Seedling performance of pasture species under elevated CO2

The effects of elevated CO2 on seedling recruitment are presented for the pasture species Anthoxanthum odoratum, Cerastium glomeratum, Leontodon saxatilis, Lolium perenne, Poa pratensis and Trifolium repens. Seeds collected from pastures maintained at ambient (360 mul l(-1)) and elevated (475 mul l(-1)) CO2 were measured for germination and seedling growth in a reciprocal design under ambient and elevated CO2. Seedlings of A. odoratum and L. perenne from elevated-CO2-developed seeds were heavier than those from ambient-CO2-developed seeds but only when the seedlings were grown at elevated CO2. Elevated-CO2-developed seeds had higher germination and seedling mass in T. repens and lower germination and seedling mass in L. saxatilis, irrespective of the CO2 concentration after sowing. There were more L. saxatilis and T: repens seedlings in pastures maintained at elevated than ambient CO2; a seed addition experiment showed that this was due mainly to the increased seed production of these species under elevated CO2. Seedling recruitment of C. glomeratum and P. pratensis was unaffected by elevated CO2. Species exhibited variable responses to seed development under elevated CO2 that could potentially alter community composition by influencing seedling recruitment.