1. Riparian vegetation management alters stream basal resources, but stream ecosystem responses partly depend on top-down interactions with in-stream consumers. Large-bodied omnivores can exert particularly strong influences on stream benthic environments through consumption of food resources and physical disturbance of the benthos. Trophic dynamics studies conducted within the context of reach-scale riparian vegetation manipulations can provide insights into the interactions and relative importance of top-down and bottom-up controls that determine ecosystem response to riparian change.
2. Here, we examine how top-down control by native crayfish omnivores (Cambarus bartonii) interacts with abiotic conditions created by reach-scale removal of riparian rhododendron (Rhododendron maximum) in the southern Appalachian Mountains of the U.S.A. We conducted 32-day trophic experiments by nesting five pairs of electrified (crayfish excluded) and non-electrified (crayfish access) plots within each of two 300-m stream reaches (one control and one rhododendron-removed) for 1 year pre-removal and 2 years post-removal.
3. Algal growth responded positively to the reduced canopy cover (post-rhododendron removal) only under low flow conditions combined with the absence of top-down control by crayfish. Leaf decomposition rates were reduced by c. 40% in the absence of crayfish, but higher inputs of rhododendron leaf litter during the summer following rhododendron removal reduced the effect of crayfish presence on decomposition. Riparian rhododendron removal also significantly increased benthic sediment and fine benthic organic matter, but crayfish exclusion did not affect these stream properties.
4. Potential long-term reductions in crayfish abundance could reduce the top-down effects of crayfish and ultimately lead to higher algal growth and reduced leaf decomposition rates in streams where rhododendron is managed through removal.

中文翻译：

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小龙虾会影响河流生态系统对河岸植被移除的反应吗？

1. 河岸植被管理改变了河流的基础资源，但河流生态系统的反应部分取决于与河流消费者自上而下的相互作用。大型杂食动物可以通过消耗食物资源和对底栖动物的物理干扰对河流底栖环境产生特别强烈的影响。在范围尺度的河岸植被操作背景下进行的营养动力学研究可以深入了解自上而下和自下而上控制的相互作用和相对重要性，这些控制决定了生态系统对河岸变化的响应。
2. 在这里，我们研究了本地小龙虾杂食动物 ( Cambarus bartonii )的自上而下控制如何与美国阿巴拉契亚山脉南部河岸杜鹃 ( Rhododendron maximum )的范围去除所产生的非生物条件相互作用我们进行了为期 32 天的营养实验在两个 300 米的河流河段（一个对照和一个杜鹃花去除）中的每一个内筑巢五对电气化（小龙虾除外）和非电气化（小龙虾通道）地块，用于去除前 1 年和去除后 2 年。
3. 藻类生长仅在低流量条件下与小龙虾自上而下控制的情况下对减少的冠层覆盖（杜鹃花去除后）产生积极响应。叶片分解率降低了c。在没有小龙虾的情况下为 40%，但在去除杜鹃花后的夏季，较高的杜鹃花落叶投入减少了小龙虾存在对分解的影响。去除河岸杜鹃花也显着增加了底栖沉积物和细小的底栖有机质，但排除小龙虾并不会影响这些溪流特性。
4. 小龙虾丰度的潜在长期减少可能会减少小龙虾的自上而下的影响，并最终导致通过去除杜鹃花进行管理的溪流中藻类生长加快并降低叶子分解率。