| The soil food web plays a vital role in the ecosystem,participating in a series of soil ecological processes such as the cycle and storage of soil carbon and nitrogen,the formation and decomposition of organic matter,the adjustment and improvement of soil structure,and soil micro-food web are closely related to above-ground plant communities and underground soil habitats,and are sensitive to changes in the external environment.They used as important factors to characterize soil environmental changes and indicate soil health.However,domestic scholars have carried out the overall research on the soil food web,but there are relatively few studies on the biological change characteristics of nematode-microarthropods in karst ecological restoration and the evolution characteristics of the combined soil micro-food web.The soil micro-food web composed of "microarthropod-nematodes" is an important part of the ecosystem,especially the underground ecosystem.They are large in number and occupy a large number of trophic levels,which can well demonstrate the feedback effect of upward and downward effects.However,most of the related researches on the restoration and reconstruction of karst ecosystems are biased to the status quo research,while the research on the karst restoration process and the research related to the soil micro-food web are relatively few.Therefore,in this study,we used space instead of time series to sample the different restoration stages of the degraded karst area in Maolan,Guizhou.Grassland,Bushes,Shrubbery and Forest were selected.Four typical plots with different succession processes,outdoor investigation and indoor analysis of four different soils,ground cover vegetation,and underground soil animals were conducted,and the collected soil animals were identified and classified according to their feeding preferences.Ten types of nutritional function groups: Fungivorous Collembolans,Predaceous Collembolans,Nematophagous mites,Predaceous mites,Non-Cryplosligmatic mite,Cryplosligmatic mites,Fungivorous nematodes,Bacterivorous nematodes,Plant-parasitic nematodes,Predacous nematodes.And on this basis to study the relationship between soil physical and chemical factors,ground cover plants and soil micro-food web structure and carbon and nitrogen mineralization in different restoration stages,and to understand the degraded karst ecology.The main results are as follows:(1)Sampling was conducted in four different restoration stages to study the change characteristics of soil physical and chemical factors at different stages.The original forest plot has the highest organic matter content,and the grassland plot has the lowest organic matter content.The overall performance is original forest>shrubland>shrub forest>grassland.The soil moisture content has a very significant correlation with total nitrogen and total carbon.There is a very significant correlation between organic matter and total nitrogen,total carbon and easily oxidizable carbon.There is a very significant correlation between total carbon and total nitrogen and easily oxidizable carbon.(2)The structure and diversity of nutrient function groups at different succession stages and their relationship with soil physical and chemical properties.fungivorous Collembolans,fungivorous mites,and plant-parasitic nematodes are belong to the dominant communities in the four types of plots;fungivorous nematodes,predatory/omnivorous nematodes,nematode mites,omnivorous non-recessive mites,and predatory Collembolans are belong to the common communities in the four types of plots;bacterivorous nematodes are belong to the rare communities in the four types of plots.Shannon-Wiener index,Margalef index,Density-Group index,Pielou index gradually increase with the succession of restoration,while the Simpson index gradually decreases.The relationship between the structure and diversity characteristics of the nutritional functional groups at the stage is more significant.(3)The soil micro-food web structure under different restoration stages.The maximum number of functional groups in the original forest is 10,and the minimum number of functional groups in the grassland is 7,and the bacterial nematode is a unique functional group in the original forest plot.The range of connectivity is between 0.48-0.60,the maximum length of the food chain is between4-5,and the average length is between 0.83-1.17.Among them,the connectivity of the original forest and the average length of the food chain are the largest;overall,except for predatory bombs Except for Caudata,fungus-eating nematodes,and predatory nematodes,the biomass of other functional groups gradually increases with succession.From the inside of the soil micro-food web,the biomass of the first trophic level is higher than that of the second trophic level,and As the succession progresses,the biomass of different trophic levels will gradually increase.(4)Soil micro-food web ingestion rate and carbon and nitrogen mineralization in different stages of restoration.In the different stages of restoration succession as a whole,in the process of energy flow from low trophic level to high trophic level,the functional group.The food intake rate of karst is gradually reduced;the carbon and nitrogen mineralization rate of each trophic level in different successional stages gradually increases with significant differences,but as the trophic level increases,the carbon and nitrogen mineralization rate decreases;with the degradation of karst.The carbon and nitrogen mineralization rate of each nutrient function group is gradually increasing during the restoration of the ecosystem,but the carbon mineralization rate of the functional groups gradually decreases during the flow from low-level trophic to high-level trophic.(5)Through comparative analysis,the adjustment of C in the energy flow of the soil micro-food web can be used as an entry point by Cryplosligmatic mites,while the adjustment of N in the energy flow of the soil micro-food web can be used as an entry point by Predaceous mites. |
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