Emerald ash borer-caused canopy gaps alter resource availability which affects woody plant community dynamics in eastern US forests. Our findings indicate that both canopy trees and seedlings are impacted by the disturbance. Seedlings of sugar maple and introduced woody plants benefited most from ash death, perhaps because they are adapted to ephemeral resource fluctuations. Ash, Fraxinus spp., mortality caused by emerald ash borer (EAB), Agrilus planipennis, results in canopy gaps which could increase resource availability and profoundly affect eastern US forests. We tested two mechanisms: (1) EAB-caused ash decline releases growth of upper forest layers (non-ash canopy and subcanopy trees), constraining any release of lower forest strata; (2) EAB-caused ash decline increases canopy openness, releasing lower strata (shrub and seedling layer). Sites representing a gradient of ash mortality were sampled throughout western Ohio to investigate how forest strata relative growth rates (RGRs) relate to EAB-caused ash mortality. Models including individual and additive effects of ash mortality and upper strata effects on woody seedlings were also investigated. Greater RGR of non-ash canopy trees, particularly maple (Acer spp.), was found in sites with more poor condition ash. Abundance of introduced seedlings was correlated with greater ash mortality and shrub cover. Sugar maple seedling height growth improved with ash loss and more subcanopy basal area (BA). Sites with greater subcanopy BA had greater introduced seedling recruitment and native seedling survival. We found evidence to support both mechanisms. Our findings indicate species best adapted to ephemeral resource fluctuations, specifically sugar maple and introduced seedlings, benefited most from ash death.

中文翻译：

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释放和抑制：森林层对翡翠灰蛀虫（Agrilus planipennis）引起的灰烬死亡的反应

翡翠灰螟引起的树冠间隙改变了资源可用性，从而影响了美国东部森林的木本植物群落动态。我们的研究结果表明，冠层树和幼苗都受到干扰的影响。糖槭的幼苗和引进的木本植物从灰烬中受益最多，这可能是因为它们适应了短暂的资源波动。水曲柳属（Ash, Fraxinus spp.）由翡翠灰螟（EAB）、Agrilus planipennis 引起的死亡导致冠层间隙，这可能会增加资源可用性并深刻影响美国东部的森林。我们测试了两种机制：（1）EAB 引起的灰烬减少释放了上层森林（非灰树冠层和亚冠层树）的生长，限制了较低森林层的任何释放；(2) EAB 引起的灰分下降增加了冠层的开放度，释放了较低的地层（灌木和苗木层）。在俄亥俄州西部对代表灰烬死亡率梯度的地点进行采样，以研究森林地层相对增长率 (RGR) 与 EAB 引起的灰烬死亡率之间的关系。还研究了包括灰分死亡率的个体和累加效应以及上层对木本幼苗的影响的模型。在灰烬状况较差的地点发现了非灰烬树冠树，特别是枫树 (Acer spp.) 的更大 RGR。大量引入的幼苗与较高的灰烬死亡率和灌木覆盖率相关。糖槭幼苗高度生长随着灰分损失和更多的冠层基底面积 (BA) 而得到改善。具有更大亚冠层 BA 的地点具有更大的引入幼苗补充和本地幼苗存活率。我们找到了支持这两种机制的证据。我们的研究结果表明物种最适合短暂的资源波动，