Dissertations / Theses on the topic 'Arid environments'

Deserts comprise the largest terrestrial biome, making up approximately one third of the Earth’s land mass. They are defined in terms of moisture deficit using the Aridity Index with values <1. A further delineation based on mean annual temperatures into hot (>18°C), cold (<18°C) and polar (<0°C) deserts is employed. In the absence of significant macrobiota, microorganisms are key to desert ecosystems. They are located in near-surface soils, and include a widespread hypolithic mode of colonization, where microbial biomass develops on the ventral surfaces of quartz and other translucent stones. A literature review was conducted to appreciate the status of existing knowledge on these systems. Amongst unresolved questions that arose were the following, which form the basis of this inquiry: What are the taxonomic and functional differences between hypolithic and near-soil communities? Do hypolithic communities assemble differently in deserts of different xeric and thermal stresses? Can the keystone cyanobacterial taxa be cultivated under laboratory conditions to allow manipulative studies? The Mojave Desert in the USA was used as a model to test the extent to which hypolithic and near-surface soil communities vary in both taxonomic and putative functional composition. A common phylogenetic marker (16S rRNA gene ITS region) was used to conclude that soil and hypolithic communities are significantly different, although both were dominated by cyanobacteria. The ubiquitous hypolithic cyanobacterial taxon Chroococcidiopsis was encountered, although communities appeared to be dominated functionally by the diazotrophic genus Nostoc. The data strongly suggest that carbon and nitrogen fixation pathways in desert soils are mediated by the same taxa, although heterotrophic pathways may differ and support distinct assemblages of heterotrophic bacteria. An opportunistic sampling of three sites along a latitudinal gradient in China allowed some inference about adaptations in hypoliths. Communities recovered from the cold Tibetan Desert, Taklamakan Basin Desert, and exposed hillsides in tropical Hong Kong, did not display significant differences at the level of community assembly. This suggests that hypolithic taxa undergo strong selection for xeric and extreme thermal stresses. A cultivation strategy for the keystone taxon Chroococcidiopsis has been lacking and is an obvious impediment to manipulative physiological studies. Here various methods for laboratory cultivation were attempted. This bacterium proved extremely fastidious and displayed slow growth rates. After extensive trials a novel cultivation method was developed. This involved using plastic petri dishes containing liquid growth medium, into which glass coverslips were introduced along with cell suspensions. The surface energy of glass served as a nucleation site for Chroococcidiopsis biofilms (which do not develop on plastic surfaces) and this method was evaluated in growth studies as a means of quantifying growth. This research includes key advances to demonstrate that hypoliths and soil, whilst supporting different communities, likely perform similar functional roles in the desert soil. Selection due to the severe environmental stresses results in similar communities across large latitudinal and environmental gradients. The development of a cultivation strategy paves the way for manipulative physiological studies on these important organisms.
published_or_final_version
Biological Sciences
Doctoral
Doctor of Philosophy

Findings from a number of recent glasshouse studies are reported and their relevance to wheat production practices in Bangladesh is discussed. It was found that application of large amounts of urea gave highest grain yield when the total amount of urea was added immediately after irrigation following germination. The same amount of urea applied before irrigation or in smaller doses throughout the growing season gave lower yield and resulted in higher post-harvest concentrations of soil nitrate. Reducing the total urea application to one quarter of the typical maximum reported value, did not cause a reduction in yield and this could be achieved with only one occasion of irrigation (as opposed to two) following germination. The findings confirm the recommended dosage of urea (typically 250 kg urea ha^-1) and indicate the importance of applying urea after irrigation to maximise yield and minimise post-harvest soil nitrate concentrations. Adding a nitrate fertiliser as opposed to the same amount of urea-N did not result in a significant yield increase. The results indicate that application of urea-N following irrigation results in a rapid availability of soil N for plant uptake. Where severe soil drying occurs in the upper rooting zone, grain field was drastically reduced. This occurred even where longer roots had access to non-limiting amounts of water and nutrients. It was found that roots in the drying soil produced the plant hormone abscisic acid (ABA) and that this had a likely causal significance in decreasing yield. ABA was also produced in plants with ammonium- as opposed to nitrate nutrition and this was also associated with reduced yield. It was concluded that breeding for deep rooting alone would be insufficient to attain high yield if the upper part of root system was exposed to severe soil water deficit. Breeding of deep rooting in combination with a decreased sensitivity of stomatal closure to ABA, is an attractive possibility for plant and yield improvement for semi-arid zones. In the interim, current measures of tillage and mulching that enhance the water content of the upper rooting zone should be encouraged. Such measures are likely to counter the potential ABA-induced inhibition of yield associated with partial root dehydration and incomplete nitrification of soil ammonium.

Soil moisture available to crops is among the main constraints on crop production by smallholder farmers in semi-arid Zimbabwe. Other restrictions, such as limited use of fertilisers and herbicides, stem primarily from socio-economic rather than biophysical constraints. To improve smallholder farming, it is essential to promote soil and water conservation practices (SWC) that consider farmers' management constraints, such as limited availability of labour and Draught Animal Power (DAP).

This study explores the linkages between slope form and slope process in arid environments. In doing so, questions of the development of slopes in arid environments are examined. The age of many arid environment surfaces, combined with the sporadic nature of formative events, means that long-term surface and slope development remains an elusive question in geomorphology. Deserts have inspired many of the most enduring theories of landscape evolution and continue to provide a test-bed for new and emerging ideas in geomorphology. The clast-mantled surface of the northeast Jordan Badia presents an ideal opportunity to study the links between surface character and slope processes in arid environments. The northeast Badia also provides an opportunity to explore theories of slope development and the behaviour of earth surface systems. The nature of the clast covered ground surface has been assessed using a new digital aerial photography and image analysis technique. A field study of surface processes has been used to explore links between surface form and slope process. Additionally, a computer based simulation of long-term modification of the spatial distribution of surface clast has been undertaken. Given the subtle variation in earth surface form between disparate locations, a new semi-quantitative method of locating sample sites has been developed. The characterization of surface form has identified statistically significant relationships between ground surface character and two-dimensional slope form. Systematic variations in ground surface configuration, both within and between basalt flows, are found to be indicative of the action of slope processes. The first study of ground surface hydrology in the north eastern Badia has been undertaken. The results from a series of rain-storm simulation experiments show subtle but significant links between the action of surface processes and variations in ground surface form. The controls on surface process are diverse and vary in significance with position in the landscape. A combination of ground surface characterization and process studies has identified several interesting geomorphological phenomena The surfaces exhibit systematic variations in structure and organization. Homeostatic links between form and process are clearly apparent, which suggests that surface form influences and is influenced by process action via a process of positive feedbacks. Given the sporadic and infrequent recurrence of formative events in arid environments, a modelling approach has been developed to understand the long-term, spatial dynamics of the ground surface. The model has been used to simulate structure in the surface clast arrangement and the sensitivity of surface organization to physically constrained variations in model parameters. The model also allows the surfaces to be considered as self-organizing earth surface systems. The model results provide new insights into the process-form linkages in operation on clast-mantled arid surfaces. The model results provide new ways of examining and understanding the dynamics of clast mantled arid surfaces and have implications for the application of self-organization in geomorphology.

This study proposes a framework and a process promoting creation of sustainable jobs and businesses in rural, arid and semi-arid agricultural conflict zones of Sub Saharan Africa, focusing on Somalia's societal stabilization and conflict mitigation. This task requires developing risk-reducing measures for infrastructure and service delivery in rural, post-conflict zones. Literature reviews identified two economic growth theories rooted in sustainability concepts for localized, pro-poor development. Ecological Economics Theory (EET) and Endogenous Growth Theory (EGT) are the philosophical bases establishing investment priorities. Additional research regarding Somali culture, key conflict factors, and potential business opportunities, provides an understanding of salient facts in Somalia's on-going, 27-years of war and potential culturally acceptable development pathways. Informal sources, Somali and non-Somali, were consulted to further identify and verify potential avenues for economic growth, sustainability, educational opportunities, allowing Somalia to emerge from the strife it has endured. Visits to Somalia and Somaliland confirmed that livestock, its products and related requirements, are key components for economic growth and job creation. Investigation, via pilot testing and case studies, was undertaken of technologies with potential to improve productive capacity and disrupt existing value chains. Initial framework elements were evaluated for job and business creation, through unstructured, semi-structured interviews, and questionnaire of Somali officials, and Somali and non-Somali conflict zone development practitioners. The pilot test used a small sample size and is a limitation of this work. Findings from the literature review, informal discussions, and the pilot test are synthesized into the framework presented in Chapter 5. The framework proposes development of an innovative, disruptive, and scalable business model that facilitates the simultaneous implementation of renewable energy production. It targets education for the livestock and agroforestry industry of Somalia, improving job and business opportunities. The model proposes modification of used shipping containers for the creation of modular elements, to satisfying infrastructural building components to initiate skills practice, job, and business growth.
Doctor of Philosophy
The wars and conflicts of various types in Africa have made the continent poorer and prevented development in many countries. One of the major, and seemingly intractable conflict locations, is Somalia located in the East Horn of Africa (EHA). This research provides an understanding of salient facts in Somalia's 27 years of war by examining culture and key conflict factors. The objective of this assessment is to identify potential culturally acceptable pathways that will lead to business opportunities and development as a means of conflict mitigation. The improvement of job opportunities for youth is viewed as a means to offset the current participation in the ongoing conflict. Somali and non-Somali sources were consulted to identify and verify avenues for economic growth, sustainability, and educational opportunities. Visits to Somalia and Somaliland confirmed that livestock, and related products, are key components for development and job creation. Technologies with potential to improve productive capacity and disrupt existing value chains were also evaluated. Findings from informal discussions and a pilot test of a proposed framework are presented. The framework identifies elements for development of an innovative, disruptive, and scalable business model that facilitates the implementation of renewable energy production. In addition, it targets education for the livestock and agroforestry industries, improving job and business opportunities.

Chickpea (Cicer arietinum L.) is an important grain legume. Global warming and changes in cropping systems are driving chickpea production to relatively warmer growing conditions. Studies on the impact of climate change on chickpea production highlighted the effect of warmer temperatures on crop development and subsequent chickpea yield. For example, the yield of chickpea declined by up to 301 kg/ha per 1˚C increase in mean seasonal temperature in India. Assessment of whole plant response, particularly flowering and grain filling in warmer environments, in the field is generally an effective screening method. The identification of heat tolerant genotypes can help adapt chickpea to the effects of warmer temperatures. In this study, 167 chickpea genotypes were screened in heat stressed (late season) and non-stressed (normal season) conditions in the field during 2009-10 (year 1) and 2010-11 (year 2) at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), India. The aim of these experiments was to screen chickpea germplasm in contrasting chickpea growing seasons for high temperature tolerance. Plant phenology (days to first flowering, days to 50% flowering, days to first pod, and days to maturity), growth (plant height, plant width and biomass at harvest) and grain yield including pod number per plant, filled pod number per plant and seed number per plant were recorded in both seasons. There was large and significant variation for phenology, growth, grain yield and yield traits. Pod numbers per plant and harvest index are the two key traits that can be used in selection for breeding programs. The genetic variation was also confirmed by canopy temperature depression and the Heat Tolerance Index (HTI). Furthermore, using daily maximum and minimum temperature during the growing period, temperature for chickpea developmental stages (vegetative, flowering and grain filling phases) was calculated for both seasons to understand genotype × environment (G × E) interaction. In addition, sensitivity of male and female reproductive tissues to high temperature is important to explain the effect of heat stress on the reproductive phase. Therefore, field experiment was conducted at ICRISAT under stressed condition (late season) during 2011. The aim of these experiments was to study genetic variation in male reproductive tissue (anther, pollen), its function (pollen germination and tube growth) and pod set. Pollen fertility, in vitro pollen germination, in vivo pollen germination and pod set was examined under different temperatures. The field experiment was compared with controlled environments (stressed and non-stressed conditions). Both anthers and pollen grains showed more structural abnormalities such as changes in anther locule number, anther epidermis wall thickening and pollen sterility, rather than function (e.g. in vivo pollen tube growth). Clearly, chickpea pollen grains are more sensitive to high temperature than the stigma in both the field and controlled environments. Both studies suggested that the critical temperature for pod set was ≥37˚C in heat tolerant genotypes (ICC 1205; ICC 15614 and ICCV 92944) and ≥33˚C for heat sensitive genotypes (ICC 4567; ICC 10685 and ICC 5912). Implementation of molecular breeding in chickpea improvement program depends on the understanding of genetic diversity. Diversity Array Technology (DArT) is a micro-array based method allowing for finding of DNA polymorphism at several thousand loci in a single assay. The aim of this research was to investigate the genetic diversity between the167 chickpea genotypes using DArT markers. Based on 359 polymorphic DArT markers, 153 genotypes showed polymorphism. A dendrogram derived from cluster analysis based on the genetic similarity coefficient matrix for the 153 genotypes was constructed. There were nine groups (group 1-9) identified from dendrogram. The genotypes were collected from 36 countries and ICRISAT breeding lines were also included in the germplasm. Based on eleven quantitative traits (days to first flowering, days to 50% flowering, days to first pod, days to physiological maturity, plant height, plant width, plant biomass, pod number per plant, filled pod number per plant, seed number per plant and grain yield) observed in the field, the diversity groups were arranged under stressed and non-stressed conditions for two years and their relationship of origin was also studied. The group 9 (ICRISAT breeding lines) produced highest grain yield under non-stressed and heat stressed followed by group 3. Those breeding lines were crossbreeds from the ICRISAT’s breeding programs and released in different countries at different times. Furthermore, characterisation of ICRISAT screening environments using 29 years of temperature data was done to understand the chickpea growing season for future breeding programs. Association analysis was conducted on chickpea genotypes evaluated in the field screening for high temperature tolerance. Eleven quantitative traits observed in the field under heat stressed and non-stressed conditions were analysed to understand the genetic control of heat tolerance through marker-trait association. Under heat stress, 44 DArT markers were associated with grain yield and pod characteristics such as total pod number, filled pod number and seed number. A DArT marker was associated with three or four traits and may be efficiently used in improvement of more than one trait at a time. The associated markers for the traits like plant height, plant width, pod number and grain yield were found in the genomic regions of previously reported QTLs. In addition, many genomic regions for phenology, biomass and grain yield under heat stressed and non-stressed conditions. The number of markers significantly associated with different traits was higher under heat stress, suggesting that many genes are present that control plant response to high temperature in chickpea. Four populations, ICC 1356 x ICC 15614; ICC 10685 x ICC 15614; ICC 4567 x ICC 15614 and ICC 4567 x ICC 1356 of F1s, F2s along with their parents were assessed in the field in 2011 at heat stressed condition (late season). The objective of this experiment was to study the inheritance of heat tolerance. Days to first flowering (DFF), pod number per plant (TNP), filled pod number per plant (NFP), seed number per plant (NS) and grain yield per plant (GY) was recorded. Estimates of broad sense heritability for the traits DFF, TNP, NFP, NS and GY were calculated for all four crosses. In this study, parents were heterogeneous for heat response. At extreme high temperature (>40˚C) the population, especially ICC 4567 x ICC 15614, set pods and gave higher grain yield compared with other crosses. The adaptation of chickpea to high temperature may also be improved using more exotic parents to combine allelic diversity for flowering time, pod number, filled pod number, seed number per plant and grain yield. High temperature clearly has an influence on plant growth, development and grain yield. The research has identified heat tolerant sources of chickpea and also found the impact of high temperature on the male reproductive tissue. Studying genetic diversity using DArT markers and understanding diversity group with agronomic traits provided the basis of chickpea response to high temperature. Further research is needed from populations of chickpea crosses using late generations. This will enable the development of heat tolerant chickpea cultivar.

Plant responses to abiotic stress are neither singular nor linear. The research represented within this dissertation was intended to evaluate selected biochemical and physiological responses in two Arugulas (Images 1-5), to agronomic interventions designed to mitigate extreme environmental abiotic factors, characteristic of arid agricultural production regions. Plant stress responses were investigated under field conditions and within controlled environments (CE), during the course of a preliminary trial and three independent studies, all four directly related. The preliminary trial evaluated harvest and postharvest nutritional content (i.e., antioxidants) of two Arugulas, Eruca sativa (L.) Cav. ssp. sativa (P. Mill.) and Diplotaxis tenuifolia (L.) DC cv. Sylvetta; grown under field conditions in the semi-arid upper Sonoran Desert. In this trial, we defined baseline harvest and postharvest antioxidant values for the Arugulas, cultivated in a semi-arid environment. The initial study, conducted within a CE utilizing a water recycling system, evaluated changes in the nutritional value of three specialty leafy cruciferous vegetables: D. tenuifolia, E. sativa and Lepidium sativum; when subjected to increasing salinity levels in the nutrient solution. It was concluded that, when specific Crucifers are irrigated with moderately high levels of salinity, neither harvest nor postharvest nutritional values are compromised. The second study, investigated the response of a suite of plant physiological parameters (e.g., yield and photosynthetic rate) in the three Crucifers to salinity, within the CE. This research provided guideline salinity values where yields did not decline, and encourages growers to consider water resources compromised by salinity and nutrient solution recycling. During the third study, the influence of environmental conditions on the nutritional content in leafy vegetables, prevalent immediately before harvest, was investigated; by subjecting plants to reduced sunlight treatments and early irrigation termination. We observed that, modulating light intensity late in the season, and early irrigation termination strategies, modify the nutritional content of leafy vegetables; and potentially the subsequent postharvest shelf life. Collectively evaluated, this research suggests that simple agronomic interventions are valuable, yet practicable, tools that can enhance the nutritional content of specialty vegetables, in arid regions: be that intervention an imposed controlled-stress, utilizing nutrient recycling systems within a CE, or basic light-reduction and irrigation termination strategies within conventional fields systems.

From a geomorphological point of view, and environments are characterised by complex process interactions and suites of landforms which can be sensitive to their controlling parameters. Relationships between sediment, moisture and soil crust characteristics are no exception. Field research and a programme of laboratory study were undertaken between 1993 and 1995 on the soils of the northern Badia of Jordan to advance knowledge on aspects of and zone soil dynamics, with a particular emphasis on crusting. The research focuses primarily on the effect soil crusts have upon the equilibrium of sediment dynamics at a hillslope scale and a ridge-furrow scale. The implications of the crust upon moisture storage within the surface layers of the soil are examined and the spatial characteristics which arise due to management practices and climate variables considered. A new, non-destructive dielectric technique to investigate moisture content in dryland soils has been developed and tested. Monitoring has taken place to examine the effects of irrigation upon the surface characteristics of the surrounding soil, with special reference to evaporation fluxes within a furrow and the associated precipitation of salts. The role of small-scale topography tends to be underestimated. Different types of crust have been studied from various topographic locations. Soil fabric and porosity have been studied, to increase understanding of micro-scale depositional and erosional processes. A new method of tracing' fine material through the upper soil profile has been developed. As crusts form, the tracer can be used to monitor the movement of fines, permitting a much clearer understanding of soil and water dynamics as a result of rainfall events.

Plugged and abandoned well pads throughout the Uintah Basin face reclamation challenges due to factors including a harsh climate, invasive species, and high salt loads. Finding ways to alleviate soil sodicity could improve soil reclamation success. Gypsum, sulfur, activated carbon, and Biochar are being applied to improve soil parameters negatively impacted by sodicity, but the direct impact of these amendments on Uintah Basin soils is still largely unknown. The aim of this study was two-fold. (1) Evaluate the effectiveness of gypsum, sulfuric acid, Biochar, activated carbon, and combinations of these amendments in reducing the impact of soil sodicity of the Desilt and Conglomerate soils by measuring amendment impact on percent dispersion, saturated hydraulic conductivity, crust bulk density, infiltration, and crust formation. (2) Compare a crust bulk density method using ImageJ to the clod wax density method and a modified linear extensibility percent equation to the linear extensibility percent equation to assess whether the novel methods can be used to accurately measure and calculate soil crust bulk density and shrink swell potential while reducing human error and analysis time.

The spatial distribution and properties of rainfed orchards in semi-arid environments result from complex interactions between man and the physical and economical environment. This thesis investigates a number of these interactions in the context of the mechanisation of management practices since the 1950's. It is shown how the practice of clean sweeping (i.e. frequent shallow tillage) influences the orchard water balance and how the removal of traditional soil and water conservation structures affects the connectivity of overland flow to the river system. Although clean sweeping prevents transpiration and competition by weeds, it also constrains the root growth in the plough layer, so that the trees cannot access the water from small rain events. In addition, clean sweeping promotes accelerated soil erosion. It appears that the practice of clean sweeping limits the water availability in orchards on loamy soils with an annual rainfall in the order of 300 mm. It is demonstrated that the presence and properties of rainfed orchards are related to spatial patterns of soil characteristics and climate. The observed decline in conservation structures like terraces and check-dams leads to an increase in the connectivity of water and sediment to the river system. An alternative for these traditional techniques to retain the water and the soil is the application of cover crops. The advantage of cover crops is that they do not limit the field size. A drawback in dry areas is the competition for water and nutrients between the cover crop and the trees. Field evidence and water balance simulations suggest that cover crops are feasible in areas with an annual precipitation of 500 mm or more.

In arid landscapes limited resources are concentrated into fertile patches that allow greater productivity than would otherwise be expected. Fertile patches are created and maintained by processes that modify soil topography and interrupt the flow of resources across the landscape. These processes may be abiotic or biotic in origin. Species that modify, maintain or create habitat have been termed ecosystem engineers. One group of soil disturbing ecosystem engineers creates fertile patches by modifying soil microtopography through foraging for food and creating habitat. This thesis examines the effects of soil foraging animals on resource concentration in arid environments and how effects are moderated by species and landscape. Chapter 1 provides an overview of the importance of fertile patches in arid systems and describes previous research on the effects of ecosystem engineers in arid environments. Chapter 2 examines how fertile patch creation by a well-studied arid zone engineer, the ant, varies between ant species and landforms, demonstrating that while we can generalise about the effects of ant nests on water flow and nutrient levels, differences in soil type, nest density and ant species across sites are likely to moderate these effects. Chapters 3, 4 and 5 compare the engineering effects of reintroduced native species, the Greater bilby (Macrotis lagotis) and Burrowing bettong (Bettongia lesueur) with the Sand goanna (Varanus gouldii) and the invasive European rabbit (Oryctolagus cuniculus) across three Australian landforms, revealing differences between reintroduced and invasive engineers at the both patch and landscape scales. At the landscape scale, differences in pit densities and resource concentration in foraging pits between landforms suggest that fertile patch development is not uniform. Chapter 6 examines whether the structure of the pit or the presence of litter per se explains observed increases in plant germination in foraging pits, and compares temperature and soil moisture conditions in bilby and bettong pits to the soil surface. Chapter 7 is a review that builds upon previous chapters, published and unpublished literature of the potential for reintroductions of ecosystem engineers to restore ecosystem function in degraded environments. Chapter 8 summarises the research presented in this thesis and its implications, and suggests directions for future work.

This study develops understanding of vegetation change and water, sediment and carbon dynamics in semi-arid environments. Objectives were addressed using an integrated ecohydrological and biogeochemical approach. Fieldwork, over two contrasting grass-woody transitions at the Sevilleta National Wildlife Refuge, New Mexico, USA; quantified vegetation structure, soil structure and the spatial distribution of soil carbon resources. Over both transitions; woody sites showed a lower percentage vegetation cover and a greater heterogeneity in vegetation pattern, soil properties and soil carbon. Soil organic carbon differed in both quantity and source across the sites; with levels higher under vegetation, particularly at the woody sites. Biogeochemical analysis revealed soil organic carbon to be predominantly sourced from grass at the grassland sites. In contrast, at the woody sites soil organic carbon under vegetation patches was predominantly sourced from woody vegetation, whilst inter-patch areas exhibited a strong grass signature. Investigation of function focussed on the hydrological response to intense rainfall events. Rainfall-runoff monitoring showed woody sites to exhibit greater; runoff coefficients, event discharge, eroded sediment and event carbon yields. In contrast to grass sites, biogeochemical analysis showed the loss of organic carbon from woody sites to exhibit a mixed source signal, reflecting the loss of carbon originating from both patch and interpatch areas. To examine the linkages between vegetation structure and hydrological function, a flow length metric was developed to quantify hydrological connectivity; with woody sites shown to have longer mean flow pathways. Furthermore, in addition to rainfall event characteristics, flow pathway lengths were shown to be a significant variable for explaining the variance within fluxes of water, sediment and carbon. Results demonstrating increased event fluxes of sediment and carbon from woody sites have important implications for the quality of semi-arid landscapes and other degrading ecosystems globally. It is thus necessary to translate the understanding of carbon dynamics developed within this study to the landscape scale, so changing fluvial carbon fluxes can be incorporated into carbon budgets, research frameworks and land management strategies at policy-relevant scales.

The overall aim of this project was to integrate chemical and archaeological techniques by the study of a number of specific individual cases from temperate, semi-arid and waterlogged sites. Samples taken from a Roman road profile at the temperate site of Silchester were found to be composed of chert and kaolinite. No phosphate, an indicator for human/animal activity was identified. Analysis of the metal content of the road samples showed high levels of iron in all layers with the highest percentage found in the orange layer. The iron may be present as an iron silicate which is found around areas where metalworking (especially ironworking) took place.

This study investigates the conditions and the levels of satisfaction with indoor environmental quality (IEQ) in naturally ventilated (NV) learning environments in Bayero University, Kano and compares the results to international comfort standards' thresholds. It examines the thermal and visual comfort, acoustic quality as well as the indoor air quality of six learning environments in the University consisting of four lecture theatres and two laboratories. Researches in IEQ have shown that good quality indoor environment enhances occupants' comfort, wellbeing, raises their productivity, and most importantly for this research, it raises students' performances, reduces absenteeism, and reduces stress and fatigue among teachers. IEQ researches are mostly being undertaken in the four most advanced continents that are situated in the temperate regions of the world, but not in sub-Saharan Africa. Using both measurement and survey methods, internal and external physical parameters (air and radiant temperatures, air velocity, relative humidity, background noise, sound pressure level, horizontal and vertical illumination level, carbon dioxide concentration and particulate matter) were evaluated. The assessments were undertaken three times covering ten months, August 2016 to May 2017, which coincided with the three distinct seasons (warm and wet; cool and dry & hot and dry) in Kano. PMV model, as always, failed to predict the thermal conditions of the learning environments. Similarly some of the measured and calculated IEQ parameters, have not met the thresholds specified by the adaptive components of ASHRAE-55, but were in agreement with EN 15251, the respondents expressed their acceptance of their learning environments, subjectively. This is not surprising as these standards were often based on experiments implemented in developed countries, where the severity of the climatic conditions and the culture are dissimilar to sub Saharan Africa. The outcome of the research is hoped to raise awareness of IEQ potentialities among the academia, building industry professionals, building owners, university managers and other education policy makers in the region.

Spatially explicit knowledge of land cover is increasingly important for environmental modeling and decision support for land managers. Such knowledge is often provided over large regions by thematic maps produced from remotely sensed satellite data. Remote sensing of vegetation in semi-arid areas is complicated, however, by high levels of landscape spatial heterogeneity, resulting in large part from spatially varying soils, topography, and microclimates. Increased understanding of spatial distributions of vegetation and the factors affecting them will enhance our ability to inventory and monitor natural resources, and to model potential consequences of land management alternatives and larger issues such as global climate change. In addition, the uncertainty in spatial knowledge must be made spatially explicit in order to determine where more information is needed and where predictions maybe less reliable. Geostatistical kriging and multiple linear regression interpolation were used to map climate spatial distributions over the San Pedro River watershed, southeastern Arizona. Both methods used climate station location and elevation and climate data. Although mean interpolation errors were similar, kriging climate with elevation as external drift was preferred due to the patterns of spatial bias in regression errors. Interpolation results provided a step toward understanding climate influence on vegetation in this area. Accuracies of four land cover maps covering the upper San Pedro watershed, mapped from remotely sensed data, were determined using aerial photography, digital orthophoto quadrangles, and airborne video data reference data sets as alternatives to contemporaneous ground-collected data. Overall map accuracies were 67--75%; class accuracies varied more for smaller classes than for larger ones. Finally, the uncertainty of occurrence of the low-accuracy Mesquite Woodland class was mapped using simple indicator kriging with locally varying means and data derived from accuracy assessment information. Enhanced class discrimination in an independent validation data set confirmed the utility of this procedure. The results of these analyses can provide direct input for use in environmental modeling and can inform land management decision making, and the methods can be employed in other settings where spatial variability and uncertainty play large roles in the landscape.

The ability of feral herbivores to reduce the amount of food available to domestic livestock has rarely been quantified. This thesis seeks to examine the degree to which feral goats (Capra hircus) reduce the availability of pasture and shrub biomass for other herbivores. The interaction between feral goat populations and their food supply will be explored using a modelling approach. In addition to this it will also examine the cost of controlling goats and attempt to identify the cost efficient target densities for control operations. The implications of this information for management will be discussed. There are two ways an animal population can interact with its food supply, through: (1) intrinsic food shortages, and (2) extrinsic food shortages. Intrinsic food shortages occur when a negative feed-back loop exists between the animal population and their food supply. This means the animals affect the availability of their food and their food supply affects the dynamics of the animal population. Since the animals are affecting their own food supply it could be said that they will also affect the availability of that food to other herbivores if they consume the same species. Extrinsic food shortages occur when there is no feed-back from the animals to their food supply. Food availability is determined by extrinsic factors such as rainfall and is unaffected by the animal population. To determine how feral goats interact with their food supply several models will be examined, and these include: (1) single species models which use data from the animal population only. These have historically been used to identify density dependence which is commonly caused by the animal population being regulated through their food supply in the case of large herbivores, and (2) trophic models which incorporate data from at least two trophic levels in an ecosystem, in this case those being the animal population and the vegetation they are thought to consume. These models allow a more direct examination of the relationship between the feral goat population and their food supply. The various models were fitted to data collected on the field sites and the following results were obtained: (1) the dynamics of the feral goat populations could not be represented by single-species models. This was most probably due to the stochastic environment in which they lived causing the level of density dependence experienced by the goats to vary greatly masking its presence. (2) the rate of increase of the goat population could be predicted by the numerical response of rate of increase to pasture biomass. This demonstrated that food availability influenced the dynamics of the goat population. (3) goat density affected the availability of some species of shrub biomass. There was, however, no response seen in the availability of pasture species to changes in goat density. Since the study was conducted during a drought this is in agreement with other studies which indicated that goats will primarily browse during dry spells but switch to pasture species when conditions improve following rainfall. These results indicate that a negative feed-back loop does exist between feral goat populations and their food supply since the goats affected the availability of some shrub species and so they suffer intrinsic food shortages. This means goats have the ability to reduce the availability of food to other herbivores providing both are eating the same species. Cost-efficiency analysis showed that the cost of removing individual feral goats increases exponentially as density decreases because the search time per animal becomes greater. This relationship was used to construct a model that predicted the cost of achieving a target density. The model describing cost of control over density was also combined with a productivity model based on the numerical response of feral goats to pasture biomass to predict the cost of maintaining target densities under different environmental conditions. Using these models the most cost-efficient density identified was 11 goats/km2. From this study we can make the following conclusions: (1) feral goats have the ability to reduce the amount of shrub biomass available to other herbivores during dry conditions (2) their ability to influence the availability of pasture species remains unknown (3) given the cost of initial and ongoing control and the minimal benefits that result it would be difficult to justify controlling goats during a drought on the field sites.

Thesis (DPhil)--Stellenbosch University, 2002.
ENGLISH ABSTRACT: Freshwater is the most fundamental of all life-supporting resources that determine our social, economic and political wellbeing. It is, however, only a small percentage of the world's water resources and is also unevenly distributed. Arid regions make-up about forty percent of the world's land area and have a large proportion of the world population, however, they only have a small fraction of the freshwater compared to other areas. Conventional freshwater sources in arid environments such as surface water in rivers, lakes and dams are often seasonal, available mainly during the rainy season. Equally, only a small part of the rain (0 - 5% of rainfall) infiltrates into groundwater reserves, and even this groundwater displays high rates of salinisation such that the end-water is too saline for human consumption. The poor quality of groundwater in arid regions is generally understood, however, it is always assumed that this is mainly a problem in areas where surface water does not occur. The study investigates seasonal groundwater salinisation in ephemeral (seasonal) river sources in some parts of Namibia and aims to derive a better understanding of the nature of this problem and how it affects people in these areas. It also looks at some possible solutions to the problem with the aim of informing water managers and scientists who are responsible for formulating solutions for water supply to areas in arid regions. These solutions are designed to take advantage of available opportunities in the study areas namely; the abundant supply of solar energy, alternative sources of freshwater such as fog and general atmospheric moisture, and adaptations for water collection in animals that inhabit these regions. The results show that groundwater in shallow ephemeral river sources of the Namib Desert and the Cuvelai delta in North central Namibia display high seasonal variation in Total Dissolved Solids (TDS) and chemical composition. The lowest TDS values are recorded during the rainy season, mainly after the first rains in the high rainfall areas and only after flood events in the lower rainfall regions. The groundwater salinity increases during the remainder of the year and in most cases becomes too saline for drinking purposes. The investigations of possible solutions indicate that small-scale photovoltaic reverse osmosis; solar distillation and fog collection could be used to address the seasonal shortage of potable water in these areas. The low-pressure (6 bar) reverse osmosis desalination experiments show that it is possible to operate the unit on a solar-driven pump to produce enough water to cover the typical daily water demand of a village in the Namib Desert. This unit would produce about 4600 litres per day (l/day) of 500- mg/l TDS product water, which exceeds the water production of similar world-leading small-scale RO units in Australia and The Canary Islands. The results also show that the cost of solar distillation units (solar stills) can be reduced sufficiently to make them a viable option for water supply to individual households in these rural areas. The study also found that fog is a feasible alternative source of freshwater in some of the study areas. The fog water is generally of 'A' quality drinking water according to the WHO-derived Namibian Drinking Water Quality Guidelines (NDWQG) and can be used directly or mixed with the saline groundwater to provide potable water. Mixing of the above-mentioned waters is particularly suitable in the Central Namib Desert because the period of high groundwater salinity coincides with that of peak fog deposition. The results also show that fog water can be collected with vanous polymeric greenhouse shade netting that can be easily obtained, and provides guidelines on the correct percentage shade coefficient and weave of possible fog collector mesh to intending users of fog collection technology in areas where the polypropylene mesh that is used in Standard Fog Collectors is not available. The investigations of surface properties of fog-harvesting beetles and experiments with various prototype collectors show that it is possible to increase water production in fog collectors existing today. The hydrophobic surface conditions as were found on the cuticles of fog-basking beetles (Onymaeris unguicularis and Onymacris bieolor) would enhance formation and runoff of large fog droplets on the collector surface. The prototype extractor-fan- and cooling system-based collectors show that it is possible to increase fog collection on polymeric meshes about three times and also that a comparable volume of atmospheric moisture can be collected even when there is no fog, up to a relative humidity of about 40%. In conclusion the study emphasizes that groundwater salinity in arid regions is at times a seasonal problem that should be considered in water supply strategies for these regions. Also that atmospheric moisture is a feasible alternative source of freshwater in some arid regions that often exceeds rainfall several times and should be considered as an important aspect of the strategies to address water problems in these areas. The study strongly recommends that scientists, engineers and water managers in these regions should always investigate the available opportunities such as climatic conditions (e.g. fog deposition) and adaptations for water collection/conservation that are found in the endemic plants and animals in order to develop sustainable solutions to this problem. They should also constantly update themselves on developments/opportunities that arise in the larger water industry that could be of benefit to water supply initiatives for remote areas in developing countries. Lastly, the study serves to better the understanding of the nature of groundwater salinity in arid environments that are dependent on seasonal surface flow for water supply as well as to contribute to the formulation of solutions to this problem in these areas, particularly in west coast hyper arid environments where conventional sources of freshwater are most inadequate. It also emphasises the role of materials science (polymers) and environmental engineering as well as that of UNESCO associated scientific institutions in the formulation of sustainable solutions to some of the current water problems in arid regions. Keywords: Arid lands, hydrochemistry, sources of freshwater, desalination, atmospheric moisture
AFRIKAANSE OPSOMMING: Vars water is die mees fundamentele van aIle lewensonderhoudende natuurlike hulpbronne wat ons sosiale, ekonomiese, en politieke welstand bepaal. Dit is egter slegs 'n klein gedeelte van die totale waterbronne van die wereld, en is boonop baie oneweredig versprei. Natuurlike waterarm gebiede (woestyne en halfwoestyne) beslaan ongeveer veertig persent van die landoppervlakte van die aarde en word bewoon deur 'n relatief groot persentasie van die wereldbevolking, maar beskik oor slegs 'n klein gedeelte van die varswater in vergelyking met ander gebiede. Konvensionele bronne van varswater in waterarm gebiede, soos oppervlaktewater in riviere, mere en darnme, is dikwels seisoenaal, en slegs beskikbaar gedurende die reenseisoen. Verder beland slegs 'n klein gedeelte van die reenval (0 - 5%) in die ondergrondse waterreserwes, en selfs hierdie grondwater vertoon 'n hoe mate van versouting, sodat die eindproduk te brak is vir menslike gebruik. Die swak gehalte van grondwater in waterarm gebiede word algemeen verstaan, maar daar is tot nog toe aanvaar dat dit oor die algemeen slegs 'n probleem is in gebiede waar oppervlaktewater me voorkom nie. Hierdie studie ondersoek seisoenale grondwaterverbrakking in seisoenale rivierbronne in sekere dele van Namibie en beoog om 'n beter begrip te formuleer van die aard van die probleem en hoe dit die inwoners van hierdie gebiede raak. Daar word ook ondersoek ingestel na moontlike oplossings vir die probleem, met die doel om 'n inligtingsbron vir waterbestuurders en wetenskaplikes wat verantwoordelik is vir die formuleer van oplossings vir watervoorsiening in waterarm gebiede daar te stel. Hierdie oplossings is ontwerp om voordeel te trek uit die beskikbare geleenthede in die ondersoekgebiede, naamlik; die oorvloedige beskikbaarheid van sonenergie, altematiewe bronne van varswater soos mis (Eng. "fog") en atmosferiese vog in die algemeen en aanpassings (Eng. "adaptations") vir die opvang van water wat voorkom by diere, veral insekte, in hierdie gebiede. Die resultate toon dat grondwater in die vlak seisoenale rivierbronne van die Namibwoestyn en die Cuvelai-delta in noordsentraal Namibie hoe seisoenale variasie in totale opgeloste stowwe (TVS) en chemiese samestelling vertoon. Die laagste TVS-waardes word waargeneem tydens die reenseisoen, hoofsaaklik na die eerste reen in die hoe-reenvalgebiede en eers na vloede in die lae-reenvalgebiede, Die soutgehalte van die grondwater neem toe gedurende die res van die jaar en in die meeste gevalle verbrak die water tot ondrinkbare vlakke. Die ondersoek na moontlike oplossings dui aan dat kleinskaalse fotovoltaiesgedrewe tru-osmose, sondistillasie en die opvang van mis (Eng."fog collection") aangewend kan word om die seisoenale tekort aan drinkwater in hierdie gebiede aan te spreek. Die laedruk (6 bar) tru-osmose-ontsoutingseksperimente wys dat dit moontlik is om die eenheid met behulp van 'n sonkraggedrewe pomp te bedryf en voldoende water te lewer vir die tipiese daaglikse drinkwaterbehoeftes van 'n nedersetting in die Namibwoestyn. Hierdie eenheid sal sowat 4600 liter per dag (l/d) water, met 'n TVSwaarde van 500 mg/I, lewer. Dit is aansienlik meer as die lewering van soortgelyke eenhede in Australie en die Kanariese Eilande. Die resultate wys ook dat die koste van sondistillasie-eenhede genoegsaam verminder kan word om dit 'n lewensvatbare opsie vir watervoorsiening aan enkelhuishoudings in die plattelandse gebiede te maak. Die studie het ook bevind dat die opvang van mis 'n toepaslike alternatiewe bron van varswater is in sekere van die studiegebiede. Die miswater is oor die algemeen 'A' -gehalte drinkwater vol gens die Namibiese gehalteriglyne Vir drinkwater (gebasseer op bepalings van die Wereldgesondheidsorganisasie) en dat dit net so, of vermeng met brak grondwater, gebruik kan word as drinkwater. Vermenging is besonder geskik in die sentrale Namibwoestyn, aangesien die periode van hoe grondwaterverbrakking saamval met die piek van benutbare misneerslag. Die resultate toon ook aan dat miswater opgevang kan word met verskeie tipes polimeriese skadunet, wat maklik verkrygbaar is, en verskaf riglyne vir die optimale skadu-koeffisient en weefpatroon van moontlike misvangsnette vir voomemende gebruikers van misvangstegnologie in gebiede waar die polipropileennet wat in die standaard miskollekteerders gebruik word nie, beskikbaar is nie. Die ondersoek van oppervlakeienskappe van mis-koesterkewers (Eng. "fog harvesting beetles") en eksperimente met verskeie prototipe versamelaars toon dat dit moontlik is om die waterproduksie van bestaande kollekteerders te verhoog. Die hidrofobe oppervlaktetoestande soos gevind op die opperhuid van die mis-koesterkewers (Onymacris unguicularis en Onymacris bicolor) bevorder die vorming en afloop van groot misdruppels op die versameloppervlak. Die prototipe suigwaaier- en verkoelerstelselgebasseerde versamelaars toon dat dit moontlik is om die misvogversameling op polimeriese nette tot drie maal te verhoog en dat 'n vergelykbare volume atmosferiese vog versamel kan word, selfs in die afwesigheid van mis, tot by 'n relatiewe humiditeit van ongeveer 40%. Ten slotte benadruk die studie dat grondwatersoutgehalte in waterann gebiede soms 'n seisoenale probleem is, en dat dit in ag geneem moet word in watervoorsieningstrategiee vir sulke gebiede. Dit benadruk ook dat atmosferiese vog 'n bruikbare alternatiewe bron van varswater kan wees in sekere areas, waar dit dikwels verskeie male meer is as reenval, en gesien behoort te word as 'n belangrike aspek in strategiee om waterprobleme in hierdie gebiede aan te spreek. Die studie beveel sterk aan dat wetenskaplikes, ingenieurs en waterbestuurders in hierdie gebiede altyd die beskikbare geleenthede soos klimaatstoestande (bv. misneerslag) en aanpassings vir vogvangslbewaring wat voorkom by inheemse plante en diere sal navors om sodoende onderhoudbare oplossings vir die probleem te vind. Hulle behoort deurlopend op hoogte te bly met ontwikkelings/geleenthede wat ontstaan in die wyer waterindustrie, wat van waarde kan wees in by waterverskaffmgsinisiatiewe vir afgelee gebiede in ontwikkelende lande. Laastens dien die studie om 'n beter begrip daar te stel van die aard van grondwatersoutvlakke in waterarm gebiede wat afhanklik is van seisoenale oppervlaktevloei vir watervoorsiening sowel as om 'n bydrae te lewer tot die formuleer van oplossings tot die probleem in hierdie gebiede, veral in die hiperdroe omgewings aan die Namibiese weskus, waar konvensionele waterbronne mees onvoldoende is. Dit benadruk ook die rol van materiaalkundige wetenskappe (polimere) en omgewingsingenieurswese sowel as die UNESCO-geassosieerde wetenskaplike instellings in die formulering van volhoubare oplossings vir sommige van die huidige waterprobleme in waterann gebiede. Sleutelwoorde: Waterarm gebiede, hidrochemie, bronne van varswater, ontsouting, atmosferiese vog

This study examines the spatial patterns of soil parameters to test the hypothesis that shrub encroachment initiates a change in scale of soil heterogeneity, which consequently influences a landscape's biotic and abiotic interactions and thus the susceptibility of soil to erosion. Grassland, shrubland and badland sites were established in two semi-arid environments; the Karoo, South Africa and the Sevilleta National Wildlife Refuge, New Mexico, U.S. 108 soil samples from each of the eleven 60m x 60m plots were analysed for bulk density, shear strength, texture, aggregate stability, organic matter content, pH, conductivity and available sodium, calcium, magnesium, potassium and phosphorus content. Geostatistical analyses determined that, at a scale representative of the vegetation community, the grassland landscape appeared relatively homogeneous in its distribution of soil parameters. Shrublands, however, demonstrated an increase in heterogeneity of all soil parameters. Periodicity in the semi-variograms indicated that regular patterns across the landscape were evident for all parameters and thus likely to represent the differences between shrub and intershrub regions. Due to the complex plant-soil interactions, and the interactions amongst the soil parameters themselves, the cyclic patterns represent areas of high and low erodibility. More pronounced patterns were identified in the badlands. This indicates that, if the conditions are right, changes in plant-soil interactions caused by soil parameter redistribution in shrubland landscapes can exacerbate erosion leading to further degradation in the form of badlands. Comparisons between the two semi-arid regions suggest that although local variations in soil type and different species of vegetation will affect the intensity of the spatial response, the underlying patterns are similar at both locations and hence, potentially, at a global scale.

The expansion of mesquite (Prosopis velutina) in southeastern Arizona and attempts to control or remove mesquite have been well documented. However, removal of woody plants may affect the distribution and quantities of nutrient resources within soil including changes in carbon (C) and nitrogen (N) cycling and changes in the amounts of C and N sequestered in these soils. We hypothesized that mechanical mesquite removal would alter soil microclimate and nutrient inputs, leading to changes in soil C and N cycling and microbial communities and activities.This study was conducted at two separate semi-arid grassland sites south of Tucson, AZ during a three-year period. There were six study plots at each site, three plots from which mature mesquite trees had been mechanically removed and three plots where mature mesquite trees were left intact. We measured the soil temperature and moisture, C and N pools, N2O and CO2 fluxes, N mineralization rate, and microbial resistance and resilience to determine if short term changes in any of these parameters were taking place.No significant differences in N mineralization rate or microbial resistance or resilience were found between the soils under intact mesquite and from plots where mesquite had been mechanically removed. Soil temperature was not statistically analyzed because temperature was taken in only one plot per treatment and without within-treatment replicates, t-tests could not be performed. Statistically significant differences in soil moisture, total soil C and N, microbial biomass C and N, heterotrophic plate counts, and CO2 and N2O fluxes were found between treatments on different dates throughout the experiment. Despite this finding of some significant differences between treatments for some parameters measured, no recognizable pattern of changes was observed during this study. Over the course of the experiment, the data did not support our overall hypothesis, that short term changes in microclimate following mesquite removal would alter soil C and N cycling and microbial communities and activities.

Current climate change trends are affecting the magnitude and recurrence of extreme weather events. In particular, several semi-arid regions around the planet are confronting more intense and prolonged lack of precipitation, slowly transforming these regions into deserts. In this thesis we present a stochastic (meso-scale) model for vegetation-precipitation interactions for semi-arid landscapes. Extensive simulations with the model suggest that persistence in current trends of precipitation decline in semi-arid landscapes may expedite desertification processes by up to several decades.

Australia’s rangelands encompass approximately 80% of the continent and generate significant wealth through a range of industries. The rangelands comprise four major ecosystem types, these are: grasslands, shrublands, woodlands and savanna. The ecological legacy of early pastoral development in most of Australia‟s semi-arid shrublands is largely one of degradation and desertification (Wilcox and McKinnon, 1974; Curry et al. 1994; McKeon et al. 2004; Mabbutt et al. 1963; Pringle and Tinley, 2001). Since the 1980‟s, there has been a slow and general shift by the pastoral industry towards sustainable stocking rates (Watson et al. 2007; Pringle and Tinley, 2001).To implement grazing systems that better align stocking rates with carrying capacity in the semi-arid shrublands, pastoralists require a much more advanced understanding of patch patterning and ecological processes at a paddock scale. This understanding of theory could improve the management decisions made by pastoralists and other land managers (e.g. mining environmental officers, carbon offset developers, conservation park rangers, Indigenous communities) and assist them in their immediate challenge of cost-effective rehabilitation of degraded areas. Landscape function theory was largely developed for this purpose.Landscape function theory was developed as a way to assess and interpret patch patterns and ecological processes that occur at a range of spatial scales (Ludwig et al. 1997). Landscape function theory is used to explain the concept of „functional heterogeneity‟ which is an information-rich phenomenon that has enabled the development of cross-scale metrics. Landscape function theory is based on four primary principles, these are: 1. Patchiness can be characterised by patch size, orientation, spacing and soil surface condition. 2. Natural landscapes have a characteristic spatial self-organisation, often expressed as patchiness. 3. Deviations from the „characteristics‟ or „natural‟ patchiness are seen as degrees of dysfunctionality and there is a long continuum from highly functional to highly dysfunctional patches. 4. Restoration or replacement of missing or ineffective processes in the landscape will improve soil surface conditions and soil habitat quality.Landscape function theory and the associated landscape function analysis (LFA) methodology have become an accepted standard for the ecological assessment of rangeland environments. However, there have been a limited number of studies in Australia that have thoroughly examined the four principles that underpin the landscape function theory. Further interrogation of the principles that underpin the theory has the potential to enhance its utility and validate its assumptions. Therefore, the aim of this thesis was to test the four principles of landscape function theory in a semi-arid shrubland environment.The overarching hypothesis of this thesis was that clear spatial patch patterns occur at a range of scales within the case study paddocks and these patterns determine the ecological functionality and resilience of the area. Specifically, I sought to find evidence of distinct patch-interpatch patterns and associations at a range of scales in the lower Murchison region of Western Australia (WA) and examined the impact that grazing and seasonal conditions can have on this natural patchiness. The study involved four components: 1. Empirical quantification of patch-scale heterogeneity and investigation into the existence of a gradient of functionality at a patch-scale. 2. Measurement of patch patterning at a paddock scale and an evaluation of sequences and associations of patch-interpatches in the context of their contribution to landscape functionality. 3. Investigation of the impact of grazing and seasonal conditions on perennial grass populations and the potential impacts of this on patch patterning and ecological processes. 4. Investigation of livestock grazing behaviour and its implications for patch patterning and ecological processes.Significant variation was detected (P<0.05) between the physical and chemical properties of 11 different patch-interpatch subclasses. Heterogeneity within individual patches was also significant (P<0.05) and the greatest variation occurred within ecologically stable, high-order patches. Higher-order patch-interpatch subclasses were highly functional and when compared to the lower-order patch-interpatch subclasses, the former had: higher soil respiration rates (>45%) (P<0.05), this indicates these subclasses are more biologically active; more than twice the number of perennial plant species within the patch (P<0.05); higher soil infiltration rates (>70% more rapid) (P<0.05), this indicates these subclasses can capture more rainfall and surface runoff when it occurs; and five times more carbon and nitrogen. A gradient of highly functional patches and highly dysfunctional interpatches was identified.Distinct patch patterning between different land-types was found. The granitic shrubland land-type had a much greater proportion of the lower-order resource-shedding interpatch subclass (>85% of the area) compared to the other land-types. In contrast, Acacia sandplains had a higher proportion of the ecologically functional patches compared to granitic shrublands. Depending on the land-type, it was concluded that a functional ecosystem will generally have balanced proportions of particular patch-interpatch subclasses as this is likely to lead to the efficient capture and cycling of water and nutrients. In contrast, a degraded ecosystem will have higher proportions of ecologically dysfunctional patch-interpatch subclasses. A number of significant spatial associations and repeating sequences of individual patch-interpatch subclasses were found to occur in the study area. In the case study paddocks, distance-from-water did not have any significant effect on the relative proportions of the different patch-interpatch subclasses.Native perennial grasses support perennial shrub patches in maintaining ecological stability and landscape processes in semi-arid shrublands. Perennial grasses were monitored over a 12 month period to determine whether summer rest from Merino sheep grazing had an impact on perennial grass populations. The change in the number of perennial grasses over the 12 month period was variable ranging from a 36.7% increase to mortality rates as high as 80.2%. There was evidence to suggest that the grasses in the exclosure treatments (i.e. no grazing) may have been conditioned by previous grazing events in such a way that made them highly susceptible to extended periods of moisture stress. Land-type, distance-from-water and stocking rate did not have a significant impact on the change in the number of perennial grasses over the 12 month period. Resting perennial grasses during the summer may be of benefit; however, given the high mortality rates in most of the paddocks, it was clear that seasonal conditions had a substantial overriding influence on the outcome.Five major factors influenced sheep grazing behaviour in the study paddock; these include: land-type, greenness cover, time of day, air temperature and distance-from-water. The GPS-collared sheep demonstrated a clear grazing preference for the higher value land-types (i.e. alluvial plains and hardpan washplains). The results also indicated that the sheep were selectively grazing areas with high greenness cover (as expressed by Normalised Difference Vegetation Index [NDVI]). The results highlight the importance of understanding the selective grazing characteristics of Merino sheep when designing paddock layouts and developing management plans. This is because repetitive, selective grazing of high-value land-types has the potential to modify the natural patch patterning and ecological processes.This study found empirical evidence which substantiates landscape function theory and concludes that it has significant application at a range of spatial scales in the semi-arid shrublands. The results explain why landscape function theory is the current standard for the assessment and interpretation of rangeland environments in Australia. Landscape function theory is the result of an evolutionary synthesis of earlier work, and it continues to be progressively refined as our knowledge of the complex patterns and ecological processes of the rangelands is improved.Based on the findings of this study, I consider that there are three areas of further inquiry which could assist land managers to practically apply landscape function theory and contribute towards the restoration of degraded Australian rangelands, these are: determination of the „functional‟ composition of patch-interpatches subclasses for a range of land-types in the Australian rangelands that could be used as benchmarks for land managers; further empirical quantification of the ecological processes that drive landscape function to assist in simulation modeling and the estimation of cost / benefit of rehabilitation efforts; and the potential role that grazing management can play in the restoration of dysfunctional patch-interpatch patterns and ecological processes in the semi-arid shrublands.

Riparian Zones are considered biodiversity and ecosystem services hotspots. In arid environments, these ecosystems represent key habitats, since water availability makes them unique in terms of fauna, flora and ecological processes. Simple yet powerful remote sensing techniques were used to assess how spatial and temporal land cover dynamics, and water depth reflect distribution of key land cover types in riparian areas. Our study area includes the San Miguel and Zanjon rivers in Northwest Mexico. We used a supervised classification and regression tree (CART) algorithm to produce thematic classifications (with accuracies higher than 78%) for 1993, 2002 and 2011 using Landsat TM scenes. Our results suggest a decline in agriculture (32.5% area decrease) and cultivated grasslands (21.1% area decrease) from 1993 to 2011 in the study area. We found constant fluctuation between adjacent land cover classes and riparian habitat. We also found that water depth restricts Riparian Vegetation distribution but not agricultural lands or induced grasslands. Using remote sensing combined with spatial analysis, we were able to reach a better understanding of how riparian habitats are being modified in arid environments and how they have changed through time.

This thesis presents a semi-automatic method to analyze morphometric features and landscape elements based on Self Organizing Map (SOM) as an unsupervised Artificial Neural Network algorithm in two completely different environments: 1) the Man and Biosphere Reserve “Eastern Carpathians” (Central Europe) as a complex mountainous humid area and 2) Lut Desert, Iran, a hyper arid region characterized by repetition of wind-eroded features. In 2003, the National Aeronautics and Space Administration (NASA) released the SRTM/ SIR-C band data with 3 arc seconds (approx. 90 m resolution) grid for approximately 80 % of Earth’s land surface. The X-band SRTM data were processed with a 1 arc second (approx. 30 m resolution) grid by the German space agency, DLR and the Italian space agency ASI, but due to the smaller X-SAR ground swath, large areas are not covered. The latest version 3.0 SRTM/C DEM and SRTM/X band DEM were re-projected to 90 and 30 m UTM grid and used to generate morphometric parameters of first order (slope) and second order (cross-sectional curvature, maximum curvatures and minimum curvature) by using a bivariate quadratic surface. The morphometric parameters are then used in a SOM to identify morphometric features (or landform elements) e.g. planar, channel, ridge in mountainous areas or yardangs (ridge) and corridors (valley) in hyper-arid areas. Geomorphic phenomena and features are scale-dependent and the characteristics of features vary when measured over different spatial extents or different spatial resolution. Morphometric parameters were derived for nine window sizes of the 90 m DEM ranging from 5 × 5 to 55 ×55. Analysis of the SOM output represents landform entities with ground areas from 450 m to 4950 m that is local to regional scale features. Effect of two SRTM resolutions, C and X bands is studied on morphometric feature identification. The difference change analysis revealed the quantity of resolution dependency of morphometric features. Increasing the DEM spatial resolution from 90 to 30 m (corresponding to X band) by interpolation resulted in a significant improvement of terrain derivatives and morphometric feature identification. Integration of morphometric parameters with climate data (e.g. Sum of active temperature above 10 ° C) in SOM resulted in delineation of morphologically homogenous discrete geo-ecological units. These units were reclassified to produce a Potential Natural Vegetation map. Finally, we combined morphometric parameters and remotely sensed spectral data from Landsat ETM+ to identify and characterize landscape elements. The single integrated data set of geo-ecosystems shows the spatial distribution of geomorphic, climatic and biotic/cultural properties in the Eastern Carpathians. The results demonstrate that a SOM is a very efficient tool to analyze geo-morphometric features under diverse environmental conditions and at different scales and resolution. Finer resolution and decreasing window size reveals information that is more detailed while increasing window size and coarser resolution emphasizes more regional patterns. It was also successfully applied to integrate climatic, morphometric parameters and Landsat ETM+ data for landscape analysis. Despite the stochastic nature of SOM, the results are not sensitive to randomization of initial weight vectors if many iterations are used. This procedure is reproducible with consistent results.
Avhandlingen presenterar en halvautomatisk metod för att analysera morfometriska kännetecken och landskapselement som bygger på Self Organizing Map (SOM), en oövervakad Artificiell Neural Nätverk algoritm, i två helt skilda miljöer: 1) Man and Biosphere Reserve "Eastern Carpathians" (Centraleuropa) som är ett komplext, bergigt och humid område och 2) Lut öken, Iran, en extrem torr region som kännetecknas av återkommande vinderoderade objekt. Basen för undersökningen är det C-band SRTM digital höjd modell (DEM) med 3 bågsekunder rutnät som National Aeronautics and Space Administration släppte 2003 för ungefär 80 % av jordens yta. Dessutom används i ett mindre område X-band SRTM DEM med 1 bågsekund rutnät av den tyska rymdagenturen DLR. DEM transformerades till 90 och 30 m UTM nätet och därav genererades morfometriska parametrar av första (lutning) och andra ordning (tvärsnittböjning, största och minsta böjning). De morfometriska parametrar används sedan i en SOM för att identifiera morfometriska objekt (eller landform element) t.ex. plan yta, kanal, kam i bergsområden eller yardangs (kam) och korridorer (dalgångar) i extrem torra områden. Geomorfiska fenomen och objekt är skalberoende och kännetecken varierar med geografiska områden och upplösning. Morfometriska parametrar har härletts från 90 m DEM för nio fönsterstorlekar från 5 × 5 till 55 × 55. Resultaten representerar landform enheter för områden från 450 m till 4950 m på marken dvs. lokal till regional skala. Inflytande av två SRTM upplösningar i C och X-banden har studerats för identifikation av morfometriska objekt. Förändringsanalys visade storleken av upplösningsberoende av morfometriska objekt. Ökning av DEM upplösningen från 90 till 30 m (motsvarande X-bandet) genom interpolation resulterade i en betydande förbättring av terräng parametrar och identifiering av morfometriska objekt. Integration av morfometriska parametrar med klimatdata (t.ex. summan av aktiv temperatur över 10° C) i SOM resulterade i avgränsningen av homogena geoekologiska enheter. Dessa enheter ha används för att producera en karta av potentiell naturlig vegetation. Slutligen har vi kombinerat morfometriska parametrar och multispektrala fjärranalysdata från Landsat ETM för att identifiera och karaktärisera landskapselement. Dessa integrerade ekosystem data visar den geografiska fördelningen av morfometriska, klimatologiska och biotiska/kulturella egenskaper i östra Karpaterna. Resultaten visar att SOM är ett mycket effektivt verktyg för att analysera geomorfometriska egenskaper under skilda miljöförhållanden, i olika skalor och upplösningar. Finare upplösning och minskad fönsterstorlek visar information som är mer detaljerad. Ökad fönsterstorlek och grövre upplösning betonar mer regionala mönster. Det var också mycket framgångsrikt att integrera klimatiska och morfometriska parametrar med Landsat ETM data för landskapsanalys. Trots den stokastiska natur av SOM, är resultaten inte känsliga för slumpvisa värden i de ursprungliga viktvektorerna när många iterationer används. Detta förfarande är reproducerbart med bestående resultat.
QC 20100924

Reduced water availability and salinity are two major environmental factors influencing crop establishment in semi-arid environments. Therefore the effect of reduced water availability using polyethylene glycol (PEG) 4000 solutions and of salinity (NaCl) on the germination of six soybean cultivars was examined. Cultivars differed in their response to reduced water availability and salinity and in their ability to recover from the stresses. A large increase in germination during a recovery period at 0 MPa following water stress suggested that PEG was not toxic whilst the failure of seeds to recover from high salinity revealed the toxic effects of NaCl. At the same water potential, germination in saline conditions was higher than that in PEG and the rate of water uptake by individual seeds was more rapid in NaCl solutions than in PEG. The most plausible explanation for the greater water uptake and germination in NaCl is that seeds accumulated salts which lowered their osmotic potential. The effects of NaCl on seedling growth were much greater when experiments were conducted in a hydroponic system compared with a paper towel method. However, analysis of the solutions soaking the paper towels revealed that 4.25 mMolal Ca2⁺ was available to the seeds in this system in saline conditions. This may have reduced Na⁺ uptake or provided a protective effect against Na⁺ toxicity. Germination (40%) was possible at a tissue Na⁺ concentration in the embryonic axis of 9.3mg g-1 FW whilst seedling growth was completely inhibited at a tissue Na⁺ concentration of 6.1 mg g^-1 FW. Germination at higher tissue Na⁺ concentrations was associated with higher K⁺+Ca2⁺ concentrations, suggesting that these ions may protect the seeds in the pregermination phase against salinity. A reduction in seed vigour due to ageing resulted in reduced germination under saline conditions compared to the germination of unaged seeds, but there was no significant interaction between salinity and seed ageing. However, unaged seeds showed a greater increase in germination after transfer to 0 MPa than did the aged seeds. Since both the site of ageing and the toxic effect of NaCl is the cell membrane, there may be additive effects of NaCl toxicity on cell membrane in aged seeds.

La política i la planificació del usos del sòl concerneix la presa de decisions col·lectives mitjançant la qual una societat decideix on, dins del seu territori, s'han de dur a terme diferents activitats socioeconòmiques i estableix les disposicions que controlin la naturalesa d'aquestes accions per motius ambientals, culturals o històrics. Aquests controls determinen característiques com ara les àrees de parcel·la, el seu consum de terres, la seva intensitat, la seva densitat o les normes tècniques de les infraestructures. Per tant, els usos de la terra determinen les diverses activitats socioeconòmiques que es produeixen en una àrea específica, els patrons de comportament humà que produeixen i el seu impacte sobre el medi ambient. Des dels anys noranta, amb l’inici del Land‐Use and Land‐Cover (LULC) change project del International Geosphere‐Biosphere Program (IGBP) i del International Human Dimensions Program (IHDP), importants avenços en el camp de la modelització de l’LULC s’ha produït. Supervisar els canvis de LULC és fonamental per desenvolupar estratègies efectives per a la gestió espacial i la protecció del medi ambient, ja que els canvis induïts pels humans han afectat el rendiment dels serveis ecosistèmics i han contribuït a alterar els cicles bioquímics que controlen el funcionament del sistema terrestre. En la política i planificació dels usos del sòl diversos tipus d’actors humans, les seves relacions i l’estructura social i institucional influeixen en els processos LULC. A causa de la seva situació geoestratègica, situada entre les nacions occidentals desenvolupades i les creixents economies asiàtiques, i els centres mundials de producció de petroli, les ciutats de la Península Aràbiga han guanyat ràpidament importància en l’economia global. En conseqüència, els espais urbans d’aquestes ciutats han ampliat la seva presència més enllà dels centres històrics. Atès el ràpid desenvolupament de les ciutats àrabs en les últimes dècades, el terme "ciutat instantània" s'ha proposat per descriure la forma en què semblen haver aparegut de sobte, fora del no‐res. En aquesta tesi doctoral, l’àrea d’estudi correspon a la ciutat d'Al Ain, situada als Emirats Àrabs Units (EAU). Es tracta d’una interessant ciutat de grandària mitjana per analitzar pel seu desenvolupament urbà molt ràpid i per una ubicació estratègica a la frontera entre els Emirats Àrabs Units i Oman. Es caracteritza per un vast i àrid desert, dominat per sorra i grava, amb llits de rius secs intermitents, una regió muntanyosa escarpada (Jabel Hafeet) i una zona de sòls i oasis fèrtils, amb grans reserves d'aigua subterrània. La tesi s'estructura en vuit capítols amb l'objectiu principal d'avaluar les trajectòries LULC d'Al Ain, entre 1984 i 2014, i comparar‐les amb la gestió de dos plans generals d’ordenació urbana. Per mapar i quantificar els canvis en els LULC, es va aplicar una combinació particular de tècniques de teledetecció i SIG. Posteriorment, per verificar la hipòtesi inicial sobre l'especificitat de l'expansió urbana d'Al Ain i per avaluar les conseqüències dels canvis d’LULC des d'un punt de vista paisatgístic, es van calcular les mètriques de paisatge dels patrons urbans (agregats, lineals, transversals o nodals). El següent pas va consistir en aplicar una anàlisi estadística a partir de les dades censals, a escala de districte, per millorar la comprensió dels processos LULC, principalment els relacionats amb la població, el sexe i el seu origen. Després, es van establir els principals motors de canvi d’ LULC a partir del coneixement expert i de les conseqüències socioambientals de les dinàmiques. Finalment, es va avaluar el futur creixement del Pla Al Ain 2030. Aquesta tesi doctoral, doncs, representa un pas més enllà del coneixement de les trajectòries i formes urbanes, essent una contribució empírica amb una combinació innovadora d’eines: una combinació particular de tècniques RS i SIG; una comparació del creixement urbà real amb les directrius proporcionades pels plans d’ordenació; una avaluació detallada dels patrons del paisatge; una anàlisi estadística mitjançant dades censals a escala de districte; i, finalment, una aproximació a través del coneixement expert aplicat per determinar les principals forces i conseqüències socioambientals.
Land‐use policy and planning concerns collective decision‐making by which a society decides where, within its territory, different socioeconomic activities should take place, and establishes provisions that control the nature of such actions due to environmental, cultural or historical reasons. These controls determine features such as plot areas, their land consumption, their intensity, their density or technical standards of infrastructures. Therefore, land‐uses determine the diverse socioeconomic activities that occur in a specific area, the patterns of human behavior they produce, and their impact on the environment. Since the 1990s, with the initiation of the Land‐Use and Land‐Cover (LULC) change project of the International Geosphere‐Biosphere Program (IGBP) and the International Human Dimensions Program (IHDP), considerable advances in the field of modeling of LULC change have occurred. Monitoring LULC changes is critical to develop effective strategies for spatial management and environmental protection because human‐induced changes have affected the performance of ecosystem services and contributed to alter the biochemical cycles that control the functioning of the Earth system. In land‐use policy and planning diverse types of human actors, their relationships and the social and institutional structure influence LULC processes. Due to their geostrategic situation, located between the developed Western nations and the rising Asian economies, and world centres of oil production, cities in the Arabian Peninsula have rapidly gained significance in the global economy. In consequence, urban spaces in these cities have extended their presence far beyond the historic centres. Given the rapid development of Arab cities in recent decades, the term ‘instant city’ has been proposed to describe the way they seem to have suddenly appeared out of nowhere. In this PhD thesis the study area comprised Al Ain city, located in the United Arab Emirates (UAE). It is an interesting medium‐sized town to analyse due to its very rapid urban development, and a strategic location on the border between UAE and Oman. It is characterized by a vast, arid desert, dominated by sand and gravel, with intermittent dry riverbeds, a rugged mountainous region (Jabel Hafeet) and an area of fertile soils and oases, with large reserves of groundwater. The thesis is structured in eight chapters with the main objective of assessing LULC trajectories of Al Ain, from 1984 to 2014, and of comparing them with the management of two master plans. To map and quantify LULC changes, a particular combination of remote sensing and GIS techniques was applied. After that, to verify the initial hypothesis about the specificity of Al Ain urban sprawl and to evaluate the consequences of LULC changes from a landscape point of view, landscape metrics of urban patterns (aggregated, linear, leapfrogging or nodal pattern) were calculated. The next step consisted in applying a statistical analysis using census data, at district scale, to improve the understanding of LULC processes, mainly those related to population, sex and origin. Later, the main driving forces of LULC changes were established based on expert knowledge and the socioenvironmental consequences of such dynamics. Finally, future growth was evaluated from the Plan Al Ain 2030. This PhD thesis represents one step beyond the knowledge about urban trajectories and forms, being an empirical contribution with an innovative used combined of tools: a particular combination of RS and GIS techniques; a comparison of real urban growth with the guidelines provided by master plans; a detailed assessment of landscape patterns; a statistical analysis using census data at district scale; and, finally, an expert knowledge approach applied to determine main driving forces and socioenvironmental consequences.

Resistance equations developed for pipe flows and open channel flows cannot be applied to model overland flows uncritically. The formulation of these equations employs several assumptions that are specific to the conditions in which they were developed and cannot be universally applied. The hydraulic behaviour of overland flow is distinct from that of pipe and channel flows and can be characterised by a high degree of variability both over space and over time as roughness elements are progressively inundated with increasing depth. A novel methodology of measuring overland flows in the field at a high- resolution permits examination of the interaction between flow variables and surface roughness. Reconstructing the water surface from elevation data and flow extent provides an estimation of the distribution of flow depths and offers a complementary perspective to more conventional approaches. Overland flows are observed to be highly variable both across and between hillslopes. The distribution of flow depths can be modelled using a two-parameter gamma distribution; both parameters show distinct variations with distance downslope and represent the progressive inundation of roughness elements with increasing depth. The flow interacts with soil surface form where it is capable of eroding its bed and the observed slope- independence of rill velocity can be explained by a feedback between flow state (as characterised by the Froude number) and surface roughness. While the existence of this interaction is affected by soil-type, the soil is observed to have little influence on the relationship between surface roughness and overland flow. Resistance is found to be spatially variable; some of this variability could be explained by the classification of areas of similar microtopogiaphy as identified in the field. This classification can be approximated by a thresholded index-based classification and provides a tool for up-scaling to the hillslope scale. Relating roughness to resistance is not straightforward. Complex natural soil surfaces vary in innumerable ways. Traditional roughness measures fall short of providing an adequate description of the complex soil surfaces observed in the field. A variety of alternative measures are developed, each of which captures a different attribute of surface form. These measures are tested to examine their influence on overland flow resistance and a suite of roughness-resistance models is developed which includes the effect of hillslope position to different degrees. Modelled flow resistance can be separated into a constant term and a depth-dependent term and can be easily incorporated into models of hillslope hydrology. This resistance is observed to decline where a hydrological connection, once established, is then maintained. Examination of the concept of hydrological connectivity in a semi-arid context suggests that the interaction between runoff generation and transfer determines not just flood peaks but also total flow amount. It is suggested that flow resistance and hence runoff transfer should be afforded the same detailed consideration as infiltration parameters, i.e. a spatially distributed and variable value (as a function of depth) that can be organised into discrete units akin to those developed for runoff generation. The parameterisation of both infiltration and resistance in this way provides a crucial interaction through the redistribution of soil moisture and runoff over hillslope surfaces. Through this mechanism, the observed complex and nonlinear runoff response to storm events may be explained as these attributes interact with rainfall characteristics and flow network development. Further understanding of this interaction could have practical implications for catchment management and affect the prioritisation of land management decisions.

An annual life history is often viewed as a model adaptation to arid environments. Annuality is predicted to have evolved in response to low adult survival and high seedling survival. In this study I evaluated the idea that increases in aridity should be associated with the evolution of an annual life history. I also investigated the correlated evolution of annuality and growth form. Ancestral character states for life history characters and climate variables were mapped onto a molecular phylogeny (obtained using plastid trnL-trnF and psbA-trnH and nuclear ETS sequences) of the genera Trichogyne and Ifloga (Asteraceae). Bayesian methods were used for phylogeny inference and maximum likelihood methods for ancestral state reconstructions. Only two phylogenetically independent contrasts were obtained and so the association between changes from annuality to perenniality and increases in aridity along branches of the tree were recorded and evaluated using Fisher's exact test. In order to account for ancestral character state reconstruction uncertainty, four different possible scenarios suggested by the maximum likelihood methods for the evolution of annuality were examined. This is the first molecular phylogeny of the group. Bayesian analysis of the sequence data places the Trichogyne+ Ifloga clade within the Gnaphileae. The genus Ifloga is shown to be paraphyletic. Trichogyne ambigua, as currently described, is polyphyletic and may contain two species. The origin of the Trichogyne+ Ifloga clade is within southern Africa and a northwards migration via the arid corridor is suggested to explain the disjunct distribution of the two Northern Hemisphere species. There is an association between the duration of the moisture growing season and the evolution of annuality. This is consistent with the idea that annuality is favoured by long drought periods making perennation difficult. The evolution of annuality was correlated with a non-woody, tufted, growth form. Amphi-basicarpy was discovered for T. polycnemoides, making it only the second known example of this reproductive strategy within Asteraceae.

Coastlines along the Arabian Sea are susceptible to marine inundation from Makran Subduction Zone (MSZ) earthquakes and tropical cyclones. Sediments deposited by these forms of inundation can expand the decadal instrumental record of events to include millennial timescales in regions without rich historical records (i.e., Oman). On November 28, 1945 a 8.1 M_w MSZ earthquake generated a tsunami that inundated coastlines of the Arabian sea with wave heights as high as 13m. The stratigraphic, sedimentological, foraminiferal, and geochemical signatures of deposit were examined from a small (12 km²), microtidal lagoon in Sur, Oman. The 1945 tsunami deposit contained distinctive taphonomic assemblages of foraminifera and bivalves. Below the 41cm thick 1945 shell-rich deposit at Sur Lagoon, seven additional anomalous sand (mean grain size of 3.73&phis; ± 1.66; very fine sand) layers, ranging in thickness from 7 to 32cm, were found preserved within fine-grained lagoonal sediment (mean grain size of 4.44&phis; ± 1.66; very coarse silt). The seven inferred overwash layers have features consistent with the 1945 tsunami deposit such as fining upward trends, marine foraminifera (e.g., Amphistegina spp., planktics) and increased concentrations of calcium and strontium. By contrast, the surrounding lagoon deposits contain finer grain sizes, intertidal and nearshore foraminifera (e.g., Ammonia tepida, miliolids), and increased concentrations of titanium and magnesium. Based on these data, the seven overwash layers found below the 1945 tsunami deposit have been attributed to marine inundation. Radiocarbon dating indicated an age of 3127 to 2515 cal yr BP for the deepest stratigraphic unit.

Frankincense, a much revered non-timber forest product (NTFP) known as luban in Oman, is a gum-resin extracted from Boswellia sacra (meqerot). In Oman, B.sacra is endemic to ecological zones in and around Dhofar's southern mountain ranges of Jabal Samhan, Jabal Qamar and Jabal Qara. Hojar (Samhan Nejd), Nejd (Qara Nejd), Shazr (Qamar Nejd) and Sha'b are the four B.sacra ecological zones. A suffix (i) after the name (i.e. Hojari or Samhan Nejdi) is indicative of the luban produced in or associated with the respective zone. Traditional Omani B.sacra ownership, management, organization, and frankincense extraction are based on a land parcel system known as menzela. The 1970's oil boom attracted rural labor to urban and oil operation centers in Dhofar and other provinces, thus creating a labor shortage that had a profound transformative impact on frankincense production. This transformation caused frankincense extraction to evolve from an Omani-controlled system to a Somali-dominated hybrid system. Migrant Somali harvesters predominantly control the production and processing of frankincense in the field. Similarly, wholesalers occupy the next rung up the production ladder are the most powerful players in the frankincense industry.Dhofar has a long history of non-timber forest product (NTFP) extraction. From April to mid-June 1999, luban production in the Hojari/Nejdi zone of the study area was estimated at 8,710 kg with a seasonal projection of 24,840kg-30,360kg. B.sacra, a single or multiple stem shrub restricted to wadis in arid environments in or around the Dhofar Mountains, can be found at elevations from 60m above sea level in Wadi Adonib on the coastal plains to 1,770m above sea level in Wadi Kharish (a branch of Wadi Qobyr) in jabal Samhan). Land-use and landcover changes in Dhofar are threatening the fragile stability of B.sacra habitats. Frankincense trees on easily accessible flat or gently sloping terrain are susceptible to stress and mortality from harvesting, grazing and mining, while trees on cliffs and steep slopes are less vulnerable to the effects of these land-use activities.

There is an undisputed need to increase accuracy of snow cover estimation in regions comprised of complex terrain, especially in areas dependent on winter snow accumulation for a substantial portion of their annual water supply, such as the Western United States, Central Asia, and the Andes. Presently, the most pertinent monitoring and research needs related to alpine snow cover area (SCA) are: (1) to improve SCA monitoring by providing detailed fractional snow cover (FSC) products which perform well in temporal/spatial heterogeneous forested and/or alpine terrains; and (2) to provide accurate measurements of FSC at the watershed scale for use in snow water equivalent (SWE) estimation for regional water management. To address the above, the presented research approach is based on Landsat Fractional Snow Cover (Landsat-FSC), as a measure of the temporal/spatial distribution of alpine SCA. A fusion methodology between remotely sensed multispectral input data from Landsat TM/ETM+, terrain information, and IKONOS are utilized at their highest respective spatial resolutions. Artificial Neural Networks (ANNs) are used to capture the multi-scale information content of the input data compositions by means of the ANN training process, followed by the ANN extracting FSC from all available information in the Landsat and terrain input data compositions. The ANN Landsat-FSC algorithm is validated (RMSE ~ 0.09; mean error ~ 0.001-0.01 FSC) in watersheds characterized by diverse environmental factors such as: terrain, slope, exposition, vegetation cover, and wide-ranging snow cover conditions. ANN input data selections are evaluated to determine the nominal data information requirements for FSC estimation. Snow/non-snow multispectral and terrain input data are found to have an important and multi-faced impact on FSC estimation. Constraining the ANN to linear modeling, as opposed to allowing unconstrained function shapes, results in a weak FSC estimation performance and therefore provides evidence of non-linear bio-geophysical and remote sensing interactions and phenomena in complex mountain terrains. The research results are presented for rugged areas located in the San Juan Mountains of Colorado, and the hilly regions of Black Hills of Wyoming, USA.

Thesis (Ph. D.)--University of Kentucky, 2006.
Title from document title page (viewed on May 31, 2006). Document formatted into pages; contains xx, 499 p. : ill. (some col.), maps. Includes abstract and vita. Includes bibliographical references (p. 481-497).

The population size and range of giraffe Giraffa camelopardalis have been greatly reduced in Africa in the past century, resulting in geographical isolation of local populations and some herds surviving at the edge of the species’ preferred range. Numerous factors have contributed to these declines, but historical analysis indicates that habitat loss and fragmentation, human encroachment, disease and poaching are the main threatening processes. These processes can be expected to continue to impact on giraffe populations, particularly as human populations grow and needs for land and resources increase. This study used field data and laboratory analyses to investigate the taxonomy, behaviour and ecology of desert-dwelling giraffe Giraffa camelopardalis angolensis in the northern Namib Desert. This population resides at the extreme of the giraffe’s range. My research also complements the community-based natural resource management (CBNRM) program of the Namibian government, and provides baseline data on the current population status and structure of giraffe in the Kunene Region. The field data, genetic, habitat and forage samples used in this study were collected by myself and a number of research assistants over a period of two years (2001 to 2003), following preliminary research that I undertook between 1999 and 2001. Laboratory analysis of genetic samples was conducted by Dr R. Brenneman and his team at Henry Doorly Zoo, Omaha, NB., as well as by Mr D. Brown at UCLA, CA. Mr W. Gawa!nab and his team at the agricultural laboratory, Ministry of Agriculture, Water and Rural Affairs, Namibia, conducted chemical analyses on plant samples that form part of the giraffe’s diet. The genetic architecture of Namibian giraffe was investigated, including the samples from the desert-dwelling giraffe of the northern Namib Desert and giraffe from Etosha National Park. The results were compared with genetic profiles of giraffe subspecies throughout Africa, but in particular with G. c. giraffa which is the currently-accepted nomenclature of the Namibian giraffe. Results indicated that the Namibian giraffe has five unique haplotypes and is genetically distinct from G. c. giraffa or any other extant subspecies; it is considered here, tentatively, to represent G. c. angolensis. Furthermore, the Namibian Abstract iv giraffe has been separated from other populations for an extended period. Some gene flow has occurred between the desert-dwelling and Etosha NP giraffe population, and can be attributed to recent translocations between these regions. Within the study region, a sharing of haplotypes between three studied subpopulations indicated gene flow among giraffe throughout the northern Namib Desert, and this was confirmed by field-based monitoring. Taken together, these findings suggest that Namibian giraffe should be viewed as important for the conservation of overall genetic variation within Giraffa camelopardalis, although further investigation into the taxonomy of the Namibian form is warranted. Following these findings, I then investigated the behaviour and ecology of the desert-dwelling giraffe. As no previous study has been published on the ecology of G. c. angolensis, there is an information gap in our knowledge of this subspecies. One hundred and fifty six giraffe were identified individually using field-based identification methods and digital imagery. An assessment of the population structure and dynamics indicated marked variation in numbers, sex and age structure, herd structure and densities between three study areas. These variations possibly arose from differences in study area size, aridity, availability of forage and human impacts. I also investigated levels of associations between giraffe within the population using a simple ratio technique, and observed that increased association occurred in smaller populations; there appeared to be a matrilineal social structure. In one bull-biased population, a higher degree of association between bulls was observed compared to bulls in the other two populations. To gain further insight into the distribution and range of giraffe, I collected GPS locations from a combination of field-based monitoring and GPS satellite collars. The GPS satellite collars were the first trial of this technology on giraffe in Africa. Using Range Manager, a MapInfo animal location analysis extension program, I estimated 100% and 95% minimum convex polygon for daily, monthly and annual home range sizes of giraffe in the northern Namib Desert. Giraffe were observed to have large home ranges, with the largest individual range for a bull, Africa-wide, being recorded in this study. Large home ranges correlated with low population density, reduced diversity of forage and, in bulls, increased search areas for receptive cows. Giraffe movements occurred predominantly along riparian woodlands, although seasonal use of other habitats was recorded. Observations Abstract v Abstract vi and data from four GPS satellite-collared giraffe provided high-resolution data on daily movements, and indicated a pattern of highly biphasic movement behaviour that correlated with ambient temperatures. Diurnal activity budgets varied between the sexes, with cows spending more time feeding and resting, while bulls walked and ruminated more frequently. Juveniles rested more often than other giraffe. Seasonal variation in activity budgets was evident, perhaps reflecting use of an energy maximiser strategy for cows and an energy minimiser strategy for bulls. The establishment of artificial water points in the Hoanib River during the study period appeared to alter the seeming independence of giraffe on water in the northern Namib Desert, and also resulted in small-scale shifts in use of the riparian woodland by elephant. To investigate the diet of giraffe, I observed animals feeding in the field and also carried out laboratory analyses of the chemical content of preferred plant species. Seasonal changes in the abundance, moisture and protein content of available food plants correlated with shifts in the diet of giraffe. Giraffe impacted on their preferred forage source, Faidherbia albida, causing distinct structural changes in the individual plants and the F. albida population. This impact, combined with elephant damage and seasonal flood events, has resulted in a shift in the age structure and dynamics of the F. albida population over the past two decades. Finally, I present a brief overview on the history of conservation and management in the Kunene Region. The established CBNRM program provides a baseline for future wildlife conservation and management, of which the desert-dwelling giraffe could be an integral component for non-consumptive tourism. Long-term research on the population’s status, range, behaviour, social structure, habitat requirements, and ecology would help to provide a better understanding of the giraffe’s adaptation to the arid environment, while focussed legislation would enable increased control of communal lands and continue to benefit community-based conservancies.

Doctor of Philosophy
The population size and range of giraffe Giraffa camelopardalis have been greatly reduced in Africa in the past century, resulting in geographical isolation of local populations and some herds surviving at the edge of the species’ preferred range. Numerous factors have contributed to these declines, but historical analysis indicates that habitat loss and fragmentation, human encroachment, disease and poaching are the main threatening processes. These processes can be expected to continue to impact on giraffe populations, particularly as human populations grow and needs for land and resources increase. This study used field data and laboratory analyses to investigate the taxonomy, behaviour and ecology of desert-dwelling giraffe Giraffa camelopardalis angolensis in the northern Namib Desert. This population resides at the extreme of the giraffe’s range. My research also complements the community-based natural resource management (CBNRM) program of the Namibian government, and provides baseline data on the current population status and structure of giraffe in the Kunene Region. The field data, genetic, habitat and forage samples used in this study were collected by myself and a number of research assistants over a period of two years (2001 to 2003), following preliminary research that I undertook between 1999 and 2001. Laboratory analysis of genetic samples was conducted by Dr R. Brenneman and his team at Henry Doorly Zoo, Omaha, NB., as well as by Mr D. Brown at UCLA, CA. Mr W. Gawa!nab and his team at the agricultural laboratory, Ministry of Agriculture, Water and Rural Affairs, Namibia, conducted chemical analyses on plant samples that form part of the giraffe’s diet. The genetic architecture of Namibian giraffe was investigated, including the samples from the desert-dwelling giraffe of the northern Namib Desert and giraffe from Etosha National Park. The results were compared with genetic profiles of giraffe subspecies throughout Africa, but in particular with G. c. giraffa which is the currently-accepted nomenclature of the Namibian giraffe. Results indicated that the Namibian giraffe has five unique haplotypes and is genetically distinct from G. c. giraffa or any other extant subspecies; it is considered here, tentatively, to represent G. c. angolensis. Furthermore, the Namibian Abstract iv giraffe has been separated from other populations for an extended period. Some gene flow has occurred between the desert-dwelling and Etosha NP giraffe population, and can be attributed to recent translocations between these regions. Within the study region, a sharing of haplotypes between three studied subpopulations indicated gene flow among giraffe throughout the northern Namib Desert, and this was confirmed by field-based monitoring. Taken together, these findings suggest that Namibian giraffe should be viewed as important for the conservation of overall genetic variation within Giraffa camelopardalis, although further investigation into the taxonomy of the Namibian form is warranted. Following these findings, I then investigated the behaviour and ecology of the desert-dwelling giraffe. As no previous study has been published on the ecology of G. c. angolensis, there is an information gap in our knowledge of this subspecies. One hundred and fifty six giraffe were identified individually using field-based identification methods and digital imagery. An assessment of the population structure and dynamics indicated marked variation in numbers, sex and age structure, herd structure and densities between three study areas. These variations possibly arose from differences in study area size, aridity, availability of forage and human impacts. I also investigated levels of associations between giraffe within the population using a simple ratio technique, and observed that increased association occurred in smaller populations; there appeared to be a matrilineal social structure. In one bull-biased population, a higher degree of association between bulls was observed compared to bulls in the other two populations. To gain further insight into the distribution and range of giraffe, I collected GPS locations from a combination of field-based monitoring and GPS satellite collars. The GPS satellite collars were the first trial of this technology on giraffe in Africa. Using Range Manager, a MapInfo animal location analysis extension program, I estimated 100% and 95% minimum convex polygon for daily, monthly and annual home range sizes of giraffe in the northern Namib Desert. Giraffe were observed to have large home ranges, with the largest individual range for a bull, Africa-wide, being recorded in this study. Large home ranges correlated with low population density, reduced diversity of forage and, in bulls, increased search areas for receptive cows. Giraffe movements occurred predominantly along riparian woodlands, although seasonal use of other habitats was recorded. Observations Abstract v Abstract vi and data from four GPS satellite-collared giraffe provided high-resolution data on daily movements, and indicated a pattern of highly biphasic movement behaviour that correlated with ambient temperatures. Diurnal activity budgets varied between the sexes, with cows spending more time feeding and resting, while bulls walked and ruminated more frequently. Juveniles rested more often than other giraffe. Seasonal variation in activity budgets was evident, perhaps reflecting use of an energy maximiser strategy for cows and an energy minimiser strategy for bulls. The establishment of artificial water points in the Hoanib River during the study period appeared to alter the seeming independence of giraffe on water in the northern Namib Desert, and also resulted in small-scale shifts in use of the riparian woodland by elephant. To investigate the diet of giraffe, I observed animals feeding in the field and also carried out laboratory analyses of the chemical content of preferred plant species. Seasonal changes in the abundance, moisture and protein content of available food plants correlated with shifts in the diet of giraffe. Giraffe impacted on their preferred forage source, Faidherbia albida, causing distinct structural changes in the individual plants and the F. albida population. This impact, combined with elephant damage and seasonal flood events, has resulted in a shift in the age structure and dynamics of the F. albida population over the past two decades. Finally, I present a brief overview on the history of conservation and management in the Kunene Region. The established CBNRM program provides a baseline for future wildlife conservation and management, of which the desert-dwelling giraffe could be an integral component for non-consumptive tourism. Long-term research on the population’s status, range, behaviour, social structure, habitat requirements, and ecology would help to provide a better understanding of the giraffe’s adaptation to the arid environment, while focussed legislation would enable increased control of communal lands and continue to benefit community-based conservancies.

Various morphological and life history attributes of Acacia karroo Hayne. were investigated in five populations from three environments in South Africa: forest (Cape Vidal, Natal), arid shrubland (Prince Albert, karoo) and savanna (Hluhluwe-Umfolozi Game reserve and ltala Game reserve, Natal). I aimed to elucidate on the distinctive characteristics required for trees to survive in savannas. The combination of frequent fires and intense herbivory in savanna environments creates a disturbance regime not encountered by trees in other situations and it was expected that A.karroo would display specific adaptations of growth form, life history, and reproductive ecology - adaptations which would reflect the strong selective pressure imposed by fire and herbivory on juvenile savanna trees to grow above flame height and browse limit in order to recruit into the mature canopy. A. karroo in savannas was found to have an unbranched, vertical growth form, and is thus maximising height gain. Reproduction was delayed until the trees were above the reach of flames and herbivores. Savanna A.karroo trees had fewer, smaller spines than trees in the other two environments, even though spines are generally considered to be effective in defense against mammalian herbivores. It is therefore suggested that a combination of low 'apparency' to browsers and rapid growth rate is an effective herbivore avoidance strategy in conditions where the need to escape from the fire trap makes a trade-off of growth rate for defensive structures unacceptable. The architecture of mature savanna trees reflects their history of rapid growth in earlier stages and they have smaller canopies, and thus lower reproductive capabilities, than equivalently sized trees in other environments.