The Afromontane Forests of Transkei, Southern Africa. I
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22 S.-Afr.Tydskr. Plantk., 1989, 55(1): 22-30 The afromontane forests of Transkei, southern Africa. I: The importance of phytogeography and past utilization to the study of forest patches and a description of a sampling strategy S.G. Cawe* and B. McKenzie 1 Department of Botany, University of Transkei, Private Bag X1, Unitra, Transkei 1 Present address: Department of Botany, University of the Western Cape, Private Bag X17, Bellville, 7535 Republic of South Africa Accepted 18 July 1988 A brief overview of the distribution and exploitation of forests in southern Africa is presented as a basis for a sampling design and classification of forests. A sampling strategy was adopted for the quantitative study of disjunct forest patches in Transkei. The approach, which has not been used in southern Africa, is described. 'n Kort oorsig van die verspreiding en ontginning van inheemse woude in suidelike Afrika word voorgele as basis vir die bemonstering en klassifikasie van woude. 'n Bemonstering-strategie vir die kwantitatiewe studie van ge·,"soleerde woude in Transkei is ontwikkel. Die strategie, wat nie tevore in suidelike Afrika gebruik is nie, word beskryf. Keywords: Biogeography, exploitation, forest, sampling, synecology *To whom correspondence should be addressed Introduction grasses (Huntley 1984) . In the early literature (e .g. Sim This paper consists of two parts; the first part briefly 1907) the term 'forest' included both high forest (the reviews research and management reports pertaining subject of the present paper), scrub forest and various specifically to phytogeography, management and com types of open woodland characterized by Acacia and munity studies in southern African forests . The review is Protea spp. Although scrub forest is generally shorter done on a regional basis and in chronological sequence and has a lower canopy cover, it cannot always be in an attempt to highlight the effects of previous distinguished clearly from high forest. White (1983) exploitation, the success of the various methodologies elaborates on the similarities and differences of these that have been used in community studies and to identify vegetation types. areas that have been poorly classified. Geldenhuys' In southern Africa the forest biome occurs in scattered (1985) bibliography is used to determine literature patches covering some 200 000-300 000 ha on the trends. Publications (e.g. Bredenkamp & Theron 1978, eastern margin of the country (Figure 1) . Huntley (1984) 1980) which are listed in the bibliography but deal divides it into an afromontane and a lowland compon essentially with formations other than forest are not ent. The afromontane component, which is part of considered. White's (1983) region by the same name, occurs from The second part of the paper is a description of the Louis Trichardt (23°S) to the Cape peninsula (34°S) , sampling strategy adopted for the quantitative commun and the lowland component, which is part of White's ity study of the afromontane forests of Transkei. The (1983) Tongaland-Pondoland regional mosaic, occurs sampling strategy, which takes into account forest size , from the mouth of the Limpopo River (25°S) to Port has not been used in southern African forests before. Elizabeth (34°S). Moll & White (1978) recognize five This exercise was done in an attempt to evaluate the forest types in the lowland forest biome: undifferen feasibility of extracting timber from the indigenous tiated lowland, dune, swamp, sand and fringing forest. forests of Transkei on a commercial basis. The latter two are restricted to the northern extremity of the biome while swamp forest is found as far south as Literature survey Transkei. Undifferentiated lowland forest reaches the Phytogeography eastern Cape and dune forest is found throughout the The forest biome has been defined by the dominance of biome. Cooper (1985) further divides lowland forest into phanerophytes (Rutherford & Westfall 1986) , with trees two types: coastal and scarp forest on both floristic and having a continuous cover (White 1978) and a projected faunal differences. canopy cover of at least 75 % (Edwards 1983). In south Interest in the phytogeography of southern Africa has ern Africa canopy height varies between 10 m and 30 m been very keen since the 19th century, and according to depending on site factors (Acocks 1953 ; Moll & White Bayer (1970) the first vegetation map was published by 1978; White 1983). Other characteristics of the forest Drege in 1845. Numerous attempts have since been biome include the abundance of climbers and epiphytes made at mapping and classifying both the vegetation and (Hall & Swaine 1981) and the absence of fire and C4 the flora , the number of phytochorological taxa S.Afr.l. Bot., 1989,55(1) 23 Key to Forest Conservancies •• A Western Cape Conservancy B Midland Conservancy F " C Eastern Cape Conservancy ./ 0 Transkeian Conservancy • E Natal & Orange Free State F Transvaal Conservancy 1 Cape Town 0 150 300 km. , I • I I Stale (After King 1941) Figure 1 Distribution of the afromontane forest biome and conservancies in southern Africa. increasing with the burgeoning knowledge of the flora White's (1978, 1983) Tongaland-Pondoland regional (Werger 1978). The various authors were never mosaic is widest in the north where it reaches up to 240 unanimous on taxonomic ranks or on the boundaries of km and, in contrast, is never more than 8 km wide in the their phytochoria. The discrepancies were, to a large south. This region , which includes both a tropical and extent, due to a lack of consensus on nomenclature, each subtropical flora, penetrates into the interior in finger worker making his own subjective decisions as to the like projections along the major river valleys. Bews rank and extent of each floristic unit. Another problem (1921 , 1922) regards the sub-tropical flora as derivative was , and still is, that the distribution ranges of plants from tropical species which, in their southward rarely coincide, adjacent floras tending to merge into migration, responded to the colder and drier conditions one another over broad and diffuse zones of transition of the subtropics by becoming xeromorphic; the higher (Good 1974). incidence of spinescence, compound leaves and capsular Werger (1978) divides the South African flora into 6 fruit being some of the adaptations to the new climate. regions, two of them, the Tongaland-Pondoland White's (1978, 1983) Afromontane Region , on the Region and the Afromontane Region , encompassing the other hand, occurs in the hinterland on the highest forest biome. In a departure from the orthodox practice mountains except at its southern extremity, where the of dividing floras into mutually exclusive phytochoria in effect of latitude compensates for altitude allowing for a heirarchical system, White (1978, 1983) proposes a the occurrence of this flora along the coast (White 1978). non-hierarchical phytochorology which highlights broad The occurrence of afromontane elements at increas transition zones by giving them equal status with centres ingly lower altitudes and the migration of the sub of endemism. A further innovation in South African tropical flora from the coast inland along river valleys led phytochorology is the use of multidimensional scaling to considerable intermingling of these floras. Seemingly, and cluster analysis by Knight et al. (1982). In spite of floristic overlap is much more pronounced in southern the differences in approach, the latest floristic Africa than in East Africa because in an account of the classifications are comparable and are based either afromontane flora of the latter, Moreau (1952) suggests exclusively or mainly on the distribution of trees. that this flora is so different from the sub-tropical that 24 S.-Afr.Tydskr. Plantk., 1989, 55(1) the two must have evolved independently, yet Goldblatt theory may be one way to explain the past extent of (1978) quotes Hilliard as being of the opinion that many forest during the present climatic regime. An examin of the afromontane elements in southern Africa were ation of the alpha diversities of various patches in the derived from the lowlands, a view shared by White different regional complexes might help elucidate (1978, 1983). In Transkei, floristic overlap is very whether the patches were once linked up or not. What is pronounced, 11 of the 12 species used by White (1978, certain is that man has been directly or indirectly 1983) to characterize the afromontane region occurring responsible for modifying both the coverage and comp in the coastal forests. Von Breitenbach (1983) further osition of southern African forests. This aspect is estimates that 70% of the species in the afromontane discussed in the following section. region are also found along the coast. In this regard it is interesting to note that the phytochorology by Knight et Utilization and management at. (1982) does not differentiate between the afro Trends in the volume of literature on the utilization and montane and lowland components of the forest biome. management of indigenous forests in southern Africa are Despite the transitional nature of the tree flora of illustrated in Figure 2. Most of the early literature Transkei the afromontane forests are fairly distinct from comprised reports by forest conservators. Sim (1907) the lowland forests, containing only about 50% of the collated these reports into a single volume. As timber species of the coastal forests (von Breitenbach 1983) . from the indigenous forests became exhausted during What is more uncertain is the previous extent of forest the second quarter of this century several reviews on the coverage. Axelrod & Raven (1978) and van Zinderen utilization and management of the indigenous forests Bakker (1978) postulate that forests were more were published, notably by Laughton (1937) and King extensive under moister and cooler conditions, but of (1938 , 1939, 1941). particular interest to phytosociology is the past coverage The large volume of literature on indigenous forests of the forests under the present climatic regime.