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，重新占据了新英格兰（New England）南部的史前原生分布区——该区域的驼鹿在近200年前几乎已被彻底灭绝。北方针叶林内高强度的驼鹿取食已导致部分区域林分密度下降、物种组成发生改变，这引发了林务员、野生动物管理者与生态学家的广泛关注与讨论，他们关切驼鹿与白尾鹿（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。哈佛森林（Harvard Forest）与美国地质调查局（USGS）马萨诸塞合作研究单元的研究者合作，启动了一项针对新英格兰南部（SNE）森林中驼鹿与白尾鹿生态作用的长期研究，实验采用实验围栏排除法（experimental exclosures）开展。该实验采用随机区组设计，包含3种处理组：全围栏排除组、部分围栏排除组与对照组。全围栏排除组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通行。部分围栏排除组的围栏底部周长处设有60厘米的开口，可阻挡驼鹿进入，但允许白尾鹿及其他中小型动物通行。该实验设计能够让我们量化三类区域的森林组成与结构：（1）同时暴露于驼鹿与白尾鹿取食的区域；（2）免受驼鹿与白尾鹿取食的区域；（3）暴露于白尾鹿取食但免受驼鹿取食的区域。