Fire history of Nothofagus pumilio forests along a precipitation gradient in southern Patagonian Andes of Argentina

BIANCHI, LUCAS O.; RADINS, MARCOS; MUNDO, IGNACIO A.; BONADA, ANABELA; VILLALBA, RICARDO

Mendoza

Congreso; Ameridendro 2016 - Third American Dendrochronology Conference; 2016

IANIGLA - Tree Ring Society

Fire is a frequent disturbance in the Nothofagus pumilio forests across the southern Patagonian Andes. However, historical records of fire occurrence in the region are scarce. Most fire histories in the Patagonian Andes have been derived from fire scars in conifers; broadleaf species have rarely been used. Recent studies have shown the potential of the deciduous N. pumilio,the dominant tree in the southern Andes, for developing treering based records of fire history in the region. In this study, we reconstructed the fire history in N. pumilio forests along a precipitation gradient from the dry forest-steppe ecotone around Lago Viedma (49°29´S) to the humid forests in the vicinity of Laguna del Desierto (49°05´S). We analyzed a total of 153 firescarred partial cross-sections from 8 sites along this precipitation gradient. Although several fires were dendrochronologically dated across the region, two major events were recorded for the years 1924 and 1935 in the dry and wet sectors, respectively. The total area burned during the fires is related to the fire location along the steep rainfall gradient: fires in the eastern dry sites cover larger areas (more than 500 ha) than those recorded in the western and more humid sites (less than 5 ha) reflecting the large influence of moisture in modulating fire size. To determine the influences of climatic variation on fire occurrence, we compare the scarce climatic records in the region with our fire history. Although fire occurrence is closely related to human activities, we found fire years associated with warm and dry summers.