Effects of livestock overgrazing on the relationships between plant and microbial diversity across the temperate steppes in northern China

Livestock overgrazing has led to worldwide grassland degradation, posing a significant threat to plant and soil microbial diversity. However, little is known about whether livestock overgrazing influences plant and soil microbial diversity linkages. We examined relationships between plant and soil microbial beta diversity in eight pairs of ungrazed and overgrazed sites across temperate steppes in northern China. Our results revealed a positive correlation between plant and microbial beta diversity across ungrazed grasslands, and overgrazing did not change this relationship. However, different mechanisms underlay the correlations between plant and microbial beta diversity in ungrazed and overgrazed grasslands. In ungrazed grasslands, plant and microbial diversity associations were maintained mainly due to their similar responses to the shared environmental factors. While in overgrazed grasslands, the maintenance of plant and microbial diversity associations was primarily due to their functional associations. Furthermore, the positive links between plant species and microbial taxa increased in overgrazed grasslands, indicating that more soil microbial taxa form close associations with plant species in overgrazed grasslands. Our work provides new insights regarding the mechanisms of plant and microbial communities that associate under different ecological contexts, ultimately suggesting that the functional associations of plant and microbial communities are tighter as grazing intensifies in grasslands.