Forest Wildfire Increases the Seasonal Allocation of Soil Labile Carbon Fractions Due to the Transition from Microbial K- to r-Strategists

Promoting the formation and accumulation of soil carbon (C) is one of the natural solutions to address climate change, but frequent wildfires increase its uncertainty and challenge. This two-year study deciphered the driving pathways of seasonal and vertical patterns in a soil C pool following a wildfire from a microbial perspective. Results showed that total organic C concentration and stock postfire decreased by 29.9 and 17.5% on average compared with the unburned control, respectively, whereas the allocations of labile C increased by 25.1-45.7%. Fire-induced alterations in labile C fractions were complicated due to their significant seasonality and respective sensitivities. Nonetheless, we emphasized that microbial life-history traits were the decisive mediators of variations and that significant positive linkages existed between labile C and microbial r-selected communities. Fire stimulated lower bacterial and fungal copiotroph/oligotroph ratios and higher ribosomal ribonucleic acid operon copy number, shifting microbes from K- to r-strategists. From integrated soil C pool management indices, fire can be concluded to reduce C stability and accelerate C cycling, but whether the recaptured prevalence of K-strategist over time will modify C processes remains unknown. This study provided a stepping stone for future efforts in accurate C predictions and reasonable C management.