Species richness of Cerambycidae in larch plantations and natural broad-leaved forests of the central mountainous region of Japan

Abstract

Species richness of Cerambycidae was investigated and compared among 32 forest stands in the central mountainous region of Japan. The stands comprised five forest types: middle-aged larch forest ( Larix kaempferi (Lamb.) Carrière), old-aged larch forest, recently thinned larch forest, secondary broad-leaved forest, and primary broad-leaved forest. Malaise traps were set deep inside of these stands, and beetles were captured during three 14-day periods, in June, July, and August. Trapped beetles were identified to the species level, and statistical analyses were carried out to determine quantitative and qualitative differences in species richness and composition among these forest types. Ninety-three species, representing 64 genera of Cerambycidae in total, dominated by Pidonia, Pterolophia, Parastrangalis, and Xylotrechus, were captured. The middle-aged larch forest and the primary broad-leaved forest were not significantly different in terms of species number. However, compositions of the beetles in these forest types were different. Pidonia puziloi was a species with a significant indicator value for the latter. Thinning increased the richness of cerambycid species in larch plantations. This management not only increased the number of individuals of species characteristic of larch plantations, but also some species usually found in natural broad-leaved forests. Long rotation for plantations also had some effects on cerambycid composition. The secondary broad-leaved forest had more cerambycid species than either the middle-aged larch forest or the primary forest. Xylotrechus was characteristic of the secondary forest, and Xylotrechus cuneipennis and X. emaciatus had significant indicator values for the secondary forest in comparison with middle-aged larch forest, whereas Pidonia was a genus characteristic of the primary forest. Besides forest type, openness of the canopy and altitude influenced the number of cerambycid species.