MAPPING OF BOREAL FOREST BIOMASS FROM SPACEBORNE SYNTHETIC-APERTURE RADAR

As part of the Boreal-Ecosystem Atmosphere Study (BOREAS), an investig ation is being made of the use of satellite data including shuttle ima ging radar-C (SIR-C), X-band synthetic aperture radar (XSAR), and Land sat-Thematic Mapper data for estimating total and component abovegroun d woody biomass in boreal forest study sites in Canada. The goal of th is paper is to present progress in mapping above ground woody biomass over portions of the BOREAS southern study area using spaceborne senso r data. Relationships of backscatter to total biomass and total biomas s to foliage, branch, and bale biomass are used to estimate biomass ac ross the landscape. The procedure involves image classification with S AR and Landsat data and development of simple mapping techniques using combinations of SAR channels. The analysis uses measurements from for est stands representing a range of biomass and structures. Field measu rements included plot level mensuration (species, stem diameter, heigh t, density, and basal area) and tree geometry measurements (leaf, bran ch, bole size, and angle distributions). The results indicate that abo veground biomass can be estimated to within about 1.6 kg/m(2) and up t o about 15 kg/m(2) across the SIR-C image evaluated. A general method produced equivalent results with those obtained by treating forest typ e (pine, spruce, and aspen) separately. The biomass mapping was extend ed to bole, branch, and foliage components from relationships with tot al aboveground biomass developed from detailed tree measurements. Aver age biomass within the imaged area was estimated to be about 7.3 kg/m( 2) with biomass components of bole, branch, and foliage comprising 83, 12, and 5% of the total. Examination of the scaling of biomass estima tes from remote sensing images of varying resolution shows that inform ation at scales useful for ecosystem models can be obtained. In additi on, the biomass estimation technique provides similar information at d ifferent image resolutions.