Role of Moose and Deer Browsing in Unharvested Forests of Southern New England since 2011

In the past 25 years, moose have spread south from Vermont and New Hampshire and recolonized their pre-historical range limit in southern New England from which they had been extirpated almost 200 years earlier. Intensive moose browsing in the boreal forest has caused declines in forest density and shifts in species composition in some areas, generating considerable interest and concern among foresters, wildlife managers, and ecologists as to how moose along with white-tailed deer will impact forest regeneration, composition, and diversity in this region. Harvard Forest in collaboration with researchers at the USGS Massachusetts Cooperative Research Unit has initiated a long-term study of the role of moose and deer in SNE forests using experimental exclosures. The design is a randomized block with 3 factors -- full exclosure, partial exclosure, and control plot. Full exclosures exclude both moose and deer but allow access to small mammals such as mice, squirrels, and rabbits. Partial exclosures have a 60cm opening around the bottom perimeter of the fence, which excludes moose but allows access to deer and other small and medium-sized animals. The design enables us to quantify forest composition and structure in areas (1) exposed to moose and deer browsing, (2) protected from moose and deer browsing, and (3) exposed to deer browsing but protected from moose browsing.过去25年间，驼鹿（moose）从佛蒙特州（Vermont）与新罕布什尔州（New Hampshire）向南扩散，并重新占据了新英格兰（New England）南部的史前原分布范围——该范围内的驼鹿曾在近200年前被彻底局部灭绝。北方针叶林（boreal forest）内高强度的驼鹿啃食活动，已导致部分区域的森林密度下降、物种组成发生改变，这引发了林务人员、野生动物管理者与生态学家的广泛关注与担忧，他们亟需厘清驼鹿与白尾鹿（white-tailed deer）将如何影响该区域的森林更新、物种组成与生物多样性。哈佛大学森林（Harvard Forest）联合美国地质调查局（USGS）马萨诸塞合作研究单元的研究人员，启动了一项针对驼鹿与白尾鹿在新英格兰南部森林中生态作用的长期研究，实验采用实验性围栏排除法（experimental exclosures）。该研究采用随机区组设计（randomized block），设置3种处理样地：全围栏排除样地、半围栏排除样地与对照样地。全围栏排除样地可同时阻挡驼鹿与白尾鹿进入，但允许小鼠、松鼠、野兔等小型哺乳动物自由通行；半围栏排除样地的围栏底部周边设有60厘米高的开口，可阻挡驼鹿进入，但允许鹿类及其他中小型动物自由进出。该实验设计可帮助我们量化三类区域的森林组成与结构：（1）同时遭受驼鹿与鹿类啃食的区域；（2）同时免受驼鹿与鹿类啃食的区域；（3）仅遭受鹿类啃食但不受驼鹿啃食的区域。