Are historical fire regimes compatible with future climate? Implications for forest restoration

The restoration of historical fire regimes is often a primary objective in the conservation of fire-adapted forests. However, individual species' responses to future climate change may uncouple historical vegetation-disturbance relationships, producing potentially negative ecological consequences to fire restoration. We used a landscape simulation model to assess how forest pattern will respond to-future climate regimes and whether the restoration of historical fire regimes will benefit forest conservation under future climate regimes. Our study landscape was the 335,000-ha Kaibab Plateau at the North Rim of the Grand Canyon spanning a broad elevation-vegetation gradient of pinyon-juniper, ponderosa pine, mixed conifer, and spruce-fir forests along with a range of associated fire regimes. We employed a novel multimodel landscape simulation approach using the Climate-Forest Vegetation Simulator to estimate individual tree species climate responses and LANDIS-II to simulate spatial patterns of fire disturbance, forest growth, regeneration, succession, and dispersal. Model simulations included three climate scenarios (no change, moderate change, and high change) and two fire scenarios (fire exclusion and fire restoration). The climate change scenarios produced declines in mean forest aboveground biomass (AGB) and a compositional turnover equal to one or two vegetation zones, approximating the vegetation displacement that occurred in this location during the Holocene. Fire restoration resulted in earlier, but roughly equivalent, AGB declines and compositional change. Uphill species migration in some elevation zones produced tree species-fire regime mismatches that promoted state changes and increased nonforest area. Regardless of fire management approach, our simulations project that the Kaibab Plateau will eventually be dominated by pinyon-juniper, oak, and ponderosa pine forest types, with a complete loss of mesic conifer species. Our results indicate that fire managers will have to be flexible with the application of historical fire regimes to avoid regeneration failures and abrupt declines in biomass.