North American Net Ecosystem Exchange: Regionalization of AmeriFlux Observations

Observations of net ecosystem exchange (NEE, g C m-2y-1) from the AmeriFlux network of eddy-covariance systems provides a basis for estimating NEE of North America, with implications for assessing the magnitude and nature of a North American carbon sink. The challenge lies in the application of appropriate techniques for scaling-up point estimates of NEE from AmeriFlux sites to regional estimates. This use of the AmeriFlux data complements the use of the AmeriFlux data to understand NEE processes. Th investigators have explored a sequence of increasingly refined, and more difficult, methods for regionalization of NEE from AmeriFlux site data. These methods range from simple methods based on defining the geographical areas that sites represent and multiplying site estimates by those areas, to more refined methods involving the application of geographically distributed, process-based terrestrial ecosystem models. This data set presents a first approximations of NEE for the forested region of the eastern United Sates using the simplest of these methods, extrapolating mean values over appropriate areas. The refinements needed to improve these estimates and point towards the next steps of more sophisticated methods of regionalization are discussed.