Analysis of carbon and water fluxes from the NOPEX boreal forest: comment

In a recently published paper on simulation and analyses of water and carbon fluxes at the NOPEX central site, a modeling exercise indicated a rather strong sink of carbon for the studied forest stand and year (1994). At the 100-m high tower, the eddy-flux measurements stretch out to the present day. They show that the surrounding forest area is a rather weak source of carbon. This note clarifies the previously published numbers in view of several new findings at the site since the paper preparation (1995) up to the publishing/present date (1998/1999). The key issues that could not be adopted three years ago, were (i) footprint analyses of the eddy-covariance measurements, (ii) correction of eddy-flux data for night-time, and (iii) information on carbon flux from soil. These complementary findings address the previous uncertainties in carbon budget assessment and model parameterization and suggest improvements to model application and better match the measured data. (C) 1999 Elsevier Science B.V. All rights reserved.