Mémoire
| Résumé : | Objectives: In Gabon, where continuous tropical forests cover 88.5% of the surface, the distinct types of forest remain unknown to date. Here, we hypothesize that human activity had a higher relative effect on the canopy than the understory floristic composition. We aimed at (i) identifying the spatial distribution of diversity (ii) investigate drivers of the species turnover and (iii) test for the effect of human activity on the canopy.Location and methods: Analyses were based on standardized floristic inventories conducted by the Missouri Botanical Garden in Gabon, compiling information for 76,499 trees with a diameter at breast height (DBH) ≥ 5 cm and identified at the species or subspecies level from 411 vegetation transects. Cluster analyses were used to produce three new forest typologies based on (i) the understory community, (ii) the upper canopy and (iii) both forest strata. Constrained ordination and variation partitioning analyses were used to quantify the relative effect of environment, past human activity and space on the species turnover.Results: Our study produced the forest typology to include the entire floristic diversity of all forest strata. Over all strata, the spatial effect explained 34.0 % of the floristic variability, environment 3.5 % and human activity 2.7 %. Human activity contributed a higher relative effect to the canopy (2.7 %) than to the understory turnover (2.2 %), confirming our hypothesis.Conclusion: Our study shows that the floristic diversity patterns differ among the forest strata and provides evidence that human activity may be the cause of this dissimilarity. These results can build the basis for future conservation and adapted management strategies. |
