Abstract
Paleoecological studies in Patagonia provide information about vegetation and climate changes occurred during the Holocene. The climatic evolution of this region offers a unique opportunity to study the environmental variability as well as the ecosystem variations. The dynamic of the forest ecosystems is modulated by the occurrence of disturbances. Fires are one of the most important disturbances in temperate forest ecosystems, and its study allows contrasting independently about the changes experienced by ecosystems. In addition, in Patagonia, environmental and postglacial vegetation changes have been determined by variations in the temperature and westerlies winds. In order to reconstruct changes experienced by the forest ecosystem and patterns of plant diversity during the Holocene, in relation to Postglacial dynamics, natural and anthropic disturbances in the Lake Argentino, pollen and charcoal were studied in a sedimentary sequence at Península Avellaneda. Pollen assemblages suggest non-cyclic changes in plant diversity during the Holocene. The highly diverse cold grass-shrub communities dominated the area up to the Early Holocene, when they were displaced upland by less diverse forest and steppes. Also, The Early and Midd-Holocene was characterized by opposite variations of hydric balance between Andean and extra-andean plant communities present between 48° and 50° S, whereas fire activity occurs synchronously between forest (Andean) and steppe communities (Extra-andean). Late Holocene is characterized by different proxy signals depending on the geographical location of the paleoecological records. To conclude, this work provides a better understanding of the fossil pollen record by its comparison with modern surface pollen samples along an altitudinal vegetation gradient.
Highlights
El clima y el régimen de disturbios son dos de los principales agentes que afectan de manera diferencial la coexistencia del conjunto de especies que conforman un determinado ecosistema (Wilson, 2011) y por lo tanto representan agentes fundamentales que modulan su dinámica
Paleoecological studies in Patagonia provide information about vegetation and climate changes occurred during the Holocene
The dynamic of the forest ecosystems is modulated by the occurrence of disturbances
Summary
El clima y el régimen de disturbios son dos de los principales agentes que afectan de manera diferencial la coexistencia del conjunto de especies que conforman un determinado ecosistema (Wilson, 2011) y por lo tanto representan agentes fundamentales que modulan su dinámica. El estudio de registros polínicos y de carbón vegetal sedimentario de cuencas lacustres, mallines y turberas ha sido fundamental para inferir los cambios que se han producido en los ecosistemas patagónicos durante el Cuaternario tardío. Estos permiten no solo ajustar la identidad taxonómica de algunos taxones polínicos (macrofósiles vegetales), sino también brindar información sobre la ocurrencia de eventos de disturbio por fuego (carbón vegetal sedimentario) y su variabilidad en el tiempo (régimen). En primer lugar se presenta un modelo de representación polínica actual del gradiente de vegetación altitudinal, y luego el análisis del registro polínico y de carbón vegetal sedimentario de una secuencia de turbera localizada en la península Avellaneda (Parque Nacional Los Glaciares, Santa Cruz). Las inferencias paleoambientales a partir de este sitio son discutidas en el contexto de otras reconstrucciones existentes para la cuenca del lago Argentino (Fig. 1)
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