The increasing CO
2 concentration in the atmosphere and its implication on agricultural productivity
I. Effects on photosynthesis, transpiration and water use efficiency
Norman J. Rosenberg
Received: 13 October 1980 Revised: 8 April 1981
Abstract The increasing concentration of CO
2 in the atmosphere should result in a general increase in the net primary productivity of most cultivated species and forest species, assuming no counterproductive climatic changes occur. The photosynthetic rate of C
3 plants is most responsive to increasing concentration of CO
2 in the ambient air. C
4 plants demonstrate a stomatal closure that causes reduced transpiration. In the case of both types of plants, the water use efficiency (photosynthesis/transpiration) is likely to be improved.
It has been suggested that photosynthetic production may be limited today more by shortages of water and nutrients than by shortages of carbon dioxide. The author speculates that the inadvertant
CO
2-fertilization
now occurring could, in itself, cause a moderate release from these constraints.
Physiological responses to an increased atmospheric CO2 concentration are easily demonstrated in controlled environment studies. Because of the difficulty in maintaining artifically enriched air near the crop against the forces of turbulent transfer, studies in the open field have been inconclusive. The observation of decreased photosynthetic rate in a perennial crop during that part of the growing season when CO2 concentration is naturally low suggests a technique by which it may be possible to infer what will happen in the real world of agricultural fields if a CO2-rich environment, such as is predicted in the coming decades, materializes. Inferences from the very limited set of data available support the view that net photosynthetic production will be increased.
Published as Paper No. 6123, Journal Series, Nebraska Agricultural Experiment Station. The work reported was conducted under Regional Research Project 11–33 and Nebraska Agricultural Experiment Station Project 1149.
George Holmes Professor of Agricultural Meteorology, Center for Agricultural Meteorology and Climatology, Institute of Agriculture and Natural Sources, University of Nebraska-Lincoln, Lincoln, NE 68583, U.S.A.
References secured to subscribers.