Shift in soil bacterial communities from K‐ to r‐strategists facilitates adaptation to grassland degradation

Abstract Numerous studies have investigated bacterial community structure and bacterial responses to human management at various spatial and temporal scales in grassland ecosystems; however, research on soil bacterial community assembly dynamics in the course of grassland degradation is limited. Here, the authors investigate the response and assembly processes of bacterial communities adopted in two grasslands with different degrees of degradation. Stochastic processes dominated bacterial community assembly in response to grassland degradation. With an increase in degree of grassland degradation, bacterial richness decreased from 3526 to 2930 and from 3573 to 3021 in Grassland 1 (G1) and Grassland 2 (G2), respectively; however, functional gene richness increased from 6760 to 6887 and from 6851 to 7040 in G1 and G2, respectively. The KO gene numbers of each operational taxonomic units were positively correlated with standardized effect size measure of the mean nearest taxon distance ( R 2 = 0.38 and 0.68 in G1 and G2, respectively), indicating that phylogenetic dispersion in community assembly under grassland degradation increases functional genes. Furthermore, different phyla exhibited distinct response strategies: Proteobacteria and Bacteroidetes, as r ‐strategists, exhibited positive productivity, with increases in diversity, abundance, and niche breadth; other phyla exhibited greater phylogenetic dispersion, and less diversity and niche overlap, highlighting the role of K ‐strategists in improving resource‐use efficiency in response to nutrient loss. The transition of communities from K ‐ to r ‐strategists could help communities adapt to environmental disturbance. The results enhance our understanding of bacterial community assembly and ecology‐associated functions in underground grassland ecosystems, which could facilitate degradation prediction and grassland management.