水交换速度和均匀度是反映水动力特征最重要的两个方面，过慢或不均匀的水交换会造成水体O2、CO2含量下降、氮磷浓度改变，而过快的水交换则会造成水体浑浊度和水流拖曳力增加，从而影响沉水植物的生态过程。可见，水交换速度和均匀度对沉水植物的影响不能简单归结于单一因素的影响，是多种环境因子共同作用的结果，其作用机制复杂，研究却相对匮乏。本项目拟以洱海沉水植物为研究对象，通过野外调查和多梯度模拟实验，从忍耐力的角度探明水交换速度和均匀度与沉水植物时空分布的关系；通过不同水交换速度或均匀度下的其他环境因子实验，阐明非生物因子互作对沉水植物生长及分布的影响；通过不同水交换速度或均匀度下种间竞争实验，阐明生物因子对沉水植物生长及分布的影响；最后整合各项研究成果，系统阐明不同生物、非生物条件下水交换速度和均匀度对洱海沉水植物生长及分布的调控机理，以期为沉水植物的保护和恢复提供理论依据。

The rate and evenness of water exchange are the two most important aspects of hydrodynamic characteristics. Slow or uneven water exchange condition is likely to decrease the contents of O2 and CO2 and alter the contents of water nutrients (e.g. N and P), and fast water exchange usually leads to an increase in the water turbidity and magnifies the negative effect of hydrodynamic force on the colonization of submerged macrophytes. The effects of water exchange condition on characteristics of submerged macrophytes cannot be derived from the effects of several single abiotic factors, and possibly because of this complicatedness, the water exchange effect has scarcely been investigated. In this program, we attempt to explore the regulating mechanisms of water exchange rate and evenness on the growth and distribution of submerged macrophytes in Erhai Lake. We will firstly examine the relationships between plant tempo-spatial distribution and water exchange condition (the rate and evenness of water exchange with other environmental factors) from the perspective of plant tolerance incorporating both filed investigation and multi-level lab experiments. Secondly, we will explore the interactive effects of abiotic factors (between the rate and evenness of water exchange with other environmental factors) for the growth and distribution of submerged macrophytes. Finally, we will investigate the biological mechanism for the community maintaining using competition experiments exploring the competition between different submerged macrophytes under different water exchange conditions. Our results may provide theoretical bases for the protection and recovery of submerged macrophytes.