Treesearch

Plant-pathogenic fungi produce cutinase, an enzyme required to degrade plant cuticles and facilitate penetration into the host. The absence of cutinase or a decrease in its production has been associated with a decrease in pathogenicity of the fungus. A set of isogenic strains of Cryphonectria parasitica, the chestnut blight fungus, was tested for the presence and amounts of cutinase activity. The virulent strain of C. parasitica produced and secreted significantly higher amounts of cutinase than the hypovirulent strains. Use of both nucleic acid and polyclonal antibody probes for cutinase...

Although the 1990-91 recession has temporarily dampened the demand for hardwood lumber, the decade of the 1980s was a period of strong growth in the hardwood market. After experiencing a flat market in 1980 and a decline in 1982, the demand for hardwood lumber by both the domestic industry and the export market increased strongly—from 8 billion board feet in 1982 to 11.2 billion in 1989. Only in 1990 did this growth moderate and then fall slightly to 11.1 billion board feet. Indications are that the slower market for hardwood lumber continued through the third quarter of 1991.

Bacillus thuringiensis (B.t.) is one of the insecticides considered effective for suppression of gypsy moth infestations, and it is considered to one of the most selective in terms of its effects on other insects. Although B.t. is touted to be "environmentally safe", there is a paucity of field data to support this claim, particularly as it relates to the effects of B.t. on native Lepidoptera. Increasingly, lepidopterists, environmentalists, the general public, and certain forest managers have expressed concerns that B.t. may, in fact, have a significant negative impact on non-target...

Cavity-nesting birds provide significant benefits to forest communities, but timber management techniques may negatively affect cavity-nesting species by reducing the availability of suitable nest and foraging sites. We surveyed cavity-nesting birds from transects in eight Massachusetts oak stands to examine the effect of thinning with retention of snag and wildlife trees on bird use of those stands. We found no difference (P > 0.05) in number of primary- and secondary-cavity nesters detected per km among thinned and unthinned stands when snag and wildlife trees were retained during...

The quality of life we cherish is in many ways dependent on the health and accessibility of our forests. Forests provide recreational and aesthetic relief from the pressures of modem society, as well as the raw material for a multitude of wood products. Many rural communities rely heavily on economic benefits provided by timber, tounsm, and other forest-related rec-reation industries. Since approximately 85% of all timberland in the highly populated East is privately owned, these owners and the decisions they make are extremely important in maintaining quality of life and economic vitality...

Breeding birds were counted along transects across edges of even-aged northern hardwood stands in the White Mountain National Forest, New Hampshire, U.S.A. Two replicate transects across each of 7 edge types representing 3 classes of contrast (abrupt, intermediate, and subtle) were sampled during June 1983-1985 to define species assemblages at stand edges and estimate the width and longevity of functional edges under even-aged management. Of 52 bird species, 28 occurred across all three classes of edges, but no unique species or assemblages were evident at the edges between stands. Across...

A two-dimensional nonhydrostatic atmospheric model was used to simulate the circulation patterns (wind and vorticity) and turbulence energy fields associated with lines of extreme surface heating on simple two-dimensional hills. Heating-line locations and ambient crossflow conditions were varied to qualitatively determine the impact of terrain geometry on the development of buoyancy-induced horizontal roll vortices and their turbulence structures. The model simulations indicate that the type of induced circulation that develops near a line of extreme surface heating on a simple hill is...

A two-dimensional, nonhydrostatic, coupled, earth/atmospheric model has been used to simulate mean and turbulent atmospheric characteristics near lines of extreme surface heating. Prognostic equations are used to solve for the horizontal and vertical wind components, potential temperature, and turbulent kinetic energy (TKE). The model computes nonhydrostatic pressure deviations from a derived atmospheric continuity equation. Horizontal pressure gradients generated from surface heating are calculated from thermal wind principles. Model simulations indicate the development of buoyancy-induced...

Clamp connections were observed in basidiospore dilutions from each of four North American biological species of Armillaria (A. gallica, A. sinapina, A. ostoyae, and A. calvescens) following spore germination and hyphal anastomosis. The occurrence of clamp connections in intrabasidioma pairings of single-germinated basidiospores and of excised margin-hyphae of Armillaria ostoyae and A. gallica was that expected of a bifactorial incompatibility system. All intraspecific pairings between basidiospores or excised margin-hyphae from actively growing haploid cultures from two different basidioma...

Differences in 10-year heights, 4-year growth from 1987 through 1990, relative timing of budbreak and damage by the balsam twig aphid (Mindarus abietinus Koch.) among balsam fir (Abies balsamea (L.) Mill.) from 6 Vermont seed sources originating from different elevations were examined. Height differences among seed sources were highly significant and trees from high elevation seed sources tended to be the shortest. Differences in 4-year growth among seed sources were also highly significant and followed the same trend as total height. Although differences in the amount of twig aphid damage...