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Olivier, Martin-Ducup Convergence of tree architecture with increasing canopy position. An approach from terrestrial laser scanning in central Africa Poster
Martin-Ducup Olivier1, Ploton Pierre1, Barbier Nicolas1, Momo Takoudjou Stéphane2, II Mofack Gislain2, Guy Kamdem Narcisse2, Fourcaud Thierry1, Sonké Bonaventure2, Couteron Pierre1 and Pélissier Raphaël1
(1) AMAP, IRD, CNRS, CIRAD, INRA, Univ Montpellier. Montpellier, France(2) Plant Systematic and Ecology Laboratory, Higher Teacher’s Training College, University of Yaoundé I, Yaoundé, Cameroon

Tree architecture characterizes how they deal with internal and external constraints to build their tridimensional structure to fulfill growth and reproduction functions. Approaching crown shape and tree topological structure of large tropical trees is challenging considering their complexity, size and longevity. Terrestrial laser scanning (TLS) technology offers a new opportunity for the massive collection of such data which can be systematically compared across a large number of species. In the present study we specifically developed topology metrics of within-crown architecture from TLS data, and investigated how they correlated with canopy position, shade tolerance and mechanical constraints.

Fifty-nine trees belonging to 14 co-existing canopy species of Cameroon were reconstructed from TLS data using quantitative structural models (QSM). The species belonged to contrasted shade tolerance groups and were sampled in different canopy positions. Classical global crown shape metrics, original topology metrics and allometric scaling parameters derived from West Brown and Enquist (WBE) metabolic theory were quantified from the QSMs. Correlations between all the descriptors were analyzed through PCA.

Results revealed that topology and crown shape metrics were not correlated, since similar topologies led to contrasted crown shapes. Crown shape, but not topology, changed with tree shade tolerance, while convergence in tree topology and towards expected WBE parameters was observed for all trees reaching dominant canopy positions, independent of species shade tolerance. This convergence is a consequence of sequential development processes (reiterations) occurring when trees attain the canopy. QSM data analysis along ontogeny open many perspectives to model architectural development of trees.