Increase in C3 plant water-use efficiency and biomass over Glacial to present CO₂ concentrations
1993
Polley, H.W. | Johnson, H.B. | Marino, B.D. | Mayeux, H.S.
Atmospheric CO₂ concentration was 160 to 200 micromole mol-1 during the Last Glacial Maximum (LGM; about 18,000 years ago), rose to about 275 micromole mol-1 10,000 years ago, and has increased to about 350 micromole mol-1 since 1800 (ref. 4). Here we present data indicating that this increase in CO₂ has enhanced biospheric carbon fixation and altered species abundances by increasing the water-use efficiency of biomass production of C3 plants, the bulk of the Earth's vegetation. We grew oats (Avena sativa), wild mustard (Brassica kaber) and wheat (Triticum aestivum cv. Seri M82 and Yaqui 54), all C3 annuals, and selected C4 grasses along daytime gradients of Glacial to present atmospheric CO₂ Concentrations in a 38-m-long chamber. We calculated parameters related to leaf photosynthesis and water-use efficiency from stable carbon isotope ratios (13C/12C) of Whole leaves. Leaf water-use efficiency and above-ground biomass/plant of C3 species increased linearly and nearly proportionally with increasing CO₂ concentrations. Direct effects of increasing CO₂ on plants must be considered when modelling the global carbon cycle and effects of climate change on vegetation.
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