Fire history in Southern Patagonia: human and climate influences on fire activity in Nothofagus pumilio forests

MUNDO, I.A.; KITZBERGER, T.; RIPALTA, A.; VEBLEN, T.T.; PARITSIS, J.; VILLALBA, R.; HOLZ, A.

Mendoza

Conferencia; AmeriDendro 2016 - Third American Dendrochronology Conference; 2016

IANIGLA-CONICET

Fire is a major disturbance affecting forests worldwide with significant economic, social and ecological impacts. In Patagonia, fire history has been reconstructed for different species by dendrochronological techniques. However, the temporal and spatial patterns of fire occurrence and the associated climatic and anthropogenic drivers in the Nothofagus pumilio dominated forests of Patagonia are practically unknown. This study applies dendrochronological techniques to reconstruct fire history in N. pumilio forests of southern Patagonia, to determine the relationship between fire occurrence and climate variability and the Southern Annular Mode (SAM), and to relate fire ignitions to the human occupation history in this area. 386 partial cross-sections with fire-scars were collected from sites between Lago Guacho in Chubut (43°50?S), Argentina and Lago Pinto (52°00?S) in the Magallanes region of Chile. Eighteen sites have been analyzed and the fire scars correctly dated with the oldest fire occurring in 1791 in Río Lácteo. A regional trend of high fire frequency was observed during the 20th century. This concentration of fire events is consistent with the pattern of human occupation and colonization in southern Patagonia during the same period. Site-level composite fire histories indicated high inter-site variability. However, 12 events occurred synchronously in at least 2 sites and 5 fire years were coincident in at least 3 sites. Among these years, 1961, 1962 and 1983 fire events were coincident with warm summer heat waves detected by means of the Twentieth Century Reanalysis version 2 (20CRv2). Additionally, both the 1962-1963 and 1983-1984 growing seasons had at least three months with positive departures of Marshall?s SAM Index. This suggests widespread fire occurrence in southern Patagonia is coincident with droughts which are partially influenced by positive phases of SAM. These results reveal the superimposed influence of climate and human activities on the fire history of these southern Patagonian forests.