Carbon balance assessment of a Belgian winter wheat crop (Triticum aestivum L.)

The carbon balance of a winter wheat crop in Lonzee, Belgium, was assessed from measurements carried out at different spatial and temporal scales between November 2004 and August 2005. From eddy covariance measurements, the net ecosystem exchange was found to be -0.63 kg C m(-2) and resulted from the difference between gross primary productivity (GPP) (-1.58 kg C m(-2)) and total ecosystem respiration (TER) (0.95 kg C m(-2)). The impact of the u(*) threshold value on these fluxes was assessed and found to be very small. GPP assessment was partially validated by comparison with an estimation scaled up from leaf scale assimilation measurements. Soil respiration (SR), extrapolated from chamber measurements, was 0.52 kg C m(-2). Net primary productivity, assessed from crop sampling, was -0.83 kg C m(-2). By combining these fluxes, the autotrophic and heterotrophic components of respiration were deduced. Autotrophic respiration dominated both TER and SR. The evolution of these fluxes was analysed in relation to wheat development.