Growth determinants of timber species Triplochiton scleroxylon and implications for forest management in central Africa

Ligot Gauthier, Fayolle Adeline, Gourlet-Fleury Sylvie, Daïnou Kasso, Gillet Jean-François, De Ridder Maaike, Drouet Thomas, Groenendijk Peter, Doucet Jean-Louis. 2019. Growth determinants of timber species Triplochiton scleroxylon and implications for forest management in central Africa. Forest Ecology and Management, 437 : 211-221.

Url - jeu de données - Dataverse Cirad : https://doi.org/10.18167/DVN1/1TUOBI

Quartile : Q1, Sujet : FORESTRY

Résumé : The sustainability of the polycyclic logging system in tropical forests has been increasingly questioned for a variety of reasons, and particularly in central Africa as commercial species, mostly light-demanding long-lived pioneer species, usually fail to recover a stable number of large trees after exploitation. Several factors are known to affect tropical tree demographic processes, like tree growth, survival and recruitment. Tree growth has particularly been showed to depend on ecological conditions, tree genetics, and competition with surrounding vegetation, as well as tree size or ontogeny. Yet, due to the paucity of available data, the importance of such factors is unclear and usually ignored when estimating future timber yields. To fill this gap, we chose to evaluate the variability in growth of one African long-lived pioneer and commercially very important species: Triplochiton scleroxylon K. Schum, gathering a broad dataset composed of tree ring data recorded in one site in Cameroon and periodic field inventory data recorded in seven sites across central Africa. In total, we analyzed 13,225 records of annual tree diameter increments recorded over 920 trees from seven sites in Cameroon, Republic of the Congo and Central African Republic. We evaluated (i) to what extent the average growth of trees that reach harvestable dimensions differs from population average and (ii) to what extent past perturbations influence the growth of remaining trees. We found the diameter growth of T. scleroxylon to be remarkably variable and this study provided an unprecedented quantification of the magnitude of some key growth determinants. In unlogged forests, the diameter increment of T. scleroxylon ranged between 0.40 cm year−1 in Southern Cameroon and 0.83 cm year−1 in South-Eastern Cameroon. The diameter increment was weakly related to tree size but increased twofold from unlogged to logged forests. Perturbation caused by logging stimulates growth of T. scleroxylon for at least 10–15 years. Finally, harvestable timber stock of large-sized T. scleroxylon was found to be constituted by trees that grew in average twice faster than trees of the entire extant population. As more and more inventory data become available, quantifying these effects could be replicated for other timber species and in other sites, to improve the accuracy of future timber resource estimates and improve forest management guidelines.

Mots-clés Agrovoc : forêt tropicale, exploitation forestière, Triplochiton scleroxylon, accroissement du diamètre, accroissement forestier, besoin en lumière, aménagement forestier, durabilité

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

Mots-clés libres : Tree ring analysis, Light demanding species, Logging, Persistent fast growth, Stock recovery rate

Classification Agris : K01 - Foresterie - Considérations générales

Champ stratégique Cirad : CTS 2 (2019-) - Transitions agroécologiques

Auteurs et affiliations

• Ligot Gauthier, Université de Liège (BEL) - auteur correspondant
• Fayolle Adeline, Université de Liège (BEL)
• Gourlet-Fleury Sylvie, CIRAD-ES-UPR Forêts et sociétés (FRA) ORCID: 0000-0002-1136-4307
• Daïnou Kasso, Université de Liège (BEL)
• Gillet Jean-François, Université de Liège (BEL)
• De Ridder Maaike, Musée royal de l'Afrique centrale (BEL)
• Drouet Thomas, ULB (BEL)
• Groenendijk Peter, UNICAMP (BRA)
• Doucet Jean-Louis, Université de Liège (BEL)

Source : Cirad-Agritrop (https://agritrop.cirad.fr/591013/)

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