INVESTIGADORES
KITZBERGER Thomas
artículos
Título:
Landscape influences on occurrence and spread of wildfires in Patagonian forests and shrublands
Autor/es:
MERMOZ, M.; KITZBERGER, T.; VEBLEN, T.T.
Revista:
ECOLOGY
Editorial:
ECOLOGICAL SOC AMER
Referencias:
Año: 2005 vol. 86 p. 2705 - 2715
ISSN:
0012-9658
Resumen:
Spatial heterogeneity of vegetation types and the abiotic environment can
influence the occurrence and spread of wildfires, but in some landscapes the importance
of these effects varies under conditions of severe fire weather. In the northern Patagonian
landscape of forests and shrublands we examined the effects of vegetation type (tall forest
vs. tall shrubland) and abiotic factors (elevation, topography, and precipitation) on fire
occurrence at a broad scale and on fire spread at a fine scale. We used satellite images
(19851999) and aerial photography (19501999) to map fires in relation to pre-burn
vegetation type and abiotic factors. Fire extent is greatest at intermediate elevations and
locations of intermediate precipitation. Fire extent is limited by lack of fuel quantity at the
lower end of the precipitation gradient and by infrequent or insufficient fuel desiccation at
the upper end. Tall shrublands are proportionally more affected by fire than are adjacent
mesic forests of Nothofagus dombeyi and N. pumilio. Patches of subalpine forests often
tend to serve as natural fire breaks, except under the most severe fire weather. Tall shrublands
are dominated by species that resprout vigorously so that fuels quickly recover. In contrast,
forests are dominated by species dependent on seed reproduction that sometimes fails after
severe fires so that shrublands tend to replace burned forests. The greater propensity of
shrublands to burn is a positive feedback that is favorable to fire and that accelerates the
replacement of forest by shrublands. Infrequently occurring severe weather is important in
the burning of otherwise relatively fire-resistant subalpine forests. Past burning, associated
both with drought and early forest clearing, expanded shrublands at the expense of forests
so that in the modern landscape an increase in anthropogenic ignitions and the positive
feedback of fire and shrublands are synergistically accelerating conversion from forest to
shrubland.