Studies On Ecological Stoichiometry Homeostasis Of Leymus Chinense Under Conditions Of Saline-alkali Stress

Grass specie,Leymus chinensis,grows vigorously with high quality in the grasslands of west Jilin province,which supports local livestock sector.However,the environment for grass growth in this area is deteriorating in terms of serious salinization,decreased productivity and invasion of inferior grasses and other plants,which restricted the development of the local livestock industry and improvement of the ecological systems.In turn,this would adversely affect region’s economic development and social stability.Therefore,vegetation restoration to protect high quality species and the improvement of soil salinization need to be addressed.Lab experiments were designed to investigate the impact of nitrogen(N)and phosphorus(P)addition and saline-alkali on Leymus chinensis using sand culture.The experiments period lasted 55 days in total.At the end of the experiments,biomass,N and P contents in aboveground(Foliage)and underground(Root)parts of plants were measured.Based on the theory of ecological stoichiometry,N,P contents and N/P ratios of the aboveground and underground parts of Leymus chinensis and the corresponding matrix(Sand culture experiment)were studied.Next,the homeostasis index(H,plants with higher H have stronger homeostasis,that is,stronger control of element change)of the Leymus chinensis is calculated and compared by means of homeostatic model of ecological stoichiometry(y=cx1/H),and the homeostatic characteristic of the abovegroundand underground parts of Leymus chinensis under different alkaline environments were analyzed.The results demonstrated that low concentration of N addition(2~16mmol/L)not only increased N content of the aboveground and underground parts of Leymus chinensis,but also stimulated plant P uptake,whereas P addition had no significant effect on N content of Leymus chinensis.High concentrations of N and P addition(N >24mmol/L,P >4.8mmol/L)with high alkaline concentration(pH >9.1)were not conducive to the growth of Leymus chinensis.Leymus chinensis can rationally distribute the nutrient elements in the above-ground and below-ground parts when soil pH was less than 8.4,and the N concentration was 8~24mmol/L.As for Leymus chinensis,the homeostatic of the aboveground part was higher than that of the underground part.Under the condition of different salinity,the homeostatic of N of the above-ground part of Leymus chinensis was higher than that the homeostatic of P,while the homeostatic of P of the below-ground part was higher than that the homeostatic of N.These indicated that above-ground dry matter accumulation mainly depended on N supply while below-ground would be controlled by P supply.The homeostatic of the above-ground part of Leymus chinensis was 4.45~12.93 when soil pH was 7~9.8,while the homeostatic of N and N:P of the below-ground part can not be characterized by the homeostatic model.For long-term high-intensity disturbed ecosystems,the homeostatic of the above-ground part of Leymus chinensis was more sensitive than that of above-ground part.