An integrated model of stand dynamics, soil carbon and fire regime : pplications to boreal ecosystem response to climate change

Authors: Miquelajauregui Graf, Yosune
Advisor: Cumming, Steven G.Gauthier, Sylvie
Abstract: Boreal black spruce forests (Picea mariana (Mill.) BSP) store great amounts of carbon in the living biomass and in the soil. Fire regime characteristics (e.g. fire return interval, fire intensity, fire season and severity) play a central role in the storage and flow of carbon, by modifying the distribution and transfer of material among pools. There is little doubt in the scientific community that climate change will cause changes in the temporal and spatial variables that control the frequency and severity of fires. A demographic diameter-class structured model was developed to simulate boreal carbon storage under different fire regimes. This approach incorporates the effect of fire intensity and stand structure measures to simulate fire severity, measured as the proportion of overstory tree mortality. The model allows quantifying and mapping average regional estimates of current and future carbon stocks for the black spruce-feathermoss bioclimatic domain of northern Québec. Simulation results suggest that fire severity increases with fire the intensity. Stand structure is one of the factors that explains the observed variation in boreal fire severity. We simulated carbon stocks and fluxes under seven levels of fire return interval (FRI) and two fire seasons. We tested for an effect of these parameters on average carbon stocks. Carbon stocks were sensitive to IRF's between 60 and 300 years. Soil C stocks were lower for summer fires that occurred during shorter IRF. Finally, we investigated the short-term impacts of climate change under four climatic periods: 1980-2010, 2010-2040, 2040-2070 and 2070-2100. Historical and future FRI maps and historical and forecasted weather data estimated by CanESM2 RCP8.5 were used to drive the growth of forests, decomposition rates, fire regime and C dynamics. In our simulation experiments, the accumulation of carbon in the ecosystem was reduced by 11% by the end of 2100. The results of this study suggest that black spruce forest could be losing their capacity to sequester and store organic C over the next coming decades due to climate change effects on the fire regime and on forest growth.
Document Type: Thèse de doctorat
Issue Date: 2017
Open Access Date: 24 April 2018
Grantor: Université Laval
Collection:Thèses et mémoires

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