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White Oak (white + oak)
Selected AbstractsPotential Effects of Passenger Pigeon Flocks on the Structure and Composition of Presettlement Forests of Eastern North AmericaCONSERVATION BIOLOGY, Issue 6 2003JOSHUA W. ELLSWORTH We suggest that the activities of roosting and nesting Passenger Pigeons caused widespread, frequent disturbances in presettlement eastern forests through tree limb and stem breakage and nutrient deposition from pigeon excrement. We suspect that the deposition of fine fuels resulting from such disturbances may have influenced fire intensity and frequency in presettlement forests. Further, we propose that consumption of vast quantities of acorns by pigeons during the spring breeding season may partially explain the dominance of white oak (Quercus alba) throughout much of the presettlement north-central hardwoods region. Consequently, the pigeon's extinction may have facilitated the increase and expansion of northern red oak (Quercus rubra) during the twentieth century. Although it is difficult to accurately quantify how physical and chemical disturbances and mast consumption by Passenger Pigeon flocks affected forest ecology, we suspect they shaped landscape structure and species composition in eastern forests prior to the twentieth century. We believe their impact should be accounted for in estimates of the range of natural variability of conditions in eastern hardwood forests. Resumen:,Consideramos los posibles efectos que pudieron haber tenido parvadas de Palomas Migratorias (Ectopistes migratorius) sobre el régimen de perturbación y la composición de especies de bosques en Norte América oriental antes de la colonización. Sugerimos que las actividades de perchado y anidación de las palomas causaron perturbaciones frecuentes y extensas en los bosques orientales antes de la colonización por medio de la ruptura de ramas y tallos de árboles y la deposición de nutrientes del excremento de las palomas. Sospechamos que la deposición de combustibles resultantes de tales perturbaciones pudo haber influido en la intensidad y frecuencia de incendios forestales. Más aún, proponemos que el consumo de grandes cantidades de bellotas por las palomas en la primavera puede parcialmente explicar la dominancia de roble blanco (Quercus alba) en muchos de los bosques nor-orientales. En consecuencia, la extinción de la paloma pudo haber facilitado el incremento y expansión del roble rojo (Quercus rubra) durante el siglo veinte. Aunque es difícil cuantificar con precisión como las perturbaciones físicas y químicas y el consumo masivo por parvadas de palomas migratorias afectaron a la ecología forestal, sospechamos que modelaron la estructura del paisaje y la composición de especies en los bosques orientales antes del siglo veinte. Creemos que su impacto debería ser considerado cuando se hacen estimaciones del rango de variabilidad natural de las condiciones en bosques orientales de maderas duras. [source] Involvement of Phytophthora species in white oak (Quercus alba) decline in southern OhioFOREST PATHOLOGY, Issue 5 2010Y. Balci Summary This study was initiated to investigate the possible role of Phytophthora species in white oak decline (Quercus alba) in southern Ohio at Scioto Trail State Forest. Surveys demonstrated the presence of four species of Phytophthora including one novel species. By far, the most common species was P. cinnamomi; P. citricola and P. cambivora were isolated infrequently. In few instances, P. cinnamomi was isolated from fine roots and necroses on larger roots. No special pattern of incidence was found, but P. cinnamomi was more commonly isolated from greater Integrated Moisture Index values suggesting moist lower bottomlands favour this Phytophthora species. When tree crown condition was examined relative to the presence of Phytophthora, no significant association was found. However, roots of declining P. cinnamomi -infested trees had 2.5 times less fine roots than non-infested and healthy trees, which was significantly different. The population densities of P. cinnamomi from declining trees were significantly greater than from healthy trees, suggesting increased pathogen activity that has the potential to cause dieback and decline and possibly the cause of a reduced fine root amount found on declining trees. [source] The influence of the impregnating chemicals on the bonding strength of impregnated wood materialsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Ayhan Özçifçi Abstract In this study, it is aimed to determine the bonding strength of white oak (Quercus petreae L.) and chestnut (Castanea sativa Mill.) woods impregnated with borax and zinc chloride. Within this purpose, the experimental samples were bonded with Polyvinyl-acetate and polyurethane based Desmodur-VTKA (D-VTKA) adhesives according to BS EN 205 standards after they had been prevacuumed with a pressure equal to 760 mmHg,1 with impregnating at 2 atm pressures for 60 min according to ASTM-D 1413 standards and applied vacuum-impregne-vacuum method. During the experiments, the retention amount, the retention proportion, and the bonding strength values of the samples were determined. According to the test results, the highest values of retention amount, and bonding strength were obtained from the wood material impregnated with zinc chloride. The impregnating materials had a negative effect on bonding strength. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Riparian Forest Restoration: Increasing Success by Reducing Plant Competition and HerbivoryRESTORATION ECOLOGY, Issue 2 2002Bernard W. Sweeney Abstract The reestablishment of riparian forest is often viewed as "best management practice" for restoring stream ecosystems to a quasi-natural state and preventing non-point source contaminants from entering them. We experimentally assessed seedling survivorship and growth of Quercus palustris (pin oak), Q. rubra (red oak), Q. alba (white oak), Betula nigra (river birch), and Acer rubrum (red maple) in response to root-stock type (bare root vs. containerized), herbivore protection (tree shelters), and weed control (herbicide, mowing, tree mats) over a 4-year period at two riparian sites near the Chester River in Maryland, U.S.A. We started with tree-stocking densities of 988/ha (400/ac) in the experimental plots and considered 50% survivorship (i.e., a density of 494/ha [200/ac] at crown closure) to be an "acceptable or minimum" target for riparian restoration. Results after four growing seasons show no significant difference in survivorship and growth between bare-root and containerized seedlings when averaged across all species and treatments. Overall survivorship and growth was significantly higher for sheltered versus unsheltered seedlings (49% and 77.6 cm vs. 12.1% and 3.6 cm, respectively) when averaged across all species and weed control treatments. Each of the five test species exhibited significantly higher 4-year growth with shelter protection when averaged across all other treatments, and all species but river birch had significantly higher survivorship in shelters during the period. Seedlings protected from weeds by herbicide exhibited significantly higher survivorship and growth than seedlings in all other weed-control treatments when averaged across all species and shelter treatments. The highest 4-year levels of survivorship/growth, when averaged across all species, was associated with seedlings protected by shelters and herbicide (88.8%/125.7cm) and by shelters and weed mats (57.5%/73.5 cm). Thus, only plots where seedlings were assisted by a combination of tree shelters and either herbicide or tree mats exhibited an "acceptable or minimum" rate of survivorship (i.e.,>50%) for riparian forest restoration in the region. Moreover, the combined growth and survivorship data suggest that crown closure over most small streams in need of restoration in the region can be achieved most rapidly (i.e., 15 years or less) by protecting seedlings with tree shelters and controlling competing vegetation with herbicides. [source] Hydraulic properties and freezing-induced cavitation in sympatric evergreen and deciduous oaks with contrasting habitatsPLANT CELL & ENVIRONMENT, Issue 12 2001J. Cavender-Bares Abstract We investigated the hydraulic properties in relation to soil moisture, leaf habit, and phylogenetic lineage of 17 species of oaks (Quercus) that occur sympatrically in northern central Florida (USA). Leaf area per shoot increased and Huber values (ratio of sapwood area to leaf area) decreased with increasing soil moisture of species' habitats. As a result, maximum hydraulic conductance and maximum transpiration were positively correlated with mean soil moisture when calculated on a sapwood area basis, but not when calculated on a leaf area basis. This reveals the important role that changes in allometry among closely related species can play in co-ordinating water transport capacity with soil water availability. There were significant differences in specific conductivity between species, but these differences were not explained by leaf habit or by evolutionary lineage. However, white oaks had significantly smaller average vessel diameters than red oaks or live oaks. Due to their lower Huber values, maximum leaf specific conductivity (KL) was higher in evergreen species than in deciduous species and higher in live oaks than in red oaks or white oaks. There were large differences between species and between evolutionary lineages in freeze,thaw-induced embolism. Deciduous species, on average, showed greater vulnerability to freezing than evergreen species. This result is strongly influenced by evolutionary lineage. Specifically, white oaks, which are all deciduous, had significantly higher vulnerability to freezing than live oaks (all evergreen) and red oaks, which include both evergreen and deciduous species. These results highlight the importance of taking evolutionary lineage into account in comparative physiological studies. [source] | ||||||||||