Transitioning to functional ecosystem restoration: The relationship between productivity and nitrogen transformation in bottomland hardwood forests.
Schaff, Steven*,1, McLeod, Kenneth 1, 1 U. of Georgia, Aiken, SC, email@example.com
ABSTRACT- Forested wetlands act as a nutrient sink within the landscape by buffering aquatic systems from agricultural runoff, intercepting nutrients before introduction to rivers and streams . Nearly 80% of these wetlands have been destroyed eliminating this functional component of the floodplain landscape. Consequently, agricultural reliance on fertilizer continuously taxes forested wetlands beyond their functional capacity resulting in downstream impacts ranging from algal blooms to anoxia (e.g. the dead zone in the Gulf of Mexico). Ecological restoration is the lynchpin of nearly all remediation plans however little is known about how long it will take before restoration provides a suitable resolution. Therefore, the goal of this study was to investigate the use of alternative restoration methods to promote the rapid development of nutrient cycles and thus the reduction of nitrogen input to aquatic systems. We tested the hypothesis that nitrogen loss from ecosystems is closely linked to plant productivity. A mesocosm study was initiated in 2002 where plant productivity was manipulated in two ways; first by using differing planting densities (0, 2, 6, and 12 individuals per mesocosm) and alternatively by varying the overall growth rate of each mesocosm using an early successional fast growing species (Salix nigra), a slow growing overstory species (Quercus lyrata), both species planted in combination, and an unplanted control. In 2004, the impact of these treatments was assessed by spiking each mesocosm with nitrogen and following its attenuation over time. Results of the experiment show the tree species differ significantly in their ability to promote nitrogen transformation (P<0.0001). Planting density also affected the rate of nitrogen loss (P<0.0001) suggesting dense plantings of bottomland hardwood forest trees may result in increased protection for nearby aquatic ecosystems. Overall productivity increased the rate of nitrogen loss however this relationship depended on the time of year and the species of nitrogen measured. These results suggest maximizing productivity while reestablishing riparian buffer zones will increase nitrogen retention and restore bottomland hardwood forest function.
Key words: bottomland hardwood forest restoration, nitrogen loss, Salix nigra, Quercus lyrata
All materials copyright The Ecological Society of America (ESA), and may not be used without written permission.