Linking soil organic carbon mineralization with soil variables and bacterial communities in a permafrost-affected tussock wetland during laboratory incubation

Microtopography can cause great soil heterogeneity in both abiotic and biotic factors, which leads to different soil organic matter decomposition rates. However, the quantitative effects of soil variables and microbial properties on soil organic carbon (SOC) mineralization in microfeatures in permafrost wetlands largely remain unknown. Here, soil samples of 0-10 cm from hummocks and hollows in a permafrost-affected tussock wetland were collected for laboratory incubation. The results showed that the temperature sensitivities (Q10 value) of SOC mineralization were 3.14 and 2.44 for hummocks and hollows, respectively. After an 80-day laboratory incubation, the microfeatures had no significant effects on the relative abundance of bacteria, but significantly affected bacterial alpha-diversity (Shannon indices) of soil. The incubation temperature also separated the bacterial community structure of the two microfeatures. Laboratory warming and the microfeatures influenced the SOC mineralization rate by regulating bacterial communities and labile substrates, with a joint contribution of 72 % of the total variances in SOC mineralization. Our study quantified the differences in soil variables, bacterial community indices, and their contribution to SOC mineralization between the two microfeatures in a permafrostaffected wetland, and thus improved our understanding of the microbial processes driving soil carbon cycling in permafrost regions.