Canada yew (Taxus canadensis) is a clonal shrub that forms discrete patches and was formerly an important component of forest understories in much of northeastern North America. Following Euro-American settlement, Canada yew has been extirpated or reduced in abundance throughout much of its former range, particularly in the USA; winter browsing by white-tailed deer (Odocoileus virginianus) has been implicated as responsible for much of its decline. Little is known about the factors affecting deer browsing intensity on Canada yew. We examined factors related to browsing intensity on Canada yew across three spatial scales in 29 forest stands in Michigan, USA. Browsing intensity on stems was related principally to two factors acting simultaneously across multiple spatial scales. Browsing intensity was negatively related to amount of Canada yew at the scale of the forest stand and negatively related to distance from the edge of Canada yew patches, effectively creating refugia from browsing. The browsing patterns we observed suggest that yew exists in two alternate stable states: (1) as loose aggregations of small stems or (2) large, dense patches of large stems. The implications of changes in deer density or snow cover to the probability of local persistence of Canada yew are discussed. 1. Introduction It is well accepted that large mammalian herbivores make foraging decisions based on interactions with resources across several spatial scales [1–3]. The collective result of foraging decisions made by herbivores at the plant individual or population level can ultimately influence plant populations, plant community structure, and ecosystem processes [3–6]. Therefore, it is important to understand patterns in ungulate foraging at multiple spatial scales to allow management and conservation efforts for affected plants to be scaled appropriately [2, 7]. Opportunities to better understand spatially dependent browsing patterns by ungulates emerge with Canada yew (Taxus canadensis), a declining species that is sensitive to browsing. Also known as ground hemlock or American yew, Canada yew is a monoecious, evergreen shrub native to the mixed conifer-hardwood forests of the northeastern United States and southeastern Canada [8]. Canada yew has garnered interest as a nontimber forest product over the last 20 years because of its pharmaceutical properties [9, 10]. Prior to Euro-American settlement, it was likely a major ground cover component in late-successional mesic forests of this region [8]. Canada yew has been extirpated or its abundance significantly reduced
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