Objectives

1Make 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.

2Develop 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.

3Model 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.

4Validate 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 (Varepsilon) 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.

5Faciltate 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.

 
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