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Abrupt vegetation changes during the last glacial to Holocene transition in mid‐latitude South America
Author(s) -
Moreno Patricio I.,
León Ana L.
Publication year - 2003
Publication title -
journal of quaternary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.142
H-Index - 94
eISSN - 1099-1417
pISSN - 0267-8179
DOI - 10.1002/jqs.801
Subject(s) - nothofagus , holocene , glacial period , last glacial maximum , rainforest , physical geography , geology , vegetation (pathology) , evergreen , ecology , geography , oceanography , paleontology , biology , medicine , pathology
A pollen record from the Huelmo site (ca. 41°30′S) shows that vegetation and climate changed at millennial time‐scales during the last glacial to Holocene transition in the mid‐latitude region of western South America. The record shows that a Nothofagus parkland dominated the landscape between 16 400 and 14 600 14 C yr BP, along with Magellanic Moorland and cupressaceous conifers. Evergreen North Patagonian rainforest taxa expanded in pulses at 14 200 and 13 000 14 C yr BP, following a prominent rise in Nothofagus at 14 600 14 C yr BP. Highly diverse, closed canopy rainforests dominated the lowlands between 13 000 and 12 500 14 C yr BP, followed by the expansion of cold‐resistant podocarps and Nothofagus at ca. 12 500 and 11 500 14 C yr BP. Local disturbance by fire favoured the expansion of shade‐intolerant opportunistic taxa between 10 900 and 10 200 14 C yr BP. Subsequent warming pulses at 10 200 and 9100 14 C yr BP led to the expansion of thermophilous, summer‐drought resistant Valdivian rainforest trees until 6900 14 C yr BP. Our results suggest that cold and hyperhumid conditions characterised the final phase of the Last Glacial Maximum (LGM), between 16 400 and 14 600 14 C yr BP. The last ice age Termination commenced with a prominent warming event that led to a rapid expansion of North Patagonian trees and the abrupt withdrawal of Andean ice lobes from their LGM positon at ca. 147 000 14 C yr BP. Hyperhumid conditions prevailed between 16 400 and 13 000 14 C yr BP, what we term the ‘extreme glacial mode’ of westerly activity. This condition was brought about by a northward shift and/or intensification of the southern westerlies. The warmest/driest conditions of the last glacial–interglacial transition occurred between 9100 and 6900 14 C yr BP. During this period, the westerlies shifted to an ‘extreme interglacial mode’ of activity, via a poleward migration of stormtracks. Our results indicate that a highly variable climatic interval lasting 5500 14 C years separate the opposite extremes of vegetation and climate during the last glacial‐interglacial cycle, i.e. the end of the LGM and the onset of the early Holocene warm and dry period. Copyright © 2003 John Wiley & Sons, Ltd.