Holocene vegetation and climate changes from a peat pollen record of the forest – steppe ecotone, Southwest of Patagonia (Argentina)

Pollen analysis from a peat-bog sequence located at 50° 24′ S, 72° 42′ W in the Subantarctic forest – Patagonian steppe ecotone gives information about vegetation and climate changes in Southwestern Patagonia since the glacier retreat. After 11 000 cal yr BP a change from grass steppe to open Nothofagus forest indicates that climatic conditions became rapidly warmer. Development of a closed Nothofagus forest between 5800 and 3200 cal yr BP is interpreted as precipitation increase. During the late Holocene colder climate conditions prevail in response to Neoglacial events. After ca 3000 cal yr BP Nothofagus forest became opener, and after 800 cal yr BP grass steppe expanded. Changes in the forest-steppe ecotone composition as well as the ecotone longitudinal shifts suggest changes in temperature and precipitation. Present-day mean annual precipitation between 300 and 400 mm is associated with grass steppe, and 500–600 mm with a greater forest representation. During the last century, low presence of forest in the area may be related to European settlement and repeated flooding caused by periodic advances of Perito Moreno glacier.