Adequate quantification of canopy fuel load and canopy bulk density is required for assessment of the susceptibility of forest stands to crown fire and evaluation of silvicultural treatments aimed at reducing the risk of crowning. The use of tree biomass equations and vertical profile distributions of crown fuels provide the most accurate estimates of the canopy fuel characteristics. In this study, 100 pole-size maritime pine (Pinus pinaster Aiton) trees were destructively sampled in five different sites, covering a wide range of its geographical distribution in the Iberian Peninsula. To estimate crown fuel mass, allometric equations were fitted separately for needles, twigs, and fuel available for crown fire. Models were also fitted to characterize the vertical fuel distributions as a function of tree height. All models were fitted simultaneously to guarantee additivity among tree biomass components, and corrections were also made for heterocedasticity and autocorrelation. Diameter at breast height was the best explanatory variable for all the allometric models. The vertical distribution of crown biomass fractions along tree height depended on the crown size and tree dominance. The system of equations provides a good balance between accurate predictions and low data requirements, allowing quantification of canopy fuel characteristics at stand level.
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