the NDVI- f APAR relationship and affect its linearity with important consequences
to scaling (Jiang et al. 2006b). The f APAR measured in a Kalahari woodland field
campaign also varied distinctly with NDVI during phenologic green-up and drydown periods (Huemmrich et al. 2005). In an attempt to encompass cross-biome
variations, Sims et al. (2006) empirically derived a global-based, linear f APAR –
NDVI relationship as,
f APAR ¼ 1:24 Â NDVI À 0:168
ð1:12Þ
The SAVI and EVI have also been found useful in estimating f APAR in vegetated canopies, with relationships that are largely independent of soil background
and NPV (Gao et al. 2000; Xiao et al. 2004). Lastly, Zhang et al. (2005) combined
MODIS data with a radiative transfer model to separate f APAR into chlorophyll-,
leaf-, and canopy-absorbed components. They showed large differences in the
f APAR absorbed by chlorophyll versus that absorbed by the canopy and noted that
only chlorophyll-absorbed f APAR is used in photosynthesis. They found NDVI to
be correlated with total canopy f APAR , while EVI was better correlated with the
chlorophyll f APAR , presumably more closely related to the green f APAR .
Gitelson et al. (2003) have conducted extensive field measurements relating
canopy chlorophyll content with satellite vegetation indices, including chlorophyll
spectral measures. The MERIS instrument onboard ENVISAT has a Total Chlorophyll Index (MTCI) product derived from inverse canopy reflectance modeling,
in which maps of canopy chlorophyll content (CCC) and leaf area index (LAI) are
derived simultaneously. The MTCI product is output at 300 m spatial resolution
and validated with indirect field measurements (Vuolo et al. 2012).
VIs have also been successfully related with the fraction of vegetation cover in
Landsat data, but with strong relationship dependencies associated with extent of
tree clumping, LAI, and tree species (Smith et al. 2009; Carlson and Ripley 1997).
There also remains a phenologic dependence similar to that with f APAR .
Fig. 1.11 Local-based
biophysical relationships
between in situ LAI with
NOAA-AVHRR NDVI in the
Hesse Beech Forest
highlighting strong
phenological dependencies
with unique green-up and
dry-down relationships.
Adapted from Wang et al.
(2005), Copyright (2005),
reprinted with permission
from Elsevier
1 Indices of Vegetation Activity
19
to scaling (Jiang et al. 2006b). The f APAR measured in a Kalahari woodland field
campaign also varied distinctly with NDVI during phenologic green-up and drydown periods (Huemmrich et al. 2005). In an attempt to encompass cross-biome
variations, Sims et al. (2006) empirically derived a global-based, linear f APAR –
NDVI relationship as,
f APAR ¼ 1:24 Â NDVI À 0:168
ð1:12Þ
The SAVI and EVI have also been found useful in estimating f APAR in vegetated canopies, with relationships that are largely independent of soil background
and NPV (Gao et al. 2000; Xiao et al. 2004). Lastly, Zhang et al. (2005) combined
MODIS data with a radiative transfer model to separate f APAR into chlorophyll-,
leaf-, and canopy-absorbed components. They showed large differences in the
f APAR absorbed by chlorophyll versus that absorbed by the canopy and noted that
only chlorophyll-absorbed f APAR is used in photosynthesis. They found NDVI to
be correlated with total canopy f APAR , while EVI was better correlated with the
chlorophyll f APAR , presumably more closely related to the green f APAR .
Gitelson et al. (2003) have conducted extensive field measurements relating
canopy chlorophyll content with satellite vegetation indices, including chlorophyll
spectral measures. The MERIS instrument onboard ENVISAT has a Total Chlorophyll Index (MTCI) product derived from inverse canopy reflectance modeling,
in which maps of canopy chlorophyll content (CCC) and leaf area index (LAI) are
derived simultaneously. The MTCI product is output at 300 m spatial resolution
and validated with indirect field measurements (Vuolo et al. 2012).
VIs have also been successfully related with the fraction of vegetation cover in
Landsat data, but with strong relationship dependencies associated with extent of
tree clumping, LAI, and tree species (Smith et al. 2009; Carlson and Ripley 1997).
There also remains a phenologic dependence similar to that with f APAR .
Fig. 1.11 Local-based
biophysical relationships
between in situ LAI with
NOAA-AVHRR NDVI in the
Hesse Beech Forest
highlighting strong
phenological dependencies
with unique green-up and
dry-down relationships.
Adapted from Wang et al.
(2005), Copyright (2005),
reprinted with permission
from Elsevier
1 Indices of Vegetation Activity
19