Abstract: Unreasonable forest management has been proposed as an important causation for the decline of saproxylic beetle diversity. In subtropical regions of China, plantation forests have been widely established to replace natural forests with high diversity. However, our knowledge about the impact of these plantation forests on saproxylic beetle diversity is still very poor. In this study, we compared the composition and diversity of saproxylic beetle assemblages associated with snags of Chinese cedar (Cryptomeria fortunei) in young cedar plantation (YPF) (30-40 year), mature cedar plantation (MPF) (80-100 year), and semi-natural mixed forests (SNMF) (>200 year) in Tianmushan Nature Reserve, Zhejiang province. The results showed that the number of saproxylic beetle individuals was significantly higher in SNMF (97.4±66.7) (mean±SD) than in YPF (39.9±16.3) and MPF (21.9±5.9). However, no significant difference in species richness was found between SNMF (27.9±11.2) and YPF (24.1±3.7). In contrast, the numbers of species and individuals were significantly higher in YPF than in MPF (P<0.05). Both species richness and abundance were significantly related to the volume of coarse woody debris (CWD) in surveyed plots (P<0.05). The canonical correspondence analysis and multi-response permutation procedure analysis confirmed that the saproxylic beetle assemblages were significantly different between forest types (P<0.001). The diameter of sampled snags, CWD diameter and amount, and canopy cover in plots had significant effects on species composition (P<0.05). Analysis of trophic composition also indicated that mycetophagous species were significantly more abundant in SNMF than in plantation forests (P<0.001). The results suggest that improving quantity and quality of CWD habitats in cedar plantations may increase species richness of saproxylic beetles, but the diversity of saproxylic beetles in these plantations may decline in later succession stage. Furthermore, saproxylic beetle assemblages in cedar plantations may remain distinct from those in natural forests.

Key words: Saproxylic beetles, species diversity, Chinese cedar, management history, plantation forest, coarse woody debris, Tianmushan