Variation of some vessel characteristics of plantation Eucalyptus regnans F. Muell

Some vessel characteristics of six 15-year old plantation grown Eucalyptus regnans F. v. Muell. trees from a progeny trial in Narbethong, Victoria were studied. The within and between tree variation of vessel frequency and percent tyloses with distance from the pith, between six heights and between the six trees was examined. Vessels and vessels containing tyloses present on the cross-sectional surface of 7 mm by 7 mm wood blocks taken from pith to bark were counted using a stereo zoom microscope. Analysis of variance was used to examine the variation of vessel frequency and percent tyloses with: distance from the pith; between the north and south axes; between the base, breast height, 20%, 40%, 60% and 80% of total tree heights; and between the six trees. Data in graphical form coupled with microscopic observations were used to examine the within and between growth ring variation. The overall mean vessel frequency for the six 15-year old trees was 7.885 vessels/mm2. Variation of mean vessel frequency with distance from the pith, between heights and between trees was statistically significant. However, after area weighting the vessel frequency values, there was not a significant difference between trees. Mean vessel frequency generally increased with height, with means of 7.100 vessels/mm2 at the base and 10.722 vessels/mm2 at the 80% height, and decreased from the pith to the bark. The variation between axes and with all interactions between the main factors were not significant. Vessel frequency was observed to vary within and between growth rings. Vessel frequency was lowest in the region at the latewood to earlywood boundary and highest in the central portion of the growth ring. Vessels containing tyloses were found at all six heights of all six trees and the mean percent tyloses for the six trees ranged between about 7 to 18%. The variation of mean percent tyloses with distance from the pith, between heights, between trees and the interaction between height and tree was statistically significant. The percent tyloses was lower in the region near the pith and in the sapwood region near the bark and highest in the central region between the pith and the bark. The percent tyloses varied between about 10 and 40% in a cyclic or wave-type manner over distances of about 10 to 15 mm from pith to bark but did not appear to be related to vessel frequency. The mean percent tyloses showed a general decrease with height, with the base height having a mean of 20.387% and the 80% height a mean of 6.448%. The largest tree mean was 17.568% and the lowest was 7.219%. The relative magnitude of the mean percent tyloses at each height and the ranking between heights varied between trees. For all six trees the frequency of vessels was greater toward the top of the trees but fewer vessels contained tyloses at these upper heights. It may be that timber removed from the upper portions of the stem might be more permeable to liquids such as in the preservation and pulping processes and may release moisture upon drying more easily