In this version of FARSITE, all canopy characteristics except cover are considered uniform across the landscape except where crown fuel characteristics have been specified in a GIS data theme (see Input > Landscape Utilities > Generate Landscape File). This is unrealistic of course, but to simulate crown fire without spatial canopy data themes on height, height to live crown base, crown bulk density, you would have to provide a constant map theme for each of these variables anyway.
The canopy characteristics dialog box allows you to select these uniform canopy characteristics used for crown fire calculations (tree height, height to live crown base, crown bulk density, and foliar moisture content). These values will be used for any crown fire parameter not contained in the Landscape (.LCP) File.
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Height - The average height of the top of the canopy. Used as a starting point for embers, calculating wind reductions, and computing volume of crown fuels. Crown Base - Crown Base Height (CBH), the height to the bottom of the live crown over the area. CBH should incorporate the effects of ladder fuels. Bulk Density - Crown Bulk Density (CBD), is the density of available crown fuels on a stand or area basis. Foliar MC - Foliar Moisture Content, the moisture content of the coniferous crown fuels. Not necessarily the same as live fuel moisture. Diameter - Average DBH of trees expected to torch. Species - Species of trees expected to torch. Tolerance - The shade tolerance of the torching trees. |
IMPORTANT NOTE: For calculating crown fire spread, you have the option of using the spatial canopy cover theme to modify the constant crown bulk density value in this dialog box (see Model > Fire Behavior Options)
Parameters that affect spotting from torching trees (if torching occurs) are tree diameter and species. These parameters only determine the characteristics of trees that torch and produce embers if torching occurs (see Spotting in the technical documentation)