• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 458
  • 177
  • 132
  • 57
  • 43
  • 17
  • 15
  • 7
  • 7
  • 7
  • 7
  • 7
  • 7
  • 6
  • 5
  • Tagged with
  • 1228
  • 254
  • 242
  • 202
  • 165
  • 134
  • 129
  • 129
  • 108
  • 105
  • 102
  • 94
  • 93
  • 93
  • 83
  • 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.
321

Drought, Depression, and Relief: The Agricultural Adjustment Wheat Reduction Program in North Dakota during the Great Depression

Gostanzik, Brent Alan January 2012 (has links)
The purpose of this thesis is to examine how the Agricultural Adjustment Wheat Reduction Program functioned in North Dakota from May of 1933 to January of 1936, why it ran so smoothly, and why it was such a success within the state. By using county Extension Agent reports that date from the time period this thesis uses an extensive number of primary sources that have not been used before. These reports, along with farmer journal accounts, newspaper articles, and Agricultural Adjustment Administration reports show that North Dakota wheat farmers openly embraced the policies of the Wheat Reduction Program and participated in it in higher numbers than any other state in the nation. The farmers embraced the program because the drought and economic depression they were facing left let them little choice, but also because the program did not seek to radically alter the structure of wheat farming in North Dakota.
322

Barriers to selling livestock in the face of drought in the Omusati Region of North Central Namibia

Joshi, Nivedita 24 August 2021 (has links)
Marginal communities living in semi-arid Namibia face significant challenges in sustaining rural livelihoods due to environmental degradation and poverty. Research has shown that livestock farming depends on rain-fed agriculture among other things, thus making communal farmers vulnerable to climate change in the future. Given this, it often makes sense for farmers to sell their livestock and explore alternative livelihood options. However, farmers in northcentral Namibia are reluctant to sell their livestock despite a noticeable temperature increase and rainfall decrease over the past forty years. This study analyses the barriers to selling livestock in the face of a drought in the Omusati region of north-central Namibia. The study was carried out in three villages namely Omahanene, Okathitukeengombe and Oshihau, in the north-central Omusati region of Namibia. Household livestock distribution, perceptions of climate change, barriers to the sale of livestock and alternative livelihood strategies from other semi-arid regions were explored among 30 households using semi-structured household interviews and a systematic literature review. Results from the study indicate that 80% of communal farmers predict future droughts in the region and able to recall climate change through frequent droughts, increasing temperatures and decreasing rainfall. Farmers claimed that these changes have affected their livestock numbers. However, several barriers including cultural beliefs, lack of financial security, access to information, lack of institutional support and lack of efficient markets hinder livestock sales. The study suggests that the imminent impact of climate change coupled with the reluctance to sell livestock will threaten food security in the future. The study argues that rural livelihood diversification strategies are critical to safeguarding sustainable livelihoods in the future, including those of communal livestock farmers specifically. Additionally, policy recommendations like access to credit through public and private funding, access to markets by providing transportation facilities, encouraging market participation by improving quality of grazing lands, increasing water availability, building veterinary facilities, employing extension officers and access to information through reliable channels can help build a sustainable future in the face of climate risks.
323

Odpověď antioxidačních enzymů na abiotický stres. Vliv snížené hladiny cytokininů. / Antioxidant enzymes response to abiotic stress. Impact of decreased cytokinin level.

Lubovská, Zuzana January 2015 (has links)
Charles University in Prague, Faculty of Science Department of Experimetnal Plant Biology Ph.D. study program: Plant physiology and anatomy Abstract Antioxidant enzymes response to abiotic stress. Impact of decreased cytokinin level. Zuzana Lubovská Supervisor: RNDr. Naďa Wilhelmová, CSc. Supervisor-consultant: RNDr. Helena Štorchová, CSc. Praha, 2015 The response of the antioxidant enzyme system to drought, heat and a combination of these stresses was followed in tobacco plants overexpressing cytokinin oxidase/dehydrogenase1 (CKX1) under the root-specific WRKY6 promoter (W6:CKX1 plants) and under the constitutive 35S promoter (35S:CKX1 plants) and in the corresponding wild type (WT). CKX1 over-producing lines developed a bigger root system, which contributed to their stress tolerance. The high stress tolerance of 35S:CKX1 plants was also associated with a dwarf shoot phenotype and changed leaf morphology. The genes for chloroplastic antioxidant enzymes, stroma ascorbate peroxidase (sAPX), thylakoid ascorbate peroxidase (tAPX) and chloroplastic superoxide dismutase (FeSOD), which are responsible for scavenging of reactive oxygen species produced via electron transfer during photosynthesis, were all strongly transcribed in control conditions. All the tested stresses down-regulated expression of these genes...
324

Impact of experimental soil moisture manipulation on tropical tree seedling demographic fates and functional traits

Lammerant, Roel January 2021 (has links)
In tropical regions, climate change is predicted to lead to increased drought frequency and intensity. The extent to which this will shift the functional diversity of tropical tree communities is unknown due to a limited understanding about the response of seedlings to variable soil moisture. We addressed this issue using an experimental approach in the Luquillo Experimental Forest, Puerto Rico. We exposed seedlings of eight tree species, representing different successional stages, to an experimental soil moisture gradient. We evaluated (1) How species mean trait values relate to species-specific demographic responses to drought, (2) How intraspecific variation in functional traits relates to a soil moisture gradient, (3) The extent to which demographic response to short-term experimental drought mirrored long-term demographic response of seedlings to natural variation in soil moisture. Growth and survival of species with more `conservative` functional strategies tended to be more sensitive to a change in soil moisture and more tolerant to drought compared to species with more `acquisitive` strategies. In addition, traits of individual seedlings within species varied with respect to soil moisture, suggesting a potential role for phenotypic plasticity in response to drought. Specifically, this response was significant for three species (Inga laurina, Guarea guidonia, Schefflera morototoni) and was primarily associated with relative carbon investment in leaves and roots. Species demographic responses to soil moisture in experimental and long-term studies were weakly positively correlated but more variables are at play under natural conditions, which partly decouples these responses. Overall, our results suggest that tree species with `conservative` functional strategies are likely to become more common under increasing drought frequency and intensity in the Luquillo Mountains of Puerto Rico. However, understanding the broader implications of our findings will require considering the effects of other disturbances, including hurricanes, which may have contrasting effects. Furthermore, intraspecific variation in functional traits is likely to influence how the seedlings of tropical tree species cope with drought.
325

Ecology and Recolonization of Benthic Macroinvertebrates in a Groundwater-dependent Stream in North Central Texas During a Supra-seasonal Drought

Burk, Rosemary A. 05 1900 (has links)
Extreme climatic events such as droughts are known to eliminate aquatic biota and alter community structure and function. Perennial headwater springs provide important drought refugia to benthic macroinvertebrates and an important source of colonists via drift or aerial adults to intermittent streams post-drought. During a supra-seasonal drought in North-central Texas summer and fall 2006, benthic macroinvertebrates from persistent groundwater-dependent macrohabitats of varying hydrological connectivity and riparian shading were studied: perennial riffles, connected pools, shaded disconnected pools, and full sun disconnected pools. Riffles were a distinct habitat with significantly higher taxa richness, proportion of lotic taxa, diversity and evenness than other macrohabitats. Macrohabitats were found to be important refugia for 106 benthic macroinvertebrates and 4 microcrustacean taxa. Throughout the extreme drought, perennially flowing habitats were refugia to 19 taxa (17.9% total taxa) not collected in disconnected pools. Shaded disconnected pools contained lotic taxa not previously known to be able to complete their lifecycles in lentic habitats, emphasizing the importance of groundwater effluent and shading. With the resumption of flow at a downstream intermittent site of Ash Creek in mid-October 2006, an annual recolonization study was conducted comparing the perennial headwaters’ benthic macroinvertebrate taxa richness, densities and community ecology with the downstream intermittent site. The headwaters supported higher mean taxa richness than the intermittent site over the duration of the study (ANOVA P < 0.001). However, the unexpected result of overall decreasing taxa richness at the perennial headwater site from August 2006 to April 2008 appears to reflect lag effects of the supra-seasonal drought combined with effects of multiple spates of 2007, which are factors confounding the point of recovery for taxa richness. Recovery of taxa richness at the intermittent site took 9 months compared to 1 to 2 months reported in other arid and semi-arid streams in the United States recovering from seasonal drying and floods. Sustainable use of groundwater resources and conservation of riparian corridors is vital to protecting groundwater-dependent ecosystems that play a vital role in maintaining regional biodiversity by serving as biotic refugia during catastrophic disturbance.
326

Testing the influence of riparian buffer design on stream biodiversity following drought / En undersökning av kantzoners påverkan på den biologiska mångfalden av makroevertebrater efter en period av torka

Eriksson, Rasmus January 2021 (has links)
Forestry is a major industry in Sweden and the most common method to harvest timber is to clear-cut large areas. Clear-cutting can alter multiple physical, chemical, and ecological characteristics of headwater streams. To minimize these effects, vegetated riparian ‘buffers zones’ are often spared along streams and lakes. Despite this, there are uncertainties regarding optimal width of buffers to safeguard streams from clearcutting effects. In this study, I ask how riparian buffer width influences stream macroinvertebrate communities, and how this influence may be altered by summer drought. I tested this in 24 headwater streams, half located in northern Sweden and the other half in southern Sweden. Streams in each region included four different buffer width categories (n = 3), including: “no buffer” (no trees left post-harvest), “thin buffer” (&lt; 5 m), “moderate buffer” (&gt; 5 m) and “reference” (no harvest). I analysed a suite of metrics that describe the abundance, richness, and composition of macroinvertebrates, and compared these across streams with different buffer properties. Regionally, southern streams had marginally greater taxonomic richness and relative abundance of sensitive taxa compared to northern counterparts, regardless of buffer conditions. Further, thin and absent buffers performed the best across several macroinvertebrate metrics, particularly for southern streams. Antecedent drought had no observable effects on macroinvertebrate communities, but taxonomic richness across region was positively correlated with stream pH. Overall, my findings, while tentative given low statistical power, suggest that retaining coniferous-dominated buffers may not lead to the desired ecological outcomes in boreal headwaters.
327

Exploring the contributions of cross-sector collaborations to Disaster Risk Reduction in the city of Harare: an investigation through a drought response lens

Nyamakura, Balbina Kudzai 14 March 2022 (has links)
The Sendai Framework for Disaster Risk Reduction calls for collaboration across sectors in society as an effective way to reduce disaster risk in order to safeguard lives, human wellbeing, and development gains from potential disasters. However, the effectiveness of these cross-sector collaboration approaches has most often been studied in the context of rapid onset disasters such as floods, with less focus on slow-onset disasters such as multiple year droughts. There is also limited research on the contributions of cross-sector collaborations towards Disaster Risk Reduction in African cities. For this study, I set out to investigate cross-sector collaboration efforts contributing to drought response in the city of Harare, Zimbabwe; and how these collaborations were contributing towards fulfilling the four priority areas of the Sendai Framework. These include i) understanding disaster risk, ii) strengthening disaster risk governance, iii) investing in disaster risk reduction for resilience, and iv) enhancing disaster preparedness for effective response. In this qualitative study, I made use of purposive and snowball sampling methods to select 14 key informants from national and local government, non-governmental organisations, and civil society organisations who were directly involved in eight drought related cross-sector collaborations. I conducted in depth semi-structured interviews with these key informants between 2018 and 2019. For the analysis, I followed prior developed themes based on Bryson et al. (2006) theoretical framework to understand cross-sector collaborations. I also applied a typology of barriers and enablers developed from the literature in the analysis, and interpreted emergent themes using NVivo software. I then assessed the contributions of the identified cross-sector collaborations to the activities listed under each of the four priority areas in the Sendai Framework. The findings highlighted the socio-political and economic context of the city of Harare had seeped through and influenced the cross-sector collaborations responding to drought. They shed light on how taking advantage of widely accessible social media platforms serve to enhance collaborations. Additionally, the results highlight the importance of existing networks and relationships in enabling cross-sector collaborations to occur effectively. Most of the cross-sector collaborations occurring in response to drought were originally formed for other reasons and included drought response during the peak of the drought disaster. Collaborations were effective at contributing towards engaging communities in risk assessment and reporting at the local level (Priority 1) and ensuring continual provisioning of services (water) during and after disasters (Priority 4). I make suggestions for collaborations to consider issues of power and how these affect the effectiveness of collaborations on the ground with regards to ensuring social justice and reducing inequality. Finally, I conclude that cross-sector collaborations would be more effective in response to slow-onset disasters when they are formed and applied before the disaster is at its peak. I also suggest that the design and implementation of the cross-sector collaborations be tailor made to consider the socio-political and economic aspects of the city in their design for effective response.
328

“It is what it is”: an ethnography of women's experience of drought in Madziva, Zimbabwe

Kanengoni, Mistancia 11 September 2020 (has links)
Bad weather conditions such as drought have had detrimental effects on the agrarian life of the people in Madziva rural area, Zimbabwe. Due to the unfavorable weather conditions in this area, poverty and unemployment, most men migrated and continue to migrate to the urban areas in search of greener pastures. This research focuses on how these more frequent extreme weather conditions in Madziva, resulting in less predictable seasons, have increased incidences of precarity. This is important as it portrays how the climate has changed, its effect and the anxiety and expectations around it. Furthermore, providing perception of the nature of climate change in the village is important in order to assess the evidence of nature and level of climate change (manifesting through drought). As a result of the uncertainty caused by drought, the migration of men had been rampant in Madziva, and thus the village is characterized by a significant number of female-led households. To understand the social, political and economic dynamics of what it means to survive in a time of drought for ‘fragmented' families, an ethnographic research was conducted in Madziva over two months (14 June 2017 to 15 July 2017) and (10 December 2017 to 11 January 2018) during one of the worst droughts in Zimbabwe. This research follows the everyday lives of eight women and the interactions with 15 more women through focus group interviews in order to understand the strategies used to achieve survival. In this thesis, the results of an ethnography of women's experience of drought particularly in Madziva rural area in Zimbabwe between June 2017 and mid-January to mid-February 2018 are presented. It further explores, the locals' understandings of extreme weather conditions particularly in Madziva rural area and how practices, particularly those linked to gender, are shaped or reinforced. This research found out that the people of Madziva rural area, particularly women are severely affected by drought as compared to men. This is because of the expectations of managing the household and caring for children which requires them to be heavily reliant on natural resources. The reliance on natural resources has been due to the very poor and non-performing Zimbabwean economy, however, these are the resources which become scarce in a time of drought, which exacerbates precarity. Additionally, women in rural areas such as Madziva have less access to critical information on shifts in cropping patterns and weather alerts, and this can be linked to the gendered structure of the village, where men are seen as the principle holders of knowledge of the land. Furthermore, women also have very little power in decision making and access to resources because of the land ownership titles often given to the men of the household. However, with iv the high migration to urban centers, there is a gap that the women of Madziva must navigate and this thesis aims to explore how this occurs. For instance, during the fieldwork, it became evident that irrespective of all these challenges that are caused by drought, women are always expected to make a plan to provide for their families although there is a stiff competition for the remaining natural resources. Women in Madziva negotiated relationships of marginality, responsibility, togetherness and belonging through the ways they experienced the challenges ushered by drought.
329

The Effect of "Drought Tolerant" Plant Labeling on Consumers' Preferences and Willingness to Pay for Ornamental Plants

Cenador, Susanne Tábara 01 May 2019 (has links)
Utah’s water resources are endangered by low rainfall rates, high per capita water consumption and a strong projected increase of residents. The irrigation of ornamental plant landscaping is estimated to account for 60% of residential water use, and is, therefore, a target of education programs in the effort to promote water conservancy. The water-wise “Yellow Tag” program developed by the Utah Division of Water Resources seeks to provide retail nurseries with free tags for labeling plants which are considered low water use with the objective of promoting water conservation. The objective of this study is to determine consumer preferences for plants labeled with the Yellow Tag. As a means of measuring consumer preference we use willingness-to-pay (WTP). We give participants the choice between daylily, spiderwort and neither. Choice alternatives differ in flower color, purported irrigation need, production location and price. The data for this study was collected through an online survey instrument applied to 463 participants residing in the state of Utah. Our results show that consumers prefer daylilies labeled with the Yellow Tag, and dislike spiderwort labeled with a high irrigation need. Special preference for Yellow Tag labeled ornamentals was found for respondents who are female, living in single houses, are concerned about the price of water and are drought aware. We do not find a preference for flower color or production location. These promising results may encourage Utah governmental and education agencies to continue the Water-Wise program, expand educational programs to increase drought awareness and help retailers optimize their future product mixes.
330

Multispectral remote sensing of the impacts of drought and climate variability on water resources in semi-arid regions of the Western Cape, South Africa

Bhaga, Trisha January 2021 (has links)
>Magister Scientiae - MSc / The occurrence of droughts is a threat to global water resources and natural ecosystems, with the impact being more profound in semi-arid environments. The frequency of droughts is likely to increase because of climate change, and this poses a huge threat to the available water resources, to livelihoods and to ecosystems. Routine drought monitoring is fundamental for developing an early warning system and an area-specific drought mitigation and adaptation framework. Surface waterbodies, especially those in arid and semi-arid environments, are vulnerable to the impacts of drought. The development of moderate-resolution sensors, such as the Landsat 8 Operational Land Imager (OLI) and the Sentinel-2 Multispectral Instrument (MSI), allow new opportunities to monitor droughts and their impact on surface waterbodies.

Page generated in 0.0431 seconds