The use of a European forest model in North America: A study of ecosystem response to climate gradients

The forest gap model FORCLIM that originally was developed for central European conditions is applied to simulate the species composition of near-natural forests in eastern North America along a latitudinal transect from 60 to 30 degrees N, covering the transition from the tundra to the boreal and deciduous forests. The results show that FORCLIM provides plausible species compositions along this gradient; most of the divergences concern species that are of minor abundance. In the central part of the gradient, the simulated species composition is considerably more realistic than the one obtained in an earlier study with a model developed for these conditions. However, in the boreal forest the behaviour of some light-demanding species is anomalous. Along drought gradients in the south western part of the gradient, FORCLIM misrepresents the influence of increased drought on forest structure, thus pointing to further research needs. The results are discussed within the context of model verification, the applicability of FORCLIM to study climatic change issues and the evolution of different tree species on the two continents. Prospects are outlined for developing a forest gap model that is applicable over a wide range of environmental conditions across several continents, thus contributing to the development of dynamic global vegetation models.