Estimating breakeven prices for Douglas-fir veneer quality logs from stiffness graded stands using acoustic tools.

摘要

Although tree dimensions and external quality characteristics (such as branch size, sweep, and scarring) may have traditionally been sufficient to specify a log-sort, consideration is now being given to specifying such wood properties as density, stiffness, microfibril angle, spiral grain, extractives content, and consumption of energy for processing. More frequently, these internal wood "attributes" are being taken into consideration as important influences on the estimation of timber value. Additional specifications required by wood buyers add extra complexity to the already complex task of log producing and sorting. It has been shown that, without any premium prices and incentives, such requirements for log grades can reduce the total value for the forest owner. Seven second-growth Douglas-fir (Pseudotsuga menziesii) stands of similar age class in Western Oregon were sampled, totaling 1400 trees and more than 3000 logs. Various measurements were taken and several parameters were calculated, including acoustically estimated stiffness and mill veneer recovery, revenues, and costs. A general methodology for estimating the relative breakeven prices of Douglas-fir peeler logs that a mill or any other log purchaser could afford to pay based on acoustic assessment of veneer stiffness differences is presented. Green veneer was the largest source of revenue averaging approximately 80% as compared to that from chippable material and unpeeled cores combined. Smaller trees incurred higher manufacturing costs, up to a 40% difference between the largest and smallest delivered average-size log. The sample with the greatest net revenue ($1145 per thousand board feet) was 3% higher than the next one and more than 16% higher than the lowest one. These results show that stand stiffness grading based on acoustic velocity measurements of Douglas-fir peeler logs could be used as a surrogate measure for potential net returns and hence a premium price could be requested on logs from such stands.