Abstract
The fuel complex variables canopy bulk density and canopy base height are often used to predict crown fire initiation and spread. Direct measurement of these variables is impractical, and they are usually estimated indirectly by modelling. Recent advances in predicting crown fire behaviour require accurate estimates of the complete vertical distribution of canopy fuels. The objectives of the present study were to model the vertical profile of available canopy fuel in pine stands by using data from the Spanish national forest inventory plus low-density airborne laser scanning (ALS) metrics. In a first step, the vertical distribution of the canopy fuel load was modelled using the Weibull probability density function. In a second step, two different systems of models were fitted to estimate the canopy variables defining the vertical distributions; the first system related these variables to stand variables obtained in a field inventory, and the second system related the canopy variables to airborne laser scanning metrics. The models of each system were fitted simultaneously to compensate the effects of the inherent cross-model correlation between the canopy variables. Heteroscedasticity was also analyzed, but no correction in the fitting process was necessary. The estimated canopy fuel load profiles from field variables explained 84% and 86% of the variation in canopy fuel load for maritime pine and radiata pine respectively; whereas the estimated canopy fuel load profiles from ALS metrics explained 52% and 49% of the variation for the same species. The proposed models can be used to assess the effectiveness of different forest management alternatives for reducing crown fire hazard.
Highlights
Accurate knowledge of fuel characteristics has been shown to be critical in forest fire management, as fuel constitutes a primary component of fire risk [1,2]
canopy fuel load (CFL) is defined as the mass of available canopy fuel per unit ground area; canopy bulk density (CBD) indicates the amount of available fuel per volume unit in the aerial layer, and canopy base height (CBH) is the lowest height above ground level at which there is sufficient available canopy fuel to propagate fire vertically through the canopy [2,5]
We aimed to model the vertical distribution of the available canopy fuel load in Pinus pinaster Ait. and Pinus radiata D
Summary
Accurate knowledge of fuel characteristics has been shown to be critical in forest fire management, as fuel constitutes a primary component of fire risk [1,2]. Crown fires are usually intense and spread rapidly, which makes them difficult and dangerous to suppress. They can cause severe economic damage and ecological disruption [4]. Assessing the risk of crown fire initiation and spread is a key element in gauging fire behaviour. Both crown fire initiation and spread are widely recognised to be determined by structural characteristics of the canopy fuel complex such as available canopy fuel load (CFL), canopy bulk density (CBD) and canopy base height (CBH) [4]. Needles and fine twigs are commonly considered available fuel because these tree biomass components are usually consumed within the flaming front of a crown fire [6]
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