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Abstract Detail

Developmental and Structural Section

LEHNEBACH, Romain [1], NICOLINI, Eric [1], BEAUCHENE, Jacques [2], AMUSANT, Nadine [2].

Architecture and wood allocation: relevance in predicting radial growth rates and sapwood area in a tropical forest tree of French Guiana (Dicorynia guianensis Amsh., Fabaceae).

Dicorynia guianensis, an emergent tree in French Guianan forests, is the most locally used timber tree and consequently of great commercial interest. However, it exhibits great variability of sapwood-heartwood proportion within tree diameter classes, and as such often generates excess material unused by sawyers. In general, current methods to estimate heartwood-sapwood quantity lack precision, require pre-existing inventory data and fastidious field work. Thus, refining estimation methods of sapwood area (SWA) could in turn improve sustainable forest management practices. 30 years of monitoring in the experimental plots at Paracou research station have shown a great variability in radial growth rate at breast height (RGR) for this species, and preliminary observations have revealed that SWA is linearly correlated with RGR. Since RGR cannot be accurately predicted by parameters such as DBH, height or crown size, and its measurement is time-consuming, there is currently no effective indicator of SWA or RGR. Our main objective thus is to investigate tree structure in order to find structural variables that can efficiently estimate both RGR and SWA. Inspired by studies on tree architecture, pipe model theory and tree growth rings vertical profile, we present a novel way to consider tree structure and functioning in predicting these two variables. Assisted by climbers, we described and measured the whole architecture of 52 living trees at Paracou at a fine scale, focusing on crown topology, living branch number, branch mortality events and the volume proportions of their different parts (i.e. trunk and crown). Using this data, we then compared different extracted architectural parameters with RGR and SWA calculated from sapwood thickness measurements at breast height. Our analysis, confirm that branch mortality proportion has a negative effect on both RGR and SWA. We also found that trunk height is negatively correlated with these two variables. Trunk height corresponds to the height above the ground where reiteration process occurs. To face competition for light in natural forest, tree will have to invest more biomass in crown if trunk height is low than if trunk height is high. Thus, trunk height has a strong effect on wood allocation between trunk and crown, and consequently on RGR and SWA. This study highlights new elements of tree biomass allocation during ontogeny by revealing new aspects of tree ageing, and shows that RGR is still a complex process which is difficult to predict and remains important in the context of natural forests and their understanding.

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1 - CIRAD, UMR AMAP - botAnique et bio-inforMatique de l'Architecture des Plantes, Bp 701, Kourou, French Guiana, 97310, France
2 - CIRAD, UMR EcoFoG -Ecologie des Forets de Guyane, Bp 701, Kourou, French Guiana, 97310, France

Tree architecture
Sapwood area
Radial Growth rate
Wood allocation
tropical tree species
Natural forest.

Presentation Type: Oral Paper:Papers for Sections
Session: 26
Location: Pines North/Boise Centre
Date: Tuesday, July 29th, 2014
Time: 2:00 PM
Number: 26003
Abstract ID:419
Candidate for Awards:Katherine Esau Award

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