Characteristics of soil bacterial communities during ecological restoration of vegetation concrete slopes

Background Soil microorganisms constitute essential components of terrestrial ecosystems, exerting irreplaceable roles in regulating biogeochemical cycles, enhancing soil fertility, and maintaining overall ecosystem stability and functionality. To gain a clear understanding of the structural characteristics and compositional dynamics of soil bacterial communities during the vegetation restoration process of vegetation-concrete slopes, systematic investigations are required, as such insights are critical for unraveling the ecological mechanisms underlying the restoration of these engineered slope environments.Methods This study adopted the space-for-time substitution method, taking the soil from vegetation-concrete slopes with different restoration ages (2a, 6a, 8a, and 21a) in Yichang City as the research objects, and using the soil from natural forest land (NF) as the control. Conventional analytical methods were used to determine the changes in soil environmental factors. Combined with high-throughput sequencing technology, the structure and diversity characteristics of soil bacterial communities were analyzed, and the functions of soil bacterial communities were predicted. The purpose of this study is to reveal the dynamic evolution characteristics of soil ecosystems during the restoration process of vegetation-concrete slopes. Results 1）Significant differences were observed in soil environmental factors across vegetation-concrete slopes with varying restoration periods. Soil pH values at all sampling sites ranged from 7.51 to 8.02, indicating weakly alkaline characteristics. With increasing restoration duration, soil organic carbon (SOC), total nitrogen (TN), available nitrogen (AN), available phosphorus (AP), and available potassium (AK) all exhibited an initial decrease followed by subsequent increase. Conversely, total phosphorus (TP) and total potassium (TK) demonstrated an opposite evolutionary pattern, showing an initial increase followed by decrease as the restoration period extended. 2）Proteobacteria（26.84%）, Acidobacteria（23.41%）, Actinobacteria（8.57%）, and Chloroflexi（6.88%） were the dominant bacterial phyla during the vegetation restoration process of vegetation-concrete slopes, accounting for more than 60% of the total bacterial community. The α-diversity of the bacterial community reached relatively high levels at the 6a and 8a of restoration, with the lowest diversity observed at the 2a. Principal Coordinate Analysis (PCoA) indicated that there were significant differences in soil bacterial communities among different restoration ages ( <italic>p</italic>=0.001). 3）PICRUSt2 functional prediction analysis revealed that the bacterial community functions encompassed 6 level-1 functional categories and 45 level-2 functional subcategories, with metabolism identified as the core level-1 function.4）The effects of soil environmental factors on the dominant bacterial phyla varied significantly across different restoration ages. Redundancy Analysis (RDA) demonstrated that soil pH, available nitrogen (AN), and available potassium (AK) were the main environmental factors influencing the structure of the soil bacterial community, exerting significant regulatory effects on the composition and distribution of bacterial communities. Conclusion Using high-throughput sequencing technology and bioinformatics analysis methods, this study systematically revealed the dynamic variation patterns of soil microbial community structure, diversity, and functional characteristics during the ecological restoration process of vegetation-concrete slopes. These findings enrich the theory regarding the distribution patterns of microbial diversity in vegetation-concrete slopes, provide important theoretical basis and practical guidance for the subsequent optimization of slope ecological restoration technologies based on microbial regulation, and hold significant application value especially in key links such as microbial agent screening, substrate improvement, and vegetation configuration.