洞庭湖湿地植物繁殖库特征及其对水位变化的响应机制

Both sexual and asexual components (seed and bud banks) of propagule banks contribute to species composition and recruitments of aboveground plant communities. Moreover, plant investment into propagule banks and regeneration of propagule banks into aboveground communities were impacted by hydrological changes. However, most of the current studies emphasized one component of propagule banks, i.e., seed banks or bud banks, which constrain our understanding on mechanisms of plant community recruitment and succession. We will investigate the density, species composition and seasonal dynamics of propagule banks of communities in different successional stages (Phalaris arundinacea—Carex sp.—Miscanthus sacchariflorus）to evaluate the recruitment potential of propagule banks in the typical Yangtze River connected lake–Dongting Lake wetlands. We will quantify the contribution of seed banks and bud banks in recruitment of aboveground shoots by marking, tracking, and identifying shoot source for each individual in the sampling quadrats. We will reveal the response mechanisms of plant investment into propagule banks as well as regeneration of propagule banks into aboveground communities to water level changes by reciprocal transplantation of communities in different elevations and water-level control experiments. Based on the results from propagule bank dynamics, community recruitment, plant reproductive investment and propagule bank regeneration, we expect to clarify the characteristics of propagule banks and its response mechanisms to water level changes in Dongting Lake wetlands. This project can supplement the theory of plant propagule banks and provide guidance for wetland vegetation restoration and reconstruction.

植物繁殖库的有性和无性组分（种子库和芽库）均对地表群落物种组成和更新具有重要作用，并且地表群落对繁殖库的投资以及繁殖库输出形成地表群落均受到湿地水文情势的调控，但当前研究仅关注繁殖库的某一组分，限制了对湿地植物群落更新和演替机理的认识。本项目拟以我国最为典型的通江湖泊—洞庭湖湿地为对象，通过野外调查不同演替阶段（虉草—苔草—荻）植物繁殖库的密度、物种组成和季节动态，评估繁殖库对不同演替阶段地表群落的更新潜力；通过野外标记、跟踪调查、形态溯源等手段量化种子库和芽库对不同演替阶段植物群落更新的贡献；通过不同高程植物群落/繁殖库相互移植和水位控制实验阐明植物繁殖库投资和繁殖库输出对水位变化的响应机制。以期从繁殖库动态、群落更新、植物繁殖库投资和繁殖库输出等方面综合阐明洞庭湖湿地植物繁殖库特征及其对水位变化的响应机制。本项目对于完善植物繁殖库理论及指导湿地植被恢复和重建等方面具有重要意义。

本项目以洞庭湖湿地典型优势植物群落苔草和荻为研究对象，通过野外调查、室内萌发及模拟控制实验等手段，评估了种子库和芽库对不同演替阶段植物群落的更新潜力，揭示了优势植物群落繁殖库投资和输出对水位变化的响应及内在机理。主要结论如下：（1）苔草与荻群落的生物量、植株密度、芽库密度和种子库密度存在显著差异，并且受季节的影响显著。（2）荻群落的芽库主要由荻、芦苇和苔草组成；苔草群落的芽库仅有苔草1种植物；荻群落的芽库由根茎腋芽、长根茎芽和短根茎芽三种类型的芽组成，苔草的芽库由长根茎芽和短根茎芽两种类型的芽组成。（3）两种植物群落的土壤种子库与地表群落的相似性系数均较低；种子库密度在土壤表层（0-5cm）最大，随土壤深度的增加而快速下降；芽库主要分布在0-10cm土层。（4）两种植物群落的土壤种子库密度在冬季最低，洪水前最高；芽库的密度与之相反，在冬季最高，洪水前最低；冬季的芽库密度与春季地表群落的密度呈显著正相关。（5）荻群落繁殖库形成地表群落的物种丰富度、多样性指数和生物量随着水位的升高呈下降趋势；苔草群落繁殖库形成地表群落的生物量在-20至20cm水位之间差异不显著，但在40 cm水位条件下不能形成地表群落。