THREE-DIMENSIONAL DISTRIBUTION OF LIGHT INTENSITY IN THE DRY DIPTEROCARP FOREST AT SAKAERAT, NORTHEASTERN THAILAND

Abstract

The frequency distribution of relative light intensity at various height levels in an undisturbed dry dipterocarp forest at Sakaerat, northeastern Thailand was closely approximated by the lognormal distribution, proving that the geometric mean was more reasonable than the arithmetical mean as the representative value of light intensity received by a certain height level under the leaf canopy. The mean value tended to decrease exponentially with decreasing height in each of the three layers between o m and 2 m. (ground vegetation), 2 m and 16 m (lower strata) and over 16 m (upper strata) above the ground level. This suggested that the leaf area density was more or less homogeneously distributed in the vertical direction within each of the three layers. A diagrammatic representation of the threedimensional distribution of relative light intensity in the forest canopy was presented.