Landscape-scale changes in canopy fuels and potential fire behaviour following ponderosa pine restoration treatments.

We evaluated canopy fuels and potential fire behaviour changes following landscape-scale restoration treatments in a ponderosa pine forest at Mt Trumbull, Arizona, USA. The goal of the project was to restore historical forest structure by thinning and burning, thereby reducing canopy fuels and minimising active crown fire potential. We measured 117 permanent plots before (1996-97) and after (2003) treatments. The plots were evenly distributed across the landscape and represented an area of ~1200 ha, about half of which was an untreated control. We compared canopy fuel estimates using three different methods to assess whether fire behaviour modelling outputs were sensitive to the choice of canopy fuel equation. Treatments decreased canopy fuel load by 43-50% from 0.77-1.83 kg m^-2 to 0.44-0.91 kg m^-2 (the range of values reflects the different canopy fuel equations) and decreased canopy bulk density by 42-61% from 0.038-0.172 kg m^-3 to 0.022-0.067 kg m^-3 in the treated area, while slight increases occurred in the control. We applied two fire models to estimate potential fire behaviour: FlamMap and NEXUS. These models differ in several important features but predicted outcomes were consistent: under extreme drought and wind conditions, the proportion of the landscape susceptible to active crown fire decreased in the treated area while little change occurred in the control. [ABSTRACT FROM AUTHOR]