Variation on growth unit morphology in Khaya senegalensis (Desr.) A. Juss., 1830 (Meliaceae) and Pterocarpus erinaceus Poir., 1804 (Fabaceae) according to habitat and climate

Retrospective analysis provides access to long-term growth series to understand and interpret the structural functioning of tree crowns required for their sustainable management. The aim of this study was to assess the development and adaptation of crown shoots in Khaya senegalensis and Pterocarpus erinaceus to a changing environment in preparation for establishing permanent plots. The growth units (GUs) morphology of the axes of 420 young, adult, and old individuals was analyzed in full sunlight or shade during the rainy and dry season in seven locations in Côte d'Ivoire. The results showed that growth unit morphology is an indicator of the choice of growth conditions. Heterogeneous habitat had no significant effect on growth unit morphology (P > 0.05) in either species. The morphology of the growth units varied from one location (climate) to another due to distinct environmental characteristics (P < 0.05). The southern part of the gradient (Toumodi and Bouaké in the central region of the country) offers favourable and hence priority areas for reforestation programmes based on the two species. The age of the individuals influenced the number of phytomers per growth unit (P < 0.05). Young individuals (cuttings) are good ideotypes for the selection of suitable resistant genotypes. Whatever the species, the rainy season increased the success rate of plot establishment. The growth units of the two species are practically the same size (P > 0.05). Our results could be a decision guide for the selection of suitable environments for the implementation of reforestation or agroforestry programs based on Khaya senegalensis and Pterocarpus erinaceus, in order to conserve and sustainably manage these species in the current climate change context. Keywords: Khaya senegalensis, Pterocarpus erinaceus, Environment, Morphology, Growth Units (GUs)