Forest Response to the Decline of a Dominant Species: Ecosystem to Regional Analyses of the Impact of the Hemlock Woolly Adelgid on Northeastern Forests

外来病原体和有害生物引入森林生态系统代表了一种强大的生态变化因素，它可以选择性地消除优势树种，同时以先发制人和抢救性砍伐的形式刺激广泛的人类干扰。由于生物和物质在全球范围内的流动，树种的选择和灭绝是一个日益重要的生态系统干扰，需要在区域范围内进行深入研究。最近在美国东北部肆虐的铁杉(HWA)提供了一个不同寻常的机会和关键的当务之急，来研究移除关键树种铁杉对森林组成、结构和功能的生态后果。从北卡罗来纳州到马萨诸塞州，HWA正在造成广泛的死亡，并开始密集采伐铁杉，并有可能导致这种在生态、文化和经济上重要的物种在整个范围内减少或灭绝。具体地说，林下稀疏铁杉林的死亡可能导致漫长的森林生态系统重组时期，导致新的、独特的森林类型和生态系统功能的重大变化，包括分解中断、氮循环和硝酸盐淋失。这项研究的广泛影响包括：1)将新的生态发现纳入科学出版物、演示文稿和公共宣传；2)通过向HWA工作组和其他基于网络的产品分发研究结果，向公众和土地管理者提供信息；3)将数据整合到现有的与区域专家和专业人员的合作努力中；以及4)为哈佛森林大学研究生和本科生研究经验(REU)项目的学生提供研究设计、现场技术、数据和实验室分析方面的强大教育培训。

The introduction of exotic pathogens and pests to forest ecosystems represents apowerful agent of ecological change that may selectively remove dominant tree species andsimultaneously stimulate widespread human disturbance in the form of pre-emptive and salvagelogging. Due to the increasing global movement of organisms and materials, the selectivedecline and elimination of tree species is an increasingly important ecosystem disturbance thatwarrants intensive study at stand to regional scales.The recent unimpeded infestation of the hemlock woolly adelgid (HWA) across thenortheastern U.S. provides an unusual opportunity and critical imperative to examine theecological consequences of the removal of a keystone tree species, eastern hemlock, on forestcomposition, structure, and function. HWA is generating widespread mortality and initiatingintensive logging of hemlock from North Carolina to Massachusetts and threatens to produce arange-wide decline or elimination of this ecologically, culturally, and economically importantspecies. Specifically, mortality of hemlock stands with sparse understories may lead toa lengthy period of forest ecosystem reorganization resulting in new, distinct forest types andmajor changes in ecosystem function including disruption of decomposition, nitrogen cycling andnitrate leaching.Broader impacts from this study include: 1) incorporation of new ecological findings intoscientific publications, presentations, and public outreach; 2) informing the public and landmanagers by distributing findings to the HWA working group and other web-based products; 3)integration of data into existing collaborative efforts with regional experts and professionals; and4) strong educational training in research design, field techniques, and data and laboratoryanalyses for students in the graduate and Research Experience for Undergraduate (REU)programs at the Harvard Forest.