Biogeosciences, 14, 3873-3882, 2017
https://doi.org/10.5194/bg-14-3873-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
31 Aug 2017
Fire-regime variability impacts forest carbon dynamics for centuries to millennia
Tara W. Hudiburg1, Philip E. Higuera2, and Jeffrey A. Hicke3 1Department of Forest, Rangeland, and Fire Sciences, University of Idaho, 875 Perimeter Dr., Moscow, ID 83844-1133, USA
2Department of Ecosystem and Conservation Sciences, University of Montana, 32 Campus Dr., Missoula, MT 59812, USA
3Department of Geography, University of Idaho, 875 Perimeter Dr., Moscow, ID 83844-3021, USA
Abstract. Wildfire is a dominant disturbance agent in forest ecosystems, shaping important biogeochemical processes including net carbon (C) balance. Long-term monitoring and chronosequence studies highlight a resilience of biogeochemical properties to large, stand-replacing, high-severity fire events. In contrast, the consequences of repeated fires or temporal variability in a fire regime (e.g., the characteristic timing or severity of fire) are largely unknown, yet theory suggests that such variability could strongly influence forest C trajectories (i.e., future states or directions) for millennia. Here we combine a 4500-year paleoecological record of fire activity with ecosystem modeling to investigate how fire-regime variability impacts soil C and net ecosystem carbon balance. We found that C trajectories in a paleo-informed scenario differed significantly from an equilibrium scenario (with a constant fire return interval), largely due to variability in the timing and severity of past fires. Paleo-informed scenarios contained multi-century periods of positive and negative net ecosystem C balance, with magnitudes significantly larger than observed under the equilibrium scenario. Further, this variability created legacies in soil C trajectories that lasted for millennia. Our results imply that fire-regime variability is a major driver of C trajectories in stand-replacing fire regimes. Predicting carbon balance in these systems, therefore, will depend strongly on the ability of ecosystem models to represent a realistic range of fire-regime variability over the past several centuries to millennia.

Citation: Hudiburg, T. W., Higuera, P. E., and Hicke, J. A.: Fire-regime variability impacts forest carbon dynamics for centuries to millennia, Biogeosciences, 14, 3873-3882, https://doi.org/10.5194/bg-14-3873-2017, 2017.
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Short summary
Wildfire is a dominant disturbance agent in forest ecosystems, shaping important processes including net carbon (C) balance. Our results imply that fire-regime variability is a major driver of C trajectories in stand-replacing fire regimes. Predicting carbon balance in these systems, therefore, will depend strongly on the ability of ecosystem models to represent a realistic range of fire-regime variability over the past several centuries to millennia.
Wildfire is a dominant disturbance agent in forest ecosystems, shaping important processes...
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