A new approach to the development of management instructions for tree plantations

Abstract

Management of tree plantations needs information on the number, time, intensity and type of thinnings, and the length of the rotation. Economically optimal plantation management depends on discount rate and site fertility. This study proposed a new approach to developing management instructions for tree plantations, simultaneously for all discount rates and site classes. The method was applied to larch (Larix olgensis A. Henry) plantations in northeast China. Instead of optimizing the management of individual stands, instructions for thinning basal area, thinning intensity and rotation diameter were optimized. The instructions consisted of three equations, the first indicating the basal area at which the stand should be thinned, the second showing the optimal thinning intensity, and the third model indicating the mean diameter of trees at the moment of clear-felling. Particle swarm optimization (PSO) was employed to simultaneously optimize the coefficients of these three equation models. PSO maximized the average net present value of the management schedules of 29 larch sample plots. The obtained instructions corresponded to earlier results on the effects of different factors on optimal stand management. Management based on the instructions developed in this study resulted in almost equally profitable management as in the case where the management of every plot was optimized separately.