Much attention has been paid to the effects of anthropogenic impacts upon physical and chemical conditions in freshwater ecosystems. However, impacts upon the functioning of these ecosystems and services that they provide remain relatively unknown. The objective of this thesis was to examine the validity of the general hypothesis that the deterioration of ecosystems may be reflected in their capacity to process resources. Changes in stream phosphorus retention and metabolism were investigated across a rural-urban gradient in the Torrens River Catchment, South Australia, where channel structures of rural reaches are less modified than urban reaches. In a stream with an intact upper rural catchment (First Creek), a reach with an un-modified channel structure retained 60% ± 12.1 filterable reactive phosphorus (FRP) and had an average uptake length of 79 m ± 3.4. In comparison, degraded and engineered reaches of First Creek retained less FRP and had longer uptake lengths. In Fourth Creek, which is influenced by agriculture, there were no differences in FRP retention between the reaches. Reduced FRP retention in impacted reaches were a result of decreased contact time, reduced period of continuous flow and increased nutrient availability. Although abiotic benthic FRP uptake rates (up to 6.8 μg m [ superscript minus 2 ] s [ superscript minus 1 ] ± 0.36) were consistently greater than biotic uptake rates (up to 3.6 μg m [ superscript minus 2 ] s [ superscript minus 1 ] ± 0.52), decreased total benthic uptake rates in impacted reaches were mainly due to decreased biotic uptake. Metabolic rates were measured within benthic chambers containing rocks and gravel and scaled up to the stream reach. At chamber and reach scales, metabolic rates in the unmodified reach of First Creek were consistently low (community respiration (CR) up to 113 mg O [ subscript 2 ] m [ superscript minus 2 ] day [ superscript minus 1 ] ± 47.4 and gross primary production (GPP) up to 234 mg O [ subscript 2 ] m [ superscript minus 2 ] day [ superscript minus 1 ] ± 89.5), with a positive net ecosystem production (NEP). In comparison, the degraded reach of First Creek switched between having a negative and positive NEP. Reaches of Fourth Creek also experienced considerable variation and had higher metabolic rates than First Creek (CR up to 371 mg O [ subscript 2 ] m [ superscript minus 2 ] day [ superscript minus 1 ] ± 62.1 and GPP up to 847 mg O [ subscript 2 ] m [ superscript minus 2 ] day [ superscript minus 1 ] ± 66.1). Increased metabolic rates in impacted reaches were attributed to increased light availability and reduced grazing by higher trophic levels, promoting autotrophic organisms. The altered ecosystem functions were considered to reflect a reduced capacity of deteriorated streams to process resources. However, the addition of coarse particulate organic matter to a degraded-urban stream reach increased CR and reduced NEP to levels more akin to those experienced within pristine streams. Furthermore, percent FRP retention increased, primarily through increased demand for phosphorus of the microbial community. Although this demonstrated that rehabilitation of in-stream attributes might restore important ecosystem functions in impacted streams, successful restoration will only be achieved if the over-riding causes of in-stream degradation are addressed. / Thesis (Ph.D.)--School of Earth and Environmental Sciences, 2005.

Seasonal trends in water table level and soil moisture for four plant community types within an irrigated eastern Oregon riparian zone were described. Aboveground biomass, species composition, litter, percent bareground and percent basal cover of key plant species and life forms were measured. The relationship between water table levels and soil moisture content were analyzed using simple linear regression. Transition zones between plant community types based on soil moisture and/or depth to water table during the growing season were determined. The soil moisture-water table relationship can be used to predict changes in plant community composition induced by a permanent depth to water table change. Irrigation impact on meadow water table levels and stream temperature were determined. Water table levels responded to irrigation manipulations within days. The permanent cessation of irrigation would shrink the riparian meadows contained within this study from widths in excess of 300 m to less than 60 m. Continuous stream temperature data were collected on a stream running through adjacent non-irrigated and irrigated meadows. Daily maximum stream temperatures in the segment contained within the irrigated meadow were 1.0�� to 3.0�� C cooler than the reach contained within the non-irrigated meadow. Management impact on plant community attributes, forage production and forage quality were assessed under three pasture management alternatives. Comparison of stubble height, litter, forage production, forage quality, species composition, percent bareground and percent basal cover of key plant species and life forms indicated all three management alternatives are sustainable from both a plant community and a livestock production perspective. / Graduation date: 1996

Thesis (Ph. D.)--Oregon State University, 2002. / Typescript (photocopy). Includes bibliographical references (leaves 136-153). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 1988. / Typescript (photocopy). Includes bibliographical references (leaves 93-97). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 96-108). Also available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 1992. / Typescript (photocopy). Includes bibliographical references (leaves 171-186). Also available online.

Thesis (PHD)--University of Montana, 2009. / Contents viewed on April 30, 2010. Title from author supplied metadata. Includes bibliographical references.

Thesis (M.S.)--Montana State University--Bozeman, 2007. / Typescript. Chairperson, Graduate Committee: Bryan L. McGlynn. Includes bibliographical references.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 104-109). Also available on the World Wide Web.

Buffer strips alongside watercourses are now a widely accepted method of reducing nutrient and sediment run-off from agricultural land thereby improving water quality and meeting policy goals. However, this change in land use may have consequences for riparian biodiversity which have yet to be fully understood. This study investigated the impact of buffering on various aspects of biodiversity by comparing three types of margins in three river catchments in north east Scotland. Margins were categorised as unbuffered (open and unfenced), buffered (fenced-off vegetated) and wooded (long established woody vegetation - fenced and unfenced). Components of biodiversity studied included vegetation patterns, and the abundance, diversity, movement and assemblage composition of ground-dwelling arthropods focussing primarily, though not exclusively, on ground beetles (Coleoptera, Carabidae). This study further considered management options which may improve or enhance biodiversity. Evidenced changes in vegetation were associated with soil parameters (including decreasing pH), channel morphology, decreasing light availability and tree canopy cover, and bryophyte abundance along a successional gradient from unbuffered-buffered-wooded sites. Buffered and wooded sites showed lower activity density and species richness of ground beetles, but while one measure of functional diversity was high for wooded sites, buffered sites were found to have significantly lower values. Both species and trait assemblage structure of ground beetles were influenced by soil and vegetation, but also by features of buffer strip design such as width, length and age. Active management of sites through grazing or cutting increased ground beetle abundance, particularly hygrophilous species, but did not affect diversity. Radiotracking showed increased movement of ground beetles was correlated with intensity of grazing. Few truly riparian plant or arthropod species were identified indicating the process of buffering essentially 'terrestrialises' the riparian margins. The presence of a tree canopy layer appears to be the key instigator of change in soil conditions with vegetation and arthropods responding accordingly. Therefore planting and maintaining trees in buffer strips could be crucial to ensuring that functional diversity and associated ecosystem services are maintained. Active management through grazing or cutting could help in this regard. The results from this study suggest that rather than buffering all riparian margins within catchments, it is fundamentally important for biodiversity to maintain a mosaic of different successional stages and a diversity of habitats.