Changes in the Fire Regime and the Relative of Role Fuel and Climate of a Historically Flammability Limited Watershed in the Western Cascades as it Responds to Two Possible Future Climate Scenarios
| Author | : Jonathan Gendron |
| Publisher | : |
| Total Pages | : 0 |
| Release | : 2022 |
| Genre | : Climatic changes |
| ISBN | : |
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Anthropogenic climate change has shifted forest fire regimes in the Pacific Northwest U.S by increasing wildfire frequency and area burned and the shift is projected to continue during the 21st century if temperature and summertime aridity continually increase. Such changes threaten natural resources in these systems, including drinking water reservoirs, which could see reduced water quality during post-fire recovery. Productive forests with historically flammability-limited wildfire regimes are susceptible to large-scale high-severity events because of large fuel sinks; therefore, as flammability increases with climate change, the frequency of these events is also expected to increase. However, it is unclear how climate change and wildfire will alter long-term fuel availability in these forests; if a strong fuel limitation develops, it could potentially offset increases in fuel flammability. Herein, we apply RHESSys-WMFire, a process-based ecohydrological framework coupled with a stochastic fire-spread model and a post-fire effects model, to explore the long-term coevolution of climate, vegetation, and wildfire in a historically climate-limited forest in the western cascades as it responds to two future climate scenarios: (1) one that enforces extreme fire-weather, and (2) one that is less arid and more suitable for forest production. Both scenarios feature three 525-year climate sequences to capture the co-evolution of vegetation and fire behavior for three stable climate regimes: the present, near future (2040s), and distant future (2070s). Each sequence was constructed from 30 years of climate data from existing CMIP5 GCM using a randomized climate resampling technique. We found both climate storylines forced a fuel limitation that increased during the 21st-century; however, increases in fuel flammability were greater, and resulted in increases in wildfire size, frequency, and area burned in near and distant future relative to the present. The severity of fuel limitation also corresponded with shifts in the fire-size distribution and the fire recurrence interval of different elevations, wherein strong fuel limitation caused relatively smaller fires and lower frequency. We surmise that reduced fuel availability will scale with the severity of climate forcing; however, in forests where fuel flammability is presently low, it will begin to limit wildfire behavior until a certain threshold has been reached.
