Objectives
Make multi-year in situ measurements
of carbon-related ecosystem properties at BigFoot sites. Our sampling
design will enable scales of fine-grained spatial pattern in these properties
to be explicitly examined, and provide for a field-based ecological
characterization of the flux tower footprint. Multi-year measurements
will ensure that the temporal validity of MODLand products can be accurately
assessed.
Develop multi-year site-specific land
cover, LAI, and fAPAR surfaces by
linking in situ measurements and observations to Landsat ETM+
data. Errors in these surfaces will be quantified and the surfaces summarized
to provide a map-based characterization of the greater flux towers footprint.
Model NPP over the 5 x 5 km BigFoot
footprint at each site in multiple years using land cover and LAI surfaces
derived from Obj. 2 and derived climate surfaces. Two independent ecosystem
process models will be used and their performance assessed by comparisons
of modeled NPP against in situ measurements of NPP from Obj 1.
Modeled GPP and water vapor will compared to tower-based calculations
of these variables.
Validate MODLand land cover, LAI, fAPAR,
and NPP surfaces and examine the contribution of several scaling factors
to differences between MODLand and BigFoot surfaces. Validation will
involve direct comparisons of MODLand surfaces to BigFoot field data
and derived surfaces. Scaling factors examined will include land cover
class, grain size, and generalization of light use efficiency factors
(
) to coincide
with the generalized land cover labels. Effects of these scaling factors
on LUE and model-based NPP estimates will be determned by developing
new NPP surfaces, using as inputs, the scaling factors at each degree
and type of generalization. We will also determine the temporal sensitivity
of the MODLand NPP product using multi-year field measurements, tower
measurements, and BigFoot NPP surfaces.
Faciltate achievement of the GTOS goal
to develop a network of sites that will serve as long-term global NPP
monitoring sites. We want BigFoot activities to both serve as a nucleus
for this network and to help define a practical scaling logic relevant
to these sites that incorporates field measurements, remote sensing,
and ecological modeling.
