Vegetation changes during the past 1300 years in western equatorial Africa: a high-resolution pollen record from Lake Kamalete, Lope Reserve, Central Gabon

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 (0 degrees 43'S, 11 degrees 46'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.