Thesis (M.S. - Renewable Natural Resources)--University of Arizona,1987. / Includes bibliographical references (leaves 87-95).

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This study investigated effects of plant quality and natural enemies on the abundance and survivorship of several leaf miner species on Florida scrub oaks over several ecological scales. Three oak species (Quercus laevis, Q. geminata, and Q. myrtifolia) and four leafminer species (Acrocercops albinatella, Brachys tesselatus, Stilbosis quadripustulatus, and Cameraria sp. nova) were the main focus of five separate studies, addressing effects of bottom-up and top-down factors at regional, local, and individual scales. At the regional scale, it was observed that Cameraria sp. nova was aggregated into sites, and sites closer to each other exhibited similar densities of mines than sites farther apart. None of the bottom-up and top-down factors studied were spatially structured, but did influence the variation in Cameraria abundance over the range of the host plant Q. myrtifolia. At the local scale, all leaf miners studied were aggregated between and within plants, and variation in bottom-up factors among individual plants explained variation in abundance for some of the leaf miners studied. Intra-specific competition was identified as an important factor influencing mine survivorship, but inter-specific competition among leaf miners and gall-formers did not shape the community structure of oak herbivores. Experimental manipulation of bottom-up and top-down factors via fertilization and natural enemy removal showed that bottom-up effects were important determinants of leaf miner abundance, as fertilized plants supported 2 to 5-fold more herbivores than control plants. The removal of natural enemies, on the other hand, did not significantly impact the abundance and/or the survivorship of leaf miners and other guilds studied. At individual scales, it was demonstrated that two leaf miner species responded to random variations in leaf morphology, by increasing in abundance in individual host plants with more asymmetric leaves and/or higher levels of fluctuating as ymmetry. These results offered support for the plant stress hypothesis and differences in host plant quality were again partially responsible for the results found.

The occurrence and concentration of substances like glycosides, alkaloids, certain amino acids, and, especially, phenolics in vegetation has been seen as a defense against environmental perturbations. Whether this phenomenon is associated with the disruptive effect of man, herbivore predation or the invasion of arthropods and microorganisms remains to be ascertained by ecologists. However, contemporary research shows that most so-called secondary metabolites in plants render them less sensitive to adverse factors in the natural environment. Likewise, herbivores that adapted to chemical defense in plants were rewarded with wider food source and might have been able to more efficiently exploit rapidly changing foraging environments. This study focuses on relationships between goats, their ruminal microbes and tannin-rich plants in a central Arizona chaparral vegetation type dominated by shrub live oak (Quercus turbinella). The study tested hypotheses involving goat dietary selection, estimated through microhistological analysis of feces; phenolic profile of shrub live oak, expressed as condensed and hydrolyzable tannins, protein binding capacity of oak leaves extract, expressed as bovine serum albumin (BSA) precipitation; and apparent dry matter digestibility of mature and immature oak leaves by goat ruminal microbes measured at 6, 12, 24 and 48 hours. Findings of this research indicated that goats prefer leaf and shoot ends of shrubs, mainly shrub live oak, despite the constant high concentration of tannins in that plant. Hydrolyzable tannins in oak are synthesized during summer/fall and late spring, and the synthesis of condensed tannins is mostly restricted to winter and early spring. Precipitation of BSA by extract of oak leaves, apparently associated with hydrolyzable tannins, did not discourage oak consumption by goats. The digestibility of younger and older oak leaves was more influenced by time of incubation than level of phenolics in plant tissue. This research emphasizes the adaptability of goats to ecological zones where presence of toxins and digestion reducing compounds in plants adversely affects survival and fitness of non-adapted herbivores.

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Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Tüpfel ermöglichen den interzellularen Stoffaustausch im Holzkörper. Im Zuge der Prozessgestaltung in den Bereichen Holzschutz und Zellstoffherstellung sind genauere Kenntnisse über ihren Aufbau von grundlegender Bedeutung. Das anatomische Wissen ermöglicht eine verbesserte Einschätzung der Tränkbarkeit sowie allgemein über die Eindringwege von Flüssigkeiten im Holz. Die Arbeit fasst den aktuellen Wissensstand des Baus der Tüpfel im Laubholz zusammen. Dabei stehen die in Deutschland wichtigsten Laubbaumarten, namentlich die Rot-Buche (Fagus silvatica L.) und Stiel- sowie Traubeneiche (Quercus robur L. und Quercus petraea Liebl.), im Fokus der Untersuchung. Zunächst wird der allgemeine Aufbau der Tüpfel beschrieben und besonders neuere Erkenntnisse mit aufgegriffen. Im Anschluss wird der Wissensstand zur Tüpfelbau der Rot-Buche sowie der Stiel- wie Trauben-Eiche zusammengefasst dargestellt.

Master of Science / Department of Horticulture and Natural Resources / Jason Griffin / Chad T. Miller / Oak trees (Quercus L.) and river birch (Betula nigra L.) are two horticulturally significant crops widely used in landscapes but notorious for developing iron (Fe) induced interveinal foliar chlorosis (IFC) in alkaline soils. Variation in IFC has been observed between species of oak and provenances of river birch suggesting that species and provenances endemic to alkaline soils do not always display this chlorosis. Limited studies investigating the effect of elevated pH on oak and river birch have been conducted. More environmentally tolerant and aesthetically pleasing selections could be used if they are first screened to determine their adaptability to high pH soils. Three experiments were conducted to evaluate Texas red oak (Quercus buckleyi Nixon and Dorr) and Durand oak [Quercus sinuata Walter var. breviloba (Torr.) C.H. Mull.] with landscape collections of pin oak (Quercus palustris L.) to determine the extent of IFC when grown at elevated pH. When grown in an elevated pH substrate, pin oak was unable to maintain elevated leaf total leaf Fe concentrations, consistently developed IFC, and exhibited low total leaf chlorophyll concentrations compared to non-chlorotic pin oak seedlings in the control pH substrate. Texas red oak and Durand in the elevated substrate did not develop IFC and maintained high leaf chlorophyll concentrations compared to controls; they also sequestered greater amounts of substrate Fe in leaves compared to pin oak in the elevated substrates. Another crop of ornamental significance and widely planted in the landscape, river birch (Betula nigra L.), develops IFC in high pH soils. Two experiments evaluated river open- pollinated (OP) seedlings of Iowa provenances, OP ‘BNMTF, and clones from selected Iowa provenances, ‘BNMTF’, ‘Cully’ in an elevated pH substrate. A seed source from Bearbower Sand Prairie, Buchanan Co., IA (BSP3) had greater leaf chlorophyll than ‘BNMTF’OP, and a clone from Clemons Creek WMA, Washington Co., IA (CCWMA3) than the trade standard ‘Cully’. Although differences in total leaf chlorophyll were observed, all sources in elevated pH substrate did not sequester sufficient amounts of leaf Fe compared to their controls. Field evaluations with considerations of provenance performance in different hardiness zones should be used to determine the potential of these Iowa sources as more suitable selections for use in landscapes with alkaline soils.

Wasting and death of deciduous trees, including oaks, is among the most serious problems today. Since 2003, the decline of oak trees in the Czech republic, among others, has been associated with the pathogenic fungus Phytophtora plurivora causing serious damage to root systems, which can lead to insufficient transport of water to transpiring leaves. The thesis is partly built on my Bachelor's thesis and includes two experiments. The objective of the first experiment,based on anatomical investigations, was to determine a theoretical maximum flow of water in the sapwood in oak seedlings. The goal of the second experiment,based on the temperature of the leaves, was to find out the functionality of the root system infected by the fungus Phytophthora plurivora. If the root system works, the transpiration is not disrupted and the leaf is cooler. The results of the first experiment give us evidence that the seedlings infected by the fungus Phytophthora plurivora are of the lower hydraulic conductivity and the lower theoretical maximum flow of water in the sapwood. The oak seedlings inoculated by the fungus Phytophthora plurivora compared with the control seedlings had smaller area of the vessels lumina, maximum theoretical flow of water in the sapwood, theoretical hydraulic conductivity, number of the vessel elements, maximum and minimum diameter of the vessel elements. In contrast, the inoculated seedlings had greater specific hydraulic conductivity and specific flow of water in the sapwood. The disruption of the root system by the fungus Phytophthora was demonstrated by 1°C higher temperature in the inoculated seedlings leaves.