Master of Science / Department of Agronomy / John P. Fellers / Allan K. Fritz / Water availability is commonly the most limiting factor to crop production, especially in drought prone areas like the Midwest. This study was conducted to map quantitative trait loci (QTL) involved in drought tolerance in wheat (Triticum aestivum L.) to enable their use for marker assisted selection (MAS) in breeding. A population of 122 F[subscript]7 derived recombinant inbred lines from a cross between Dharwar Dry and Sitta, spring wheat lines with contrasting drought tolerances, was analyzed using the amplified fragment length polymorphism (AFLP) technique and Diversity Array Technology (DArT) markers to create a QTL map. Of the 256 AFLP primer combinations evaluated, 151 were found to be polymorphic between the parents and were used to screen the population. A linkage map of 48 groups was created from the combined DArT markers, AFLP data, and SSR markers. This was used to create a QTL map which identified QTL in 24 of these groups. Using these markers for MAS in a breeding program could overcome the difficulties of selecting for drought tolerance. Another serious limitation to wheat production is leaf rust caused by the pathogen Puccinia triticina. Leaf rust causes between 1% and 20% yield loss on average and tends to be the worst in years with high yield potential. PI 289824 contains a single, dominant gene for seedling resistance mapping to chromosome 5BS and thought to be different from Lr52. An F[subscript]2 mapping population from a cross between PI 289824 and Jagger was used to try to identify markers very closely linked to the gene and therefore useful for MAS. The population presented some mapping challenges, but with the use of SSR and EST-STS markers, the gene was flanked. However, the markers were at too a great distance to be useful for mapping.

6 pp. / Remotely sensed data are valuable for monitoring, assessing, and managing impacts to arid and semi-arid lands caused by drought or other changes in the natural environment. With this in mind, we collaborated with scientists and technologists to redevelop DroughtView, a web-based decision-support tool that combines satellite-derived measures of surface greenness with additional geospatial data so that users can visualize and evaluate vegetation dynamics across space and over time. To date, users of DroughtView have been local drought impact groups, ranchers, federal and state land management staff, environmental scientists, and plant geographers. Potential new applications may include helping to track wildland fire danger. Here, we present the functionality of DroughtView, including new capabilities to report drought impacts and share map information, as well as the data behind it.

Linking annual tree growth with remotely-sensed terrestrial vegetation indices provides a basis for using tree rings as proxies for ecosystem primary productivity over large spatial and long temporal scales. In contrast with most previous tree ring/remote sensing studies that have focused on temperature-limited boreal and taiga environments, here we compare the normalized difference vegetation index (NDVI) with a network of Pinus brutia tree ring width chronologies collected along ecological gradients in semiarid Cyprus, where both radial tree growth and broader vegetation activity are controlled by drought. We find that the interaction between precipitation, elevation, and land-cover type generate a relationship between radial tree growth and NDVI. While tree ring chronologies at higher-elevation forested sites do not exhibit climatedriven linkages with NDVI, chronologies at lower-elevation dry sites are strongly correlated with NDVI during the winter precipitation season. At lower-elevation sites, land cover is dominated by grasslands and shrublands and tree ring widths operate as a proxy for ecosystem-scale vegetation activity. Tree rings can therefore be used to reconstruct productivity in water-limited grasslands and shrublands, where future drought stress is expected to alter the global carbon cycle, biodiversity, and ecosystem functioning in the 21st century.

>Magister Scientiae - MSc / Sugargraze is a moderately drought tolerant sweet sorghum hybrid which is ideal for grazing, winter stand over and pit silage. A major advantage that Sugargraze has over other forages is its very high sugar content which improves feed quality thus increasing palatability and results in significantly reduced feed wastage. This study explored the influence of hyperosmotic stress on plant development, ROS accumulation, antioxidant capacity and the extent of cell death. Heat shock protein (Hsp70) expression immunoblotting assays were used to demonstrate whether the various treatment conditions induced stress within natural physiological parameters for the experimental material. This was coupled with the separation, visualization and identification of abundant proteins in Sugargraze leaves in response to hyperosmotic stress using two-dimensional gel electrophoresis (2-DE) in combination with mass spectrometry (MS). The results showed that hyperosmotic stress significantly influences plant development by reducing plant biomass and increasing the levels of ROS accumulation, proline content and subsequently reducing total chlorophyll content. An over accumulation of ROS in the form of hydrogen peroxide and lipid peroxidation was observed in the stressed plants which was supported by the extent of cell death. Although an increase in antioxidant enzyme activity (in the form of total enzymatic activity or individual isoform activity) in response to hyperosmotic stress was observed, this increase was not sufficient to counter the deleterious effects caused by the stress conditions hence the decrease in plant biomass and increase in cell death. Western blotting analysis of Sugargraze leaf tissues using Hsp70 antibodies showed that hyperosmotic stress induced Hsp70 expression to levels significantly higher than observed for the control plants. A total of thirteen CBB stained spots were selected for mass spectrometric identification, owing to their good resolution and abundance levels, and of these, nine were positively identified. Identified proteins were divided into functional categories including both known and novel/putative stress responsive proteins. Molecular and physiological functions of some of the proteins of interest identified will be subjected to further investigation via bioinformatic and molecular biology approaches.

>Magister Scientiae - MSc / This study investigated the effects that drought stress imposed on the growth and development of soybean plants. Soybeans were initially observed at the whole-plant level in order to identify the physical changes that had taken place in response to drought. Further investigation of the effects of drought stress on Soybean plants were quantified at the molecular level. Physical changes of soybeans in response to drought stress were typified by the change in leaf morphology and pigmentation. At the molecular level, it was observed that drought stress resulted in the accumulation of hydrogen peroxide in soybean leaves, which was met by elevated levels of lipid peroxidation. The effects of drought on the modulation of (and interplay between cystatins) cysteine protease (caspase-like) activity and programmed cell death (PCD) were also investigated. Total caspase-like activity and cell death were enhanced in response to water deficit despite the up-regulation in gene expression of the cystatin Glyma14g04250. The cystatin Glyma18g12240 was not expressed in soybean leaves, whilst the gene expression of the cystatin Glyma20g08800 remained unchanged in response to drought. This study was aimed at the characterization of two single domain soybean cystatins, namely, Glyma14g04250 and Glyma20g08800 which could potentially be overexpressed in transgenic soybean plants in an attempt to alleviate the effects of drought stress. / National Research Foundation (NRF)

Germination of plants is one of the most important stages during their growth which is often influenced by environmental stresses, especially drought and salinity. This study was conducted to investigate the effects of salinity and drought on seed germination and growth of Lathyrus sativa. The experiment was laid out in a completely randomized design with factorial arrangement in 4 replications. Salinity treatments were 0, 2, and 4 dS/m and drought treatments included 0, 0.4, 0.8, 1.2 MPa. Salinity and drought treatments were prepared by using sodium chloride and polyethylene glycol 6000, respectively. The results showed that salinity and drought stresses decreased germination percentage, root and radicle length.

Drought is the most costly hazard among all natural disasters. Despite the significant improvements in drought modeling over the last decade, accurate provisions of drought conditions in a timely manner is still one of the major research challenges. In order to improve the current drought monitoring and forecasting skills, this study presents a hybrid system with a combination of remotely sensed data assimilation based on particle filtering and a probabilistic drought forecasting model. Besides the proposed drought monitoring system through land data assimilation, another novel aspect of this dissertation is to seek the use of data assimilation to quantify land initial condition uncertainty rather than relying entirely on the hydrologic model or the land surface model to generate a single deterministic initial condition. Monthly to seasonal drought forecasting products are generated using the updated initial conditions. The computational complexity of the distributed data assimilation system required a modular parallel particle filtering framework which was developed and allowed for a large ensemble size in particle filtering implementation. The application of the proposed system is demonstrated with two case studies at the regional (Columbia River Basin) and the Conterminous United States. Results from both synthetic and real case studies suggest that the land data assimilation system significantly improves drought monitoring and forecasting skills. These results also show how sensitive the seasonal drought forecasting skill is to the initial conditions, which can lead to better facilitation of the state/federal drought preparation and response actions.

Here we analyze climate variability using instrumental, paleoclimate (proxy), and the latest climate model data to understand more about the sources and impacts of low-frequency climate variability. Understanding the drivers of climate variability at interannual to century timescales is important for studies of climate change, including analyses of detection and attribution of climate change impacts. Additionally, correctly modeling the sources and impacts of variability is key to the simulation of abrupt change (Alley et al., 2003) and extended drought (Seager et al., 2005; Pelletier and Turcotte, 1997; Ault et al., 2014). In Appendix A, we employ an Earth system model (GFDL-ESM2M) simulation to study the impacts of a weakening of the Atlantic meridional overturning circulation (AMOC) on the climate of the American Tropics. The AMOC drives some degree of local and global internal low-frequency climate variability (Manabe and Stouffer, 1995; Thornalley et al., 2009) and helps control the position of the tropical rainfall belt (Zhang and Delworth, 2005). We find that a major weakening of the AMOC can cause large-scale temperature, precipitation, and carbon storage changes in Central and South America. Our results suggest that possible future changes in AMOC strength alone will not be sufficient to drive a large-scale dieback of the Amazonian forest, but this key natural ecosystem is sensitive to dry-season length and timing of rainfall (Parsons et al., 2014). In Appendix B, we compare a paleoclimate record of precipitation variability in the Peruvian Amazon to climate model precipitation variability. The paleoclimate (Lake Limón) record indicates that precipitation variability in western Amazonia is ‘red’ (i.e., increasing variability with timescale). By contrast, most state-of-the-art climate models indicate precipitation variability in this region is nearly'‘white' (i.e., equally variability across timescales). This paleo-model disagreement in the overall structure of the variance spectrum has important consequences for the probability of multi-year drought. Our lake record suggests there is a significant background threat of multi-year, and even decade-length, drought in western Amazonia, whereas climate model simulations indicate most droughts likely last no longer than one to three years. These findings suggest climate models may underestimate the future risk of extended drought in this important region. In Appendix C, we expand our analysis of climate variability beyond South America. We use observations, well-constrained tropical paleoclimate, and Earth system model data to examine the overall shape of the climate spectrum across interannual to century frequencies. We find a general agreement among observations and models that temperature variability increases with timescale across most of the globe outside the tropics. However, as compared to paleoclimate records, climate models generate too little low-frequency variability in the tropics (e.g., Laepple and Huybers, 2014). When we compare the shape of the simulated climate spectrum to the spectrum of a simple autoregressive process, we find much of the modeled surface temperature variability in the tropics could be explained by ocean smoothing of weather noise. Importantly, modeled precipitation tends to be similar to white noise across much of the globe. By contrast, paleoclimate records of various types from around the globe indicate that both temperature and precipitation variability should experience much more low-frequency variability than a simple autoregressive or white-noise process. In summary, state-of-the-art climate models generate some degree of dynamically driven low-frequency climate variability, especially at high latitudes. However, the latest climate models, observations, and paleoclimate data provide us with drastically different pictures of the background climate system and its associated risks. This research has important consequences for improving how we simulate climate extremes as we enter a warmer (and often drier) world in the coming centuries; if climate models underestimate low-frequency variability, we will underestimate the risk of future abrupt change and extreme events, such as megadroughts.

By 2050, mean annual temperature on Vancouver Island, British Columbia is expected to rise by 1.5°C and summer precipitation is expected to decrease 14% below pre-industrial levels. The purpose of this thesis was to extend the Sooke Watershed precipitation record by developing proxy records from annual Douglas-fir tree rings, with the goal of being able to provide information about the pre-historical range of precipitation variation that could assist future water management decisions. Robust dendrohydrological relationships were established to extend the instrumental record of precipitation back to the year 1591. To provide geographic context for the hydrologic history of the Sooke Watershed, I examined Douglas-fir climate-radial growth relationships across western Canada to three monthly climate variables: precipitation, average air temperature, and Hargreaves Climatic Moisture Deficit (CMD). Ten study sites were chosen to represent a gradient of climate conditions where Douglas-fir grows in Alberta and British Columbia. In order to explore how growth sensitivities varied over time, long- and short-term climate-growth relationships at these study sites were analyzed and compared to those established for the Sooke Watershed. A short-term analysis of the radial growth of Douglas-fir trees in the Sooke Watershed revealed the presence of a negative climate-growth relationship to the June and July temperature of the growing year starting in 1990. Further, the radial growth of Douglas-fir trees at all sample sites was moisture limited, whereby they exhibited strong positive growing season correlations to precipitation and negative correlations to CMD. Lastly, lagged negative effects of August and September precipitation and CMD were present and related to the annual radial growth increments. These results signify that: the rise in air temperature in recent decades is limiting the radial growth of Douglas- fir trees in the Sooke Watershed; annual variation in ring-width increments is regulated by the amount of precipitation that falls near the end of the prior growing season; and, moisture availability in the spring of the current year of growth plays an important role in determining the annual increment of radial growth. Collectively, the results suggest that the radial growth of Douglas-fir trees within the Sooke Watershed are sensitive to interannual climate fluctuations and future growth is likely to be altered by changes in temperature and precipitation regimes. These climate-growth relationships justified the development of a May-June-July precipitation reconstruction for the Sooke Watershed. Using a novel detrending method, an Ensemble Empirical Mode Decomposition, I created a model that explained 28% of the May-June-July precipitation variability. Results from the dendrohydrological analyses extend the understanding of the water supply area May-June-July precipitation record to 1591. The reconstruction revealed four major summer drought episodes that exceeded severity during the instrumental record severity: 1594-1596, 1662-1665, 1796-1797, and 1898-1899. Four extreme summer pluvial episodes were also observed from 1646-1647, 1689-1690, 1793-1794, and 1920-1921. The findings of the research provide information about historical summer precipitation trends within the Sooke Watershed – the primary water supply area to Greater Victoria. Notably, the research places summer drought and pluvial events recorded within the instrumental record into a much longer context, permitting an understanding of natural frequency and duration of hydrological events in the Sooke Watershed. / Graduate

Drought poses a threat to socio-economic activities across eastern Africa and its river basins. While there are indications that global warming may continue to enhance evaporation and intensify droughts at all scales, most drought projections over eastern Africa are based on rainfall alone and are limited to meteorological droughts. The present study combines rainfall and Potential Evapotranspiration (PET) to examine the characteristics of meteorological and hydrological droughts in present and future climates at the regional and river basin scales. To accomplish that we have applied five objectives; i) Study the temporal and spatial characteristics of eastern Africa droughts modes, ii) Investigate how some atmospheric teleconnections influence the characteristics of the Africa droughts modes, iii) Examine the influence of 1.5°C and 2°C global warming levels on drought modes in eastern Africa under two future climate scenarios, RCP 4.5 and RCP8.5 iv) Assess how increases in global warming will influence drought characteristics over eastern African river basins. v) Examine the potential impacts of climate change and land use change on water availability in the Rufiji River basin (RRB), Tanzania, with an emphasis of hydrological droughts in this basin. Different types of datasets, including gridded and station observation datasets, regional climate model simulations (CORDEX: Coordinated Regional Climate Downscaling Experiment) and hydrological simulations (SWAT: Soil and Water Assessment Tool), were analysed for the study. The meteorological drought were characterised using two indices (i.e. Standardized Precipitation Evapotranspiration Index, SPEI; Standardized Precipitation Index, SPI) at 3- and 12-month scales, while the hydrological droughts were characterised using four indices (i.e. soil water index, SWI; Surface Runoff Index, RFI; Water Yield Index, WYI; and Stream Flow index, SFI). The study combined principal component analysis (PCA) with wavelet analysis to identify the spatio-temporal structure of four dominant drought modes over the region. It also used wavelet coherence to quantify the influence of four atmospheric teleconnections (i.e. El Niño Southern Oscillation, ENSO; Indian Ocean Dipole, IOD; Tropical Atlantic Dipole Index, TADI; and Quasi-Biennial Oscillation, QBO) on the drought modes. The study also projects the characteristics of future droughts over eastern Africa and its major river basins at different global warming levels (GWLs). Series of hydrological simulations were used to assess the sensitivity of future droughts to four land use change scenarios (i.e. increase in forestry, shrubs, cropland and agriculture) over the Rufiji River Basin (RRB), a prominent river basin in eastern Africa. Although eastern Africa have been documented with several drought studies, the application of a combination of PCA, Wavelet analysis, wavelet coherence and Self Organizing Maps provides more comprehensive representation of droughts in the region using SPEI/SPI derived from both models and observations The results of the study show that the four drought modes, which have their core areas over different parts of eastern Africa, account for more than 45% of drought variability in the region. All the drought modes are strongly coupled with either ENSO or IOD indices (or both); but, in addition, one of the modes is also strongly coupled with the TADI. CORDEX models give a realistic simulation of the relevant climate variables for calculating drought indices over eastern Africa and the river basins. However, the ensemble mean struggles to reproduce the spatial distribution and frequency of drought intensity in the region. The CORDEX simulations project no changes in the spatial structure of the drought modes but suggest an increase in SPEI drought intensity and frequency over the hotspots of the drought modes and elsewhere in the region. The magnitude of the increase, which varies over the drought mode hotspots, increases with increasing GWLs. The projections also show that the increase in intensity and frequency of drought can be attributed more to increased PET than to reduced precipitation. In contrast to the SPEI projection, the SPI projection shows a weak change in intensity and frequency of droughts, and the magnitude of the increase does not vary with the GWLs. Over the river basins, the SPEI projections are more robust than the SPI projections. Over the RRB, the future projections of some hydrological drought indices (i.e. RFI and SFI) follow the change in the SPEI projections, while others (i.e. SWI and WYI) follow that of SPI. Among the four land use scenarios considered, only forestry and shrubs show a substantial change in the hydrological drought indices. The results of the study thus give valuable insight into the characteristics of future droughts in eastern Africa and provide a useful guide to the effectiveness of using land cover to reduce the severity of hydrological droughts over river basins in the region. However, resolution of CORDEX dataset (50km, i.e. 0.44deg) could be among the potential limitation as it is too low to capture the influence of local-scale processes (e.g. sea breeze, mountain induced circulations) on drought over the region.