Variation of cork oak wood density

The radial variation of the wood density components in the cork oak (Quercus suber) was studied in trees that had never been debarked (30 to 40 years of age) and in trees under cork production (37 to 60 years of age) using X-ray and microdensitometric techniques. The following variables were calculated: ring width, mean ring density, minimum density, maximum density, earlywood density and latewood density. The results showed that the Quercus suber wood is very dense and has a small intra-ring variability. The overall average ring density was 0.86 g.cm3, with a minimum density of 0.79 g.cm3, and a maximum density of 0.97 g.cm3. The mean earlywood density was 0.80 g.cm3 and the latewood density 0.90 g.cm3. The ring density and all the density components showed a tendency to decrease from pith to bark more rapidly up to the rings 13-15, and then only slightly. The mean annual growth was 3.9 mm/yr and the latewood percentage was 57% of the annual growth. In average, there were no significant differences between never debarked trees and trees under cok production. However for the never debarked trees the radial patterns of the density components decreased outwards more than in the debarked ones. It could be speculated that with cork extraction, there is a displacement of extractives from heartwood to sapwood, thereby reducing wood density in the innermost rings and increasing it in the outward rings.