Response Of Soil Nematodes To Nitrogen Addition In The Xing'an Larch Forest In The Greater Khingan Mountains

The extensive accumulation of nitrogen(N)caused by human activities such as nitrogen deposition and fertilization has greatly changed the structure and function of ecosystem.Although the low level of nitrogen added usually promote ecosystem function,but high levels of nitrogen to add will induce forest of water,soil acidification and inhibition of soil organisms,and structure and function of forest ecosystems have a significant impact,so the nitrogen deposition has become a forest ecosystem sustainable development are the main research content.Nematodes are the most abundant and species of soil animals,which occupy an important nutritional position in soil food web.Therefore,nematodes are considered to be an important indicator of soil ecosystem function under nitrogen enrichment conditions.In this study,a simulated nitrogen deposition control experiment was conducted to study the effects of nitrogen addition on soil nematode community structure and soil physicochemical properties in a boreal forest of Larix Xing'an in the Greater Hinggan Mountains.The results showed that:Soil total nitrogen,soil ammonium nitrogen,soil p H and the number of plant groups all showed significant changes with different nitrogen addition.The addition of nitrogen significantly reduced the soil p H value.There were 54 genera in soil nematodes of larch in the Daxingan Mountains.The dominant groups were Plectus,Alaimus and Tylencholaimus,and the phenomenon of superaggregation was obvious.The results showed that:(1)Compared with the control group,the diversity index(H')of soil nematode was decreased and the dominance index(?)of soil nematode was increased under low,medium and high nitrogen treatments,indicating that the stability of soil nematode community tended to increase with the increase of nitrogen content.(2)Nitrogen addition reduced the abundance of soil nematodes,significantly affected the relative abundance of Fungivores and Bacterivores,and significantly affected Bacterivores.Predators and nematodes referred to as bacterial eaters and plant parasitic nematodes were referred to as prey /Omnivores decreased with the addition of nitrogen.Nitrogen addition had significant effects on the diversity,community structure,and richness of soil nematodes,but had no significant effects on the community structure of Fungivores,Bacterivores,and omnivores-predator nematodes.(3)Soil nematodes with different feeding habits had different responses under different nitrogen addition treatments.The number of bacteriophagous nematodes was the highest and decreased with the increase of nitrogen content.There was no significant change in the number of parasitic nematodes.The number of fungivorous nematodes increased significantly under medium nitrogen treatment.The number of omnivorous/predatory nematodes decreased with the addition of nitrogen.Under nitrogen added processing food groups of fungi taxa,plant parasitic nematodes food bacteria groups nematodes and omnivorous/line and feed on the number of taxa nematodes are under different degree of relative reduction,which illustrates the different levels of nitrogen added element added amount of different types of soil nematodes community shows relative to different degree of inhibition.These results suggested that soil nematode communities were affected by nitrogen supplementation,and changes in the structure and composition of soil nematode communities made the underground food web of terrestrial ecosystems have a good indicative potential in response to nitrogen deposition,an important driver of global change.These results are helpful for us to study the response mechanism of soil nematodes to nitrogen addition in boreal forest ecosystems.