The aim of the study was to estimate the soil organic carbon (SOC) storage in the interface between riparian forests and a matrix of rice fields and pastures with organic management. The study took place in Piedras, Tolima, Colombia. Two plots in production (rice and pasture) were selected and SOC was estimated in these areas and in the edge and the interior of adjacent riparian forests at a depth of 0 to 20 cm. Bulk density and SOC concentration were quantified between May and July, 2013. Potential change in SOC storage due to land use change among rice fields, pastures, and riparian forests was estimated. The interfaces rice field-riparian forest and pasture-riparian forest stored an average of 65.6 and 61.3 t C/ha, respectively, with no statistical differences (p>0.05). Statistical differences were not detected (p>0.05) between agricultural matrices (rice fields and pastures) in any of the variables. The sampling position (matrix and the edge and interior of forests) had a significant impact (p<0.05) just in bulk density: 1.7 vs 1.1 vs 1.0 g/cm3 in interior and edge of the riparian forests and the matrix, respectively. SOC was not statistically affected (p>0.05) by the position in the riparian forest-matrix interface. Conversion from riparian forests to rice fields or pastures with organic management is not emitting greenhouse gases, on the contrary, it is increasing SOC in 3.2 t C/ha. 

Keywords: land use changes, greenhouse gases, carbon sinks.