Kvalitet och ekonomi i utförandet av förstagallring baserat på olika gallrings- och underväxtröjningsprogram
Stora Enso Skog has a long term contract regarding felling rights and silvicultural activities on forest owned by Bergvik Skog. In the autumn 2006, Bergvik Skog proposed a new thinning program, ?Bergvikgallring?. The new program implied an increased focus on extraction of smaller trees compared to the present thinning program, Stora Enso Skog?s ?Kvalitetsgallring?. Furthermore, in the new program the thinning decision is based on a dominant height/stand density relation instead of a dominant height/basal area relation. For Stora Enso Skog, the new program raised the question of how to handle smaller trees and emphasized the importance of practicable routines in thinning operations.
The aim of this study was to compare Kvalitetsgallring and Bergvikgallring in terms of the quality and economy of thinning operations. Additionally, preclearance as a complement or substitute to the harvester?s handling of small trees was evaluated. The study was conducted in a 32-year old first-thinning-stand dominated by spruce. A factorial block design was used, in which four combinations of thinning and preclearance were randomly assigned to study units of 0.1 ha in size. In total, the study encompassed 12 study units.
Higher harvester productivity was observed with Kvalitetsgallring, while there was no difference in volumes extracted between thinning programs. Consequently, the increased number of trees extracted could not compensate for the higher productivity when processing larger trees. Preclearance had positive effects on harvester productivity, but the study implied that loss of merchantable roundwood and the diameters of the cleared trees need to be considered when evaluating the economical outcome. For Bergvikgallring, the targets for stand density were difficult to meet, but this was also true for Kvalitetsgallring. There were no significant differences in target fulfilment between the two thinning programs. The results emphasized the importance of education, calibration, follow-up and feedback during thinning operations, especially when the new thinning program should be introduced at full scale.