Biometric and eddy covariance-based assessment of decadal carbon sequestration of a temperate Scots pine forest

In recent years, the status of forests as sources or sinks of carbon has received much attention. Nonetheless, evidence-based long-term estimates of the magnitude of the carbon sequestration in forests are still scarce. In this study we present two independent estimates of net carbon sequestration in a temperate Scots pine dominated forest ecosystem over a 9-year period (2002–2010). First, the net ecosystem carbon balance (NECB) was estimated from net ecosystem CO2 exchange as measured by the eddy covariance technique (NECBEC). To this end, the eddy covariance estimates were combined with non-CO2 carbon fluxes such as DOC leaching and VOC emissions. The second approach to determine the carbon sequestration was based on the changes in the ecosystem carbon stocks over time (NECBSC). For this NECBSC estimate, two assessments of the ecosystem carbon stocks (2002 and 2010) were compared. Results showed that the eddy covariance approach estimated a net uptake of 2.4 ± 1.25 tC ha−1 yr−1, while the stock based approach suggested a carbon sink of 1.8 ± 1.20 tC ha−1 yr−1. No significant change was observed in the mineral soil carbon, while the carbon stock of the litter layer slightly decreased. Phytomass was thus the main carbon sink (2.1 tC ha−1 yr−1) in the pine forest, predominantly in the stems (1.3 tC ha−1 yr−1). The fact that stem wood is the main carbon sink within the ecosystem implies that the future harvesting has the potential to fully offset the CO2 uptake by this Scots pine forest.