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. 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. The authors examined 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. They also monitored the response of vegetation to ungulate browsing by sampling woody and herbaceous vegetation in fenced enclosures and paired controls in disturbed and undisturbed plots.

有蹄类动物（ungulates）的种群密度往往与近期森林干扰（如火灾、采伐及虫害爆发）紧密相关，干扰引发的资源补给增加会促进树木更新，进而为有蹄类提供充足的可食用嫩枝。尽管有蹄类在受干扰森林中往往发挥着重要作用，但令人意外的是，学界对有蹄类与森林干扰之间的相互作用却知之甚少，且现有森林对干扰的响应研究往往未纳入有蹄类植食作用（ungulate herbivory）这一因素。在美国东北部，大规模虫害爆发引发的铁杉球蚜（hemlock wooly adelgid, HWA）已对当地铁杉林产生了直接与间接的重要影响，其中间接影响体现为预防性抢救性采伐。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。本研究依托铁杉移除试验（Hemlock Removal Experiment），在4种处理组（每组设置2个重复样地）中，通过三项有蹄类活动监测指标——粪便团密度、幼苗及幼树的既往啃食痕迹，以及红外相机记录的动物出现频次，评估了驼鹿与鹿的相对丰度。此外，研究人员还在受干扰与未受干扰样地内设置围栏排除样地与配对对照样地，通过取样调查木本与草本植被的生长状况，监测植被对有蹄类啃食的响应。