The interactive effects of climate change and atmospheric CO 2 rise could have potential effects on both soil organic carbon (SOC) storage and the capability of certain management practices to sequester atmospheric carbon (C) in soils. In this study, we present the first regional estimation of SOC stock changes under climate change in Spanish agroecosystems. The Century model was applied over a 80-yr period (i.e., from 2007 to 2087) to an agricultural area of 40,498 km 2 located in northeast Spain under five different climate scenarios. The model predicted an increase in SOC storage in the 0-30 cm soil depth in all the climate change scenarios tested (i.e., ECHAM4-A2, ECHAM4-B2, CGCM2-A2 and CGCM2-B2). Among climate change scenarios, SOC stock changes ranged from 0.15 to 0.32 Tg C yr -1. The Century model also predicted differences in SOC sequestration among agricultural classes. At the end of the simulation period, the greatest SOC stocks were found in the rainfed arable land under monoculture and no-tillage (MC-NT) class and in the grape-olive (GO) class with average stocks greater than 80 Mg C ha -1. On the contrary, both the alfalfa (AF) and the cereal-fallow (CF) classes showed the lowest SOC stocks with predicted values lower than 60 Mg C ha -1. Under climate change conditions, Spanish agricultural soils could act as potential atmospheric C sinks. Nevertheless, both the magnitude of the change in climate and the adoption of beneficial management practices could be critical in maximizing SOC sequestration.
