Modern pollen–vegetation relationships within tropical marshes of Lopé National Park (Central Gabon)

Abstract

In the Congo Basin, paleoenvironmental data are scarce, due to the lack of natural lakes. Using marshes sedimentary deposits as alternative archives requires the calibration of modern pollen assemblages, which are totally absent for these type of deposits. The aim of this study is to understand and qualify how well surface marsh sediment pollen assemblages reflect the contemporary vegetation. We compare pollen assemblages at the surface of 23 sedge marshes disseminated in an enclave of savanna in the Gabonese forest and vegetation surveys along transects from sampling areas. Very high diversity of forest pollen taxa is recorded, with a gradient of diversity from most open environments to those where the forest is closer, however savanna taxa remains low. The surface samples surprisingly reveal general weak percentages of Poaceae pollen grains that never exceed 25%. The low proportion of Poaceae is consistent with the deposition mode of pollen in these specific sites but challenges the common interpretation of a straightforward relationship between this percentage and savanna/forest balance.