Effect of sun exposure on saproxylic beetle assemblages may change with topoclimate in a subtropical forest of east China

Abstract

Sun exposure is an important determinant of diversity and distribution of saproxylic beetles. However, the sun requirement of saproxylic beetles in forests outside of Europe is still poorly known. In this study, we explored the effect of sun exposure on the biodiversity of saproxylic beetles in a subtropical forest of east China. Beetles were sampled from 64 newly cut boles of Pinus taiwanensis and Cryptomeria fortunei which were equally distributed across high-exposed and low-exposed sites on a warm south-facing and a cold north-facing slope (×4 replicates) during 2 years by, respectively, using flight intercept and emergence traps. It was suggested that sun exposure had no significant effect on species richness of saproxylic beetles. Its effect on beetle abundance changed over the season and significantly varied with topoclimate in the colder months of April and May. Species richness and abundance of beetles associated with different trees did not respond differently to sun exposure. Significantly more beetle individuals were trapped on the warm south-facing slope than on the cold north-facing slope, but aspect had no detectable effect on beetle species richness. Beetle assemblages were significantly affected by sun exposure, but tended to be more similar among low-exposed sites across different slopes. In general, our results indicated that sun exposure is not a sufficient indicator of species richness of saproxylic beetles, but may play an important role in retaining the integrity of saproxylic fauna in subtropical forests. The effect of sun exposure on biodiversity of saproxylic beetles is affected by topoclimate variations.