Review of sixteen forest-soil-atmosphere models

The principles and characteristics of sixteen forest-soil-atmosphere models, describing the flows of water, carbon and nutrients in a forest ecosystem were compared. This comparison addresses technical aspects of model implementation and system discretisation, as well as the nature of the included processes. e variety of integrated models exists, but only a few of them are ‘well-balanced’, describing all aspects of the forest ecosystem with a comparable level of detail. As a result, only a few models can be used to assess effects of air pollution and acid deposition on forest growth. is considerable agreement with respect to the description of the water cycle and geochemical processes; differences result mainly from different levels of process aggregation. There is no general agreement on the description of the nutrient cycle. Models differ most with respect to nutrient uptake and nutrient (re)allocation in the plant. impossible to develop simple lumped models for regional, policy-oriented applications, without a well-based strategy for simplification. Therefore, simple models should always be backed up by more detailed mechanistic models, which can be tested against field observations. few models are well-documented and available to others. The lack of concise and adequate model documentation hampers model exchange and may lead to unnecessary development of new models. Therefore, model documentation must be given high priority.