Elevated CO2 and nitrogen supply alter leaf longevity of grassland species

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Abstract
Summary: The longevity of green leaf area for 10 grassland species was measured to establish whether elevated CO2 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 CO2 (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 CO2 (+3.4 d, P = 0.03) and decreased under elevated N (−4.2 d, P = 0.03). Leaf longevity increased under elevated CO2 for C3 species only; there was no change in leaf longevity of C4 species under elevated CO2. For both CO2 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 CO2 and N, site fertility and the development of ecoystem feedbacks appear to be important in determining leaf longevity.