Empirical ecological response surfaces were derived for eight dominant tree species in the boreal forest region of Canada. Stepwise logistic regression was used to model species dominance as a response to five climatic predictor variables. The predictor variables (annual snowfall, degree-days, absolute minimum temperature, annual soil moisture deficit, and actual evapotranspiration summed over the summer months) influence the response of plants more directly than the annual or monthly measures of temperature and precipitation commonly used in response surface modeling. The response surfaces provided estimates of the probability of species dominance across the spatial extent of North America with a high degree of success. Much of the variation in the probability of dominance could be related to the species' individualistic response to climatic constraints within different airmass region. A forest type classification for the Canadian boreal forest region was derived by a cluster analysis based on the probability estimates. (Copyright (c) IAVS: Opulus Press Uppsala. Printed in Sweden, 1993.)