Abstract
AIRSAR data gathered in winter, spring, and summer over the Bonanza Creek Experimental Forest, near Fairbanks, Alaska are compared to estimates of whole-tree aboveground dry biomass from 21 forest stands and 2 clear-cuts. Using empirical relationships, biomass values are predicted from the radar at various frequencies and polarizations and compared to actual biomass values. Predicted biomass levels are most accurate at P-band. At that frequency, the radar discriminates 7 biomass levels, up to the maximum observable biomass level for these forests, with 18% error. Within these 7 biomass levels data dispersion is large because of significant inner-stand spatial variations in biomass, interactions of the radar signals with a spatially varying three-dimensional structure of the canopy, as well as uncertainties associated with the estimation of stand biomass from empirical equations. Multiple incidence angle data also reveal that the incidence angle /spl theta//sub i/ of the radar illumination affects the retrieval of biomass from the radar data even at HV-polarization when /spl theta//sub i/>50/spl deg/ or /spl theta//sub i/ >
Highlights
In undisturbed, even-aged, mono-specie pine plantations in temperate regions with nearly level topography, airborne radar experiments showed radar backscatter is positively correlated with total aboveground dry biomass until it saturates at a level which is higher with increasing radar wavelengths [l-21
Standing aboveground tree biomass ranges from 92 t o 183 tons/ha for the hardwood stands up t o 249 tons/ha for white spruce stands, and 2-11 tons/ha for black spruce stands
Floodplain forests vary from productive stands of balsam poplar and white spruce forming on river alluvium, permafrost-free soils, t o slow-growing black spruce and bogs occupying older terraces underlained by permafrost
Summary
AIRSAR 191 imaged BCEF on March 13, 17 and 19 of 1988 when the forest changed from frozen (March 11) t o thawed conditions (March 13) and back t o frozen conditions (March 17) due t o a transition t o unusually warm air-temperatures for the season [lo]. On May 4 , 6 and 7 of 1991, AIRSAR overflew the study site when the forest changed from flooded (May 4) t o unflooded conditions (May 6-7) with the formation and subsequent disappearance of ice jams in the Tanana river. AIRSAR overflew again BCEF in July 1993 when the forest had a fully developed canopy under dry climatic conditions. The multidate SAR were subsequently co-registered to a SPOT scene
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