Röjningsförbandets betydelse för avverkningsekonomin i södra Sverige

Sammanfattning: The aim of this work is to demonstrate how the net present value (NPV) at the time of the first thinning depends on the spacing after pre-commercial thinning, and show how net value from first thinning in same stand is influenced. This study is performed with models based on non-distant dependent growth models for single trees. Two different growth models have been used, one for cleaning (pre-commercial thinning) and one for thinning. The first one yields stem density distributed over diameter classes. In the second one, (the thinning model), it is possible to choose when thinning should be done, the thinning method, thinning grade and numbers of thinning. Growth functions that are not influenced by thinning are applied. The models have also been used in project "Hugin". The rate of interest used at the calculations, the silviculture and quality aspech are also discussed. The conclusion of this project is that it might be reasonable with more information about the importence of different spacings for the NPV under different rates of interest. According to the results in this study, it also might be conceivable to make a reduction of recommended stem density before first thinning in "The Royal Boards' (Skogsstyrelsens) template for thinning", (when rate of interest is 2 %), especially for spruce. The reduction of recommended stem density before first thinning is in the region of: Pine T20: 0 T24: 100 T28: 500 Spruce G24: 500 G28: 600 G32: 600 G36: 600 This study do not consider that a lower stem density gives higher cleaning cost.