A THEORETICAL-ANALYSIS OF THE EFFECT OF FOREST STRUCTURE ON SYNTHETIC-APERTURE RADAR BACKSCATTER AND THE REMOTE-SENSING OF BIOMASS
A THEORETICAL-ANALYSIS OF THE EFFECT OF FOREST STRUCTURE ON SYNTHETIC-APERTURE RADAR BACKSCATTER AND THE REMOTE-SENSING OF BIOMASS
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DOI：
10.1109/36.377934
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发表时间：
1995-03-01
影响因子：
8.2
通讯作者：
IMHOFF, ML
中科院分区：
文献类型：
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作者：
IMHOFF, ML
林分水平的森林冠层结构，测量的大小，密度和分布的茎，枝，叶可能有很大的影响SAR后向散射。本研究使用密歇根州微波冠层散射模型（MIMICS）和森林冠层的生物特征数据，从热带和亚热带阔叶林模拟一系列的林分具有相当的地上生物量，同时仍表现出显着的结构差异。这些模型林分代表了地球阔叶林中广泛的基本结构差异。NASA/JPL AIRSAR P-、L-和C-波段四极天线配置在20度、40度和60度入射角下显示了雷达对这些结构差异的响应。五种结构类型，地上生物量总量为5 kg/m3（2）（50吨/公顷），15 kg/m2（150吨/公顷）的三种结构类型，30 kg/m2（300吨/公顷）的三种结构类型。使用简化的模型输入来减少在结构类型范围内测试的几何变量的数量。评估极端结构差异可能对生物量信号和饱和阈值的潜在影响。结果表明，结构可以有相当大的影响，对SAR返回森林与地面生物量相当，后向散射的差异高达18分贝的预测为某些波段和极化。一个森林冠层结构的描述符来自植被表面积体积比（SA/V），这是一个结构的巩固措施，似乎解释后向散射的差异。在许多植被中，结构巩固与森林演替的“疏伐阶段”生物量的增加直接相关。这种结构效应可以解释在这些情况下SAR后向散射和生物量之间的良好关系。
Stand level forest canopy structure as measured by the size, density, and distribution of the stems, branches, and leaves may have a strong effect on SAR backscatter. This study used the Michigan Microwave Canopy Scattering model (MIMICS) and forest canopy biometric data from tropical and subtropical broadleaf forests to simulate a series of forest stands having equivalent above ground biomass while still exhibiting substantial structural differences. The model stands were made to represent a wide range of basic structural differences found in Earth's broadleaf forests. The radar response to these structural differences is shown for the NASA/JPL AIRSAR P-, L-, and C-band quadpol, configuration at incidence angles of 20 degrees, 40 degrees, and 60 degrees, Results for three sets of equal-biomass-forest-stands were generated: five structural types having a total above ground biomass of 5 kg/m(2) (50 ton/ha), three structural types at 15 kg/m(2) (150 tons/ha), and three structural types at 30 kg/m(2) (300 tons/ha). Simplified model input were used to reduce the number of geometric variables tested across the range of structural types, The potential effect that extreme structural differences might have on the biomass signal and saturation threshold was assessed. Results indicate that structure can have a considerable effect on the SAR return for forests with equivalent above ground biomass, Differences in backscatter of up to 18 dB were predicted for some bands and polarizations. A forest canopy structural descriptor derived from the vegetation surface area to volume ratio (SA/V), which is a measure of stuctural consolidation, appears to explain the differences in backscatter. In many vegetation stands structural consolidation is directly related to an increase in biomass during the ''thinning phase'' of forest succession. This structural effect may explain the good relationship between SAR backscatter and biomass in these cases.