Satellite estimation of tropical secondary forest above-ground biomass: data from Brazil and Bolivia

This paper reports on a test of the ability to estimate above-ground biomass of tropical secondary forest from canopy spectral re ectance using satellite optical data. Landsat Thematic Mapper data were acquired concurrent with Ž eld surveys conducted in secondary forest fallows nearManaus, Brazil and Santa Cruz de la Sierra, Bolivia. Measurements of age and above-ground live biomass were made in 34 regrowth stands. Satellite data were converted to surface re ectances and compared with regrowth stand age, biomass and structural variables. Among the Brazilian stands, signiŽ cant relationships were observed between middle-infrared re ectance and stand age, height, volume and biomass. The canopy re ectance–biomass relationship saturated at around 15.0kgm Õ 2, or over 15 years of age (r> 0.80, p< 0.01). In the Bolivian study area, no signiŽ cant relationship between canopy spectral re ectance and biomass was observed.These contrasting results are probably caused by a low Sun angle during the satellite measurements from Bolivia. However, regrowth structural and general compositional di€ erences between the two study areas could explain the lack of a signiŽ cant relationship in Bolivia. The results demonstratea current potential for biomass estimation of secondary forests with satellite optical data in some, but not all, tropical regions. A discussion of the potential for regional extrapolationof spectral relationships and future satellite imagery is included.