Effects Of Precipitation And Nitrogen Deposition On The Allocation Of The Biomass And Carbohydrate Of Leymus Chinensis In Different Densities

In recent years,the global climate change,which takes precipitation change and nitrogen deposition as main factors,has had a significant impact on ecosystem and has increasingly changed the development direction of grassland ecosystem.Further,the researchers found that the density control also affects the growth and reproduction of plants.So Leymus chinensis which is a typical perennial clonal plant in Songnen plain of the northeast of China,will make corresponding reproductive strategies to adapt to the environmental change.Therefore,it is important for us to understand the effects of precipitation change and nitrogen deposition on the resource allocation of asexual and sexual reproduction in L.chinensis in different densities,which is of great scientific significance for further understanding the ecological adaptation strategies of clonal plants under the background of global climate change.Our study simulated by pot experiment which as L.chinensis an experimental material.We set up the actual local precipitation as a contrast,increasing and decreasing the precipitation(±30%),two levels of nitrogen(0 and 10g·m-2·y-1)and two levels of the density(1500 and 500 no.·m-2).We tested the effects of precipitation change and nitrogen deposition in different densities on the allocation of biomass,soluble sugar and starch between vegetative growth,asexual reproduction and vegetative growth,vegetative shoot and fertile stem.Then we got some conclusions as followed:(1)Enhancing rainfall increased the account for biomass,contents of soluble sugar and starch of vegetative shoot,and reduced these indexes of fertile stem.Also it was different effects of rainfall changes on every vegetative organ.As rainfall enhancing,it was increased to the account for biomass and contents of soluble sugar of stems and leaves,while decreased the contents of starch.Meanwhile,it was decreased to the account for biomass and contents of soluble sugar of the root,while increased the contents of starch.It indicated that when the water was not limited,L.chinensis trended to focus on asexual reproduction and put most of the resources into organs of asexual reproduction,while reduced the resources input for sexual reproduction.(2)Nitrogen addition has no significant effects on the account of biomass,soluble sugar and starch content between asexual reproduction,sexual reproduction and vegetative organs,but the combined effects of nitrogen addition and density treatment had.Only in the low density condition,nitrogen addition improved the account of biomass,soluble sugar and starch content of vegetative shoots,lower resource of the fertile stem.Meanwhile,nitrogen addition increased the account of biomass and soluble sugar content of the stem and leaf,and reduced the starch content,also decreased the account of biomass and soluble sugar content of the root,and improved the starch content.Nitrogen application significantly improved nutritional resources in the environment so that made not limited to nitrogen for the growth of L.chinensis in low density.Thus it is so good for the growth and reproduction of the population to quickly occupy a great habitat.(3)The influence of density dependence on the strategy of growth and reproduction of L.chinensis is mainly reflected in the competitive relationship to environmental resources.Under the condition of certain environmental resources,the low-density treatment reduced the interspecific competition,so that L.chinensis individuals would get more nutrition resources compared with the high-density treatment.The low-density treatment put more resources into the vegetative shoot,and reduced the investment to the fertile stem.So that the account of biomass,soluble sugar and starch content of the vegetative shoot were higher than those of the fertile stem.The same effect occurred to the stem,leaf and root,compared with the high-density treatment,the low-density increased the account of biomass and soluble sugar content of the stem and leaf,reduced the starch content.In addition,L.chinensis will achieve the optimal reproductive strategy by trade-off asexual and sexual reproduction.Under the low-density,increasing rainfall and nitrogen addition will tend to asexual reproduction and reduce the input of sexual reproduction in order to speedy occupy the good habitat.Also it will strengthen the growth of the stem and leaf,weaken the resource of the root,so they obtain more nutrition by the photosynthesis.Based on the resource allocation of asexual and sexual reproduction of L.chinensis,our study expounds of the reproductive strategy under the global climate change,and provides basic data and theory evidence for the ecological adaptation of clonal plants.