Introduction: Our goal is to provide maps of woody plant crown cover and canopy height in the arid southwest US using moderate resolution NASA Earth Observing System data with a multi-angle approach. These are important parameters in western forests that are increasingly vulnerable to fire and also in grasslands that have experienced increases in woody plant abundance since the late C19th, resulting in changes in C pools and cycling. We show how data from the NASA Multiangle Imaging SpectroRadiometer (MISR) can be used to map woody plant canopies. Method: MISR Level 1B2 Terrain Data from June 2002 over SE Arizona and S New Mexico were atmospherically corrected and mapped to 250 m grids. The background (soil+understory) angular response in the MISR viewing plane was estimated a priori, using the isotropic, geometric, and volume scattering weights of a LiSparse-RossThin kernel-driven model (adjusted against the MISR red band data in nine views) plus nadir camera reflectance factors. Calibration of these relationships was effected using shrub cover estimates obtained from IKONOS 1 m panchromatic imagery in a grass-shrub transition zone in the USDA, ARS Jornada Experimental Range. A simple geometric-optical (GO) model was then adjusted against the MISR red band data in all 9 views (providing view zenith angles of up to 70.5°) to retrieve crown cover (by adjusting only mean crown radius; Fig. 1) or mean crown radius and mean canopy height (using the Praxis algorithm).

NASA Carbon Cycle and Ecosystems Workshop, Adelphi, MD, August 21-25, 2006. Acknowledgments: This work was supported by NASA grant NNG04GK91G under the EOS/LCLUC program (program manager: Dr. Garik Gutman). Oblique aerial photo: Scott Bauer, USDA, ARS Photo Unit. Data credits: NASA/JPL/LARC; USDA, ARS, Jornada Experimental Range; The Global Land Cover Facility (http://www.landcover.org). Further results are at http://csam.montclair.edu/~chopping/wood/

Results: Woody plant cover shows a good if biased relationship to cover from QuickBird-derived shrub maps (Fig. 2) and MODIS Vegetation Continuous Fields % Tree Cover (Fig. 3); cover and height show a match with Forest Inventory Analysis Maps (Figs. 4 and 5). Regional-scale maps give very reasonable distributions (Figs. 6, 7, and 8). Inversions took ~1 hour.

A Multi-Angle Approach to Mapping Forest and Shrub Canopy Structure in the Southwestern US Mark Chopping1, Lihong Su1, Andrea Laliberte2, Albert Rango2, Gretchen Moisen3, and John V. Martonchik4

1. Earth & Environmental Studies, Montclair State University, Montclair, NJ 2. USDA, ARS Jornada Experimental Range, New Mexico State University, Las Cruces, NM3. USDA, US Forest Service Rocky Mountain Research Station, Ogden, UT 4. NASA/JPL, Pasadena, CA

Figure 1. L-R: ground and air photogrpahs showing typical backgrounds; flowchart showing the method used to enable GO model inversions.

invert theLiSparse-RossThin

kernel-driven model againstMISR data

obtain relationships between thekernel weights and the backgroundBRDF in the MISR plane by fixing

shrub statistics and adjusting theWalthall model parameters

invert the SGM modelusing the estimated

background and fixingall parameters except

mean shrub radius;adjust the model

against MISR data

obtain estimates of woody shrubmean radiius and number density

via thresholding 1 m IKONOSpanchromatic imagery

calculate fractionalshrub cover from mean

shrub density

MISRRed Band

BRFsin Nine Cameras

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+shrub-volume scattering

+u.story+volume scattering

Fig. 4 MISR/GO Woody Plant Canopy Cover

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AZ NM

TX

Mexico

MISR/GO Forest Inventory Analysis

white=cloud cover and

White Sands National

Monument

Fig. 5 MISR/GO Woody Plant Canopy Height

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MISR/GO Forest Inventory Analysis

AZ NM

TX

Mexico

Figure 3. Comparisons of Retrievals with MODIS VCF % Tree Cover Map

Left: MISR/GO Woody Plant Cover Right: MODIS Vegetation Continuous Fields % Tree Cover for the USDA, ARS Jornada Experimental Range near Las Cruces, NM

Summerford San Andres Mountain Mountains

10 km

Rio Grande riparian zone

0.30

0.89

0.00

0.29

FractionalCover

FractionalCover

tree

shru

b

0.27

0.02

0.0

1

--10 km-- 10 km

Top: MISR/GO Woody Plant Cover Bottom: MODIS Vegetation Continuous Fields % Tree Cover for the Sevilleta National Wildlife Refuge near Socorro, NM

San AndresMountains

Rio Grande riparian zone

0.30

0.89

0.00

0.29

0.0

1

0.27

0.02

Fra

ctio

nal C

over

tree

shru

b

(a) (b) (c)

0.03 0.30 0.01 0.18 shrub non-shrub500 m

y = 0.4358x + 0.0208

R2 = 0.4676

0.00

0.10

0.20

0.30

0.00 0.10 0.20 0.30

Fractional Shrub Cover (QB-NIH)

Fractional Shrub Cover (MISR/SGM)

(d)

Figure 2. (a) QuickBird shrub map in the Jornada Experimental Range (b) aggregated to 250 m (c) retrieved using MISR and the SGM GO model (d) retrieved vs measured cover

Regional Crown Cover and Canopy Height from MISR

Figure 7. Retrieved mean canopy height for SE Arizona and S New Mexico

Black: close to zeroVIBGYOR: 0.06 - 15.10

MISR/GO Regional Woody Plant Canopy Cover

MISR/GO Regional Woody Plant Canopy Height

MISR/GO Regional Crown Cover x Canopy Height Figure 8. Dot product of crown cover and mean canopy height (a surrogate of aboveground woody biomass).

Grayscale: 0.00 - 2.00VIBGYOR: 2.00 - 11.00

Conclusions: Multi-angle data are sensitive to canopy structure and can be exploited to provide maps of woody plant cover and canopy height over large areas. Further work is required to validate these retrievals.

Figure 6. Retrieved woody plant crown cover for SE Arizona and S New Mexico

Black: cover < 0.05 Grayscale: 0.05 - 0.30 (shrubs)VIBGYOR: 0.30 - 0.99 (trees)

White: cloud cover and White Sands National Monument (gypsum dunes and alkali flats)

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