Exotic species spread after fire in a forest of Nothofagus dombeyi and Austrocedrus chilensis in Patagonia, Argentina

MELISA BLACKHALL; ESTELA RAFFAELE; THOMAS T. VEBLEN

S. C. de Bariloche

Congreso; VI Southern Connection Congress; 2010

Universidad Nacional del Comahue, CONICET, INTA

Species invasions are often associated with disturbance events. In northwest Patagonia, two of the most important disturbances are fire and introduced herbivores. In 1999 a severe wildfire affected a Nothofagus dombeyi and Austrocedrus chilensis forest, where introduced cattle graze freely. Seven years after the fire we determined the cover of exotic and native forbs in the burned site (inside and outside cattle exclosures) and in an adjacent unburned site. Cover of native forbs was significantly higher than exotic forbs at the unburned site. At the burned site the cover of exotic forbs was higher than native forbs, but no differences were found between plots with and without cattle. Exotic species account for 76.2% of the total cover of forbs at the burned site. Of the total exotic forb cover, 83.6% belongs to species with aerial structures that lose their structure and dieback during the late summer months of highest fire risk. Thus, burning alone favors the spread of exotic forbs and the presence of dry fine fuels, but cattle did not significantly affect the abundance of exotic forbs in the burned or unburnt forest.