Composition, Spatial And Seasonal Dynamics Of Ground-dwelling Beetle (Insecta: Coleoptera) Communities In Different Vegetation Types In Yeyahu Wetland, Beijing

Ground-dwelling beetle communities(GDBCs) from 32 sampling sites with five main vegetation types,two well-conserved ones and three degradated ones,were investigated in Yeyahu Wetland of Beijing by pitfall traps from April to December,2007,and the influence of wetland degradation and vegetation variation on the composition,spatial distribution pattern and season dynamic of GDBCs was studied at the family level.The results are as follows:1.A total of 11,818 beetle specimens belonging to 40 families were collected in the whole sampling period.Among these,Carabidae and Staphylinidae were dominant,while Anthicidae, Eumolpidae and Lathridiidae were subdominant.2.In the five types of vegetation investigated,the activity density,family level richness and the Shannon-Wiener diversity index(H') of GDBCs were not significantly different between the well-conserved Phragmites communis and Cyperus glomeratus ones.However,the beetle activity density in these two well-conserved vegetations,and the family richness in the Cyperus glomeratus one were almost significantly higher than those of the three degradated ones.3.It was showed by canonical correspondence analysis(CCA) to the relationship between the composition of GDBCs and nine environmental factors,that there was an obviously correspondance between the distribution of the 32 sampling sites in CCA ordination diagram and the vegetation types.The composition of GDBCs was affected synthetically by the wetland degradation and vegetation variation,and soil water content,plant coverage,plant biomass and litter coverage were the major factors affecting on the composition and spatial distribution of GDBCs in the wetland.According to the correlation analysis,I also found that the correlation among beetle activity density and the soil water content,plant biomass and coverage was all significantly positive (P＜0.05 or P＜0.01),and it was between beetle family richness and plant biomass(P＜0.05); while that between the beetle diversity index(H') and plant coverage was significantly negative (P＜0.01).Moreover,in a nonlinear regression analysis,the change of soil water content could explain about 57%of the variation in beetle activity density.The plant density,species richness and diversity index had no significant effect on the composition of GDBCs.A synthetic environmental variable,WBC(Water-Biomass-Coverage),which reflects the situation of soil water content,plant biomass and coverage,was obtained by principal component analysis(PCA) of the nine environmental factors.Well-conserved vegetation types and degradated vegetation types separated significantly along the WBC change gradient.On the basis of relationship between beetle activity density and WBC,the five vegetation types could be divided into three extremely different groups.Our results showed that maintaining appropriate wetland landscapes was vital for beetle protection.4.According to the seasonal dynamics of ground-dwelling beetles,we found that total individual number of ground-dwelling beetles in Yeyahu Wetland varied obviously in different months and reached its peak in April.Then it declined in fluctuation,formed two secondary peaks in June and August.At last,it was lowest in October.The seasonal dynamics of beetle family richness was flat and the family richness reached a peak in June.The beetle activity density and family richness in different vegetation types were highest in April mostly,but the seasonal dynamics were varied.However,it was showed by detrended correspondence analysis to the seasonal dynamics of GDBCs activity density and family richness in 32 sampling sites,the seasonal dynamics of the sites in the same vegetation type were similar mostly.Seasonal dynamics of dominant families and subdominant families activity density in five vegetation types showed that the Hemarthria altissima and degradated Phragmites communis ones were similar,but the two well well-conserved vegetation types were different except for Carabidae.We can seen that the vegetation compositon may be one of the important factors influencing the seasonal dynamics of ground-dwelling beetles in Yeyahu Wetland.