科研之友
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摘要
The emerald ash borer (EAB) has killed millions of ash trees in Michigan and at least fourteen other states since its first detection near its introduction point in metropolitan Detroit in 2002. Despite overstory ash mortality near 100% in many areas, ash seedling and saplings remain unaffected and provide the potential for ash re-establishment into the canopy of deciduous forests of the region. We examined the potential for ash re-establishment in areas of heavy mortality by measuring the status and change of ash regeneration at 45 sites across southeastern Lower Michigan in 2007 and 2009. Ash regeneration was found to be abundant in all forest types, particularly in the smallest height classes, though it was more abundant in ash species of upland forests compared to those of lowland forests. New seedlings 1-2 years old were less common than other regeneration size classes, and declined substantially between 2007 and 2009, suggesting a depletion of the ash seed bank in these forests. Regeneration density was not explained well by the presence of overstory ash prior to EAB introduction, suggesting that competitive interaction with other tree species in higher canopy strata is an important driver of ash regeneration density. Regeneration is sufficient to replenish overstory ash to pre-EAB levels in upland forests, though ecological changes caused by overstory ash mortality in lowland areas may affect local hydrology in a way that reduces opportunities for tree regeneration. Despite abundant ash regeneration, it remains unclear whether ash will recover to the overstory of forests in southeastern Michigan because of uncertainties in the future dynamics of EAB in the region.
- 出版日期2011-2-1
