Carbon dioxide exchange above a 30-year-old Scots pine plantation established on organic-soil cropland

In the boreal zone, large areas of natural mires have been drained and used for agriculture, resulting in net carbon dioxide (CO 2 ) emissions and increased nitrous oxide emissions but decreased methane emissions. However, due to structural changes in agriculture, a substantial area of cropland on organic soil has been afforested. In order to estimate the carbon balance of afforested organic-soil cropland, we measured CO 2 and water vapour (H 2 O) fluxes during year above a Scots pine plantation (Pinus sylvestris) in the middle-boreal zone, using the micrometeorological eddy covariance method. We observed CO 2 uptake by the Scots pine stand from late April to mid-October with a daily average net uptake from May to the beginning of October. However, there were also periods of daily net efflux. High ecosystem respiration rates continued throughout the winter (mean winter respiration 0.036 mg CO 2 m -2 s -1 ). As an annual average, the 30-year-old pine stand was a small source of CO 2 (+50 g m -2 a -1 ) to the atmosphere, showing that the CO 2 sequestration into the ecosystem was able to compensate for most of the carbon that was released by heterotrophic respiration from the drained soil.