A NEW FIELD TECHNIQUE FOR ELEVATING CARBON-DIOXIDE LEVELS IN CLIMATE-CHANGE EXPERIMENTS

1. A compact, low-cost, free-air carbon dioxide enrichment system for use in climate change experiments is described, The system has been us ed in a small-scale study of the effects of an enriched carbon dioxide atmosphere on the growth and functioning of a natural plant community , 2. The experiment ran for 4 months in summer on a nutrient-poor lime stone grassland in Derbyshire, The study examined the separate and com bined effects of elevated CO2, temperature and soil nutrient status on the growth of seedlings of obligate mycorrhizal and non-mycorrhizal p lant species native to the site. 3. It was demonstrated that the CO2 e levation could be controlled within the limits set for 64% of the time . Significant effects of elevated CO2 on the growth and recruitment of seedlings were found in the presence of added nutrients and elevated temperatures.