Pre-industrial landscape composition patterns and post-industrial changes at the temperate-boreal forest interface in western Quebec, Canada

QuestionsWhat were the pre-industrial forest landscape composition patterns? Which factors had structured the pre-industrial landscape patterns? How have pre-industrial landscape patterns and post-industrial disturbances controlled composition changes? LocationAn area of 4175km(2) at the temperate-boreal forest interface of southwest Quebec, Canada. MethodsReconstruction of the pre-industrial composition is based on an original early land survey data set (1874-1935). Composition changes were computed by comparing historical data with modern forest inventories. Landscape-scale patterns and composition changes were assessed through spatially constrained clustering analysis. ResultsPre-industrial forest composition was structured across the landscape by the combination of environmental gradients (topography, deposits, drainage, etc.) and recurrence of fire. Frequency and intensity of fires were most likely the main drivers of forest dynamics and composition across the landscape. Black spruce (Picea mariana) and balsam fir (Abies balsamea) dominated hilly areas affected by former fires; aspen (Populus tremuloides) dominated lowlands following recent fire. White cedar (Thuja occidentatlis) and pines (Pinus spp.) dominated areas probably affected by small surface fires. New disturbance regimes that were subsequently incurred by human activities have shifted the pre-industrial landscape mosaic and have led to the current landscapes. Composition changes included a replacement of conifers by early successional species within settled or burned areas, and the maintenance of conifers and an increase in cedar dominance in areas affected by partial disturbance. ConclusionsPost-industrial composition changes must be perceived as complex interactions between pre-industrial landscape patterns and natural and human disturbances. Such land-use legacies could be important drivers of future landscape change and should be investigated and considered when predicting future climate-induced ecological changes.