Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 118-124). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Urban stormwater runoff from impervious surfaces reduces water quality and ecological diversity in surrounding streams. The problem is exacerbated in older cities with combined sewer systems like New York City, where roughly 30 billion gallons of untreated sewage and stormwater runoff are combined and dumped into the New York harbor annually. Rain gardens and green roofs are designed to naturally manage stormwater, but both performance data and design guidance are limited. In particular, rain gardens are not optimized for nutrient removal, and US green roofs are commonly planted with non-native vegetation, which may not be optimized for water retention. The first of three studies in this dissertation investigates the overall effect of rain gardens on nutrient removal. Engineers have found there to be tradeoffs between rain garden designs that overall favor greater water retention and those that favor removal of pollutant nutrients, as efficient nutrient removal requires designs that drain slowly, and thus absorb less stormwater. Despite these opposing concerns, this dissertation has found that rain gardens constructed in areas with combined sewer systems should focus on water retention, as the benefits of treating increased amounts of water outweigh admitted downsides, such as the leaching of pollutant nutrients contained in rain garden soil. The second study investigates how nutrient pollution can be reduced in rain gardens. To do this, it quantifies the rate that the rain garden’s soil creates nitrogen pollution, by converting nitrogen from organic to inorganic forms, as inorganic nitrogen is more readily washed out of the soil and into water bodies. Conversely, it also quantifies the amount of nitrogen consumed by plants and also nitrogen emitted in gas form. It then uses the results to construct an overall nitrogen mass balance. The results indicate that the soil used to build rain gardens is in fact too nitrogen rich; inorganic nitrogen supplied by the decomposition of organic nitrogen and by stormwater runoff is far greater than required to maintain vegetative health for rain garden plants. The study concludes that altering rain garden soil specifications could reduce nitrogen pollution. The third study finds that “industry-standard” green roofs planted with drought-tolerant Sedum vegetation might not capture as much stormwater as “next-generation” native systems with irrigation and smart detention. Specifically, the study provides crop coefficients demonstrating reduced evapotranspiration in drought tolerant green roof plants compared to native plants. It also found a native roof’s stormwater capture increased with irrigation and the use of a smart runoff detention system, which automatically reduced the volume of water in the cistern that captures roof runoff in advance of a predicted storm. US government agencies are launching multi-billion dollar greening initiatives that include rain gardens and green roofs designed to manage volumes of stormwater runoff. The research here can assist in quantifying performance and improving green infrastructure designs.

In some continental shelf sediments integrated benthic microalgal biomass is greater than the integrated phytoplankton biomass in the overlying water column. In addition, benthic microalgae may account for up to 10% of the primary production responsible for the coastal fishery yield of the eastern United States. A three-dimensional model of the eastern Gulf of Mexico examines the effects of water-column nutrient sources on the growth of benthic microalgae. To parameterize the exchange of nutrients across the sediment/water interface in these permeable sediments, a non-local exchange submodel was constructed and tested within the framework of the model's grid. Based on the results of the three dimensional simulations, the growth of benthic microalgae from water-column nutrients is highly dependent on the light limitation of overlying phytoplankton. When light is available to phytoplankton in high enough quantities, water-column nutrients are used up before reaching the sediments. When the overlying phytoplankton are light limited, nutrients are able to reach the sediments where the shade adapted benthic microalgae can grow.

Thesis (Ph. D.)--College of William and Mary. / Vita. Includes bibliographical references. Also available online.

The objective of this study was to investigate K, Ca, and Mg immobilization in the stem of species typical of the hardwood forest of southern Quebec. The species examined included American basswood, sugar maple, and white ash from a rich site, and American beech, red oak, and red maple from a poor site. Firstly, rates of immobilization were evaluated over a time span of 40 years. Higher rates of immobilization in the wood only were generally observed on the rich site. Sugar maple immobilized Ca at an elevated rate during 1978--1997, in comparison to the other species on site. In the case of Ca for white ash, and Ca and Mg for red oak, a low wood element concentration and a high rate of growth was associated with a low rate of immobilization. Mean annual immobilization rates on a whole stem basis were also determined for the life of the tree. These results suggest that American basswood and red oak immobilize significant amounts of Mg and Ca in their bark, respectively. / In a second study, concentrations of K, Ca, and Mg across the radial section of the stem (heartwood, transitional, sapwood, and bark) were determined. In a majority of cases, the bark was highest in concentration of base cations. Whereas, for the woody portion of the stem, concentrations were generally highest in the heartwood.

This research was conducted at the University of KwaZulu-Natal, Pietermaritzburg, South Africa. The research encompasses five different studies to assess nutrient cycling in intensive and extensive grazing systems with a view to optimising livestock production. The first study was designed to assess the effect of teff-lucerne mixtures on teff, lucerne and teff-lucerne mixture yields. Lucerne and teff-lucerne mixtures benefited from the association. The overall soil N content of the teff-lucerne mixture plots was greater than the teff alone plots. The second study focused on teff-leucaena association evaluation. It had two leucaena plant row spacings as treatments, 180cm and 120cm, respectively. Teff grown in mixture with leucaena produced a total teff dry matter (DM) of 7931.57 kg ha¯¹ for the 180cm row spacing and 8329.57 for the 120cm row spacing compared to the 3548.93 kg ha¯¹ of DM obtained from the teff alone treatment. The teff-Ieucaena stand also had a greater DM yield response to leucaena row spacing compared to the teff alone. In terms of nutritive quality, all stands from the teff-leucaena plots were better than the quality obtained from the teff alone plots. Total N content of teff from the l80cm row spacing was 21.83 g kg¯¹ and that from the 120cm 16.07 g kg¯¹ compared to the total nitrogen (N) content of 19.77 g kg¯¹ of the teff alone treatment. The total phosphorus (P) content was 2.73, 1.96 and 2.07 g kg¯¹ for the 180cm, 120cm and teff alone treatments respectively. However, the total soil N content was higher for the teff alone plot than for the teff-leucaena plots, which are 1.91, 1.48 and 100 g kg¯¹ for the teff alone, 180cm and 120cm treatments respectively. The third study was designed to assess the effects of different N fertilizer application rates on teff yield response. The rates applied were 0, 50, 100 and 150 kg N ha¯¹. There was significant difference in teff response of the three N fertilizer application rates compared to the control and teff DM yield response was lower for the 150 kg N ha¯¹ (838 kg ha¯¹) treatment compared to the control (553 kg ha¯¹). Both teff DM and nutritive value were higher in the plots treated with N fertilizer than in the plot which received no N fertilizer (control). The soil N content was also higher in those plots treated with N fertilizer. Study four was conducted on the Department of Grassland Science's grassland management techniques trial field at Ukulinga. The effects of nutrient cycling under different management techniques such as burning, mowing and grazing on grass yield response, plant quality and soil nutrients were assessed. However, the response of grass DM yield and P content was not significant but the three treatments had a significant effect on grass N content. Their effect on soil N content was also significant and the grazing plot had the greatest soil N levels. The last study was conducted in the rural areas of Okhombe and Zwelitsha to assess the effects of grazing intensity on grass yield response, plant quality and soil nutrient status at different distances from homesteads. Grass DM yield and nutritive value declined when distance from the homestead increased. The soil N content also was higher nearer to the homestead than further away. Most farmers, particularly in developing countries including those in Eritrea, often experience that their animals prefer forages from some plants such as lucerne, leucaena, and other indigenous leguminous plants. They also observe that they get greater yield from crops grown near leguminous plants or in rotation with legumes. They are also still using manure from their animals to fertilize their croplands. Therefore, it is still the duty of the researchers to demonstrate to farmers on farm studies to convince farmers that it is because leguminous plants have the ability to add quality and quantity to the feed of the animals and soil nutrients to the croplands. Hopefully, this study will convey to farmers the use of growing integrated grassllegume pastures and crops, and illustrate that livestock have their own role in transporting nutrients and hence use them as good means of distributors of soil nutrients. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.

Inclement climate conditions have made the Arctic Ocean logistically difficult to study, and thus, our historical knowledge of Arctic Ocean processes are limited. Recent observations indicate rapid and abrupt changes in climate. These changes are thought to includes rising temperatures, increase storm activity, altered freshwater balance and a notable decrease in the concentration and extent of sea ice covering the Arctic Ocean. Increasing awareness of these changing conditions and our poor knowledge of how the physical environment influences carbon fluxes, planktonic productivity and biogeochemical cycling have lead to international efforts to address these questions. The data presented here addresses biogeochemical cycling and phytoplankton primary production in the pelagic ecosystem. Given the pace of environmental change in the arctic (rapid ice retreat, record minimum ice extents, and temperature rise) and the relatively little historical data that is available for the region, the data presented here can also be used as a baseline data set from which predictions can be made and future observations can be compared. / Conducted as part of the Canadian Arctic Shelf Exchange Study (CASES), this thesis provides a current review of nutrient dynamics and cycling, and estimates of annual new and net primary production for the Mackenzie Shelf, the Amundsen Gulf and the Cape Bathurst polynya in the southeastern Beaufort Sea in the Canadian Arctic Ocean.

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 122-143).

Thesis (Ph.D.)--University of Wollongong, 2004. / Typescript. Includes bibliographical references: leaf 142-167.