Late Pleistocene and Holocene environmental change inferred from the Cocha Caranga sediment and soil records in the southeastern Ecuadorian Andes

Abstract

Late Pleistocene and Holocene vegetation, climate and fire dynamics of mountain forest and paramo ecosystems, as well as human impact, are presented from the Cocha Caranga area, at 2710 m elevation in the Podocarpus National Park, southeastern Ecuadorian Andes. Palaeoenvironmental changes, inferred from two sediment cores and a soil core were investigated by pollen, spore, algae and charcoal analyses. During the transition from late Pleistocene to early Holocene between ca. 14,500 to 9700 cal yr BP upper mountain forest vegetation expanded, suggesting increasing temperature and moisture. This expansion abruptly stopped with increasing fires at ca. 9700 cal yr BP and open grassy vegetation became established. The period from ca. 9700 to 1300 cal yr BP of strong fire intensity indicate that vegetation components, mainly Weinmannia and Myrica, react sensitively to past, probably human caused fires. During the last few centuries modern vegetation established, characterised by open grassy areas with forest patches and small mires. The green algae Botryococcus braunii, Isoetes and Cyperaceae were used to identify lake level fluctuation to reconstruct Holocene wet/dry phases. Drier climatic conditions occurred from ca. 9700 to 6900 cal yr BP and from ca. 4200 to 1300 cal yr BP. From ca. 6900 to 4200 cal yr BP and from ca. 1300 cal yr BP to modern times, wetter climatic conditions occurred.