This study aims to demonstrate that contemporary landscape vegetation heterogeneity is controlled by a combination of natural disturbances with other sets of explanatory variables. Integration of these drivers should be considered the key to explaining vegetation changes along ecological gradients characterizing the boreal forest. Forest inventory plots and maps produced from about 1970 to 2000 were used to characterize a large area (175 000 km2) according to 3 vegetation themes constituting distinct aspects of forest community composition (tree species, forest types, and potential vegetation–successional stages) and 4 sets of explanatory variables (climate, natural disturbances, physical environment, and human disturbances). Canonical ordinations were performed to define ecological gradients as well as the overlap between vegetation themes and sets of explanatory variables along each gradient. For each vegetation theme, we quantified the relative proportion of vegetation variation explained by unique as well as combined sets of explanatory variables. The landscape vegetation heterogeneity described by species and potential vegetation–successional stage was mostly explained by natural disturbances and climate in association with other sets of explanatory variables. The influence of physical environment was higher for landscape vegetation heterogeneity related to forest types than for the other themes, but this theme also was dominated by natural disturbances and climate. Compared to natural sets of explanatory variables, human disturbances played a secondary but significant role in the 3 vegetation themes. This research contributes to a better understanding of the relationship between vegetation and the factors underlying its development in the boreal forest and represents an important step toward ecosystem-based management.