A reduction of dung-beetle community diversity caused by an increasing sika deer population in the ohdalgahara subalpine plateau

Abstract

The Ohdaigahara subalpine plateau has recently suffered deforestation caused by an increasing population of sika deer (Cervus nippon), which stripe the bark of many coniferous trees and browse seedlings. Deforested area has been transformed to forest with the floor dominated by Sasa nipponica and grassland densely covered by S. nipponica, which has a tolerance to heavy browsing by sika deer. Hence, deforestation involves an increase in dung supply because S. nipponica contains rich protain and is a major forage of sika deer. To examine the effects of deforestation on the dung-beetle community in the plateau, we compared the diversity of dung-beetle assemblages in the primary forest, transition forest, and S. nipponica grassland using dung-baited pitfall traps. The primary forest had the highest species richness, evenness (Smith-Wilson index, Evar) and species diversity (Shannon-Wiener index, H )of dung beetles. The transition forest showed the greatest abundance but lowest evenness of dung beetles. The S. nipponica grassland had the lowest species richness and species diversity. These results suggest that loss of primary forest resulting from an increasing deer population decreases the diversity of the dung-beetle community. Deforestation in the Ohdaigahara subalpine plateau, therefore, is unfavorable from the viewpoint of biodiversity conservation even though it would increase the abundance of dung beetles.