| Soil nematodes exist widely in various ecosystems,and their community structure and metabolic footprint can comprehensively and effectively reflect the structure and function of soil food web,soil health status and other information,and are regarded as biological monitors to indicate the degree of environmental disturbance.At present,there are no consistent conclusions on the effects of common utilization methods（mowing and free grazing）and enclosure measures without any utilization on soil nematode community in steppe.Therefore,in this study,soil nematode samples were collected from Baikal Stipa steppe under different utilization methods（mowing,free grazing and control enclosure）in May,August and October of 2021.The nematode samples were extracted and isolated by improved shallow disk method,and morphological identification and number statistics were conducted by stereomicroscope and light microscope.To explore the characteristics of soil nematode community and metabolic footprint under different grassland utilization patterns and their relationship with environmental factors.The results are as follows:（1）A total of 20536 nematodes were captured in the study area,belonging to 64genera,with an average individual density of 1140·100g dry soil-1.NMDS analysis showed that soil nematode species composition and dominant genera differed significantly among different utilization modes.Total nematode abundance,Ba,Pp and Op,c-p 3 and c-p 5nematode abundance were significantly decreased in mowing habitat,and total nematode abundance and functional group nematode abundance were significantly decreased in free-grazing habitat（P<0.05）.（2）The diversity and stability of nematode community were significantly decreased in free-grazing habitat（P<0.05）,but the anti-jamming ability of food web was significantly increased（P<0.05）.The connectivity and food chain of soil food web in mowing habitat were significantly stronger than that in enclosure（P<0.05）.The enclosure habitat significantly increased the external input soil nutrients,and the stability of soil health status was significantly enhanced（P<0.05）.NCR value<0.75 and WI value>1 indicated that bacterial pathway was the main decomposition pathway of organic matter in stipa baikal steppe,and microbivorous nematodes were the main carrier of soil mineralization pathway.（3）TNf,Baf and Opf were significantly decreased in mowing habitat（P<0.05）,TNf and metabolic footprint of nutrient groups were significantly decreased in free-grazing（4）habitat（P<0.05）,and overall activity and carbon flow of nematode community were significantly increased in enclosure habitat（P<0.05）.The flora analysis showed that the soil food webs were all structured under different utilization modes,and only the soil food webs in the enclosed habitats became mature in August.We also found that nearly half of the carbon and energy input to the food web is from the omnivorous nematode channels.（5）Soil depth and seasonal change had significant effects on nematode community（P<0.05）.However,the surface aggregation characteristics of nematode communities were not changed,the response of nematode community to grassland use in 10-20cm soil layer was weaker than that in 0-10cm soil layer.There was a positive effect on the development of nematode community in the vigorous vegetation season（August）compared with the green season（May）and yellow season（October）.（6）RDA analysis showed that environmental factors affecting the composition of nematode community were different under different utilization modes,among them,TN and AGB were the main environmental factors affecting soil nematode composition in enclosure habitat,SOC in mowing habitat,AK,TN and AGB in free grazing habitat.Correlation analysis showed that soil TN,AK,SWC and BGB were significantly correlated with nematode community structure under different utilization modes. |
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