Late-Holocene vegetation dynamics and disturbance regimes in north Patagonia Argentina (40°S)

Natural disturbance processes such as volcanic eruptions, fire and human activities are important vegetation drivers in north Patagonia. Here, we tested the impact of volcanic ash fall and fire on vegetation composition analysing two sediment records, Lake Avutarda and Lake Bruja, located in the forest-steppe transition at 40 degrees S. In addition, our analysis provides the first account on the history of Nothofagus alpina at its eastern distribution limits. Our results comprise the last 3000 years, indicating the persistence of the vegetation despite evident volcanic activity documented by numerous tephra layers in both records. Eleven fire episodes were identified, while redundancy analysis indicates a non-significant influence of fire activity on the vegetation. The population increase of Nothofagus alpina represents the most important change in vegetation composition in the last three millennia. We speculate that the presumed change in climate, which led to the expansion of Austrocedrus chilensis south of the study area, also caused the increase of Nothofagus alpina populations in the region.