IIMYC   23581
INSTITUTO DE INVESTIGACIONES MARINAS Y COSTERAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Vegetation and environmental changes in extra-Andean Patagonia, Argentina
Autor/es:
MANCINI, M.V., BAMONTE, FP, MARCOS MA
Reunión:
Congreso; 4th Southern Deserts Conference; 2014
Resumen:
Extra-Andean Patagonia is a wide region with arid and semiarid climatic conditions. In this region mean annual precipitation is lower than 200 mm due to rainshadow effect produced by the Andes. Spatial variation in rainfall is one of the causes of the vegetation patchiness which is represented by grass, shrub and dwarf-shrub steppes. Modern pollen-vegetation-climate relationships from different precipitation gradients were established to be used as modern analogous to understand the vegetation dynamic particularly during the Holocene. According to the current correlation between precipitation and wind speed, changes revealed by the pollen records are interpreted as indicative of variations in the intensity and / or position of the westerlies; the moist air influence Atlantic is more pronounced towards the east. These atmospheric circulation changes led to drifts of the forest-steppe ecotone and in steppes composition. Paleoenvironmental reconstructions are based on pollen records comparison from different depositional environments such as ?mallines?, lakes and archaeological sites (caves and rockshelters). Palynology applied to archaeology generates essential information that when is combined and integrated properly lead to improve the understanding of the landscape in the past. An important consideration is the degree of stratigraphic resolution of the archaeological sequences. Comparison of fossil pollen records from archaeological sites and those analyzed from other deposits strengthen paleoclimatic reconstructions, assess similarities and differences in the distribution patterns of vegetation and their relationship with regional (climate) and /or local (topography, substrate, disturbance) changes. Environmental reconstruction presents similar trends from the Pleistocene-Holocene transition. Human occupation since Late Pleistocene and early Holocene in the southern steppes suggest that humans utilized the area during times of increased moisture. The major human impact on the vegetation began around 150 years ago with the European settlement; overgrazing led to changes especially in the grass steppe. The agreement between these trends and others palaeoenvironmental interpretations based on pollen, charcoal and sedimentological records, suggests that the reconstructed features reflect large-scale climatological patterns over Patagonia. However, stratigraphical and chronological discontinuities, with unrepresented processes, limit the knowledge of the environment change during the past. A few continuous lacustrine records of the climatic and ecological history are available. Other palaeo-environmental reconstructions are needed to achieve a better understanding of the regional changes that allow to identify climatic events, and to contribute with new insights into the role of atmospheric circulation at these latitudes. For these reasons it is recommended for future studies, increasing high resolution palaeoecological records and analyze continuous sequences of the steppe to compare with available reconstructions. Currently it is being analyzed the pollen content of a ?mallin? sequence in the semiarid steppe of southern Patagonia.