Elevated CO 2 and nitrogen supply alter leaf longevity of grassland species

• The longevity of green leaf area for 10 grassland species was measured to establish whether elevated CO 2 and N fertilization alter leaf longevity, an important determinant of ecosystem leaf area and ecosystem carbon gain. • Plants were selected from monocultures in their second year of growth in a field experiment that directly manipulated atmospheric CO 2 (550 ppm and ambient) and nitrogen fertilization (4 g N m − 2 and ambient). Leaves were censused biweekly over a 4-month period. • Leaf longevity increased under elevated CO 2 ( + 3.4 d, P = 0.03) and decreased under elevated N ( − 4.2 d, P = 0.03). Leaf longevity increased under elevated CO 2 for C 3 species only; there was no change in leaf longevity of C 4 species under elevated CO 2 . For both CO 2 and N, changes in leaf longevity were congruent with expectations based on observed changes in N cycling. • In addition to supplies of resources such as CO 2 and N, site fertility and the develop ment of ecoystem feedbacks appear to be important in determining leaf longevity.