<p> An open Quercus-dominated vegetation association, known locally as the oak plains, was found at a number of locations in southern Ontario until disturbance by European settlers in the late 18th and early 19th centuries. Two contrasting theories have been suggested in the literature regarding the origin of the oak plains. One suggests they developed as the result of burning by pre-European natives, while the other considers them to be relics of a warmer, drier mid-Holocene climate. In this paper, the factors which led to the development of the oak plains are examined. The hypothesis that the oak plains resulted from native burning of the natural vegetation was tested by pollen analysis of a 5 m sediment core from Decoy Lake, a small kettle basin near Paris, Ontario located in an area mapped by early surveyors as oak plains. The Decoy Lake record was then compared to those of two nearby lakes supporting mesic forests. This palaeoecological analysis was supported by an investigation of physical factors controlling the historical distribution of the oak plains in a study area between Cambridge and Long Point on Lake Erie. </p> <p> The distribution of the oak plains and other vegetation associations in pre-settlement times, reconstructed from early survey records, correlated fairly well with the texture of soils and underlying Quaternary parent materials. Within the defined study area, the oak plains were restricted almost exclusively to well-drained soils overlying coarse-textured till and sandy outwash and deltaic deposits. Climatic factors and topography varied within the study area, but showed little correlation with the distribution of vegetation associations. <p> <p> The fossil pollen record at Decoy Lake indicates that a QuercusPinus- herb pollen assemblage, unique to southern Ontario, was found from 4000 yr BP until pre-settlement times. This suggests that the oak plains have existed in the area for at least 4000 years. The oak plains replaced an assemblage dominated by Pinus strobus. The warm, dry Hypsithermal appears to have allowed Pinus strobus to remain dominant on the well drained soils around Decoy Lake until after 5000 yr BP, 2000 to 3000 years longer than at other southern Ontario sites. The Picea zone (11,800 yr BP to 10,100 yr B P), Pin us banksiana/resinosa zone ( 10,100 yr BP to c. 9000 yr BP), and the replacement of Pinus banksiana/resinosa by Pinus strobus (c. 9000 yr BP) occurred contemporaneously with other records from southern Ontario. </p> <p> The hypothesis that anthropogenic factors resulted in the development of the oak plains was rejected since this association developed 2500 years before the onset of agricultural activity by natives in southern Ontario. Instead, it appears post-Hypsithermal increases in moisture, perhaps coupled with an amelioration of winter temperatures, led to the replacement of Pinus strobus by the oak plains in some areas of well-drained soils between 6300 yr BP and 4000 yr BP. The pollen record from Decoy Lake provides the first evidence from southern Ontario for substantial vegetation response to mid to late Holocene climatic change. </p> / Thesis / Master of Science (MSc)

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Temperate deciduous forests of eastern North America are undergoing a long-term compositional shift from oak/hickory-dominated forests to maple/birch-dominated forests, resulting in decreased species diversity and more homogeneous understory communities. This shift is likely due to secondary regrowth after extensive logging and intensive fire suppression efforts that together allowed shade-tolerant but fire-intolerant species to flourish. Managers have more recently sought to use forest management practices to counteract this shift. Our aim in this study was to improve understanding of how prescribed burning and mechanical tree thinning shape forest communities and the extent to which they favor declining species and communities of temperate eastern deciduous forest. We conducted our study at Fort Indiantown Gap National Guard Training Center in south-central Pennsylvania. Prescribed burning and mechanical thinning have been conducted onsite since 2003. Forestry plots were surveyed in 2003 just prior to management implementation and again about ten years after intensive management began, during 2013-2014. The data collected at forestry plots, including number of stems, tree diameter at breast height, management activities undertaken at the plot, and other environmental characteristics were analyzed using model selection and generalized linear mixed models. A broader community analysis was then conducted using non-metric multidimensional scaling and permutational multivariate analysis of variance (PERMANOVA) analyses. Specifically, we analyzed tree species persistence, changes in tree basal area, changes in the abundance of tree stems, and changes in the the distribution of basal area and stems within 16 tree species targeted for management and throughout the forest community as a whole following management action. Burning and thinning both had significant effects on tree species persistence, basal area, and stem abundance. The interaction of the two management techniques was rarely significant, but since thinning and burning affected different species of trees, the two management practices were complementary. At a whole community level, management by both burning and thinning shifted the forest composition back toward an oak/hickory-dominated forest, and without such management the shift to a maple/birch-dominated forest is likely to continue. / Biology

Ellagitannins are plant phenolics characterized by biaryl-coupled gallic acid moieties esterified to a D-glucose core. They are widely distributed through higher plants. In the case of oaks, ellagitannin concentrations in heartwood can reach up to 10% (dry wt. basis). These secondary metabolites are not only important physiologically but also influence the economic value and quality of wood products that contain them. Efforts were made to develop and validate the methods used to quantify both soluble and insoluble ellagitannins. First, the efficiencies of the two commonly used extraction solvents, aqueous acetone and aqueous methanol were evaluated. The results showed that aqueous acetone is superior to aqueous methanol in obtaining higher vescalagin and castalagin yields. In a separate study, the method used for determining insoluble ellagitannins was found to under-estimate the contents of insoluble ellagitannins in wood products. Anhydrous methanolic HCl was found to be an excellent reagent for releasing insoluble ellagic acid and gallic acid (as methyl gallate) from biomass substrates. Optimization of both the reaction conditions and the gradient HPLC analysis has led to the development of a robust and reliable protocol. The chemical stability of the two predominant ellagitannins in oaks (vescalagin and castalagin) were evaluated in aqueous methanol and water. It was found that oxygen, pH and higher temperature (60 °C) affect their stability with higher temperature being the most prominent factor. Both vescalagin and castalagin were found unstable in methanolic solutions. Vestalagin, however, is less stable than castalagin. In the course of finding alternative models for ellagitannin biosynthesis study, both callus tissues and suspension cell cultures of white oak (Quercus alba) and sweetgum (Liquidambar styraciflua) were investigated for their possible use as models for ellagitannin biosynthesis. It was found that oak callus tissue cultures (Quercus alba) are capable of producing ellagitannins, and the production and profile of ellagitannins can be modified by adjusting the media composition. Comparison of extracts from the heartwood of Quercus alba with those from callus tissue reveals that they have similar ellagitannin profiles. Through manipulation of the media nitrogen and copper concentrations the callus tissue produced almost 3 times as much castalagin and vescalagin. Suspension cells of Quercus alba and Liquidambar styraciflua were found to be unsuitable for the study of biosynthesis of ellagitannins. These cells either did not produce any detectable level of ellagitannins or the production was unstable. Although the suspension cells could be elicited to produce ellagic acid with glycanases (Driselase), the levels of ellagic acid were too low for quantitative metabolic studies. A method using high performance liquid chromatography – mass spectrometry was developed and optimized with purified ellagitannins. Ellagitannins analyzed under the optimal conditions all provide base peaks of (M-H)- from which the molecular weights of the ellagitannins can be determined. Mild fragmentation was also achieved to give fragments characteristic of ellagitannins (loss of ellagic acid and gallic acid if present). These characteristic peaks allow for rapid identification of ellagitannins from other secondary metabolites present in the samples. Application of the HPLC/ESI-MS in the identification of monomeric ellagitannins in white oak heartwood extracts revealed that it can unambiguously identify the two monomeric ellagitannins, castalagin and vescalagin, and their degradation product, ellagic acid. The key fragmentation pathways of the ellagitannins are also described. Finally, preliminary work using proteomics to study the heartwood formation was conducted. Proteins from transition zone and sapwood were determined and resolved with two-dimensional electrophoresis. It was found that both sapwood and transition woods contain active enzyme(s) capable of catalyzing formation of ellagic acid from pentagalloylglucose. Preliminary results from the 2-D gel separation of sapwood and transition wood proteins showed more protein spots in sapwood than in transition wood, suggesting that sapwood not only had higher protein levels but also a great total number of proteins. The lower complexity of the transition wood proteome suggests that this material may be a good substrate for studying the biaryl-coupling process. / Ph. D.

Northern red oak (Q. rubra L.) seeds were dormant and required 10 weeks of moist, cold stratification before a large percentage of the seeds would germinate. White oak (Q. alba L.) seeds were not dormant and germinated immediately upon falling from the mother tree. A transfer of mass from the cotyledons to the embryos occurred during germination of red and white oak seeds. No detectable transfer of mass occurred during stratification of the red oak seeds. The longer the red oak seeds were kept under stratification conditions, the shorter the period of time required for seeds at 26°C to begin germination. A significant decrease in GA-like activity occurred during the first 5 weeks of stratification of red oak seeds. No transfer of activity from one pH-dependent ethyl acetate-soluble fraction to another occurred. A slight increase in GA-like activity occurred between 5 'and 7-1/2 weeks of stratification. Red oak seeds stratified for 18 weeks contained significantly more GA-like activity than those receiving lesser periods of stratification. When l8-week stratified red oak seeds were warmed to 26°C, germination commenced within 2 days and the levels of GA-like activity decreased. White oak seeds contained substantially less GA-like activity than red oak seeds and amounts of activity in white oak seeds changed little during cold storage of the seeds. Radicle extension growth of white oak seeds began even at 5°C and complete seed germination began within 2 days of warming to 26°C, independent of the time in cold storage. Cytokinin activity was measured in the ethyl acetate and n-butanol fractions of red oak seeds. Concentrations did not change between 0 and 5 weeks of stratification. / Ph. D.