The ICOS Ecosystem Station Loobos: a pine forest site exposed to atmospheric pollution

Abstract. The Loobos Ecosystem Station (ICOS: NL-Loo) is in a pine forest on sandy soil, the most dominant forest type in the Netherlands. The station was first built in 1995 and the first atmospheric flux measurements were taken in 1997. The station was one of the first in EuroFlux and FLUXNET. Between 2021 and 2023, the station was rebuilt to meet the ICOS standards as an Ecosystem Class 2 station. The initial purpose of the station was to measure fluxes of heat, water and carbon dioxide. Over time, interest has increased in better understanding the forest water use and ecosystem dynamics and its interaction with air quality. This has resulted in additional concentration and flux measurements of ozone and volatile organic compounds. In the near future, we intend to include measurements of nitrogen species (ammonia and nitrogen oxides) to exploit Loobos’ unique location downwind of major anthropogenic emission hotspots. Documenting the instrumentation and exploring the quality of the data is important to understand the observational data. This paper therefore describes the station in terms of geography, ecosystem and instrumentation.