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是生态变化的一个强有力的因素，它可能有选择地消除占优势的树种，同时以先发制人和拯救性伐木的形式刺激广泛的人类干扰。由于生物和物质的全球移动，树种的选择性倾斜和消失是一个越来越重要的生态系统干扰，值得在区域尺度上进行深入研究。最近，铁杉绵球蚜（HWA）在美国东北部的无阻碍的侵扰提供了一个不寻常的机会和关键的必要性，以研究移除一个关键树种的生态后果，东部铁杉，对森林组成，结构和功能。从北卡罗来纳州到马萨诸塞州，HWA正在造成广泛的死亡率，并开始密集砍伐铁杉，并有可能造成这一生态、文化和经济上重要物种的大范围衰退或灭绝。具体而言，铁杉林下植被稀疏的死亡率可能导致森林生态系统重组的漫长时期，从而导致新的、独特的森林类型和生态系统功能的重大变化，包括分解、氮循环和硝酸盐淋溶的中断。2）通过向HWA工作组分发调查结果和其他基于网络的产品，向公众和土地管理者提供信息; 3）将数据纳入与区域专家和专业人员的现有合作努力;在研究设计、现场技术、以及哈佛森林大学研究生和本科生研究经验（REU）项目学生的数据和实验室分析。

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.