Publication: forest-savanna bistability in tropical Africa

Recently, Adeline Fayolle, a researcher at Gembloux Agro-Bio tech co-authored an article published in the prestigious journal PNAS*: he was interested in the floristic evidence of alternative stable states between the two main biomes in tropical Africa, the forest and the savannah. A new mapping of the biomes was thus proposed as a very valuable tool to guide planting and restoration efforts in this region.

Alternative stable states in tropical biomes

The researchers who participated in this study were able to provide large-scale evidence that there are alternative stable states in the tree species composition of tropical African vegetation. Thus, a new, more accurate map of the distribution of the two main tropical biomes (forest and savannah) could be produced. This takes into account the species composition of trees and a number of environmental determinants including climate, soil and disturbances.
Previous studies on bistability were based on vegetation structure, including the multimodal distribution of structure indicators. The different modes represented a heavily forested state, forest; a moderately forested state, savannah and a non-wooded state, grasslands and steppes. These approaches were criticised because structure alone does not allow one to distinguish the most humid savannas from the driest forests. In the new study, an alternative approach has been developed: it uses lists of tree species collected for a large number of sites and forest and savannah areas available for the African continent, in order to delimit the climatic envelope of forest and savannah in Africa. In addition, it was found that forest and savannah sites have divergent tree species compositions. Thanks to this, it has been possible to quantify the environmental limits of forest and savannah; limits which are mainly determined by climate (rainfall and seasonality) but also by fire.
What is the most important thing about this study? To be able to give precise indications for restoring African ecosystems.

* PNAS: Proceeding of the National Academy of Sciences of the United States of America.

Crédit photo : Jean-Louis DOUCET

En savoir + :  https://www.pnas.org/content/117/45/28183.short?rss=1