Post‐fire soil extracellular enzyme activities in subtropical‐warm temperate climate transitional forests

Wildfire impacts on soil microbial community structure and functional activity have attracted a growing attention because of the higher sensitivity of soil microbes to wildfire. Soil extracellular enzymes play pivotal roles in biogeochemical processes, such as mediating carbon (C) and nutrient cycling. However, little is known about how post-fire changes in soil biogeochemical properties and microbial community composition affect soil extracellular enzyme activities. This study explored the responses and regulating factors of C-, nitrogen-(N), and phosphorus-(P) acquiring extracellular enzyme activities across a wildfire chronosequence (i.e., 1, 6, 13, and 50 years after fire) in subtropical-temperate ecotonal forests in Central China. The activities of C-(beta-glucosidase), N-(N-acetylglucosaminidase), and P-(acid phosphatase) acquiring enzymes declined with time post-fire, with the highest values one-year post-fire. The response of C-acquiring enzyme activity to fire was positively correlated with bacterial biomass, suggesting that microbial compositions were related to post-fire changes in extracellular enzyme decomposition. The response of N-acquiring enzyme activity to fire was positively correlated with soil P availability, while P-acquiring enzyme activity was positively correlated with soil N availability. Overall, soil extracellular enzyme activity declined with time post-fire, suggesting wildfire may reduce microbial demand for nutrients over time. Future research is needed to elucidate fire impacts on microbial processes for nutrient-microbial-enzyme linkages.