A Look at Amazon Basin Seasonal Dynamics with the Biophysical ...

Mapping Biomass Loss from Forest Fires in a Dense Forest of Western ParáAne Alencar, Oswaldo de Carvalho Jr., Daniel Nepstad, Richard Houghton, Sanae HyashiDuring dry years, carbon emissions from Amazon forest understory fires may exceed thoseassociated with deforestation, but remote detection mechanisms for fire-induced biomass loss areyet to be developed. Little is known about the spectral properties of forest fire scars and theirrelationship to changes in ground-level biomass. In this study, remote sensing transformationtechniques were used to determine spectrally fire disturbance levels and response to biomassloss. The study site was a ~250 km 2 forest understory fire scar resulting from the1997/1998 ElNino event, located 100 km south of Santarém, Western Pará. Field interviews were conducted todetermine the burning and logging history of the fire scar, and showed three levels of burning andlogging intensity. Subsequently, biomass, fuel load, and LAI were measured in four 500x 500 mplots - three burning intensity levels and a primary forest control plot. Aboveground biomass was170, 184, 370, and 423 Mg ha -1 in forests with heavy, moderate, light, and no fire history,respectively. A multi-date analysis using Landsat TM and ETM images from 1997, 1999 and 2001identified changes in the spectral signal before, during and after the burning event. Preliminaryresults indicate that, when compared to field measures of biomass and LAI, Landsat bands 4 and5 provided the most accurate detection of burn intensity. This method reveals the potential formonitoring fire effects on dense forest biomass in Amazonia using remote sensing techniques.1 Instituto de Pesquisa Ambietal da Amazônia2 Woods Hole Research Center* Corresponding author: Avenida Nazare 669. Belem, PA - Brazil 66035-170Email:ane@amazon.com.br