Uniform TitleThe effects of urban hydrology and elevated atmospheric deposition on nitrate retention and loss in urban wetlands
NameStander, Emilie (author), Ehrenfeld, Joan (chair), Barkay, Tamar (internal member), Groffman, Peter (internal member), Zhu, Wei-Xing (outside member), Rutgers University, Graduate School - New Brunswick,
SubjectEcology and Evolution,
DescriptionWetlands are known for their ability to process nitrate inputs from uplands and groundwater and thus prevent nitrate discharge to sensitive waters. Wetlands in urban landscapes are subjected to numerous disturbances which may prevent them from serving as N sinks. The objective of this dissertation is to document N cycling in urban wetlands in the context of altered hydrology and elevated atmospheric N deposition, and to determine whether urban wetlands serve as sinks or sources of nitrate to receiving waters.
This study was conducted in palustrine, forested wetlands in northeastern New Jersey. In situ rates of net N mineralization, net nitrification, and denitrification were measured monthly for one year. Water table levels were monitored over five years, and soil and vegetation properties were characterized. Weekly nitrate inputs as throughfall and outputs as leachate were measured for one year and analyzed for stable isotopes of nitrogen and oxygen.
Due to altered hydrology, natural hydrogeomorphic setting was not an effective predictor of N cycling rates in urban wetlands. Many assumptions of functional assessment models used to make wetland management decisions were not met. Alternative models I developed using indicators of specific N functions successfully predicted nitrification rates, but they did not predict denitrification rates. Assessment of biogeochemical functions and reference standard site selection should be based on long-term monitoring of water table levels. Assessment models should be targeted to specific functions and may need to utilize intensive field or laboratory techniques. Local scale factors are better descriptors of N cycling rates than indicators of landscape scale urbanization.
Nitrate inputs were higher in more urban sites, but there was no urban effect in nitrate outputs. Urban wetlands generally retained nitrate, as demonstrated by higher nitrate inputs than outputs. However, two sites did demonstrate overall loss of nitrate. Two other sites exhibited direct leaching of atmospherically-derived nitrate, suggesting a lower capacity for N retention. Nitrate retention is not universal in urban wetlands.
NoteIncludes bibliographical references.
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.