Deglacial and postglacial history of temperate rainforest in Isla Grande de Chiloé, Chile
by
Ana M. Abarzúa Vasquez
Instituto de Geociencias, Universidad Austral de Chile, Valdivia, Chile

At present human and natural disturbances are the most common responsible in the temperate rainforests dynamics. Few paleoclimate records from terrestrial environments in Southern Hemisphere have temporal continuity, high time resolution, and adequate chronologic control to allow for a detailed examination of the timing, direction, and rates of vegetation and climate change at millennial, and multimillenial timescales.

Stratigraphic, palynologic, and macro-charcoal records from small, high-sediment accumulating lakes in southern portion Isla Grande de Chiloé show catastrophic changes in the last glacial-interglacial cycle. Indeed, Laguna Melli and Laguna Tahui records (~42°46´ S; 73º33´ W; ~70 m) evidence the vegetation changes are trigged by source of an interaction between human, fire and climate during the last 14,700 years 14C BP. The most abrupt changes in the landscape occur at 13,200 years 14C BP with closed canopy forests until modern days, associated to high rates of vegetation changes and warm pulse in the region. These cold and humid conditions, prevailing during the Late-glacial period, contrast with the warm and dry condition prevailing in the mid-early Holocene, between 10,000-6,000 years 14C BP, dominated by Valdivian forest ensemble. This period is characterized by an important increase in macro-charcoal particles, probably due to human and volcanism activity, triggering vegetation change in the Lake Region lowlands, associated changes in the position/strength of the westerly belt accompanied by a decrease in the annual precipitation, and high temperatures.

At ~6,000 years 14C BP start a vegetation mosaic of Nordpatagonian/Valdivian communities, associated a more variable climatic conditions, intensifying in the last ~3,000 years 14C BP when restart fire activity and high rates of vegetation changes in the Lake Region lowlands. These results suggest an increase in climate variability associated to high variability, and frequency climate, possible the start an ENSO-like signal in South America.

Acknowledgements: Fondecyt 1000905-1030766, ICM P02-051-F

Date received: November 18, 2004

Copyright © 2004 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # caod-29.