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.
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Claims 6
Claim · model-written summary
Simulated canopy reflectance at leaf area index 10 did not match infinite-leaf reflectance.
Not reportedValue
Verbatim
e0“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∞.”
Claim · model-written summary
Euclidean distances between canopy and infinite-leaf reflectance were large, particularly under the Stokes equation.
Verbatim
e0“Differences using ED between canopy ρ and R∞ were large, especially using Stokes’ equation.”
t0“leaf reflectance”
e1“plant species”
Claim · model-written summary
SCM, SAM, SID, and SID × sin(SAM) found Stokes-equation R∞ most similar to canopy reflectance.
Verbatim
e0“the SCM, SAM, SID, and SID × sin(SAM) metrics showed R∞ from the Stokes’ equation was the most similar to canopy ρ”
t0“leaf reflectance”
e1“plant species”
Claim · model-written summary
The combined SID × sin(SAM) metric had greatest similarity between infinite-leaf and canopy reflectance.
Verbatim
e0“The combined SID × sin(SAM) metric had the greatest similarity between R∞ and canopy ρ compared to the other spectral information metrics.”
t0“leaf reflectance”
e1“plant species”
Claim · model-written summary
Infinite-leaf reflectance was judged a poor substitute for canopy reflectance.
Not reportedDirection
Verbatim
e0“R∞ was not a good substitute for canopy ρ”
t0“leaf reflectance”
e1“plant species”
Claim · model-written summary
Infinite-leaf reflectance may help assess species differences in leaf chemical composition.
Not reportedComparatorValue
Verbatim
e0“R∞ may be important for assessing differences of leaf chemical composition among species”
t0“leaf reflectance”
e1“plant species”