Abstract
Plant Palaeocommunities of Central Tierra del Fuego during the Early and Late Holocene. This study presents new data for the history of vegetation of central Tierra del Fuego. The goal is to identify the vegetation types before and after the middle Holocene, having in mind previous studies proposing a forest expansion started in early Holocene times following a SW-NE precipitation gradient. Two segments of a Sphagnum peat bog profile (R-2: 54°32’S, 67°04’W), now surrounded by the Nothofagus pumilio (Poepp et Endl.) deciduous forest, were analyzed. The following results were obtained through the modern analogs method: steppe and woodland were found in the older segment and open and closed forest in the younger segment. We concluded that an asynchronous establishment of the involved plant communities occurred. In fact, ca. 7000 years BP, while in other sites of the central island forests were already established, in R-2, located eastwards from those sites, the steppe-woodland ecotone dominated. On the other hand, from ca. 2000 years AP to modern times both open and closed forests covered the central area. The humidity carried by the Southern Westerlies could have influenced the late development of Nothofagus. This study represents an advancement in the knowledge of the vegetation history, and provides new data about the asynchrony in the establishment of communities.
Highlights
A los 2000 años AP el bosque cerrado se había establecido en la zona del Canal de Beagle, indicando descenso de la temperatura y aumento de la humedad, así como también en el Lago Fagnano, en el Lago Yehuin y en el sitio Río Claro (54°22’S, 68°W) (Burry et al, 2003)
El modelo actual (Fig. 3) muestra los tipos polínicos hallados en superficie y su abundancia a lo largo de la transecta con orientación SW-NE
Peatbog accumulation rate in the Andes of Tierra del Fuego and Patagonia (Argentina and Chile) during the last 43,000 years
Summary
Total sum of squares de Empetrum y de Rosaceae, principalmente del género Acaena, y hasta un 7% de Poaceae. Hay bajos valores de especies de suelos húmedos y las especies herbáceas y arbustivas están prácticamente ausentes. Se observó una mayor concentración polínica en el segmento superior del perfil. El modelo actual (Fig. 3) muestra los tipos polínicos hallados en superficie y su abundancia a lo largo de la transecta con orientación SW-NE. La composición de las muestras y la relación de los tipos polínicos dominantes, Poaceae y Nothofagus, permitió identificar la estepa, el parque, el bosque deciduo abierto y el. Porcentajes de frecuencia de los tipos polínicos Poaceae y Nothofagus en las distintas unidades de vegetación, según un modelo actual (Trivi et al, 2006)
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