Open Access Thesis
Master of Science (M.S.)
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Once prevalent on the landscape, early-successional habitats are now increasingly threatened in the northeastern United States. As a result, many species that rely on or require habitats dominated by shrubs, young trees, grasses, and forbs have experienced precipitous population declines, leading many organizations to list shrubland habitats and constituent wildlife as a conservation priority. Even-aged forest management (e.g. clearcutting) has been shown to be an efficient and effective means for creating early-successional habitat for certain taxa such as shrubland birds, but it is unfeasible in many situations in southern New England due to public opinion and increased parcelization. Group selection harvests create shrubland conditions in the form of relatively small forest openings (< 1 ha); however, limited attention has been directed toward understanding the extent to which these methods contribute to conservation of early-successional species. In order to assess the conservation value of small forest openings for wildlife in southern New England, I studied two distinct communities associated with early-successional habitats, shrubland birds and bees (Hymenoptera: Apiformes), in openings created by group selection harvests and patch-cutting.
In 2014 and 2015, birds were surveyed in small forest openings in western Massachusetts in an effort to describe relationships between species occurrence and patch area as well as other microhabitat-, patch-, and landscape-level variables. Black-and-white warblers, common yellowthroats, chestnut-sided warblers, eastern towhees, and gray catbirds were likely to be present in openings at least 0.3 ha in size, while indigo buntings and prairie warblers had minimum area requirements of 0.55 and 1.07 ha, respectively. Variables within microhabitat-, patch-, and landscape-levels were important for predicting species occurrence. Most notably, prairie warblers were more likely to occur in openings closer to large patches of habitat such as powerline corridors, even if those openings were small in size. I conclude that, despite their inability to support the entire community of shrubland birds in this region, small forest openings can provide habitat for several species of conservation concern if proper attention is given to promoting suitable microhabitat, patch, and landscape characteristics.
Bees were sampled in openings as well as adjacent mature forest in an effort to describe the bee community, identify environmental variables influencing bee abundance and diversity, and examine the extent to which openings created by forest management may support bees, as well as potentially augment bee populations within adjacent unmanaged forest. Bees were significantly more abundant and diverse in forest openings than mature forest, but species composition was indistinguishable between openings and forest. Abundance and diversity displayed no relationship with opening size in either openings or forest, but were generally positively related to the amount of early-successional habitat on the landscape. Vegetation characteristics within openings were important in shaping bee communities in openings, with abundance and diversity decreasing with vegetation height and increasing with floral abundance. Notably, eusocial, soft-wood-nesting, and small bees exhibited the opposite pattern in adjacent forest, increasing with the succession of openings and decreasing with greater floral abundance within openings. These results suggest that the creation of small forest openings may help to promote bees both in openings and adjacent mature forest, but certain guilds may be negatively affected.
Roberts, Henry Patrick, "Factors Influencing Shrubland Bird and Native Bee Communities in Forest Openings" (2017). Masters Theses. 482.