Fuel moisture and fuel productivity are two primary drivers of fire behavior and, at landscape scales, are not easily measured. We approximate them using two topographically-controlled surrogate variables that are central to site water balance: potential evapotranspiration (PET) and actual evapotranspiration (AET). PET can be used to estimate fuel moisture during the fire season and was estimated from solar radiation. AET is a correlate of productivity and can be used to estimate fuel load after the growing season. Previous studies reported that fuel moisture and fuel availability, also estimated from surrogate variables, explained 68% the variation of burned area. This study explores the potential of these two water balance elements to explain variation in fire behavior at the landscape scale. Fire behavior was described by fire radiative energy (FRE, kJ m-2), estimated as the integral of high resolution time-sequence airborne infrared imagery from two different prescribed-fires. In turn, FRE was used to estimate total fuel consumption from relationships reported in the literature. PET and AET were estimated using a GIS-based water budget model. Field measurements of the fuel prior and after combustion, served to validate fuel consumption estimated from heat release.
Results/Conclusions
Preliminary results reveal that, at the pixel level, the links between PET and AET and fire heat output were weak, perhaps being dominated by other fine-scale local processes (e.g., hydrology, decomposition). At a coarse scale, FRE increased with both PET and AET. In conclusion, future work should be directed towards improving site water balance estimates by inclusion of a hydrological model that accounts for small-scale soil moisture and, thus, fuel moisture and fuel decomposition dynamics.
