Late-Quaternary savanna history of the Colombian Llanos Orientales from Lagunas Chenevo and Mozambique: a transect synthesis

A 7000-year pollen record of a 90 cm core from Chenevo (4 degrees 05'N, 70 degrees 21'W, 150 m altitude) and a 3500-year pollen record of a 285 cm core from Mozambique (3 degrees 58'N, 73 degrees 03'W, 175 m altitude) both from the savannas of the Llanos Orientales, Colombia, are presented. The records show dynamics between open savanna (Poaccae, Cyperaceac), woody savanna (Byrsonima, Curatella, Didymopanax), palm swamp (Mauritia, Mauritiella), forest and gallery forest taxa. These reflect plant available moisture. and more latterly human impact. The record from Chenevo shows: from 7260 to 6930 C-14 yr BP, open savanna vegetation and gallery forest along the drainage system; from 6930 to 4000 C-14 yr BP, forest and gallery forest expanded from 5500 C-14 yr BP, Mauritia palm forest increased and particularly so from 4000 to 2380 C-14 yr BP also in combination with gallery forest expansion; from 2380 C-14 yr BP to present-day gallery forest, Mauritia and Mauritiella palm forest is most abundant. The from Mozambique is hampered by C-14 reversals, but appears to show the following development: from 3440 to 610 C-14 yr BP abundant Mauritia swamp forests from 600 C-14 yr BP Mauritia swamp forest was replaced by gallery forest in which Byttneria, Mimosa and Sapindaceae are presents from 600 to 350 C-14 yr BP, gallery forest replaced woody grass savanna; during the last 350 C-14 yr BP, savanna increased and gallery forest decreased, as Cecropia, Mauritia and Zea mays point to human impact. Comparison of pollen records from six savanna lakes located along 400 km east-west transect (Sardinas, Angel, El Pinal, Carimagua, Chenevo and Mozambique) shows the following regional vegetation and climate development. From 18000 to 10700 C-14 yr BP, patchy gallery forest, non-permanent lake conditions and maximum abundance of grasses reflect low precipitation and long dry seasons. From 10700 to 9700 C-14 yr BP, gallery forest expansion reflects a more humid climate. From 9700 to 5800 14C yr BP, grasslands were at a maximum, reflecting dry climatic conditions. From 5800 to 3800 C-14 yr BP, gallery forest increased. Around 4000 C-14 yr BP, the savanna ecosystem changed in all records presented: particularly the palms Euterpe/Geonoma Mauritia and Mauritiella became abundant in the savanna ecosystem, this may be indicative of human impact on the savanna ecosystem.