(1) Measurements on leaf optical properties
Leaf (both coniferous needle leaf and deciduous broad leaf)
reflectance and transmittance are measured from 350 nm to
2500 nm at 1 nm interval using the portable field spectroradiometer
FieldSpec Pro FR (Analytical Spectral Devices, Inc. Boulder,
USA) attached via a fiber optic to the Li-Cor 1800 integrating
sphere (Li-Cor 1800-12S, Li-COR, Inc., Lincoln, Nebraska,
USA).
Fig.1: Leaf reflectance and transmittance
measurements using the ASD equipped with the Li-Cor 1800 integrating
sphere
Fig.2: Measured reflectance
and transmittance spectra of sugar maple leaves
(2) Measurements on leaf biochemical contents
Leaf chlorophyll content can be estimated by measuring the
spectral properties of the solvent using the ASD spectroradiometer
by illuminating the solvent with the LS-1 tungsten halogen
light source connected to a 400-micron Fiber (Ocean Optics,
Inc., Dunedlin, Florida, USA). The absorbance at 664 nm, 647
nm, and 480 nm were calculated to estimate chlorophyll a and
b content using the extinction coefficients derived by Wellburn
(1994). The seasonal and canopy-gradient variations of the
leaf chlorophyll content were measured and used for validating
the leaf optical model.
Fig.3: Seasonal and
canopy gradient variation of leaf chlorophylla+b content
|
