Structural and floristic typology of the forests in the forest-savanna mosaic of the Lopé National Park, Gabon

Florence Palla,Kate A Abernethy,Bernard Riéra,Elizabeth C White,Tharcisse Ukizintambara,Lee White,Nicolas Picard,Jean-Paul Rudant

doi:10.5091/plecevo.2011.478

Abstract

Background and aims - The Lope National Park in Gabon, recently added to the UNESCO world heritage list, presents a mosaic of forest and savanna that dynamically changes. Conserving this landscape requires an understanding of the forest dynamics. This study aims at defining a forest typology at Lope in relation with its dynamics. Methods - Floristic and structural characteristics for 265 tree species belonging to 55 families were measured in 258 sampling plots in the Lope National Park. Multivariate analysis of these data was used to partition the sampling plots into groups on the basis of their floristic or structural characteristics. Key results - Five structural forest types and six floristic forest types were identified. This typology showed that the forests in the forest-savanna mosaic of Lope organize themselves along a gradient of forest recovery, from young forests to mature forests. Typical pioneer species are associated with the youngest forest stages. The gradient on the species also corresponds to a geographical gradient on the sampling plots, associated with features like altitude, rocks, or hydrography. Conclusions - Five forest types were defined on the basis of species abundances. The snapshot of forest types characterizes a dynamic process of forest regeneration (Resume d'auteur)

Highlights

Many tropical forests have once been disturbed by human activities, but after a long time following this disturbance, only a detailed examination of the structure and floristic composition of the vegetation can reveal a difference with pristine forests
When using a classification method based on floristic data with a weight for each species proportional to its abundance, this gradient vanishes and floristic groups become more similar to structural groups
The significant relationship between the number of trees in diameter class N6 and basal area suggests that the corresponding species are commercial species that were not removed following selective logging

Summary

Introduction

Many tropical forests have once been disturbed by human activities, but after a long time following this disturbance, only a detailed examination of the structure and floristic composition of the vegetation can reveal a difference with pristine forests. The effect of selective logging on native tree diversity in tropical forests is a subject of speculation and of great current concern, but very limited data are available to assess its impact (Brown & Gurevitch 2004). Rain forest is a complex community whose framework is provided by trees of many sizes. The consideration of the autoecology of individual tree species necessitates a reinterpretation of the much-discussed concept of stratification in the canopy (Whitmore 1975). The use of the stratification concept allows one discriminating species at different heights

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Conclusion