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The Controls Of Watershed Nutrient Export, Wilfred M. Wollheim
The Controls Of Watershed Nutrient Export, Wilfred M. Wollheim
Doctoral Dissertations
Anthropogenic nitrogen (N) loading has increased considerably in recent times, yet only a small proportion is generally exported to the coast from most watersheds. This dissertation addresses some of the factors controlling N export from watersheds. The focus is on (1) how N export and N retention change with increased urbanization, and (2) how river networks modify N that is loaded to them.
Urbanization is a major perturbation of the land surface. Chapter 1 uses a budget approach to assess how N retention changes with increased urbanization in small headwater catchments in northeastern Massachusetts, USA. Water runoff, N loading, and …
Evolution Of Chemical Composition Along River Drainage Networks, Maya P. Bhatt
Evolution Of Chemical Composition Along River Drainage Networks, Maya P. Bhatt
Doctoral Dissertations
Surface water chemistry from a tropical and temperate rivers system was studied in order to understand the controls on longitudinal variation of stream chemistry. In the Rio Icacos-Blanco system in Puerto Rico, I examined changes in stream chemistry associated with a change in bedrock composition from intrusive quartz diorite (upstream) to volcaniclasitc material (downstream). Overall, after sea-salt correction, most solutes decreased consistently with distance downstream. The silica to alumina ratio, however, changed sharply with changes in the underlying bedrock. Other indices of weathering rates and processes showed strong similarities despite the change in bedrock. The dominance of silica, alkalinity, calcium …
Wood And Soil-Atmosphere Carbon Dioxide Fluxes From A Tropical Forest Ecosystem, Evilene C. Lopes
Wood And Soil-Atmosphere Carbon Dioxide Fluxes From A Tropical Forest Ecosystem, Evilene C. Lopes
Doctoral Dissertations
Carbon cycling in tropical rainforests is an important component of the global carbon budget. A better understanding of controlling mechanisms and magnitude of CO2 sources from tropical forests will improve our ability to predict future impacts of climate changes. The research presented in this dissertation has focused on determining the magnitude and characteristics of the CO2 flux from tropical wood and soil surfaces.
Stem CO2 fluxes were measured in a tropical moist forest at Tapajos National Forest (TNF) in Brazil and in a tropical wet forest at La Selva Biological Station in Costa Rica (LS) using infrared gas analysis methods. …