Treesearch

In a large factorial study replicated in six locations, responses of five Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and two western hemlock (Tsuga heterophylla (Raf.) Sarg.) stock types, tubed and untubed, were observed when planted after each of four site preparation treatments with and without later release. In 10 years, more Douglas-fir seedlings survived than did western hemlock seedlings, 69.6 vs. 57.7 percent, averaged much taller, 543.7 vs. 416.6 cm, and larger in diameter, 8.2 vs. 5.2 cm. Survival of tubed seedlings averaged 82.2 percent, untubed 50.5 percent. Seedling...

Wildfire is one of several potential disturbances that could have extraordinary impacts on individuals and communities in fire-prone areas. In this article we describe disturbance risk perceptions from interviews with residents in three Florida communities that face significant wildfire and hurricane risk. Although they live in areas characterized by emergency managers as having high wildfire risk and many participants have direct experience with wildfire, residents tended to share high hurricane and low wildfire risk perceptions. The different perceptions of risk seem linked to several...

Because of their unique physiology, lichen communities are highly sensitive to climatic conditions,making them ideal bioindicators for climate change. Southeast and south-central Alaska host diverse and abundant lichen communities and are faced with a more rapidly changing climate than many more southerly latitudes. We develop sensitive lichen-based indicators for tracking the effects of climate change in south-central and southeast Alaska. Using 196 plots, we model community composition and 12 individual species abundances in relation to synthetic climate variables. Both types of lichen...

The range of sugar maple (Acer saccharum Marsh.) is expected to shift northward in accord with changing climate. However, a pattern of increased sugar maple abundance has been reported from sites throughout the eastern US. The goal of our study was to examine the stability of the sugar maple southern range boundary by analyzing its demography through the southern extent of its distribution. We analyzed changes in sugar maple basal area, relative frequency, relative density, relative importance values, diameter distributions, and the ratio of sapling biomass to total sugar maple biomass at...

Structural class systems are species-independent product classification systems for structural timber. They are used throughout the world to reduce the number of species and grade choices that face the designer of wood construction projects. Structural class systems offer an opportunity to simplify timber specification in North America and to encourage more effective quality standardization across product types. This report gives some background information on the development of major structural class systems used in other countries. The guiding principles of a new ISO Structural Class...

ASTM International D1990 Standard Practice for Establishing Allowable Properties for Visually-Graded Dimension Lumber from In-Grade Tests of Full-Size Specimens, that governs the development of design values for dimension lumber in North America, was first adopted in 1991with recognition that the resource and manufacturing of lumber could change over time impacting design values. D1990 Section 13 instructed users of the standard to conduct a reassessment of property values derived by the practice if there is cause to believe that there has been a significant change in the raw material...

Two important wood properties are the modulus of elasticity (MOE) and the modulus of rupture (MOR). In the past, the statistical distribution of the MOE has often been modeled as Gaussian, and that of the MOR as lognormal or as a two- or three-parameter Weibull distribution. It is well known that MOE and MOR are positively correlated. To model the simultaneous behavior of MOE and MOR for the purposes of wood system reliability calculations, we introduce a bivariate Gaussian–Weibull distribution and the associated univariate pseudo-truncated Weibull (PTW). We note that theoretical arguments...

Cellulose nanocrytals (CNCs) are predominantly produced using the traditional strong acid hydrolysis process. In most reported studies, the typical CNC yield is low (approximately 30%) despite process optimization. This study investigated the hydrolysis of a bleached kraft eucalyptus pulp using sulfuric acid between 50 and 64 wt % at temperatures of 35−80 °C over time periods of up to 240 min for the production of CNCs. The experimental design captured the feature of the coexistence of a variety of reaction products, such as CNC, cellulosic solid residue (CSR), glucose, and xylose, in the...

This study was designed to evaluate the performance of the extended wall structural panel connection in resisting combined uplift and shear forces at the roof-to-wall interface with a focus on a truss heel height of 24 in. to address the expected increases in the depth of attic insulation used in Climate Zones 5 and higher. Five full-size roof-wall assemblies were constructed with extended oriented strandboard (OSB) wall sheathing and each was tested under a different loading combination. Our test results indicate that using extended wood structural panel wall sheathing as the primary...

Color degrade in soft maple can be minimized by drying soon after harvest at temperatures that do not exceed 43 °C.