水情变化对鄱阳湖洲滩湿地藜蒿生长与分布格局的驱动机制研究

Currently the relationship between water regime and vegetation is really a hot research topic in the domain of wetland ecolgoy. Water regime is one of the key factors for the growth and distributional pattern of wetland vegetation. Artemisia selengensis, one of the dominant plants in the delta wetland of Poyang Lake, was selected as the study object to study the relationship between water regime and vegetation. The study designed observation experiment in situ to establish a long-term observation of Artemisia selengensis transect with process change of three key environmental factors, viz. hydrology, soil, vegetation. The influenced mechanism of water regime on evolution characteristics of the Artemisia selengensis population was revealed through canonical correspondence analysis (CCA). The flood frequency simulation control experiment, with different flood depth, flood duration, flood frequencies and extreme water regime, was designed to study the adaptive mechanism of the growth and development situation of Artemisia selengensis to the different hydrological rhythms by grey correlation method. The long-term evolution of the distributional pattern of Artemisia selengensis community was analyzed by the remote sensing information extraction techniques in the whole delta wetland of Poyang Lake. The driving mechanism of water regime on the formation and long-term evolution of distributional pattern of Artemisia selengensis community was showed through the regression fitting equation method. The study quantitatively explored the relationship between the water regime and the particular plant, which was helpful to understand the ecological effect and the driving mechanism of the water regime in seasonal lake wetland. The results could provide an important scientific basis for protection and management of the important international vegetation resources and for restoration and reconstruction of the degraded wetland areas in Poyang Lake.

水情与植物关系研究是当前湿地生态学领域热点研究课题，水情变化是湿地植被生长与分布格局演替的核心因素之一。本项目立足于鄱阳湖洲滩湿地，以湿地优势植物—藜蒿为研究对象，从水情—植物关系入手，通过开展原位实验建立水文、土壤与植被关键要素变化过程长期定位观测的藜蒿样带，运用典范对应分析法探明洲滩湿地水情变化要素对藜蒿种群演变特征的影响机制；设计不同淹水深度、淹水历时、淹水频率与极端水情等水文节律情景的淹水频率盆栽模拟控制试验，运用灰色关联度方法阐明藜蒿生长发育态势对水文节律变化的响应机制；并利用遥感信息提取技术，揭示洲滩湿地藜蒿群落分布格局长期演替态势，通过建立回归方程阐明藜蒿群落空间格局形成及其长期演变的水文驱动机制。本研究通过对特定植物与水情关系的定量研究，有助于揭示季节性湖泊湿地水情变化的生态效应与机理，可为鄱阳湖国际重要湿地的植物资源保护与管理及退化区域的生态恢复与重建提供科学依据。

水文过程主导了湖泊湿地植被的分布格局，是湿地生态系统演替和生态功能稳定的主要驱动因子及决定因素。受江湖格局、气候变化和人类活动的共同影响，我国最大淡水湖泊湿地-鄱阳湖湿地水文过程和空间格局都发生显著的变化，突出表现为低水过低，高水过高，极端水文事件发生频率加快。这种由湖泊水文过程变化对湿地植被生长、分布格局和演替趋势会产生哪些影响？湿地植物群落对水文过程变化是如何反馈和响应的？水文过程和植被之间相互作用是否会导致湿地生态系统结构发生变化？为了回答这些问题，项目在分析鄱阳湖水文特性的基础上，借助淹水频率控制试验模拟鄱阳湖水文情势变化，从种群尺度探明极端水情对优势种群植物及其根系生长发育的定量影响；利用光谱特征技术对比分析相同优势植物在不同水情变化作用下的光谱反射率和红边位置特征；采用遥感解译技术从群落尺度阐明湖泊水文过程与植被覆盖面积及分布格局之间的定量关系。结果发现，1）鄱阳湖水位在年尺度上以1998年为最高，在月尺度上逐月平均水位最大值主要发生在1998和1954年，日尺度水位以1998年为最高；历年年均水位演变过程中存在25-32年，19-23年，8-15年以及3-7年4类时间尺度的周期变化规律。2）极端水情变化对藜蒿和灰化苔草的根系生长均具有显著作用，旱化处理有利于藜蒿主根重量和须根重量的增加，长期淹水与旱化处理下的灰化苔草植株生长高度差异不明显。3）湿地植物光谱红边位置由大到小依次为藜蒿群落>南荻群落>灰化苔草群落>芦苇群落。控制试验藜蒿组和灰化苔草组的红边斜率均以处理6试验组为最大，以处理8为最小。4）鄱阳湖湿地植被面积分布呈高滩植被挤占中低滩植被分布空间，中低滩植被呈向更低高程洲滩扩张态势，洲滩湿地植被受五河流域来水影响受长江水位顶托影响较小，更多受流域来水影响更大。研究结果有助于揭示季节性湖泊湿地水情变化的生态效应与机理，对维持鄱阳湖湿地生态系统结构与功能，降低区域生态灾害风险具有重要的理论价值和现实意义。