Species Diversity And Habitat Distribution Of Carabid (Coleoptera: Carabidae) In Ziwuling Forest Region Of Gansu Province

The carabid beetle (Coleoptera.Carabidae) is incapable of flying with leg crawling. Its distributions are limited and show close relation to certain habitats. We investigate species diversity and habitat distribution of carabid beetle and use them as indicators in monitoring environmental changes, to see how these changes would affect spatial distribution patterns and local biodiversity in a more general sense. This study was conducted in Ziwuling forest region (35° 18 ' -36° 39 ' N,107° 59 ' -108° 43 ' E) of Gansu province, northwest China. The Ziwuling secondary forest region of China is located at a transitional area where the semi-humid climate is changing into the semi-arid and arid climate. Because of both natural and man-induced cause, up to now, the Ziwuling secondary forest region is being a habitat fragmentation landscape.Five habitat types were classified based on altitude, climate, soil and vegetation differences: coniferous forest, coniferous broad-leaved mixed forest, broad-leaved forest, shrubs, meadow and crop field. Sixteen plots within sex different habitats were investigates and the method of pitfall traps was employed in the study. Field collection were done regularly, three times each month from April through October in the years of 2003 to 2004. Of the total collection of 2983 specimens in this region, 36 species of 18 genera in 4 subfamilies were identified, carabid species of subfamily reduced in the following sequence: Harpalinae (24 spp.), Carabinae(9 spp.), Scaritinae(2. spp,) and Brachininae(1 species). The most species-rich genera were Harpalus (7 spp.), Chlaenius (7 spp.), and Carabus (4 spp.).36 species of carabid beetles were collected, of which eleven species, Calosoma maximowiczi, Campalita chinense, Anoplogenius cyanescens, Anisodactylus signatus, Harpalus calceatus, H.jureceki, H. griseus, Chlaenius inops, Chmicans, Calathus halensis and Amara plebeja each accounted for 5%~7% of total specimens; they were the commonly occurred species in this region. Six other species, Carabus brandti, Carabus brandti, Scarites terricola, Stenolophus connotatus, Harpalus sinicus, H. captio, H. simplicidens and Chlaenius spoliatus each accounted for 2%~4.9% of total specimens; they were the incidentally occurred species in this region. Eighteen residual species, each accounted less than 1.67% of total specimens and were rare.Species abundance, Species diversity (Shannon-Wiener index H ),and species composition similarity (Jaccard index) were calculated for the six habitat type. With respect to species number and their abundance, broad-leaved forest habitats were shown to be higher than those habitats, crop fields were the lowest. Species diversity (H ) increased in the following sequence: broad-leaved forests (H =2.3287), coniferous broad-leaved mixed forests(H'=2.0958), coniferous forests (H=1.9948), shrubs (H =1.4568), meadows(H =0.6578), and crop fields (H =0.3877). In contrast, evenness value was highest in broads-leaved forest habitats and lowest in crop field habitats. The carabid species composition between broad-leaved forests and coniferous broad-leaved mixed forests had the highest similarity (Jaecard index=0.8065), with the second highest similarity between meadows and crop fields (Jaccard index=0,6364), and the lowest similarity between coniferous forests and crop fields. Severe disturbance from intensive human and natural activity strongly limited species distributions and abundance. The highest species number was observed in habitat with a moderate degree of disturbance, and the highest abundance was found where disturbance existed in a much lower degree. Habitats in very stable and undisturbed ecosystems did not show the highest number of species and abundance. A positive correlation is seen between precipitation and carabid species diversity and evenness, and a positive correlation is one exhibited between precipitation and individual numbers. Species abundance does not show such patterns. Analysis showed significant habitat preferences for commonly species: Calosoma maximowiczi was more abundant in shrub, Anoplogenius cyanescem in coniferous broad-leaved mixed forest, Calathus halensis and Campalita chinense were more abundant in broad-leaved forest and coniferous broad-leaved mixed forest, Harpalus calceatus was more abundant in crop field, Harpalus jureceki in broad-leaved forest. The results indicate that habitat type and disturbance determine the species distribution of carabid beetle, and habitat differences strongly modify numbers of each species. For species diversity protection, it is very important to maintain environmental heterogeneity and reduce the magnitude of disturbance from human and natural activity in Ziwuling secondary forest region.