Treesearch

To properly evaluate the reliability of lumber structures, good models for the strength distributions of their components are needed. Modulus of rupture (MOR) distributions of structural lumber grades have often been modeled as two-parameter Weibulls. However, in a series of papers, Verrill and others have established that strength properties of visual and machine stress rated grades of lumber are not distributed as two-parameter Weibulls and that modeling them as two-parameter Weibulls can yield large over- or underestimates of probabilities of breakage. Instead, grades of lumber have...

Vacuum drying is an economical alternative to conventional drying for many species under a variety of environmental and economic conditions. Vacuum drying can reduce drying time and be more energy efficient compared with conventional steam drying. But there are many factors to consider when comparing the two technologies. This report describes the principles and practices of vacuum drying and discusses its advantages and disadvantages. Among other concerns, final moisture content variation and residual stress have been significant issues of concern with vacuum drying. Standard vacuum...

The Douglas-fir beetle (Dendroctonus pseudotsugae Hopkins) (Coleoptera: Curculionidae) antiaggregation pheromone, 3-methylcyclohex-2-en-1-one (MCH), has been used since 2000 to protect high-value trees and stands throughout western North America. Operational treatments involve placing individual releasers on a 12m× 12m grid throughout the area to be protected. In this study, six widely spaced trap lines were established with aggregation attractant–baited traps located 1, 3, 9, 27, and 81m from a location where an operational MCH release device was alternately either present or absent, and...

Semiochemical background in the environment can influence insect orientation to release points of the sameor different semiochemicals. endo-Brevicomin is a pheromone component of the tree-killing bark beetleDendroctonus frontalis Zimmermann (Coleoptera: Curculionidae: Scolytinae) that has a biphasic dose–responsecurve, enhancing attraction at low release rates but reducing attraction at high rates. We investigated the effectof artificial manipulation of background levels of endo-brevicomin on D. frontalis responses to sources ofaggregation attractant in the field. Traps baited with the...

The southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae: Scolytinae), isamong the most destructive bark beetle pests of pines (Pinaceae) of the southeast and mid-Atlantic UnitedStates of America, Mexico, and Central America. Numerous volatile compounds can stimulate or reduceattraction of the beetle, but efforts to incorporate these into effective, practical technologies for pest managementhave yielded mixed results. Attractants have been incorporated into lures used in monitoringtraps that are employed operationally to forecast outbreaks and detect emerging...

The southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae: Scolytinae) is amajor destructive pest of Pinus L. In the southeastern United States, numbers of this species and a majorpredator, Thanasimus dubius (Fabricius) (Coleoptera: Cleridae), captured during an annual springtime trappingsurvey are used to make forecasts of the likelihood and severity of an outbreak during the following summer.We investigated responses by both species to six lure formulations to evaluate their suitability for the surveyand allow integration of historical data sets produced with...

Being able to associate an organism with a scientific name is fundamental to our understanding of its conservation status, ecology, and evolutionary history. Gastropods in the subfamily Physinae have been especially troublesome to identify because morphological variation can be unrelated to interspecific differences and there have been widespread introductions of an unknown number of species, which has led to a speculative taxonomy. To resolve uncertainty about species diversity in North America, we targeted an array of single-locus species delimitation methods at publically available...

Hazardous fuels such as woody biomass and small-diameter trees accumulate in the forest, contributing to increased risk of wildfires. Two tree species that specifically contribute to this problem in the Midwest and Northeast of the United States are balsam fir and eastern hemlock. If the durability of these two species against fungal decay could be improved, markets for lumber made from these species would increase, contributing to removal of them from the forests. Thermal modification of the wood from these species may improve the fungal durability. In this study, we performed soil-block...

It has been mathematically demonstrated that the distribution of MOR in a graded lumber subpopulation does not have the same theoretical form as the distribution of the mill-run population from which the subpopulation is drawn. However, the distributional form of the graded lumber subpopulation does depend heavily on the distributional form of the full mill-run population, and thus, it is important to characterize the distributions of full mill-run lumber populations. Previous studies presented evidence suggesting that commonly used distributions such as normal, lognormal, and Weibull...

A large family of copulas with gamma components is examined, and interesting submodels are dened and analyzed. Parameter estimation is demonstrated for some of these submodels. A brief discussion of higher-dimensional versions is included