疏花水柏枝残存种群的更新受限及其水生态机制

The surviving populations of endangered Myricaria laxiflora are distributed on several riverbanks along Yangtze River at the downstream of large-scale water conservation and hydropower projects in Hubei and Sichuan province. Its habitat has a special hydroecological environment dominated by summer flooding. Constructions of the large scale water conservancy and hydropower project not only submerge its major habitats in the reservoir, but also change the hydroecological environment where the surviving populations are distributed making the species endangered. The research project is going to focus on the problem of population degradation of surviving populations under the change of hydroecological environment. The crucial scientific issue of population regeneration characteristics and its relationship with hydroecological environment will be studied through a series of field and control experiments.The characteristics of the important stages in population regeneration, including seed development, seed dispersal, seed bank development, seed germination, seedling establishment, seedling growth and morphological building, and their relationship with hydroecological environment are all tested. The requirement and dependence of population regeneration on hydroecological condition are analyzed. Based on the change of hydroecological environment of habitats, the ecological effects of hydroecological environmental change on each stage and total progress of population regeneration are evaluated, and the related hydroecological mechanism of population regeneration limitation is finally uncovered. Suggestions in hydroecological management for the conservation of surviving population are further put forward.

疏花水柏枝（Myricaria laxiflora）残存种群分布于湖北及四川境内大型水利水电工程下游少量河段的长江河滩地，其生境具有由洪水消涨主导的水生态环境。大型水利水电工程的修建不仅淹没了该物种在库区的主要生境地，而且还改变了其残留种群生境的水文条件，使其成为濒危物种。本项目针对该物种残存种群所出现的种群退化的问题，以残存种群生境地水生态环境的改变为研究背景，以种群更新特征及其与水生态环境的关系为核心研究内容，通过野外实验和控制实验，研究该物种群更新过程中种子发育、种子传播、种子库形成、种子萌发与幼苗定居、幼苗生长与形态构建等重要环节的特征及其与水生态环境的关系，分析种群更新对水生态环境的需求与依赖性。并结合残存种群生境地水生态环境的变化特征，评价水生态环境变化对种群更新各环节及整个过程的生态效应与影响，揭示残存种群更新受限的水生态机制，探讨该物种残存种群的水生态保护策略与方法。

为了探究珍稀濒危植物疏花水柏枝种群更新受限的机制，本项目以宜昌胭脂坝为野外试验地，设置长期样带和样方，在对群落和种群结构、种群更新现状、生境地水生态环境实地调查的基础上，结合控制实验，对种群开花结实、种子传播、土壤种子库形成与可持续性、种子萌发与幼苗定居、幼苗生长与功能构件形成、植物光合生理的特征及其与水生态环境的关系进行了系列的研究。结果显示，疏花水柏枝种群的开花结实、种子库的形成与分布受水位消涨的显著影响，消涨带上部植株的开花与结实数量、种子库的多样性和种子数量显著高于中部和下部。土壤种子库可持续性、种子萌发与幼苗定居则与地下水位显著相关。自然条件下，种子库的可持续性相对较低 (10d左右)，且在干燥条件下的可持续性最强。种子的萌发率随土壤含水量的增加而下降，适宜的地下水位（-10cm左右）有利于种子萌发和幼苗生长。植株生长和光合生理也受水位消涨的显著影响，消涨带上部植株的生长显著好于中下部植株，而其光合生理活动也强于中下部植株。进一步的相关性分析表明，疏花水柏枝种群更新的几个关键过程均水生态环境密切相关。三峡大坝和葛洲坝对河流调节所引起的疏花水柏枝残存种群水生态环境的变化是引起其种群更新受限的主要因素。