Trees for the Western Transvaal selected on the basis of arboretum trials

[摘要] ENGLISH ABSTRACT: Trees are needed on the semi-arid Highveld ofthe western Transvaal for shelterbelts, woodlots, fodder,honey, shade and ornament.A brief history of tree planting in the area,more particularly at Lichtenburg and Potchefstroom, isgiven.Relatively few species can be grown successfully in the western Transvaal because of the unfavourableclimate. Hot, dry winds blow almost continuously offthe Kalahari between August and October before the first,spring rains; cold winds and frosts are experienced inwinter, although the summers are hot; the rainfall iserratic and low, averaging about 600 mm. a year andoccurring mainly in the form of heavy thunderstormsduring summer; hail is common.The geology of the area is complex. In thenorth-west an overburden of wind-transported sand obscuresthe underlying formations. The soils are mostly of alight, sandy or loamy consistency, with a fairly highbase-saturation value. Concretions, sometimes forminga continuous hardpan, are characteristic of certaintypes.Various indigenous trees are found in somelocalities. These are small,and are mainly confined torocky hillsides and stream banks. In the past they havebeen much exploited for rough building timber, fence postsand firewood. Their growth is very slow, and exoticshave proved to be more vigorous as well as more usefulin cultivation.Possible adaptations of trees to dry climatesare discussed. It is concluded that'apparent adaptationsobserved in the field are of little value in selectingtrees for dry areas. No practical alternative thereforeexists at this stage to the introduction of species from.areas with a similar climate and testing these underlocal conditions. Parts of the world having a climatesimilar to that of the western Transvaal are in.dicated.Summarised results of species trials in thewestern Transvaal are given in tabular form, and recommendationsfor tree planting in the area are made.In an appendix, trials of BB species inarboreta at Lichtenburg and Potchefstroom are fullydescribed and discussed.

[发布机构] Stellenbosch University