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Abstract. This paper reports on a test of the ability to estimate above-ground biomass of tropical secondary forest from canopy spectral re ectance using satel-lite optical data. Landsat Thematic Mapper data were acquired concurrent with 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, signi 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 signi 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 composi-tional di erences between the two study areas could explain the lack of a signi c-ant 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. 1.
Marc K. Steininger (Sat,) studied this question.