Height development of Betula and Salix species following pre-commercial thinning through breaking the tops of secondary stems: 3-year results

• Published in: Forestry
• Main Authors: Karlsson, A, Albrektson, A
• Format: Text
• Language: English
• Published: Oxford University Press 2001
• Subjects: Articles; Stump; The Stump; Northern Sweden
• Online Access: http://forestry.oxfordjournals.org/cgi/content/short/74/1/41; https://doi.org/10.1093/forestry/74.1.41

Reducing competition by topping secondary stems may be an attractive alternative to traditional pre-commercial thinning in forestry, for both biological and financial reasons. In this study, the height development of secondary and main stems of birch ( Betula pubescens Ehrh. and Betula pendula Roth, species not separated), and secondary stems of willow ( Salix spp.) following such topping was examined in an even-aged and naturally regenerated stand in northern Sweden. At a main stem mean height of 2.8 m, the following treatments were applied to all secondary stems: top-breaking at 40 per cent (111 cm above ground) or 65 per cent (184 cm above ground) of main stem mean height. A control group (average height of secondary stems, 221 cm) was left untreated. Post-treatment damage to the trees was frequent for both genera. For birch, treatment rankings for all the secondary stems, and for undamaged secondary stems, according to height development after three growing seasons, were control >=top-breaking at 65 per cent >=top-breaking at 40 per cent. For willow, the greatest height growth was observed after top-breaking at 65 per cent. The results indicate that the 'stump height' (break-point) could be raised to a level of at least 65 per cent in this birch stand without risk of the main stems being overtopped. During the study period, 50 per cent of the main stems exchanged their leading shoots at least once.