Soil quality assessment of vegetation restoration after a large forest fire in Daxing’anling, northeast China

Forest fires significantly change soil function and quality. Finding an effective way to accelerate the restoration of soil quality after forest fires is a major issue. This study investigated the soil quality index (SQI) during vegetation restoration after a fire in a Larix gmelinii plantation, throughout different restoration years. Fifteen physical, chemical, and biological properties of soil were examined using principal component analysis, and soil quality was assessed by SQI. The results revealed that soil physical properties, chemical properties, and enzyme activities showed the most improvement after 24 yr of restoration. Soil microbial biomass carbon content and microbial biomass nitrogen content increased with restoration years. Soil bulk density, microbial biomass nitrogen, sucrase, and catalase were retained in the minimum data set. After 24 yr of restoration, SQI was the highest, with a value of 0.52, followed by natural restoration, 21, 13, and 16 yr; the SQI after 3 yr of restoration was the lowest, with a value of 0.26. Artificial regeneration accelerated the recovery of soil quality after 24 yr. Soil quality should be monitored continuously in the study area.