We estimated component and whole-ecosystem CO 2 efflux (R ECO) in a Pinus canariensis Chr. Sm. ex DC stand in Tenerife, Canary Islands, an ecotone with strong seasonal changes in soil water availability. From November 2006 to February 2008, we measured foliage, stem and soil CO 2 efflux by chamber techniques. Sitespecific CO 2 efflux models obtained from these chamber measurements were then combined with half-hourly measurements of canopy, stem and soil temperature as well as soil water potential, leaf and stem surface area data for scaling up component-specific CO 2 efflux to R ECO. Integrated over an entire year, R ECO was 938 g of C m À2 in 2007 and comprised the following component fluxes: 77% from soil, 11% from stems and 12% from foliage. Whole-ecosystem CO 2 efflux varied markedly throughout the year. During the cold and wet season, R ECO generally followed the seasonal trends in temperature, and during the warm and dry summer, however, R ECO was significantly reduced because of limited soil water availability in the main rooting horizon.