Bacterial community structure shifts induced by biochar amendment to karst calcareous soil in southwestern areas of China

PurposeBiochar as a promising soil amendment is poorly explored on the coarse and infertile karst soils in the ecological restoration region. The aim of this study is to ameliorate soil microbial and nutrient conditions in karst areas of southwestern China based on biochar's soil amendment potential.Materials and methodsA pot experiment with black locust (Robinia pseudoacacia) was conducted to test the effects of the biochar amendment (i.e., with five loads as follows: 0, 0.5, 1, 2, and 4% mass ratio of biochar to soil) on the soil enzyme activities, soil pH, nutrient content as well as the bacterial community diversity and composition.Results and discussionOur results showed that the carbon, nitrogen, and phosphorous contents in the soil microbial biomass increased with the biochar addition rate. Soil enzyme activities, soil nutrient content, and pH increased after biochar addition and exhibited highest values at higher biochar treatment (2 and 4% loads). Biochar addition had no effects on the soil bacterial richness (according to the Chao1 index) and diversity (Shannon and Simpson indices). Treatments with higher biochar addition rates (2 and 4% loads) had distinct bacterial groups compared to the lower ones (0, 0.5, and 1% loads) both at the phylum and genus taxonomic levels. Biochar addition significantly increased the relative abundance of phylum Actinobacteria, Bacteroidetes, and Chloroflexi. Moreover, the soil enzyme activity and microbial biomass were strongly correlated with some specific microorganisms.ConclusionsIn conclusion, this study demonstrated that the addition of biochar changed the soil bacterial community structure in calcareous karst soil.