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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.
51

Knowledges, fuelwood and environmental management in Kisumu district, Kenya

Mahiri, Ishmail O. January 1998 (has links)
Fundamental issues of natural resource management revolve around diverse worldviews, knowledges and practices, which cannot all be captured within the policy framework. The Western worldview, which reflects mainly the utilitarian, economistic view of resources, has influenced and shaped the trend management of natural resources has taken world-wide. The Western worldview contrasts with local knowledges, which are uniquely innovative, highly dynamic, tacit, contextual and/or locality-specific. This thesis explores the fuelwood problem in Nyando Division of Kisumu District in Kenya, seeking both a holistic understanding and an emphasis on the interface between official policy and local rural practice, including the varying knowledges. The study focused on two case study clans, Muga and Kadhier in Awasi and Kochogo Locations, respectively. Most fuelwood in the study areas is from on-farm and multiple accessible sources. This contradicts the 'fuelwood orthodoxy' school which associates fuelwood consumption with deforestation and 'woodfuel crisis'. Aerospace imageries clearly illustrated a change and decline in stand density of the woody vegetation cover in Nyando Division over time. Differences in fuelwood availability and inequalities in endowment of wood/tree resources in and between the study localities exemplify critical questions of entitlement in the face of 'abundance'. Tree planting was not seen to be synonymous with fuelwood availability. This scenario promotes the fuelwood trade, high dependence on fuelwood purchase and supplements of crop residues by local households. Land privatisation has exacerbated the situation. Distances travelled to collect fuelwood have decreased as people turn to alternative and purchased fuels. Opportunities in the study area for the resolution of the fuelwood problem include promotion of less culturally restricted and less economically valuable trees, and a more farmer-sensitive approach from government and NGOs which recognises farmers as active partners in the interface between policy and rural practice.
52

Comparing attitudes and perceptions of forest certification among foresters, loggers, and landowners in Mississippi

Auel, John Benkert 23 September 2016 (has links)
<p> Forest certification plays an important role in the forest products industry in Mississippi. Approximately 17% of the state&rsquo;s 19 million acres of forest land is certified under one of three major systems in the United States. More than two million acres are certified under Sustainable Forestry Initiative, more than one million acres are certified under American Tree Farm System and over 150,000 acres are certified under Forest Stewardship Council. </p><p> The goal of forest certification is sustainable use of all forest resources, from timber to clean water to recreation. This goal can only be achieved if nonindustrial private forest landowners, loggers, and forestry professionals all agree on the concepts each system espouses. </p><p> This project surveyed nonindustrial private landowners in Mississippi, members of the Mississippi Loggers Association, and members of the Mississippi Sustainable Forestry Initiative Implementation Committee, to test their levels of agreement on 12 different Likert Scales or sets of statements representing specific underlying concepts of forest certification. </p><p> The three groups generally agreed on most aspects of forest certification. There were some significant differences between the groups based on the distribution of responses, however the scale averages never differed by more than 0.7 indicating that while the differences were significant, overall they were still fairly close in their understanding of certification concepts. </p><p> There were a large number of non-industrial private landowners who were not aware of forest certification. This result has not changed since the last landowner study that was conducted in Mississippi regarding forest certification, almost 10 years ago.</p>
53

Aquaculture Production of the Zooplankton Species Americamysis bahia| Comparing On-Site Production at the Waikiki Aquarium to Importation

Lentes, Gwendolen A. 08 March 2019 (has links)
<p> An aquaculture production system was constructed at the Waik&imacr;k&imacr; Aquarium in the fall of 2016 that produces mysid shrimp zooplankton (<i> Americamysis bahia</i>). From November 2017 to February 2018, the Waik?k? Aquarium (WAq) required an average of 5,751 live mysids per week that were imported as feed with current import rates of $0.08 per animal or$24,000 annually. Fixed and variable budgets were used to evaluate the economics for the mysid culture system. Sensitivity analyses of labor costs, the sale of excess mysid production, and the discount rate were also conducted using stochastic modeling of in-house domestic yields to estimate the expected the net present values (NPV) of domestic production in comparison with imports. The indirect benefits of domestic production were qualitatively evaluated. Results showed that WAq had a greater (> 0) NPV across a variety of cost and benefit scenarios and a less expensive $.05 mysid versus the imported $.08 mysid.</p><p>
54

Estimating the Water Budget of Extratropical Cyclones with the Precipitation Efficiency

Cooley, Amanda 08 March 2019 (has links)
<p> Estimating the water budget of three mid-latitude extratropical cyclones is attempted from the perspective of the precipitation efficiency (PE), using a method proposed for the study of convective columns. Using a lagrangian, system-relative volume centered on the surface low pressure, each cyclone was followed for most of its lifetime within a pre-defined volume (7 degrees latitude x 9 degrees longitude, or approximately 700 x 700 km). A comparison is then made of total atmospheric water vapor ingested to total moisture eliminated (as precipitation). We hypothesize that the PE increases with the intensity of the cyclone. This small sample confirms that idea, and thus encourages further study with this approach.</p><p>
55

Relative Densities, Population Characteristics, and Sampling Efficiency of Bighead and Silver Carp in Reservoirs of the Tennessee River and Cumberland River

Fernholz, Savannah 30 January 2019 (has links)
<p> Bighead Carp <i>Hypophthalmichthys nobilis</i> and Silver Carp <i> H. molitrix</i> (collectively referred to as bigheaded carp) were introduced to the United States in the 1970s and escaped into the Mississippi River from aquaculture ponds. Since their escape, bigheaded carp have become established in the Mississippi River Basin, including the Ohio River and its tributaries. More recently, bigheaded carp have invaded the Tennessee and Cumberland rivers. Little research has been conducted on bigheaded carp in Tennessee waters, with preliminary studies investigating the distribution and characteristics of established bigheaded carp populations, including growth rates and recruitment. My study represents the first systematic sampling of bigheaded carp in the Tennessee and Cumberland rivers, both tributaries to the Ohio River, and in large reservoirs in the southeast U. S. Standardized, multi-gear sampling methods were used to sample bigheaded carp in Kentucky Lake and Pickwick Lake on the Tennessee River and Lake Barkley and Cheatham Lake on the Cumberland River in 2017 and 2018. Overnight gill nets were the most effective gear, capturing an average of 17 Silver Carp per gill net gang. Short-set gill nets captured an average of one Silver Carp per gill net gang, and electrofishing captured an average of one Silver Carp per 10-minute electrofishing transect. Maximum total length (TL) was 1,390 mm for Bighead Carp and 1,111 mm for Silver Carp, and the maximum age for both species was 11 years. Average age and condition of Silver Carp was higher in upstream impoundments than downstream, and thus suggested an early invasion period from Ohio River movements. Gonadosomatic index (GSI; egg mass weight to body weight ratio) was also higher in upstream impoundments than downstream impoundments. Higher GSI values were observed in the spring and summer, when bigheaded carp may begin to spawn in response to high flows. Length-at-age estimates for the four reservoirs suggested bigheaded carp growth rates in the Tennessee and Cumberland rivers are similar to other populations in the US, indicating populations may be experiencing density effects in southeastern impoundments. No young of year (YOY) bigheaded carp were captured during the study, but weak and missing year classes due to erratic recruitment patterns are common in bigheaded carp, and monitoring for YOY fish should continue. Mean catch-per-unit-effort (CPUE) was not significantly different among reservoirs for the three gear types, and no significant seasonal variation in mean CPUE was observed for overnight gill nets. A lack of differences in CPUE across sampling seasons suggested population densities could be assessed as agencies could fit into their schedules. Overall, the results represent the first large-scale standardized sampling effort for bigheaded carp across four southeastern states and provide integral population information for natural resource managers. Future monitoring efforts should continue to track characteristics of bigheaded carp populations in the Tennessee and Cumberland rivers and determine effective control and management strategies for populations in large impoundments. </p><p>
56

The long term dynamics of coyote brush invasion in a type-converted landscape of Southern California

Brennan, Sean G. 16 September 2015 (has links)
<p> Coyote brush (<i>Baccharis pilularis</i>) is a native shrub common to the coastal sage scrub (CSS) habitat of California and often appears in a complex mosaic with other vegetation types including grasslands. Both CSS and California grasslands are threatened habitats, where restorations of type-converted landscapes are often burdened by the persistent dominance of non-native annual grasses. However, coyote brush has been documented periodically invading grasslands, resulting in a change of state from grassland to shrubland. This study investigates the long-term dynamics of coyote brush invasion in a type-converted landscape of Southern California. Stands of expanding coyote brush were transected to identify species composition along a spatial and temporal continuum. Results show that following initial invasion, non-native species are replaced by not only coyote brush, but also several other noteworthy native species. This study shows that in Southern California, coyote brush invasion of type-converted landscapes leads to increased native diversity that includes native grasses.</p>
57

The 30-year outcome of assisted regeneration treatments in a burned and salvaged interior Alaska boreal forest

Allaby, Andrew 05 November 2015 (has links)
<p> Wildfire and subsequent timber salvage harvests are forecasted to increase in the Alaska boreal forest, creating the need to evaluate the effectiveness of forest regeneration practices in light of these interacting disturbances. Silvicultural practices such as site preparation and assisted regeneration are carried out shortly after disturbance in order to ensure satisfactory reforestation. Thirty years after a stand-replacing wildfire and salvage, we sampled an operational-scale (26.7 ha) white spruce (<i>Picea glauca </i> Moench [Voss]) regeneration trial established in a productive upland forest. Regeneration treatments were applied in a split-split plot experimental design on two landform types (LF), four ground scarification treatments (GST) plus a non-scarified control, and five artificial white spruce regeneration treatments (WSRT) plus a natural seedfall control. We analyzed total biomass as well as stand density and basal area for all species, seeking to evaluate the persistence of regeneration silvicultural treatment effects 28 growing seasons after installation. Our results indicate GST had no significant effect on white spruce basal area or stem density. </p><p> However, compared to natural seedfall control plots, white spruce basal area was six times higher in planted seedling plots, and white spruce stem density (dbh &ge; 1.0 cm) was nearly three times greater in broadcast seeding plots. White spruce stem density from natural seedfall averaged 944 stems ha<sup>-1</sup>, but density was dependent on both topographic position and distance to wind-dispersed seed sources. Scarification nearly doubled Alaska birch (<i>Betula neoalaskana</i> Sarg.) stem density and basal area compared to non-scarified control plots. Planted white spruce plots supported 19% less birch basal area, except in the most intensive scarification treatments in which birch basal area did not differ. Although quaking aspen (<i>Populus tremuloides</i> Michx.) density and basal area were generally unaffected by the regeneration silvicultural practices in this study, intensive scarification reduced basal area by half on slope plots. These results confirm that regeneration silvicultural practices continue to influence stand development beyond the stem initiation stage, but practices that promote one species may reduce others.</p>
58

Effects of the seed bank and interseeding in reconstructed tallgrass prairies

Rossiter, Stephen Cary 11 March 2014 (has links)
<p> Disturbances such as fire and mowing temporarily increase available resources for plants, opening a window of opportunity for establishment. During the recovery of vegetation after disturbance in remnant prairies, seedling establishment is often negligible compared to vegetative regrowth. It is unclear if this is the case in reconstructions. I tested the contribution of seedlings to diversity after disturbance in two, 25-year-old, low diversity reconstructed prairies by removing seedlings, allowing seedlings, and adding seed in 1 m<sup> 2</sup> plots. Disturbance frequency effects were tested by clipping each treatment zero, one, or multiple times. After two growing seasons, in the wetter field site, seedlings removed plots had the lowest species richness and highest evenness, plots with seedlings from the seed bank were intermediate, and plots with added seed had the highest richness and lowest evenness. In the drier site, only adding seed impacted richness (higher) and evenness (lower). In both sites, the seeds present in the seed bank were over 80% from non-native species. Seedling establishment was quantified along with light, water, and nitrate availability within each seeded plot. In the wetter site, resource levels did not predict seedling numbers, but seedlings were more numerous in more frequently clipped, lighter plots. In the drier site, seedlings were more numerous in less frequently clipped plots which received less light and may have remained moister. Seedling establishment from any source never affected community diversity suggesting that while some seeds establish, reconstructions are primarily maintained by vegetative reproduction. The inconsistent effect of clipping highlights the need for management to adapt to varying precipitation, however, given the non-native dominated seed banks, any management intended to increase seedling establishment could result in increased non-native cover. </p>
59

Assessing structural and functional recovery in a restored southern California salt marsh| fish community composition and the diet of juvenile California halibut

Fox, Erika Jade 09 August 2013 (has links)
<p> To evaluate the success of reestablishing tidal connection to salt marshes as a method of creating new fish habitat, both newly-restored and previously-restored (hereafter termed "reference") habitats within the Huntington Beach Wetlands Complex were monitored over a two year period. Although fish abundance and diversity metrics were generally equivalent between marshes within one year, community composition remained different. Newly-restored habitat generally had higher abundances of planktivores (e.g., <i>Atherinops affinis</i>), and lower abundances of benthic carnivores (e.g., <i>Fundulus parvipinnis </i>) relative to reference habitat. To determine the possible mechanisms driving fish habitat use patterns, trophic support was assessed for juvenile California halibut, <i>Paralichthys californicus,</i> using gut content and stable isotope analyses of wild-caught and caged individuals. Observed differences in the diet of halibut across size classes indicated ontogenetic shifts in feeding behaviors, while similarity in diet among marshes suggested the potential for rapid development of trophic support within restored habitats for this species. </p>
60

Restoring Ecological Function by Mimicking Natural Process

Katz, Jacob Van Epen 09 July 2015 (has links)
<p> <b>Chapter 1:</b> <i>Impending extinction of salmon, steelhead, and trout (Salmonidae) in California. </i> California contains the southernmost native populations of most Pacific Coast salmon and trout, many of which appear to be rapidly headed toward extinction. A quantitative protocol was developed to determine conservation status of all salmonids native to the state. Results indicate that if present trends continue, 25 (78%) of the 32 taxa native to California will likely be extinct or extirpated within the next century, following the bull trout (Salvelinus confluentus), which was extirpated in the 1970s. California's salmonids are adapted to living in a topographically diverse region with a Mediterranean climate, characterized by extreme seasonal and inter-annual variability in streamflow. Consequently, California salmonids have evolved extraordinary life history diversity to persist in the face of stressful conditions that often approach physiological limits. The spatial distributions of California salmonids vary from wide-ranging anadromous forms to endemic inland forms persisting in only a few kilometers of stream. Eighty-one percent of anadromous taxa are threatened with extinction and 73% inland taxa are either threatened or already extinct. Although specific drivers of decline differ across species, major causes of decline are related to increasing competition with humans for water, human degradation of watersheds, and adverse effects of hatchery propagation. Climate change, interacting with the other causes of decline, is increasing the trajectory towards extinction for most populations. Bringing all of California's salmonid fishes back from the brink of extinction may not be possible. If there are bold changes to management policy, however, self-sustaining populations of many species may be possible due to their inherent ability to adapt to changing conditions. </p><p> <b>Chapter 2:</b> <i>Floodplain Farm Fields Provide Novel Rearing Habitat for Chinook Salmon.</i> When inundated by floodwaters, river floodplains provide rich food resources and high quality habitat for many species of wildlife. Globally, many rivers have been leveed and floodplain wetlands drained, primarily for flood control and conversion to agriculture. In the Central Valley of California, USA, where less than 5% of floodplain wetland habitats remain, a critical conservation question is how farmlands located on floodplains can be managed to provide increased habitat benefit to fish and wildlife. In this study agricultural fields located on the Sacramento River floodplain were intentionally inundated after the autumn rice harvest to mimic natural floodplain inundation patterns and determine if they could provide shallow-water rearing habitat for imperiled Sacramento River fall-run Chinook salmon (<i>Oncorhynchus tshawytscha</i>). Approximately 10,000 juvenile fish were reared on two hectares for six weeks when fields were idle between fall harvest and spring planting. Growth rates of juvenile salmon (average 0.76 mm/day) reared in this surrogate floodplain habitat were among the most rapid ever documented in fresh water in California and survival was high (minimum estimated survival 57%). The apparent compatibility of crop production and fish and wildlife habitat on the same ground demonstrates the ecological and economic benefits of reconciling management of agricultural working landscapes with recovery of native species. </p><p> <b>Chapter 3:</b> <i>Managed Inundation of Agricultural Floodplains Produces Record Growth in Juvenile Chinook Salmon.</i> Floodplains are important engines of seasonal productivity in river ecosystems. However, in North America and Europe over 90% of floodplains habitats are no longer hydrologically connected to rivers, representing a significant loss of riverine ecosystem food web productivity. Expanding inundated floodplain area increases the volume of the photic zone, the uppermost portion of the water column, where sunlight is converted to carbohydrates by phytoplankton. Greater extent of shallow floodplain augments overall food availability and provides important aquatic habitats for many species. For example, invertebrates are in greater abundance on floodplains than in adjacent river channels, enhancing foraging success of fish that gain access to these seasonally inundated aquatic habitats. Like many large river valleys globally, the Central Valley of California, USA, (encompassing the Sacramento and San Joaquin River watersheds) has lost the majority of its floodplain habitat, primarily to conversion to agriculture. However, remnant floodplains still exist and are managed as flood bypasses which function in the winter wet season as "pressure relief valves," allowing floodwaters to pass safely around vital infrastructure and urban areas. In the summer dry season, bypasses are actively farmed. Managed inundation of agricultural floodplains may offer a means of regaining some of the ecological benefits of floodplains for native fish and wildlife while continuing to support flood protection and production agriculture, thereby creating a landscape where native species and human uses can coexist. An example of such reconciliation is Yolo Bypass, a farmed floodway where two decades of managed winter inundation of post-harvest rice fields&mdash;in the agricultural off-season when farm fields are idle&mdash;creates wetland habitat for millions of waterfowl using the critically important Pacific Flyway. Recent studies have shown that managed inundation can also provide suitable floodplain foraging habitat for native fish species such as juvenile Chinook Salmon. </p><p> In order to better understand how rice farming practices affect the quality of reconciled winter rearing habitat for juvenile fall run Chinook Salmon (Oncorhynchus tshawytscha), we built and experimentally manipulated nine replicated two-acre rice fields. Fields shared a common layout and water source. Each was randomly assigned to one of three post-harvest farming options generally used in the Yolo Bypass; fallow, leaving standing rice stubble, or tilling to incorporate the stubble into the soil. Each field was stocked with approximately 4,500 juvenile salmon. Weekly sampling for water quality, invertebrate abundance and diversity, and fish growth and survival was conducted for 6 weeks, after which fields were drained and fish counted, measured</p>

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