Simulated fire behaviour in young, postfire lodgepole pine forests.

Early-seral forests are expanding throughout western North America as fire frequency and annual area burned increase, yet fire behaviour in young postfire forests is poorly understood. We simulated fire behaviour in 24-year-old lodgepole pine (Pinus contorta var. latifolia) stands in Yellowstone National Park, Wyoming, United States using operational models parameterised with empirical fuel characteristics, 50-99% fuel moisture conditions and 1-60 km hr^-1 open winds to address two questions: [1] How does fireline intensity and crown fire initiation and spread vary among young, lodgepole pine stands? [2] What are the contributions of fuels, moisture and wind on fire behaviour? Sensitivity analysis indicated the greatest contributors to output variance were stand structure mediated wind attenuation, shrub fuel loads and 1000-h fuel moisture for fireline intensity; crown base height for crown fire initiation and crown bulk density and 1-h fuel moisture for crown fire spread. Simulation results predicted crown fire (e.g. passive, conditional or active types) in over 90% of stands at 50th percentile moisture conditions and wind speeds greater than 3 km hr^-1.We conclude that dense canopy characteristics heighten crown fire potential in young, postfire lodgepole pine forests even under less than extreme wind and fuel moisture conditions. [ABSTRACT FROM AUTHOR]