PARENT SESSION
Contributed Oral Session 21: Urban Stream Ecosystems
Monday, August 8, 1:30 PM - 5:00 PM, Meeting Room 513 E, Level 5, Palais des congrès de Montréal
The Effects of Urbanization on Nitrate Removal Capacity of Urban Wetlands.
Stander, Emilie*,1, Ehrenfeld, Joan1, 1 Rutgers University, New Brunswick, NJ, estander@eden.rutgers.edu
ABSTRACT- Wetlands are increasingly being viewed and used as management tools to combat the widespread problem of excess nitrogen in surface waters of the United States. This is particularly true in urban or urbanizing watersheds. Wetland functions are frequently assessed based on hydrogeomorphic (HGM) setting, because processes such as nitrogen cycling should reflect sources and flow patterns of water. However, HGM assessment may not be applicable in urban environments because urbanization alters wetland hydrology, thus causing wetlands to function differently than their natural HGM setting would suggest. We tested the ability of HGM classification to explain variations in nitrogen cycling rates in a sample of wetlands in northeastern New Jersey, a heavily developed metropolitan area. Fourteen palustrine, forested wetlands, representing three reference sites in less heavily-developed landscapes, were sampled for hydrology and rates of in situ nitrogen cycling processes to determine the usefulness of the HGM approach. Three clusters of nested piezometers in each site were sampled for one year. One autowell in each site recorded water table measurements four times daily. In situ rates of net nitrogen mineralization and net nitrification were measured monthly during the same time period. Hydrographs demonstrated that many of the wetlands have water table depths below 30 cm for long periods of time. Many wetlands display uncharacteristically flashy hydrographs. In some cases our selected reference wetlands showed more symptoms of altered hydrology than more urban sites. In this region it is therefore necessary to identify reference wetlands based on hydrology monitoring data. There were no differences in nitrification rates among HGM classes. However, wetlands with dry or flashy hydrographs did have higher nitrification rates than wetlands with more normal hydrology. This suggests that urbanization is a better predictor of nitrogen cycling functions than HGM class.
Key words: hydrogeomorphic setting, urban wetlands, nitrification, hydrology