By Christian OBAME -

FR – De la forme à la source : la morphologie du charbon de bois sédimentaire comme indicateur de la composition de la biomasse tropicale brûlée

AN – From Shape to Source: Sedimentary Charcoal Morphology as a Proxy for Tropical Burned Biomass Composition

Résumé / Abstract

FR –Pour étudier les feux du passé, l'examen de la longueur des charbons permet de différencier l'herbe brûlée du bois brûlé. Pourtant, cette étude n'a jamais vraiment été réalisée pour les plantes tropicales, alors que cela permettrait de mieux comprendre l’histoire des incendies, la déforestation et la capacité de la nature à se reconstruire sur le long terme.

D’habitude, une limite fixe de longueur est utilisée pour distinguer les charbons d’herbe de ceux de bois. Cette méthode est toutefois trop rigide et ne tient pas compte de la grande variation des formes de charbons entre échantillons, pouvant fausser l’interprétation des incendies passés.

Pour y remédier, un modèle mathématique a été développé afin de classer les fragments de charbon selon leur morphologie. Ce modèle, testé sur 19 enregistrements de charbons anciens d’Afrique de l’Ouest et centrale couvrant les 30 dernières années, offre une meilleure distinction entre herbe et bois en intégrant la diversité des longueurs observées.

Les résultats, comparés aux images satellites de la forêt actuelle, montrent que plus un site est arboré, plus il contient de charbons de type « bois ». L’application du modèle aux sédiments du lac Sélé (Bénin) a permis de reconstituer l’histoire de la végétation, des résultats cohérents avec les données polliniques anciennes, confirmant l’efficacité de cette méthode.

AN –To study past fires, examining charcoal length helps differentiate burnt grass from burnt wood. However, such analyses have rarely been conducted for tropical plants, despite their importance for understanding fire history, deforestation, and long-term ecosystem recovery.

A fixed length threshold is usually applied to distinguish grass from wood charcoal, but this approach is too rigid and ignores the high variability in charcoal shapes between samples. This can bias interpretations of past fire events.

A mathematical model was therefore developed to classify charcoal fragments based on their morphology. Tested on 19 charcoal records from West and Central Africa covering the last 30 years, the model better separates grass from wood by incorporating the full range of charcoal sizes.

Comparisons with modern satellite imagery show that the more trees present on a site, the more wood-type charcoal appears. Applying the model to sediments from Lake Sélé (Benin) enabled reconstruction of vegetation history, with results consistent with ancient pollen records, confirming the method’s reliability.

AN –Fig. Location of the study sites in West and Central Africa, with regional vegetation based on White (1984). The satellite images and photos of five sites, representing the variety of vegetation types and the degree of agricultural conversion, are framed in different colors to make them easier to find throughout this article.


FR –Fig.Localisation des sites d'étude en Afrique de l'Ouest et centrale, avec la végétation régionale d'après White (1984). Les images satellites et les photos de cinq sites, représentatives de la diversité des types de végétation et du degré de conversion agricole, sont encadrées de différentes couleurs pour faciliter leur repérage dans cet article.

MOTS-CLÉS / KEYWORDS

FR – Modèle bayésien ; rapport d’allongement du charbon de bois ; mosaïque forêt-savane ; paléoécologie ; Afrique de l’Ouest et centrale
AN – Bayesian model; charcoal elongation ratio; forest–savanna mosaic; paleoecology; West and Central Africa

Auteurs / Authors

Fiona Cornet, Vincent Montade, Stéphanie C. Bodin, Justine Descloitre, Maxime Réjou-Méchain, Gaëlle Viennois, Julie C. Aleman, Chimène Assi-Kaudjhis, William F. Kenney, Richard Oslisly, Monique G. Tossou, Laurent Bremond, Charly Favier

À citer / To cite :
Fiona Cornet, Vincent Montade, Stéphanie C. Bodin, Justine Descloitre, Maxime Réjou-Méchain, et al.

DOI :10.1002/jqs.70053

Source :Journal of Quaternary Science / Journal des sciences du Quaternaire, John Wiley & Sons Ltd (2026) 1–17

Date de publication / Publication date

29 janvier 2026 / January 29, 2026

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