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An Evaluation of the Photosynthetic Efficiency of Forests

Henry Hellmers
The Quarterly Review of Biology
Vol. 39, No. 3 (Sep., 1964), pp. 249-257
Stable URL: http://www.jstor.org/stable/2820035
Page Count: 9
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
An Evaluation of the Photosynthetic Efficiency of Forests
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Abstract

Data available on the photosynthetic efficiency of forest trees are reviewed. Results from the different sources suggest that over a growing season a stand of trees has a relatively high photosynthetic efficiency in comparison to that of an agricultural crop. Three factors that possibly could cause a high over-all efficiency are suggested: (a) low efficiency of agricultural crops in the early part of the season until canopy closure, whereas the tree stands studied usually had complete canopy closure all season; (b) the available forest data are from areas with low light intensity, which tends to increase the efficiency of light utilization; (c) carbon dioxide becomes limiting for photosynthesis in stands of plants under full sunlight, but because of the physical structure of the plant communities, forest stands possibly have more carbon dioxide available to them than do agricultural crop.

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