Forest cover has increased in mountainous areas of Europe over the past decades because of the abandonment of agricultural areas (land-use change). For this reason, understanding how land-use change affects carbon (C) source-sink strength is of great importance. However, most studies have assessed mountainous systems C stocks, and less is known about C turnover rates, especially of “fresh” organic material (OM). We studied the decomposition of wood stakes of trembling aspen (Populus tremuloides Michx.) and loblolly pine (Pinus taeda L.) placed on the litter layer and in the mineral soil of five ecosystem types (pastures and forests) - representing the successional development after land abandonment in the eastern Swiss Alps - for 6 years. Wood stake decomposition rates were generally highest in pastures and lowest in early successional forests. Aspen stakes decomposed more rapidly than pine stakes, especially in the mineral soil. Soil temperature (and to a smaller extent soil phosphorus (P) concentration) best explained the differences in decomposition among the ecosystem types. Initial wood decay is temperature-sensitive, and therefore would likely increase under future climate change scenarios.