Abstract: [Objective] In order to provide a reasonable reference for the management regime of natural secondary forests, the carbon source utilization and functional diversity of soil microbial communities were investigated under different forest management regimes of natural secondary forests in northeastern China.[Method] Four forests representing management regimes, traditional forest management(FM1), target tree-based forest management(FM2), conversion to mixed broadleaved-based forest management(FM3) and nonintervention forest management(FM4), were selected in Danqinghe Forestry Farm located in Harbin, Heilongjiang Province. Among them, the traditional forest management (FM1) puts more emphasis on obtaining the woods. Target tree-based forest management (FM2) is mainly based on the crop tree management, the weak interference and natural regeneration of the target trees. Conversion to mixed broadleaved-based forest management (FM3) is a management that new hardwoods are introduced into the original management regime while logging. The nonintervention forest management (FM4) is based on the natural growth without any disturbance. Under each forest management regime, we had 3 sampling plots. Each 50 m×50 m plot was divided into 10 m×10 m quadrats, generating a total of 25 quadrats. The topsoil (0-20 cm) was collected in each quadrate. Based on the Biolog-Eco method, we studied the different characteristics of carbon source utilization and functional diversity in the four forest management regimes, and further explored the effect of soil chemical properties on soil carbon source utilization types.[Result] The carbon source utilization of soil microbial communities in FM1 was significantly lower than those in other three regimes, and it was highest in FM4, while there was no significant difference in soil carbon source utilization between in FM2 and FM3. Soil chemical properties, especially available nitrogen(AN), available potassium(AK), available phosphorus(AP), soil organic carbon(SOC)and carbon-nitrogen ratio(C/N), had significant impact on the carbon source utilization of soil microbial communities. Soil microbial functional diversity, expressed as Simpson index(D), Shannon-Wiener index(H')and McIntosh index(U), had an order of FM4 >FM2 and FM3 >FM1, which might be related to the different tending and thinning treatments among the four natural secondary forests.[Conclusion] The nonintervention forest management(FM4) may be the optimalnatural forest management regime in secondary forest in northeastern China, in term consideration of the utilization and the functional diversity of soil microbial carbon source. However, with comprehensive consideration of the ecological and economic benefits of forest management, as well as the natural regeneration of the tree species, the conversion to mixed broadleaved-based forest management(FM3) would be the best management regime for natural secondary forest in northeastern China.

Key words: forest management regime, natural secondary forest, soil microbe, carbon source utilization, functional diversity