Objective  As a small-scale disturbance in the forest ecosystem, the forest gap plays an important role in nutrient cycling and functional diversity of microbial community in the soil of forest. Clarifying the seasonal dynamic response mechanism of soil nutrients and functional diversity of microbial community to the forest size will help to improve the soil ecological environment of Castanopsis kawakamii forests.

  Method  The gaps of C. kawakamii natural forests were used as research objects, and the Biolog micro-plate method was used, combining the regularity of soil physical and chemical properties, carbon source utilization capacity and metabolic characteristics with different size of forest gaps during growing season and non-growing season.

  Result  (1) The soil temperature (ST), available potassium (AK) content in the growing season of the gaps were significantly higher than those in the non-growing season, and pH value, available phosphorus (AP) content were significantly lower than those in the non-growing season. The formation of forest gaps promoted the increase of soil pH value and the accumulation of available potassium (AK), and accelerated the absorption and utilization of alkali-hydrolyzable nitrogen (HN) and available phosphorus (AP) by microorganisms. (2) The average well color development (AWCD) of soil microorganisms in the growing season of the forest gaps was significantly higher than that in the non-growing season in the middle and late cultivation periods. The soil microorganisms of the forest gaps mainly used carboxylic acid, polymer, and amino acid carbon sources in the growing season, and mainly used the carbon sources as amino acid and carboxylic acid carbon sources in the non-growing season. (3) In soil microbial functional diversity indexes of forest gaps, Shannon-Wiener and Pielou indices in the growing season of the forest gaps were significantly higher than those in the non-growing season, and the Simpson index was significantly lower than in the non-growing season. Gap size had no significant effect on the functional diversity index of microbial community during the growing season. The Simpson index of the soil microbial community in the non-growing small forest window was the highest. The Shannon-Wiener index and Pielou index of the medium gaps were the highest. (4) Generalized linear model (GLM) analysis showed that increasing soil temperature (ST) and soil available potassium (AK) in the growing season of the forest gaps were conducive to increasing the dominance of common soil microorganism species. The reduction of soil alkaline nitrogen (HN) content and the increase of available potassium (AK) content in non-growing seasons were conducive to the increase of microbial diversity and uniformity.

  Conclusion  Functionaldiversity of soil microbial community of the forest gaps during the growing season is maintained at a high level, and the soil nutrient cycling efficiency is high. The soil environment of non-gaps during the non-growing season is conducive to the growth and metabolism of soil microorganisms and maintains the function of the soil ecosystem. Heterogeneity of soil temperature and available nutrient content caused by the formation of forest gaps is the main factor affecting the metabolic characteristics and functional diversity of soil microbial communities.