A simplified, physiologically based (3-PG) model was used to evaluate the effects of spatial variation in climate and soils on the potential productivity of Eucalyptus nitens Deane and Maiden (Maiden). The model was parameterized based on the physiology of E. nitens to predict potential productivity and leaf area index as influenced by environmental factors. Data obtained from conventional weather stations were utilized by the 3-PG model to predict productivity site classes. A final plantation suitability grid was mapped to show areas of the region with productivity classes predicted to be very high (> 52 m(3) ha(-1) year(-1)), high (47.5-52 m(3) ha(-1) year(-1)), moderate (45-47.5 m(3) ha(-1) year(-1)), low (35-45 m(3) ha(-1) year(-1)) and very low (< 35 m(3) ha(-1) year(-1)). The lowest potential productivity was attributable to soil water and nutrients limitations. A process-based forest growth model that can be widely extrapolated using geographic information system is particularly useful to screen areas as prospective plantation sites.