Links
- BigFoot
- MODIS, NASA
- Earth Observatory

Investigators
University of Wisconsin, Madison, WI
S.T. Gower (PI)

Summary
The objective of BigFoot is provide ground validation of MODLand (MODIS Land Science Team) land cover, leaf area index (LAI), fAPAR, and net primary production (NPP) products. The name BigFoot was selected to describe the multiple scales, or footprints, of ground validation that the project will undertake. The current BigFoot study plan covers measurement, mapping, and modeling activities at 4 sites, each equipped with a meteorological flux tower which makes continuous measurements of energy, water, and carbon fluxes for a roughly a 1 km² footprint. Ground validation measurements will be conducted both within the 1 km² eddy flux tower footprint and in an outlying area covering 25 km².

A total of four sites were selected for the BigFoot study: a boreal forest (NOBS), a temperate hardwood forest (HARV), an agriculture cropland (AGRO), and tallgrass prairie grassland (KONZ). The boreal evergreen conifer forest site is the BOREAS NSA old black spruce site near Thompson, Manitoba Canada. The temperate crop site has alternate crops of corn and soybean; it is located near Champaign-Urbana, Illinois. The site is also used for GEWEX validation. The tallgrass prairie site is located at Konza Prairie near Manhattan, Kansas. The site is part of the U.S. Long-Term Ecological Research (LTER) network. The temperate hardwood forest site is located at the Harvard Forest, near Petersham, MA and is also part of the U.S. LTER network. LTER site.

The core BigFoot products will be 25 km² surfaces at 25 m spatial resolution for land cover, LAI, fAPAR, and NPP. Land cover and LAI will be based on Landsat ETM+ imagery, and NPP will be based on spatially distributed, process-based biogeochemistry models. The models will be initialized with the land cover and LAI surfaces and driven by time-series meteorological data. Validation of BigFoot land cover and LAI surfaces will be based on ground sampling of land cover and LAI which is not used in development of the original surfaces. Validation of BigFoot carbon and water flux estimates will be made over the flux tower footprints at a daily time step, based on flux tower measurements, and for the 5 km² study area (i.e., henceforth referred to as the MODLand footprint) based on a sample of new aboveground NPP (NPPA) measurements. Belowground NPP (NPPB) will be measured mostly in the immediate vicinity of the flux towers.

For comparisons to MODLand NPP products, the BigFoot 25 m² grid at each site will be overlain with the 1 km2 MODLand grid that is spatially consistent with the MODIS imagery. NPP models will be run for calendar years 1999 and 2000 for the boreal forest (NOBS) and agroecosystem (AGRO) study area, and compared to MODLand NPP products produced at eight-day and annual time steps. Similar analyses will be conducted for the tallgrass prairie (KONZ) and temperate forest (HARV) study area in 200 and 2001. Differences between BigFoot and MODLand NPP products will be evaluated in terms of the differences in spatial resolution of the analysis, the differences in vegetation classification system, and the differences in epsilon, the light use efficiency factor, as used in the MODLand NPP algorithm and as derived from BigFoot NPP simulations.

Publications
Canadell, J.G., H.A. Mooney, D.D. Baldochi, J.A. Berry, J.R. Ehleringer, C.B. Field, S.T. Gower, D.Y. Hollinger, J.E. Hunt, R.B. Jackson, S.W. Running, G.R. Shaver, W. Steffen, S.E. Trumbore, R. Valentini, and B.Y. Bond. 1999. Carbon metabolism of the terrestrial biosphere: A multi-technique approach for improved understanding. Ecosystems 3:115-130.

Cohen, WB, TK Maiersperger, Z Yang, ST Gower, DP Turner, WD Ritts, M Berterretche and SW Running. 2003. Comparison of land cover and LAI estimates derived from ETM+ and MODIS for four sites in North America: a quality assessment of 2000/2001 provisional MODIS products. Remote Sensing of Environment 88:233-255.

Cohen, WB, TK Maiersperger, ST Gower, DP Turner, 2003. An improved strategy for regression of biophysical variables and Landsat ETM+ data. Remote Sensing of Environment 84:561-571.

Gower, S.T., C.J. Kucharik and J.M. Norman. 1999. Direct and indirect estimation of leaf area index, fapar, and net primary production of terrestrial ecosystems. Remote Sensing of Environment 70:29-51.

Lee KS, WB Cohen, RE Kennedy, TK Maiersberger, and ST Gower. 2004. Hyperspectral versus multispectral data for estimating leaf area index in four different biomes. Remote Sensing of Environment 91(3-4): 508-520.

Lefsky, MA, WB Cohen, DJ Harding, GG Parker, SA Acker, ST Gower. 2002. Lidar remote sensing of aboveground biomass in three biomes. Global Ecology and Biogeography 11:393-399.

Running, S.W., D.D. Baldochii, W. Cohen, S.T. Gower, D. Turner, P. Bakwin, K. Hibbard. 1999. A global terrestrial monitoring network, scaling tower fluxes with ecosystem modeling and EOS satellite data. Remote Sensing of Environment 70:108-127.

Shabanov, NV, D Huang, W Yang, B Tan, Y Knyakikhin, RB Myneni, DE Ahl, ST Gower, AR Huerte, LEOC Aragao, YE Shimabukuro. 2005. Analysis and optimization of the MODIS Leaf Area Index algorithm retrivals over broadleaf forests. IEEE Transactions on Geosciences and Remote Sensing 43:1855-1865.

Turner, DP, WD Ritts, WB Cohen, TK Maeirsperger, ST Gower, AA Kirschbaum, SW Running, MS Zhao, SC Wofsy, AL Dunn, BE Law, JL Campbell, WC Oechel, HJ Kwon, TP Meyers, EE Small, SA Kurc, JA Gamon and H Tian. 2005. Site-level evaluation of satellite-based global terrestrial gross primary production and net primary production monitoring. Global Change Biology 11(4): 666-684.

Turner, D, WD Ritts, WB Cohen, ST Gower, M Zhao, SW Running, SC Wofsy, S Urbanski, AL Dunn, and JW Munger. 2003. Scaling gross primary production (GPP) over boreal and deciduous forest landscapes in support of MODIS GPP product validation. Remote Sensing of Environment 88:256-270.

Turner, D, ST Gower, WB Cohen, M Gregory, and TK Maiersperger. 2002. Effects of spatial variability in light use efficiency on satellite-based NPP monitoring. Remote Sensing Environment 80:397-405.