Thinning Intensity Effect On Soil Microbial Activity And Functional Diversity In Chinese Fir Plantation

Understanding forest management-associated soil microbial change is central to linkingforest above-and below-ground structure and function. Thinning is an important andwidely-used silvicultural treatment to primarily improve remaining tree growth and standregeneration. However, its effects on soil microbial biomass and functional diversity remainunclear. To study the effect of thinning treatments on soil microorganisms, soils were sampledto measure the soil microbial biomass C, N(MBC, MBN) and BiologTM-ECO substrate usepatterns at different thinning intensity sites, i.e., CK(no thinning), LIT(30%trees removed),HIT(70%trees removed) in autumn, winter, spring, summer from Chinese fir plantations ofLiShui, South-east China, and the reasons that thinning regulates the microorganisms were alsoexplored. The general results were as follows:(1) Significant differences among different thinning intensity were found for soil MBC,MBN and the MBC/MBN radio and the differences differed with season and soil depth.Compared with the control site, high-intensity thinning practice significantly increased soilMBC and MBN whereas light-intensity thinning treatment decreased soil MBC and MBN.Mid-intensity thinning treatment significantly decreased MBC throughout the year andincreased MBN except in winter.(2)For the results of Average Well Color Development (AWCD), soil microbial functionaldiversity index and principal component analysis, soil microbial functional diversity werestrongly influenced by thinning and in a different way depending of the soil layer and season. Ingenerally, The Average Well Color Development (AWCD), which represents soil microbialmetabolic activity, followed the order of LIT>HIT>MIT≈CK and soil microbial functionaldiversity index(Shannon diversity index and Simpson index) followed the order ofLIT>MIT>HIT≈CK. The result of redundancy analysis indicated that Biolog Ecoplatesutilization patterns of carbon substrate correlated with soil temperature, MBC/MBN radio, totalphosphorus and C/N radio.(3)Thinning treaments significantly influenced the activities of catalase, urease,dehydrogenase, acid phosphatase, polyphenol oxidase, invertase, cellulase and have no effecton the activities of peroxidase and β-glucosidase.