Abstract: Wildfires in forests impact soil nutrient contents, and thus influence vegetation restoration and the ecological balance of soil. Therefore, it is crucial to explore the impact of wildfires on soil chemical and microbial properties. We compared soil properties between current-year burned areas and adjacent unburned forests in the Da Xing’anling Mountains. Using paired sample t-tests, we analyzed the changes in soil nutrient contents and microbial characteristics in response to wildfire disturbances. The results showed that wildfire significantly increased the contents of ammonium, available phosphorus and microbial biomass phosphorus by 80.6%, 14.6%, and 14.1%, respectively. In contrast, microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), the ratios of MBC to microbial biomass phosphorus (MBP) and MBN to MBP decreased by 25.4%, 39.8%, 29.9%, and 45.9%, respectively. Both redundancy analysis and linear fitting analysis indicated that total phosphorus, ammonium, soil N∶P, and microbial biomass C-N-P stoichiometric ratio were significantly correlated with soil enzyme activities. Additionally, multiple regression analysis revealed that soil total phosphorus and carbon positively influenced the exoglucanase activity, with total phosphorus exhibiting the highest explanatory variation. Overall, this study found that wildfires contribute to the accumulation of available nutrients in soils in the short term primarily due to the return of nutrients from litters and trees after fires. However, wildfires may compromise the sustainable nutrient storage and ecological stability of soils in the long term. Therefore, it is necessary to remove high-risk litters to reduce the occurrence of forest fires.

Key words: burned area, forest soil, soil nutrient, microbial biomass, enzyme activity