Development of a rapid wood density evaluation instrument

A need for a field method of evaluating wood density in tree breeding programs has been recognized by tree breeders worldwide. A densitometric method based on compression of increment cores is described in this paper. Radial compression of 5-mm-diameter cores in a specially designed cylinder demonstrated that the substance obtained in this manner had essentially constant density, allowing bulk density calculation from the initial and compressed core volumes. A regression of actual versus predicted density for 82 increment cores obtained from the 5 different British Columbia softwood species of Douglas-fir, Sitka spruce, western hemlock, lodgepole pine, and amabilis fir gave a coefficient of determination of 0.973. After these highly encouraging results were obtained from laboratory trials, a semi-portable field prototype density tester was built, incorporating a direct current electric motor-powered screw actuator to apply the compressive force. A split compression chamber design consisting of two longitudinal halves was chosen to allow easy insertion and removal of core samples. The weight of this unit was approximately 16 kg and overall dimensions were 75 cm long by 19 cm wide by 18.4 cm high (30 in. by 7.5 in. by 7.25 in.). Total time required for density measurement of a core sample was approximately 30 seconds.

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