Time-related changes in specific gravity and moisture content of spruce budworm killed balsam fir

Abstract

The variation in specific gravity and moisture content of healthy balsam fir (Abiesbalsamea (L.) Mill.) and balsam fir killed by the spruce budworm (Choristoneurafumiferana Clem.) in northern Minnesota has been investigated. Disks were removed at 100-in. (254-cm) intervals along the merchantable boles of 31 healthy trees, 16 trees dead 6 months, 42 trees dead 12months, and 18 trees dead 22 months. Knot-free wedges were cut from the disks and separated into inner and outer sections for specific gravity and moisture content determinations. Outer and inner sections' specific gravity averages for healthy (control) balsam fir varied within tree, decreasing then increasing with height. This trend was not apparent for the outer section specific gravity averages in the dead tree categories. Average specific gravities for the four tree categories were not significantly different even 22 months after death. Tree categories' average moisture content rapidly decreased with time after death, and significant differences were detected within months of tree death. Significant outer section moisture losses occurred within 6 months after death, while significant inner section losses developed after 12 or more months.