414 J. AV. BKWS. 



6. Tree Veld. * 



(PI. XXIII, fig. 2; PI. XXIV, figs. 1 and 2.) 



There are various types of tree veld on the coast belt, con- 

 sisting of more mesophytic species on the south coast and of 

 thorn veld dominated by species of Acacia and Euphorbia 

 on the drier, hotter portions of the north coast, from A^'erulam 

 to the Tugela and beyond it in Zululand, The tree veld 

 plant succession for typical thorn veld has been analysed in 

 considerable detail in one of my former papers.^ Various 

 pioneer species of trees, e.g. the Acacias, Cussonias, Euphor- 

 bias, Celastrus buxifolius, Albizzia fastigiata,. 

 Dichrostachy s nutans, the seeds of which are able to 

 germinate among the grasses of the grassveld and the- 

 seedlings of which can withstand full exposure from the 

 start, grow up as isolated specimens, forming a park-like 

 type of plant community. The pioneers are not shrubs as in 

 other forest seres. Many other species both of trees and 

 shrubs (including numerous climbei's) which are not able to 

 act as pioneers find a suitable germinating ground under the 

 shade of the pioneer tree, where the soil is loosened and 

 prepared for them by the activities of earthworms, termites, 

 etc. The pioneer itself frequently grows up from an old 

 termite nest, which thus forms the starting-point for the 

 formation of a chai'acteristic clump. The seeds of the 

 majority of the species are disti-ibuted b}^ birds, which 

 naturally alight on the branches of the pioneer tree. Fruit- 

 eating bats, too, are very common agents of dispersal. The 

 seeds of some of the pioneers, however, e.g. the Acacias, are 

 often distributed uniformly through the grassveld by grazing 

 herbivores. 



The pioneers are not only light-demanding xerophytic 

 species, but they are also resistant to grass-fires. The second 

 stage of the succession is seen, when the later arrivals grow 

 up round the pioneer tree and tend to smother it. Thus 



' Bews, J. W., " The Plant Succession in the Thorn Veld." ' South 

 African Journ. of Science,' November, l!:*!?. 



