ABSTRACT

An important application of hyperspectral remote sensing is monitoring the diversity of plant species and functional types, which correlate with differences of leaf chemical constituents. Diffuse reflectance of an infinitely thick leaf ( R _∞) is directly related to chemical absorbance and may be calculated from leaf spectral reflectance and transmittance based on Kubelka-Munk theory or other radiative transfer models. The PROSPECT-D leaf optics model was used to create leaf optical properties of nine pseudo-species, and R _∞ were calculated using Stokes’, Lillesaeter’s, Goudriaan’s, and Hapke’s equations. Conceptually, R _∞ is assumed to equal canopy reflectance (canopy ρ ) at maximum leaf area index. For each pseudo-species, canopy ρ at a leaf area index of 10 was obtained using the PROSAIL model, but the simulated canopy ρ did not match R _∞. Similarity between R _∞ and canopy ρ for each pseudo-species was calculated using five spectral information metrics: Euclidean distance (ED), an adjusted spectral correlation measure (SCM), spectral angle mapper (SAM), spectral information divergence (SID), and the product of SID × sin(SAM). Differences using ED between canopy ρ and R _∞ were large, especially using Stokes’ equation. However, the SCM, SAM, SID, and SID × sin(SAM) metrics showed R _∞ from the Stokes’ equation was the most similar to canopy ρ , because these metrics are insensitive to differences in magnitude. The combined SID × sin(SAM) metric had the greatest similarity between R _∞ and canopy ρ compared to the other spectral information metrics. While R _∞ was not a good substitute for canopy ρ, R _∞ may be important for assessing differences of leaf chemical composition among species, thereby avoiding effects of taxon-independent factors on canopy ρ .

摘要

高光谱遥感的重要应用是监测植物种类和功能类型的多样性，这些多样性与叶片化学成分的差异相关。无限厚叶（漫反射率- [R _∞）直接相关的化学吸收，并且可以由基于库贝卡-芒克理论或其他辐射转移模型叶片光谱反射率和透射来计算。前景-d叶光学模型用于创建九个伪物种叶子的光学性质，和- [R _∞使用斯托克斯，Lillesaeter的，Goudriaan的，和Hapke方程计算。从概念上讲，- [R _∞被假定为等于冠层反射（篷ρ ）处于最大叶面积指数。对于每个伪物种，树冠ρ使用PROSAIL模型得到以10叶面积指数，但模拟篷ρ没有匹配- [R _∞。之间的相似性[R _∞和树冠ρ为每个伪物种使用五个频谱信息指标计算：欧几里得距离（ED），经调整的频谱相关性度量（SCM），光谱角映射器（SAM），光谱信息散度（SID），和SID×sin（SAM）的乘积。使用冠层之间ED差异ρ和- [R _∞很大，尤其是在使用斯托克斯方程。但是，SCM，SAM，SID和SID×sin（SAM）指标显示 [R _∞从斯托克斯方程为最相似的篷ρ，因为这些指标是不敏感的在幅度上的差异。将合并的SID×SIN（SAM）度量之间有最大相似- [R _∞和篷ρ相对于其他光谱信息指标。而[R _∞不是为冠层的良好替代ρ，R _∞可以是用于评估物种间叶化学成分的差异，从而避免了对篷分类单元无关的因素的影响重要ρ。