Life after fire - Long-term responses of 20 timber species in semi-deciduous forests of West Africa

Abstract

Understanding the response of commercial timber species to fire is fundamental to designing sustainable forest management strategies in West Africa. In this area of high deforestation for agriculture, semi-deciduous tropical forests have been reduced to a trickle in 50 years and are now subject not only to logging but also to increasingly frequent fires. This paper aims to study the long-term (37 years) demographic and growth responses of 20 timber species after a spatially heterogeneous fire in a West African semi-deciduous forest. We (i) inventoried, in 2020, 100 hectares of plots already established before the 1983 fire, (ii) built demographic and growth models, in a Bayesian framework, to estimate the vulnerability to fire of each species and (iii) linked this vulnerability to functional traits: wood density (WD) and bark thickness (BT). Our results show that most species have lower current abundances but higher growths in burnt areas than in fire-preserved areas. We identified three categories of vulnerability to fire: 1 non-vulnerable species, 16 species with vulnerable demography, and 3 highly vulnerable species. Species with high wood density or thin bark show higher demographic vulnerability to fire. Our results show that fire management is a top priority in West African semi-deciduous forests to maintain long-term populations of timber species and ultimately the forest industry. The differences in vulnerability observed, and the strong predictive power of the functional traits studied, should make it possible to (i) better define harvesting rates and adapt them to fire risk and (ii) better select commercial species to be promoted for reforestation or natural (assisted) regeneration.