Litter decomposition and fine root turnover play an important role in the direct cycling of metals between plants and soil, and thus in the mobilization process of the metals. Hence, the goal of this project is to quantify the effects of decomposition processes of leaf litter and roots under 6 different tree species on the mobility of Cd and Zn, after 10 years of tree growth on former agricultural, sandy soil. The project focuses on modifications in pH and percent base saturation and the different OC-fractions that will be originated during those decomposition processes.