%0 Research article
%T Saw log recovery and stem quality of birch from thinnings in southern Finland
%A Kilpeläinen, Harri
%A Lindblad, Jari
%A Heräjärvi, Henrik
%A Verkasalo, Erkki
%D 2011
%J Silva Fennica
%V 45
%N 2
%R doi:10.14214/sf.117
%U https://silvafennica.fi/article/117
%X The objective of this study was to examine the timber quality of silver  birch (Betula pendula Roth) and European white birch (Betula pubescens  Ehrh.) trees in the first and second thinnings in southern parts of  Finland, from the viewpoint of sawing of small-diameter, short logs, in  particular. The average stem volume of birch was 0.140 m<sup>3</sup> in the first thinning stands and 0.206 m<sup>3</sup> in the second thinning stands. In planted stands, the trees were larger  in the first thinnings but slightly smaller in the second thinnings,  compared with naturally regenerated pure birch stands or mixed stands of  Norway spruce and birch species. Almost 60% of the harvested and 35% of  the remaining stems that could provide saw logs were graded as pulpwood  for timber quality due to the occurrence of stem defects. The most  common stem defects were multiple crooks and middle crooks. Only minor  between-stratum differences were detected in the numbers of defects.  Depending on the bucking option, the total percentage of saw and plywood  logs from the total birch recovery in the thinning of the sample stands  varied between 11.7 and 18.2. The recovery of saw logs was clearly  higher in the second thinnings, 12–19%, than in the first thinnings,  8–14%. Of the stand types, saw log recovery was the highest in planted  birch stands, 12–19%, but lower in naturally regenerated pure birch  stands and mixed stands of Norway spruce and birch. The highest share of  saw logs was in the second thinning of planted stands, 17–25%. This  study shows that the harvesting recoveries of end-use based timber  assortments can be estimated in different kinds of thinning birch  stands. Based on tree and log dimensions and stem squality, silver birch  firstly from plantations and secondly from mixed stands should be the  most interesting source of raw material for the saw milling, furniture  and interior product sectors.