Excerpt from Predicting Behavior and Size of Crown Fires in the Northern Rocky Mountains Figure 1 - Variation in rate of spread exhibited by running crown fires. The Mack Lake fire, a plume-dominated fire, is shown as a solid line, and the Sundance fire. A wind-driven fire, is shown as a dashed line. As the name implies, a crown fire is a fire carried through the crowns of living forests. Before reaching this condition, a fire can go through several stages of development. Typically, a fire may Spread for some time in sur face fuels such as grass, forest litter, or shrubs, without interacting with the overstory. It may even smolder in forest duff for days or weeks until burning conditions improve and the fire becomes active and begins to Spread. Beighley and Bishop (1990) provide an excellent description of the transition from surface fire to crown fire in high-elevation forests. Favor able conditions for a crown fire include. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.

Fire managers are increasingly concerned about the threat of crown fires, yet only now are quantitative methods for assessing crown fire hazard being developed. Links among existing mathematical models of fire behavior are used to develop two indices of crown fire hazard-the Torching Index and Crowning Index. These indices can be used to ordinate different forest stands by their relative susceptibility to crown fire and to compare the effectiveness of crown fire mitigation treatments. The coupled model was used to simulate the wide range of fire behavior possible in a forest stand, from a low-intensity surface fire to a high-intensity active crown fire, for the purpose of comparing potential fire behavior. The hazard indices and behavior simulations incorporate the effects of surface fuel characteristics, dead and live fuel moistures (surface and crown), slope steepness, canopy base height, canopy bulk density, and wind reduction by the canopy. Example simulations are for western Montana Pinus ponderosa and Pinus contorta stands. Although some of the models presented here have had limited testing or restricted geographic applicability, the concepts will apply to models for other regions and new models with greater geographic applicability.