UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item Investigating the hyperdiversity of fungal endophytes in wild Rubiaceae tropical plants and coffee plantations.(2022) Castillo Gonzalez, Humberto; Yarwood, Stephanie A; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Fungal endophytes are an essential component of a plant’s microbiome, their effect spreads to fitness, disease dynamics, stress tolerance, water acquisition and nutrient uptake. Plant ecosystems, from natural forest to plantations bear the indelible signature of its presence. The current investigation was designed to understand the diversity of endophytes in the Rubiaceae family, in plants associated to natural and managed ecosystems. The effect of location, leaf developmental stage, tissue type, host genotype, and anthropogenic interference was evaluated through amplicon sequencing. Costa Rica served as base for the sample collection. Leaves and sapwood from a variety of tropical plant species were collected in old-growth natural forests and foliar tissue from domesticated coffee plants were sampled in two plantations under different management. Fungal diversity was assessed by metabarcoding using the ITS2 nrDNA region fITS7 – ITS4, and library sequencing was completed by Ion Torrent. We identified a hyperdiversity of endophytes inhabiting these plants and were able to isolate a total of 659 fungi from coffee leaves. This investigation provides relevant information about overall community composition, the ecological drivers of community assemblage and the characteristics of the fungal endophytic communities, including potential interactions among the identified taxa. Endophytes may harness the potential to transform agriculture and conservation science, however we currently lack the knowledge to engineer microbial communities through breeding or management. It is essential to continue the efforts on understanding community functions and dynamics, and how host, endophyte interactions, and other ecological and human- related mechanisms influence their diversity in both forest species and agronomically important crops.Item Caffeinated Development and Other Essays in Latin American Economic History(2020) Uribe-Castro, Mateo; Wallis, John J; Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation consists of three essays. The first one focuses on Colombia after 1850 and measures the impact of the expropriation of Church's assets on political violence. With yearly data on the number of battles per municipality, archival information on the reform, and difference-in-differences, the paper documents a reduction of political violence in places where the Church's assets were expropriated. The paper contests the traditional idea of the expropriation of Church's real estate as a source of political violence. It highlights changes in political competition after the alliance between Conservative factions and the Church was weakened. Specifically, it shows the reduction in political violence was concentrated in municipalities with high political competition and where the Conservative Party was relatively weak. The second essay studies the effect of the first wave of globalization on developing countries' structural transformation, using data from Colombia's expansion of coffee cultivation. Counties engaged in coffee cultivation in the 1920s developed a smaller manufacturing sector by 1973 than comparable counties, despite starting at a similar level in 1912. My empirical strategy exploits variation in potential coffee yields, and variations in the probability to grow coffee at different altitudes. This paper argues that coffee cultivation increased the opportunity cost of education, which reduced the supply of skilled workers, and slowed down structural transformation. Using exogenous exposure to coffee price shocks as instrument, I show that reductions in cohorts' educational attainment led to lower manufacturing activity in the long-run. The effect is driven by both a decrease in demand for education and reductions in public goods. Finally, coffee cultivation during the early 20th Century had negative long-run effects on both individual incomes and poverty rates. The third essay explores how changes in commodities’ prices can have differential effects on school enrollment according to characteristics of crop’s production functions. It compares schooling outcomes in counties that specialize in sugar (a land intensive crop with economies of scale) or coffee (mostly produced in small farms) in Puerto Rico between 1900 and 1930. Sugar price increases lead to increases in enrollment in sugar counties, while coffee price changes have a negative relationship with enrollment in coffee regions.