Ungulate-Disturbance Interactions in Hemlock Ecosystems at Harvard Forest 2012-2013

Densities of ungulates are often associated with recent forest disturbances such as fire, logging and insect outbreaks, as increased resources stimulate tree regeneration, leading to abundant available browse. Despite the often significant role that ungulates play in disturbed forests, surprisingly little is known about ungulate-disturbance interactions, and ungulate herbivory is often excluded from examinations of forest response to disturbance. In the Northeastern United States, a large-scale insect outbreak, the hemlock wooly adelgid (HWA), has begun to have important effects on hemlock forests both directly and indirectly (i.e., by preemptive salvage logging). No studies have examined the interactions of both moose and deer activity with these associated canopy disturbances. Our objectives are twofold: to determine (1) the response of ungulates to varying disturbance types and intensities and (2) the influence of ungulate interactions with canopy disturbance on vegetation, other biota, and ecosystem processes. We will examine the relative abundance of moose and deer in four treatments (2 replicates) at the Hemlock Removal Experiment using three indices of ungulate activity: pellet group density, evidence of past browsing on seedlings and saplings, and the occurrence of animals using game cameras. We will also monitor the response of vegetation to ungulate browsing by sampling woody and herbaceous vegetation in fenced exclosures and paired controls in disturbed and undisturbed plots.

有蹄类动物（ungulate）的种群密度往往与火灾、伐木、虫害暴发等近期森林干扰密切相关，因为干扰带来的资源增加会促进树木更新，进而形成充足的可食用嫩枝资源。尽管有蹄类动物在受干扰森林中往往发挥着重要作用，但人们对有蹄类动物与干扰的互作关系却知之甚少，且有蹄类动物的植食作用常被排除在森林对干扰的响应研究之外。在美国东北部，大规模虫害暴发导致的铁杉球蚜（Hemlock Woolly Adelgid, HWA）已开始对铁杉林产生直接与间接的重要影响（间接影响体现为预防性打捞伐木）。目前尚无研究探讨驼鹿与鹿的活动与这类冠层干扰之间的互作关系。本研究的目标分为两点：一是明确有蹄类动物对不同类型和强度的森林干扰的响应；二是探究有蹄类动物与冠层干扰的互作对植被、其他生物群落以及生态系统过程的影响。我们将在铁杉移除实验（Hemlock Removal Experiment）样地中，针对4组处理（每组设置2次重复），通过3种有蹄类动物活动指标来评估驼鹿与鹿的相对丰富度：粪便团密度、幼苗及幼树曾被采食的证据，以及利用红外相机记录的动物出现情况。我们还将通过在受干扰与未干扰样地中设置围栏排除区及其配对对照样地，对木本及草本植被进行采样，以监测植被对有蹄类动物采食的响应。