Abstract Non-native insects and pathogens can alter the composition and successional trajectories of forests and, in exceptional cases, drive their host trees functionally extinct. Emerald ash borer has killed millions of ash trees in its invaded range across eastern North America. Predicting the future ecological role of ash requires information on the extent of ash regeneration and recruitment in the wake of invasion. Variable levels of ash regeneration have been observed in stands invaded by emerald ash borer, although recruitment rates of young ash trees into the overstory remain unclear. Here, we used forest inventory data to quantify ash recruitment and regeneration across the eastern United States, and we linked these observed patterns to emerald ash borer invasion history. Inventory data from 2013-2018 indicate there has been extensive ash regeneration in invaded regions, totaling > 1,200 seedlings per ha in counties invaded in 2002–2006. Plots in counties with the longest invasion histories contained the highest densities of ash seedlings and saplings, likely due to the high densities of overstory ash in these areas prior to invasion by emerald ash borer. Seedling densities also remained generally unchanged between inventory periods ending in 2007 and 2018 irrespective of invasion history. Despite this widespread regeneration, ash trees in the smallest overstory class died at faster rates than they were recruited from seedlings or saplings, resulting in negative population trajectories on plots that have been invaded for more than ~ 10 years. This trend suggests that ash will continue to decline in abundance and may become functionally extinct across the invaded range of emerald ash borer. However, the future ecological role of ash will ultimately be determined by the iterative production and survival of ash seeds to reproductive ages in the presence of emerald ash borer populations, along with effective management practices.

中文翻译：

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翡翠灰蛀虫入侵后美国东部灰烬的种群动态

摘要 外来昆虫和病原体可以改变森林的组成和演替轨迹，并在特殊情况下导致寄主树木功能性灭绝。翡翠灰螟在其入侵的北美东部地区杀死了数百万棵灰树。预测灰烬未来的生态作用需要有关入侵后灰烬再生和补充程度的信息。在祖母绿灰螟侵入的林分中观察到不同程度的灰再生，尽管幼灰树进入上层的补充率仍不清楚。在这里，我们使用森林清单数据来量化美国东部的灰烬补充和再生，并将这些观察到的模式与祖母绿灰螟入侵历史联系起来。2013 年至 2018 年的清单数据表明，入侵地区出现了广泛的灰烬再生，2002 年至 2006 年入侵的县每公顷总计有超过 1,200 株幼苗。入侵历史最长的县的地块中的灰树苗和树苗密度最高，这可能是由于这些地区在祖母绿灰螟入侵之前具有高密度的上层灰烬。无论入侵历史如何，在 2007 年和 2018 年结束的清单期间，幼苗密度也基本保持不变。尽管这种广泛的再生，最小的覆盖层类中的白蜡树死亡的速度比从幼苗或树苗中招募的速度更快，导致已被入侵超过 10 年的地块的人口轨迹为负。这一趋势表明，灰烬的丰度将继续下降，并可能在祖母绿灰螟入侵的范围内功能性灭绝。然而，灰烬未来的生态作用最终将取决于在祖母绿灰蛀虫种群存在的情况下，灰烬种子的迭代生产和存活到繁殖年龄，以及有效的管理实践。