Management of Mixed-Species, Uneven-Aged Forests in the French Jura: From Stochastic Growth and Price Models to Decision Tables

Abstract

A deterministic matrix growth model of uneven-aged stands of fir, spruce, and hardwood trees was extended to recognize random shocks. The results showed that the expected basal area of hardwoods, mainly beech, was substantially higher in the long run than that predicted by the deterministic model. A parallel stochastic model of prices was also developed from past data. It showed that real prices had no trend but that they were autocorrelated over time. The stochastic stand and price models were simulated simultaneously to obtain the probabilities of transition between stand and market states. This transition probability matrix was used in Markov decision-process models to calculate the best decision in each possible stand and market state. The policies examined included maximizing net present value, or expected tree diversity, production, or annual returns, subject to constraints on net present value, expected tree diversity, and basal area. A general mathematical programming method is presented to optimize economic or ecological objective functions subject to multiple constraints with or without time discounting. In the French Jura context, the solutions suggested that high net present value could be obtained while maintaining the average basal area near its current level, and keeping a high level of tree diversity. Accounting for risk called for more intense harvesting to raise revenues, and it led to stands that were much more diverse than suggested by deterministic solutions. FOR. SCI. 51(1):64–75.