Relationship Between Soil Nematode Community Characteristics And Soil Fertility In Desert Steppe With Different Grazing Intensities

Grazing is an important regulating factor of desert grassland in Inner Mongolia,which plays an important role in underground ecological process.Soil nematodes,as environmental indicators widely distributed in different types of soils,have important ecological significance in maintaining soil stability and promoting energy flow and material circulation.In this study,the long-term positioning experiment of grazing disturbance was carried out in the desert grassland of Inner Mongolia.The fence was divided into three groups.Four different stocking rate levels were set in each group,namely blank control area(CK),light grazing area(LG),medium grazing area(MG)and heavy grazing area(HG).High throughput sequencing technology was used to explore the response mechanism of soil nematode community structure and soil nematode community diversity to grazing disturbance.So as to give better play to the indicative role of soil nematodes in desert grassland ecosystem and provide theoretical reference for rational grazing in desert grassland.The main conclusions are as follows:(1)There is no significant difference in physical and chemical properties between enclosed control plot and lightly grazed plot.Compared with CK,HG significantly reduced the contents of Soil Organic Carbon(SOC),Total Carbon(TC),Total Nitrogen(TN),Total Phosphorus(TP),available potassium and Available Phosphorus(AK,AP).With the exception of,redundant analysis shows that soil factors such as soil p H value,available phosphorus and available potassium have a significant influence on soil nematode abundance,and then affect the community structure of soil nematodes.(2)Different grazing intensities significantly affect the composition and diversity of soil nematode communities in different seasons.In the first quarter,omnivorous nematodes were the dominant trophic group,with the increase of grazing intensity,the abundance first decreased and then increased,and the abundance was the smallest under moderate grazing.In the second quarter,plant-eating nematodes were the dominant trophic group,The increase in grazing intensity led to a decrease in the soil nematode abundance.Under light grazing,the abundance increased.In the third quarter,as in the fourth quarter,the abundance of dominant group phytophagous nematodes is the largest under moderate grazing,while that of omnivorous predatory nematodes is the smallest under moderate grazing.Light or moderate grazing increased the diversity of soil nematodes in the first and third quarters.Enclosure control enhanced the diversity of soil nematodes in the second and fourth quarters.(3)The Maturity Index(MI)of soil nematodes in fenced areas in the first quarter is significantly higher than other grazing treatments,the Basic Index(BI)is significantly higher than other treatments in the first quarter under moderate grazing,the Sructure Index(SI)will decrease with the increase of grazing intensity,and the Enrichment Index(EI)will increase with the increase of grazing intensity.Wasilewska Index(WI)and Plant Parasitic nematode maturity Index(PPI)had no significant difference in four seasons under grazing treatment.Nematode Channel Ratio(NCR)showed that,with the exception of heavy grazing in the first quarter and moderate grazing in the fourth quarter,all other grazing and quarterly treatments were fungal channels,which indicated that the fungal decomposition pathway was dominant in the regreening period and growth period of grazing land,while the bacterial decomposition.(4)Moderate grazing can maintain soil nutrients,increase soil biomass and structure.Moderate grazing is beneficial to nutrient circulation and energy circulation in the soil.In contrast,moderate and heavy grazing weakened soil fertility and reduced the diversity of soil nematodes.In this study,it is considered that the most suitable grazing intensity of desert grassland in Inner Mongolia is light grazing.