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

Birch Xeric 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 Pine RAMI Spruce

Kuusk et al., 2009, RSE

a mixture of several grass

speciesvarious 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 hazelnutFieldMODIS 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)