Bacterial community structure drives soil multifunctionality along a precipitation gradient in the Inner Mongolian shrublands

The impact of precipitation patterns on microbial community structure and diversity has been extensively studied. However, there is limited research on the influence of precipitation on microbial diversity and ecosystem multifunctionality, particularly in arid shrub ecosystems. A clear gradient occurs in the annual precipitation from east to west on the Inner Mongolian Plateau, which is an ideal region for investigating how shrub soil microbial communities respond to rainfall. This research explored how precipitation influences the diversity, structure, network complexity, and cohesion of the shrub soil bacterial community, and their connections with soil multifunctionality across a 1500 km precipitation gradient in northern China. The findings indicated a pattern where bacterial community diversity and network complexity initially increased but later declined as precipitation levels rose, whereas microbial network cohesion and soil multifunctionality showed a notable increase. Mean annual precipitation had the strongest direct effect on the overall bacterial community and network structures. While previous studies have demonstrated that microbial network complexity can reliably predict ecosystem functioning, our findings do not align with this conclusion. Instead, our study highlights the crucial role of bacterial α-diversity in modulating the relationship between microbial network complexity and soil multifunctionality. For shrub systems, the correlations of microbial diversity, network complexity, and network cohesion with soil multifunctionality weakened when controlling for differences in habitat and sampling site, but the relationship between bacterial community structure and soil multifunctionality remained robust. Our findings emphasize that only specific functional groups within microbial communities are essential for ecosystem stability. Considering the challenges posed by climate change and the rapid decline in biodiversity, future investigations should focus on these key groups to provide strategic insights for maintaining and enhancing ecosystem functions.