Abstract: To investigate the recovery pattern of soil bacterial community after low intensity fires and its response to fire-deposited charcoal in subtropical forest, we conducted a field experiment with different amounts of charcoal input (charcoal removal (C0), single rate (C1), and double rates of charcoal input (C2) via adding the removed charcoal from C0 plots), and an unburnt area was selected as control (UB), at a harvest site of Pinus massoniana plantation subjected to prescribed burning. Soil samples at the 0-10 cm depth were collected one year and five years after the burning. Soil bacterial community diversity and structure was analyzed using the highthroughput sequencing technology. Soil physicochemical properties were measured to evaluate the potential mechanisms driving the dynamics of soil bacterial community. The results showed that the diversity of soil bacterial community was not affected by either fire or charcoal input (P>0.05). The number of amplicon sequence variants (ASVs) and Chao1 index were significantly lower while Shannon index was significantly higher in soils collected five years after fire than that collected one year after fire (P<0.05). Non-metric multidimensional scaling (NMDS) analysis based on Bray-Curtis distance showed that the structure of bacterial community in C0 and UB soil was significantly different one year after fire (P<0.05), while no difference was observed among the treatments five years after fire (P>0.05). Soil pH was the key factor regulating the changes of soil bacterial community structure, which accounted for 46.3% and 50.5% of the variations in soil bacterial community one and five years after fire, respectively. Acidobacteria, Proteobacteria, Actinobacteria, and Chloroflexi were the most abundant bacterial phyla. The relative abundance of Proteobacteria and Actinobacteria was significantly lower in soils collected five years after fire than that one year after fire, while the opposite trend was found for Firmicutes in C0 and C1 soils (P<0.05). The relative abundance of Gemmatimonadetes was significantly higher in C1 than UB soil. Higher abundance of Firmicutes was observed in C0 and C1 soils than UB soil five years after fire (P<0.05). Collectively, the diversity and structure of soil bacterial community after the low intensity fire can recover to the original level in the short term in subtropical forests. Fire-deposited charcoal exhibits long-term effects on the abundance of specific soil bacterial taxa. Future studies should focus on the temporal dynamics of soil bacterial taxa which regulate soil functions such as carbon and nutrient cycling after fire in subtropical forests.

Key words: broadcast burning, charcoal, soil bacteria, diversity, community structure