Effects Of Grazing On Soil Nematode Communities And Seasonal Changes In Desert Steppe

Soil nematodes are an important part of the food web of soil ecosystems.They participate in and promote material circulation and energy flow,and play an important role in maintaining the stability of ecosystem structure and function.As the main resource utilization and management method in temperate steppe,grazing can indirectly affects the structure and ecological function of soil nematode communities through changing plant communities and soil.By supporting of the long-term grazing test platform of Stipa Breviflora Desert steppe in Inner Mongolia,this study set up control(0 sheep unit/hm~2/half year),mild(0.91 sheep unit/hm~2/half year),moderate(1.82 sheep unit/hm~2/half year)and severe(2.71 sheep units/hm~2/half year),four grazing intensities,layouting by a completely randomized block design.A survey of soil nematodes communities were conducted by separating animals using Shallow Dish Method and identifing with morphological features in spring(April),summer(July),and autumn(October)respectively Studying the effects of grazing intensity soil on nematode community and its seasonal distribution may provide a theoretical basis for maintaining the health of desert steppe ecosystems and sustainable development of animal husbandry.The main conclusions are as follows:(1)A total of 19,355 soil nematodes were captured in the grazing plot,belonging to36 genera.The dominant taxa are Cervidellus and Acroloboides with 19 common taxa.Grazing did not change the composition of soil nematodes communities.With the increase of grazing intensity,soil nematode abundance decreased.The effect of the same grazing intensity on soil nematode individual numbers was different from spring to autumn.The abundance of soil nematodes with different nutritional groups decreased with the increase of grazing intensity,but had significant effects on the abundance of fungal feeding nematodes,bacterial-eating nematodes and herbivorous nematodes.Grazing had significant effects on fungal-eating nematodes and herbivorous nematodes in different seasons.Soil nematode communities were similar between lightly grazing and control habitats,and soil nematode communities were similar between moderately and heavily grazing habitats.(2)Grazing had some effects on the Shannon-Wiener index,Richness index and Simpson index of soil nematode communities.Moderate grazing significantly increased the Shannon-Wiener index and Richness index,and significantly decreased Simpson index.This study showed that moderate grazing disturbance was benefit to the improvement of soil nematode community diversity.(3)The decomposition of soil organic matter in the grazing plot was mainly carried out by fungi.Although light and moderate grazing increased the proportion of fungal nematodes in a certain extent,grazing did not change the organic matter mineralization pathway of soil.Moderate,severe grazing made the soil environment more stable and the soil of total grazing plots was still in high quality.Grazing did not affect the nutrient accumulation of soil nematode communities,and the soil food web was structured.(4)Grazing did not alter the changing pattern of characteristics,biodiversity and ecological functions of soil nematode communities from spring,summer and autumn.We deduce that the differences of soil nematode communities among different seasons were mainly controlled by each seasonal hydrothermal conditions,grazing did not affect the rhythmic law of soil nematode communities.