Operational Influences Affecting Sawlog Weight and Volume Relationships in the Intermountain West

Abstract

As weight-based timber sales become more common in the Intermountain West, characterizing the factors affecting weight-to-volume relationships for softwood sawlogs has become more important. Several factors are thought to affect sawlog weight and volume (W:V) relationships, but the relative importance of weather, topography, species, and region in the western United States has not been quantified. Analysis was conducted to determine the factors affecting W:V relationships across the state of Idaho for commercial softwood sawlogs. Using 7,929 sorted and scaled sawlog loads sampled throughout Idaho from 2011 to 2013, we studied the relationships between log small-end diameter (SED), region, atmospheric temperature, precipitation, and elevation, to assess changes in W:V. Relationships of W:V using mixed-effects models were strong (R2 of 0.74 to 0.90, P < 0.05) when fitted individually by species, with volume modeled as a function of weight, SED, truckload piece count, percent defect, and seasonal quarter: Y (board foot volume) = β0 + β1 (Tons) + β2 (SED) + β3 (Piece Count) + β4 (Length) + β5 (Defect) + β6 (Seasonal Quarter) + β7 (1|Sale Number/Ticket) + u (Error).