Effects of thinning on spider diversity of an East Asian subtropical plantation forest

Studies examining the effects of forest management on biodiversity in Asia are scarce and conducted mostly in temperate areas. In this study, the effects of the management on the biodiversity of a subtropical plantation forest were assessed by comparing the composition of spiders in Chamaecyparis formosensis plantations located in central Taiwan that received different degrees of thinning. Sampling plots were established in C. formosensis plantation stands receiving no, moderate, and heavy thinning treatments and a nearby natural broadleaf forest. The responses of spider communities in different strata of the plantation forests to thinning treatments varied. Heavy thinning treatment generated lower diversity indices in ground spiders and higher abundances in canopy spiders. Sampling plots in plantation stands receiving various thinning treatments differed in the compositions of ground, understory, and canopy spiders. Such composition variations resulted from abundance changes of ground weavers on the ground and orb weavers in the understory layer, which in turn seemed to be generated by reduced understory vegetation complexity due to the thinning treatments. Results of this study show that although thinning practices do not increase species richness in a subtropical C. formosensis plantation, they can generate alterations in understory vegetation structures which can lead to increased habitat heterogeneity and spider diversity in plantation forests.