Synergy between shading and herbivory triggers macrophyte loss and regime shifts in aquatic systems
Synergy between shading and herbivory triggers macrophyte loss and regime shifts in aquatic systems
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DOI：
10.1111/oik.03104
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发表时间：
2016-10-01
期刊：
影响因子：
3.4
通讯作者：
Hilt, Sabine
中科院分区：
文献类型：
--
作者：
Hidding, Bert;Bakker, Elisabeth S.;Hilt, Sabine
大型植物在浅水生态系统中起着重要的作用。在湖泊中，大型植物稳定了具有高生物多样性的清水条件，它们的下降可能导致向生物多样性较低的浑浊状态的转变。不同的机制被认为是大型植物崩溃的触发因素。水禽和鱼类的食草性似乎是明显的因素之一，但水生植物对食草性的反应是模棱两可的。我们假设，仅靠草食通常不会导致大型植物的崩溃，但附生植物的遮蔽可以增强草食动物的效果。由于从鱼类到大型无脊椎动物再到围生植物的自上而下控制级联的变化，随着富营养化，大型植物的遮荫应该增加。我们通过将大型植物生长模型与不同的草食动物放牧和围生植物遮荫情景进行拟合，详细阐述了这一想法。此外，我们对现有的关于附生植物生长的实验草食动物围隔研究进行了荟萃分析。该模型支持我们提出的假设，回顾的实地研究似乎指向相同的方向。我们认为，显著的食草动物影响可能表明植被对富营养化的恢复能力降低，使其成为大型植物即将崩溃的早期预警信号，导致系统突然转向混浊条件。
Macrophytes play a keystone role in shallow aquatic ecosystems. In lakes, macrophytes stabilize clear-water conditions with high biodiversity and their decline can cause a shift to a turbid state with lower biodiversity. Various mechanisms have been suggested as triggers of macrophyte collapse. Herbivory by waterfowl and fish seems to be one of the obvious factors, but the response of macrophytes to herbivory is ambiguous. We hypothesized that herbivory alone does not typically cause macrophyte collapse, but that shading from periphyton can enhance the effect of herbivores. Shading of macrophytes is supposed to increase with eutrophication due to changes in the top-down control cascading from fish via macroinvertebrates to periphyton. We elaborated on this idea by fitting a macrophyte growth model with different herbivore grazing and periphyton shading scenarios. In addition, we performed a meta-analysis on existing experimental herbivore exclosure studies with respect to periphyton growth. The model supported our proposed hypothesis and the reviewed field studies appeared to point in the same direction. We suggest that a significant herbivore impact may indicate a reduced resilience of vegetation to eutrophication, making it an early warning signal for an imminent macrophyte collapse leading to a sudden shift of the system to turbid conditions.