| Along with the Age of Steam in 18 century,the global climate has been changed by the human agricultural and industrial activities.Nitrogen deposition and rainfall changes have been got more attention by sciensits.The Songnen Grassland,in the east of the Euarsia,has been the representative of the perennial rhizomatous grass,because it is famous for its dominant and constructive guinea grass which has good palatability and high nutritive value.Based on this,our study was conducted in the Songnen grassland,where Leymus.chinensis is the dominant species.We tested the combined effects of rainfall changes and nitrogendeposition on the plant below ground traits(structural,chemical characters)and soil environment.Three levels of precipitation(-30%,0 and +30%)and two levels of N(0 and 10g·m-2·y-1)were set up.To explore how the below ground biomass,root structure traits and chemical traits of L.chinensis were responsed to future climate change.But also provide a theoretical basis for the future management of grassland.The main results listed as follows:tion has no significant effect on below ground biomass.The rhizome had a rising tendency but rootsystem and total below ground biomass had a declining tendency with the N addition.The rainfall change has a signigicant effect on rhizome biomass of L.chinensis.The increasing rainfall increased the rhizome biomass significantly(P<0.05),The rootsystem and total below ground biomass were also decreased.(2)The nitrogen deposition has no significant effect on rhizome structure traits.The rhizome length,surface area showed a rising tendency,per unit biomass of rhizome length showed a decling tendency.The N addition increased rootsystem length,surface area significantly(P<0.05),specific root length and specific surface area showed a rising tendency but no significant effects.The rainfall change has a significant effect on rhizome length,surface area.The increased rainfall has a rising influence on rhizome length,surface area,but per unit biomass of rhizome length was decreased.The increased rainfall has a siginificant delining influence on rootsystem length(P<0.05).Rootsystem surface area,specific root length,specific surface area were decreased with increasing rainfall.Two couple factors had a significant effect on rootsystem structure traits and all of them had a rising tendcy(P<0.05).(3)The nitrogen deposition showed a significant effect on rootsystem content of nitrogen,the ratio of rootsystem carbon to nitrogen、nitrogen to phosphorus,the rhizome content of nitrogen and phosphorus and the rootsystem conten of carbon and nitrogen were increased with the N addition.The rainfall change has no siginicifant effect on rhizome,rootsystem chemical traits.The rhizome content of nitrogen and the rootsystem content of nitrogen have a declining tendency,but the rhizome content of phosphorus and the rootsystem content of carbon have a rising tendency,the rootsystem content of phosphorus was not obvious.The above results in an increase in rainfall,the ratio of rhizome carbon to nitrogen was increased,but the ratio of rhizome nitrogen to phosphorus,carbon to phosphorus were decreased;the ratio of rootsystem carbon to nitrogen,carbon to phosphorus were increased.The nitrogen deposition decreased the ratio of rhizome carbon to nitrogen,carbon to phosphorus;the ratio rhizome of carbon to phosphorus were increased;but the ratio of rootsytem carbon to nitrogen was declined,the ratio of nitrogen to phosphorus,carbon to phosphorus were rose.(4)The nitrogen deposition has significant effect on total phosphorus content,the values C:P,N:P.The total carbon conten and phosphorus content have a declining tendency,the total nitrogen content has a rising tendency.The rainfall change has a significant effect on soil total carbon content,the values of C:N,N:P.The increasing rainfall increased the total carbon content,decreased total phosphorus content and the values of C:N significantly(P<0.05).Thus,the values C:N,C:P have a declining tendency,but values N:P has a rising tendency with increasing rainfall and nitrogen deposition.Based on these results,the increasing rainfall and nitrogen deposition facilitated rhizome growth,indirect improvement of clonal propagation potential and nutrition store of L.chinensis;the increasing rainfall and nitrogen deposition changed structure traits and chemical traits,rootsystem biomass was decreased,the rootsystem length,surface area,specific root length,specific surface area were increased,the content of nitrogen was increased,those were the reasons of enhancing the per surface rootsystem absorptive capacity;the content of carbon,nitrogen,phosphorus of rhizome and rootsystem had a similar tendency with increasing rainfall and nitrogen deposition. |
