Ellison Aaron M, Orwig David A, Fitzpatrick Matthew C, Preisser Evan L
Harvard Forest, Harvard University, 324 North Main Street, Petersham, MA 01366, USA.
Appalachian Laboratory, Center for Environmental Science, University of Maryland, 301 Braddock Road, Frostburg, MD 21532, USA.
Insects. 2018 Nov 23;9(4):172. doi: 10.3390/insects9040172.
The nonnative hemlock woolly adelgid is steadily killing eastern hemlock trees in many parts of eastern North America. We summarize impacts of the adelgid on these forest foundation species; review previous models and analyses of adelgid spread dynamics; and examine how previous forecasts of adelgid spread and ecosystem dynamics compare with current conditions. The adelgid has reset successional sequences, homogenized biological diversity at landscape scales, altered hydrological dynamics, and changed forest stands from carbon sinks into carbon sources. A new model better predicts spread of the adelgid in the south and west of the range of hemlock, but still under-predicts its spread in the north and east. Whether these underpredictions result from inadequately modeling accelerating climate change or accounting for people inadvertently moving the adelgid into new locales needs further study. Ecosystem models of adelgid-driven hemlock dynamics have consistently forecast that forest carbon stocks will be little affected by the shift from hemlock to early-successional mixed hardwood stands, but these forecasts have assumed that the intermediate stages will remain carbon sinks. New forecasting models of adelgid-driven hemlock decline should account for observed abrupt changes in carbon flux and ongoing and accelerating human-driven land-use and climatic changes.
外来物种铁杉球蚜正在稳步杀死北美东部许多地区的东部铁杉树。我们总结了铁杉球蚜对这些森林基础物种的影响；回顾了之前关于铁杉球蚜传播动态的模型和分析；并研究了之前对铁杉球蚜传播和生态系统动态的预测与当前状况的对比情况。铁杉球蚜重置了演替序列，使景观尺度上的生物多样性趋于同质化，改变了水文动态，并将森林从碳汇转变为碳源。一个新模型能更好地预测铁杉球蚜在铁杉分布范围南部和西部的传播，但仍低估了其在北部和东部的传播。这些预测不足是由于对加速气候变化的建模不充分，还是没有考虑到人们无意中将铁杉球蚜转移到新地点，这需要进一步研究。由铁杉球蚜驱动的铁杉动态的生态系统模型一直预测，从铁杉向早期演替的混合硬木林转变对森林碳储量的影响很小，但这些预测假设中间阶段仍将是碳汇。新的由铁杉球蚜驱动的铁杉衰退预测模型应考虑到观察到的碳通量的突然变化以及持续且加速的人类驱动的土地利用和气候变化。
