The Varrio Subarctic Research Station and the Station for Measuring Ecosystem-Atmosphere Relationship (SMEAR I, established in 1991) of the University of Helsinki (UH) are located in V?rri? strict nature reserve, Salla, Finnish Laplandon. The flux tower is located at SMEAR I station at the arctic-alpine timberline on the top plateau of the hill of Kotovaara, at 395 m a.s.l, and surrounded by a homogeneous and relative open 10m tall Scots Pine (Pinus sylvestris L.). The trees in the stand are mostly 65-70 years old (in 2017) with a few older trees (up to 150 years). No other disturbances than forest fires, the last one in about 1950.