Soil surface CO ₂efflux measurements in Norway spruce forests: Comparison between four different sites across Europe — from boreal to alpine forest

Extensive measurements of soil surface (including vegetation cover) CO2 efflux were carried out on 80 positions at four different forest sites (Sweden, Germany, Czech Republic and Italy) using a closed dynamic chamber technique. The period of measurement was 4–5 consecutive days per site. Two approaches were used to analyze the measured data, the Q10 parameter and the Arrhenius relationship. Basic environmental factors such as soil temperature and moisture were measured. All the four investigated sites showed a positive dependence of the soil surface CO2 efflux on soil temperature. The four datasets generally resulted in good agreement (up to 93%) between the approaches and residual analysis showed no significant difference between approaches (less than 8%). The Q10 ranged between 2.0 and 2.3 among the sites. The highest spatial variation of the soil surface CO2 efflux at 10 °C (expressed by the coefficient of variation CV) ranged from 30 to 65% between sites.