西洞庭湖洲滩植物物种与功能多样性空间分布特征及其相关性

    Spatial Distribution and Correlation of Plant Species and Functional Diversity in the Floodplain of West Dongting Lake

    • 摘要: 洞庭湖是长江中下游重要的通江湖泊,具有调蓄洪水和维护周边湿地生态系统及生物多样性等生态功能。研究植物群落物种多样性与功能多样性在异质环境条件下的特征及其相关关系,对认识植物群落分布规律、保护修复生态系统结构和功能具有重要意义。以西洞庭湖沅江和澧水水流方向上的洲滩植物群落为研究对象,采集优势种并测定其根和叶的碳氮磷含量、叶面积和根长等8个功能性状来研究群落间物种多样性差异、水流方向上洲滩群落功能多样性差异、物种多样性和群落功能多样性的关系及多样性指数间的相关性。研究结果表明:(1)沿水流方向不同位置植物群落物种多样性有显著差异。其中,沅江和澧水的水流方向上入湖口物种丰富度均较低;在所有调查区域中,沅江中游洲滩植物群落物种丰富度、香农指数均较高,出湖口的物种多样性最低。(2)澧水上游洲滩植物群落的碳氮磷含量的群落加权平均值(community weighted-mean, CWM)和Rao二次熵指数较高;澧水中游植物群落所有性状的CWM值和Rao二次熵指数最低;沅江上游植物群落具有较高的叶性状值,优势种中一年生草本植物的快速生长策略可能贡献较高的叶性状值。(3)西洞庭湖洲滩植物群落物种多样性与CWM值具有显著相关性,根碳含量的CWM值与物种丰富度、香农指数呈负相关;水流方向上不同位置植物群落物种多样性与Rao二次熵指数没有相关性。研究结果说明,沅、澧两水及沿水流方向不同调查区域的水文地貌特征差异对洲滩湿地植物群落物种和功能多样性都有影响,但拥有更高物种多样性(优势种组成、丰富度等)的植物群落适应能力并不一定更强。此外,沿水流方向,湖泊洲滩植物群落的物种与功能多样性趋异。因此,在西洞庭湖洲滩植物群落的保护和修复工作中需要综合考虑更多因素(如土壤、地形等),以便更全面地了解其生态系统的复杂性和特殊性。

       

      Abstract: Dongting Lake is located in the middle of the Yangtze River flood plain and connects with the Yangtze River, exhibiting crucial ecological roles like flood regulation, preservation of adjacent wetland ecosystems, and fostering biodiversity. The study delves into the characteristics and interconnections among species diversity and functional variety within plant communities existing in diverse environmental settings. Grasping these dynamics proves pivotal in unraveling plant community distribution patterns and safeguarding the ecosystem's structure and functionality. Focusing on the flood-affected shores, this research scrutinizes plant communities influenced by these river surges. It encompasses on-site surveys, gathering dominant species, and scrutinizing eight functional attributes of roots and leaves' carbon, nitrogen, phosphorus concentrations, leaf area ratio, and root length ratio, etc.. The study endeavours to decipher species diversity variations, functional diversity shifts along flood trajectories, associations between species and functional diversity, and correlations within diversity indices. Key findings reveal: (1) Noticeable species diversity disparity aligning with distinct water flow positions. Species richness diminishes notably at the Yuan River and Li River confluence points with the lake. Notably, midstream Yuan River shores display heightened species richness and Shannon's index, while the lake outlet records the lowest species diversity. (2) The midstream Li River plant community exhibits the lowest Community Weighted Mean (CWM) values and Rao's Quadratic Entropy across all traits. Conversely, upstream Li River shores manifest higher CWM values for carbon, nitrogen, and phosphorus concentrations. Additionally, the upstream Yuan River community showcases elevated leaf trait values, possibly attributed to rapid-growth strategies of dominant annual herbaceous plants. (3) A significant correlation emerges between species diversity and CWM of functional diversity parameters among West Dongting Lake's shore plant communities. Root carbon concentration's community-weighted mean shows a negative correlation with species richness and Shannon's index. Nevertheless, no correlation materializes between species diversity and Rao's Quadratic Entropy along different plant community positions along the water flow. The research findings shed light on how the differences in hydro-geomorphic characteristics among the Yuan and Li Rivers, as well as within various surveyed areas along the water flow, impact both the species and functional diversity of wetland plant communities. Interestingly, plant communities with higher species diversity, including dominant species composition and richness, don't necessarily demonstrate greater adaptability. Furthermore, there's a noticeable divergence in species diversity and functional variety along the floodwater's trajectory within the lake shore plant communities. Hence, when undertaking conservation and restoration efforts for the shore plant communities of West Dongting Lake, a comprehensive consideration of multiple factors (such as soil quality, topography, etc.) becomes pivotal for a holistic understanding and management of its intricate and distinctive ecosystem.

       

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