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

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（ungulates）的种群密度常与近期森林干扰（如火灾、采伐和昆虫暴发）相关，因为干扰带来的资源增加会促进树木更新，进而产生大量可供取食的嫩枝。尽管有蹄类动物在受干扰森林中往往发挥着重要作用，但目前对有蹄类-干扰相互作用的认知却极为匮乏，且森林对干扰的响应研究中常未纳入有蹄类动物的取食作用。在美国东北部，大规模昆虫暴发事件——铁杉球蚜（hemlock wooly adelgid, HWA）——已开始对铁杉林产生直接与间接的重要影响（例如通过预先实施的灾后采伐）。目前尚无研究探讨驼鹿与鹿的活动与这类林冠干扰之间的相互作用。本研究的目标分为两部分：一是明确有蹄类动物对不同类型和强度干扰的响应；二是探究有蹄类与林冠干扰的相互作用对植被、其他生物群落以及生态系统过程的影响。本研究将在“铁杉移除试验”平台的4种处理（各设2次重复）中，通过3项有蹄类活动指标调查驼鹿与鹿的相对丰度：粪便团密度、幼苗及幼树过去被取食的痕迹，以及利用红外相机记录的动物出现情况。此外，本研究还将在受干扰与未受干扰样地中，通过在禁牧围栏样地及其配对对照样地内对木本与草本植被进行取样，监测植被对有蹄类取食的响应。