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Wood Density and Anatomical Properties in Suppressed-Growth Trees: Comparison of Two Methods

David W. Vahey, J. Y. Zhu, C. Tim Scott

Abstract


Interest in the commercial value of small-diameter timber has led to testing core samples with SilviScan to characterize density and transverse fiber dimensions. Data showed that latewood density and tracheid diameter in suppressed-growth material can vary spatially on a scale comparable to the 50-μm resolution of the instrument used in our testing. An optical imaging method called Ring Profiler was developed to determine what effect SilviScan's resolution had on the measurements. A single suppressed-growth specimen of Douglas-fir was used to develop the method. Ring Profiler measurements of the specimen showed that SilviScan overestimated latewood tracheid radial diameters by 59% in growth rings averaging 200-μm width. In those same growth rings, SilviScan latewood density was found to be 19% too low. In all growth rings measured by Ring Profiler, latewood wall thicknesses were anisotropic. Radial and tangential values averaged 13% less than the isotropic wall thickness calculated from SilviScan data. Ring Profiler density measurement from binarized images of wood cross-sections was found to correlate well with SilviScan X-ray density (r-squared = 0.907); however, better images and an objective method for thresholding are needed for accuracy over a large sample space. With these improvements and automated scanning of samples, Ring Profiler could be an attractive, inexpensive complement to SilviScan.

Keywords


SilviScan;tracheid;density;diameter;wall thickness;anisotropy;image analysis;resolution;suppressed growth;small diameter;thinnings;pulp

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