We calculated stem CO2 efflux (ES) of Pinus canariensis at a timberline site in Tenerife, Canary Islands, from March 7, 2008 and February 9, 2009. ES varied markedly throughout the year. Although ES generally followed the seasonal trends in temperature, we observed seasonal adjustment of ES in both ES normalized to temperature (ES10) and the temperature sensitivity (Q10) resulting in lower ES10 values during the warm and dry season as compared during the cold and wet season; the latter corresponding with the period of stem growth. The Q10 by contrast, was higher during the warm and dry summer than during the cold and wet season, an observation suggesting that climate extremes such as summer drought in the Mediterranean may override the observation that Q10 declines with increasing temperature. As concurrent measurements estimating the potential impact of sap flow on ES revealed no interaction in P. canariensis, the Q10 values were used along with ES10 and stem temperature records to predict annual total ES and for partitioning total ES into its maintenance (Em) and a growth (Eg) component.