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Vegetation changes during the past 1300 years in western equatorial Afnrca: a highresolution pollen record from Lake Kamalee, Lope Reserve, Central Gabon

Institut des Sciences de l'Evolution de Montpellier, Equipe Pakloenvironnements, CC 61 Place Eugene Bataillon, CC 61, 34095 Montpellier Cedex 5, France; alfred{at}isem.univ-montp2.fr

Alex Chepstow-Lusty

Institut des Sciences de l'Evolution de Montpellier, Equipe Pakloenvironnements, CC 61 Place Eugene Bataillon, CC 61, 34095 Montpellier Cedex 5, France

Mvoubou Makaya

Laboratoire d'Etude de Geo-Environnements Marins, Universite de Perpignan 52, Avenue Paul Alduy, 66000 Perpignan, France

Patrick Schevin

Jean Maley

Institut des Sciences de l'Evolution de Montpellier, Equipe Pakloenvironnements, CC 61 Place Eugene Bataillon, CC 61, 34095 Montpellier Cedex 5, France

Michel Fontugne

Laboratoire des Sciences du Climat et de l'Environnement, UMR CEAICNRS 1572, Domaine du CNRS, 91198 Gif sur Yvette cedex, France

Richard Oslisly

Wildlife Conservation Society, BP 7847 Libreville, Gabon

Nicaise Rabenkogo

IRSH/GREH, Centre National de Recherche Scientifique et Technique (CENAREST), BP 846 Libreville, Gabon

Dominique Jolly

Institut des Sciences de l'Evolution de Montpellier, Equipe Pakloenvironnements, CC 61 Place Eugene Bataillon, CC 61, 34095 Montpellier Cedex 5, France

Vegetation changes during the past 1300 years are reconstructed in western equatorial Africa using a high-resolution pollen record from Lake Kamalete This small marshy basin (c. 5-7 ha) is located in forest-savanna mosaic in Lope Reserve (043'S, 116'E), central Gabon. The Kamalete pollen data show the persistence over the past 1300 years of a relatively stable forest-savanna mosaic, associated with significant changes of the forest component. Three successive stages of forest dynamics occurred. First, at 1325 cal. BP, moist semi-evergreen rainforest existed around the catchment of Lake Kamalete. However, it appears from the consistent presence of > 70% Gramineae pollen that the site was always primarily in savanna. Secondly, from c. 1240 to 550 cal BP, a noticeable increase in shade-intolerant plant species indicate openings in the rainforest canopy. The persistence of gap-colonizer species, such as Macaranga, Tetrorchidium and Musanga for several centuries in the rainforest, is explained by recurring canopy disturbance associated with shifts in available moisture. These hydrological changes may be related to a succession of longer and more severe dry seasons than observed today. Thirdly, at 550 cal BP, mature forest was re-established, corresponding to progressive savanna colonization by forest pioneer species such as Aucoumea klaineana, Lophira alata and Fagara macrophylla. This new phase of forest expansion coincided with a marked lithological change, indicating an increase in lake-level. It is concluded that the major vegetation changes observed are due to climatic variability, and anthropogenic action had limited influence.

Key Words: Pollen • vegetation change • climatic change • forest-savanna mosaic • canopy disturbance • Gabon • equatorial Africa • late Holocene

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