Can ungulates foraging in a multiple-use landscape alter forest nitrogen budgets?

Authors


Steven W. Seagle, Center for Environmental Science, Univ. of Maryland, Appalachian Laboratory, 301 Braddock Road, Frostburg, MD 21532, USA (seagle@al.umces.edu).

Abstract

Ungulates alter nutrient dynamics within many of Earth's ecosystems. However, whether foraging ungulates transfer nutrients among ecosystems at a magnitude sufficient to alter nutrient budgets and associated ecological processes is unknown. I suggest that within eastern North American landscapes dominated by agriculture and forest, the juxtaposition of high nitrogen crops for foraging and forest used for diurnal concealment promotes a net transfer of nitrogen from cropland to forests by overabundant white-tailed deer (Odocoileus virginianus). To estimate the magnitude of this nutrient transfer I apply allometric relationships of deer nitrogen consumption and excretion to populations within a hypothetical landscape in which deer use forest and cropland in equal proportions daily and are not limited in habitat use by landscape spatial pattern. Results indicate a non-linear relationship between deer nitrogen deposition to forest and percent forest cover, with deposition rising toward estimated atmospheric nitrogen deposition when forest covers less than 40% of the landscape. This “spatial subsidy” of nitrogen to the forest-floor represents a previously unrecognized input to the forest nitrogen budget with equally unknown impacts on forest-floor ecosystem processes.

Ancillary