Soil carbon dioxide efflux in pure and mixed stands of oak and beech

Total Soil Respiration (TSR) was measured in pure and mixed stands of oak and beech and was partitioned into two contributions using the forest floor removal technique: Mineral Soil Respiration (MSR) and Forest Floor Respiration (FFR). In addition, laboratory incubations of the forest floor and the Ah horizon were performed to evaluate the heterotrophic respiration and the DOC production of these horizons. The relationships between soil temperature and the various soil respiration contributions in the three stands were compared using Q(10) functions. In situ, significant differences (alpha = 0,05) between stands were observed for the R-10 parameter (respiration rate at 10 degrees C) of the TSR, MSR and FFR contributions, while only the temperature sensitivity (Q(10)) of TSR was significantly affected by stand composition. The effect of soil water content was only significant on MSR and followed different patterns according to stand composition. Under controlled conditions, the R-10 of the forest floor and of the Ah horizon varied with stand composition and the Q(10) of the forest floor decreased in the order: oak (2.27) > mixture (2.01) > beech (1.71).