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

外来病原体和害虫进入森林生态系统代表了生态变化的强大因素，它可以选择性地去除优势树种，同时以先发制人和救助性采伐的形式刺激广泛的人类干扰。随着生物和物质在全球范围内移动的增加，树种的选择性减少和消失是一个日益重要的生态系统干扰，需要在林分到区域尺度上进行深入的研究。最近，铁杉绵蚜（HWA）在美国东北部的无阻碍侵扰提供了一个不寻常的机会和关键的必要来检查移除一个关键树种，东部铁杉，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造成了广泛的死亡，并开始了对铁杉的密集砍伐，并威胁到这种在生态、文化和经济上都很重要的物种的广泛减少或灭绝。具体而言，林底稀疏的铁杉林的死亡可能导致森林生态系统的长时间重组，从而产生新的、不同的森林类型和生态系统功能的重大变化，包括分解、氮循环和硝酸盐淋滤的破坏。本研究的更广泛影响包括：1)将新的生态学发现纳入科学出版物、报告和公众宣传中；2)将调查结果分发给环管局工作小组和其他网络产品，告知公众和土地管理者；3)将数据整合到与区域专家和专业人员的现有协作工作中；4)在研究设计、现场技术、数据和实验室分析方面为哈佛森林大学研究生和本科生研究经验（REU）项目的学生提供强有力的教育培训。

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.