Reintroduction of Grassland Plant Species Shapes Soil Bacterial Ecological Groups and Contributes Differently To Bacterial Diversity

The reintroduction of grassland plant species is widely used to restore degraded cropland, yet the species-specific effects on soil microbial diversity remain poorly understood. Understanding how individual plant species shape microbial communities is critical for improving restoration outcomes. To address this, we established experimental plots with 11 plant species on abandoned cropland and evaluated their impacts on soil bacterial diversity. Our results revealed marked variations in soil bacterial diversity across species. Richness indices (ACE and Richness) were positively correlated with soil total phosphorus (TP) and pH, while evenness indices (Simpson and Pielou) were negatively correlated with the proportion of water-stable aggregates (WSA). By classifying soil bacteria into ecological groups via co-occurrence network analysis, we found that bacterial diversity was positively correlated with the relative abundance of keystone and low-frequency taxa, but negatively correlated with peripheral taxa and other taxa. Further analysis indicated that stochastic processes following plant reintroduction promoted the emergence of low-frequency taxa, while deterministic processes contributed to a higher relative abundance of other taxa. Taken together, these findings suggest that species such as Elymus sibiricus (E. sibi) enhance soil bacterial diversity by shifting community assembly toward more stochastic processes, accompanied by an increase in low-frequency taxa and a reduction in the relative abundance of other taxa. Our results provide critical insights for selecting plant species that enhance microbial diversity for the restoration of abandoned cropland. Our study demonstrates a dual-pathway mechanism by which plant species regulate soil bacterial diversity: (i) by modifying soil properties (e.g., pH, TP, WSA), which filter the microbial community; and (ii) by modulating the abundance and assembly of key ecological groups within the microbial network. The selection of plant species determines the balance between these pathways, ultimately shaping the diversity outcome.