Objective  The function restoration of fired forest depends not only on the time of forest fire, but also on the forest fire type and intensity. It has great ecological implications for the reconstruction of forest structure to study soil physicochemical properties in short time period after fire occurrence.

  Method  Soil samples were taken separately during the depth of 0−5 cm and 5−10 cm in the burned area by crown fire and surface fire within one month since the fire occurrence, and then the soils were analyzed for soil microbial biomass, soil enzyme activity, and soil nutrient content. The metabolic entropy of soil microorganisms was estimated based on these analyzed soil properties.

  Result  Forest fire had a great effect on soil biophysical properties at 0−5 cm depth. Compared with forest surface fire, forest crown fire increased soil nutrient content, soil respiration rate (3.85%) and soil extracellular enzyme activities (47.67%), but it decreased the values of soil moisture content (21.95%) and soil microbial biomass carbon (27.98%) and nitrogen (9.65%) content. The result of statistical analysis indicated that forest fire manipulated soil microbial activity via the changed soil nutrient contents.

  Conclusion  Higher values are found in soil nutrient contents, the activities of soil microbial organism and extracellular enzymes in burned sample plots during short time period after forest fire. The crown fire exerts a stronger priming effect on soil biophysical properties especially in soil depth of 0 to 5 cm. The positive correlations of soil nutrient and the activities of soil microbes and enzymes indicate that soil physicochemical properties would get improved with the time of forest fire.