White-tailed deer (Odocoileus virginianus) herbivory in Northeastern Ohio riparian zones: A preference study

Background/Question/Methods

Preferential browsing by large ungulates can have a marked impact on plant community composition and successional processes in riparian zones. However, relatively little research has been done on white-tailed deer (Odocoileus virginianus) herbivory in Eastern riparian communities. The main objective of this study is to determine white-tailed deer browsing preferences for tree and shrub species in riparian zones of Northeastern Ohio. Five sites in total were selected along the Grand River and Pymatuning Creek in Trumbull County, and the Cuyahoga River in Geauga County. In autumn of 2012, three to five 12 x 20 m quadrats were established in a stratified random fashion at each site, and the canopy species composition was surveyed for each quadrat. For individual tree species that had foliage accessible to white-tailed deer the following data were recorded quantitatively and or categorically: total available browse, type of available browse (e.g., epicormic sprouts, perennial foliage), and severity of browsing. The shrub and sapling layer was also sampled within two randomly placed 4x4 m nested plots per 12x20 m overstory quadrat. The Jacob’s Electivity Index was used to determine browsing preferences for tree and shrub species.

Results/Conclusions

As determined by the Jacob’s Electivity Index various tree and shrub species: 1) were consistently avoided at all quadrats where present (bitternut and shagbark hickories, green [swamp] and black ashes, black cherry, American basswood, and American elm), 2) were consistently selected in all quadrats where present (American hornbeam [i.e., Carpinus caroliniana] and black willow), or 3) varied widely in their selection by deer (silver and sugar maples). Floristic composition varied among sites, but was generally similar within sites with few exceptions. The Grand River site was predominantly sugar maple and bitternut hickory, the Cuyahoga River silver maple, green ash, and American elm, and Pymatuning Creek silver maple and shagbark hickory. Quadrats containing sugar and, especially, silver maple with epicormic sprouts due to flood and/or beaver damage had greatest total browsing impact. Preliminary results suggest that white-tailed deer herbivory may actually reflect a marginal value model dictated by patches abundant in such epicormic sprouts rather than strict electivity within patches. Further research is needed to determine potential effects of white-tailed deer in hindering the regeneration of such flood and/or beaver damaged vegetation in Northeastern Ohio riparian zones.