Study On The Features Of Soil Scarab (Scarabaeoidea) Community In Inner Mongolia Median Region

Soil scarab (Scarabaeoidea) is an important group of Coleoptera. They have a rich species distribution in temperate zone. Most of them have important economic and ecological value. In this paper, the features of soil scarab community, species diversity, the responses to the changes of grazing pressures, as well as their functions in the material cycle of grazing ecosystem were studied.1. In Inner Mongolia median region, we chose 7 habitats as the sampling sites. They are typical steppe, meadow steppe, sandy land, desert steppe, farmland, quit ploughing farmland and artificial woodland. During the 2003-2004 sampling period, a total of 8 families, 24 genera, 77 species have been collected. Among them, there are shytophagous scarab beetles belonging to 3 families, 14 genera, 22 species, and coprophagous and saprophagous scarab beetles of 5 families, 10 genera, 55 species. Eurychoric species are the soil scarabs which individual number is higher. The individual number of stenochoric species is lower. There are no stenochoric species which individual number is comparatively higher. Among the eurychoric species, there are someone which can select distributing in fix habitats. The result of factor analysis showed that 7 soil scarab communities can divided into 2 kinds. One includes the soil scarab communities of typical steppe, meadow steppe, sandy land and desert steppe, another is composed by the soil scarab communities of farmland, quit ploughing farmland and artificial woodland.2. The dominant species of soil scarab community are Aphodius sp16, A. rectus Motschlsky and A. sp21. Onthophagus gibbulus(Pallas), O.marginalis nigrimargo Goidanish, O. bivertex Heyden and A. erratcus (L.) are the common species of the soil scarab community. Species compositions of different soil scarab communities are approximately same. The main differences are that they have different common species and rare species.According to the features of spatial distribution, all of the coprophagous and saprophagous scarab beetles can be divided into 5 groups: ① grassland species, such as A. sp16, O. marginalis mgrimargo Goidanish, A. erratcus (L.) and O. bivertex Heyden, etc. ② sandy land species, such as O. sp1, O. sinicus Zhang et Wang, Ochodaeus ferrugineus Eschscholtz, Scarabaeus typhon Fischer, ete. ③desert steppe species, such as Geotrupidius sp. ④farmland species, such as Arectus Motschlsky, A. sp21, A. sp1, A. sp9, A. sp20, Copra ochus Motschulsky, ete. ⑤eurychoric species, suchas O. gibbulus(Pal\as), A.According to the occurring time of the coprophagous and saprophagous scarab beetles, they can be divided into 4 groups: occurring in spring, such as A. sp>6^ O. marginalis nigrimargo Goidanish^ Ceratophyus polyceros(?a\las), etc. ? occurring in summer, such as A. spi9, A. erraticus (L.), A. sp3, Geotrupes stercorarius(L.), O. spi, Gymnopleurus mopsus(Pallas), etc. ?occurring in autumn, such as A. rectus Motschlsky, A. sp2i, A. SP20, A. spi, A. sp9, O. sinicus Zhang et Wang, A. hctroldianus Balthasar, etc. ?occurring in all the year, such as O. bivertex Heyden, O. gibbulus (Pallas), Ceratophyus fischeri Fischeri, 4- sp22, etc.3. The soil scarab species-dominance curves in typical steppe and sandy land are mostly representation. They are reasonable in utilizing environmental resources, the condition of species competition, collocating for the species niches. They are the fitness environments for the soil scarab communities. It is the reverse conditions that aridity condition in desert steppe and shade condition in artificial woodland are the main restricting factors for the development of soil scarab community.Typical steppe possess of the bigger area in temperate zone. It has a longer time for the succession. The sandy land is the intrazonal habitat in the study region. The environmental conditions are atrocious than that of temperate grassland. The spatial heterogeneity of topographty is higher. So the community stability and species diversity of soil scarab are all relatively higher in the two habitats. Comparing to the grassland sampling sites, farmland and artificial woodland are in different climatic region and human activities are high frequency. The species diversities are relatively lower. The or *er of favorableness of ecological factors for the occurring of soil scarab is annual rainfall > humidity > >\Q°C accumulated temperature of annual > altitude.4. The spatial and time niches of main soil scarab species are obviously different-tiation. They -occupied the special niches in habitats. The indice of the common species niche breadth are bigger. On the other hand, degrees of their spatial niches overlap are more. According to the spatial niches differentiation of main species, they can divided into three groups. One of them mainly distributed in grassland habitat, such as Aphodius spi6- The other group mainly distributed in farmland, such as Aphodius sp2i- Third group distributed in sandy land habitat, such as Onthophagus bivertex Heyden.5. As the grazing pressure increased, the individual number of soil scarab will decrease. Another obviously tendency is that as the grazing pressure increase the dominance of main species and the composition of rare species will change. The species diversity will increase and the similarity of soil scarab community will decrease. The effects of grazing activity on the guild III and IV are larger than on the guild I and II. Following species are all sensitivity to the grazing activity: A.erraticus(L.), A. rectos Motschlsk, O. gibbulus(Pallas), Gymnopleurus j?qpiswar(Pallas), O. marginalis nigrimargo Goidanish, 0. bivertex Heyden.With the Indicator Value Method (IndVat), we can choose the bioindicators for the changes of environment that caused by some factors. For the degeneration of the steppe that caused by grazing activity, A. sp4, A. spa and Ceratophyus fischeri Fischeri can be used as characteristic species. Following species can be used as detector species: 0. spi, A. spi6, A. sp22, O. marginalis nigrimargo Goidanish, O. gibbulus(Pdllas), A. sp9, A. spn.6. The bio-enrichment of different chemical element is different in soil scarab. Comparatively, the amount of K bio-enrichment in soil scarab is higher, and the amount of Cu bio-enrichment is lower. Because the biomass of soil scarab is different in different habitats, so the amount of chemical element bio-enrichment is different In typical steppe and farmland, the amount of bio-enrichment is higher man that of in desert steppe.Mammal feces can be the pools of material in grazing ecosystem. Two factors can effect its material releasing. They are biotie factors and abiotic factors. As the biotic factor, soil scarab can intake the material into their body. Through activating in the mammal feces to change its physical constructions, and regulating its process of decomposition.