Effects Of Nitrogen Addition On Soil Nematode And Microbial Community Structure In A Stipa Baicalensis Grassland In Inner Mongolia

Nitrogen is one of the most important limiting nutrients on Earth's life activities.The increase in atmospheric nitrogen deposition is one of the important phenomena of global environmental change.The series of ecological problems brought about by it have become increasingly serious,affecting the structure and function of grassland ecosystems.It has become one of the important research contents of the natural grassland ecosystem to cope with climate change and sustainable development.The community characteristics of soil nematodes in a Stipa baicalensis grassland in Inner Mongolia under different nitrogen?NH₄NO₃?treatments(N0,N15,N30,N50,N100,N150,N200 and N300 kg N·hm^-2·a^-10)were studied by field investigation and sample analysis using the morphological classification method.In total,52 genera were identified in all the samples.The dominant species were Helicotylenchus,Acrobeles,and Aphelenchus.Soil nematodes showed an obvious surface convergence phenomenon,and their relative density was not significant.Different nitrogen addition levels had no significant effect on the density of soil nematode,but had significant effects on the relative densities of soil nematodes of Bacterivores nematodes,Fungivores nematodes,and plant parasites.The effect on plant parasitic group nematodes is particularly significant.From the functional group point of view,with the increase in the level of nitrogen addition,nematodes of Bacterivores nematodes and predators/Omnivores necrosis were negatively correlated with nitrogen addition levels.Nitrogen addition mainly affected the species richness of the soil nematode and the stability of the community structure,and had no significant effect on the nematode and plant parasitic groups of the soil and the community structure of the Predators/Omnivores nematode.From the ecological point of view,in the range of<N50 nitrogen addition,nitrogen addition will promote the increase of soil nematode richness?SR?,diversity?H'?,evenness?J'?index;The pathway index was less than 0.75 in all treatments tested,indicating that the organic matter decomposition pathway in the soil is dominated by fungi;The Vasteraska index shows that a small amount of nitrogen added can improve the environmental conditions of the soil and reduce the impact of plant parasites on plant infection and plant community structure.In terms of microbial community,different nitrogen addition levels significantly affected the structure and number of soil microbial fungal and bacterial communities,but the effect on soil microbial content was not significant.In terms of the coupling of soil nematodes and soil physicochemical factors,When the amount of nitrogen applied was>N100,the soil pH value decreased significantly,the nitrate nitrogen and ammonium nitrogen contents increased significantly,the soil life history k countermeasures were significantly reduced,and r countermeasures were significantly increased,significantly altering the soil nematode community structure.In terms of the coupling of soil nematodes and soil microorganisms,the correlation analysis between soil microorganisms and soil nematodes revealed a significant positive correlation between soil parasitic nematodes and soil bacterial communities,fungal communities,and fungi/bacteria.It indicated that the change of soil microbial community significantly affected plant parasitic group nematodes.The effect of nitrogen addition on soil microbes is greater than that of soil nematodes.There was a significant correlation among the richness,evenness,and structural index of soil fungal communities and soil nematode communities.