Abstract:

This paper studies the influences of edge effect on ground-dwelling beetles (Coleoptera) across a forestgrassland ecotone, where the forest interior, the forest-grassland edge and the grassland are compared using beetle diversity (abundance and composition in family level) as the main indicator. The study was conducted in Wolong Natural Reserve (102°52′-103°24′E, 30°45′-31°25′N), Sichuan, Southwest China. Beetles were collected with pitfall traps in 45 plots along five replicated transects extending 100 m from the edge into the forest interior and 100 m into the grassland, with a 25 m interval between different plots. During the field research, a total of 4 736 beetles were collected. Of these beetles belonging to 28 families, Carabidae comprised 49.5%, Staphylinidae 23.5%, and Elateridae 13.0% of the total, being considered as dominant groups. From forest interior to forest edge and then to grassland, family abundance decreased in sequence, but family diversity and evenness increased in sequence. Based on the family composition and abundance, ground-dwelling beetles from the forest interior and those from the grassland were separated from each other by PCoA ordinations; but the beetle assemblages in the forest edge were similar to those found in both the forest interior and grassland, suggesting that the beetle assemblages on the forest edge were dispersed from both of the two adjacent habitats. Seasonal dynamics of family richness and abundance in the forest edge were more similar to the forest interior than to grassland. Predators and scavengers of grounddwelling beetles showed the similar seasonal changes between the forest interior and edge, while the seasonal variation of the phytophagous in the forest edge was more similar to that in grassland. Multiple linear regression analyses showed that litter cover was the most important factor determining the family diversity and evenness of ground-dwelling beetles, and litter depth and canopy cover affected the family abundance. The results indicated the forest edge had obviously different composition of ground-dwelling beetles from that in forest interior at the family level. Since increasing forest fragmentation would result in more edge, it is so necessary to preserve a large enough area of undisturbed deciduous broad-leaved forest for protecting the diversity of ground-dwelling beetles.

Key words: Ground-dwelling beetles, edge effect, diversity, ecotone, forest fragmentation, Wolong Natural Reserve