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Long-term tree-ring series of Cedrus atlantica have been utilized to reconstruct and characterize past drought occurrences in Morocco. Based on the close relationship between tree growth and rainfall variations, the best tree-ring indicator of drought has been found to be, x₀ = μ -.75σ, with μ and σ the mean and standard deviation of the tree-ring series. In Morocco, drought is a short event lasting 1.7 years on average with 84% of the events lasting less than 2 years. The average maximum duration exceeds 4 years. It is associated with a 40% deficit about normal moisture availability which can add up to more than 125% when the anomalies persist. The average empirical recurrence interval of drought is 8 years. Long-term persistence has been characterized by the Hurst coefficient. Over the domain of study, the mean Hurst coefficient is .765. The tree-ring series show a periodic behavior with two major peaks at 22 and 66 years. Drought characteristics have been extended from the tree-ring sites to other regions such as the agricultural plains using geostatistical methods. The drought prone areas are located in central Morocco, including the Sais, the Gharb and central Middle Atlas, which experience longer, more severe and more persistent droughts. The northern latitudes experience milder and shorter drought events. The cost for spatial extension of the results was greater kriging errors which make the estimates less reliable. However, cokriging significantly improved the reliability and the quality of the estimates. A regionalization, using cluster analysis, was found to follow the natural climatic and orographic zones of north central Morocco. The tree-ring data were used to reconstruct spatial patterns of moisture anomalies for the period 1845-1974. Three atmospheric factors appear to be important: (1) the relative strength and position of the Azores High, (2) the importance and location of the local cyclogenesis centers, (3) the importance of the northeastern perturbations coming from the Mediterranean sea. The periods 1860-1890, 1925-1950 and the 1970's are associated with dry anomalies while the periods 1900-1920 and 1950-1970 are associated with wet anomalies. They exhibit a rhythmic succession with a 20-year periodicity.

This dissertation makes valuable contributions to hazard and disaster vulnerability assessment theory and methodology. Appendix A presents results of a national survey of state drought planning processes that examined and evaluated how state processes were assessing drought impacts and vulnerabilities, and how assessments were used to mitigate risk. While impact and vulnerability assessments have been useful for reactive, short-term mitigation, most were found to have not been used to develop pro-active and/or committed, long-term mitigation programs. To be useful for developing long-term planning and mitigation, assessments must involve more social scientists, a greater emphasis on second-, third-, etc., order impacts, and examining how systems are sensitive to drought exposure, and studying adaptive capacity. Appendix B adapts a political economy/human ecology and political ecology research framework and examines how regional historical, institutional and regional development patterns in central Arizona have contributed to the production of local drought vulnerability in rural Arizona during the 20th century. The study evaluates the applicability of a research framework developed in Third World settings, and resulted in valuable insights for developing state and county policy in Arizona to mitigate social, economic, and political-institutional drivers of drought vulnerability. Appendix C compliments the assessment in Appendix B by examining local drivers of drought vulnerability and conducting a comparative drought vulnerability analysis in two rural communities in northern Gila County, Arizona. The assessment found local differences in community water system vulnerabilities were driven by differences in capacity to adapt to climate variability and population growth. Differences in adaptive capacity, in turn, were driven by differences in local management, institutional factors, and economic incentives of private and public water systems. Together, the three appendices contribute practical and theoretical contributions for assessments conducted by state and local governments, non-governmental organizations, and academic research units that seek to assess and ultimately mitigate hazard and disaster vulnerability.

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Fungal endophytes can improve plant tolerance to abiotic stresses such as heat and drought. I hypothesized that the six endophytic fungi SMCD 2204, 2206, 2208, 2210, 2214 and 2215 would promote heat and drought tolerance in wheat during both seed germination and at later developmental stages. The Vujanovic and Germida laboratories originally discovered these fungi from the roots of Saskatchewan grown wheat (Triticum turgidum L.). I assessed mycomediated enhancement of seed germination (mycovitality) including seedling performance, in vitro in terms of percent germination, seedling fresh weight, energy of germination (EG) and hydrothermal time (HTT) of germination. Endophytes SMCD 2206, 2210 and 2215 improved seedling heat or drought resistance, while SMCD 2204, 2208 and 2214 did not. In the greenhouse and phytotron, I evaluated the ability of the same six endophytes to enhance wheat tolerance for heat or drought stress by measuring photosynthetic stress (PS), carbon isotopic discrimination (∆), average seed weight (ASW), total seed weight (TSW) and the EG and percent germination of the F1 seeds produced. SMCD 2206, 2201 and 2215 increased performance of pot-grown wheat under heat and drought. Epigenetic modifications frequently involve changes in DNA methylation. Methyl-sensitive amplified polymorphism (MSAP) revealed that drought stressed wheat seedlings colonized with SMCD 2206 had DNA methylation patterns more similar to those of unstressed plants (with or without the endophyte) than to uncolonized drought stressed plants. Plant DNA sequences – similar to a cytochrome p450 EST and three transposable elements (TEs) – were differentially methylated between endophyte-free and endophyte colonized drought stressed plants. I tested the hypothesis that the endophyte-free progeny of SMCD 2206 colonized wheat grown in the phytotron or greenhouse under heat or drought stress would have heightened resistance for the same abiotic stressors to which their parents were exposed, compared to uninoculated first generation plants. Data on PS, ASW, TSW and ∆ showed that F2 plants incompletely inherited stress tolerance. This research demonstrated that fungal endophytes SMCD 2206, 2210 and 2215 improve wheat tolerance for heat and drought both in vitro and in pot studies. If field trials produce similar results, these isolates could be agriculturally important.