芽库对羊草草原群落放牧演替的调控机制

As the base of vegetative reproduction, bud bank is a potential plant community,playing a role in regulating community succession. How the spatiotemporal pattern and type of bud bank respond to disturbance type and intensity is not only an important theoretical question concerning the adaption and evolution of plants, but also an important practical problem regarding vegetation responses to climatic change and human disturbance. However, research with regard to characteristics, mechanisms and ecological functions of bud bank is very limited.Lymus chinese Steppe is an important steppe type of northern China, of which about 90% has degraded to some extent. Vegetative reproduction is the major reproductive form of Lymus chinese steppe, but how bud bank contributes to its community succession under grazing has not been fully understood .This program is to elucidate how bud bank is linked to the succession of Lymus chinese steppe under grazing around the Xilin River in Inner Mongolia.We would compare the spatial-temporal pattern of bud bank between different succession phases,and analyze differences in responses of different bud bank types to grazing intensity. Our purposes are to explore the relevance of bud banks in different species to enlargement and shrinkage of population, and to assess the reproductive contribution of different bud bank types. This programme is very useful for elucidating the mechanisms of bud bank in regulating community succession of steppe under grazing and very important for managing Lymus chinese steppe properly.

芽库作为植物营养繁殖的基础，是潜在植物群落，其对群落演替的驱动作用特别值得关注。芽库时空格局及芽库类型如何响应不同干扰方式和干扰强度不但是与植物适应和进化密切相关的重要理论问题，而且是与预测植被响应气候变化和人类干扰所发生的演变密切相关的重要实践问题。但是，迄今为止，与芽库特性、机制和生态功能相关的研究还非常有限。羊草草原是我国北方重要草地资源,约90%以上发生了不同程度的退化。羊草草原以营养繁殖为主，但在群落尺度开展的芽库对其群落演替的调控作用研究还鲜见报道。鉴于此，本项目拟以内蒙古锡林河流域羊草草原放牧演替群落系列为研究对象，通过比较不同放牧演替阶段芽库的时空格局、分析不同类型芽库对放牧强度的响应差异，探究放牧条件下不同植物芽库的种群增殖能力以及不同类型芽库的繁衍贡献，进而揭示芽库对草原放牧演替的调控机制，为羊草草原管理提供理论依据。

芽库作为植物营养繁殖的基础，在植物种群更新与群落动态中发挥重要作用，其对群落演替的驱动作用特别值得关注。本项目以内蒙古锡林河流域羊草草原为研究对象，通过研究地下芽库大小与组成对放牧方式与强度的响应、比较不同类型芽库对放牧演替不同阶段植物群落更新的相对繁殖贡献、探究芽库对不同围封年限草地植物群落更新的繁殖贡献、揭示内蒙古草原地下芽库大小与组成的空间分布格局及其对环境因子的响应，阐明芽库对草原放牧演替的调控机制以及芽库赋予植物的适应对策及其在群落构建与动态中的作用。研究表明：1）放牧方式对草原地下芽库密度具有显著影响，根茎型与鳞茎型芽库对放牧更为敏感，芽库对放牧的响应因物种及芽库类型而异；2）适当放牧可促进地下芽库对地上植被的整体繁殖贡献，草地围封抑制源于分蘖型芽库的种群更新，而增加根茎型与根蘖型芽库的繁殖贡献；3）草地退化改变不同类型芽库对地上植物种群的相对繁殖贡献，分蘖型芽库在草地退化初期种群更新中发挥更重要的作用，而借助根蘖型芽库的种群更新在退化后期植物群落中更具优势；4）沿自然气候梯度，地下芽库倾向于向炎热、干旱端减小，“保守型”（鳞茎芽）芽库有利于干旱草地中的植物种群维持，“扩展型”（根茎芽）芽库倾向于在相对湿润草地中更具优势。因此，放牧对草原地上植物群落组成与动态的影响可通过其对芽库大小与组成的影响进行调控和预测，芽库大小、组成及其繁殖贡献对放牧和环境变化的响应有助于揭示并预测草地植物群落响应干扰与气候变化下的群落组成、结构与动态。本项目对丰富芽库生态功能研究、推动植物适应性策略理论发展，量化芽库对不同干扰强度与环境因子水平的响应具有积极的推动作用，为草地植被维持与退化草地生态恢复提供了理论依据。