Study On The Trophic Structure Of Soil Food Web In Karst Forest Of Maolan

Soil animals in soil ecosystems are huge and diverse,Through the relationship between predation and predation,they have formed a complex relationship of soil animal food web structure,which plays an important role in the energy flow and material circulation in the soil ecosystem.Studying the energy flow relationship among soil animals can not only reflect the energy flow relationship among soil animals,but also can understand the intrinsic connection among soil animals.Conducting research on the distribution composition of soil fauna and the trophic level relationship of soil fauna in different vegetation succession stages is important for understanding the role played by soil fauna in the food web.Carrying out the composition of soil distribution and its trophic level relationship in different vegetation succession stages can help explore the value and role of soil fauna in soil food webs,which is of great practical significance for understanding the study of forest soil food web structure and improving forest ecosystem productivity and biodiversity conservation.The karst forest of Maolan is a relatively concentrated,native and stable karst forest system remaining in the same latitude of the subtropics in the world,and it is also the largest area of native forest distribution in the karst region,which is representative and typical.However,studies on the soil food web of this unique karst ecosystem are still relatively rare.Therefore,in this paper,Mao Lan Nature Reserve was selected as the study area,and the soils of four vegetation types(grassland,scrub,shrubland,and native forest)in Mao Lan karst primary forest were selected for sampling and collecting soil fauna,and the food web structure was constructed by studying the trophic level relationship of soil fauna through stable isotope technique.It provides a theoretical basis for further understanding of soil fauna distribution composition and soil food web research under different vegetation succession stages in karst forests.The main conclusions are as follows.1.In this study,a total of 4125 soil animals and 30 species groups were collected from soil and litter in four different vegetation succession stages in Maolan Karst,belonging to 2 phyla,7 classes and 20 orders.In different vegetation succession stages,the dominant populations of soil animals are different.In the original forest stage,the collected species have 30 species groups,belonging to 2 phyla,7 classes and 20 orders;the species collected in the shrub forest stage have 27 species groups,belonging to 2 Phyla 7classes and 19 orders;species collected in the bush stage have 24 species groups,belonging to 2 phyla,6 classes and 13 orders;species collected in the grassland stage have 19 species groups,belonging to 2 phyla,6 classes and 16 orders.2.The distribution of soil eukaryotic microorganisms by sequencing18 S rRNA at different successional stages was as follows: at different taxonomic levels,the dominant populations of soil eukaryotic communities at different successional stages were similar in composition.At the Supergroup level,the dominant populations of the community were mainly composed of Opisthokonta,Alveolata and Rhizaria,and the sum of their relative abundance reached 74% of the community structure;at the Division level,the dominant populations of the community were mainly composed of Fungi,Cercozoa and Streptophyta,and the sum of their relative abundance reached 63% of the community structure.(2)Soil eukaryotic microbial diversity differed at different successional stages,and the Shannon index and Simpson index were as follows: native forest >shrubland > shrubland > grassland at different successional stages.3.The trophic levels of soil animals in the food web of the karst forest in Maolan,Guizhou were calculated by carbon and nitrogen stable isotope analysis according to certain trophic level formulae,and a relatively simple soil food web structure was initially constructed.It was found that the soil fauna collected in this experiment consisted of three main trophic levels,with primary producers such as plant litter in the first trophic level.The second trophic level included taxa such as dung mosquitoes,Coleoptera,Chaetognathidae,nematodes,dinoflagellate larvae,Orthoptera,subfamilies of marching ants and leaf-cutting ants;and the third trophic level included taxa such as centipedes and ground spiders.This indicates that the soil fauna collected in this study spanned three trophic level positions in the soil food web.