Nutrient supply as driver of biomass production and associated water flows along a land use and climate gradient. Our goal is to determine the effects of climate and land use changes in the Andes of Ecuador on important processes of nutrient supply (mineralization of organic matter and weathering of rock and soil) using environmental gradients (from about 1000 to 3000 m a.s.l.) as a proxy for climate change and to quantify the effects of land use changes (from natural forest to pastures and to pine forests) through space-time substitution. In addition, we want to test a method for the determination of N mineralization using short-term incubations and a new method for the determination of nutrient supply by weathering, both based on the vertical distribution of stable isotope ratios of C and Ca in soils.