THE EFFECT OF ELEVATED CO2 AND SOIL TYPE ON NONSTRUCTURAL CARBOHYDRATES IN BEECH LEAVES AND NORWAY SPRUCE NEEDLES GROWING IN MODEL-ECOSYSTEMS

Young beech and Norway spruce trees from two Swiss provenances were bo th planted in an acidic and calcareous soil in 16 open-top chambers. H alf of the plants were exposed to elevated CO2 (ambient, ambient + 200 mu l l(-1), 24 hrs/day, 365 days/year) and enhanced nitrogen depositi on (2.5, 25 kg ha(-1) yr(-1)) throughout a single growing season. Leaf and needle samples from all 64 trees were collected (2 provenances x 2 soil types x 4 treatments x 4 replications) at the end of July and S eptember. These were analysed for starch, soluble carbohydrates and to tal non-structural carbohydrates (TNC). Increased starch and TNC level s were found in plants under elevated CO2 and those growing on the aci dic soil. These effects were not consistent in both species or on both sampling dates. Soluble carbohydrates were only effected significantl y by sail type. So far no interactions have been found between CO2, N or soil type on any date and in any fraction. It is concluded that soi l type should be considered when discussing the effects of elevated CO 2 on starch, soluble carbohydrate or TNC contents in beech and spruce trees.