Study On The Dynamics And Community Structure Of Macrofauna At Different Succession Stages In Songnen Grassland

The sampling sites chosen for this study included four plant communities at diffferent succession stages in Songnen grassland, Changling district, Jilin Province, namely Suaeda salsa community, Chloris virgata community, Leymus chinensis +Chloris virgata community, Leymus chinensis community.The soil fauna, captured in the six months of a year, amounted to 76 in group, 7,498 in number, falling into 3 phylum, 6class, 17order, 62 family.The number of total macrofauna groups in Chloris virgata community was higher than that in Suaeda salsa community, that in Leymus chinensis community was higher than that in Chloris virgata community and that in Leymus chinensis +Chloris virgata community was higher than that in Leymus chinensis community. In the respect of total density distribution,density of macrofauna in Suaeda salsa community was higher than that in Chloris virgata community, that in Leymus chinensis community was higher than that in Suaeda salsa community and that in Leymus chinensis +Chloris virgata community was higher than that in Leymus chinensis community. The Suaeda salsa community was inferior to the other three communities and the horizontal distribution of soil fauna was unequal. The characteristic of vertical distribution was that the density and the number of groups of macrofauna decrease with the increasing of soil depth. Soil fauna were always assembled on surface layer. The contrary distributing was obvious in Curculionidae larva.In conclusion, the number of macrofauna groups and the population density of macrofauna in this region had the same seasonal variation which varied according to hydrothermal factors. The individual number of soil fauna was small and increased slow in May and June. It was much propitious to soil fauna in July and Autumn because the temperature and the humidity were increasing gradually and the habitat was better, the maximum individual population appeared in August. Then the population of soil fauna became decrease as the soil temperature and soil moisture descend.Density-group index was ideal in diversity comparing of a number of soil animal communities. The density-group index of soil fauna community in Leymus chinensis community was larger than that in Leymus chinensis +Chloris virgata community, that in Leymus chinensis +Chloris virgata community was larger than Chloris virgata community, and that in Suaeda salsa community was lowest. Jaccard index and Grower index showed different results.The analysis of the correlation between density and the number of groups of soil fauna and soil environmental essential factors showed that the correlation between density and the number of groups and soil environmental essential factors is obvious, namely soil humidity, soil pH and organic matter.