1. Scaling GPP at Flux Tower Sites in the Context of EOS/MODIS Validation
David P. Turner
Oregon State University

2. Validating MODIS Terrestrial Ecology Products with Satellite and In-situ Measurements
Warren Cohen
USDA Forest Service
David Turner
Oregon State University
Tom Gower
University of Wisconsin
Peter Reich
University of Minnesota
Steve Running
University of Montana

3. BigFoot Objectives
Develop and validate data layers (25 km2) for land cover,
leaf area index (LAI), and net primary production (NPP)
at high spatial resolution (25 m) at sites representing
the major biomes
Use these data layers for validation of MODIS land cover,
LAI and NPP products
Study scaling issues related to monitoring of global NPP

5. HARV HARV Leaf-off Leaf-on KONZ April July September
Capturing seasonality
With ETM+ is
important to both land
cover and LAI mapping
HARV
Leaf-off
Leaf-on
KONZ
April
July
September

7. Field-Based Sampling Design
100 25m2 plots
80 in a nested spatial series
20 plots broadly distributed
Plot measurements
Vegetation cover
LAI, fPAR
Aboveground biomass
Aboveground productivity
Belowground productivity

8. GPP =  (NEE – Re) GPP = gross primary production (gC m-2 d-1)
For daylight period
GPP = gross primary production (gC m-2 d-1)
NEE = net ecosystem exchange (half hourly)
Re = ecosystem respiration (half hourly)

9. PAR = from DAO climate model
MODIS GPP Product
GPP (gC m-2 d-1) = PAR * fAPAR * g
Where:
PAR = from DAO climate model
fAPAR = from MODIS reflectances
g ( gC MJ-1) = GPP / APAR
MODIS g from lookup table
Spatial Resolution is 1 km
Temporal Res. is 8-day mean

10. AGRO (29 July 99) LAI 27 July 99 98 % accurate (cross validation)
P vs. O r^2 = 0.72

13. *
* Data courtesy of S. Wofsy and Ameriflux

14. *
* Data courtesy of S. Wofsy and Ameriflux

15. * Data courtesy of D. Bremmer, A. Knapp, J. Ham

16. *
* Data courtesy of T. Meyers and FLUXNET

17. NPP and GPP at the Northern Boreas Site
(units are gC m-2 yr-1)
Old Black Spruce (1994)
ANPP (measured )
BNPP (estimated)
TNPP
GPP (flux tower) ~800
NPP/GPP
TNPP (measured)
Plant Respiration (scaled)
GPP
NPP/GPP

22. NPP and GPP at the Konza Site
(units are gC m-2 yr-1)
tallgrass prairie (1997)
ANPP (measured )
BNPP (estimated)
TNPP
GPP (flux tower)
NPP/GPP
TNPP (simulated)
GPP (simulated)
NPP/GPP (simulated)

24. Konza Prairie false color composite TM imagery*
Konza Prairie false color composite TM imagery
* Images courtesy of Konza LTER web site

25. NPP and GPP at the Bondville Site
(units are gC m-2 yr-1)
corn (1999) soybean (1999)
ANPP (measured )
BNPP (estimated)
TNPP
GPP (flux tower) (1999)
NPP/GPP
TNPP (simulated)
GPP (simulated)
NPP/GPP

28. *
* Derived from tower PAR data courtesy of S. Wofsy and Ameriflux

32. Conclusions
Still lots to be done reconciling tower-based GPP and the sum of measured NPP and scaled plant respiration
At some tower sites, spatial heterogeneity matters in linking tower NEE to field measurements and modeling
A scaling approach using high resolution remote sensing and NPP models permits indirect linkage of flux tower measurements to MODIS GPP products at the 1 km spatial resolution and 8 day temporal resolution