Carbon And Nitrogen Dynamics In Urban Ecosystems
Chapter 1: Urban areas are growing in size and importance; however we are only beginning to understand how the process of urbanization influences ecosystem dynamics. In particular, there have been few assessments of how the land use history and age of residential soils influence carbon and nitrogen pools and fluxes, especially at depth. In this study, we used one-meter soil cores to evaluate soil profile characteristics and carbon and nitrogen pools in 32 residential home lawns that differed by previous land use and age, but had similar soil types. These were compared to soils from 8 forested reference sites. Chapter 2: The rapid increase in residential land area in the United States has raised concern about water pollution associated with nitrogen fertilizers. Nitrate (NO[-] ) is the form of reactive N that is most susceptible to leaching and 3 runoff; thus, a more thorough understanding of nitrification and NO[-] avail3 ability is needed if we are to accurately predict the consequences of residential expansion for water quality. In this study, we evaluated potential net nitrification and mineralization, microbial respiration and biomass, and soil NO[-] and 3 NH+ pools in residential home lawns and forests. 4 Chapter 3: We previously created a mass balance for residential lawns, however, a major N flux was missing - gaseous losses from denitrification. Using recent advances in instrumentation, we were able to measure field-relevant rates of denitrification from lawns. We calculated annual denitrification rates of 14.0 ± 3.6 kg N/ha/yr for the lawns in this study, which suggests that denitrification is an important means of removing reactive N from the residential landscape. Further work is required before these findings can be generalized to a wider range of residential lawns and soils. Chapter 4: Economic and political realities present challenges for implementing an aggressive climate change abatement program in the United States. A high efficiency approach will be essential. In this synthesis, we compared carbon budgets and evaluated carbon mitigation costs for nine counties across the northeastern United States that represent a range of biophysical, demographic and socioeconomic conditions.
Carbon; Nitrogen; Urban
Fahey, Timothy James
Petrovic, Anthony Martin; Yavitt, Joseph B
Ph. D., Natural Resources
Doctor of Philosophy
dissertation or thesis