Partenaires et organisations internationales
(Anglais)
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A, B, HR, CZ, DK, EE, FIN, F, D, GR, H, IS, IRL, I, LT, NL, N, PL, P, RO, E, S, CH, GB
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Résumé des résultats (Abstract)
(Anglais)
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In its 4th year of operation the Swiss Canopy Crane project offers insight into the future response of forest trees when CO2 concentration will have reached twice the pre-industrial level. Treering chronologies obtained now for the first time reveal a transitory growth stimulation by elevated CO2 in European beech during the first year of experimental CO2 enrichment, but later, trees return to 'business as usual'. Oak showed a slight, and hornbeam no response in year one, and none of the species responded thereafter. These data represent the first ever evidence for CO2 effects on the growth of mature trees in a natural forest, and they do not support the widespread assumption that forest trees will tie up more carbon in a CO2-rich world. After an initial adjustment, trees pump more CO2 through the ecosystem, but the biomass carbon pool appears to remain unaffected so far. We now have good evidence that biodiversity plays a key role in forest CO2 responses. In all aspects studied, trees show tree species specific responses. Major forest tree species clearly differ in their responses to CO2 in growth, carbon relations, water and nutrient relations. Stable carbon isotope data illustrate a rapid transfer of new carbon into tree tissues and into consumers of biomass such as canopy herbivores or mycorrhizal fungi. This COST-project revealed no evidence of a CO2-driven increase of carbon sequestration into biomass, but substantially greater amounts of carbon are pumped through the ecosystem, with unknown consequences.
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