The Forest Vegetation Simulator was integrated with the FSim wildfire simulation model to conduct research on long term management and wildfire feedbacks.
Forest landscape models (FLMs) are important tools used to address a wide range of forest management policy tradeoffs on public and private forests. Several recent studies using FLMs have examined the effects of forest and fuels management on future wildfire activity, carbon, water yield, resiliency, and other forest metrics. Studying longer-term (e.g. > 20 years) dynamics between management and disturbances can reveal ecosystem tipping points, feedbacks, and unintended consequences of management activities that are not otherwise observable. Most recently, applications of FLMs have provided insights on the potential effects of management on future fire and forest composition under a range of climate change scenarios. Many of these studies in the US have used portions of the large (76 million ha) national forest network as study areas where wildfires are increasingly impacting ecosystem services and burning into adjacent developed areas. In this study, we are applying a new FLM, LSim, to examine a wide range of wildfire and foest management issues on western US landscapes.
We developed and applied a new FLM, LSim, that integrates the Forest Vegetation Simulator (FVS), with the large-fire simulation model FSim. The resulting LSim model has the functionality to simulate spatially coordinated forest management over time under a background of large stochastic wildfires with models that have undergone decades of field application. This is in contrast to other FLMs that have yet to be used to guide site specific management activities as part of forest and fuels management on national forests. The LSim model provides a platform to simulate detailed prescriptions developed by silviculturalists in the field as part of forest landscape management projects.
We applied the model to the Deschutes National Forest in central Oregon, USA, to study how accelerated forest restoration might affect future wildfire area burned, fire severity, fire exposure to the wildland urban interface (WUI) and commercial timber production. We are also applying the model to national forests in the Blue Mountains in eastern Oregon to study the effect of climate change on future fire. A third study area is in northern Arizona examining alternative restoration and fire management strategies through time on fire behavior.
- Restoration treatments over time had a large effect on fire severity, reducing potential flame length by 45% for the study area within the first 20 years, whereas reductions in area burned were relatively small.
- Although wildfire contributed to reducing flame length over time, area burned was only 16% of the total disturbed area (managed and burned with prescribed fire) under the 3x management intensity.
- Interactions among spatial treatment scenarios and treatment intensities were minimal, although inter-annual and among-replicate variability was extreme, with the former coefficient of variation in burned area exceeding 200%.
- We also observed simulated fires that exceeded four times the historically recorded fire size. Fire regime variability has manifold significance since very large fires can homogenize fuels and eliminate clumpy stand structure that historically reduced fire size and maintained landscape resiliency.
- We discuss specific research needs to better understand future wildfire activity and the relative influence of climate, fuels, fire feedbacks, and management to achieve fire resiliency goals on western US fire frequent forests.