1 Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), CH-8903 Birmensdorf, Switzerland
In a mature mixed forest (NW Switzerland), the nutrients in the soil solution were monitored over the first year of canopy enrichment with CO2 (+ 140 µmol.mol-1). For this purpose, ceramic suction cups and resin bags were installed along three transects through the experimental area under control and CO2-treated trees: one transect under beech (Fagus sylvatica), one under oak (Quercus petraea, Q. robur and one under hornbeam (Carpinus betulus). There was an indication of enhanced nitrate availability under beech and oak trees exposed to elevated CO2, but not under hornbeam trees. There was no delta13C-signal in the dissolved organic carbon (DOC) of the soil solution and only a small depletion in the roots of CO2-enriched trees at the end of the first growing season. Therefore it is probably too early to decide wether the observed nutrient effects were due to the CO2-treatment or to the natural variability of the soil.
Keywords: elevated CO2, soil nutrients, nitrogen, forest, broadleaves