The Response Of Soil Nematode Community To Temperature And Precipitation On The Eastern Tibetan Plateau

Soil nematodes are the most abundant and diverse soil animals.Soil nematodes occupy in major trophic levels and are important components of soil food webs.Therefore,it is important to study the spatial distribution pattern of soil nematodes to further realize the patterns and mechanisms of changes in soil food webs.Recently,although our understanding on the spatial distribution pattern of soil nematodes has greatly advanced,relevant studies remains rare on the Tibetan Plateau.Therefore,we investigated soil nematode communities in 590 soil samples from 118 sites(latitude29.14-38.85°N,longitude 88.15-101.51°E,altitude 2793-5217 meters)in the alpine grassland of the eastern Tibetan Plateau.Soil properties(soil moisture,p H,available phosphorus,ammonium,nitrate,carbon-nitrogen ratio,carbon-phosphorus ratio,and nitrogen-phosphorus ratio)and plant community characteristics(plant richness,and plant coverage)were measured,while climatic(annual mean temperature and annual mean precipitation)were extracted from world Clim 2.1 dataset and geographic factors(longitude,latitude,and altitude)were also recorded.The responses of soil nematode community(abundance,richness,community composition and within-site community similarity)to climatic and geographic factors were analyzed by(generalized)linear mixed effect models(GLMM and LMM)and structure equation modellings(SEM).And we also compared the response patterns of each trophic group and community level of soil nematodes,and potential mechanisms of the response pattern were speculated.We found:1.On the eastern Tibetan Plateau,total nematode abundance were regulated by both annual mean precipitation(MAP)and annual mean temperature(MAT)(i.e.,the significant interaction between the MAP and the MAT): when the MAP was lower than400 mm,the nematode abundance increased significantly with the MAT,when the MAP was higher than 400 mm,the nematode abundance decreased significantly with the MAT.At trophic levels,the response pattern of each trophic group was consistent with the community level.According to SEMs,we speculated that the soil moisture was important for the occurrence of the response patterns.2.We also found that total nematode richness increased with the increase of MAP and decreased with the increase of MAT.However,the interaction between MAT and MAP did not affect soil nematode richness.The response pattern of each trophic group to the MAT and MAP were also consistent with the community level,respectively.According to SEMs,we speculated that soil carbon-nitrogen ratio,carbon-phosphorus ratio,available phosphorus,and plant coverage were important for the occurrence of the response patterns.3.According to the results of distance-based redundancy analysis(db RDA),we found that the composition of soil nematode community was significantly correlated with soil carbon-nitrogen ratio and MAP.The non-metric multidimensional scaling(NMDS)analysis showed that the soil nematode community composition is dispersed when the MAT was higher than 2.5 °C and the MAP was lower than 300 mm or higher than 500 mm.We also found that some omnivorous/predator nematodes were more dispersed than the other trophic groups.For the within-site community similarity,the within-site community similarity of the total soil nematode increased with the increasing MAP and decreased with the increasing MAT.The interaction between MAT and MAP did not affect the within-site community similarity.Additionally,the response patterns of each trophic group were different: the within-site community similarity of bacterivores and fungivores nematode only increased with the increasing of MAP.The within-site community similarities of herbivores and omnivorous/predator nematodes were regulated by both MAP and MAT: when the MAP was lower than 400 mm,the within-site community similarity of these nematode decreased with the increasing MAT,while when the MAP was higher than 400 mm,the within-site community similarity of these nematode increased with the increasing temperature.However,we did not find the effect of soil and plant factors at these response pattern.This study revealed the response patterns of soil nematode community abundance,richness,community composition and community similarity to climatic and geographic factors in alpine grassland of eastern Tibetan Plateau.We found the interaction of temperature and precipitation would alter the effects of temperature and precipitation to soil nematode community on the Tibetan Plateau,but the potential driving mechanism of above finding was complicated.Our knowledge of the response pattern of soil nematode would be benefited by performing more treatment experiment,for example soil temperature treatment and precipitation treatment at locations with400 mm MAP.Even there were some studies on soil nematode at global and regional scale,but the distribution pattern of soil nematode is still unclear.Our study shows that in unique ecosystems,it is still necessary to study the distribution of soil nematodes and explore the underlying driving mechanism by investigation survey and control experiments.