Derivation of diameter measurements for buttressed trees, an example from Gabon

Abstract

Many tropical tree species have buttresses at the standard breast height (1.3 m above ground) of diameter measurement, with a presumable role in improving nutrient acquisition or tree anchorage in the ground (Newbery et al. 2009, Richter 1984). Measuring the diameter using standard dendrometrical tools such as callipers or graduated tapes, which require that the cross-section of the trunk has a convex shape, is then impossible (Nogueira et al. 2006). The recommended method in this case is to measure the diameter above the buttress (DAB), thus possibly leading to biased estimates of the basal area (West 2009), of tree above-ground biomass (Dean & Roxburgh 2006, Dean et al. 2003) and of tree growth (Metcalf et al. 2009). As an alternative, one can measure the basal area at breast height of buttressed trees, using a method that can deal with the irregular non-convex shape of the cross-section of the stem such as the Picus calliper, photogrammetry or 3D laser scanning (Badia et al. 2003, Dean 2003, Newbery et al. 2009).

On the geometry and allometry of big-buttressed trees - a challenge for forest monitoring: new insights from 3D-modeling with terrestrial laser scanning

“…5. These results are consistent with the findings by Ngomanda et al (2012), who measured the buttress perimeter with a wire. As there is visual evidence of heteroscedasticity, linear models were fit to the log-transformed variables.…”

“…According to Ngomanda et al (2012), we expect that such allometric relationships can be derived with reasonable model accuracy also for irregularly shaped large trees, either using a buttress form factor (as introduced here) or by using the diameter above buttress and/or the length of the convex hull at 1.3 m height as input variables. However, any measurement taken from such trees in the field is difficult to obtain.…”

“…Measuring the DBH of these trees is practically impossible and actually counterproductive, because a proper interpretation of such a measurement is not possible as of yet (Ngomanda et al 2012). Commonly, a diameter above buttress (DAB) is measured where the cylindrical bole of the tree starts (Clark & Clark 2000, Clark 2002, Basuki et al 2009, Metcalf et al 2009).…”

“…The measurement of the crosssectional area for buttressed parts of the trunk with conventional techniques is difficult (Ngomanda et al 2012) and precise volume estimates of the buttressed stem section for larger trees are rare and often based on destructive techniques (Nogueira et al 2006).…”

Ecological Structure and Prediction Equations for Estimating Tree Age, and Dendometric Parameters of <i>Acacia senegal</i> in the Senegalese Semi-Arid Zone—Ferlo

“…Crown ratio was estimated as the crown diameter divided by total tree height. Stem diameter (D) at breast height at the standard of 1.37 m above ground level [25,26], was taken by measuring the circumference (C) of the stem. The stem diameter was calculated as follows: C = D × π, D =C/π, where π = 22/7.…”