Study On The Characteristics Of Soil Nematode Community Under Different Utilization Modes In Typical Steppe Of Inner Mongolia

As the main part of temperate grassland in northern China,typical grassland in Inner Mongolia is of great significance in material circulation,energy flow and climate regulation,and also affects the production and life of local herdsmen.In this paper,the main components(soil nematodes,soil and vegetation)of typical steppe in Inner Mongolia,the interaction between them,and the response characteristics to different grazing forms were studied.Different utilization methods were set up,including control(CK),grazing in May and July(T2),grazing in June and August(T3),grazing in July and September(T4),mowing(TG),determination of quantitative indicators of plant communities,analysis of soil physical and chemical properties in different soil layers(0～10 cm,10～20 cm and 20～30 cm),and analysis of soil nematode composition by high-throughput sequencing.The effects of different utilization methods on plant communities,soil physical and chemical properties in different soil layers and soil nematode communities were discussed.The purpose of this paper is to study the interaction between soil,vegetation and soil nematodes through the analysis of plant community,soil physical and chemical properties and soil nematode community characteristics under different utilization modes,and to provide scientific basis for rational planning and grazing of typical grassland.The main results are as follows :(1)A total of 3 classes,6 orders,19 families and 29 genera of soil nematodes were detected in the surface layer(0～10 cm).Plant parasitic nematodes accounted for the largest proportion,and fungivores accounted for the smallest proportion.In addition to unclassified nematodes,21 genera of soil nematodes were detected under T2 treatment,20 genera of soil nematodes were detected under T3 treatment,17 genera of soil nematodes were detected under T4 treatment,and 19 genera of soil nematodes were detected under TG treatment.(2)In different soil layers,3 classes,6 orders,21 families and 35 genera of soil nematodes were detected under CK and T2 treatments.Under the genus level classification,compared with the control,the number of soil nematodes increased under T2 treatment.In the 10～20 cm soil layer,T2 treatment detected20 genera of soil nematodes,and in the 20～30 cm soil layer,T2 treatment detected 20 genera of soil nematodes.Among them,plant parasitic nematodes accounted for the largest proportion,and fungivores accounted for the smallest proportion.(3)In the 0～10 cm soil layer,compared with the control,the diversity and richness of soil nematodes under T2 treatment decreased significantly(P<0.05),and the diversity index and richness index of soil nematode communities under T3 treatment increased.In different soil layers,under CK and T2 treatments,the diversity index and richness index of soil nematodes were the highest in0～10 cm soil layer,and the diversity index and richness index of soil nematodes were the lowest in 10～20 cm soil layer under T2 treatment.(4)In 0～10 cm soil layer,the content of organic matter(OM)and available nitrogen(AN)in T2 treatment were significantly lower than those in other treatments(P<0.05),and the content of total potassium(TK)in different treatments was significantly lower than that in CK(P<0.05).In the 10～20 cm soil layer,the water content(SWC)and TK content of different treatments were significantly lower than CK(P<0.05).In the 20～30 cm soil layer,the TK content of different treatments was significantly lower than that of CK(P<0.05).(5)The effects of soil physical and chemical properties of different land use types on soil nematode communities were different.In the 0～10 cm soil layer,AP,TP,TK and AK of T2 treatment had a strong effect on soil nematode community.The effects of SWC,TK,AK,AP,AN and OM on soil nematode community were stronger in T3 treatment.The AK,TP,OM and SWC of T4 treatment had a strong effect on soil nematode community.The effects of OM,AP,SWC,TK and AK on soil nematode community were stronger in TG treatment.In 10～20 cm soil layer and 20～30 cm soil layer,T2 treatment of OM and AN had a strong effect on soil nematode community.(6)The dominant species of plant communities in the study area were Chenopodium aristatum,Leymus chinensis,Cleistogenes squarrosa and Stipa krylovii.Grazing affected the composition and importance value of plants.In the three grazing treatments,compared with the control,the diversity and richness of plant communities increased and unevenly distributed.The plant community diversity under T3 treatment was the highest,and the plant species under T4 treatment were the most abundant,but the distribution was uneven.(7)Plant communities with different utilization patterns have different effects on soil nematode communities.In the 0～10 cm soil layer,six main plants(Leymus chinensis,Cleistogenes squarrosa,Stipa krylovii,Chenopodium aristatum,Corispermum,Thalictrum squarrosum)with large importance values under T3 treatment had significant effects on soil nematodes.Stipa krylovii and Cleistogenes squarrosa had significant effects on soil nematode communities under different grazing conditions.In summary,vegetation,soil and soil nematodes are the main components of typical grasslands in Inner Mongolia,and the interaction among them affects the development of grasslands.Grazing and mowing,as the main utilization methods of grassland,have a direct impact on plant communities and soil physical and chemical properties,thus affecting soil nematode communities.