Allometric equations for estimating canopy fuel load and distribution of pole-size maritime pine trees in five Iberian provenances

Abstract

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.

Compatible System for Predicting Total and Merchantable Stem Volume over and under Bark, Branch Volume and Whole-Tree Volume of Pine Species

“…As commonly found for branch components, the precision was lower, with R 2 values of respectively 0.65 and 0.7 for P. cooperi and P. durangensis. Similar R 2 values for branch biomass prediction are commonly reported in the literature (e.g., [11][12][13]49,[64][65][66]). Tree branches are widely acknowledged to be difficult to model [67].…”

Characterizing crown fuel distribution for conifers in the interior western United States

“…This effect presumably arises from the increased shading of lower branches in dense stands. Similarly, upward-shifted foliage distributions are frequently reported for trees in subordinate social positions (e.g., Maguire and Bennett 1996;Gilmore and Seymour 1997;Mäkelä and Vanninen 2001;Garber and Maguire 2005;Jiménez et al 2013; but see Weiskittel et al (2009)). This is likely a similar plastic response of within-crown foliage distribution to light competition.…”

Forest fire severity in NW Spain: a case of study

“…ELEV_MAX variable was positively correlated to canopy height (Andersen et al, 2005), so looking at table 4 one can say that, under the same under conditions, high severity fire tended to occur more frequently in lower (i.e younger) stands. Studies in maritime pine stands for the same area (Jimenez et al 2013, Fernandez-Alonso et al 2013, Gomez-Vazquez et al 2013 have shown that there is a positive correlation between mean stand height or dominant height and canopy base height (CBH). Thus, higher stands may have also higher CBH values and therefore, lower possibilities of crown fire occurrence.…”

“…That type of stand replacement fires means a challenge for fire managers: they pose an important risk to population and firefighting crews due to difficulty to suppress them. They also are a threat to forest production by removing much or the entire tree canopy in a particular area, and resulting in considerable C emissions (Jimenez et al 2013). They reset the successional and growth processes of stands and forests (Graham et al, 2004) and can change post-fire dominant vegetation type (Holden, 2009).…”