The Hölstein site is located in in the eastern part of the Swiss Jura mountains (47°26’16.4’’, 7°46’31.1’’; 540 m a.s.l.), in a mixed, temperate forest with an exceptionally high biodiversity and a vigorous tree regeneration. The research plot has a size of 1.6 ha and comprises 540 mature trees. The main tree species are Fagus sylvatica and Picea abies with an admixture of Abies alba, Quercus petraea, Pinus sylvestris, Acer pseudoplatanus, Carpinus betulus, Fraxinus excelsior and Sorbus torminalis. A canopy crane is installed in the center of the research area to access the tree canopies for in situ measurements and for sampling of leaf material. Rainout shelters will be installed in 2019 for conducting a long-term throughfall exclusion experiment.

The site is located next to Wettingen in the canton of Aargau, within a natural, mixed forest stand which mainly consists of 150 year-old beech (Fagus sylvatica) and 120-170 year-old spruce (Picea abies) trees. Among others, the site is equipped with two meteorological measurement stations; one is located within the forest stand, the second is co-located in the nearby open-field, allowing to measure the forest stand effect on micro-climate. The following parameters are being measured since 2013: Soil solution chemistry (lysimeters), TREENET, atmospheric deposition (throughfall and bulk deposition), circular vegetation plots, crown condition assessment, diameter and height measurements, foliar analyses, leaf area index (LAI), litterfall, manual circumference band measurements, Ozone visible injury assessment, permanent vegetation quadrats, phenological observations, sapflow measurements, soil matrix chemistry, tree core sampling, automated point dendrometer measurements, automatic circumference band measurements.

As the largest contiguous pine forest in Switzerland, the Pfyn forest in Canton Valais (46° 18' N, 7° 36' E, 615 m ASL) offers the best conditions for such measurements. In light of this, a WSL research team installed a long-term experiment of 20 years duration in the Pfyn forest. The average temperature here is 9.2°C, the yearly accumulated precipitation is 657 mm (average 1961-1990). The pines in the middle of the forest are about 100 years old and 10.8 m high. The test area has 876 trees covering 1.2 ha divided into 8 plots of 1'000 m2 each (Image 4). Between the months of April and October four of these plots are irrigated by a sprinkler system providing an additional 700 mm of water, annually. In the other four plots, the trees grow under natural, hence relatively dry conditions.

Beech forest in the Central italian Apennines

The Hyytiälä SMEAR II site (Station for Measuring Ecosystem-Atmosphere Relations) is situated in the Hyytiälä Forestry Field Station of the University of Helsinki. The site consists is a managed, 60-yr old Scots pine forest stand. The main idea of SMEAR type infrastructures is continuous, comprehensive measurements of fluxes, storages and concentrations in the land ecosystem–atmosphere continuum. The forest measurements are operated continuously since 1996, and include e.g. leaf, stand and ecosystem scale measurements of greenhouse gases, volatile organic compounds, pollutants (e.g. O3, SO2, NOx) and aerosols, in addition to full suite of meteorological measurements. The biogeochemical cycles and vegetation–soil–atmosphere interactions are studied both experimentally and with long-term observations. The site has full carbon, water and nitrogen budgets made over 10 years, and it is a full ICOS ecosystem and atmospheric station. Ecosystem and atmosphere measurements also exist nearby in two open oligotrophic fen sites and a humic lake with forested catchment. Most of the measured data can be retrieved from: https://smear.avaa.csc.fi/