Thesis (Ph. D.)--University of California, Davis and San Diego State University, 2005. / Includes bibliographical references. Also available via the World Wide Web. (Restricted to UC campuses)

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Norma Fowler. Vita. Includes bibliographical references.

Not available / text

No description available.

Maritime forests are a critical interface between ocean and terrestrial ecosystems, providing important ecosystem services and functions. Along the U.S. southern Atlantic coast, maritime forests are dominated by <i>Quercus virginiana</i>. Maritime forests and <i>Q. virginiana</i> have been heavily impacted by conversion to agriculture, residential development, and pine stands. Southern pine beetle outbreaks have led to salvage and thinning silvicultural treatments of pine stands which offer an opportunity to restore more complex maritime forests. This research project is comprised of two experiments which allowed me to study the performance of planted <i>Q. virginiana</i> seedlings in response to (1) animal browse, (2) competing vegetation, and (3) varying overstory pine canopies. For both experiments, one-year-old bareroot seedlings were planted as split-plot experimental designs. The first experiment evaluated control of deer browse (fenced and not fenced whole plots) and competing vegetation (0, 1, and 2-yr vegetation control subplots) as independent variables. Overall seedling survival was 60% after two years. There was a significant interaction between deer browse and competing vegetation for seedling height, diameter, crown width, and lateral branches. Seedlings were larger for all response parameters when fenced with vegetation control. Vegetation control significantly improved seedling performance only in fenced plots, indicating a shift in pressure from herbivory to competition when deer were excluded. Foliar nitrogen (N) was significantly greater in fenced plots than non-fenced plots and in 2-yr vegetation control subplots than non-weeded subplots. The second experiment evaluated varying pine overstories (clearcut, heavy thin, light thin, and no thin whole plots) and competing vegetation control (0 and 2-yr vegetation control subplots). Overall seedling survival was 78% after one growing season, with clearcut plots at the greatest survival (83%) and no thin at the lowest (72%). Seedling growth and foliar nitrogen were significantly greater in clearcut plots followed by the heavy thin, light thin, and no thin plots. Vegetation control consistently promoted seedling height, but was only beneficial to diameter and crown width in clearcut/heavy thin plots. <i>Q. virginiana</i> seedlings demonstrated plasticity in their ability to acclimate to the varying microclimates created by silvicultural treatments, as demonstrated by light response curves, stomatal density, and specific leaf area. These results highlight the importance of fencing to remove deer browse, introducing light in the understory, and further improving seedling performance by removing competing vegetation.

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 164-198). Available also in a digital version from Dissertation Abstracts.

No description available.

Trees provide numerous benefits crucial to urban environments, yet poor growing conditions often prevent trees from reaching their genetic potential for growth, longevity, and ecosystem function. To overcome these limitations, greater understanding of tree growth in the urban environment is needed. The goal of this research project was therefore to characterize a broad suite of soil characteristics associated with urban tree plantings and evaluate their suitability for modeling physical dimensions and growth rates of urban trees. A series of observational studies and experiments was conducted on urban soils inhabited by two tree species (Zelkova serrata (Thunb.) Mikano and Quercus phellos L.) in Washington, DC and one tree species (Quercus virginiana Mill.) in Jacksonville, FL – two major metropolitan areas of the eastern United States with contrasting climate and soils. Characterization of urban soil attributes within cities revealed low variability for some properties (soil texture, pH, and certain plant nutrients with coefficients of variation (CV) below 0.5), but high variability (CV>1.0) for others (nitrate, ammonium, copper, and zinc). This is dependent on the location. These findings suggest that tree planting site evaluations may not require measurements for all soil properties and that representative sampling may be sufficient to accurately characterize most soil properties within a city. Field assessment of urban tree soils also revealed that conventional measures of soil compaction are difficult to obtain due to obstructions by roots and other foreign objects. To address the critical need for efficient and reliable assessment of soil compaction around urban trees, an experiment was conducted to develop bulk density estimation models for four common soil texture classes using soil strength and soil moisture as predictor variables. These models provided medium (0.42) to high (0.85) coefficients of determination when volumetric water content (VWC) was log transformed, demonstrating that measurements of soil texture, strength, and moisture can provide rapid, reliable assessment of soil compaction. Tree growth modeling focused on three response variables: canopy projection (CP), canopy volume (CV), and peak-increment-area age (PIA). To calculate PIA, tree-ring analysis was used to determine the age at which maximal trunk diameter growth occurred between transplanting and time of sampling. Because Q. virginiana has difficult-to-distinguish growth rings, an intensive tree-ring analysis of cores collected from these trees was conducted. The analysis revealed interseries correlation coefficients of up to 0.66, demonstrating that Q. virginiana can be aged with fairly high confidence in an urban setting. Empirical models developed for all three tree species using the suite of soil and site variables explained 25% – 83% of the observed variability in tree physical dimensions and growth rates. Soil pH was found to be a significant predictor variable for the majority of growth models along with nutrients such as Fe, B, Mn, and Zn, which are also associated with soil alkalinity. Models for PIA possessed the highest coefficient of determination, suggesting that measurements of soil conditions can be used confidently to predict the age at which growth rate subsides in these species. CV and CP were not predicted as well by soil-related variables, presumably because above-ground constraints such as pruning and building encroachment can affect canopy size without necessarily affecting growth rate. Certain prediction models for all three species included predictor variables with counterintuitive influences on tree growth (e.g., negative influences of soil depth on Q. phellos and soil volume on Q. virginiana), suggesting that either these urban trees are responding to these variables in a novel manner or that variables unaccounted for in these models (perhaps related to urbanization or high vehicular traffic) are concomitantly influencing tree growth. / Ph. D.

La seconde crise de Berlin (1958-1961) est un évènement majeur de la guerre froide. L'hypothèse de notre recherche remet en question le rôle du Canada et les perceptions négatives de l'Occident envers l'URSS durant cette crise. La recherche se divise en trois volets : premièrement, une revue de l'historiographie de la politique canadienne; deuxièmement, une présentation de la chronologie des évènements de la crise de Berlin, l'importance de la diplomatie multilatérale canadienne et la politique nucléaire de Diefenbaker; enfin, un examen de la politique étrangère soviétique. À partir de sources primaires et d'un bilan historiographique,il fut démontré que, durant la crise de Berlin, le Canada a réussi à influencer l'OTAN et à ménager les gouvernements américains et soviétiques. Quant à l'URSS, contrairement à l'image négative que l'Occident en avait, celle-ci a manifesté durant cette crise des intentions pacifiques envers l'Occident, contredisant les interprétations orthodoxes de la guerre froide. / The second Berlin crisis(1958-1961)is a major event of the Cold War. The hypothesis of our research revises the role of Canada and the negative perception of the occidental countries toward USSR during this crisis. This study is divided in three parts : firstly, a historiographical review of the canadian policy toward NATO; secondly, a presentation of the events in regard to the implication of the canadian governement during the Berlin crisis, the importance of the the multilateral canadian diplomacy and the nuclear policy during the Diefenbaker's governement; at last, an examination of the soviet foreign policy. With the help of canadian primary sources, it will be demonstrated firstly that : while the tensions are to their peaks, Canada succeeded to influence NATO and american policy and tried to spare both soviet and american governements. Secondly, soviet and east-german archives showed that the soviet governement manifested during this crisis his pacific intentions, contradicting the most often supported orthodox interpretation of the Cold War.

La seconde crise de Berlin (1958-1961) est un évènement majeur de la guerre froide. L'hypothèse de notre recherche remet en question le rôle du Canada et les perceptions négatives de l'Occident envers l'URSS durant cette crise. La recherche se divise en trois volets : premièrement, une revue de l'historiographie de la politique canadienne; deuxièmement, une présentation de la chronologie des évènements de la crise de Berlin, l'importance de la diplomatie multilatérale canadienne et la politique nucléaire de Diefenbaker; enfin, un examen de la politique étrangère soviétique. À partir de sources primaires et d'un bilan historiographique,il fut démontré que, durant la crise de Berlin, le Canada a réussi à influencer l'OTAN et à ménager les gouvernements américains et soviétiques. Quant à l'URSS, contrairement à l'image négative que l'Occident en avait, celle-ci a manifesté durant cette crise des intentions pacifiques envers l'Occident, contredisant les interprétations orthodoxes de la guerre froide. / The second Berlin crisis(1958-1961)is a major event of the Cold War. The hypothesis of our research revises the role of Canada and the negative perception of the occidental countries toward USSR during this crisis. This study is divided in three parts : firstly, a historiographical review of the canadian policy toward NATO; secondly, a presentation of the events in regard to the implication of the canadian governement during the Berlin crisis, the importance of the the multilateral canadian diplomacy and the nuclear policy during the Diefenbaker's governement; at last, an examination of the soviet foreign policy. With the help of canadian primary sources, it will be demonstrated firstly that : while the tensions are to their peaks, Canada succeeded to influence NATO and american policy and tried to spare both soviet and american governements. Secondly, soviet and east-german archives showed that the soviet governement manifested during this crisis his pacific intentions, contradicting the most often supported orthodox interpretation of the Cold War.