博文
摘要7 暂时性浮岛的形成维持了湿地植物物种丰富度：种子库的作用
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暂时性浮岛的形成维持了湿地植物物种丰富度：种子库的作用
摘要
湿地中，波动的水位为种子库中新个体的更新提供了机会，枯水期通常有利于适宜浅水生活的物种的建立。本研究中，浮岛形成的作用类似于水位降低，它通过在深水沼泽中形成上覆水较少的沉积物斑块。浮岛形成的波动（如垫沙和植被在水柱中垂直上升）也能导致占优势的扎根浮叶植物覆盖率降低，从而为其他物种建立提供了暂时的空斑。为了评估浮岛形成相对于周围的深水沼泽是如何影响湿地植物群集的物种丰富度和物种组成，我们在2年间对浮岛上下植被覆盖百分比进行了调查，同时在温室进行水位涨落控制种子库实验。深水沼泽出现了5个物种而浮岛周围的则有22个种。浮岛的植物群集主要由挺水物种组成，而多年生浮叶植物则在深水沼泽占优势。温室种子库实验中，在进行与野外观察到的水位变化一致的水位处理时，物种丰富度和群集组成在不同水位中呈现了不同。最小水位处理中群集发芽的物种丰富度最高（3.5-4.3种/样方）且含有比那些水位较高的情况下（2.8–2.9种/样方以及<405 个体 m-2）更多的挺水物种（>450 个体 m-2）。本研究不单是温带（如季节性）浮岛唯一的研究报告，还表明了岛屿改变了对于物种更丰富的挺水湿地植物集群有利的水位。因为这些岛屿存在的时间足够长从而使许多物种能够产生种子，它们的形成可能是种子库得以补充和稀有物种种群得以维持的机制之一。
Temporary floating island formation maintains wetland plantspecies richness: The role of the seed bank
Julia A. Cherry a,*, Laura Gough b
a Department of Biological Sciences, University of Alabama, P.O. Box 870206, Tuscaloosa, AL 35487, USA
b Department of Biology, University of Texas at Arlington, P.O. Box 19498, Arlington, TX 76019, USA
Received 14 July 2005; received in revised form 16 January 2006; accepted 20 January 2006
Abstract
In wetlands, fluctuating water levels create opportunities for recruitment of new individuals from seed banks, and drawdown periods often favor the establishment of species adapted for life in shallow water. In this study, floating island formation functioned similarly to drawdowns in water level by creating patches of sediment that were less inundated relative to the surrounding deep water marsh. The disturbance of floating island formation (i.e., mats of sediment and vegetation rising vertically in the water column) also resulted in reduced cover of the dominant rooted, floating-leaved macrophyte, thereby creating temporary gaps for the establishment of other species. To assess how floating island formation influences species richness and composition of wetland plant assemblages relative to surrounding deep water marsh, field surveys of plant percent cover on and off of islands were conducted over 2 years, along with a controlled greenhouse seed bank experiment in which levels of inundation were manipulated. Five plant species were present in deep water marsh compared to 22 in surrounding on floating islands. Plant assemblages on floating islands consisted primarily of emergent species, while floating-leaved perennials dominated the deep water marsh. Species richness and assemblage composition in the greenhouse seed bank experiment differed among water level treatments in a manner consistent with differences observed in field surveys. Assemblages germinating under minimal inundation treatments were more species rich (3.5–4.3 species per sample) and contained more emergent species (>450 individuals m_2) than did those germinating under flooded conditions (2.8–2.9 species per sample and <405 individuals m_2). This study, in addition to being the only reported seed bank study of temporary (i.e., seasonal) floating islands, demonstrates that islands altered levels of inundation favoring the germination of more species-rich, emergent wetland plant assemblages. Because these islands persisted long enough for several species to set seed, their formation may be one mechanism by which the seed bank is replenished and populations of otherwise uncommon species are maintained.
Keywords: Deep water marsh; Drawdown; Floating island; Percent cover; Seed bank
https://blog.sciencenet.cn/blog-272085-400605.html
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