Responses of Legume‐Associated Rhizobacterial Communities to Plant Diversity and Soil Traits in Alpine Grassland

Abstract

Legume species are essential components of plant diversity and affect soil biodiversity across various ecosystems. Their effect on the diversity and traits of soil bacteria, particularly in degraded grasslands, remains unknown. This study analysed the relationships among plant diversity, soil traits and legume‐associated rhizobacterial communities in Xiahe (XH) and Maqu (MQ) in Gansu Province, Haibei (HB) in Qinghai Province and Hongyuan (HY) in Sichuan Province in the eastern Qinghai‐Tibetan Plateau (QTP). The diversity index values (coverage, richness, Shannon index and evenness) of legume species were positively correlated with plant diversity. Several soil nutrients (ammonia‐nitrogen, nitrate‐nitrogen, total nitrogen, available potassium, available phosphorus and soil organic matter) and enzymes (urease, sucrase, peroxidase and dehydrogenase) were lower in HB and HY than in XH and MQ. The Shannon index for rhizobacterial diversity was higher in HB and HY than in XH and MQ. In contrast, the diversity index values were higher for geographical locations than for sympatric plant species. Additionally, HB and HY showed 50% fewer positive and negative associations with rhizobacteria than XH and MQ. Functional Annotation of Prokaryotic Taxa analysis indicated a higher relative abundance of nitrate reduction occurred in HB and HY than in XH and MQ, whereas nitrogen fixation occurred at a lower level in HB and HY than in XH and MQ. The Simpson index value for bacterial diversity was positively correlated with plant diversity, legume species diversity and soil multifunctionality. However, the Shannon index value was negatively correlated with these parameters. Changes in the composition of legume‐associated rhizobacteria across different geographical locations are strongly influenced by plant diversity and soil nutrients, reflecting the distribution characteristics of legumes in alpine grasslands.