Influence Of Warming And N Deposition On Physiological And Ecological Characteristic Of Leymus Chinesis In The Songnen Grassland

The plant species Leymus chinensis is one of the most important dominant species in Songnen meadow steppe, which play a key role in ecosystem stability and agriculture and animal production in west of northeast China. However, the responses of physiological and ecological characteristics of L. chinensis to warming and nitrogen(N) deposition are still not clear. In this study, the dominant species L. chinensis was selected as our research object, we studied the effects of warming and N addition on the development of individual morphology, phenology, silicon content and population quantitative characteristics of L. chinensis in the field. The main results were shown as follows:(1) The effects of warming and N addition on the development of L. chinensis showed significant difference. The responses of leaf to warming and N addition were higher than stem. N addition improved the development of L. chinensis, and increased leaf number, stem height, etc. Warming significantly suppressed the development of L. chinensis and reduced leaf number, stem height and diameter. Moreover, warming and N addition significantly influenced the clone reproductive capacity of rhizomes, which will affect the offspring population reproduction and alter plant community composition.(2) Warming significantly reduced the nutrients uptake of L. chinensis. Compared to control, the concentrations of K+, Na+, Ca2+, Mg2+, N and P decreased significantl, but increased the ration of C:N, C:P and N:P in leaves of L. chinensis. N addition highly increased the concentrations of Na+, Ca2+, Mg2+ and N in leaves of L. chinensis, reduced P concentration, but no impact on K concentration. N addition significantly reduced the ratio of C:N and increased C:P and N:P. Significant interactive effects of warming and N addition on nutrients of K, Ca, Mg, N, P and C:N were detected.(3) Warming significantly improved the development of silicon in leaves of L. chinensis, while N addition suppressed the development of L. chinensis. Warming reduced the negative effects of N addition on silicon in L. chinensis. The short cell’s taxonomic in graminea is significant because of no disappearance with simulated warming and N addition. The phytolith originated in the long cell and plant intercellular space are more sensitive to warming, and N addition, and could become some new indicators for environmental changes.(4) Warming and N addition significantly affected the population quantitative characteristics of L. chinensis. Warming highly reduced the relative cover, relative density, relative abundance and population height of L. chinensis. N addition increased the relative density, cover and abundance of L. chinensis, which would increase the competition ability of L. chinensis. N addition can reduce the negative effects of warming on development of L. chinensis population.It is concluded that, firstly, warming significantly suppressed the development of leaf and stem, nutrients uptake and reduced the dominant position of L. chinensis, but warming can increase silicon content and improve the stress resistance. Secondly, N addition highly improved the development and nutrients uptake, and increased the dominant position of L. chinensis in Songnen meadow steppe, but N addition had negative effect on silicon formation. Thirdly, N addition can reduce the negative effects of warming on development of the dominant position of L. chinensis population.