Aims Volcanic eruptions play an important role in vegetation dynamics
and its historical range of variability. However, large events are
infrequent and eruptions with significant imprint in today vegetation
occurred far in the past, limiting our understanding of ecological
process. Volcanoes in southern Andes have been active during the last 10
ka, and support unique ecosystems such as the Araucaria-Nothofagus
forest as part of the Valdivian Temperate Rainforest Hotspot. Araucaria
is an endangered species, strongly fragmented and well adapted to
disturbances. Yet it was suggested that volcanism might have increased
the fragmentation of its populations. To provide an insight into the
vegetation responses to past volcanic disturbances, a paleoecological
study was conducted to assess the role of volcanic disturbance on the
vegetation dynamics and if the current fragmentation has been caused by
volcanism. Location Araucaria forest-steppe ecotone in northern
Patagonia. Methods Pollen and tephra analysis from a sedimentary record.
Results During the last 9 kyr, 39 tephrafall buried the vegetation
around Lake Relem, more frequently between 4-2 ka. The vegetation was
sensitive to small tephrafall but seldom caused significant changes.
However, the large eruption of Sollipulli-Alpehue (~3
ka) might change the environmental conditions affecting severely the
forest and grassland, as suggested by the pollen record. Ephedra
dominated early successional stage, perhaps facilitating Nothofagus
regeneration recovering original condition after ~500
years. Slight increase of pollen percentage from Araucaria and
Nothofagus obliqua-type could be indicative of sparse biological
legacies distributed in the landscape. The analysis showed that
vegetation resisted without permanent changes, recovering relatively
fast after the large eruption. Conclusion The relative stability of
Araucaria pollen in the study area after several tephrafall suggests no
change in its past geographical distribution at the current
forest-steppe ecotone, thus I found no evidence that volcanic eruptions
would have affected its current conservation status.
Vegetation responses to past volcanic disturbances at the Araucaria araucana forest-steppe ecotone in northern Patagonia
