Wood Degradation after Windthrow in a Northern Environment

Abstract

Severe windthrows often require salvage operations that can lead to increased costs. Given these extra costs, it is of paramount importance to make sure that wood degradation does not become so advanced that significant value loss is incurred. The rate at which wood deteriorates is a function of many factors, including species and climate. The study was conducted in a northern area affected by two partial windthrows. Logs from the damaged area were collected for two species, balsam fir (Abies balsamea) and black spruce (Picea mariana). Logs were classified into one of three degradation classes based on visual assessments. A sample of logs from standing trees was also collected. In total, 167 logs were sampled. Each log was sawn and one piece of lumber was selected from each to determine the bending strength and stiffness and the visual grade. The time since tree death, as determined from dendrochronology, ranged from 1 to 31 years. The visual grade of the lumber was not affected after 1 year but severe downgrades were observed after 4 years. Moisture content decreased rapidly for both species during the first year and continued to decrease until 4 years after mortality. No clear decrease in bending stiffness was identified even though such a tendency was noticed for older black spruce windthrows. Bending strength became variable after 4 years for balsam fir and was reduced after 4 years for black spruce. Windthrows older than 7 years will produce low visual grade timber of reduced bending strength and possibly of lower bending stiffness.

Using a Standing-Tree Acoustic Tool to Identify Forest Stands for the Production of Mechanically-Graded Lumber

“…2 and better [35]) for black spruce growing in natural stands [10]. However this percentage may be reduced depending on certain stand-level characteristics, such as the proportion of decayed or windthrown stems [3,40,41]. In addition, sawing defects that can cause downgrades, such as wane, were avoided in our study.…”

Comparison and validation of three versions of a forest wind risk model

“…z 0 is the aerodynamic roughness (m), d is the zero-plane displacement (m), and k ¼ 0.4 (von Karman constant). f CW is a factor to account for the additional moment provided by the overhanging displaced mass of the canopy; f knot is a factor to reduce wood strength due to the presence of knots (usually between 0.8 and 1; Ruel et al, 2010); and MOR is the green wood Modulus of Rupture (Pa) for the particular species, derived from bending tests (e.g. Lavers, 1969).…”

Temporal changes in stem decay and dead and sound wood volumes in the northeastern Canadian boreal forest

“…However, they can bring many benefits to forest ecosystems by providing habitat, seedbed, or a food source for numerous organisms (Harmon et al 1986). The rate at which dead standing trees deteriorate affects undoubtedly the quality and availability of the DSW material (Barrette et al 2012;Ruel et al 2010).…”