Twelve trees in a 36 year old full-sib progeny plantation, testing a part of the Scots pine breeding population, were analysed for wood density and the width of the earlywood and latewood sections in each annual ring. Wood samples (stem discs) were taken with 1 m intervals along the stem and the analyses covered thus the whole stem. Based on these data, the biomass of the earlywood and latewood of each annual ring in each 1 meter stem section was estimated. Latewood density increased from pith to bark while it decreased from stem base to top. Earlywood density was of similar size both radially and vertically. The biomass in each annual ring increased until around ring number 10 from pith for both wood types. For earlywood it then decreased while it remained quite constant for latewood. Latewood biomass decreased more rapidly towards the top of the tree than earlywood biomass. Heritabilities for earlywood and latewood in each annual ring at breast height (estimated in the same material in a previous study) were related to the corresponding biomasses to indirectly estimate overall heritability for wood density valid for the whole stem. The analyses indicate that the decrease in heritability for latewood density and increase for earlywood density, from the pith to bark, is compensated by the increase in latewood biomass in relation to earlywood biomass. Thus, the heritability of the latewood density and earlywood density seems to have the same influence on the overall heritability for density in the whole stem.
Wood fibre length of Scots pine (Pinus sylvestris L.) was measured in wood sticks and 5-mm increment
cores. The aim was to evaluate whether fibre length estimates from such small-diameter
cores could be used to calculate genetic parameters, in spite of the increased amount of cut fibres
produced at boring. The correlation between mean fibre lengths obtained from cores and sticks,
with substantially fewer cut fibres, was high (r = 0.87, n = 53) and of the same magnitude as the correlation
between samples from varied positions in the same tree (r = 0.87, n = 46). As regards evaluation
of genetic tests and ranking for selection purposes, values from non-destructively sampled
5-mm cores from 0.5 m tree height appear to serve well. Fibre length development along annual
ring classes started to differentiate between trees at annual rings 13–15, and after ring 16 there was
a slight tendency towards stabilisation which may be interpreted as a reasonably advanced transition
from juvenile wood to mature wood.