Contribution of root respiration to total CO2 efflux from the soil of a deciduous forest

The measurement of CO 2 efflux from forest soils has become of great importance in evaluating the role of forests as sequestering agents of atmospheric CO 2 . In this regard, it is important to know the part of total efflux that originates from root respiration. We have tried to evaluate it by measuring efflux in the field with a portable infrared gas analyzer, while at the same time, the 0–10 cm soil layer was sampled and incubated in the laboratory during 30–40 days. Comparison of field and laboratory measurements was made by conversion to a common temperature (10 °C) using the Arrhenius equation for both processes. Results indicated an Arrhenius apparent activation energy of 25 kcal (1 kcal = 4.1855 kJ) in the field and 15 kcal in the laboratory. Comparison of the results was also made possible by modelling the cumulative CO 2 efflux in the laboratory so that we eliminated the initial flush of mineralization, the value of which was temperature dependent. The grand average of CO 2 efflux from the forest soil calculated for the whole year from the temperature of the soil and the Arrhenius equation was 70 Mg•ha −1 •year −1 , of which 90% originated from the roots.