Vegetation and environmental changes related to hydroclimate regimes in Western Pampas, Argentina, over the last 1.5 kyr.

ISABEL VILANOVA; ALFONSINA TRIPALDI; EDUARDO L. PIOVANO; STEVE FORMAN; JORGE CHIESA; ESTEBAN JOBBAGY; LEANDRO D. ROJO; GUILLERMO HEIDER; KARSTEN SCHITTEK

Zaragoza

Congreso; 5th Open Science Meeting; 2017

PAGES

The Western Pampas of Argentina is a climate-sensitive region located near the eastern fringe of the Arid Diagonal of South America where spatial and temporal fluctuations of the Southern Hemisphere west-wind drift and the South American tropical circulation can be recorded. Shallow lakes formed in blowout dunes in this semiarid/subhumid region (33-34°S; 65°21?W) are a key source for reconstructing Late Quaternary environmental and paleoclimatic evolution because they provide geomorphologic evidences, sedimentary archives, and proxy-indicators (pollen and other palynomorphs, charcoal, C and N stable isotopes, among others) for deciphering the present landscape dynamics and the environmental changes over time. Basal radiocarbon dates of lake cores from different shallow lakes (e.g. Nassau, Los Pocitos and Primera Laguna) suggest that the commencement of organic sediment deposition occurred at dissimilar times. In addition, palynological analyses of these cores reveal local vegetation changes at multi-centennial and decadal scales for the last ~1.5 kyr, concomitant with variable dry and humid phases and anthropogenic activity. Regarding regional vegetation, pollen records indicate that the main components of the Pampean Grassland, Espinal (savannah-like with grasses), and Monte (shrub steppe with scattered woodlands) vegetation units (e.g. Celtis, Larrea, Prosopis) were present in the region since ~1.5 kyr BP. During the last ~300 cal yr BP some variations in the pollen assemblages, representing psammophytic and halophytic communities, seem to coincide with sand-dunes stabilization, rise in lake levels, and lately anthropogenic disturbance. This data highlights the complexity of the hydrological balance of the region and the need to further study this dune-lake landscape.