三江平原沼泽湿地植被群落分布的水文驱动机制

Hydrological regime is the most important factor that controls the formation and evolution of wetland ecosystem. Change in hydrology will result in the change in the spatial distribution pattern of vegetation communities, and influence the structure and function of the whole wetland ecosystem. Change in hydrological regime during global change and human activities has resulted in extensive degradation in wetlands all over the world, and threatened the stability and health of wetland ecosystems. Relationship between hydrology and vegetation in wetland is a hotspot in the research of wetland ecohydrology. Hydrological drivers in the spatial distribution of wetland vegetation communities is the foundation for the assessment of impact of global change and human activities on wetland ecosystem. This research, with typical wetland vegetation communities as objects, attempts to explain the coupling relationship between ecological characteristics of wetland vegetation communities and hydrological regime, quantify the hydrological tolerance of wetland vegetation communities, and then illuminate the driving mechanism for the spatial distribution of vegetation communities based on the modeling of potential spatial distribution of vegetation communities in wetland. This research is instructive in the research on the relationship between hydrology and vegetation in wetland ecosystem, and helpful for the further understanding of formation and evolution of wetland ecosystem, and the relationship between structure and function of wetland. This research will enrich the research content and theory of wetland ecohydrology. Additionally, this research will also provide scientific basis for the ecological restoration and reestablishment of degraded wetland ecosystems and the protection and management of wetland ecosystem.

水文情势是湿地形成与维持的最重要决定性因子。水文条件变化将直接导致植物群落空间分布格局改变，进而影响整个湿地生态系统结构与功能。全球变化和人类活动导致的水文情势改变已造成大面积的湿地退化，并严重威胁湿地生态系统的稳定和健康。开展湿地植群落分布格局的水文驱动机制研究，是科学评估全球变化和人类活动对湿地生态系统影响的基础和关键。本研究以典型湿地植被群落为研究对象，通过植被群落生态特征与水文情势的耦合研究，量化主要湿地植被群落的水文耐受能力，阐明其空间分布的水文驱动机制，探讨水文情势变化下湿地植被群落的分布格局，有助于揭示湿地水文-植被的相互关系，更好地理解湿地系统的发育和演替过程以及湿地结构和功能的关系，完善湿地生态水文学的研究内容和方法，具有重要的理论意义；同时本研究结果也可为退化湿地生态修复与重建以及湿地生态系统保护和管理提供科学依据，具有显著的应用价值。

选择三江平原典型湿地为研究对象，揭示了湿地水文情势的变化过程及其驱动机制；阐明了湿地植被群落的格局及其动态；量化了不同类型湿地植被的水文耐受能力及敏感性；预测和模拟了不同水分梯度下的湿地植被群落格局动态。研究表明，利用水量平衡模型可以对湿地水位进行较为精确的模拟；浓江周期性洪泛对湿地水源补给具有决定作用，人类活动对地表水文格局的改变，直接改变了湿地的水文情势。湿地植物群落具有明显的环境梯度特征，水文和生态空间格局的耦合特征，可以通过一些特定植物群落格局特征展现出来。由于人为活动显著改变了湿地的水文情势，导致湿地水分梯度特征发生显著变化，最终必然引发生态系统结构和空间格局的变化。建立了一种数学方法来定量统一表达湿地水文梯度的空间分异。水分梯度控制下湿地植被景观呈显著的水平地带性规律。水深过高或者过低物种的多样性指数和丰富度指数都相对较低。量化确定了典型湿地植被高度，密度与生物量与水分梯度的量化关系，确定了其水文生态幅。小叶章、毛苔草、漂筏苔草基于高度最大值的水分梯度依次为： 0.40、0.50、0.60；基于密度最大值的水分梯度依次为 0.36、0.40、0.55；基于地上生物量最大值的水分梯度依次为 0.38、0.42、0.50。确定了不同水分梯度下典型湿地植被的分布概率。基于分布概率的小叶章水分梯度最适区间为[0.087，0.411]，最高分布概率的水分梯度0.249;基于分布概率的毛苔草水分梯度最适区间为[0.351，0.569]，最高分布概率的水分梯度0.46；基于分布概率的漂筏苔草水分梯度最适区间为[0.49，0.766]，最高分布概率的水分梯度0.628。模拟了典型湿地植被分布对水文梯度变化的响应，通过随机抽样法和样带验证法对模型进行了验证，模型可用于预测水分梯度分异下的植被类型及其分布概率，确定其最佳适宜生境分布格局。本研究的开展有助于深入了解湿地生态格局和过程，进一步完善湿地生态水文学研究理论和方法体系。同时也为退化湿地的健康评价、生态修复与重建以及湿地保护和管理提供科学依据。