干旱半干旱地区的生态系统受水分和氮素双重限制和驱动，研究降雨格局变化和氮沉降增加对东北半干旱盐碱化草地建群种- - 羊草无性繁殖和有性繁殖权衡和对策的影响，对揭示羊草乃至根茎型禾草种群在全球气候变化影响下的生态适应对策和进化机制具有重要的意义。然而, 在半干旱草地区域该方面的研究至今未见报道。因此，本项目分别以自然和人工生境的羊草为研究对象, 以本地实际降雨情况为背景和依据，通过增减年降雨/浇水量、降雨/浇水间隔时间和施氮及二者耦合的不同处理, 在进行静态和动态的，种群、个体和构件水平上"二性"繁殖资源分配模式、权衡关系研究的基础上，再从生理机制变化的角度，全面分析羊草在繁殖上所采取的适应对策，为阐明"二大"驱动因子变化下的半干旱草地羊草以至根茎型禾草"二性"繁殖如何权衡和繁殖对策如何调整这一科学问题，揭示其繁殖生态学和进化学意义，以及今后草地的科学管理等提供有力的理论和实践依据。

Leymus chinensis, is a dominant species in semi-arid and arid regions ecosystem in northern China, and its reproductive types (sexual and asexual) is considered to be largely determined by precipitation patterns and N deposition. Up to now, there is little known about the detailed process of adaptive evolution of trade-off between sexual and asexual reproductive of this species. The project aims to uncover the detailed infromation underlying the adaptive evolution of the two reproductive types of Leymus chinensis. First, by artifically changing watering volume and corresponding interval in natural and artifical Leymus chinensis habitats, we intend to figure out the process of the reproductive allocation and trade-off among sexual and asexual reproduction in different levels, e.g. population, individual, or different components within one individual. Second, we may further uncover the process of the physiological change that underlaying the switching of the reproductive types of Leymus chinensis. Therefore, the study can not only help us to understanding the evolution process of the reproductive types of Leymus chinensis, but also scientifically guide mangement of the grassland.