Maps and models of density and stiffness within individual Douglas-fir trees

Abstract

Spatial maps of density and stiffness patterns within individual trees were developed using two methods: (1) measured wood properties of veneer sheets; and (2) mixed effects models, to test the hypothesis that within-tree patterns could be predicted from easily measurable tree variables (height, taper, breast-height diameter, and acoustic velocity). Sample trees comprised an assortment of 25 coastal Pacific Northwest Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees grown on three sites under a range of thinning regimes. At harvest, trees were 36 years old on one site, and 45 and 51 on the other two. After felling and crosscutting, bolts were peeled into veneer, labelled, dried, weighed, measured, and non-destructively tested using a Metriguard 2600™ veneer tester. The labels allowed each sheet to be tracked back to the peeler bolt and consequently to the position within the parent tree from which it came, and the measurements allowed calculation of veneer density and, after application of the fundamental equation for propagation of sound, veneer stiffness. Maps of each parent tree created from the veneer data clearly demonstrated regions of higher density and stiffness. Furthermore, within each tree, density was approximately normally distributed, while stiffness tended to have moderate negative skew. Maps developed using mixed effects models showed very good correspondence between measured and predicted patterns, particularly for density. Despite differences in age, site and silviculture, results from this study suggest that it is possible to predict within-tree wood properties using easily measurable tree variables.

Citation

Todoroki, Christine L.; Lowell, Eini C.; Dykstra, Dennis P.; Briggs, David G. 2012. Maps and models of density and stiffness within individual Douglas-fir trees. SCION. 42: 1-13.