Allometric equations for crown fuel biomass of Aleppo pine (Pinus halepensis Mill.) in Greece

Abstract

Allometric equations for the estimation of crown fuel weight of Aleppo pine (Pinus halepensis Mill.) trees in the Mediterranean Basin were developed. Forty trees were destructively sampled and their crown fuels were weighed separately for each fuel category. Crown fuel components, both living and dead, were separated into size classes and regression equations that estimate crown fuel load by diameter class were derived. The allometric equation y = ax^b with diameter at breast height as the single predictor was chosen, because the addition of other parameters did not decrease the residual sum of squares significantly. The adjusted coefficient of determination (R²_adj) values were high (R²_adj = 0.82–0.88) in all cases. Diameter at breast height was the most significant determinant of crown fuel biomass. The aerial fuels that are consumed during crown fires (i.e. needles and twigs with diameter less than 0.63 cm) comprised 29.3% of the total crown weight. Live fuels constituted ~96.3% of total crown biomass, distributed as follows: needles 16.7% (average load 12.07 kg), branches with 0.0–0.63-cm diameter 12.6% (average load 9.18 kg), 0.64–2.5-cm diameter 37.3% (27.99 kg), 2.51–7.5-cm diameter 25.4% (18.59 kg), and >7.5-cm diameter 3.7% (2.65 kg). The equations provide quantitative fuel biomass attributes for use in crown fire behaviour models, fire management and carbon assessment in Aleppo pine stands.