Cambios de la vegetación en la Cuenca de la Laguna Merín, Uruguay, durante los últimos ca. 2000 cal. años AP

Abstract

The palynological analysis from a sedimentary sequence from the wetland Paso Barranca-India Muerta at Laguna Merín Basin (RB1 core, 33°40’36”S-53°49’15”W) of southeastern Uruguay, allowed to reconstruct the vegetation history during the last ca. 2000 cal. yr BP. The modern pollen-vegetation relationship from Laguna Merín Basin at regional scale was used for the interpretation of RB1 fossil record. Results revealed that during the late Holocene grassland vegetation dominated at Paso Barranca-India Muerta, together with the development of riparian forests, palm grooves and freshwater marshes. This suggests a diverse vegetation on the area under either humid climatic conditions or a positive water balance. However, the freshwater marsh showed fluctuations in depth and extent, probably as a response to local soil water content changes. Since ca. 2000 cal. yr BP the marsh water level changes displayed variability, with increased levels at ca. 700 cal. yr BP. Thereafter, conditions remained relatively steady until ca. 300 cal. yr BP, when the marsh water level progressively increased until reaching the current conditions. The local soil water content changes would have responded to the late Holocene climate variability suggested for southeastern Uruguay, even under humid conditions proposed for the campos region of the Río de la Plata grasslands. The vegetation changes inferred from the palynological analysis could not be related to the anthropogenic changes introduced by the prehispanic populations in the region. This work substantially improves our knowledge of the late Holocene vegetation and climate conditions in the Laguna Merín Basin.