Abstract
Amongst all terrestrial ecosystems, the productivity of Mediterranean-type ecosystems has been suggested to be one of the most responsive to increasing atmospheric CO 2. The extent to which this prediction holds will depend in part on plant responses to elevated CO 2 under the highly variable conditions characteristic of semiarid regions. Structure and composition responses of a semi-natural grassland community to a step-increase in atmospheric CO 2 (to about 580 μmol mol -1 ) were examined in the field using Free-Air CO 2 Enrichment (FACE) under seasonally varying moisture conditions. The limited production response to elevated concentrations of atmospheric CO 2 of this grassland community was counterbalanced by the effect on the phenology of many species. These findings suggest that predictions regarding Mediterranean plant responses to elevated CO 2 should account for seasonal patterns of production regulatory responses, which may vary across species and plant functional types. © Akadémiai Kiadó Budapest.