CHARACTERIZING CARBON IN A NORTHERN FOREST BY USING SIR-C X-SAR IMAGERY/

A significant large-scale question in ecology and earth systems scienc e pertains to the amount of carbon (C) stored in terrestrial vegetatio n. In this paper, a synthetic aperture radar (SAR)-based methodology i s developed and evaluated for quantification of several key vegetative C components-both natural and human induced-of the northern forest. S pecifically, the methodology provides estimates of C stored in living forest vegetation, above-ground C gain from annual growth (aboveground net primary productivity, or ANPP), and C removal due to managed fore st disturbance in the form of clear-cutting. The inputs are shuttle im aging radar (SIR)-C/X-SAR-derived terrain classifications, SIR-C/X-SAR -derived biomass estimation, and allometric relations and equations de veloped for the northern hardwood and conifer forest in general and fr om local test stand data. Results are mapped quantitatively in the ima ge domain for above-ground C storage, below-ground C storage, above- t o below-ground ratios, total C in living woody vegetation, and forest absolute and relative ANPP rates. Numeric estimates also are extracted from each of these in tabular form; for example, results show that th e forested parts of the sampled area contain 2.73X10(9) kg of abovegro und C and 4.86X10(8) kg of below-ground C in 51,448 ha. When combined with a SAR-derived classification, similar quantifications can be extr acted for each of the several forest communities present in the region . Estimates of forest ANPP show that it ranges from 0.5 kg/m(2)/yr of biomass to 2.7 kg/m(2)/yr in the test site, with an average of 1.09 kg /m(2)/yr. Estimation of C removal due to clear-cutting is done by suin g multidate classifications of SAR imagery and a procedure including i mage differencing and decision rules. Clear-cuts that were made betwee n SIR-C/X-SAR Shuttle Radar Laboratory (SRL)-1 (April) and SRL-2 (Octo ber) are identified by differencing the classified imagery. When combi ned with the SAR-derived biomass image, results show that an estimated 300 ha of forest with 6.02X10(6) kg of C were removed in this 6-month period. (C) Elsevier Science Inc., 1998.