Browsing by Subject "yhden puulajin metsä"
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(2013)This thesis studies the economically optimal timing of thinnings and final harvest on Costa Rican Tectona grandis plantations. Consequently this thesis studies the profitability of the plantations and makes a comparison to previous studies. Optimization is based on programming with AMPL with Knitro optimizing software. The objective function used is the Faustmann formula. Different rates of interest are used. The ecological functions used for the modeling were obtained from previous studies by Pérez and Kanninen (2005a). The economic data such as planting and thinning costs and log prices were obtained from a T. grandis plantation specialist. The results of the study show that the optimal harvesting regime in T. grandis plantations differs from what is suggested in literature. The main findings are that the optimal rotation length is shorter and both timing and intensity of the thinnings vary depending on the rate of interest used. In addition the maximized bare land values under optimal management regimes are notably higher than bare land values under previously suggested management regimes. The management regime is highly sensitive to the rate of interest used. The management regime is less sensitive to the changes in price than expected. This thesis suggests that the initial density of 816 ha-1 trees results into higher bare land values than 1111 ha-1 trees . However, the difference is minor and possible increase in silvicultural costs is not considered. In addition a simple test is carried out to see the possible effects on heartwood proportion growth to the optimal management regime. The shortcomings and possibilities to improve the model are discussed. It is noted that the price data for T. grandis is not coherent, and that the ecological model could be improved in order to increase its accuracy.
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(2013)This study analyzes the optimal harvesting of single species uneven-aged Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.), and birch (Betula pendula Roth. and B. pubescens Ehrh.) stands, in addition to mixed species stands with all three species. The analysis is based on an economic description of uneven-aged forestry using a size-structured transition matrix model and a single-tree model. The optimization problem is solved in its general dynamic form using gradient-based interior point methods. Similar analysis on uneven-aged birch, Scots pine and mixed species stands in Nordic conditions has not been published. Increasing the harvesting interval decreases the average annual volume yield. Assuming natural regeneration, this suggests that volume yield is maximized by uneven-aged rather than even-aged management. The present value of stumpage revenues is maximized after saw timber and pulpwood prices, interest rate, and a 15-year harvesting interval are included. The economically optimal solution with a 3% interest rate produces an annual yield of 1.9, 5.5 and 2.9 cubic meters (m3) for Scots pine, Norway spruce, and birch respectively in single species stands at site with average productivity. At less productive sites, the mixed species stand is heavily dominated by Norway spruce regardless of interest rate. At more productive sites on the other hand, increasing interest rate increases species diversity. Both the optimal volume yield and net present value maximization solutions converge to unique species- and site-type-specific steady-states with constant harvests. The transition matrix model typically used in optimization studies is computationally less demanding than the single-tree model, but the differences in optimal solutions are more remarkable than earlier studies show. Additionally, it appears that the investmentefficient optimization model may result in steady-state solutions that significantly differ from the correct solutions.
Now showing items 1-2 of 2