Effects Of Nitrogen Deposition And Litter Input On Soil Nematode Community In Songnen Meadow Steppe

Soil nematodes occupy several trophic levels in soil food web,and play an important role in soil ecosystem,especially for organic matter decomposition,nutrient mineralization and cycles.Nitrogen deposition is much more serious,and affects nematode community and its ecological function.Grassland litter is the main way to link aboveground biomass and decomposer subsystem,and to input carbon,nitrogen,phosphorus and other nutrients into the soil.Nitrogen addition and litter manipulation have strong effects on soil nematodes via their impacts on the plant community,soil nutrients and soil environment in grassland systems.Currently,there are few studies about the combined effects of nitrogen addition and litter on soil nematode.In particular,the effects of litter manipulation on soil nematode communities with nitrogen deposition are lack of relevant research.In this study,we mainly focused on the effects of different level litter on soil nematode community,soil properties and plant community under different nitrogen addition levels,on Songnen meadow steppe.The main results were as follows:(1)It was found that nematode individual density was 261/100 g dry soil on average on Songnen meadow steppe,belonged to 31 families and 54 genera.The dominant group included Tylencholaimus and Acrobeloides,the common group included Basiria,Tylenchorhynchus and Pratylenchus etc 18 genera,and the rare group included Coslenchus,Boleodors,Rotylenchus etc 34 genera.(2)Nitrogen addition and litter manipulation had no significant effects on nematode richness.Nitrogen addition and litter manipulation had no significant effect on soil pH and soil total nitrogen content.But nematode richness decreased with increasing soil pH and total N concentration.Soil pH had negative effect on nematode richness by decreasing the abundance of Filenchus and Discolaimus.Soil N concentration increased nematode richness mainly by increasing Rotylenchus and Prismatolaimus.(3)The effects of nitrogen on nematode depend on litter levels.Nitrogen addition significantly reduced total abundance,diversity and maturity index of nematode in double litter treatment.In the remove and natural litter treatments,nitrogen addition had no significant effects on nematodes.Nitrogen addition directly reduced nematode abundance,as well as increased abundance and diversity of nematode through improving soil nitrate concentration and plant shoot biomass.(4)The effects of litter on nematodes could be affected by nitrogen.Without nitrogen addition,the total abundance of nematodes increased with increasing litter levels,and there was no change in diversity and maturity index of nematode.With nitrogen addition,nematode abundance was not affected by litter manipulation,and diversity and maturity index of nematode decreased with increasing litter levels.Litter treatments enhanced the abundance of nematode by increasing soil moisture,could directly decrease nematode diversity,and also could reduce diversity by inhibiting plant growth.(5)There are significant interactive effects between nitrogen addition and litter on soil nematode communities.With increasing litter levels,the adverse effect of nitrogen addition on nematodes increased.As well as,with nitrogen addition,litter addition had the disadvantage to maintain the stability of nematode community.The results showed that decreasing litter can reduce the adverse effects of nitrogen deposition on nematode.Under the background of nitrogen deposition,reasonable utilization of grazing and mowing can maintain the stability of grassland ecosystem structure and function though decreasing the litter accumulation.In conclusion,present study clarified the mechanism of the effects of nitrogen addition and litter manipulation on soil nematodes.It revealed the pathways of nitrogen addition and litter manipulation to regulate nematode communities by changing soil environment and plant communities.This study can give deep understanding of the maintain mechanism of structure and function of grassland ecosystem,and its response to global change and human disturbance,as well as enriched the theory of grassland ecology and biodiversity.