| Popis: |
The amount of absorbed solar radiation is an important factor in the energy balance of leaves and depends largely on their spectral properties. In a Sourish Mixed Bushveld (Roodeplaat Dam Nature Reserve, Transvaal) measurements of the spectral properties of leaves of 26 trees and shrubs were made to determine whether or not the occurrence of a species under the different radiation regimes (inside a bush clump or in the open) is influenced by these spectral properties. The absorptance of the investigated leaves is uniform (58,7 ± 2,3%) but, mainly for the infrared fraction of the solar radiation, is achieved in different ways; either by a high reflectivity and a low transmissivity or vice versa. Values for the reflectance, transmittance and absorptance of the different species are given and variations are discussed. The small variation in the absorptance leads to the conclusion that other morphological (e.g. leaf orientation) or physiological (e.g. water availability) features must be more significant for the occurrence of a species in or outside a bush clump. |
