Spatial And Temporal Distribution Of Soil Fauna And Its Influencing Factors In Typical Small Catchment In The North Loess Plateau

Since the large-scale implementation of the measures of returning farmland to forests and grasslands on the Loess Plateau,it has significantly improved vegetation coverage,significantly reduced the amount of yellow sediment,and gradually improved the ecological environment.At the same time,the ever-increasing vegetation coverage has also provided suitable habitats and sufficient food sources for soil fauna,which has significantly improved the biomass and diversity of soil fauna.Soil fauna play a very important role in participating in ecosystem material circulation and energy flow,improving soil structure,promoting soil material migration and transformation,evaluating soil environmental management and restoration,and protecting biodiversity.At present,the research on the effects of vegetation restoration on soil fauna on the Loess Plateau has not received enough attention.This article conducted a comprehensive and systematic study on the composition,spatiotemporal distribution,and influencing factors of soil animal communities in Liudaogou Watershed,Shenmu City,northern Loess Plateau,in order to reveal the impact of vegetation restoration on soil fauna communities,and explore the relationship between environmental factors and soil fauna.It provides a reference for the scientific evaluation of the ecological effects and ecological service values of the measures of returning farmland to forests and grasslands on the Loess Plateau,and provides important basic data and theoretical support for a more indepth study of soil fauna as indicators of ecological restoration quality.This study focused on soil fauna from different habitats.In May,August and November 2019,Populus simonii,Pinus tabulaeformis,Caragana korshinskii,farmland,Stipa bungeana,Medicago Sativa,Burued-Stipa bungeana and Burued-Medicago Sativa habitats were selected,using a combination of field sampling surveys and indoor analysis tests,compared the characteristics of soil fauna communities under different site conditions,analyzed the spatial and temporal distribution of soil fauna,and quantified the relationship between soil fauna community structural characteristics and environmental factors.The main results and conclusions were as follows:1.A total of 32,494 soil fauna were collected in this study,of which the number of identifiable species reached 3,1997,and the remaining 497 were unable to accurately determine species attributes.This study mainly focused on soil fauna that can be accurately identified,and the results showed that the 3,1997 soil fauna belonged to 1 phylum,7 classes,and 32 groups.The dominant groups of Acarina and Collembola account for 69.88% and 11.96% of the total,respectively.There were 5 common groups,accounting for 14.34% of the total catch.There were 25 rare groups,accounting for 3.82% of the total catch.2.The largest number of soil fauna groups was the Caragana korshinskii habitat,the smallest was the farmland habitat;the largest total density of soil fauna was the Medicago Sativa habitat,and the smallest was the Burued-Stipa bungeana habitat.Dominant groups in different habitats varied between Acarina,Collembola,Isoptera,and Formicidae,and the Acarina was the dominant group in all habitats.Although the number of dominant groups was small,the proportion of their biomass in total capture was very high(72.3%-91.2%).The differences in the composition of soil fauna in eight habitats indicate that different habitats have a certain effect on the composition of soil fauna communities.Diversity analysis of soil fauna communities in different habitats showed that the Shannon-Wiener diversity index(H)and Pielou uniformity index(J)were positively correlated,and negatively correlated with the Simpson dominance index(C).3.The dynamic changes of the number of soil fauna,the number of groups,and the total density in different seasons was always: August(summer)> November(fall)> May(spring).Although the dominant groups in different seasons were Acarina and Collembola,the dynamic trend of the number and density of dominant groups was always August(summer)> November(fall)> May(spring).Isotomidae and Arthropleona were endemic species in August(summer),and Cyclorrhapha and Bombyliidae were endemic species in November(autumn).The dynamic changes in the number of soil fauna,the number of groups,and the total density in different habitats also showed the phenomenon of August(summer)> November(fall)> May(spring),indicating that the characteristics of soil fauna have obvious differences in different seasons.The seasonal variation of soil fauna community indices in different habitats indicated that the diversity index(H)and uniformity index(J)of Populus simonii,Caragana korshinskii,Medicago Sativa and Burued-Stipa bungeana habitats were the largest in spring.The diversity index(H)and evenness index(J)of Pinus tabulaeformis,farmland,and BuruedMedicago Sativa habitats were the largest in summer.However,the abundance index(D)of all habitats was basically the largest in summer.4.The comparative analysis of environmental factors in different habitats showed that the soil organic carbon,total nitrogen,nitrate nitrogen,litter total nitrogen,and litter total phosphorus content of Medicago Sativa habitat were the largest in all habitats,while the surface soil water content,soil p H,soil organic carbon,total nitrogen,total phosphorus,and ammoniacal nitrogen content of Populus simonii habitat were among the lowest in all habitats.Analysis of the relationship between environmental factors and soil fauna showed that Acarina,Collembola,and Homoptera tend to areas with higher soil water content,soil available potassium and soil total nitrogen;Diptera larvae and Coleoptera adult tend to areas with high soil total phosphorus and soil organic carbon content;Araneae and Coleoptera larvae tend to area with high litter organic carbon content.Comprehensive analysis showed that the main environmental factors affecting soil fauna changes in the watershed were litter organic carbon,soil water content,soil total nitrogen,soil total phosphorus,soil olsen phosphorus,and soil organic carbon.As mentioned above,this study showed that the groups and numbers of soil fauna in this watershed was still at a low level compared with other regions at the same latitude,and ecological restoration projects still need to be scientifically carried out.There were some differences in the characteristics of soil fauna communities under different artificial restoration vegetations.The Caragana korshinskii and Medicago Sativa habitats were best suited for the survival of soil fauna.In addition,the characteristics of soil fauna also had certain differences in time.Summer was the most favorable season for the survival of soil fauna.Soil fauna were more sensitive to environmental changes.The changes of soil fauna communities in this watershed were mainly affected by litter organic carbon,soil water content,total soil nitrogen,total soil phosphorus and soil organic carbon...