Eastern Andean Patagonia (40º-51ºS) vegetation and climate variability during the Holocene related to southern westerlies fluctuations and recent human interactions. Impacts on Patagonian forests and steppe plants communities

SOTTILE,G.D; MARCOS, M.A, BAMONTE, F.P; ECHEVERRÍA, M.E., DE PORRAS, ME., TONELLO, M.S, MANCINI, M.V, BIANCHI, M.M.

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Congreso; 4th PAGES Open Science Meeting (OSM).; 2013

Vegetation patterns in Patagonia are driven by a strong west-east annual precipitation (Pann) gradient related to Southern Westerly Winds (SWW) and the Andes cordillera rainshadow. Stronger (weaker) SWW seem to steeper (weaken) the Pann gradient on the lee side of the Andes, drying (humidifying) the extra-andean steppes. While weaker SWW, allow Pacific humid air masses to reach western grass steppes and Atlantic air masses to reach eastern grass and shrub steppes, stronger SWW force Pacific humid air masses to discharge most of the precipitation in the Andes, considerably reducing the humidity of the air masses that reach eastern Patagonia (Garreaud et al. in 2013) . The integration of peat bog and lake records from the eastern side of Patagonian Andes offer the opportunity to gain a better understanding and propose a preliminary regional palaeoenvironmental synthesis. Today, a lot of controversy and debate about SWW strength and displacement during the Holocene exists (Fletcher & Moreno, 2012; Killian & Lamy, 2012). Other natural and anthropic forces have also modified patagonic vegetation specially during the late Holocene. The objectives of this study are: Describe and compare pollen anomaly indexes and fire regime changes as signal of water balance changes in northern vs. southern, and western vs. eastern regions of Patagonia during the Holocene in order to propose a model of SWW Holocene variability and discuss it with climate models available for Patagonia. Analyze the effect of other natural or human drivers of vegetation changes on Patagonian plant communities during the late Holocene.