Abstract
Palaeoenvironmental changes, inferred from a 492 cm long lake sediment core from Laguna Rabadilla de Vaca (3312 m) in Podocarpus National Park, southeastern Ecuadorian Andes, were investigated using multiple proxies. Pollen, spore and charcoal analyses, as well as x-ray fluorescence and magnetic susceptibility scanning reflect the last c. 11 700 cal. yr BP of climate and vegetation history. Pollen data indicate that the herb-paramo was the main vegetation type at Laguna Rabadilla de Vaca during the early-Holocene period, before c. 8990 cal. yr BP. The herb-paramo was rich in Poaceae, Cyperaceae, Valeriana and Huperzia, reflecting cold and relatively wet climatic conditions. During the middle Holocene from c. 8990 to 3680 cal. yr BP Weinmannia increases markedly, indicating warmer climatic conditions than present-day, probably related to the Holocene thermal optimum, because of a spread of shrub-paramo vegetation and/or a shift of mountain rainforest and sub-paramo vegetation zones to higher elevations. XRF data indicate a drier period from c. 8990 to 6380 cal. yr BP and a wetter period from c. 6380 to 3680 cal. yr BP. A Poaceae-dominated herb-paramo occurred from c. 3680 cal. yr BP until modern times, reflecting cooler climatic conditions relative to the middle Holocene. XRF and charcoal data indicate a decrease in precipitation during this period.
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