The biochemical anti-herbivore defense of trembling aspen (Populus tremuloides Michx.) was investigated in a molecular analysis of polyphenol oxidase (PPO; EC 1.10.3.2). A PPO cDNA was isolated from a trembling aspen wounded leaf cDNA library and its nucleotide sequence determined. Southern analysis indicated the presence of two PPO genes in the trembling aspen genome. Expression of PPO was fou...

Studies on the durability and dimensional stability of a series of hardwoods and softwoods after thermal modification in vegetable oils and in steam atmospheres have been performed. Mass loss after exposure to Coniophora puteana (BAM Ebw.15) for 16 weeks was very low for European birch, European aspen, Norway spruce, and Scots pine thermally modified in a linseed oil product with preservative (...

Identification of specific genes and enzymes involved in conversion of lignocellulosics from an expanding number of potential feedstocks is of growing interest to bioenergy process development. The basidiomycetous wood decay fungi Phanerochaete chrysosporium and Postia placenta are promising in this regard because they are able to utilize a wide range of simple and complex carbon compounds. How...

Paper birch (Betula papyrifera Marsh.) and three trembling aspen clones (Populus tremuloides Michx.) were studied to determine if alterations in carbon gain in response to an elevated concentration of CO(2) ([CO(2)]) or O(3) ([O(3)]) or a combination of both affected bud size and carbohydrate composition in autumn, and early leaf development in the following spring. The trees were measured for ...

Trembling aspen covers a large geographic range in North America, and previous studies reported that a better understanding of its singular influence on soil properties and processes is of high relevance for global change questions. Here we investigate the potential impact of a shift in aspen abundance on soil carbon sequestration and soil carbon stability at the continental scale by conducting...

Because forest stand structure, age, and productivity can mediate the impacts of climate on quaking aspen (Populus tremuloides) mortality, ignoring stand-scale factors limits inference on the drivers of recent sudden aspen decline. Using the proportion of aspen trees that were dead as an index of recent mortality at 841 forest inventory plots, we examined the relationship of this mortality inde...

The ecosystem consequences of intraspecific genetic variation is an emerging field of research that strengthens the link between population and ecosystem ecology. Despite recent advances, it remains unclear under what conditions (abiotic and biotic) plant genetic variation will be important to belowground processes. Forest canopy herbivores can have large influences on soil processes by alterin...

Belanger, R. R., Falk, S. P., Manion, P. D., and Griffin, D. H. 1989. Tissue culture and leaf spot bioassays as variables in regression models explaining Hypoxylon mammatum incidence on Populus tremuloides clones in the field. Phytopathology 79:318-321. Regression models were used to interpret the relationships among H. mammatum. High positive correlations among bioassays, with various sensitiv...

Conference Reports: Aspen Workshop on Numerical Investigations of Singularities in GR, Susan Scott : : : : 15 Second Annual Penn State Conference: Quantum Geometry, Abhay Ashtekar : : : : : : : 17 First Samos Meeting, Spiros Cotsakis and Dieter Brill : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 19 Aspen Conference on Gravitational Waves and Their Detection, Syd Meshkov : : : : ...

1. Resource selection specialization may increase vulnerability of populations to environmental change. One environmental change that may negatively impact some populations is the broad decline of quaking aspen Populus tremuloides, a preferred nest tree of cavity-nesting organisms who are commonly limited by nest-site availability. However, the long-term consequences of this habitat change for ...