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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.
371

Towards structured planning and learning at the state fisheries agency scale

Aldridge, Caleb A 09 December 2022 (has links)
Inland recreational fisheries has grown philosophically and scientifically to consider economic and sociopolitical aspects (non-biological) in addition to the biological. However, integrating biological and non-biological aspects of inland fisheries has been challenging. Thus, an opportunity exists to develop approaches and tools which operationalize planning and decision-making processes which include biological and non-biological aspects of a fishery. This dissertation expands the idea that a core set of goals and objectives is shared among and within inland fisheries agencies; that many routine operations of inland fisheries managers can be regimented or standardized; and the novel concept that current information and operations can be used to improve decision making through structured decision making and adaptive management approaches at the agency scale. In CHAPTER II, my results show that the goals of inland fisheries agencies tend to be more similar than different but have expanded and diversified since the 1970s. I suggest that changes in perspectives and communication technology, as well as provisions within nationwide funding mechanisms, have led to goals becoming more homogenous across the USA and more diverse within each bureau. In CHAPTER III, I found that standardized collection and careful curation of data has allowed one inland fisheries bureau to acquire a large fish and fisheries database and that managers use this database to summarize common fish population parameters and indices, craft objectives, and set targets. The regimentation of data management and analysis has helped managers within the inland fisheries bureau to assess fish populations and fisheries efficiently and effectively across waterbodies within their districts and state. In CHAPTER IV, I extend CHAPTERS II and III to show that biological and non-biological management objectives and their associated measurable attributes and management actions can be synthesized into a common set of decision elements. I demonstrate how common decision elements enable managers to easily structure decisions and help to address common problems at the agency scale. Using a subset of common decision elements, I demonstrate how existing agency operations (e.g., monitoring) can be used to expedite learning and improve decision making for a common problem faced by managers in multiple, similar systems.
372

Modeling Spatial Distributions of Tidal Marsh Blue Carbon using Morphometric Parameters from Lidar

Turek, Bonnie 05 April 2023 (has links) (PDF)
Tidal marshes serve as important “blue carbon” ecosystems that accrete large amounts of carbon with limited area. While much attention has been paid to the spatial variability of sedimentation within salt marshes, less work has been done to characterize spatial variability in marsh carbon density. Driven by tidal inundation, surface topography, and sediment supply, soil properties in marshes vary spatially with several parameters, including marsh platform elevation and proximity to the marsh edge and tidal creek network. We used lidar to extract these morphometric parameters from tidal marshes to map soil organic carbon (SOC) at the meter scale. Fixed volume soil samples were collected at four northeast U.S. tidal marshes with distinctive morphologies to aid in building our predictive models. Tidal creek networks were delineated from 1-m resolution topo-bathy lidar data using a semi-automated workflow in GIS. Sample distance to tidal creeks and flow distance to the marsh edge were then determined. Log-linear multivariate regression models were developed to predict soil organic content, bulk density, and carbon density as a function of these predictive metrics at each site and across sites. Results show that modeling salt marsh soil characteristics with morphometric inputs works best in marshes with simple, single creek morphologies. Distance from tidal creeks was the most significant model predictor. Addition of distance to the inlet and tidal range as regional metrics significantly improves cross-site modeling. Our process-based approach results in predicted total marsh carbon stocks comparable to previous studies but provides trade-offs to existing simplistic carbon mapping methods. Further, we provide motivation to continue rigorous mapping of soil carbon at fine spatial resolutions and to use these results to guide salt marsh restoration projects and aid in the development of carbon markets.
373

Investigation Of Temperature, Solution Strength, And Applied Stress Effects On Cation Exchange Processes In Different Geosynthetic Clay Liner Products

Fuller, Kendra 01 September 2024 (has links) (PDF)
An extensive laboratory test program was conducted to analyze and compare the cation exchange processes in three different varieties of sodium bentonite (Na-B) geosynthetic clay liners (GCLs) over increased conditioning durations up to 32 days and investigate the effects of temperature, solution strength, and applied stress. The goal of this test program was to establish whether the variables of temperature, solution strength, and applied stress improved or degraded the engineering properties of GCLs in laboratory testing and municipal solid waste (MSW) landfill applications. The GCLs were conditioned in liquids of increasing ionic strength, using deionized water and 2, 50, and 200 mM CaCl2 solutions to represent control, pore water, mild MSW leachate, and harsh MSW leachate. Conditioning periods were 1 to 32 days. Tests were conducted at 5°C, 20°C, 40°C, and 60°C and at 0 kPa, 30 kPa, and 500 kPa to represent stresses experienced by the cover and bottom liner. These variables were selected to represent geoenvironmental conditions observed in MSW landfill systems. Cation exchange processes in the bentonite component of the GCL were quantified by measuring the bound cation (BC) concentrations and cation exchange capacities (CEC) of the specimens and by conducting index testing to determine the dimensional measurements, final moisture content, and swell index of the conditioned bentonite. The temperature, electrical conductivity, total dissolved solids, sodium and calcium concentrations of the conditioning fluids were measured periodically for all specimens and the sodium concentration was measured for all specimens tested at applied stress. Temperature, solution strength, and applied vertical stress all affected the cation exchange processes in the bentonite component of GCLs. Increasing temperature, increased solution strength and decreased applied vertical stress were observed to increase cation exchange processes. The results of this study can be applied to quality assurance evaluations of in-service GCLs. In addition, the observation of the study indicates that GCLs used in cover liner systems for MSW landfills may be susceptible to high rates of cation exchange due to low overburden stresses and high surface temperatures. GCLs used in bottom liner may experience inhibited cation exchange rates as a result of high vertical stresses and relative lower temperatures.
374

Harvesting strategies of fuelwood and kraalwood users at Machibi : identifying the driving factors and feedbacks

Scheepers, Kelly January 2008 (has links)
Forest and woodland ecosystems provide a variety of natural resources such as fuelwood, brushwood and kraal posts to local communities, as well as possess important cultural and spiritual value. However, many forests and woodlands worldwide have been unsustainably used and managed. Thus, under pressure from the international conservation community to recognise the importance of people's relationships with their surrounding natural environment, particularly for the natural resources it can provide, and given a move away from the management of forests and woodlands for sustained yields, and according to simple cause and effect models, in favour of systems approaches, South Africa has developed some of the most progressive natural resource management policies in the world. Nevertheless, for these policies to be sensitive to local contexts, there remains a need for a better understanding of how local people in different contexts, determine forest and woodland ecosystems to be of use to them, and what 'usefulness' means to different groups of resources users. This is a case study, which examines the role of fuelwood, brushwood and kraal posts in the rural livelihoods of the people of Machibi village, located in the Eastern Cape province of South Africa, through people's preferences for particular landscapes and species, accessed for these purposes, and the trade-offs people make between resource availability and resource accessibility. Key objectives of the study are to 1) determine the preferred landscapes and species for fuelwood, brushwood and kraal posts at Machibi, 2) determine the landscapes and species actually used for fuelwood, brushwood and kraal posts, and 3) with the help of a conceptual model, and using iterative modelling as a tool, determine the factors that influence people's harvesting strategies in terms of the costs and benefits associated with the different landscape and species options. On the basis of this knowledge, the study provides some guiding principles for the better use and management of these landscapes and species for fuelwood, brushwood and kraal posts. An innovative research approach and methodology that integrates social and ecological systems, works across disciplines, and draws on different types of knowledge is used to develop and test a conceptual model of the harvesting strategies of fuelwood and kraalwood users at Machibi. Participatory methods such as workshops, participatory resource mapping, ranking exercises and trend-lines were used to tap into local knowledge while plotless vegetation sampling and GIS maps were used to capture the scientific information. Results showed that people did not always use the landscapes and species they preferred. However, the local people did behave in a rational manner by weighing up the returns from harvesting and accessibility costs associated with the respective options available to them, before selecting the option(s) associated with the greatest net benefits. At the landscape level, people made trade-offs between the returns from harvesting and the accessibility costs of using particular landscapes in addition to costs associated with the physical work of harvesting fuelwood, brushwood or kraal posts from these landscapes. At the species level, people made trade-offs between the returns from harvesting and the accessibility costs of harvesting particular species for fuelwood, brushwood and kraal posts, or the costs of commercial alternatives. Costbenefit factors that influenced people's resource use patterns also differed across landscapes and species for fuelwood, brushwood and kraal posts, respectively. Consequently, a range of diverse and flexible management options and strategies is recommended for the wise use and management of these landscapes and species, focused on short, medium and long term goals. These strategies examine the use of cost - benefit incentives to influence people’s landscape and species use patterns.

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