Seasonal Changes in Live Tree Branch Moisture in Oregon, USA: Four Case Studies

摘要

Moisture content management is key to improve forest harvest residue economics for biofuel production. Branches are a large component of these residues, especially when residual bole components are diverted to pulpwood. The literature is not clear about seasonal moisture patterns for the main forest species commercially harvested in Oregon, and most studies have focused on bole wood. A repeated-measurements experiment was implemented to determine seasonal moisture content changes in four western and central Oregon research sites. From all sites, the highest moisture recorded was 50% in ponderosa pine during winter; the lowest was 43% in the summer for Willamette Valley Douglas-fir. Ponderosa pine had significantly higher moisture content in the winter compared to other seasons (1.6-9.0% higher), and summer branch moisture was considerably lower than fall (4.4-2.0% lower). Willamette Valley Douglas-fir branches had significantly lower moisture content during summer compared to other seasons (1.0-4.8% lower). In addition, regression equations were developed to predict branch moisture content from branch height (R-2 0.36-0.58) and branch heartwood diameter (R-2 0.69-0.93). Although branch heartwood resulted in a more accurate alternative for predicting branch moisture content, it requires destructive sampling.