Data for: Ongoing regeneration of ash and co-occurring species 20 years following invasion by emerald ash borer

Emerald ash borer (Agrilus planipennis Fairmare) is a destructive invasive insect pest of ash trees (Fraxinus spp.) in North America. Monitoring ash regeneration within post-invasion forests is essential to assess ash persistence in North America. We recorded density of overstory ash [> 10 cm diameter at breast height (DBH)], ash recruits (2-10 cm DBH), ash saplings (≥ 45 cm in height; < 2 cm DBH), and ash seedlings (< 45 cm in height), along with canopy dieback of overstory ash and recruits in four post-invasion areas in south-central Michigan, USA. We also recorded density of all other overstory trees, recruits, saplings, and seedlings by species. Ash regeneration was abundant in recruit (470 ± 68.9 stems per ha), sapling (2,599 ± 336.1 stems per ha), and seedling strata (4,557 ± 557.9 stems per ha). Overall, 47% of overstory ash, 17% of ash recruits, and 7% of ash saplings were dead. More than half of the live overstory ash (54%), and 43% of ash recruits had < 30% dieback, although 33 ± 3.0% of ash recruits had external signs of EAB infestation. Living ash basal area was inversely associated with Quercus rubra and Tilia americana density. Dead ash basal area was not related to tree species composition, indicating that stands with low ash density, and subsequent effects on community structure, were not due to canopy gaps resulting from EAB mortality. Overall, we documented substantial ash regeneration in post-invasion forests despite high mortality of trees > 10 cm DBH.

翡翠灰螟（Emerald ash borer, EAB，学名Agrilus planipennis Fairmare）是危害北美白蜡属（Fraxinus spp.）树木的毁灭性外来入侵蛀干害虫。对入侵后森林内的白蜡更新状况开展监测，是评估北美地区白蜡种群存续能力的核心环节。本研究针对美国密歇根州中南部的4个入侵后林分，调查记录了上层林冠白蜡（胸径（diameter at breast height, DBH）>10厘米）、白蜡幼树（胸径2~10厘米）、白蜡树苗（株高≥45厘米且胸径<2厘米）及白蜡实生苗（株高<45厘米）的密度，同时统计了上层林冠白蜡与幼树的冠层枯梢情况；此外还按物种记录了其余所有上层林冠树木、幼树、树苗及实生苗的密度。白蜡更新种群在幼树层（470±68.9株/公顷）、树苗层（2599±336.1株/公顷）与实生苗层（4557±557.9株/公顷）中均极为丰富。整体而言，上层林冠白蜡的死亡率达47%，白蜡幼树死亡率为17%，白蜡树苗死亡率为7%。超过半数的存活上层林冠白蜡（54%）与43%的白蜡幼树冠层枯梢率低于30%，但有33±3.0%的白蜡幼树表现出EAB侵染的外部症状。存活白蜡的胸高断面积与北美红栎（Quercus rubra）、美洲椴（Tilia americana）的密度呈负相关关系。死亡白蜡的胸高断面积与树木物种组成无显著关联，这表明白蜡密度较低的林分及其对群落结构造成的后续影响，并非由EAB致死引发的林冠空隙所致。综上，尽管胸径>10厘米的白蜡树死亡率较高，但本研究仍在入侵后森林中观测到了规模可观的白蜡更新种群。