Structural lumber from dense stands of small-diameter Douglas-fir trees

Small-diameter trees growing in overstocked dense stands are often targeted for thinning to reduce fire hazard and improve forest health and ecosystem diversity. In the Pacific Northwest and Intermountain regions, Douglas-fir can be a predominant species in such stands. In this study, mechanical properties and grade yield of structural products were estimated for 2 by 4 lumber cut from logs of small-diameter Douglas-fir trees from a stand in northern California. The results indicate that 70- to 90-year-old suppressed Douglas-fir has excellent potential for the production of all structural lumber products. Grade recovery was determined using five grading systems. When graded as Structural Light Framing, 68 percent of the lumber made Select Structural as Light Framing, 74 percent made Construction grade, 89 percent made STUD grade, 90 percent made 2400Fb-2.0E under machine stress rating rules, and 46 percent would qualify as stock for glue laminated beams. Care must be taken in kiln-drying to avoid the commonly observed problem of twist.