Vegetación History and climatic variability during the Late Holocene at Pampa grasslands: the sate of art

PRIETO, A.R., STUTZ, S., VILANOVA I., TONELLO, M.

Malargüe, Mendoza

Simposio; Reconstructing Past Regional Climate Variations in South America over the late Holocene: a new PAGES Initiative; 2006

In the Pampa grasslands (34º-39ºS; 56º-63ºW) the vegetational history based on pollen analysis has been mainly conducted at alluvial sites since pollen records from shallow lakes are temporally and spatially limited. Even though pollen assemblages in alluvial sequences may be biased as a result of episodic and irregular accumulation of sediments, these sequences are amazingly constant over large distances and contain very well preserved pollen grains in large quantities giving us the possibility to obtain important paleoenvironmental information. In this overview, we selected key proxy palynological records with different temporal and spatial resolution in order to evaluate the response of the vegetation to different forcings during late Holocene and to show the advancements achieved over the last years. The vegetation changes are discussed at individual sites by comparing them with other paleoenvironmental proxy and historical data. A quantitative climatic reconstruction applying a pollen-climate calibration model is presented and discussed as an example of quantification of paleoclimatic variables. Pollen records allowed us to infer (1) a pattern of environmental variability to large-scale, mainly in precipitation and humid index during late Holocene, (2) sea level variations as the main forcing affecting the vegetation of the southeastern coast between 6500 and 4000 yr BP and, (3) anthropogenic impact on vegetation over last ca. 300 years, which correlate accurately with evidence concerning the documentary information. In addition, pollen and no-pollen palynomorphs records have recently allowed to propose an alternative explanation for the vegetational change from shallow lakes.