Dynamic Of Soil Mesofauna Communities In Different Vegetation Succession Stages In Songnen Grassland

Soil animals play an important role in grassland ecosystem, which are important consumer and special decomposer, and the role of them is irreplaceable. There are complex interactions between soil fauna and plant communities. The succession of plant communities in aboveground could influence on the soil fauna in belowground. Converse, soil fauna in belowground could affect the form of soil organic matter through their activities, feeding and metabolism, and the structure and physiochemical properties of soil, and consequently plant growth, community structure and succession.The present study focused on the dynamic of soil mesofauna in four plant succession communities of Suaeda glauca, Chloris virgata, Chloris virgata +Leymus chinensis,and Leymus chinensis, and discussed the relationship between soil mesofauna and environmental factors. We investigated the soil mesofauna in soil consisted three horizons(0-10cm,10-20cm,20-30cm) monthly from May to October in 2006. At the same time, we measured the water content, pH value, organic matter content of soil, aboveground biomass of plant as well. We also collected the climate data (comprising temperature, precipitation and evaporation capacity). Based on these data, the relationship between environmental factors and soil mesofauna is analysized. In this paper, we took the four simultaneous typical plant communities as the four succession stage, because so long time required by succession is not practical for this study.The results showed that there are great differences in the number of individuals and groups of soil mesofauna among the four succession stage. 29 groups, 2 668 ind soil animals are found in Suaeda glauca communities, and they belong to 11 orders (include 3 suborders), 21 families. The common groups are consisted of Collembola, Coleoptera, and Diptera. 37 groups, 3 340 ind soil animals are found in Chloris virgata communities, and they belong to 13 orders (include 3 suborders), 30 families. The common groups are consisted of Collembola, Coleoptera, Diptera, and Hemiptera. 41 groups, 6 427 ind soil animals are found in Chloris virgata + Leymus chinensis communities, and they belong to 14 orders (include 4 suborders), 31 families. The common groups are consisted of Hymenoptera, Collembola, Pauropodiae, Coleoptera, Diptera, Hemiptera, and Homoptera. 48 groups, 7 186 ind soil animals are found in Leymus chinensis communities, and they belong to 16 orders (include 3 suborders), 39 families. The common groups are consisted of Gamasida, Collembola, Hymenoptera, Coleoptera, Homoptera, and Diptera. The dominant groups among vary plant succession communities are similar, mainly compsed with Oribatida, Actinedida, and Gamasida. But Collembola, Diptera and Homoptera probably are dominant groups in July, August, and September.The dynamics of soil mesofauna individuals in four plant communities have the same trend, as greater numbers of individuals in May, June and October than that in other months. But the trend of group number is vague and contrasts with that of individual. In vertical distribution of soil mesofauna, not only the individual numbers but also the group numbers in four plant communities aggregate in soil surface (0-10cm). The rate of decrease of group number is lower than that of individual number.The diversity indexes of soil mesofauna in Chloris virgata + Leymus chinensis communities and Leymus chinensis communities are great higher than that in Suaeda glauca communities and Chloris virgata communities. The similar index between Chloris virgata +Leymus chinensis communities and Leymus chinensis communities is the highest than other similar indexes.The correlation analysis showed that the factors of soil and climate are the main factors on soil mesofauna in Suaeda glauca communities, Chloris virgata + Leymus chinensis communities and Leymus chinensis communities. In Chloris virgata communities, vegetation affects strongly the soil mesofauna.