Fire on the Amazon Forest_Cerrado transition

Ernesto Alvarado alvarado at
Fri Dec 12 00:56:11 EST 1997

Dear All,

The following abstract is from a paper that I presented last year at the
Conference on Fire and Forest Meteorology, October 27-31,1996 in Lorne,
Australia. The paper will be published in the conference proceedings in the
near future. I considered that the paper can contribute to the  discussion
on fires in the tropical forest currently  going on on several fronts. A
postscript copy of the paper can be  checked out in the "Special Features"
section at The original file is in
WordPerfect for Macintosh and the translation to postscript may have
changed some of the format. Feel free to drop me a line if you have any
trouble reading the postscript file and I'll see what can I do.


Ernesto C. Alvarado		email: alvarado at
CFR-University of Washington	Tel: (206) 553-7815
Mail Box 352100			Fax: (206) 553-7709
Seattle, WA 98195

Title: Fire Along the Transition Between the Amazon Forest and the
Cerrado Ecosystems

Authors: Gustavo Hees de Negreiros, David Sandberg, Ernesto Alvarado,
Thomas Hinckley, Daniel C. Nepstad, and Marcos Pereira


Most of the fires in Amazonia happen along an arc of deforestation,
which generally follows the transition between the Amazon evergreen forests
and the savannas (cerrado).  The evergreen primary forest acts as a giant
fire break, while the cerrado has adapted to frequent fires.  The
transitional zone between these two ecosystems is a fragile boundary
controlled by very dynamic ecosystem processes.  It is also an area with
heavy pressures from human settlements that use fire as a way to clear and
manage the land.  Canopy disturbance of the primary forest due to increased
selective logging and deforestation, along with extended droughts, alters
the hydrological equilibrium of this ecosystem and therefore, the ecotone.
High temperatures and very low relative humidity in disturbed stands
increase the flammability of the primary forest.  The deep rooting systems
have an important role in supplying water during the dry season.  As
precipitation decreases, the primary forest is able to tap deep soil water;
however, if the water supply is interrupted during an exceptionally dry
year, the vegetation can dry and suffer leaf loss.  Light penetration then
increases, fuel moisture decreases, and fuels become dangerously flammable.
This paper presents the main ideas of a fire susceptibility model that is
being developed for the region.

Key words: Fire, Forest Savanna Ecotone, Water Stress, Rooting Depth, GIS,
Modeling, Tropics, Brazil.

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