The Fauna Composition,Species Diversity And Spatial Distribution Pattern Of Carabid Beetles In Helan Mountain

Helan Mountain is the core area of Alxa-Ordos area,which is one of the six biodiversity centers in China.Study on the carabid beetles biodiversity and its spatial distribution pattern in Helan Mountain has important significance of conservation biology.From July to August in 2015 and 2016,we selected 98 sample plots from the five type habitats such as mountain needle-leaf forest,mountain broadleaf forest,mountain shrub,mountain grassland and piedmont desert grassland of Helan Mountain.The community composition of carabid beetles in different elevation and vertical vegetation zones were investigated by using pitfall trap and hand capturing method.The species composition and diversity of carabid beetles were studied,and the environmental factors such as vegetation,soil types as well as topographic factors were analysed.The aims were to analyze the factors that affect the carabid beetle diversity and its spatial distribution patterns and explain the mechanism of spatial distribution pattern of carabid beetles of Helan Mountain.The main results are presented below:1.A total of 10989 carabid beetles were collected,belonging to 65 species and 21 genera.Of these beetles,the species of Harpalus was the largest among the genera with including 19 species.Poecilus fortipes and Harpalus salinus were the dominant species,accounting for 43.93%and 11.33%of the total individuals.According to the Zoogeographical fauna of the world,37 species were belonged to the Palaearctic Realm and 28 species were belonged to widespread.Pure Oriental species were absent.There were 21 distribution patterns in the Zoogeographical Regions of China.The element of Mongolia-Xinjiang region plays an important role in the carabid beetle fauna and closely related to the Northeast and North China region.Palaearctic species increased gradually with increasing altitude in vertical distribution.2.To analyze the different vegetation zones and three soil types of carabid beetles community diversity,the results showed that species composition and dominant groups varied greatly among different vegetation types.The individual and richness of carabid beetles community were the highest in mountain broadleaf forest habitat.The dominance of carabid beetles community was the highest in mountain needle-leaf forest habitat,and the evenness was the highest in the piedmont desert grassland.The indices of individual,dominance,as well as Shannon-Wiener index were the lowest in the piedmont desert grassland,and which was significant difference between the four habitats.Shannon-Wiener index were a significant difference(P = 0.0328)among Grey cinnamon soil,Sierozem and Rhogosol.3.The relationship between species diversity index and species distribution and terrain factors was analyzed by using the correspondence relation between the canonical(CCA).Using generalized additive model(GAM),the response curves of community diversity index of different habitats to altitudinal gradients was fitted.The altitude,aspect,slope,profile curvature and topographic wetness index were significantly effect on the distribution pattern of carabid beetles diversity.Altitude was the best important effect factor that analysis intensity was the highest.Slope was significantly effect on the distribution of carabid beetles community in mountain coniferous forest and shallow mountain desert habitats.The fitting curve of species richness indices and individuals with antitude was an asymmetric single peak curve.The fitting curve of Shannon-Wiener index with antitude was showed increases at first and tends to be gentle.The fitting curve of evenness index with antitude was showed a "V" trend.