Dissolved organic matter (DOM) is an essential parameter of quality and aquatic ecosystem functioning. The production of DOM in soils and its fate as it moves through the catchment were studied during experiments conducted at different scales, from the soil microcosm to the catchment, using natural abundance tracing of stable carbon isotopes (13C). At the catchment scale, we highlighted the role of wetlands in the formation of dissolved organic carbon (DOC). During discharge events we nevertheless observed the mobilisation of several sources of DOC to feed rivers. During laboratory experiments, we demonstrated that forest type influences the fate of water extractable organic carbon content in soil. The substitution of native forests by Douglas plantations reduces carbon inputs into the soil and mineralisation rates of soil organic carbon, which also depend on temperature. However, the water extractable organic carbon content of forest soils, which is influenced by the forest type, depends neither on carbon mineralisation rate nor temperature. We have therefore concluded that in the surface horizons of forest soils, the DOC mainly originates, not from the decomposition of soil organic matter but rather, from the vegetation via litter leachate.