In the last two decades the use of stable isotope analysis has increased greatly in ecology and environmental and land use sciences. This stems from the fact that the natural stable isotope composition of organisms and ecosystems hold many clues about their functioning and physical environment, including the relative availability of resources. The distribution of the isotopes is not homogeneous in the environment, but follows characteristic spatial and temporal patterns. These patterns * originate from the different behaviour of isotopes in physical and chemical processes, and are * controlled by environmental conditions (including anthropogenic factors) and biological properties of organisms and ecosystems. Thus, stable isotope analysis is providing insight into the functioning of ecosystems and organisms, including forage crops. This includes aspects such as the * water use efficiency of crops and grassland * the role of biological nitrogen fixation in nitrogen nutrition of crop and rangeland plants, * the carbon sink/source activity of ecosystems and the terrestrial biosphere, * C3:C4 vegetation dynamics in grasslands/rangelands, * the nutritional behaviour of wild and domestic animals, * biogeochemical cycling of nitrogen,carbon and water, and * the (agro-)ecology of production systems. These insights have many important applications. For instance, they can be used * to breed crops for greater water use efficiency, * to quantify non-productive water losses in cropping systems, * to assess nitrogen losses from production systems, * to trace animal migration patterns, * to reconstruct ecosystems from archaeological remains and historic relicts and artefacts, * to determine the origin of food stuffs and other organic materials, and * to unravel responses of ecosystems to climate and land use change. Many of these applications have great potential for solving scientific and practical issues of land use, environment, food authentification and forensics. The aim of this spring school is * to give a broad introduction to stable isotope uses in ecology, and land use and environmental research, and so * to generate an awareness of the potential of these methods to young scientists and * to provide a stimulus for stable isotope research and applications to agricultural and environmental problems.