Bauxite mining is a major activity in the jarrah (Eucalyptus marginata Donn ex Sm.) forest of south-western Australia. After mining, poor tree growth can occur in some areas. This thesis aimed to determine whether soil constraints, including reduced depth and compaction, were responsible for poor tree growth at low-quality restored bauxite mines. In particular, this study determined the response of jarrah root morphology, leaf-scale physiology and growth/development to soil constraints at two contrasting (low-quality and high-quality) restored bauxite-mine sites. Jarrah root excavations at a low-quality restored site revealed that deep-ripping equipment failed to penetrate the cemented lateritic subsoil, causing coarse roots to be restricted to the top 0.5 m of the soil profile, resulting in fewer and smaller jarrah trees. An adjacent area within the same mine pit (high-quality site) had a kaolinitic clay subsoil, which coarse roots were able to penetrate to the average ripping depth of 1.5 m. Impenetrable subsoil prevented development of taproots at the low-quality site, with trees instead producing multiple lateral and sinker roots. Trees in riplines, made by deep-ripping, at the high-quality site accessed the subsoil via a major taproot, while those on crests developed large lateral and sinker roots. Bauxite mining is a major activity in the jarrah (Eucalyptus marginata Donn ex Sm.) forest of south-western Australia. After mining, poor tree growth can occur in some areas. This thesis aimed to determine whether soil constraints, including reduced depth and compaction, were responsible for poor tree growth at low-quality restored bauxite mines. In particular, this study determined the response of jarrah root morphology, leaf-scale physiology and growth/development to soil constraints at two contrasting (low-quality and high-quality) restored bauxite-mine sites. Jarrah root excavations at a low-quality restored site revealed that deep-ripping equipment failed to penetrate the cemented lateritic subsoil, causing coarse roots to be restricted to the top 0.5 m of the soil profile, resulting in fewer and smaller jarrah trees. An adjacent area within the same mine pit (high-quality site) had a kaolinitic clay subsoil, which coarse roots were able to penetrate to the average ripping depth of 1.5 m. Impenetrable subsoil prevented development of taproots at the low-quality site, with trees instead producing multiple lateral and sinker roots. Trees in riplines, made by deep-ripping, at the high-quality site accessed the subsoil via a major taproot, while those on crests developed large lateral and sinker roots.

Recurring drought conditions have always been an endemic feature of climate in South Africa, limiting maize development and production. However, recent projections of the future climate by the Intergovernmental Panel on Climate Change suggest that due to an increase of atmospheric greenhouse gases, the frequency and severity of droughts will increase in drought-prone areas, mostly in subtropical climates. This has raised major concern for the agricultural sector, particularly the vulnerable small-scale farmers who merely rely on rain for crop production. Farmers in the Luvuvhu River catchment are not an exception, as this area is considered economically poor, whereby a significant number of people are dependent on rain-fed farming for subsistence. This study was therefore conducted in order to improve agricultural productivity in the area and thus help in the development of measures to secure livelihoods of those vulnerable small-scale farmers. Two drought indices viz. Standardized Precipitation Evapotranspiration Index (SPEI) and Water Requirement Satisfaction Index (WRSI) were used to quantify drought. A 120-day maturing maize crop was considered and three consecutive planting dates were staggered based on the average start of the rainy season. Frequencies and probabilities during each growing stage of maize were calculated based on the results of the two indices. Temporal variations of drought severity from 1975 to 2015 were evaluated and trends were analyzed using the non-parametric Spearman’s Rank Correlation test at α (0.05) significance level. For assessing climate change impact on droughts, SPEI and WRSI were computed using an output from downscaled projections of CSIRO Mark3.5 under the SRES A2 emission scenario for the period 1980/81 – 2099/100. The frequency of drought was calculated and the difference of SPEI and WRSI means between future climate periods and the base period were assessed using the independent t-test at α (0.10) significance level in STATISTICA software. The study revealed that planting a 120-day maturing maize crop in December would pose a high risk of frequent severe-extreme droughts during the flowering to the grain-filling stage at Levubu, Lwamondo, Thohoyandou, and Tshiombo; while planting in October could place crops at a lower risk of reduced yield and even total crop failure. In contrast, stations located in the low-lying plains of the catchment (Punda Maria, Sigonde, and Pafuri) were exposed to frequent moderate droughts following planting in October, with favorable conditions noted following the December planting date. Further analysis on the performance of the crop under various drought conditions revealed that WRSI values corresponding to more intense drought conditions were detected during the December planting date for all stations. Moreover, at Punda Maria, Sigonde and Pafuri, it was observed that extreme drought (WRSI <50) occurred once in five seasons, regardless of the planting date. Temporal analysis on historical droughts in the area indicated that there had been eight agricultural seasons subjected to extreme widespread droughts resulting in total crop failure i.e. 1983/84, 1988/89, 1991/92, 1993/94, 2001/02, 2002/03, 2004/05 and 2014/15. Results of Spearman’s rank correlation test revealed weak increasing drought trends at Thohoyandou (ρ = of 0.5 for WRSI) and at Levubu and Lwamondo (ρ = of 0.4 for SPEI), with no significant trends at the other stations. The study further revealed that climate change would enhance the severity of drought across the catchment. This was statistically significant (at 10% significance level) for the near-future and intermediate-future climates, relative to the base period. Drought remains a threat to rain-fed maize production in the Luvuvhu River catchment area of South Africa. In order to mitigate the possible effects of droughts under climate change, optimal planting dates were recommended for each region. The use of seasonal forecasts during drought seasons would also be useful for local rain-fed maize growers especially in regions where moisture is available for a short period during the growing season. It was further recommended that the Government ensure proper support such as effective early warning systems and inputs to the farmers. Moreover, essential communication between scientists, decision makers, and the farmers can help in planning and decision making ahead of and during the occurrence of droughts. / Agriculture, Animal Health and Human Ecology / M. Sc. (Agriculture)

Several studies indicates China is experiencing a water crisis, were several regions are suffering of severe water scarcity and rivers are heavily polluted. On the other hand, water is used inefficiently and wastefully: water use efficiency in the agriculture sector is only 40% and within industry, only 40% of the industrial wastewater is recycled. However, based on statistical data, China’s total water resources is ranked sixth in the world, based on its water resources and yet, Yellow River and Hai River dries up in its estuary every year. In some regions, the water situation is exacerbated by the fact that rivers’ water is heavily polluted with a large amount of untreated wastewater, discharged into the rivers and deteriorating the water quality. Several regions’ groundwater is overexploited due to human activities demand, which is not met by local. Some provinces have over withdrawn groundwater, which has caused ground subsidence and increased soil salinity. So what is the situation in China? Is there a water crisis, and if so, what are the causes?This report is a review of several global water scarcity assessment methods and summarizes the findings of the results of China’s water resources to get a better understanding about the water situation. All of the methods indicated that water scarcity is mainly concentrated to north China due to rapid growth, overexploitation from rivers and reduced precipitation. Whereas, South China is indicated as abundant in water resources, however, parts of the region are experiencing water scarcity due to massive dam constructions for water storage and power production. Too many dam constructions in a river disrupts flow of the river water and pollutants are then accumulated within floodgates.Many Chinese officials and scholars believe that with economic growth comes improved environmental quality when the economy has reached to a certain of per-capita level. However, with the present water situation it is not sustainable or possible for China to keep consuming and polluting its water resources. Improvement of environmental quality does not come automatically with increased income, and policies, laws and regulations are needed in order to stop further deterioration of the environment.China’s water situation is not any news and the key factor is human activities, but the question is how to solve it. China’s water crisis is much more complex than over exploitation of groundwater and surface water. There are three water issues in China: “too much water – floods, too little water – droughts, and too dirty water – water pollution” (Jun &amp; Chen, 2001). Thus, solving China’s water crisis is a huge challenge to solve without negatively affecting the economic growth.

From the Proceedings of the 1974 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 19-20, 1974, Flagstaff, Arizona / A progressive and coordinated effort is underway to provide a sound technical basis for managing water resources on forest and rangelands in the Southwest. An in-house Forest Service (USDA) research program including pilot testing and economic evaluations of multiple-use alternatives provides information necessary for this purpose. Demands for other goods and services also are increasing on these lands in the face of a burgeoning population. homeseekers, vacationers, and recreationists seek a variety of recreational. experiences that require open space and a relatively undisturbed environment. Frequently these uses conflict, and the combined pressure from too many activities can damage the environment. A new research effort has been organized in the central and southern Rocky Mountain Region to cope with these problems. Nine Western universities including Northern Arizona University, Arizona State University, and University of Arizona have joined forces with the Rocky Mountain Forest and Range Experiment Station to form the Eisenhower Consortium for Western Environmental Forestry Research. Simply stated, the consortium seeks to better our understanding of the relationships between man and his open-space environment in order that its quality might be maintained.

From the Proceedings of the 1974 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 19-20, 1974, Flagstaff, Arizona / Two native grass species, blue grama and sidecoats, were successfully seeded on a semiarid rangeland on the walnut gulch experimental watershed in southeastern Arizona. Optimum seeding dates selected were those within the time period most likely to receive precipitation, and grass stands were established in two successive years with average rainfall. Shrubs were killed by root-plowing at a depth of 14 inches, a procedure which was more than 95% successful in controlling sprouting shrubs. Forage production measurements taken on nm-28 sideoats and Vaughn sideoats showed a yield of 1,950 and 2,643 pounds of forage per acre, respectively, for the 2 years following the seeding, whereas untreated sites produced 23 and 25 pounds per acre of forage. Results indicate that success in establishing a stand of native grass is increased through use of existing hydrologic data.

From the Proceedings of the 1974 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 19-20, 1974, Flagstaff, Arizona / An examination of potential water sources for power plant cooling in Arizona is presented along with information pertinent to Arizona's future water needs relative to electrical usage growth. It has been projected that Arizona's peak electrical power demands in 1980 and 1990 will exceed that of 1970 by some 5000 megawatts and 16000 megawatts of electricity respectively. At present, the bulk of the electrical energy generated in the western states originates at hydroelectric installations. Utilization of nuclear reactors for power generation requires a larger amount of cooling water than is required for a comparable fossil-fueled plant. It is suggested that the utilization of reclaimed wastewater for cooling purposes is a viable and attractive alternative to groundwater pumpage from both economic and ecological standpoints. Savings arise from conservation of fuel normally required for well pumps, costs of well construction are not required, quantities of fresh water should be released for consumption by alternate users, and a previously unused resource would be effectively recycled.

Local maize landraces have evolved over hundreds of years of natural and farmer selection under varying conditions. These landraces may have developed tolerance to abiotic stresses such as water deficits during this cycle of selection. However, despite its continued existence and importance, little is known on their agronomy and responses to water stress. If indeed landraces have developed tolerance to water stress, they may prove a key genetic resource for future crop improvement in light of increasing water scarcity. The primary objective of this study was to evaluate the responses of a local maize landrace to water stress at different stages of growth in comparison to two known commercial hybrids, SC701 and SR52. Seed from a local maize landrace was multiplied and characterised according to kernel colour. Two distinct colours were selected for the purposes of this study, white (Land A) and dark red (Land B). In a holistic approach, the thesis consisted of four separate studies whose overall objective was to evaluate the responses of the maize landraces to water stress at different growth stages, up to and including yield and its components. These comprised three controlled environment studies (25°C; 60% RH) and a field trial. For the controlled environment, two water regimes were used, 25% field capacity (FC) (stress treatment) and 75% FC (non-stress). The first study investigated the effect of water stress on early establishment performance. Seed quality was evaluated using the standard germination test together with electrolyte leakage. Catalase activity and accumulation of proline were examined as seedling physiological response to water stress. The second study was conducted as a pot trial to investigate the effect of water stress on growth, photosynthesis and yield. Photosynthesis was measured as chlorophyll fluorescence (CF). In addition, a field study over three planting dates was conducted at Ukulinga Research Farm in Pietermaritzburg, under dryland conditions, during the period from August 2008 to June 2009. The objective was to evaluate the effect of planting dates and changing soil water content on growth, yield and yield components. Three planting dates were used, representative of early (28 August 2008), optimum (21 October 2008) and late planting (9 January 2009). Lastly, a study on hydro-priming was conducted, necessitated by observations made primarily in the first study. The study was carried out under controlled environment conditions. The objective was to evaluate whether hydropriming can improve germination, vigour and emergence under water stress. Seeds were soaked in water for 0 hours (Un-primed or control), 12 hours (P12) and 24 hours (P24). Results from the first study showed that maize landraces were slower to germinate and emerge, and produced less vigorous seedlings compared to the hybrids. The study showed that hybrids were more superior under optimum (75% FC) conditions than under stress conditions (25% FC). Physiological showed that both hybrids and landraces expressed catalase under water stress, with landraces showing slightly better expression compared to the hybrids. Proline accumulation was observed in both hybrids and landraces as a response to water stress, with hybrids being more sensitive to water stress. In the pot trial, results showed that the vegetative stage of both hybrids and landraces was less sensitive to water stress than the reproductive stage. Results showed no differences between field capacities, with respect to emergence, mean emergence time, leaf number, CF, ear prolificacy and ear length. Photosynthesis, as measured by CF, was shown to be desiccation tolerant. Water stress had a negative effect on cob mass, lines per cob, grains per cob and total grain mass, and resulted in barrenness in the landraces. The hybrids had superior yield compared to the landraces. Results for the field trials showed that planting date had highly significant effects on emergence, plant height, leaf number and days to tasseling (DTT). Landraces emerged better than hybrids in all plantings; highest emergence was in the early and late plantings. Optimum and late planting resulted in maximum plant height and leaf number, respectively, compared to early planting. Hybrids were superior, growing taller and with more leaves than landraces in all plantings. DTT decreased with successive plantings. Planting date had an effect on ear prolificacy (EP), kernels/ear (KNE) and 100 grain mass. Planting date had no effect on ear length and mass, kernel rows/cob, grain mass and yield. With the exception of EP, hybrids out-yielded the landraces in all three planting dates. Hydro-priming landraces for 12 hours and 24 hours, respectively, improved germination velocity index, reduced mean germination time and improved emergence and mean emergence time of maize landraces under water stress. Performance of hybrid seeds remained superior to that of landraces even after seed treatment to improve germination and vigour. Landraces were slower to germinate and emerge and produced less vigorous seedlings in controlled conditions only. Both hybrids and landraces expressed catalase activity and also accumulated proline in response to water stress, although hybrids were more sensitive to stress in the establishment phase. Results confirmed literature, showing that, for both hybrids and landraces, the vegetative stage is less sensitive to stress than the reproductive stage. Hybrids produced superior yields compared to landraces in both controlled environment and field conditions. However, the pattern of seedling establishment observed in the initial controlled environment study for hybrids and landraces was reversed in the field study. Lastly, hydro-priming is of some benefit to maize establishment. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

As is the case in many other regions in the world, sugarcane production in southern Africa is affected by a wide range of climatic conditions, which can vary considerably from location to location and from year to year. As a result, the season length and growth cycles of sugarcane in southern Africa differ greatly. Such conditions include the hot and dry regions of northern KwaZulu-Natal, Swaziland and Mpumalanga, where sugarcane is mostly irrigated, to the humid sub-tropical coastal belt extending from the far north coast of KwaZulu-Natal to areas in the Eastern Cape, as well as the cool frost prone midlands regions of KwaZulu-Natal. Owing to the wide range of climatic conditions in which sugarcane is grown in southern Africa, there are many different external factors that affect sugarcane production, including a range of pests and diseases, frost occurrences and variations in soil water. The objective of this research was to (1) identify a number of important variables that affect cane production in southern Africa, (2) employ suitable models to reflect these variables, and (3) simulate and map the extent and severity of these variables at a high spatial resolution over southern Africa. Such variables include the Eldana saccharina and Chilo sacchariphagus stalk borers, sugarcane rust fungus, heat units with selected base temperatures, frost, soil water content, soil compaction, irrigation water demand, conducive and non-conducive growing conditions, flowering proficiencies for sugarcane, sugarcane yields and yield increments per unit of irrigation. The distribution patterns of the above-mentioned variables relied greatly upon the various models employed to represent them, as well as the accuracy of the temperature and rainfall databases to which the various models were applied. Although not definitive, the models used to reflect the variables which had been identified were considered to be generally satisfactory. The resolution at which the variables which had been identified in this study were mapped, was also found to be adequate. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

[Truncated abstract] Establishment of vegetation and ecosystem functioning is central to the mitigation of environmental impacts associated with mining operations. This study investigated the ecophysiological functioning of mature plants in natural vegetation and applied this knowledge to diagnose problems affecting plant health and causes of poor plant cover at a mine-rehabilitation site. Ecophysiological parameters, including plant water relations and mineral nutrition, were studied in conjunction with soil physical, hydraulic and chemical properties. The natural ecosystem at the study location in the Great Sandy Desert is characterised by sand dunes and interdunes with distinct plant communities on each. One of the most notable features of the vegetation is the presence of large Corymbia chippendalei trees high on the dunes and relatively small scattered shrubs in the interdunes. Triodia grasses (spinifex), dominate the vegetation in both habitats but different species occur in each; T. schinzii is restricted entirely to the dunes, and T. basedowii occurs only in the interdunes. It was hypothesised that the deep sandy dunes afford greater water availability but lower nutrient supply to plants in this habitat compared with those occurring in the lower landscape position of the interdunes. Water-relations parameters (leaf water potentials, stomatal conductance, d13C) revealed that dune plants, particularly woody species, displayed higher water status and water use than closely related and often congeneric plants in the interdunes. Nutrient concentrations in soils were significantly higher in the interdunes, but concentrations in foliage were similar for related species between habitats. It is concluded that the dunes provide a greater store of accessible water than the soil profile in the interdunes. ... Following an experimental wetting pulse equivalent to a summer cyclone event, A. ancistrocarpa plants displayed significant increases in stomatal conductance, leaf water potential and sap velocity in lateral roots within three days of irrigation at the natural site and two days at the rehabilitation site. Secondary sinker roots originating from distal sections of lateral roots were evidently supplying water to maintain hydraulic function in laterals, thus enabling a fast pulse response. This was accentuated at the rehabilitation site where roots were confined closer to the surface. These results indicate that plants at the rehabilitation site are more dependent on small pulses of water and have less access to deep reserves than plants at the natural site. It is concluded that high runoff losses and insufficient soil depth are major factors contributing to plant water stress, and combined with the direct impacts of erosion, are largely responsible for plant death and ultimately poor plant cover. These issues can be alleviated if cover soil depth is increased to more than 0.5 m and slope angles are reduced to <12o. This study demonstrates the value of an ecophysiological approach for diagnosing problems affecting plant establishment at mine-rehabilitation sites. Furthermore, it has provided recommendations that will improve the rehabilitation strategy and lead to the development of a well vegetated, resilient ecosystem on a stable and non-polluting land form.

[Truncated abstract. Please see the pdf format for the complete text. Also, formulae and special characters can only be approximated here. Please see the pdf version for an accurate reproduction.] This thesis examines the water use, ecophysiology and hydraulic architecture of Eucalyptus marginata (jarrah) growing on bauxite mine rehabilitation sites in the jarrah forest of south-western Australia. The principal objective was to characterise the key environment and plant-based influences on tree water use, and to better understand the dynamics of water use over a range of spatial and temporal scales in this drought-prone ecosystem. A novel sap flow measurement system (based on the use of the heat pulse method) was developed so that a large number of trees could be monitored concurrently in the field. A validation experiment using potted jarrah saplings showed that rates of sap flow (transpiration) obtained using this system agreed with those obtained gravimetrically. Notably, diurnal patterns of transpiration were measured accurately and with precision using the newly developed heat ratio method. Field studies showed that water stress and water use by jarrah saplings on rehabilitation sites were strongly seasonal: being greatest in summer when it was warm and dry, and least in winter when it was cool and wet. At different times, water use was influenced by soil water availability, vapour pressure deficit (VPD) and plant hydraulic conductance. In some areas, there was evidence of a rapid decline in transpiration in response to dry soil conditions. At the end of summer, most saplings on rehabilitation sites were not water stressed, whereas water status in the forest was poor for small saplings but improved with increasing size. It has been recognised that mature jarrah trees avoid drought by having deep root systems, however, it appears that saplings on rehabilitation sites may have not yet developed functional deep roots, and as such, they may be heavily reliant on moisture stored in surface soil horizons. Simple predictive models of tree water use revealed that stand water use was 74 % of annual rainfall at a high density (leaf area index, LAI = 3.1), high rainfall (1200 mm yr-1) site, and 12 % of rainfall at a low density (LAI = 0.4), low rainfall (600 mm yr-1) site, and that water use increased with stand growth. A controlled field experiment confirmed that: (1) sapling transpiration was restricted as root-zone water availability declined, irrespective of VPD; (2) transpiration was correlated with VPD when water was abundant; and (3) transpiration was limited by soil-to-leaf hydraulic conductance when water was abundant and VPD was high (> 2 kPa). Specifically, transpiration was regulated by stomatal conductance. Large stomatal apertures could sustain high transpiration rates, but stomata were sensitive to hydraulic perturbations caused by soil water deficits and/or high evaporative demand. No other physiological mechanisms conferred immediate resistance to drought. Empirical observations were agreeably linked with a current theory suggesting that stomata regulate transpiration and plant water potential in order to prevent hydraulic dysfunction following a reduction in soil-to-leaf hydraulic conductance. Moreover, it was clear that plant hydraulic capacity determined the pattern and extent of stomatal regulation. Differences in hydraulic capacity across a gradient in water availability were a reflection of differences in root-to-leaf hydraulic conductance, and were possibly related to differences in xylem structure. Saplings on rehabilitation sites had greater hydraulic conductance (by 50 %) and greater leaf-specific rates of transpiration at the high rainfall site (1.5 kg m-2 day1) than at the low rainfall site (0.8 kg m-2 day1) under near optimal conditions. Also, rehabilitation-grown saplings had significantly greater leaf area, leaf area to sapwood area ratios and hydraulic conductance (by 30-50 %) compared to forest-grown saplings, a strong indication that soils in rehabilitation sites contained more water than soils in the forest. Results suggested that: (1) the hydraulic structure and function of saplings growing under the same climatic conditions was determined by soil water availability; (2) drought reduced stomatal conductance and transpiration by reducing whole-tree hydraulic conductance; and (3) saplings growing on open rehabilitation sites utilised more abundant water, light and nutrients than saplings growing in the forest understorey. These findings support a paradigm that trees evolve hydraulic equipment and physiological characteristics suited to the most efficient use of water from a particular spatial and temporal niche in the soil environment.