Abstract: The broad-leaved Korean pine forest in the Xiaoxing'an Mountains is representative of temperate mixed coniferous and broad-leaved forests. In this study, we selected burned area of broad-leaved Korean pine forest and the adjacent unburned area (control) to investigate soil physicochemical properties, enzyme activities, and microbial characteristics after 28 years natural recovery. We further analyzed the main soil factors influencing enzyme activities and microbial communities. The results showed that: 1) soil total nitrogen, alkali-hydrolyzable nitrogen, and water content in the burned area were significantly lower than the control by 28.0%, 39.3% and 4.5%, respectively. However, the activities of catalase, restriction endonuclease, urease, nitrate reductase, and soil dehydrogenase were significantly increased. 2) The α- and β-diversity of soil bacterial and fungal communities in the burned area was not different from those of the control after 28 years recovery, but marked differences were observed in community composition at phylum and genus levels. 3) Redundancy analysis and structural equation modeling revealed that soil pH was the primary factor influencing enzyme activities and microbial communities. 4) After 28 years, the stability and complexity of soil bacterial network in the burned area increased, while the fungal network showed an opposite trend. These results suggested that forest fires have long-term effects on soils, with soil physicochemical properties, enzyme activities, and microbial communities exhibiting distinct post-fire recovery patterns.

Key words: burned area, soil physicochemical properties, enzyme activity, soil microbial community, long-term effects