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Journal Article

Light Intensity Measurements in Rain Forest Near Santarem, Brazil

P. S. Ashton
Journal of Ecology
Vol. 46, No. 1 (Mar., 1958), pp. 65-70
DOI: 10.2307/2256903
Stable URL: http://www.jstor.org/stable/2256903
Page Count: 6
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Light Intensity Measurements in Rain Forest Near Santarem, Brazil
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Abstract

1. A series of photometer readings were taken near Monte Alegre, Para, Brazil, on 7 August 1954. 2. These observations were made in Evergreen Rain forest at the beginning of the dry season, when there were probably fewer leaves on the trees than at any other time. 3. The readings were taken at different heights in the forest, all up one tree, from dawn to dusk during one day. 4. Despite limitations caused by the method used, the observations showed that: (a) The ground level series corresponded remarkably with those obtained by more complex methods by Evans (1939) in Nigeria. (b) The density of the second storey was the predominant controller of light intensity and duration of day when sunflecks were present within the forest canopy. (c) The shading effect of the emergent canopy is thrown over a considerable area of the neighbouring forest as the sun passes round, thus leaving few parts of the second storey unshaded, at least during one part of the day. 5. The method shows that though the worker in the tropics may have only a simple apparatus, unsuited to this type of work, the results can still be worthwhile.

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