Landscapes, as well as being physical spaces, are imagined and invested with meaning. The way they are thought about influences what is done to them. Conservation and development programmes in Zimbabwe's south-east 'lowveld' have been rooted in a particular conceptualisation of landscape - as wilderness. This derives from the experiences and priorities of colonial settlers and has had two facets. On the one hand the landscape came to be constituted as one of adventure, mystique and danger - a fearful place that 'pioneers' sought to tame into a productive landscape through cattle ranching or irrigation. On the other hand it has been viewed as a pristine natural landscape that must be preserved, rehabilitated or consciously manufactured. In both these manifestations African people were written out of the landscape. Their uses, perceptions and experiences of this landscape have been ignored in policies deriving from this 'wilderness vision'. Dryland agriculture in the low veld has been regularly dismissed as inappropriate, rather than a key livelihood strategy. Irrigation developments have been biased towards large-scale initiatives in the commercial sector. Livestock management strategies, other than those recommended for commercial ranching, have been discouraged. Wildlife utilisation schemes have delivered minimal returns to communities and imposed coercive regulations on resource use, deepening antagonism over land; but conservation initiatives such as a transfrontier national park are going ahead - bolstered by economic imperatives, global environmental agendas and donor priorities. Land reform has failed to take account of the way the landscape is bound up with identity through its embodiment of ancestral spirits and function as a repository of social memories. The turbulent dynamics around the ongoing farm invasions in Zimbabwe may open space for previously silenced constructions of landscape to influence policy. An awareness of the flexible and multiple nature of livelihood strategies and further debate on the restitution of ancestral lands would go a long way towards improving livelihoods in the lowveld.

Decomposition of organic matter is a critical component in global biogeochemical cycling. While decomposition rates have been robustly predicted for mesic systems, modeling decomposition dynamics in drylands has proven to be problematic, reflecting a need to account for processes that may be unique to dryland systems: low and spatially variable vegetation cover, high rates of soil movement, and high levels of radiant energy exposure at the soil surface. Recent empirical evidence suggests that the discrepancies between measured and predicted decomposition rates in drylands may be due to the greater influence of abiotic drivers, such as soil-litter mixing (SLM) and solar radiation, on plant litter decomposition relative to more mesic systems. UV-driven photodegradation may dominate until SLM reaches a threshold, at which point litter is shielded from radiation and microbial processes become predominant. The overarching goal of this dissertation was to examine the influence of SLM and solar radiation on decomposition of foliar and woody plant litter in a dryland ecosystem undergoing woody plant encroachment. A series of four complimentary experiments sought to quantify the effects of these abiotic drivers on decomposition in relation to variables such as vegetation patch type (e.g., beneath a shrub canopy, in a grass patch, on bare ground), radiant energy regime (e.g., full sun vs. shade), geomorphic surface (e.g., sandy, Holocene-age vs. clay-rich, Pleistocene-age soils), seasonality of litter fall (e.g., summer vs. winter), and litter quality (e.g., grass, shrub leaf, woody). Results indicate that interactions between SLM and photodegradation are complex and mediated by variations in ground cover which influence the local radiant energy environment and the movement of soil across the landscape by wind and water. Decomposition rates were significantly influenced by SLM, UV radiation, radiant energy regime, vegetation structure, and initial litter quality. While these results confirmed the importance of SLM and photodegradation as dryland decomposition drivers, they also reinforced the need for additional research to further clarify the relative importance of these processes under field conditions, particularly the interplay between UV radiation and SLM and their relative influence on biotic and abiotic decomposition processes. Given the changes in climate and vegetation projected for drylands, it is critical to further elucidate the influence of these processes on dryland biogeochemical cycling, as their effects may be magnified or dampened under future conditions. A deeper understanding of the processes driving biogeochemical cycling that may be unique to systems undergoing shifts in plant lifeform composition will allow us to better account for the fate of carbon in these globally important ecosystems.

Wheat is one of the major crops of Utah and for more than 50 years farmers have been raising wheat on the dry lands of the state. The system they use is known as the alternate cropping or crop-follow system and consists of one year of crop alternating with one year of clean cultivation known as fallow. Wheat removes a considerable amount of the natural plant food elements from the soil each year. This is especially true of nitrogen. According to Bracken and Greaves (9) the original low supply of nitrogen in most Utah soils together with the depleting effects of alternate wheat and fallow has the possibility of making nitrogen rather than moisture the limiting factor of crop production in certain dry-farm areas. The amount of nitrogen removed from the soil by the wheat crop is only a portion of the total supply. Such factors as leaching to a lower depth beyond the feeding range of the plant, erosion, denitrification, and volatilization through biological and possibly chemical action are thought to be responsible for the loss of nitrogen unaccounted for by crop removal. The results of several investigators indicate that this loss is approximately twice as much as was removed by the crop. Since nitrogen is one of the major factors responsible for high yields and high quality of wheat, it naturally follows that any reduction of the amount of nitrogen in the soil produces a corresponding reduction in yield and quality of wheat. Recent reports show that this condition exists in Utah as well as in other areas. As a result of this reduction in yield and quality of wheat, processors are concerned about the problems. The seriousness of the problem cannot be over-emphasized. Ways and means of checking these losses and subsequently increasing the yield and quality are being studied. Three possible procedures for increasing soil nitrogen have been suggested: 1. the use of legumes, especially alfalfa, in a rotation program; 2. non-symbiotic nitrogen fixation: and 3. the use of commercial fertilizers. Since legumes have not been grown to any great extent, the only other natural source of nitrogen has been non-symbiotic fixation. Evidence in this field of investigation, however, indicates that this source is inadequate and that other sources must be bad. Also, the data indicate that no effective methods have been found which increase non-symbiotic fixation. Limited information suggests that further study is needed on the use of legumes for increasing the nitrogen and organic matter content of dry farm soils. This investigation is confined to the use of commercial fertilizers as one solution to the general problem.

Doctor of Philosophy / Department of Agronomy / Scott A. Staggenborg and Alan J. Schlegel / Previous work in the High Plains with alternative planting geometries of corn and grain sorghum has shown potential benefits in dryland production. Studies conducted in 2009-2011 at Tribune, KS evaluated five planting geometries in corn and grain sorghum: conventional, clump, cluster, plant-one skip-one (P1S1), and plant-two skip-two (P2S2). Geometries were evaluated at three plant densities in corn: 3.0, 4.0, and 5.1 plants m[superscript]-2. Every measured corn production characteristic was affected by planting geometry, seeding rate, or an interaction in at least one of the years. Corn planted in a P2S2 configuration produced the least above-ground biomass, kernels plant[superscript]-1, kernels ear row[superscript]-1, and the highest kernel weight. Conventionally planted corn minimized harvest index and maximized stover production. Alternative geometries produced similar harvest indices. Grain yield response to seeding rate varied by geometry and year. Responsiveness and contribution of yield components were affected by geometry. Yield and yield components, other than ears plant[superscript]-1, were the least responsive to seeding rate in a cluster geometry. Clump planting consistently maximized kernels plant[superscript]-1. Prolificacy was observed in the cluster treatment and barrenness in the skip-row treatments. Light interception at silking was highest for clump and conventional geometries and lowest for the skip-row treatments. Corn in a P2S2 configuration did not fully extract available soil water. Conventionally planted corn had the lowest levels of soil water at tassel-silk indicating early-season use which potentially affected kernel set. In the lowest yielding year, grain water use efficiency was highest for clump and P2S2. Across-years, grain yields were lower for corn planted in a P2S2 geometry. Across-years corn yields were maximized when planted in clump at low or intermediate plant density, conventional and P1S1 at low plant density, P1S1 at high density, or cluster at any density. Planting grain sorghum in a P1S1 or P2S2 configuration reduced total biomass, grain yield, water use efficiency for grain production (WUEg), and water use efficiency for biomass production (WUEb) compared to conventional, clump, or cluster geometries at the yield levels observed in this study. Total water use was unaffected by planting geometry although cumulative water use at flower / grain fill was higher for conventional, clump, and cluster than for skip-row configurations. Sorghum planted in a conventional geometry was always in the highest grouping of grain yields. Grain yields from sorghum in either a cluster or clump geometry were each in the top yield grouping two of three years. When evaluated across-years, sorghum planted in a clump, cluster, or conventional geometry resulted in similar levels of above-ground biomass, grain yield, WUEg, and WUEb. Clump or cluster planting appear to have substantially less downside in a high yielding year than skip-row configurations. A comparison of corn and sorghum reinforced the findings of others that the relative profitability of the crops is largely dependent on the environment for any given crop year. Relative differences in grain yield, WUEg, WUEb, and net returns varied by year. Net returns over the three year study were maximized by conventional, cluster, and clump planted sorghum as well as clump planted corn.

Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol) / Small ruminants found in pastoral dryland systems face many challenges regarding constant environmental and climate changes. These variable environments are home to many pastoralists who use the natural resources to sustain their livestock. Due to the prevailing environmental changes, these pastoralists require various adaptation strategies for the survival of their small ruminants. Adaptation is vital for all pastoralists globally, especially those living in semi-arid to arid regions as these areas are badly impacted by climate change. Farming with small ruminants that are able to constantly adapt to variable environments are a long-term and low cost resource strategy for farmers in these areas. Drought is a recurring challenge that farmers in dryland systems have to cope with and small ruminants are forced to adapt to food and water available to them as drought affects their survival, reproduction and production. This is because drought affects the environment directly as rainfall has an impact on all forage and water resources found in drylands. Thus available forage and the utilisation of this resource by small ruminants is essential for sheep and goat farmers who depend on these animals for their livelihoods. This thesis sets out to establish sheep and goat breeds found in a dryland pastoral system in South Africa focussing on their genetic differences and their diet selection during a drought period. The study was carried out in the 582 634 ha Steinkopf communal area located in the semi-arid to arid region of Namaqualand in South Africa. The dominant land use in this area is livestock farming where farmers utilise two biomes for grazing. Using mitochondrial DNA, genetic differences were investigated in small ruminants found in Steinkopf. The small ruminants that were studied were the Boer goats, Swakara sheep (Karakul) and cross-bred sheep. These were the most commonly farmed small ruminants in this area. Genetic differences and diversity found within the small ruminants in this area supports their ability to adapt to drought and changing environments. Diet selection of these small ruminants were assessed using direct forage observation during this drought period in both the Succulent and Nama Karoo biomes. Findings of the study indicate that small ruminants during a drought period will largely forage on what is available to them. Boer goats changed their diets from browser to grazers in the different biomes while sheep remained grazers in both biomes. This suggests that these animals are well adapted to changing forage availability and will adjust their feeding behaviours accordingly. Succulent plant species were utilised by all small ruminants and this can be regarded as new knowledge for small ruminants in dryland systems. Succulent species play a role in the diets of small ruminants in the Steinkopf rangeland and these animals have adapted traits that allow them to eat plants that contain high levels of phenolics and tannins, which show their high adaptability to this area. This study also revealed that indigenous and locally bred sheep in this area are crucial resources for livestock farming in this area. Swakara sheep in this area showed a low level of genetic variation while cross-bred sheep and the Boer goat had significant variation. With a long tradition of breeding small ruminants in the Steinkopf communal area that suit changing conditions, livestock keepers have accumulated detailed knowledge of their animals. Recommendations from this study were to do further studies regarding genetic variation within the cross-bred sheep as this information will be useful for breeding programs in dryland areas and it will add to the small ruminant genetics in South Africa. Because this study was conducted in a drought period, I recommend that diet selection should be observed during a regular wet and dry period as this would indicate how these animals adapt to what forage is available to them. These studies can act as management strategies for herders as it can provide information on how to use the natural resources sustainably.

Since the earliest explorations of the Colorado Plateau, geologists have suspected that cliffs are retreating back laterally. Clarence Dutton envisioned “the beds thus dissolving edge wise until after the lapse of millions of centuries their terminal cliffs stand a hundred miles or more back from their original position” when he wrote about the landscape in 1882. While many geologic studies have determined how fast rivers cut down through the Plateau, only a few studies have calculated how quickly cliffs retreat laterally, and geologists have been arguing since the 1940’s what exactly drives cliffs to retreat in the first place. We study the Book Cliffs in central Utah, and in particular remnant landforms and deposits related to a 120,000-year history of erosion and deposition, which we date by optically stimulated luminescence methods. Our dataset shows that deposits along the Book Cliffs are preserved especially during times of climate instability, which suggests that escarpment retreat locally is driven by climatic disturbances. This disproves older hypotheses suggesting escarpments retreat in response to local factors regardless of shifts in climate, and it is consistent with the few other well-studied escarpment records globally. We also constrain the rates of cliff retreat via a new measurement approach and luminescence age control, showing that the Book Cliffs have retreated at 1-3 meters per thousand years while local toeslope drainages have incised at about 0.5 meters per thousand years, which confirms that cliffs of shallow-dipping, layered rock retreat laterally faster than streams lower the landscape vertically.

Thesis (M.Dev.) --University of Limpopo, 2011 / Food security in most drought-stricken areas of Limpopo Province is a challenge to the Department of Agriculture and to all the people living in the province, especially to the resource poor smallholder farmers. Finding remedial solutions to agricultural production in stress prone conditions is therefore a high priority. The introduction of Challenge Programme Water for Food (CPWF) technologies/techniques to smallholder dry land farming in Greater Giyani Municipality was seen as one of the solutions. However, there are constraints raised by CPWF technology adopters such as shortage of labour, lack of ploughing equipment, lack of credit, shortage of land and marketing. CPWF technologies are suitable for smallholder dry land farming, especially rainwater harvesting technologies. Smallholder farmers need to be remobilised and trained on the potential benefits of CPWF technologies to enhance their adoption and spread to other areas.

Drylands occupy about one-third of the world's land surface area and rivers in these regions have less predictable flow regimes than those in humid tropical and temperate regions. Australia's dryland river-floodplain systems cycle through recurrent periods of floods and droughts, oflen resulting in extreme hydrological variability. As a result, these systems have been described as having a 'boom and boost' ecology with periods of high productivity associated with flooding. Not surprisingly, flow and its variability have been recognised as major driving forces in the ecological functioning of Australian rivers and responses to flow variability from fish and aquatic invertebrates have been reasonably well described. Furthermore, the reduced amount of water reaching floodplain waterbodies due to river regulation has been held responsible for successional changes in aquatic biota and, consequently, the resources available for both fish and invertebrates. However, information regarding the impacts of water resource development has generally focused on within-channel processes of Australian rivers, not on floodplains, which are arguably more affected by water development. The following dissertation is concerned with how different types of natural and modified floodplain lagoons are able to trophically support their fish communities in the floodplain of the Macintyre River, Border Rivers catchment (QLD/NSW), a regulated dryland river. This study focuses on the influence of flooding and the implications of an extended dry period, and different levels of flow regulation, on the feeding ecology of selected fish species (Ambassis agassizil, Lelopotherapon unicolor and Nematalosa erebi) between 2001 and 2003. Food resources consumed by fish are hypothesised to vary in response to flooding, when inundation of isolated lagoons and vast floodplain areas can result in a burst of primary and secondary productivity. Given the permanently elevated water levels of some regulated floodplain lagoons, fish diets are hypothesised to be less variable in these floodplain habitats in comparison to diets of fish from floodplain lagoons with natural flow and water regime. Feeding ecology is examined firstly, in terms of diet composition of selected fish species, using stomach content analysis, and secondly, in relation to possible energy sources sustaining fish (using stable isotope analysis) in selected floodplain lagoons and a site in the main channel of the Macintyre River. The information produced should allow managers to take variations in food resources, food web structure and dietary ecology into account in management regimes for refugia and dryland systems in general. Factors such as diel and ontogenetic variations in dietary composition and food intake by fish are shown to considerably affect ovemll dietary patterns of each study species. Therefore, it is important to understand the contributions of such factors to the variability of fish dietary patterns before performing studies on resource use by fish in floodplain habitats of the Macintyre River. Major food categories consumed by the study species were zooplankton, aquatic invertebrates and detrital material. Zooplankton was of particular importance as this food item was ingested by all three study species at some stage of their life history. Spatial and temporal variation in diet composition of the study species was mostly associated with changes in prey items available across floodplain habitats and between seasons (summer/winter). The low magnitude of flooding events during the study period is arguably the most likely factor influencing the lack of patterns of variation in fish diets in floodplain habitats subject to flooding, whereas in non-flooded lagoons the observed dietary variation was a consequence of successional changes in composition of the aquatic fauna as the dry season progressed. Water regime had an important effect on differences in fish diet composition across lagoons, but further evaluation of the influence of flooding is needed due to overall lack of major flooding events during the study period. Autochthonous resources, namely plankton, were the basis of the food web and phytoplankton in the seston is the most likely ultimate energy source for fish consumers, via planktonic suspension feeders (zooplankton). Nevertheless, organic mailer could not be disregarded as an important energy source for invertebrates and higher consumers. In general, the present study does not provide support for the major models predicting the ftinctioning of large rivers, such as the River Continuum Concept and Flood Pulse Concept, which argue that allochthonous organic matter either from upstream or from the floodplain are the most important sources of carbon supporting higher consumers. In contrast, the Riverine Productivity Model would be more appropriate to describe the food web and energy sources for consumers in the Macintyre River floodplain as this model suggests that local productivity, based on autochthonous phytoplankton and organic matter, ftiels food webs in large rivers. The results of this study suggest that factors known to affect phytoplankton production in floodplain lagoons (e.g. flow regulation, turbidity and nutrient/herbicide inputs) must be seriously considered in current landscape and water management practices.

Soil microorganisms are important for the stabilization and preservation of a good soil structure. Management practices can affect the diversity and population of microorganisms, which could beneficially change soil properties and promote a more sustainable dryland system. This study was established near Pontotoc, MS on Atwood silt loam to evaluate the impacts of cover crops and fertilizer sources on selected biologically related soil properties in a no-tillage, dryland soybean system. Soil analyses included total carbon and nitrogen, permanganate oxidizable carbon (POXC), easily extractable glomalin-related soil protein (EE-GRSP), water stable aggregate (WSA) and soil pH. Cover crop biomass and percent groundcover, soybean leaf area index (LAI), plant height, and yield were also determined. Results indicated that fertilizer source did have an impact on total nitrogen, EE-GRSP and soybean yield. A positive impact on soil properties is expected with the use of cover crops if studied for a longer period of time.

This dissertation investigated the practicality and expediency of applying remote sensing data fusion products to the analysis of dryland vegetation phenology. The objective of the first study was to verify the quality of the output products of the spatial and temporal adaptive reflectance fusion method (STARFM) over the dryland Arizona study site. Synthetic 30 m resolution images were generated from Landsat-5 Thematic Mapper (TM) data and a range of 500 m Moderate Resolution Imaging Spectroradiometer (MODIS) surface reflectance datasets and assessed via correlation analysis with temporally coincident Landsat-5 imagery. The accuracy of the results (0.61 < R2 < 0.94) justified subsequent use of STARFM data in this environment, particularly when the imagery were generated from Nadir Bi-directional Reflectance Factor (BRDF)-Adjusted Reflectance (NBAR) MODIS datasets. The primary objective of the second study was to assess whether synthetic Landsat data could contribute meaningful information to the phenological analyses of a range of dryland vegetation classes. Start-of-season (SOS) and date of peak greenness phenology metrics were calculated for each STARFM and MODIS pixel on the basis of enhanced vegetation index (EVI) and normalized difference vegetation index (NDVI) time series over a single growing season. The variability of each metric was calculated for all STARFM pixels within 500 m MODIS extents. Colorado Plateau Pinyon Juniper displayed high amounts of temporal and spatial variability that justified the use of STARFM data, while the benefit to the remaining classes depended on the specific vegetation index and phenology metric. The third study expanded the STARFM time series to five years (2005-2009) to examine the influence of site characteristics and climatic conditions on dryland ponderosa pine (Pinus ponderosa) forest phenological patterns. The results showed that elevation and slope controlled the variability of peak timing across years, with lower elevations and shallower slopes linked to higher levels of variability. During drought conditions, the number of site variables that controlled the timing and variability of vegetation peak increased. / Ph. D.