ISOTOPE DISCRIMINATION AND PHOTOSYNTHESIS OF VEGETATION GROWING IN THE BOSSOLETO CO2 SPRING

The Bossoleto CO2 spring emits CO2 which has a stable carbon isotopic ratio (delta(13)C = -8 parts per thousand). We determined delta(13)C o n leaves of several individual species growing in Bossoleto and in a n earby control site at ambient CO2. delta(13)C was 6% more negative in leaves of species collected from the grassland community of Bossoleto, indicating increased discrimination (Delta) against the heavy carbon isotope. No such changes were found in ruderal species growing in the same spring, suggesting that photosynthetic capacity was much less aff ected. Delta was substantially increased under elevated CO2 in leaves of Quercus pubescens but not in Quercus ilex, which also did not show any increase in non-structural carbohydrates. Gas-exchange measurement s made on Plantago lanceolata, supported the view that photosynthetic capacity is decreased in plants grown under elevated CO2 and on poor s oils. (C) 1998 Elsevier Science Ltd.