EFFECTS OF LONG-TERM ELEVATED [CO2] FROM NATURAL CO2 SPRINGS ON NARDUS-STRICTA - PHOTOSYNTHESIS, BIOCHEMISTRY, GROWTH AND PHENOLOGY

Plants of Nardus stricta growing near a cold, naturally emitting CO2 s pring in Iceland were used to investigate the long-term (> 100 years) effects of elevated [CO2] on photosynthesis, biochemistry, growth and phenology in a northern grassland ecosystem. Comparisons were made bet ween plants growing in an atmosphere naturally enriched with CO2 (appr oximate to 790 mu mol mol(-1)) near the CO2 spring and plants of the s ame species growing in adjacent areas exposed to ambient CO2 concentra tions (approximate to 360 mu mol mol(-1)). Nardus stricta growing near the spring exhibited earlier senescence and reductions in photosynthe tic capacity (approximate to 25%), Rubisco content (approximate to 26% ), Rubisco activity (approximate to 40%), Rubisco activation state (ap proximate to 23%), chlorophyll content (approximate to 33%) and leaf a rea index (approximate to 22%) compared,vith plants growing away from the spring. The potential positive effects of elevated [CO2] on grassl and ecosystems in Iceland are likely to be reduced by strong down-regu lation in the photosynthetic apparatus of the abundant N, stricta spec ies.