Drylands cover large areas of the land surface and may continue to expand in the future due to climate change. Even though dryland soils have low organic carbon (OC) concentrations, they store a significant fraction of global soil OC stocks. However, predicting effects of increasing aridity on soil OC stocks is not yet possible because above- and belowground processes of litter decomposition and soil organic matter (SOM) stabilization are differently affected by aridity. Therefore, the project focuses on the differential response of above- and belowground litter decomposition to increasing aridity and to elucidate the consequences for SOM stabilization. We will take advantage of a unique steep gradient in precipitation found on common parent material in Israel. We will study above- and belowground litter decomposition and SOM stabilization by applying ¹³C-labelled litter (shoots and roots) of an annual herbaceous plant in the field along the aridity gradient. The use of stable isotopes allows us to monitor litter decomposition and follow SOM formation under conditions as natural as possible along the gradient. We will measure ¹³CO₂ fluxes in the field and combine these data with the incorporation of the ¹³C tracer into different SOM fractions.