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Organic carbon quality, composition of main microbial groups, enzyme activities, and temperature sensitivity of soil respiration of an acid paddy soil treated with biochar

Chen, Junhui, Chen, De, Xu, Qiufang, Fuhrmann, Jeffry J., Li, Lianqing, Pan, Genxing, Li, Yongfu, Qin, Hua, Liang, Chenfei, Sun, Xuan
Biology and fertility of soils 2019 v.55 no.2 pp. 185-197
acid tolerance, bacteria, biochar, community structure, enzyme activity, fungi, hydrolysis, labile carbon, laboratory experimentation, magnetism, microbial communities, paddy soils, soil amendments, soil enzymes, soil respiration, spectroscopy, sulfuric acid, temperature
The role of soil organic C (SOC) quality affecting microbial community composition and function under biochar application is poorly understood. We investigated the relationship between the pool size and chemical composition of SOC; composition of main microbial groups; enzyme activities involved in C, N, and P cycling; and soil respiration in a rice paddy amended with biochar for 20 months in a laboratory experiment at 15, 25, and 35 °C. Soil labile and recalcitrant organic C pools were determined by a two-step sulfuric acid (H₂SO₄) hydrolysis method. The chemical composition of SOC was determined with ¹³C-nuclear magnetic resonance spectroscopy. The biochar amendment at 20 and 40 t ha⁻¹ significantly decreased the soil labile C pool I (extracted by 5 N H₂SO₄), alkyl, and carbonyl C contents and increased the recalcitrant C pool (acid-resistant) and aromatic C contents and the aromatic C to O-alkyl C ratio. The phospholipid-fatty acid concentrations and soil enzyme activities were unchanged by biochar application at 10 and 20 t ha⁻¹, but both were increased at 40 t ha⁻¹. Biochar increased the ratio of gram-positive (G+) to gram-negative (G−) bacteria and decreased that of fungi to bacteria. The recalcitrant C pool and aromatic C contents were positively correlated to the G+ bacteria abundance and were important factors in shaping composition of the main microbial groups and improving enzyme activities. Biochar application at 40 t ha⁻¹ lowered soil respiration rates at 15 and 25 °C by decreasing labile C pool and increasing C recalcitrancy while increased temperature sensitivities of soil respiration at 25/15 °C and 35/25 °C by stimulating microbial abundance and enzyme activities. Together, our results suggest that biochar soil amendment shifted microbial community composition and function through influencing the composition of SOC.