People and forests: Evaluating the impact of historical human activity on the present-day floristic composition of tropical rainforest ecosystems in western Central Africa

UNIL principal investigator

Prof. Gretchen Walters, Faculty of Geosciences and Environment

ULB principal investigator

Prof. Thomas Drouet, Faculty of Science


In Gabon, where environmental variables alone hardly explain the floristic variability, observations from 15 years of field experience indicate that past land-use (PLU) is an auspicious factor to explain community assembly. The study of forest succession can thus provide insights into the process of community assembly through time, and therefore provides an optimal setting to infer the drivers and mechanisms that underlie the structuring of biodiversity.

The main objective of this collaboration will be to mutually support joint projects aiming to investigate the interaction between historical human activity and the present-day floristic composition of tropical rainforests in Gabon.


The project will focus on Gabon where we aim to study forest communities in space-for-time chronosequences of secondary succession at the local scale (< 1 ha) by choosing sampling sites for which information about the site history (i.e., type of disturbance and age of the regrowth) can be obtained either a priori or posteriori. We will track three distinct SSPs, comprising the most dominant land-use types, i.e., selective logging and post-cultural regrowth as well as tree-fall gaps as a natural reference. The following hypothesis is to be tested: PLU causes alternative pathways of secondary succession that differ from natural succession in their (a) taxonomic, (b) functional and (c) life-history strategy composition.

Floristic data will be sampled in the field using standardized MBG vegetation transects. On a surface of 5 x 200 m (0.1 ha), all (± 100) trees with a diameter at breast height (DBH) ≥ 5 cm are identified at the species level, if possible, and measured in DBH. Additionally, 100 dominant trees will be sampled to balance the record between the forest strata.

We will assign each sampling unit to a secondary successional pathway (SSP) based on descriptors of human activity related attributes. Therefore, we will compile a prioriori and/or posteriori information on past land-use type, intensity, frequency, duration and spatial extent for each transect.


  • Preparation reunion: 16-18 March 2022
  • Archive works: 10-13 May 2022
  • Field mission: 20 November - 12 December 2022
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