Diversity Analysis Of Soil Fauna In Restoration Area Of Loess Plateau

China has carried out large-scale afforestation in the northwest since the 90 s of last century.Over the past 30 years,water loss and soil erosion has improved a lot,and there are types vegetation forms of different successions in the Loess Plateau Region.As an important component of the ecosystem,soil fauna take part in the material circulation and energy flow in the soil ecosystem.Also,soil fauna can reflect the superiority of the habitat sensitively and indicate changes of the vegetation in some way.So far it has not been figured out that how soil fauna community changes in loess hill and gully region,as well as its evolution mechanism.This paper studied soil fauna in restoration area of Wuqi County,and the methods contained field investigation and laboratory test.During the July to September 2017,we investigated forest lands of different conditions like site condition,species,years of returning farmland,recovery measures and concentrated on researching the composition of soil fauna,quantitative characteristics,spatial and temporal pattern and the evolution of soil factors.The purpose of this paper is to analyze the distribution of soil fauna on different site conditions,to explore the response of soil fauna to secondary succession of plantation,to evaluate the ecological effects of plantation scientifically,to provide basic data for construction of vegetation that can conserve soil and water efficiently and for a new round of returning the grain plots to forestry and consolidation of reforestation.Main results of this paper are as follows:(1)This investigation captured soil fauna of different sizes 1905 in total,subordinating to 4 phyla,10 classes,25 orders,66 groups.The dominant groups were Coleoptera,Hymenoptera and Araneae.The common groups were 11 groups that contained Homoptera,Hemiptera,Geophilomorpha,Dermaptera,etc.The rare groups were 14 groups that contained Lithobiomorpha,Zygentoma,Microcoryphia,chelonethida,etc.The major component of Loess Plateau soil fauna is macro-meso soil fauna including Coleoptera,Hymenoptera,Hemiptera,Araneae,Stylommatophora and so on.Micro soil fauna like Acarios and Chelonethida is much more less.In the investigation region,the species and quantity of soil fauna showed that the southeastern part was larger than the northwest.The phytophagous and predatory groups were more,and the humorous and omnivorous groups were less.(2)In different site conditions,slope direction,slope position and vegetation types had a significant impact on soil fauna's species number,individual number,biomass and diversity index.The number of soil fauna in shade slope is much more than that in sunny slope(P<0.05).The distribution of soil fauna characteristics on different slope showed a lower slope margin higher than the upper slope margin(P<0.05).Under different vegetation types,the distribution of mixed forest in the individual density and biomass was significantly higher than that of pure forest(P<0.05),and the grassland is somewhere in between.(3)Soil fauna accumulated in the surface obviously in plantation of different stage of succession.The secondary succession influenced the density and biomass of soil fauna significantly,and it showed a tendency that increased at first and then decreased.The peak value of individual density and biomass was in five to ten years after afforestation,and gradually decreased with the secondary succession of plantation.The succession of vegetation changed the function groups of soil fauna,which made the species of herbivores less,and the proportion of predatory and omnivorous animals increased.(4)The soil water content in different rainfall plots is positively correlated with atmospheric rainfall.In the 310-350 mm area of rainfall,the density of individual and biomass appeared that the bottom layer larger than the surface layer,and soil fauna assumed inverse distribution.The individual density and biomass of the surface and bottom soil fauna increased with the increase of rainfall.In different rainfall plots,the individual density and biomass of soil fauna was woodland > grassland > farmland,and the individual density,biomass and rainfall were positively correlated.