Log and lumber grades as indicators of wood quality in 20- to 100-year-old Douglas-fir trees from thinned and unthinned stands.

Abstract

This report examines the differences in wood characteristics found in coastal Pacific Northwest Douglas-fir (Pseudotsuga mensziesii (Mirb.) Franco) trees harvested at the age of 70 to 100 years old to wood characteristics of trees harvested at the age of 40 to 60 years. Comparisons of differences in domestic log grades suggest that the proportion of log volume in the higher grades (Special Mill and No. 2 Sawmill) increased with both stand age and tree size. Simulation of lumber grade yields based on log characteristics suggests that yields of higher grades of lumber increased until about age 60 to 70, and then leveled off over the rest of the age range examined in this analysis. We included structural lumber products in the analysis but not higher value appearance grade products, and some evidence suggests that yields of these products might have begun to increase in the oldest trees. The analysis also showed that the younger trees had larger branches and more juvenile wood, possibly because they had been grown in stands that received a higher level of early stand management than the older trees. If these young trees were grown to the ages of 70 to 100, they likely would not produce the same log and lumber grade yields found in the older trees we examined.

Young-stand management options and their implications for wood quality and other values

“…Projection of lumber recovery by using sawing simulation models is becoming an accepted alternative to more expensive empirical wood product recovery studies (Todoroki, 1990(Todoroki, , 1995Steele et al, 1994;Pont et al, 1999). Inexpensive techniques have been developed to diagram the branch size and position in logs either for sawing simulations to estimate lumber grade yield (Barbour et al, 1999) or to combine this information with other log characteristics, e.g., growth rate and diameter, to estimate log grade yields (Barbour and Parry, 2001). These techniques would be appropriate for use in southeast Alaska and could be incorporated into evaluations of other thinning trials or remeasurements of existing spacing trials.…”

Effects of Silviculture and Genetics on Branch/Knot Attributes of Coastal Pacific Northwest Douglas-Fir and Implications for Wood Quality—A Synthesis

“…Examination of log grades and sorts, product recovery studies, and discussions with log buyers indicate that the four following log characteristics predominate in log specifications: minimum rings per inch, minimum log diameter, maximum knot diameter, and maximum length [9][10][11]. Unfortunately, current log grades are not always indicative of lumber quality recovered during processing [2,12].…”

“…Product recovery researchers have found that a measurable log attribute referred to as largest limb average diameter (LLAD) [2], also known as branch index or BIX [9], is a good predictor of product grade recovery. LLAD is obtained by measuring the diameter of the largest knot in each lengthwise quadrant or face of the log and calculating the average (Figure 4).…”

Productivity of Western forests: a forest products focus.

“…Ty p i c a l l y, each log grade or log sort has a maximum knot diameter (Bowers 1997) and product recovery researchers have found that largest limb average diameter (LLAD, Fahey et al 1991) also known as branch index (bix, Barbour & Parry 2001), defined as the average of the largest diameter knot in each of the four quadrants or faces of the log surface, is a good predictor of product grade recovery from a log. One can hypothesize that the diameter of the largest knot or LLAD, measured with a caliper on the lower bole, would be highly correlated with the largest knot diameter or LLAD of logs within the tree.…”