Measurement of canopy interception of solar radiation by stands of trees in sparsely wooded savanna
作者:
S. D. PRINCE,
期刊:
International Journal of Remote Sensing
(Taylor Available online 1987)
卷期:
Volume 8,
issue 12
页码: 1747-1766
ISSN:0143-1161
年代: 1987
DOI:10.1080/01431168708954814
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
A three-dimensional tree canopy model of scenes which consist of a discontinuous tree layer and a continuous field layer is described. ‘Scene’ or spatial average tree canopy layer transmissions are defined for direct solar radiation, diffuse sky radiation and emission of reflected radiation from the ground and field layers. Hemispherical canopy photographs are used to measure these three types of transmission and the measurements provide the parameters for the model which can be inverted to give estimates of the spatial average properties of a scene. The model requires only the frequency distribution of tree canopy diameters to be specified and these can be measured on the ground or on aerial photographs. The effect of each canopy is additive and so the model can be applied to any pattern and density of trees. Hemispherical photographs can be reinterpreted for any solar azimuth and zenith angle and are therefore applicable for long periods of time. Measurements in two areas of savanna woodland in Kordofan, Sudan, showed that canopy cover measured in the traditional way, which treats the canopy as opaque, overestimated interception by approximately half. Comparisons betweenAcacia Senegaland other species indicate that there are some significant differences in transmission characteristics between savanna tree species. The relevance of these observations to remote sensing of savanna field layer primary production is discussed.
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