Effects of biochar incorporation on soil viable and necromass carbon in the luvisol soil

Biochar amendments generally enhance soil organic carbon (SOC) accumulation. Little is known about soil carbon sequestration and stabilization, particularly via the path of living microbial biomass (MBC) and dead microbial biomass (amino sugar tissue C, AS-C) with biochar incorporation. In a maize field trial in north-eastern China, maize straw-derived biochar was applied at four dosages levels of 0, 22.5, 67.5 and 112.5 t center dot ha(-1)(CK, D1, D2 and D3). The SOC, MBC, MBC/SOC (qMB), AS-C (GluN: glucosamine; GalN: galactosamine; and MurA: muramic acid), AS-C/SOC and phospholipid fatty acids (PLFAs) were quantified during five corn-growing stages. The differences between the principal component analysis results of each pair of treatments were significant. The soil MBC, SOC and qMB were significantly linearly correlated with biochar dosage. These results indicate that biochar incorporation still accelerated the microbial C pool and the turnover after 3 years. Biochar addition enhanced the AS-C pools slightly. The addition of biochar increased the fungi and bacteria PLFAs and their ratios, but it only slightly influenced the GluN/MurA. The biochar dosages and growing stages had significant interactive effects on MBC, qMB, GluN-C, MurA-C and AS-C, but not on SOC, GalN-C and AS-C/SOC. The growing stages had significant impacts on all of the indexes, except for GluN/MurA. These results collectively suggest that increasing the biochar amendment dosage further stimulates the microbial activity, particularly that of the fungal communities, while retaining the dead microbial biomass residues and their structural stability.