We analyzed the factors limiting the distribution of the white spruce (Picea glauca) in North America and the ecological amplitudes of the species in relation to these factors. Based on these data, an ecogeographical model of spruce dispersal was built. It is shown that the northbound dispersal of White Spruce in North America is limited by heat supply. The species range is shaped at the southwestern border (from the central part to the Rocky Mountains) by the lack of humidification and at the southeastern border, presumably, by competitive relations with foliar edificators. For P. glauca, the northern limit of heat supply is about 1200°C. At the southern border of the range, the White Spruce has low competitive ability with deciduous trees, starting approximately from the sum of active temperatures of about 3000°C. The limits of species dispersal in arid zones are determined by the hydrothermal coefficient, the value of which should not exceed 1.2. Validation of the dispersion model for P. glauca shows a discrepancy between the actual and model range of ±50–100 km. Formerly unknown populations of P. glauca may be found, as affirmed by a new records of the White Spruce in the Noatak National Park, within the discrepancy zone, between the potential range and that ascertained by Little (1971). We compared the ecological boundaries of P. glauca dispersal with those boundaries of the genus Picea in Eurasia. It was found that ecogeographical model designed for P. glauca describes
the dispersal of Eurasian spruce species with high accuracy. This was evidence that the ecological divergence between North American and Eurasian spruce species was not strong. Deviation of the modeling results for the White Spruce from the actual Eurasian spruce range was observed in the regions with permafrost and some others. Therefore, additional environmental factors are required for the ecogeographical model upon its introduction to another continent.