Further Responses to CO 2 Enrichment in British Herbaceous Species

CO 2 -enrichment experiments have been performed on 15 British herbaceous species of widely differing ecology. The conditions of growth were very similar to those used in a previous study and involved full-light glasshouse conditions, non-limiting supplies of water and mineral nutrients and a daytime mean temperature of 18 °C. Four CO 2 treatments were maintained (350, 500, 650 or 800 vpm) over periods of 49 or 52 days. Hyperbolic functions were fitted to yield vs CO 2 concentration. The functions were used to generate predictions of Q 540/350 (the quotient of the «present» yield which is predicted for the CO 2 regime expected by the year 2050) and Q 700/350 (the quotient predicted for a doubling of the present ambient CO 2 concentration). Values of Q 540/350 for whole-plant dry weight ranged from below 1.00 to 1.19 (...)