Beslutsunderlag för energianpassade gallringar i Västerbotten

The demand for renewable energy is increasing in Sweden. This consequently increases the pressure for and willingness to pay for forest fuels. One method to extract forest fuel from suitable commercial thinnings is the "long top method” (LT-method). With this method saw logs and non-delimbed tops are recovered, i.e. no pulpwood is recovered. Branches from delimbed sawlogs are not recovered and only long top (with branches and needles still attached) is hauled the landing site. To optimize income from the LT-method knowledge about the share of recovery of respectively saw logs and fuel wood at different stand conditions and top diameters are needed. The purpose of this study was to develop a decision support for the LT thinning method in Västerbotten and make an assumption of the outcome at stand level and the proportions of biomass in stem, branch and needles. Thinning outlet was 35% of basal area. Four types of forests were formed for two regions in Västerbotten, Lapland and the coastal region. The forest types were pine, spruce, coniferous and mixed forests. Forest data (test area with associated sample tree) were retrieved from the national forest surveys database and then processed. Forests in need of commercial thinning were sorted out (average dbh 19 cm). Forest functions were compiled, a model was established and implemented to Microsoft Excel. The model estimates the outcome of non delimbed wooden parts per region and for each forest type at three different top diameters for saw logs; 10, 12 and 14 cm. A decision support for energy-suited thinning has been developed. Among the forest types the mixed forest yield the highest outcome in this type of thinning in both regions, in the coastal region between 25 and 29 tonnes dry matter/ha and in Lapland between 22 and 24 tonnes/ha depending on the diameter of the top saw log. The second largest outcome at the theoretical thinning were spruce forests and the coniferous forests in Lapland, these were calculated to an outcome between 10 and 17 tonnes dry matter/ha. The largest difference in percent between the coastal region and Lapland was in pine and coniferous forests located in the coastal area which had approximately 30% lower outcome. This work can be used for prediction of biomass outcome under different conditions in Västerbotten, and consequently for optimization of income. The model should further be developed to cover, and be valid, in all regions of Sweden