OOS 17-5 - Can managing for fire refugia slow 21st century forest change? A simulation study in Greater Yellowstone

Subalpine forests in the western US are at risk of fire-driven conversion to nonforest with far reaching consequences for wildlife and ecosystem services. As fire activity increases, greater distances to live seed sources and elevated immaturity risk jeopardize postfire tree regeneration. Islands of unburned forest within burn perimeters enhance postfire recovery, but it is unknown if managing some forest stands as fire refugia that persist through successive fire events could enhance postfire tree regeneration and slow fire-driven forest loss. Simulation models are powerful tools to explore alternative management scenarios across large spatial and temporal scales, and results may inform when and where to resist, accept, or direct changes driven by novel fire regimes. We used the individual-based forest disturbance simulation model iLand to ask how fire refugia shape postfire forests recovery in Grand Teton National Park, Wyoming, USA. Our objectives were to determine (1) whether landscapes with refugia experience higher postfire forest recovery and retain greater forest extent by the end of the 21st century compared to landscapes without refugia, (2) how postfire forest recovery and forest extent vary with different climate scenarios, and (3) what amount and configuration of forest managed as fire refugia maximizes and prolongs potential positive impacts of fire refugia. Results suggest that fire refugia have little effect on postfire forest recovery or forest extent if fire stays within the historical range of variation (HRV). However, in a warmer and drier climate with fire that exceeds the HRV, fire refugia can slow the rate of forest loss at least through mid-century. For fire refugia to be an effective management strategy, a high proportion of forest would need to be maintained as refugia. Resisting change by managing forest stands of high conservation value as fire refugia may sustain valuable habitat and increase tree regeneration in surrounding burned areas by providing live seed sources. While fire refugia do not confer stasis to a landscape, they can curb the rate of change and buy ecosystems time to adjust to a warmer world with more fire.