Light conditions

The availability of  light at ground level in the woodlands is primarily determined by the tree layer, which intercepts  the incoming sunlight  (van der Meulen & Werger 1984).  The amount of light that is transmitted through a tree canopy decreases, therefore, as the number of layers through which the light passes increase.  This, in turn, is affected by the architecture of the canopy plants (Prince 1987) as well as the number of canopies that overlap.

The growth form of plants, often species specific, has a significant effect on light interception.  Plants with spreading crowns, like many of the taller woodland trees in Namibia, intercept less light.  However, species like Guibourtia coleosperma and many Schinziophyton rautanenii trees have rounded crowns that intercept much light.

Light availability and woody plants

The amount of light that is available will then determine the species that are able to establish themselves.  Vermeulen (1990) has indicated, for instance, that Pterocarpus angolensis seedlings do not grow very well under other trees, but require open areas.  Similarly, Yeaton (1988) and Scholes & Walker (1993) report that Terminalia sericea seedlings are seldom found under the canopy of trees.  Seedlings of Schinziophyton rautanenii on the other hand seem togrow better in moderate shade than in full sun (Graz, unpublished data), as do those of Burkea africana (Yeaton 1988, Scholes & Walker 1993).