چکیده:
Economically optimal management of a continuous cover forest is considered here. Initially, there is a large number of trees of different sizes and the forest may contain several species. We want to optimize the harvest decisions over time, using continuous cover forestry, which is denoted by CCF. We maximize our objective function, the expected present value, with consideration of stochastic prices, timber quality variations and dynamically changing spatial competition. The problem is solved using an adaptive control function. The parameters of the control function are optimized via the first order optimum conditions based on a multivariate polynomial approximation of the objective function. The second order maximum conditions are investigated and used to determine relevant parameter ranges. The procedure is described and optimal results are derived for a general function multi-species CCF forest. Concrete examples from Germany, with beech, and from Sweden, with Norwegian spruce, are used to illustrate the methodology and typical numerical results. It is important to make market adapted harvest decisions. If the stochastic price variations are not considered when the harvest decisions are taken, the expected present value is reduced by 23%.
خلاصه ماشینی:
Market Adaptive Control Function Optimization in Continuous Cover Forest Management Peter Lohmander Optimal Solutions in Cooperation with Linnaeus University, Umea, Sweden (Received: October 16, 2018; Revised: April 28, 2019; Accepted: May 13, 2019) Abstract Initially, there is a large number of trees of different sizes and the forest may contain several species.
We maximize our objective function, the expected present value, with consideration of stochastic prices, timber quality variations and dynamically changing spatial competition.
With the help of this function, all of the harvest decisions, of every tree, are optimized in such a way that the expected value of the total objective function is maximized.
In this paper, this method will be utilized to derive optimal adaptive control functions in forest management.
Lohmander (2007) presents several optimization methods and typical solutions to adaptive forest management problems.
Numerical tests showed that the optimized values of the harvest control function parameters usually converge to stable solutions also with rather low number of hectares.
The present approach makes it possible to determine optimal adaptive control rules and to estimate the economic values of mixed forests with trees in many size classes and of many species.
Discussion In the introduction, the central question of this study was presented: “What is the best way to sequentially update the information and adaptively determine the management decisions?” Now, we have seen that it is possible to obtain a significant improvement of the expected present value, if the timber market prices and tree sizes are sequentially monitored and harvest decisions are adaptively optimized via the derived optimal control function.