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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
791

The Role of Deer Browsing on Plant Community Development and Ecosystem Functioning during Tallgrass Prairie Restoration

Harris, Patrick Thomas 01 August 2014 (has links)
Tallgrass prairie in North America has been highly reduced and degraded by human activity (e.g. agriculture) and now human facilitated restoration is necessary to preserve and reestablish the biodiversity, structure and function of this system. In historical tallgrass prairie large ungulates (e.g. Bison bison) were keystone species that regulated many ecosystem properties and functions. Today, restored prairie often lacks these historical ungulates and white-tailed deer (Odocoileus virginianus) have largely assumed the role of dominant ungulates in small, tallgrass prairie restorations. Little is known about how white-tailed deer affect the development of plant communities and ecosystem function during the onset of prairie restoration. In June 2012 an agricultural field was restored to native prairie species in Konza Prairie Biological Station (KPBS) near Manhattan, KS. Immediately following seeding, experimental plots were established and fences were constructed in half of the plots to excluded white-tailed deer. From 2012 to 2013 deer browse of forbs, aboveground biomass (total, sown forbs, sown grasses, volunteer forbs and volunteer grasses), light availability at the soil surface, soil nutrients, and plant community composition were measure inside and outside of exclosures. The first year of this study occurred during a severe drought which diminished in year two, presenting the opportunity to examine the interaction of climate and deer browse on restoration. In plots where deer had access, the percentage of forbs browsed ranged from 1.3 to 10.5%. The effect of deer browsing on aboveground biomass varied across years for each category of biomass. Total biomass appeared to be regulated more strongly by deer than climate, as unbrowsed plots produced similar biomass in each year despite major climatic variation, while browsed plots did not follow this trend. Across all sampling periods, deer browsing increased light availability by 20%. In year two inorganic N was 19% lower in browsed plots, though potential net N mineralization did not vary between treatments. Plant communities were significantly different between years and, between browsed and unbrowsed plots as time and browsing affected community composition, diversity and richness. Deer browsing increased diversity and richness by 24% and 22% respectively. Community composition was most greatly affected by browsing in year one corresponding to the highest rates of browsing and greatest differences in aboveground biomass. These results indicate that deer can have substantial effects on the initial establishment of prairie communities as well as resource availability from the onset of restoration.
792

Variation in Benefit from Arbuscular Mycorrhizal Fungal Colonization within Cultivars and Non-cultivars of Andropogon gerardii and Sorgastrum nutans

Campbell, Ryan E. 01 January 2009 (has links)
Wide-scale conversion of tallgrass prairie to row-crop agriculture has spurred restoration of this endangered ecosystem. At the onset of restoration, a matrix of native plant species is sown into former crop field and includes warm-season (C4) grasses, cool-season (C3) grasses, legumes, and a large variety of herbaceous forbs. Increased demand for native seed due to a greater number of areas targeted for restoration has increased use of C4 grass cultivars by restoration practitioners. Cultivars are selectively bred to display traits such as increased productivity and digestibility, thus highlighting their original use in rangelands of the Great Plains. C4 grasses have a mutualistic relationship with arbuscular mycorrhizal fungi (AMF). In remnant tallgrass prairie, AMF can increase C4 plant uptake of belowground resources (e.g., water, soil P) by increasing root surface area. It is unknown if AMF colonization varies between seed source (cultivar or non-cultivar) of C4 grasses used in restoration and if this further affects plant biomass. Intraspecific variation in AMF colonization between two dominant warm-season prairie grasses was tested in two established prairie restoration experiments, both having plots seeded with either C4 cultivars or non-cultivars. To test for effects of seed source and AMF colonization on plant biomass, a greenhouse experiment was designed using two source populations (cultivar and non-cultivar) of two species (Andropogon gerardii Vitman and Sorghastrum nutans (L.) Nash) and soil collected at each field restoration (Kansas and Illinois). To suppress activity and colonization of AMF, a fungicide (Allban Flo: Thiophanate Methyl) was applied to half of the containers. Warm-season (C4) grass cultivars had greater or equivalent biomass production than non-cultivars at the onset of field restoration and also in the greenhouse. Furthermore, cultivars generally had less or equivalent root colonization by AMF and dependence on fungicide-free soil was greater in cultivars to retain increased accrual of biomass. It was, however, not possible to determine the role of AMF in plant biomass production as fungicide did not successfully reduce AMF root colonization in cultivars or non-cultivars, with one exception. It is critical that an effective AMF-suppression treatment be established in these types of studies. Future experiments should validate supposed effectiveness of the newly-recommended fungicide (Topsin-M) in population sources of warm-season prairie grasses and also apply it to the soil at time of planting in greenhouse studies. In the field sites, adjacent soil cultivation may have contributed to greater AMF biomass more so than surrounding remnant prairie. Future research identifying species composition of AMF at these sites is necessary to clarify differences in biomass. Despite greater plant biomass in cultivars, soil nutrient availability remained equivalent between source populations in general. Available N and P were not less in soils grown with cultivars, however soil inorganic N was inversely related to root length colonized by AMF, suggesting a role of AMF in N transfer from soil to plant. Soil P was not different between source populations likely due to legacy effects of agricultural fertilization, thus limiting a well known benefit of AMF symbiosis, at least at the onset of restoration. Non-target effects of fungicide application were observed (e.g., changes in available N) and effectiveness of AMF suppression was questionable. Fungicide lowered pH and increased N availability in soil as indicated by main effects of application and a positive relationship between pH and inorganic N across species. Fungicide application either 1) decreased N uptake by soil microorganisms (possibly including AMF) or 2) increased competition for adsorption sites and/or solubility of total inorganic N as pH changed, thus making this nutrient more available in the soil solution. Future examination quantifying indirect effects of fungicide application on soil chemistry should also be considered to better elucidate role of AMF in plant growth and soil nutrient availability between cultivars and non-cultivars of warm-season grasses used in tallgrass prairie restoration.
793

Drivers of Compositional Trajectories in Reference and Restored Pine Savanna Communities

Harshbarger, Diane 01 May 2014 (has links)
Wet pine savannas are among the most diverse ecosystems in North America and provide critical habitat for many species but have seen a dramatic decline in size over the past century due to urbanization, logging, and fire suppression. Coastal pine savannas are also vulnerable to anticipated effects of global climate change. Models of climate change predict rapid sea-level rise along the northern Gulf of Mexico and more intense hurricanes. Restoration of these fragile wetland ecosystems is needed, but the effects of climate change on restored, as well as remnant communities, are unknown. This research aimed to compare resiliency of remnant and restored plant communities to simulated hurricane disturbance. I hypothesized that species composition within both site types will be altered following experimental storm surge, and restored plots will follow a different compositional trajectory due to site conditions including invasion by non-target species and disturbed soils. I compared community composition and soil properties between remnant and restored sites experiencing experimental storm surge. Non-metric multidimensional scaling (NMDS) ordinations and a cluster analysis was used to visualize dissimilarities in composition and permutational analysis of similarity (PERMANOVA) was used to compare composition among treatment, site, and time. Repeated measure analysis of variance (ANOVA) was used to compare soil water conductivity and available ammonium over the course of the study. Results from compositional surveys suggested no significant effect of treatment on community composition, but there were significant vectors for soil moisture and ammonium resulting in different compositional trends and an apparent degree of divergence over time between the two site types. Soil characteristics (texture and bulk density) and pressure from neighboring plants within the restored site are also likely contributing to differences between the two site types. As climate change continues to alter disturbance regimes that shape coastal ecosystems, it will be necessary to assess structure and function of remnant and potentially novel plant communities and their capacity for adaptation.
794

A Novel Image Retrieval Strategy Based on VPD and Depth with Pre-Processing

Wang, Tianyang 01 August 2015 (has links)
This dissertation proposes a comprehensive working flow for image retrieval. It contains four components: denoising, restoration, color features extraction, and depth feature extraction. We propose a visual perceptual descriptor (VPD) to extract color features from an image. Gradient direction is calculated at each pixel, and the VPD is moved over the entire image to locate regions with similar gradient direction. Color features are extracted only at these pixels. Experiments demonstrate that VPD is an effective and reliable descriptor in image retrieval. We propose a novel depth feature for image retrieval. Regarding any 2D image as the convolution of a corresponding sharp image and a Gaussian kernel with unknown blur amount. Sparse depth map is computed as the absolute difference of the original image and its sharp version. Depth feature is extracted as the nuclear norm of the sparse depth map. Experiments validate the effectiveness of this approach on depth recovery and image retrieval. We present a model for image denoising. A gradient item is incorporated, and can be merged into the original model based on geometric measure theory. Experiments illustrate this model is effective for image denoising, and it can improve the retrieval performance by denoising a query image. A model is proposed for image restoration. It is an extension of the traditional singular value thresholding (SVT) algorithm, addressing the issue that SVT cannot recover a matrix with missing rows or columns. Proposed is a way to fill such rows and columns, and then apply SVT to restore the damaged image. The pre-filled entries are recomputed by averaging its neighboring pixels. Experiments demonstrate the effectiveness of this model on image restoration, and it can improve the retrieval performance by restoring a damaged query image. Finally, the capability of this working flow is tested. Experiments demonstrate its effectiveness in image retrieval.
795

AUTOMATIC RECONFIGURATION OF RADIAL DISTRIBUTION NETWORK FOR RELIABILITY ASSESSMENT USING THE CIRCUIT GRAPH

Isapour Chehardeh, Maziar 01 August 2018 (has links)
The problem of optimum restoration after occurrence the outages in a distribution network is an important issue in smart grids. In this kind of networks remote-controlled switches, alternative sources and grid-connected distributed generators (DG) are employed. Therefore, the reliability of the system (corresponding to the frequency of failures and the duration of interruptions) is improved by operating the switches to resupply a part of interrupted system during the repair time. To evaluate the reliability indices in smart grids, neglecting the restoration during the repair time causes the wrong assessment of the network. Thus, considering the rerouting the power during the interruptions seems necessary to calculate the reliability indices. The problem of restoration is formulated as a non-linear integer programming problem with the assistance of the network graph. The circuit graph method is also used to pre-evaluate the feasible interchanging operations to enhance the efficiency of the computations. The topological and operational constraints in this formulation can be found and resolved with the assistance of fundamental cut-set matrix. The optimum restoration schemes is obtained by considering the optimal islanded mode of operation of the DGs which implies maximizing the loading of DGs while not violating their generation capacities. The optimum restoration policies lead us to find the optimum number and location of those manual switches that should be upgraded to the remote-controlled switches. This is a multi-objective problem that contains the contribution of each restoration policy in the reliability improvement and the cost of those switching operations. The proposed algorithm is applied to different standard test systems and the results are compared to the results obtained from other methods and algorithms.
796

Managing Change: Integrating Cultural Landscape Values and Industrial Heritage Preservation / Integrating Cultural Landscape Values and Industrial Heritage Preservation

Cimino, Stephanie Laura 06 1900 (has links)
xv, 155 p. : ill. (some col.), maps. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / This thesis provides new ways to understand preservation theory and management objectives for industrial heritage sites by analyzing existing mechanisms for their preservation through values and practices associated with cultural landscape preservation. In addition to discussing the theory and development of existing preservation approaches to cultural landscapes and industrial heritage sites, the study identifies characteristics and values aimed at expanding the framework of historic industrial landscape preservation practice. Using case studies of western hard-rock mining landscapes as the primary examples, the study argues that management strategies based on traditional preservation practices are insufficient for interpreting the complexity of these historic places, and that historic industrial landscape preservation is best served by attending to the range of values and processes associated with the historic landscape and its protection. / Committee in Charge: Robert Z. Melnick, Chair; Mark Davison
797

Larval Supply, Settlement, and Post-Settlement Performance as Determinants of the Spatial Distribution of Olympia Oysters (Ostrea lurida) in Coos Bay, OR

Rimler, Rose 17 June 2014 (has links)
The Olympia oyster, Ostrea lurida. was overharvested in the early 20th century and is now the focus of restoration efforts in estuaries along the west coast of North America. These efforts would be aided by a better understanding of larval abundance patterns, settlement behavior, and post-settlement performance of oysters in estuaries throughout its range. In Coos Bay, Oregon, all three of these components of the oyster life cycle were investigated at multiple sites. Like adult oysters, larvae were restricted to the upper portion of the bay, although larvae were supplied to sites in the upper bay where settlement was low. Settlement and post-settlement growth was highest at sites of high adult density. These results indicate that in O. lurida, as in many other marine invertebrates, the adult population is subject to bottlenecks at the larval and juvenile stage that can vary spatially. This thesis contains previously unpublished co-authored material. / 2014-12-16
798

The Nicosia Master Plan: Historic Preservation as Urban Regeneration

Ewers, Caitlyn 06 September 2018 (has links)
Bifurcated by a demilitarized United Nations Buffer Zone since 1974, Nicosia is the only divided capital city in Europe. In 1979, its dual municipalities devised a radical, bicommunal Master Plan to mitigate some of the buffer zone’s divisionary effects and to revitalize the city center. This thesis examines the role of historic preservation within the Nicosia Master Plan, investigating the development of the plan’s preservation element and evaluating how the rehabilitation and adaptive reuse of historic buildings on either side of the barrier have promoted peaceful interaction and spurred economic growth and resettlement in the central city. Population growth, the booming heritage tourism industry, and the proliferation of bicommunal cultural events all indicate the successful implementation of these strategies. Of interest to preservationists, planners, and policymakers faced with divisive and nontraditional planning challenges, this is a timely topic that reveals the potential for preservation strategies to effect lasting urban revitalization.
799

Effect of drainage and restoration on the ecology of peatlands in the Šumava Mountains / Effect of drainage and restoration on the ecology of peatlands in the Šumava Mountains

URBANOVÁ, Zuzana January 2012 (has links)
The effect of drainage and restoration on the ecology of different types of peatlands in the Šumava Mountains was investigated. The study was focused primarily on peat properties, vegetation dynamics, carbon gas fluxes and their linkages under the affected hydrological regimes.
800

Effect of spruce swamp forest drainage and restoration on soil organic matter quality

MASTNÝ, Jiří January 2013 (has links)
The aim of the study was to determine the effect of spruce swamp forest drainage and water regime restoration on soil organic matter (SOM) quality. Six localities of spruce swamp forests in Šumava Mountains were studied (2 drained, 2 restored and 2 pristine). SOM quality was affected by long-term drainage. Spruce swamp forest restoration (3-7 years) did not have significant effect on SOM quality although other parameters (pH, bulk density, water level, plant coverage) changed.

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