Three decades of monitoring 22 native tree species planted in an arboretum in Korhogo in northern Côte d'Ivoire.
In forest plantations in tropical Africa, most native species have been left aside in favour of exotic species with initially rapid growth rates. This tendency is even more marked in the Sudanian and Sahelian zones with a long dry season, and explains the lack of knowledge on the potential of native or "local" tree species and suitable sylvicultural methods. To contribute to the acquisition of this essential knowledge, a 2.56 ha arboretum was established in 1990 in the Korhogo area in northern Côte d'Ivoire. A particular feature lies in the establishment of large parcels (1,596 m2) with 224 saplings of each species. The aim was to allow sylvicultural treatment that would conserve 10 to 16 adult trees of each species, in particular for their timber, by the end of each rotation. Because nursery techniques for some of the species were insufficiently mastered, the 244 saplings per species initially planned were only planted for 12 of the 22 species. The results are shown for all of the species tested, both in the nursery and once planted out. This arboretum was regularly monitored until 1999, when proper management was disrupted by political upheaval in the country. A measurement campaign was set in motion in November 2019, which brought interesting conclusions as to the aptitude for growth of 15 species in even-aged single-species stands, two of which (Pterocarpus erinaceus Poir. and Anogeissus leiocarpa (DC.) Guill. & Perr.) show outstanding productivity. All of the data collected as from seed harvesting and throughout the life of the arboretum are presented and discussed here, in the hope that this will be of benefit to foresters in this phytogeographical area. The lessons learned should be applied to forest and landscape restoration through the reforestation commitments made by countries to tackle climate change, biodiversity loss and the degradation of ecosystem services to populations.