Precleanings effects on first-thinning

Thinning is a part of a forest management program when some merchantable timber is cut while creating better volume growth and higher quality of remaining stems. One arrangement to make the logging operation more effective in thinning is to pre-clean the stand from undergrowth. The purpose of this study was to measure which effects different pre-cleaning methods had on the efficiency of the harvester in a thinning stand. The quantity of stems damaged by the harvester and the forwarder were measured as well as the productivity of the harvester. This study intended to answer the question if the costs of the pre-cleaning could be motivated by increased harvester efficiency and accuracy. The different treatments that have been implemented are that the undergrowth stems have been cut, cut and laid down and an area that have been left untouched. Since the study intended to analyze the relationship between performance and different influencing factors the method of a correlation study has been used. The productivity of the harvester has been calculated and measured against the pre-cleaning costs for each treatment. According to the results the harvester was most effective in the area where the undergrowth was cut and laid down and least effective in the untouched area, both in terms of damaged stems and productivity. From a harvester operator point of view it was most profitable to work in that area. The increased harvester productivity was however not enough to motivate the costs of the pre-cleaning from a landowner perspective. One conclusion from this study is that with given conditions in the current area, the treatment where the undergrowth had been cut and laid down have had positive effects on the harvester productivity and accuracy