U.S. Joint Fire Science Program


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Alexander, M.E.; Cruz, M.G.; Vaillant, N.M.; Peterson, D.L. 2013. Crown fire behavior characteristics and prediction in conifer forests: a state-of-knowledge synthesis. Joint Fire Science Program, Boise, Idaho. JFSP 09-S-03-1 Final Report. 39 p.


US government work.


Joint Fire Science Program (JFSP) project 09-S-03-1 was undertaken in response to JFSP Project Announcement No. FA-RFA09-0002 with respect to a synthesis on extreme fire behavior or more specifically a review and analysis of the literature dealing with certain features of crown fire behavior in conifer forests in the United States and adjacent regions of Canada. The key findings presented are organized along nine topical areas: types of crown fires; crown fire initiation; crown fire propagation; crown fire rate of spread; crown fire intensity and flame zone characteristics; crown fire area and perimeter growth; crown fire spotting activity; models, systems, and other decision aids for predicting crown fire behavior; and implications for fire and fuel management. A total of 16 management implications are discussed at some length, involving the following subjects: • Classification of crown fires • Flames don’t have to extend into the lower canopy for crowning to occur • Unsubstantiated coupling of crown fire behavior models • Defining canopy fuel stratum characteristics • Evaluating models to predict canopy fuel stratum characteristics • The myth of the “crown fire-proof” conifer forest • Lack of physics-based model evaluation in predicting crown fire behavior • Van Wagner’s criteria for active crown fire spread is a robust concept • Foliar moisture content has little or no effect on crown fire rate of spread • Surface fire versus crown fire rates of spread prediction • An example of linking surface and crown fire behavior to fire effects • Model of elliptical crown fire length-to-breadth ratio underpredicts • Maximum spotting distance model for active crown fires • Reviews on predicting crown fire and wildland fire behavior have proven valuable • Alternative models for predicting the characteristics of crown fire behavior • Evaluation of fuel treatment effectiveness From the standpoint of relationships to other recent findings on the topic of crown fire behavior in conifer forests, four areas of ongoing work were identified: • Crown fire potential in mountain pine beetle-attack lodgepole pine forests • Physics-based fire behavior models • Crown fire potential in other forest types • Experimental crown fires From a practical point of view, future work is needed in the following areas: • Systematic documentation of crowning wildfires for model evaluation purposes • Development and testing of flame size model for crown fires • Defining the threshold for vertical fire spread in terms of ladder/bridge fuels and canopy bulk density • Crown fuel consumption data collection and model evaluation • Application of ensemble or multiple simulation methods to the prediction of crown fire behavior The following type/number of deliverables emanated from Project JFSP 09-S-03-1: • Book chapters – 5 • Special issue of Fire Management Today - 1 • Journal articles – 16 • Conference papers and technical journal notices - 13 • Software – 2 • Workshop – 1 • Other contributions – 7 • Websites – 2 Collectively, the references associated with the book chapters and journal articles, constitutes a comprehensive bibliography on the subject of crown fire behavior in conifer forests.