Radar estimates of aboveground biomass in boreal forests of interior Alaska
Radar estimates of aboveground biomass in boreal forests of interior Alaska
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DOI：
10.1109/36.312903
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发表时间：
1994
期刊：
影响因子：
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通讯作者：
E. Rignot;J. Way;Cynthia L. Williams;L. Viereck
中科院分区：
文献类型：
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作者：
E. Rignot;J. Way;Cynthia L. Williams;L. Viereck
机载合成孔径雷达数据收集的美国宇航局/喷气推进实验室的三频，极化，雷达系统在冬季，春季和夏季的博南扎溪实验森林，附近的费尔班克斯，AK，进行了比较，估计全树地上干生物量从21个森林的立场和两个皆伐。虽然C波段雷达后向散射对生物量的敏感性很小，但当生物量从5吨/公顷增加到200吨/公顷时，L和P波段雷达后向散射增加6分贝以上。使用二阶多项式回归，从L-和P-波段雷达预测生物量值，并与实际生物量值进行比较。在P波段HV极化时，预测生物量的误差约为实际生物量的30%。当HV-、HH-和VV-极化在回归中一起使用时，预测生物量的误差约为20%。使用L波段数据获得的误差要大一些。造成这些误差的原因是实际林分生物量估计的不确定性、林分内生物量的显著空间变化、林分受自然干扰后的不寻常状况、沿着雷达信号与林冠复杂三维结构的相互作用。多个入射角数据揭示了雷达照射的入射角/spl θ//sub i/也是影响生物量恢复的因素，即使在HV偏振下，当/spl θ//sub i/>50/spl deg/或/spl θ//sub i/ >
Airborne SAR data gathered by the NASA/JPL three-frequency, polarimetric, radar system in winter, spring, and summer over the Bonanza Creek Experimental Forest, near Fairbanks, AK, are compared to estimates of whole-tree aboveground dry biomass from 21 forest stands and two clear-cuts. While C-band radar backscatter shows little sensitivity to biomass, L- and P-band radar backscatter increase by more than 6 dB when biomass increases from 5 to 200 tons/ha. Using second-order polynomial regressions, biomass values are predicted from the radar at L- and P-band and compared to actual biomass values. At P-band HV-polarization, the error in predicted biomass is about 30% of the actual biomass. When HV-, HH-, and VV-polarization are used together in the regression, the error in predicted biomass is about 20%. Errors obtained using L-band data are a few percents larger. These errors are caused by uncertainties in actual stand biomass estimates, significant inner-stand spatial variations in biomass, unusual conditions of forest stands following natural disturbances, along with interactions of the radar signals with a complex three-dimensional structure of the canopy. Multiple incidence angle data reveal that the incidence angle /spl theta//sub i/ of the radar illumination is also a factor influencing the retrieval of biomass, even at HV-polarization, when /spl theta//sub i/>50/spl deg/ or /spl theta//sub i/ >