鄱阳湖极端水情对典型洲滩湿地植被群落稳定性的影响机制

The frequent occurrence of extreme hydrological regime of Poyang Lake has broken the dynamic balance between the wetland ecosystem and the periodic hydrological changes. It has seriously threatened the integrity and stability of the wetland ecosystem, and affected the structure and function of the wetland ecosystem. In this study, aiming at the deficiency of the previous research on wetland vegetation in Poyang Lake area, through the field monitoring and investigation, the methods of principal component analysis and Godron stability analysis method were used to quantitatively evaluate the stability and spatial distribution of vegetation communities in a typical wetland. The relationship between diversity and stability of different vegetation communities and the changes of key hydrological elements was studied. Through the control experiments, the tolerance ranges of typical wetland vegetation to flooding and drought stress were explored, and the synergistic influence mechanism of different extreme hydrological regimes on typical Wetland vegetation communities was also revealed. Based on a two-dimensional hydrodynamic model of Poyang Lake, the flood and drought scenarios with different severities were constructed to analyze the distribution and growth situation of typical wetland vegetation and predict the trends of diversity and stability of vegetation communities under different extreme hydrological scenarios. The results are of scientific significance to reveal the distribution pattern and succession of vegetation communities in the Poyang Lake wetland under the influence of extreme hydrology, and also play an important supporting role in maintaining the health of the whole wetland ecosystem and ensuring the ecological service function.

鄱阳湖区极端水情频繁出现，打破了湿地生态系统与周期性水文变化之间的动态平衡，已严重威胁湿地生态系统的完整性和稳定性，影响湿地生态系统的结构与功能。本研究以鄱阳湖典型洲滩湿地植被群落为对象，通过野外监测与样方调查，分别基于主成分分析法和Godron稳定性测定方法，定量评价典型湿地植被群落稳定性及其空间分异特征；研究不同湿地植被群落多样性、稳定性对关键水情要素变化的响应关系；通过控制试验，探明典型湿地植被对淹水与干旱胁迫的耐受范围、阈值，揭示不同极端水情对典型湿地植被群落的协同作用机制；并利用鄱阳湖二维水动力模型构建不同级别洪水和枯水情景，分析典型湿地植被在不同极端水情情景下的分布和生长态势，预测不同湿地植被群落多样性、稳定性的变化趋势。研究结果对揭示极端水情影响下鄱阳湖湿地植被群落分布格局、演替规律具有重要的科学意义，也对维持整个湿地生态系统的健康、保障生态服务功能的发挥具有重要的支撑作用。

鄱阳湖区极端水情频繁出现，严重威胁湿地生态系统的完整性和稳定性，影响湿地生态系统的结构与功能。本项研究在分析鄱阳湖湖泊-流域系统水文干旱的基础上，通过融合Landsat和MODIS遥感影像数据，解译了2000-2020年鄱阳湖洪泛湿地植被空间分布格局及转移变化过程，定量研究了典型湿地植被群落稳定性及其空间分异特征，并分析了不同湿地植被群落稳定性、多样性对关键水情要素变化的响应关系。主要结论如下：(1) 鄱阳湖-流域系统、鄱阳湖-长江系统的水文干旱联合概率分别为8.75%和12.40%，鄱阳湖干旱与长江来水的关系更紧密，但2003年后鄱阳湖-流域系统水文干旱同时发生的频次多于鄱阳湖-长江系统，流域补给减少对鄱阳湖水文干旱的影响也不容忽视。(2) 遥感时空融合为鄱阳湖湿地植被精细化分类提供了良好的数据基础，基于物候特征的决策树分类方法将研究区解译为水体、泥滩、浮叶植物群落、蓼子草-虉草群落、苔草群落、芦荻群落、蒌蒿群落和林地八种景观，总体分类精度达89.36%。(3) 鄱阳湖湿地植被总面积整体呈显著增加趋势，其中蓼子草-虉草群落的增加最为明显；在2000-2020年间，鄱阳湖湿地景观演变趋势呈现出从水体→泥滩→低滩地植被到苔草群落与芦荻群落相互转化的过渡性特征，整体表现出高滩地的芦苇、南荻等向低滩地扩张，而低滩地的苔草、虉草、蓼子草等向湖心扩张的态势。(4) 芦苇-南荻群落的Shannon-Wiener指数和稳定性都显著高于狗牙根群落；狗牙根群落稳定性在丰水期明显低于其他时段；芦苇-南荻群落的稳定性在退水期和枯水期较高；当土壤含水量在15-20%时，狗牙根群落稳定性最高，而当土壤含水量在35-40%时，芦苇-南荻群落稳定性最高。本项目研究结果对进一步认识干旱加剧影响下鄱阳湖湿地植被群落分布格局、演替规律具有重要的科学意义，也对维持整个湿地生态系统的健康、保障生态服务功能的发挥具有重要的支撑作用。