Effects of harvesting systems and bole moisture loss on weight scaling of douglas-fir sawlogs (Pseudotsuga Menziesii var. glauca Franco)

Abstract

Characterizing the moisture loss from felled trees is essential for determining weight-to-volume (W-V) relationships in softwood sawlogs. Several factors affect moisture loss, but research to quantify the effects of bole size and harvest method is limited. This study was designed to test whether bole size, harvest method, environmental factors, and the associated changes in stem moisture content of felled Douglas-fir (Pseudotsuga menziesii var. glauca Franco) affected the weight-to-volume relationship of sawlogs. Thirty trees in three size classes (12.7-25.4 cm, 25.5-38.1 cm, 38.2-50.8 cm) were felled and treated with one of two harvesting processing methods. Moisture content was sampled every two days for four weeks. Results showed 6% greater moisture loss in the crowns of stems that retained limbs after felling compared to stems with limbs removed after harvesting. Additionally, moisture loss rate increased as stem size decreased. The smallest size class lost 58% moisture content compared to 34% in the largest size class throughout the study duration. These stem moisture content changes showed a 17% reduction in average sawlog weight within the largest size class, shifting current W-V relationships from 2.33 tons m-3 to 1.94 tons m-3 during the third seasonal quarter for northern Idaho Douglas-fir and potentially altering relationships year-round.