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Carbon Dioxide and Water Fluxes of C3 Annuals and C3 and C4 Perennials at Subambient CO2 Concentrations
H. W. Polley, H. B. Johnson and H. S. Mayeux
Vol. 6, No. 6 (1992), pp. 693-703
Published by: British Ecological Society
Stable URL: http://www.jstor.org/stable/2389966
Page Count: 11
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1. The C3 annuals, Avena sativa and Brassica kaber, and C3 and C4 perennials, Prosopis glandulosa and Schizachyrium scoparium, respectively, were grown in a 38-m long chamber along a continuous gradient of daytime CO2 concentrations ([CO2]) from near the current 350 μ mol mol-1 to 150 (annuals) or 200 μ mol mol-1 (perennials). Diurnal CO2 and water fluxes were calculated for plant stands in five consecutive, 7.6-m lengths of the chamber arranged linearly along the [CO2] gradient. 2. The ratio of night respiration (RN) to daytime net assimilation (PD) was greatest in A. sativa/B. kaber exposed to mean [CO2] below 200 μ mol mol-1, while RN/PD differed little among five stands of P. glandulosal S. scoparium that were grown at mean [CO2] from 219 to 331 μ mol mol-1. 3. Evapotranspiration was reduced and water-use efficiency (WUE) was increased in A. satival B. kaber stands by higher [CO2]. 4. PD and WUE of P. glandulosal S. scoparium were not related to [CO2] across either of two growing seasons. Both PD and WUE, however, were greater at higher [CO2] in three of four stands when [CO2] was varied on consecutive days. 5. We conclude that past increases in atmospheric [CO2] have promoted higher WUE and increased carbon uptake in C3-dominated ecosystems.
Functional Ecology © 1992 British Ecological Society