Taking advantage of natural regeneration potential in secondary forests to recover commercial tree resources in Côte d’Ivoire

Abstract

In Côte d’Ivoire, more than 80% of the original forest cover has disappeared due to slash-and-burn shifting agricultural practices, uncontrolled logging, and large-scale land conversion for cash crop cultivation. Yet the demand for timber continues to grow and cannot be met by the scarcity of tree plantations. Despite the widespread presence of secondary forests of various ages in Ivorian landscapes, little is known about recovery trajectories of timber resources and the environmental factors that influence recovery rates. We set up 96 0.2 ha forest plots, along a chronosequence of 1 to 40 years and including 7 controls, on which all commercial trees larger than 2.5 cm in diameter at breast height were inventoried. We modelled the recovery trajectories of four complementary indicators of timber resources (basal area, tree density, size of big trees, bole volume) in a Bayesian framework. Our results show that the four indicators recover at different rates, with tree density recovering in less than 15 years while bole volumes need more than a hundred years to recover. Among the local, landscape, and historical factors studied, the number of remnants and proximity to old-growth forests have a positive impact on recovery rates, with, under good environmental conditions, the density, basal area and size of big trees being almost completely recovered in less than 25 years. Our results demonstrate the very high resilience of the timber resource, but also suggest that the landscape management of these post-forest areas must be differentiated according to the landscape context and the presence of isolated trees, which are the last vestiges of the former forest.