not archaea. Along nitrogen addition treatment distance, the overall beta diversity of fungi and bacteria increased due to turnover, while that of archaea was stabilised by increasing turnover and decreasing nestedness. Within treatments, dispersion in bacterial overall beta diversity and turnover increased, whereas archaeal overall beta diversity decreased at higher nitrogen addition level, and that of fungi did not change. Bacterial beta diversity was more susceptible to changes in plant community composition and soil properties after nitrogen addition than that of fungi and archaea. Our results highlight distinct responses of different soil microbial communities and partitioned community diversity patterns to nitrogen addition, which is critical for predicting regional microbial diversity and informing global conservation efforts.