Summary

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.