Abstract
Volume 04 (4) 1997
Influences of humans and ENSO on fire history of Austrocedrus chilensis woodlands in northern Patagonia, Argentina
Thomas KITZBERGER, Departamento de Ecologia, Universidad Nacional del Comahue, Estafeta Postal Universidad, 8400 Bariloche, Argentina, e-mail: kitzberg@cab.cnea.edu.ar
Thomas T. VEBLEN, Department of Geography, University of Colorado, Campus Box 260, Boulder, Colorado 80309, USA, e-mail: veblen@spot.colorado.edu
Abstract:
In northern Patagonia, Argentina, five areas near the ecotone of xeric woodlands and the steppe were sampled for fire history to assess spatial and temporal variations in fire regimes. A total of 214 fire-scar samples from the xeric conifer Austrocedrus chilensis (D. Don) Florin & Bout. yielded 430 cross-dated fire dates from AD 1439 to 1989. A reginal trend of increasing fire frequency during the latter half of th 19th century coincides with increased native American occupation of the area. There is a marked decline in fire frequency following the demise of the native American population in the late 1800s and in association with increasingly effective fire suppression during the 20th century. Inter-site variations in the frequency of small fires appear to reflect intra-regional variations in human activities. In contrast, regional synchroneity of years of more widespread fires implies greater climatic control of major burning events. El Ninő-Southern Oscillation (ENSO) events are a major influence on the subtropical anticlone of the southeast Pacific that affects weather in northern Patagonia, and, at a time scale of fifty years, periods of widespread fire closely track increased ENSO events as determined from historical sources and tree-ring reconstruction. However, the multi-decadal relationship of increased frequency of years of widespread fire and increased ENSO activity could only be tentavely established due to the relatively small number of pre-1800 fire dates and the potentially confounding influence of variations in human activities. This tentative association of increased fire occurence with greater climatic variability at a fifty-year time scale complements earlier research that relates more widespread fire to droughts preceded by years of above-average moisture availability at time scales of 1 to 4 years.
Keywords :
Austrocedrus, dendroecolgy, fire history, Patagonia, climatic variations, land use.
Pages: 508-520