Late Holocene history of savanna gallery forest from Carimagua area, Colombia

The pollen record of a 65 cm long core Laguna Carimagua-Bosque (4 degrees 0 4'N, 70 degrees 13'W) shows the late Holocene environmental history from a lake located within the gallery forest of the savannas of the Llanos Orient ales of Colombia. Nine AMS radiocarbon dates of the organic deposits show t hat the core represents the period from ca. 1300 C-14 yr BP to the present. The lake evolved from an active drainage system. During the period from ca. 1300 to 875 C-14 yr BP (zone CMB-Ia), Mauritia-d ominated swamp and gallery forest was present, dominated by Cecropia, and l ater also Acalypha and Alchornea, From 875 to 700 C-14 yr BP (zone CMB-Ib), the lake was completely surrounded by gallery forest. Mauritiella and Cecr opia occurred around the lake. Cecropia pioneer forest reached its greatest abundance and became gradually replaced by a more species-rich gallery for est, including Acalypha, Alchornea, Euterpe/Geonoma, Moraceae/Urticaceae, P iperaceae, and Virola. From 700 to 125 C-14 yr BP (zone CMB-II), Cecropia l ost its dominant role, and Mauritiella palms became more frequent. The main vegetation categories were swamp forest, gallery forest, understory elemen ts, savanna shrubs and trees, and grass savanna. From 125 C-14 yr BP to rec ent (zone CMB-III), the plant diversity in the gallery forest became highes t, Mauritiella became very abundant, and among the savanna elements, woody Didymopanax increased. Comparison of four pollen records from savanna sites shows that pollen of s avanna vegetation is markedly underrepresented in lake sediments when the l ake lies within the gallery forest. As most of the drainage system of a sav anna is hidden by gallery forest, we also expect a significant underreprese ntation of the savanna ecosystem in river-transported pollen assemblages. ( C) 2000 Elsevier Science B.V. All rights reserved.