Leguminous and non-leguminous shrubs have different effects on the soil microbial co-occurrence networks along a precipitation gradient

In alpine meadow ecosystems, shrub encroachment alters the structure and co-occurrence network characteristics of soil microbial communities, and these effects vary with precipitation gradients. However, the specific mechanisms underlying the interactive effects of precipitation and shrub encroachment on soil microbial communities remain unclear. Therefore, this study utilized Illumina MiSeq technology to analyze the effects of leguminous and non-leguminous encroachment, precipitation, and their interactive effects on the complexity and stability of soil microbial co-occurrence networks on the Qinghai-Tibet Plateau. Leguminous shrubs increased the diversity of soil bacteria and fungi, while non-leguminous shrubs increased soil bacterial diversity. Co-occurrence network analysis showed that non-leguminous shrubs decreased network complexity. Piecewise structural equation model showed that the interactive effects between leguminous shrubs and precipitation negatively impacted network stability by reducing the indirect effects of nitrate nitrogen and also through direct effects. The interactive effects between non-leguminous shrubs and precipitation had a positive impact on network complexity through direct effects. In summary, under increased precipitation, leguminous shrubs decreased network stability, while non-leguminous shrubs increased network complexity. These findings reveal the regulatory mechanisms of the interactive effects of precipitation and shrub encroachment on soil microbial communities in alpine meadows, provide a scientific basis for addressing the impacts of climate change on ecosystem functions, and aid in developing conservation strategies to maintain ecosystem stability.