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Cordia alliodora (Boraginaceae) as a candidate for tree plantations in French Guiana: characteristics and development of natural populations in Saül vicinity

Bossu J., Heuret P., Morel H., Nicolini E.A.. 2016. In : Plinio Sist (ed.), Stéphanie Carrière (ed.), Pia Parolin (ed.), Pierre-Michel Forget (ed.). Tropical ecology and society reconciliating conservation and sustainable use of biodiversity. Program and abstracts. Storrs : ATBC, p. 117. Annual Meeting of the Association for Tropical Biology and Conservation (ATBC 2016), 2016-06-19/2016-06-23, Montpellier (France).

In French Guiana, forest accounts for almost 96% of the territory, with the habitat maintaining a good state of conservation. Nonetheless, forest management in this region faces new challenging issues given the emerging and increasing demands for wood products. The present-day challenge is to develop sustainable and efficient wood production solutions, whilst preventing deforestation and reducing the current dependence on importation. Plantations of native fast-growing species here represent a real potential. Cordia alliodora is a long-lived pioneer species known only in French Guiana in the vicinity of the town of Saül. This species appears to match the requirements for plantation growth, in relation to its very high growth rate and good wood properties. Nevertheless, to our knowledge, no growth monitoring has been conducted in French Guiana, with little information on the performance of local populations under natural conditions. Here, we present a retrospective analysis of C. alliodora development (primary and secondary growth) based on anatomical and morphological markers. To achieve this work, we also describe the past development of adjacent trees belonging to the pioneer species C. obtusa. This last species was considered here as "standard" to (i) estimate the age of secondary forest within which both species belong, (ii) demonstrate the annual nature of growth rings in C. alliodora and (iii) compare the growth trajectories of the two species. We sampled 13 and 15 individuals of C. alliodora and C. obtusa trees respectively in three contrasted sites in the region of Saül. Above 10 meters in height, which is the flowering stage of C. obtusa, our results show that C. obtusa and C. alliodora have a competitive growth in height despite two contrasted growth strategies (continuous growth vs. polycyclic rhythmic growth). Beyond this point, C. alliodora becomes dominant in the stand. Strong differences were observed in C. alliodora growth trajectory depending on the studied site, demonstrating a high phenotypic plasticity (lato sensu). We also estimate that under good growth conditions, this species is able to reach a productivity of 11 m3/ha/years and enable rotations in less than 30 years. From these promising results we can consider that C. alliodora is a good contender as an alternative timber productive system in French Guiana, provided it is accompanied by other species, such as C. obtusa, to encourage straight and rapid growth without bole defects. (Texte intégral)

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