Effects of re-vegetation restoration on soil bacterial community structure in degraded land in subtropical China

Ecosystem degradation is one of the most pressing environmental problems in the world. Re-vegetation is the major method in land restoration, playing an important role in improving soil quality and biodiversity. Bacteria constitute a vital part of terrestrial ecosystems; however, the relationship between bacteria and restoration of degraded land is not well understood. In this study, we investigated how restoration of degraded land impacts soil physicochemical properties and soil bacterial communities 7, 17, 23 and 35 years after re-vegetation, along with an adjacent control of degraded land. Results showed increases in OTUs, Chao1 and Shannon indices by 54.7%-69.7%, 55.6%-66.0% and 13.5%-17.8% after restoration, with Proteobacteria, Acidobacteria, Chloroflexi and Actinobacteria being the dominant phyla in the study area. Bacterial diversity increased, more strongly during the initial 7 years, but continuous until 35 years. There were positive correlation between the number of OTUs, the Chao1 and Shannon indices and soil nutrients, indicating that improved nutrient contents after restoration was an important driver of bacterial richness and diversity. Vegetation restoration increased the relative abundance of Alphaproteobacteria by 55.9%-118%, especially the genus Bradyrhizobium, which doubled. The relative abundance of Nitrospira (a nitrite-oxidizing bacterial group) was very low ( < 0.1%), corresponding well with the low NO3--N content (less than 1.4 mg kg(-1) soil) in all soil samples, despite increasing soil organic carbon and total nitrogen levels with vegetation restoration age. The results indicated that vegetation restorations have positive effects on the richness and diversity of soil bacteria, and that these effects are the most pronounced during the first 7 years after restoration.