The Flask-Sampler is used for the automated collection of air samples under standardized conditions. The Flask-Sampler consists of five drawers. There are 24 flask ports in the upper four drawers, 6 in each floor. Each port allows the automated valve opening and closing of one inserted flask. The lowest drawer contains the control electronics and all necessary components for the sampling procedure (e.g. pumps, valves, pressure sensors).3 The air will be sampled at the highest sampling height of the continuous gas analysis (100m in this case).1 The flasks containing air samples will be send at the ICOS Central Analytical Laboratories for the analyses which include: CO, CO2, CH4, H2, SF6 mole fractions and the isotopic ratio of 13C and 18O within CO2.