Rhizosphere microbial α diversity dominates network complexity in governing soil multifunctionality during alpine grassland restoration

Abstract

This study aims to reveal the successional patterns of rhizosphere microbial α diversity and network complexity during alpine grassland restoration, and to elucidate the underlying underground biological mechanisms driving the enhancement of soil multifunctionality. Focusing on the constructive species Kobresia pygmaea in alpine grasslands, this study selected artificial grasslands at various restoration stages (2000s, 2006s, 2013s, and 2018s), with natural alpine meadows (AM) and degraded bare grassland (black soil beach, BOBG) serving as controls. By analyzing plant biomass allocation, soil microbial diversity, microbial co-occurrence network structures, soil multifunctionality indices, and structural equation modeling (SEM), the study systematically characterized the successional shifts in soil microbial α diversity and network complexity, as well as their impacts on soil multifunctionality throughout the restoration of artificial grasslands. With increasing restoration age, plant resource allocation gradually shifted from aboveground tissues to root systems. Soil bacterial and fungal α diversity, microbial network complexity, and soil multifunctionality increased significantly along the restoration gradient. With the extension of restoration time, microbial networks exhibited increased complexity; however, relatively simplified network structures were observed in severely degraded grasslands and those with shorter recovery durations. Soil multifunctionality was significantly positively associated with bacterial α diversity. Compared with fungal diversity, bacterial α diversity showed a higher relative importance in explaining variations in soil multifunctionality. These results highlight the importance of soil bacterial α diversity for soil multifunctionality in sown grassland ecosystems.