Evaluating forest models in a sustainable forest management context

Abstract

My objective is to examine the expected utility of general classes of forest growth models for answering questions regarding the sustainability of forest management. Six classes of forest models are reviewed: Forest Yield Models; Ecological Gap Models (population succession); Ecological Compartment Models (resources fluxes); Process/Mechanistic Models; Vegetation Distribution Models; Hybrid Models. The review reveals structural shortcomings in several classes of models as potential tools for evaluating questions of sustainable forest management. For example, the great disadvantage of Forest Yield Models is that they are not linked to the underlying causes of productivity (the carbon and nutrient cycles, the moisture regime, and climate). Yield models implicitly assume that environmental conditions remain constant. This assumption is clearly unsuitable for evaluating climate change scenarios, which are crucial for long-term sustainability considerations. Hybrid models hold the greatest promise, because they are predicated on producing an operational process model with useful products on yield for the manager (e.g., PipeQual, Stand-BGC). The hybrid modelers base as much of their system on causal process models as is practical, and openly embrace relevant empirical results from yield models to complete the system.