Impacts of deer browsing on plant diversity and tree composition in Lake States forest
We continue to investigate the impacts of high deer densities on tree regeneration and understory plant diversity in the Lake States forests (Alverson et al. 1988; Waller & Alverson 1997; Rooney 2001; Rooney & Waller 2003). Our initial work focused on hemlock (an old-growth dominant in the region), white cedar (an important community type), and Canada yew (a once ubiquitous but now uncommon shrub). We use the classic tools of demography and experimental exclosures to assess how herb and tree seedling populations respond to local site conditions and regionally variable deer densities (Alverson & Waller 1997; Rooney et al. 2000, 2002).
In a related project, we are investigating the nature, extent, and causes of change in forest plant communities over 50 years. We have access to an excellent historic data set collected by John Curtis (1959) and colleagues and summarized in the classic book: The Vegetation of Wisconsin. We are particularly concerned with documenting rates of species loss across sites, the prevalence of exotics, regional changes in species abundance, and the extent of community homogenization. We find that native species losses are greatest in parks that do not allow deer hunting, thus providing evidence that deer are a major driver of ecological change (Rooney et al. 2004).
We are also working to develop plant indicators, which can be used by managers to monitor deer impacts (Balgooyen & Waller 1995). With support from an EPA Star Fellowship, Tom Rooney investigated how the abundance and demography of white-flowered Trillium (Trillium grandiflorum) populations respond to browsing and related site factors (Rooney & Waller 2001; Rooney & Gross 2003). Such results contribute to our ability to make ecologically informed deer management decisions.
Finally, with Canadian collaborators we wrote a review for the 2004 volume of Annual Review of Ecology, Evolution, and Systematics, highlighting the ecological consequences of overabundant deer populations. This can be found under the publications section.
Building Deer Exclosures
Here is one design that we like for deer exclosures uses 7' black plastic anti-deer fencing. It is currently $213 for 330' or 100m if you buy 4+. This fencing can be strung around existing trees, saving on fenceposts, is easy to repair, already tall enough, and appears quite tough. It also tends to disappear once you're out 20-30 yards, pleasing those concerned about aesthetics in the woods. You can also use plastic zip-ties to secure the fencing to trees and itself (e.g., for repairs or a door). With luck, it will also last a long time, allowing you to re-use it.
Another good resource here.
Waller, D.M. 2007. White-tailed deer impacts and the challenge of managing a hyperabundant herbivore. In Gaston, A.J.; Golumbia, T.E.; Martin, J.-L.; Sharpe, S.T. (eds.), Lessons from the Islands: introduced species and what they tell us about how ecosystems work. Pp. 135-147, Proceedings from the Research Group on Introduced Species 2002 Symposium, Queen Charlotte City, Queen Charlotte Islands, BC. Special Publication, Canadian Wildlife Service, Environment Canada, Ottawa.
Côté, S. D., T. P. Rooney, J.-P. Tremblay, C. Dussault and D. M. Waller. 2004. Ecological impacts of deer overabundance. Ann. Rev. Ecol. Evol. System. 35: 113-147.
Rooney, T. P. and D. M. Waller. 2003. Direct and indirect effects of deer in forest ecosystems. Forest Ecology & Management 181: 165-176.
Rooney, T. P., S. L. Solheim and D. M. Waller. 2002. Factors influencing the regeneration of northern white cedar in lowland forests of the Upper Great Lakes region, USA. Forest Ecology & Management. 163: 119-130.
Rooney, T. P. 2001. Deer impacts on forest ecosystems: a North American perspective. Forestry 74: 201-208.
Rooney, T. P. and D. M. Waller. 2001. How experimental defoliation and leaf height affect growth and reproduction in Trillium grandiflorum. Journal of the Torrey Botanical Society 128: 393-399.
Rooney, T.P., R. J. McCormick, S. L. Solheim and D. M. Waller. 2000. Regional variation in recruitment of eastern hemlock seedlings in the Southern Superior Uplands Section of the Laurentian Mixed Forest Province, USA." Ecological Applications 10: 1119-1132.
Rooney, T. P. and D. M. Waller. 1998. Local and regional variation in hemlock seedling establishment in forests of the upper Great Lakes region, USA. Forest Ecology and Management 111: 211-224.
Alverson, W. S. and D. M. Waller. 1997. Deer populations and the widespread failure of hemlock regeneration in northern forests. The Science of Overabundance: Deer Ecology and Population Management. W. J. McShea, H. B. Underwood and J. H. Rappole. Washington DC, Smithsonian Institution Press: 280-297.
Rooney, T. P. 1997. Escaping herbivory: refuge effects on the morphology and shoot demography of the clonal forest herb, Maianthemum canadense. Torrey Bot. Club 124: 280-285.
Rooney, T. P. and W. Dress 1997. Patterns of plant diversity in overbrowsed old growth and mature second growth hemlock-northern hardwood forest stands. J. Torrey Bot. Soc. 124: 43-51.
Waller, D. M. and W. S. Alverson. 1997. The white-tailed deer: a keystone herbivore. Wildlife Society Bulletin 25: 217-226.
Alverson, W. S., D.M. Waller and S. L. Solheim. 1988. Forests too deer: Edge Effects on northern Wisconsin. Conservation Biology 2: 348-358.