The Fire and Fuels Extension (FFE) to the Forest Vegetation Simulator (FVS) integrates elements of existing fire behaviour and fire effects models (such as FIREMOD and FOFEM) with the ability of FVS to simulate tree growth and mortality and stand management. The model predicts the actual or potential effects of a fire in a stand. It does not simulate the spread of a fire within a stand or between stands, and it cannot predict the likelihood of a fire.
The FFE-FVS model consists of several components: sub-models that simulate the dynamics of live trees, fuels, and fire effects. The main FVS model maintains the live trees and simulates natural growth and mortality along with the impacts of silvicultural activities. The FFE tracks snags (standing dead trees) and woody debris (logs or tree parts on the ground). Snags may be created through stand management activities or through tree mortality. As they age, snags lose their crown, break, and fall down to become woody debris. Woody debris is also created through crown loss from live trees and through the addition of debris from management actions. This dead organic matter decays over time, with rates that depend on the size and type of material and the stand’s habitat type. As well as all the standard silvicultural management options that are part of FVS, the FFE contains specific options for managing snags and woody debris, such as salvage logging and mechanical treatment of snags and yarding waste.
The FFE can simulate actual or potential fire behaviour and effects, including fuel consumption, crowning, tree mortality and smoke production. If desired, the FFE will simulate the actual effects of stand fire, consuming woody debris and crowns, killing trees, producing smoke and changing the stand’s structure. Alternatively, the FFE can predict the potential effect of two different types of fire. In this case, the model will produce output on the potential mortality, fuel consumption, smoke production, and will produce indices of crowning potential.
The FFE can also account for and report on stand carbon stocks and fluxes, separately tracking living and dead biomass and carbon in above- and below-ground pools. Two stand carbon accounting methodologies are available to model users for this purpose. When stand entries are made and harvested products leave the stand, the C accounting system can also optionally track the fate of the merchantable biomass C over time, as it enters a variety of end-use categories. The methodology for end-use tracking involves partitioning the harvested products into hardwood/softwood and pulpwood/sawlog categories, each with unique C retention characteristics in different geographic regions of North America.
The FFE was created in cooperation with scientists and others from the USFS and has been linked to all western and most eastern FVS variants, using regional rules and parameter sets.
An overview of the FFE model components and linkages