Estimation of combustion completeness based on fire‐induced spectral reflectance changes in a dambo grassland (Western Province, Zambia)

Abstract

An experimental burn was performed in a dambo grassland, in the Western Province of Zambia, during the SAFARI 2000 Third Intensive Field Campaign. The main goal of this study was to analyse the possibility of estimating combustion completeness based on fire‐induced spectral reflectance changes in surface. Inverse, nonlinear relationships were obtained between combustion completeness and pre‐fire to post‐fire spectral reflectance changes, in the green, red, and near‐infrared spectral domains (equivalent to Landsat 7 ETM+ channels 2, 3, and 4). The coefficient of determination (R ²) varied from 0.50 for channel 4, to 0.57 for channel 3, and all the regressions were significant at the 95% confidence level. Thus, it may be feasible to treat combustion completeness as a variable whose values can be remotely estimated. However, its relationship with fire‐induced spectral reflectance changes is expected to exhibit some dependence on vegetation structure. The experimental burn was performed simultaneously with overpasses from the Terra satellite, and from the NASA ER‐2 research airplane carrying the 50‐channel MODIS Airborne Simulator (MAS) image spectrometer. Our results may be used in conjunction with imagery from these sensors, to support the development of operational approaches for combustion completeness estimation from remotely sensed data.

Acknowledgements

We thank the Luso‐American Foundation for the Development, which provided financial support to the participation of J.M.C.P., A.C.L.S., and J.M.N.S. in the Third Intensive Field Campaign of SAFARI 2000. We are also grateful to Dr Darold Ward, USDA Forest Service, for the logistic support to our activities. He and Natasha Ribeiro (University Eduardo Mondlane, Mozambique) also helped with fieldwork. A.C.L.S. and J.M.N.S. were funded by the Foundation for Science and Technology, Ministry for Science and Technology, through doctoral grants SFRH/BD/891/2000 and SFRH/BD/1026/2000, respectively. This research was performed under Project POCTI/CTA/33582/99 (Reduction of uncertainties in estimates of atmospheric emissions from fires in southern Africa), Foundation for Science and Technology, Ministry for Science and Technology, Portugal. We are grateful to the Government of Zambia for hosting our activities. This study was part of the SAFARI 2000 Southern African Regional Science Initiative.