Mapping forest understory in European hemi-boreal stands using MODIS BRDF
productJan Piseka, Miina Rautiainenb, Janne Heiskanenb,
Matti Mõttusb
July 26, 2011, IGARSS 2011 Vancouver
a b
Why?
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the signal from the understory can be used, for example:
(1) in forestry applications to separate forest site types (i.e. soil fertility classes)(2) to remove the influence of understory in estimating canopy biophysical variables (e.g. LAI, fPAR) from remotely sensed images (3) to develop and test canopy radiative transfer models
Rautiainen et al., 2007, RSE
Rn = PTn x RT + PGn x RG + ZTn x RZT + ZGn x RZG
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Is it possible?
Rn = PTn x RT + PGn x RG + ZTn x RZT + ZGn x RZG
Ra = PTa x RT + PGa x RG + ZTa x RZT + ZGa x RZG
RZT = M RT ;RZG = M RG 4Canisius and Chen, 2007, RSE; Pisek et al., 2010, IEEE-TGRS
How?
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Rn = PTn x RT + PGn x RG + ZTn x RZT + ZGn x RZG
Ra = PTa x RT + PGa x RG + ZTa x RZT + ZGa x RZG
RZT = M RT ;RZG = M RG
(Peltoniemi et al., 2005, RSE)
mixed understory
Bidirectional Reflectance Distribution Function (BRDF)
The MODIS BRDF/Albedo Product (MCD43A1) at 500 m resolution every 8
days
6Photo property of Andres Kuusk
Hyytiälä forest standsHerb-rich
BirchXeric Pine
Mesic Spruce
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herbaceous species and graminoids
lichens and heather
mosses, abundant dwarf shrubs
Upscaling field measurements in Hyytiälä
area
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upscaling with forest site type database (produced by Metsähallitus)
Hyytiälä results
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Field 2010MODIS 2010MODIS 2009
Hyytiälä results – mean absolute errors
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DOY 100-200 (April-mid July) QA=0 QA=1red band 0.007 0.006NIR band 0.019 0.022
DOY 201-300 (mid July-October) QA=0 QA=1
red band 0.009 0.014NIR band 0.045 0.058
DOY 100-300 (April-October)QA=0 QA=1
red band 0.008 0.011NIR band 0.031 0.045
Finland understory NDVI - 2010
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Hyytiälä summary
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We retrieve seasonal dynamics of understory spectra at 500 m resolution with MODIS BRDF product
Results directly validated with in-situ measured seasonal reflectance trajectories of boreal forest understory layers at Hyytiälä, Finland
We illustrate the potential of MODIS multi-angle, multi-spectral observations to map understory properties, which was not possible with mono-angle data
Always check and take into account documented quality and limitations of the satellite-derived product!
Want to know more?
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Pisek, J., Rautiainen, M., Heiskanen, J., Mottus, M. On the retrieval of seasonal dynamics of forest understory reflectance in a Northern European boreal forest from MODIS BRDF data. Remote Sensing of Environment (accepted with revisions).
Rautiainen, M., Mõttus, M., Heiskanen, J., Akujärvi, A., Majasalmi, T. & Stenberg, P. 2011. Seasonal reflectance dynamics of common understory types in a Northern European boreal forest. Remote Sensing of Environment (in press).
RAMI stands (Järvselja, Estonia)
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RAMI Birch RAMI PineRAMI
Spruce
Kuusk et al., 2009, RSE
a mixture of several grass
species
various Sphagnum moss species and
marsh tea
bare soil, mosses
Järvselja results
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FieldMODIS 2007Hazelnut LOPEX
36 (birch+alder)51 (spruce)13 (pine)
97 (pine)3 (birch)
86 (birch, aspen, alder)14 (spruce)
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RAMI birch stand (Järvselja, Estonia)
abundant layer of hazelnut
FieldMODIS 2007Hazelnut LOPEX
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MODIS BRDF parameters (every 8 days at 500m resolution)
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R(θi,θv,Φ,λ) = fiso(λ) + fvol(λ)Kvol(θi,θv,Φ) + fgeo(λ)Kgeo(θi,θv,Φ)
MODIS BRDF parameters fromMCD43A1.005 product
from Lucht et al. (2000, IEEE)