Browsing by Subject "Natural disturbance Optimal rotation Even-aged forestry Forest economy Ympäristöhäiriöriski Optimikiertoaika Metsäekonomia"

Forests provide important ecosystem services for humans. As climate change continues, disturbances such as extreme weather conditions and drought become more common all over the globe. This causes pressures to forests and forest owners whose incomes might depend on the harvesting profits. This thesis studies natural disturbance risk in profit maximizing forestry and optimizes forest rotation time by maximizing the bare land value while including the risk. The thesis aims to answer what is the optimal rotation with natural disturbances, how the results change when another tree species is introduced and how the share of trees changes the results in the case of natural disturbances. The optimization problem is first analysed analytically and then numerically in MATLAB. In the analytical part, first the optimum is solved for the normal Faustmann rotation model and then the Faustmann model is modified to include a mixture of two different tree species. After that the optimal rotation and bare land value are solved for normal Faustmann model with natural disturbance risk included. Lastly the natural disturbance risk is included to the two species rotation model. Numerical calculations are done for all the four cases: normal Faustmann, Faustmann with a mixture of two species, natural disturbance risk for one species and natural disturbance risk for the two species mixture. The data for mathematical calculations is from Bollandsås, Buongirno and Gobakken (2007) study and the Finnish parameter values are modified. The studied tree species in the numerical model are spruce and birch. The results show that when a second species, in this case birch, is added to the Faustmann-like model for two species mixture, the rotation gets longer and the bare land value decreases. The model with disturbance risk is studied with different disturbance risk probabilities and the results indicate that when the risk increases the rotation time gets shorter and the bare land value decreases. When a second species is added to the natural disturbance model, the results are calculated for different salvage shares. The risk this time depends on the share of birch and the risk decreases when the share of birch is increased. The results show that when the salvage share increases in the optimal solution, the share of spruce and bare land value increases. However, the optimal rotation time does not change that much. The results are similar in other studies that study a similar topic. When the natural disturbance risk is included, the optimal rotation gets shorter, and the bare land value decreases and these results are aligned with other studies. The results with natural disturbances and two tree species are new, as the rotation time does not change much between the different salvage shares. The results indicate that dependency between risk probability and the share of birch appears reversing the effects of birch lengthening the rotation time and risk probability shortening the rotation time.