Vegetation, climate and fire in the eastern Andes (Bolivia) during the last 18,000 years

Abstract

A c. 18kacal BP long sediment record from Laguna Khomer Kocha Upper (4153m asl), Bolivia, shows that fire regime, governed by climatic variation, has long been a transformative agent in the eastern Andes. Before c. 14.5kacal BP, warming and relatively moist conditions free from fire, facilitated the expansion of high Andean Polylepis woodland. Fire onset at c. 14.5.kacal BP, quickly transformed the local vegetation and the woodlands became restricted to areas protected from fire. A major increase in burning, c. 10.1–6.4kacal BP removed Polylepis woodland locally and this coincided with a region-wide Holocene dry event (HDE) which caused falling lake levels and allowed fire intensification. A decline in burning at c. 6.4kacal BP and an increase in marsh–woodland (Alnus) marked the termination of the HDE and a return to wetter conditions. As well as recording the environmental history of local vegetation dynamics, long-distance pollen transport provides evidence of changes in the Yungas montane forests, highlighting their sensitivity to climate and burning regimes. Simultaneous adjustments in both Andean and Yungas montane taxa suggest that vegetation dynamics in the two environments are linked to a common climatic driver. There is no evidence to indicate that human activity had any impact on the local landscape.