A 3D approach to model the taper of irregular tree stems: making plots biomass estimates comparable in tropical forests

Bauwens Sébastien, Ploton Pierre, Fayolle Adeline, Ligot Gauthier, Loumeto Jean-Joël, Lejeune Philippe, Gourlet-Fleury Sylvie. 2021. A 3D approach to model the taper of irregular tree stems: making plots biomass estimates comparable in tropical forests. Ecological Applications, 31 (8):e02451, 12 p.

Url - jeu de données - Entrepôt autre : http://hdl.handle.net/2268/262867

Quartile : Q1, Sujet : ECOLOGY / Quartile : Q1, Sujet : ENVIRONMENTAL SCIENCES

Liste HCERES des revues (en SHS) : oui

Thème(s) HCERES des revues (en SHS) : Economie-gestion

Résumé : In tropical forests, the high proportion of trees showing irregularities at the stem base complicates forest monitoring. For example, in the presence of buttresses, the height of the point of measurement (HPOM) of the stem diameter (DPOM) is raised from 1.3 m, the standard breast height, up to a regular part of the stem. While DPOM is the most important predictor for tree aboveground biomass (AGB) estimates, the lack of harmonized HPOM for irregular trees in forest inventory increases the uncertainty in plot-level AGB stock and stock change estimates. In this study, we gathered an original non-destructive three-dimensional (3D) data set collected with terrestrial laser scanning and close range terrestrial photogrammetry tools in three sites in central Africa. For the 228 irregularly shaped stems sampled, we developed a set of taper models to harmonize HPOM by predicting the equivalent diameter at breast height (DBH0) from a DPOM measured at any height. We analyzed the effect of using DBH0 on tree-level and plotlevel AGB estimates. To do so, we used destructive AGB data for 140 trees and forest inventory data from eight 1-ha plots in the Republic of Congo. Our results showed that our best simple taper model predicts DBH0 with a relative mean absolute error of 3.7% (R2 = 0.98) over a wide DPOM range of 17–249 cm. Based on destructive AGB data, we found that the AGB allometric model calibrated with harmonized HPOM data was more accurate than the conventional local and pantropical models. At the plot level, the comparison of AGB stock estimates with and without HPOM harmonization showed an increasing divergence with the increasing share of irregular stems (up to −15%). The harmonization procedure developed in this study could be implemented as a standard practice for AGB monitoring in tropical forests as no additional forest inventory measurements is required. This would probably lead to important revisions of the AGB stock estimates in regions having a large number of irregular tree stems and increase their carbon sink estimates. The growing use of three-dimensional (3D) data offers new opportunities to extend our approach and further develop general taper models in other tropical regions.

Mots-clés Agrovoc : biomasse aérienne des arbres, allométrie, dendrométrie, modélisation, forêt tropicale, tronc, parcelle

Mots-clés géographiques Agrovoc : Cameroun, République démocratique du Congo, Congo

Mots-clés libres : Allometry, Aboveground biomass, Buttress, Terrestrial photogrammetry, Terrestrial laser scanning

Classification Agris : K01 - Foresterie - Considérations générales
U10 - Informatique, mathématiques et statistiques

Champ stratégique Cirad : CTS 1 (2019-) - Biodiversité

Auteurs et affiliations

• Bauwens Sébastien, Université de Liège (BEL) - auteur correspondant
• Ploton Pierre, IRD (FRA)
• Fayolle Adeline, Université de Liège (BEL)
• Ligot Gauthier, Université de Liège (BEL)
• Loumeto Jean-Joël, UMNG (COG)
• Lejeune Philippe, Université de Liège (BEL)
• Gourlet-Fleury Sylvie, CIRAD-ES-UPR Forêts et sociétés (FRA) ORCID: 0000-0002-1136-4307

Source : Cirad-Agritrop (https://agritrop.cirad.fr/599691/)

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