| Forest fire incidence, effects, characteristics and implications were investigated from 1996 to 1998 in a series of studies that combined field work with satellite imagery analyses.; Investigation of an extensive tract of previously burned forest showed that fire had burned more than 70% of the forest more than once and led to the conclusion that recurrent fire was capable of devastating large tracts of forest. The study indicated that burned forests become more susceptible to recurrent fire with each fire event in a classic example of positive feedback.; Subsequent investigation of a complex of fires that burned in the study region in December 1997 illustrated the fire dynamic within the heterogeneous landscape of forest patches of different bum histories. Fuel loads of all sizes increased with each recurrent burn. Furthermore, the combination of microclimate changes and fuel load/structure in previously burned forests resulted in significantly increased flame lengths, flame depths, spread rates, residence times and fireline intensities. The study showed that there is a positive feedback in fire severity as well as future fire susceptibility in these forests.; To increase the scope of the fire studies to the landscape level, a new remote sensing technique for detecting closed canopy tropical forests damaged by low intensity ground fires was developed. The methodology allows a sub-pixel decomposition of Landsat TM imagery into 'endmembers' that correspond to vegetation, canopy shade and non-photosynthetic vegetation (NPV) fractions. Detection of burned forests relies on the small but significant NPV fraction increase that occurs in fire impacted forests.; A multitemporal landscape analysis of fire occurrence was conducted for two separate regions (Paragominas and Tailandia, total area 3,920 km2) to address the questions of fire frequency and land cover change. Both regions were shown to have fire-return-intervals of less than 15 years. If left unchanged, this fire frequency will eradicate the remaining forests from the landscape of the study regions. This same fire dynamic is shown to exist throughout an extensive portion of the Amazon (580,000 km 2), posing an extreme threat to the region's forests and the likelihood of globally significant emissions of CO2. |
