Change in composition and function of microbial communities in an acid bamboo (Phyllostachys praecox) plantation soil with the addition of three different biochars

Biochar has been known as means to increase soil carbon (C) storage, and at the same time to ameliorate soil acidity and enhance plant growth. However, how biochar addition affects microbial community composition and metabolic function in subtropical plantation soils and their linkage with soil quality change is still poorly understood. We selected bamboo stick, corn straw and peel of Carya cathayensis as feedstocks to produce three biochars at 350 °C by slow pyrolysis, and added them to an acid bamboo (Phyllostachys praecox) plantation soil. Changes in soil nutrient and C availability, soil acidity, plant biomass, and microbial function in terms of C source utilization and soil enzyme activities were investigated after a three-month greenhouse trial. The results showed that the biochars from corn straw and peel significantly increased plant biomass, soil pH, organic C, total nitrogen (N) and dissolved organic N contents, while decreased exchangeable H⁺ and exchangeable Al³⁺ concentrations. The concentration of total phospholipid fatty acids (PLFAs) was increased significantly under biochars from corn straw and peel. The activities of β-D-cellobiosidase, N-acetylglucosaminidase and acid phosphatase were significantly increased by peel biochar. Soil basal respiration and microbial utilization rate of carbohydrates, carboxylic acids and amino acids compounds were significantly increased under the three biochars, suggesting a higher capacity of biochar-treated soil to catabolize C sources. Increased plant biomass was related to the increased N availability and decreased acidity. Our study suggests that biochar–induced changes in soil acidity and soil nutrient availability are key drivers shaping the composition of microbial communities and enhancing their catabolic capacity, but the effects on soil microbial function vary depending on feedstock origins.