Effect of reduced rotation length on Araucaria wood quality.

Abstract

The review of existing information has identified the following:

- the juvenile core in Araucaria is probably contained within the first 15 growth rings in the pith, with spiral grain being a chief determinant of its extent within the stem;
- a reduction in rotation length for a given site index will reduce ASV and mature wood volume, with an increase in the proportion of juvenile wood;
- for a given rotation length, lower ASV stems were estimated to contain a lower proportion of juvenile wood (based on the assumptions made and crude simulations using WEEDS, PL YSIM and STEPS software); regardless of juvenile wood proportions, smaller stems will yield a higher proportion of pith-in material;
- an increase in the proportion of juvenile wood, due to a reduction in rotation length, could affect wood quality due to an increase in the proportion of the recovery containing high spiral grain, shorter tracheids and higher micellar angle;
- high spiral grain and high micellar angles adversely impact on wood quality through their influence on twist and longitudinal shrinkage, respectively;
- positive outcomes from a reduction in rotation length might include an increase in the proportion of live knots in upper stem sections and a reduction in the extent of brown-stain heartwood;
- the uniformity in basic density within Araucaria stems means reduced rotation lengths and lower stem ASVs are unlikely to have a major impact on this wood property, and
- the effect of a reduction in rotation length on the incidence of compression wood and timber susceptible to kiln staining could not be established from the available information.