Wang, W., K.J. Davis, D.M. Ricciuto, M.P. Butler, and B.D. Cook, 2004. Decomposing NEE measured over a mixed forest area and upscaling in northern WI using footprint models and a vegetation map, Fall Meeting of the American Geophysical Union, pp. B51A-0933, American Geophysical Union, San Francisco, CA.

The measured net ecosystem-atmosphere exchange of CO2 (NEE) in a mixed forest area in Northern Wisconsin is decomposed into contributions from six vegetation classifications using footprint models and a vegetation map. The large footprint of the WLEF tall tower is used as a regional flux measurement, encompassing several vegetation classifications.The vegetation classifications are mixed coniferous/deciduous, aspen, mixed deciduous, low-canopy wetland, forested wetland, and others. The functional parameters in the ecosystem models of respiration-Temperature and flux-PAR for the six types of ecosystems are inferred and compared. It appears that separate ecosystems respond differently to the same environmental conditions. The aspen and forested wetland ecosystems have the largest values of NEE when saturated with respect to incoming solar radiation in the day. The forested wetland ecosystem has the largest Q10 and diurnally-averaged respiration rate at night. Another interesting finding is that the derived respiration rates for the deciduous and lowland wetland ecosystems in the area around WLEF tower are larger than those measured at two nearby flux tower sites, Willow Creek (deciduous forest) and Lost Creek (low-canopy wetland). These results indicate that the measurements at Willow Creek and Lost Creek are not representative of all deciduous and low-canopy wetland ecosystems in the region possibly because variables such as stand age, density, species composition, or coarse woody debris content can vary among similar land cover classifications. As an application, the NEE models with derived parameters for each ecosystem are aggregated in a bottom-up approach to estimate the flux in a 40km x 40km region, and the results are compared with those from a top-down ABL budget method.