MOE DISTRIBUTION IN VISUALLY GRADED PONDEROSA PINE LUMBER HARVESTED FROM RESTORATION PROGRAMS IN SOUTHERN OREGON AND NORTHERN CALIFORNIA

Abstract

Every year, restoration programs in Southern Oregon and Northern California produce large amounts of low-value Ponderosa pine (PP) lumber, which has limited market in the US. Engineered wood products, such as CLT and glulam, are expected to provide a value-added market to offset the high costs of restoration programs. However, restoration program lumber has larger amounts of juvenile wood and visual grades are reported to show lower mechanical properties compared to commercially harvested material, on which the National Design Specification (NDS) design values are based. This research addresses a knowledge gap on the impact of juvenile wood and visual, strength-affecting characteristics on the mechanical performance of PP lumber generated in the region of interest. The purpose of this study was to assess this impact based on measured moduli of elasticity (MOE) of samples of visually graded and ungraded restoration program PP lumber. The results were compared to previous studies and published values for commercially harvested PP as reflected in the NDS Western Woods (WW) species group. The results show that characteristic MOE values of visual grades No. 1 and 2. of PP from restoration programs were lower than respective design values for NDS WW group. However, the mean MOE values of all groups considered individually as well as pooled together were higher than NDS WW grade No. 3. MOE distributions for all groups, except for the visual grade No. 1, were remarkably similar showing negligible differences at 5^th percentile, which may indicate negligible differences in correlated strength design values, not measured in this study. The average MOE of PP harvested in Southern Oregon and Northern California were higher than those reported for Columbia PP harvested in North Idaho.