芽库在黄河三角洲贝壳堤湿地植物群落建成中的调控机制

Bud bank，which is the basis of vegetative propagation，largely determines the population regeneration, dynamics and community assembly. During the restoration process of damaged coastal wetland ecosystems，it is critical to clarify the role of bud banks on vegetation regeneration, population maintenance and responses to heterogeneity of moisture and salt contents. This study would be carried out in typical plant communities of chenier wetland in Yellow River Delta. Responses of bud types, spatial patterns and seasonal dynamics to shell sand water-salt heterogeneity of three dominant herbs (Phragmites australis, Artemisia mongolica and Messerschmidia sibirica) were studied to analyze the heterogeneous environmental controls of bud development and demography, and investigate the fate of various types of buds and their relationship with the formation of aboveground plants. Based on field survey, the reproductive contribution of bud banks was determined. Combined with the indoor experiment，the relationship between bud types, numbers and population density, vegetation coverage were investigated to reveal the regulatory mechanism of bud banks in plant populations renewal. Through the habitat characteristics of water and salt, vegetation characteristics and bud bank structure in typical community, the intrinsic link between habitats, bud banks and vegetation were analyzed. By analyzing bud developments in heterogeneous habitat at individual-level，regulation on population dynamics at population-level, the regulation mechanisms of bud banks in the course of community assembly was revealed. In a word, this study would provide a theoretical basis for the vegetation protection and restoration in the coastal wetland of Yellow River Delta.

芽库是植物营养繁殖的基础，其在很大程度上决定了种群更新与群落构建；弄清芽库对水盐异质生境的响应以及在植被更新中的作用是修复受损海岸湿地生态系统的关键。本项目以黄河三角洲贝壳堤湿地典型植物群落为研究对象，通过室内控制实验研究优势植物各类芽的建立、输出、休眠、空间拓展对水盐异质生境的响应，探讨各类芽的命运及与地上植株形成的关系；在野外调查取样的基础上，分析芽库在种群更新中的繁殖贡献，结合室内实验阐明芽库的构成、数量特征与种群密度、盖度的关系，揭示芽库在种群更新中的调节机理；通过调查典型群落的水盐状况、植被特征和芽库构成，分析三者之间的内在联系，在个体水平和种群水平的研究基础上，对比分析不同植物的芽库构成、数量特征及动态变化，探讨由芽库差异引起的种间相互作用，揭示芽库在贝壳堤湿地植物群落建成中的调控机理，为黄河三角洲贝壳堤湿地植被保护和恢复提供理论依据。

芽库是植物营养繁殖的基础，其在很大程度上决定了种群更新与群落构建；弄清芽库对水盐异质生境的响应以及在植被更新中的作用是修复受损海岸湿地生态系统的关键。本项目以黄河三角洲贝壳堤湿地典型植物群落——芦苇、蒙古蒿（-芦苇）群落为研究对象，室内设置了富水富盐（FF）、贫水多盐（PD）、少水少盐（SS）三个土壤水盐生境，研究了优势植物——芦苇、蒙古蒿、砂引草各类芽的建立、输出、休眠、根茎空间拓展对水盐异质生境的响应；分析了芽库在种群更新中的繁殖贡献，揭示了芽库在种群更新、群落建成中的调控机理。结果表明：黄河三角洲贝壳堤湿地主要以多年生草本植物为主，地下芽库是该地区植物种群更新的主要来源，根颈芽、根茎芽、分蘖芽、根蘖芽和顶芽、腋芽、花芽分别是该地区植物地下芽和地上芽的主要类型，不同植物通过调控地下芽和地上芽的输出从而形成了不同的群落格局。芦苇具有出芽强度低、地下根茎扩展强的保守型出芽特征，在春季以FF生境芽活跃度最高。蒙古蒿和砂引草的地下芽和地上芽库具有此消彼长的生长规律，地上分株主要来源于根颈芽，两者的差异在于：蒙古蒿属于经济型出芽植物，根系主要分布于表层20 cm，每年4月份前大部分活跃芽都转化为新的分株，地上芽量大且分化快，出芽强度高，而砂引草属于奢侈型出芽植物，根系伸扎，在4月份其地上分株输出才刚刚开始，输出量低且植物生长缓慢，出芽强度低，因此其一般在群落中处于从属地位。无论是个体水平还是群落水平下，植物叶面积（群落盖度）、生物量与芽库都成显著正相关（p<0.05）。由于向海侧土壤水盐多变、海浪、风蚀、沙埋频繁等恶劣生境，具根系伸扎的保守型出芽植物-芦苇成为优势植物，形成芦苇植物群落，而滩脊和向陆侧，水盐平和，蒙古蒿发芽早且芽分化快往往成为优势植物群落，而向陆侧一些水分含量稍高的地区，芦苇以其耐淹特性能以分蘖芽生成分株，也能成为与蒙古蒿共生的优势植物群落。