Holocene Amazon rainforest-savanna dynamics and climatic implications: high-resolution pollen record from Laguna Loma Linda in eastern Colombia

We present a high-resolution pollen record of a 695-cm-long sediment core f rom Laguna Loma Linda, located at an altitude of 310 m in the transitional zone between the savannas of the Llanos Orientales and the Amazonian rainfo rest, about 100 km from the Eastern Cordillera. Based on eight AMS C-14 age s, the record represents the last 8700 C-14 yr BP. During the period from 8 700 to 6000 C-14 yr BP the vegetation was dominated by grass savanna with o nly a few woody taxa, such as Curatella and Byrsonima, present in low abund ance. Gallery forest along the drainage system apparently was poorly develo ped. Compared with today, precipitation must have been significantly lower and seasonality stronger. During the period from 6000 to 3600 C-14 yr BP, r ainforest taxa increased markedly, reflecting an increase in precipitation. Rainforest and gallery forest taxa such as Moraceae/Urticaceae, Melastomat aceae, Alchornea, Cecropia and Acalypha, were abundant, whereas Poaceae wer e reduced in frequency. From 3600 to 2300 C-14 yr BP rainforest taxa contin ued to increase; Moraceae/Urticaceae became very frequent, and Myrtaceae an d Myrsine became common. Savanna vegetation decreased continuously. We infe r that precipitation was still increasing, and that the length of the annua l dry period possibly shortened. From 2300 C-14 yr BP onwards, grass savann a (mainly represented by Poaceae) expanded and Mauritia palms became freque nt. This reflects increased human impact on the vegetation. Copyright (C) 2 000 John Wiley & Sons, Ltd.