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

Abstract

Questions: What 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?Location: An area of 4175 km 2 at the temperate-boreal forest interface of southwest Quebec, Canada.Methods: Reconstruction of the pre-industrial composition is based on an original early land survey data set . Composition changes were computed by comparing historical data with modern forest inventories. Landscapescale patterns and composition changes were assessed through spatially constrained clustering analysis.Results: Pre-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.Conclusions: Post-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.

The pyrogeography of eastern boreal Canada from 1901 to 2012 simulated with the LPJ-LMfire model

“…Therefore, it is difficult to determine the contribution of climate alone to fire activity in studies using observations collected since the second half of the 20th century. Furthermore, fire history studies rarely consider the feedback of fire on vegetation, mostly because historical data about vegetation composition are lacking (Danneyrolles et al, 2016). This is particularly true in the case of studies dealing with reconstructions of fire activity using dendrochronological evidence (e.g., Girardin et al, 2006) or adjusted empirical data sets (Van Wagner et al, 1987).…”

The pyrogeography of eastern boreal Canada from 1901 to 2012 simulated with the LPJ-LMfire model

“…Forest management has contributed to modifying the composition and distribution of forest fuels (Girardin and Terrier, 2015;Danneyrolles et al, 2016). However, alterations in fuel composition and structure that were induced by human activities are not implemented in the present LPJ-LMfire simulations.…”

“…Although it is also possible to investigate recent changes in fire regimes that are based upon observations collected over relatively short time intervals (< 100 years), reliable observations were not available in many boreal regions prior to the late 1960s (Podur et al, 2002). Furthermore, fire history studies rarely consider the feedbacks of 15 fires on vegetation, mostly because historical data about vegetation composition are lacking (Danneyrolles et al, 2016). This is particularly the case for studies dealing with reconstructions of fire activity using dendrochronological evidence (e.g., Girardin et al, 2006) or by adjusting empirical datasets (Van Wagner et al, 1987).…”

Tree Diseases as a Cause and Consequence of Interacting Forest Disturbances

“…Vegetation changes in response to environmental and social or economic dynamics can also shift species abundances and spatial distributions with no significant changes in the represented taxa. For example, in northern forests of Quebec, human impacts reflecting changes in economic factors and silvicultural practices could influence future likelihood of insect outbreak [30]. Plant invasions can also alter host populations at broad spatial scales.…”

“…In the absence of disease, disturbances play a critical role in structuring forest communities at local-to-landscape scales [17,30,39]. Ecological disturbances can alter any component of the disease triangle (Figure 1).…”