Vegetation restoration types affect soil bacterial community composition and diversity in degraded lands in subtropical of China

Significant improvement of soil quality and biodiversity has been reported following vegetation restoration on the degraded lands in subtropical of China. However, so far the response of soil bacterial communities and drivers of their composition to differing vegetation restoration types are not well understood. In this study, we investigated soil physicochemical properties and bacterial communities in degraded land subjected to differing vegetation restoration types after 12 years of long-term experiment. Restoration types included grassland, cropland, three differing plantation forests (orchard, coniferous forest, and coniferous forest with applied tillage), and control of degraded land. Bacterial community composition was examined using 16S rDNA sequencing. Result found that soil nutrient content includes soil organic carbon (SOC), total N (TN), available nitrogen (AN), available phosphorus (AP), and available potassium (AK) was improved after 12-year restoration and the highest contents were found in cropland. However, soil pH was decreased after revegetation in the order degraded land > grassland > forestland > cropland, and the soil C/N ratio was significantly decreased in cropland. Revegetation restoration significantly increased operational taxonomic units (OTUs), ACE, and Chao1 indices by 13.67-22.81%, 16.34-25.11%, and 14.66-24.00%, with relative abundances of bacterial phyla varying between the different vegetation types. Soil physicochemical properties (e.g. pH, SOC, TN, AN, AP, and AK) showed significant correlations with the majority of the dominant phyla. When degraded land was restored to cropland, soil C/N ratio decreased which promoted the growth of Actinobacteria. Revegetation with grassland and forest increased soil nutrient content and decreased pH, resulting in shifts in bacterial phyla favoring Proteobacteria and Acidobacteria. Our observations show that restoration of degraded land will lead to differing bacterial community compositions depending on the vegetation type.