"June 2002" / Bibliography: leaves 172-198. / viii, 198 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Proposes that the overall outcome of plant interactions along a temporal gradient of resource availability changes from positive during interpulses to negative during pulses. Examines negative interactions between 4 co-dominant chenopod scrubs in arid Acacia papyrocarpa woodlands. Negative interactions were more intense when conditions were least productive. Positive interactions between seedlings also changed over time, depending on the facilitation mechanism. Plant interactions seem to be most intense at the beginning of interpulses when plants are competing for diminishing water, or survivorship is enhanced in the favorable microsites provided by other plants. Later in the interpulse, interactions become less intense as conditions become more stressful and therefore survivorship and growth are affected more by abiotic conditions than plant interactions. / Thesis (Ph.D.)--University of Adelaide, Dept. of Environmental Biology, 2002

Bibliography: leaves 155-169. / xiv, 169 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Studies the effect of nitrogen fertilizer on dry matter production under differing watering regimes. Investigates the accuracy of different crop and soil organic matter models for predicting crop yield, nitrogen uptake and changes in soil organic carbon and nitrogen. Compares the models with data from long-term field experiments on wheat in Australia and sorghum in Ethiopia. Finds that a higher crop yield and better nitrogen and water utilisation can be achieved if addition of nitrogen fertilizer is balanced with soil water. / Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy & Farming Systems, 1997?

<p>Tortoises appear to be successful in arid ecosystems, where they depend on primary production for their predominantly herbivorous diets. The low primary production of arid regions is exacerbated by priodic droughts, so that iteroparous species such as chelonians require mechanisms to overcome resource shortages. The smallest of all tortoises, Homopus signatus signatus, occurs in a dry winter rainfall area in northwestern South Africa that is threatened with aridification due to regional climate change. The overall aim of this study is to understand the ecology of H. s. signatus, particularly in reference to the importance of rainfall.</p>

Graduation date: 1992

Thesis (Ph. D.)--University of Queensland, 2001. / Includes bibliographical references.

Certified organic farming is developing rapidly world-wide and has become of interest to many farmers, politicians, environmentalists and governments and is practised now in nearly all countries of the world. However, adoption of certified organic farming is not an easy option for farmers and it carries with it several barriers such as technical, economic, social, cultural or legal. The Jordanian Government is interested in proposing organic farming to farmers, but without initially investigating whether or not organic farming will be a suitable system for farmers. Therefore, this research is based on the need to investigate the main barriers and to evaluate opportunities and potential for organic farming in Jordan’s arid lands and to propose an adoption model based on local farmer participation, using farmers’ local knowledge and their initiative, as well as institutional participation. To do so, a two-stage research methodology was employed in this research to gain the necessary data during two periods of fieldwork, April to September 2004 and July to September 2005. During this fieldwork, interviews with 46 farmers using an open questionnaire and interviews with discussion groups and government officials were conducted to investigate barriers and potential for organic farming in Jordan. Also, a national workshop was conducted attended by the Minister of Agriculture and stakeholders to evaluate and to ensure the sustainability of the proposed model. Respondents reported that the main barriers to adopting organic farming included perception, technical, nutrient availability, cultural/social, marketing, economic, institutional, lack of national regulation and lack of information and advice, but that labour was not a barrier. Findings also showed that despite barriers the area has potential for organic production owing to its extensive area, good water quality, potential farmers and international agreements. Based on the results obtained from this research, a suitable organic farming model for Jordan, and other countries having similar conditions, was developed. The model is divided into four levels: government, field, academic and regional and international, and the role of each level and its relationship with other levels is explained. The research shows that the success of this model with delivery of its objectives does not rely on the work of only the Ministry of Agriculture (MoA) or any other single body, but on everyone involved in the provision of organic farming in Jordan. Moreover, the model suggests a potential framework for an action plan on the subject of Jordan and organic farming. Also the methodology developed in this research is considered to be a great help for future researchers wanting to conduct research on organic farming or research related to sustainable agricultural development in the developing world context.

Watershed models have two significant shortcomings that limit their application to management problems in arid and semi-arid regions. The first is that the performance of event-based hydrologic models for ephemeral stream networks declines significantly as watershed size increases. The second is that no single model is capable of simulating runoff, erosion, and geomorphic response in the channel network for multiple consecutive events. A diffusion-wave routing subroutine was developed for the Kinematic Runoff and Erosion Model (K_INEROS2) using a four-point iterative solution to the modified variable-parameter Muskingum-Cunge (MVPMC4) technique. It was tested against kinematic-wave routing at scales ranging from 0.05 to 150 km² on the Walnut Gulch Experimental Watershed in southeastern Arizona. Analyses demonstrated that MVPMC4 routing significantly improves simulated outflow hydrographs for small to moderate events on watersheds that are 95 km2 and larger. A geomorphic model was developed by modifying KINEROS2 to compute width, depth and slope adjustments from computed changes in sediment storage at each time step. Width and depth adjustments are determined by minimizing total stream power for each reach. A GIS-based interface was developed for model parameterization, coordinating multiple-event batch simulations, tracking cumulative geomorphic change, computing the sediment mass balance, visualizing results, and comparing results from different simulations.

No description available.

Compiled and Edited by Patricia Paylore / For 23rd International Geographical Congress, Moscow, 1976, Pre-Conference Meeting of the IGU Working Group on Desertification, Desert Research Institute, Ashkabad, Turkmen SSR, July 20-26, 1976.

The International Geographical Union Working Group on Desertification In and Around Arid Lands