Juvenile wood in Irish grown Sitka spruce and the impact of rotation length.

Abstract

The impact of rotation length on the level of juvenile wood in Sitka spruce (Picea sitchensis (Bong.) Carr.) in Ireland was investigated. Mean density was 539 kg/m3 at the first growth ring, rising to 558 kg/m3 in the second, and thereafter declining to 384 kg/m3. Demarcation between juvenile and mature wood was assumed to occur at growth ring 14, where the mean density was lowest. The proportion of juvenile wood was then estimated for Sitka spruce of yield class 24, and was found to substantially decline with age, from 30.3% at age 30 to 13.7% by age 46 (tabulated age of maximum mean annual increment), The implications of the results for rotation length policy are discussed.