Divergent group-specific pathways of microbial diversity and network complexity maintain soil multifunctionality during alpine grassland restoration.

INTRODUCTION: Soil microorganisms maintain ecosystem multifunctionality, yet the group-specific pathways linking microbial diversity, community assembly, and network complexity to soil multifunctionality (SMF) during natural restoration of abandoned alpine grasslands remain unclear. METHODS: We examined artificial grassland (AG) and 3-, 12-, and 31-year abandoned grasslands (AB03, AB12, and AB31) in Bayinbuluk, Xinjiang, and analyzed bacterial, fungal, and protistan diversity, community assembly, and co-occurrence networks in relation to SMF. RESULTS: SMF was significantly higher at AB12 and AB31 than at AG. Stochastic processes dominated community assembly in all three groups: homogenizing dispersal in bacteria, drift in fungi, and in protists a shift from dispersal limitation at AB03 (90%) to drift at AB12 (100%). Bacterial network complexity was lowest at AB03, fungal complexity increased at AB31, and protistan complexity was unchanged. Partial least squares path modeling (PLS-PM) revealed divergent microbial pathways: fungal diversity and bacterial and protistan network complexity were positively associated with SMF, whereas fungal network complexity and protistan diversity showed negative associations. DISCUSSION: Microbial-SMF linkages thus reflect a strategy of diversity dependence in fungi versus network dependence in bacteria and protists, indicating that assessing alpine grassland restoration requires group-specific rather than universal microbial indicators.