PARENT SESSION
Oral Session #100: Landscape Ecology.
Presiding: T. Crist
Friday, August 9. 9:00 AM to 12:00 PM. Gila Meeting Room, TCC.

Can deer utilization of heterogeneous landscapes alter forest nitrogen budgets?

SEAGLE, STEVEN^*,1, ¹ University of Maryland Center for Environmental Science, Frostburg, MD

ABSTRACT- Large herbivorous ungulates impact forest ecosystem structure and function by suppressing regeneration, altering competitive interactions among tree species, and altering nutrient cycling either directly or indirectly. When forests are interspersed with other land uses, ungulates have the potential to transport nutrients to the forest floor from other land uses in dung and urine if (1) nutrient concentrations are higher in other land uses compared to the forest; (2) the ungulate population is mobile and selectively forages within the landscape for high nutrient food; and (3) behavioral traits of the ungulate dictate utilization of both forest and other high nutrient land uses. Although examples of nutrient transport by foraging ungulates have been previously reported, the interaction of nutrient heterogeneity, landscape structure, and behavior have not been assessed to determine the potential impact of nutrient transport on forest nitrogen budgets. Using white-tailed deer (Odocoileus virginianus) in agricultural landscapes of the eastern United States as an example, I calculate that low and high populations of this ungulate can transport between 2.57 and 10.26 kg N/ha/yr, respectively, into adjacent forest ecosystems when deer deposit nutrients across the landscape randomly. These amounts correspond to approximately 12.5% and 49.9% of estimated total annual atmospheric deposition rates. A nonlinear relationship between percent forest cover and deer nitrogen deposition to the forest floor results if I assume that deer utilize forests 50% of each day for concealment and that this behavioral trait is upheld even as percent forest cover is decreased. For example, the extreme case of 10% forest cover results in 12.83 and 51.3 kg N/ha/yr (62.4% and 249.4% of atmospheric deposition) deposited to the forest floor for low and high deer populations, respectively. Although empirical measures of N transport by white-tailed deer are needed, these calculations clearly hypothesize an important potential impact on forest N budgets, forest productivity, and forest floor processes where deer are overabundant and utilizing heterogeneous agricultural landscapes.

KEY WORDS: nitrogen transport, forest nitrogen budget, landscape heterogeneity, ungulate foraging