Uniformity of wood density assessed from X-rays of increment cores

Summary

Variations in wood density within and across growth rings were measured in lodgepole pine, ponderosa pine and Douglas-fir wood samples using X-rays and a digital integrator. Densities were automatically recorded at 14 successive levels from .20–.25 to .85–.90, then converted to percent figures to yield numerical tables of wood density distributions in the samples. Densities ranged from .20–.91 in lodgepole pine, .19–.93 in ponderosa pine, and .18–.97 in Douglas-fir. Uniformity was computed using magnitude of departures from mean density as accumulated across growth rings. Lodgepole pine was the most uniform, followed by ponderosa pine and Douglas-fir. Mean densities were .36, .39, and .43 for the three species. Additional data and descriptions of original equipment designs and methods are included.