Of the Proposed Vhembe-Dongola National Park, Limpopo Province, South Africa

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Analysis of the riparian vegetation (Ia land type) of the proposed Vhembe-Dongola National Park, Limpopo Province, South Africa

A.R. GÖTZE, S.S. CILLIERS, H. BEZUIDENHOUT and K. KELLNER

A.R. Götze, S.S. Cilliers, H. Bezuidenhout and K. Kellner. 2003. Analysis of the riparian vegetation (Ia land type) of the proposed Vhembe-Dongola National Park, Limpopo Province, South Africa. Koedoe 46(2): 45-64. Pretoria. ISSN 0075-6458. The establishment of the Vhembe-Dongola National Park has been an objective of several conservationists for many years. The ultimate objective is that this park would become a major component of a transfrontier park shared by Botswana, Zimbabwe and South Africa. The aim of this study was to identify, classify and describe the plant communities present in the Ia land type of the proposed area for the park. Sampling was done by means of the Braun-Blanquet method. A total of 70 stratified random relevés were sampled in the Ia land type. All relevé data was imported into the database TUR- BOVEG after which the numerical classification technique TWINSPAN was used as a first approximation. Subsequently Braun-Blanquet procedures were used to refine data and a phytosociological table was constructed, using the visual editor, MEGATAB. From the phytosociological table four plant communities were identified and described in the Ia land type. The ordination algorithm, DECORANA, was applied to the floristic data in order to illustrate floristic relationships between plant communities, to detect possible gradients in and between communities and to detect possible habitat gradients and/or disturbance gradients associated with vegetation gradients. Key words: national parks, phytosociology, vegetation classification, Braun-Blanquet procedures, Savanna Biome.

A.R. Götze, S.S. Cilliers and K. Kellner, School of Environmnetal Sciences and Devel- opment, Section Botany, Rivate Bag X6001, Potchefstroom University for C.H.E., Potchefstroom, 2531; H. Bezuidenhout, Conservation Services, S.A. National Parks, P.O. Box 110040, Hadison Park, Kimberley, 8306 Republic of South Africa.

Introduction (Willcox 1966). The significance of this proposed park and its surrounding areas is fur- The establishment of the Vhembe-Dongola ther enhanced by the potential role of the National Park has been an objective of sever- area as a sanctuary for some of the most al conservationists for many years and was endangered mammals on earth, such as the finally approved by South African National Black Rhino and the African wild dog Parks in 1994 (Robinson 1996). This action (Robinson 1996). follows after a long history of proposals to this regard, starting in 1922 from an initiative The ultimate objective is that the Vhembe- of General J.C. Smuts to form the Dongola Dongola National Park would become a Botanical Reserve (Carruthers 1992). The major component of a transfrontier park conservation value of this area lies in it’s rich shared by Botswana, Zimbabwe and South biodiversity, it’s great scenic beauty and the Africa. The total area of this transfrontier cultural importance of the archaeological park could potentially add up to 2530 km² treasures of Mapungubwe which is included (Robinson 1996). Certain parts of the pro- in the proposed area for this national park. posed area for the Vhembe-Dongola Nation- The artifacts found at Mapungubwe rank al Park is, however, extremely degraded among the most important pieces of ancient because of a combination of anthropogenic history yet found in sub-Saharan Africa influences, such as mining, cultivation, over-

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grazing and trampling by livestock as well as agement has moved more in the direction of other management malpractices (Götze total environmental management. Emphasis 2002). A large military base of the former in conservation is not on strictly policed, South African Defence Force was also situ- protected areas, primarily for large mammals ated on the farm Greefswald, and con- anymore, but on sustainable resource use, tributed to the disturbance and degradation maintenance of ecological processes and of the area. Old campsites litter the proposed conservation of genetic diversity (Winter- area and the scars left by forgotten roads, bach 1998). A sound knowledge of the vege- quarries and dumpsites are a cruel sight to tation ecology of areas of conservation sig- the eye (Götze 2002). It is, therefore, evident nificance is essential for the establishment of that specific restoration and rehabilitation efficient wildlife and environmental man- practices should be implemented in an agement programs and the compilation of attempt to restore the land to a higher poten- conservation policies (Bredenkamp & tial for the conservation of our precious Theron 1978; Bredenkamp et al. 1993; fauna and flora. Bezuidenhout 1996; Van Rooyen et al. Of all the land types in the Vhembe-Dongo- 1981). Different ecosystems react differently la National Park the Ia land type which to certain management practices (Bre- include the riparian areas seems to be the denkamp & Theron 1976) and therefore, in most disturbed, mainly because of the exten- order to formulate a management policy, siveness of this linear landscape, the high where proper land use is emphasised, the fertility of the soils and the consequent classification of the vegetation is essential establishment of irrigation lands (Götze (Van Rooyen et al. 1981; Bezuidenhout 2002). The riparian zone can be identified as 1993). It is widely recognised that a detailed the area of land adjacent to a stream or river, description, identification, classification and which is, at least periodically, influenced by mapping of the vegetation, form the basis for fluctuations of the water level (Rogers sound land-use planning and management 1995). Although the Ia land type is (Fuls 1993; Bezuidenhout 1996; Brown overutilised by small and large livestock, the 1997). destruction caused by migratory Tuli Ele- The aim of this study is to identify, classify phants, from neighboring Botswana, is an and describe the plant communities present additional cause for concern. Furthermore, in the Ia land type of the proposed area for riparian zones warrant special attention since the Vhembe-Dongola National Park. This their positioning in the landscape ensures study forms part of a bigger study on the that they play direct roles in the functioning vegetation of all the land types included in of both the river system and the terrestrial the proposed Vhembe-Dongola National landscape and are one of the major centers of Park. biodiversity in a global context (Naiman et al. 1993). The narrow spatial dimensions and open endedness of riparian wetlands make Study area them highly sensitive to landscape changes, with major consequences to the river ecosystems which they buffer from terrestrial influ- Location ences (Naiman & Décamps 1990; Rogers The proposed area for the Vhembe-Dongola 1995). National Park is centered on the confluence The current state of the proposed area for the of the Limpopo and Shashi Rivers, in the Vhembe-Dongola National Park and the Limpopo Province, on the international bor- uniqueness of the area with respect to diver- ders between Botswana, Zimbabwe and sity and cultural importance warrant the South Africa (Robinson 1996) (Fig. 1). The establishment of detailed management prac- primary core area spans from Pontdrif in the tices. In the past decade conservation man- west to Weipe in the east incorporating 22

Koedoe 46/2 (2003) 46 ISSN 0075-6458 gotze.qxd 2005/12/09 10:52 Page 47 Fig. 1 Relative location of the Ia land type in the proposed area of the Vhembe-Dongola National Park area Relative location of the Ia land type in proposed

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farms with a surface area of 28 000 ha the Limpopo River the flats give way to a (Fig. 1). more rugged, hilly terrain. The soils of the Limpopo Valley are derived from rocks of the Archaean granite formations in the south Land types and, more generally, from the Karoo-system In South Africa land types have been used as (Stormberg, Ecca and Beaufort Series). The a map unit denoting land, mappable at soils vary from red-brown sandy loam to 1:250 000 scale, over which there is marked dark brown clays with high silt content. uniformity of climate, terrain form and soil Large areas are characterised by sandy, lime- pattern. The Ia land type (Fig. 1) includes the rich soils (Robinson 1996). The geology of riverine and non-perennial wetland vegeta- the Ia land type consists of sand and alluvi- tion with deep to moderately deep soils with um from the Quaternary System and deep a high silt and clay content. Other land types red/brown, alluvial soil forms (Oakleaf) and which occur within the proposed area of the some duplex soils (Valsrivier & Arcadia) Vhembe-Dongola National Park are the Ae, dominate the soils of this land type (Land Db, Fb and Ib land types (Fig. 1) (Land Type Type Survey Staff 2000). Survey Staff 2000). Vegetation Climate According to Van Rooyen & Bredenkamp The climate is semi-arid with the long-term (1996), the area is situated in vegetation type mean annual rainfall ranging from 350 mm no. 10, Mopane Bushveld, while Acocks to 400 mm per annum (Willcox 1966; Robin- (1988) placed it in veld type no.15, also son 1996). Rainfall is highly variable and Mopane Veld. According to Acocks (1988), usually falls during the summer months there are two major blocks of Colophosper- between October and March. Evaporation mum mopane veld. One of these blocks of from free water surfaces is in excess of Colophospermum mopane is situated in the 2 500 mm per annum for the largest part of Limpopo Valley north of the Soutpansberg the area. In summer the temperatures rise as and the other to the east of the Soutpansberg. high as 45 °C (Weather Bureau 1986). The The conservation status of the eastern block, winters are mild, although frost may occur in which occurs in the Kruger National Park is low-lying areas (Robinson 1996). sound with 89% of the area protected. The western block is not well represented in conservation areas with only 0,36% being for- Hydrology mally protected (Berry 1994; Robinson Surface drainage is mostly in a northerly 1996). direction towards the Limpopo River. None The former Transvaal Provincial Adminis- of the rivers in the area, including the tration (Transvaal Provincial Administration Limpopo, are perennial. Ground water sup- 1989) recognised three main vegetation units plies are generally poor in the region except in the region: the riparian fringe along the where these occur along well-developed Limpopo River and its tributaries, the Aca- fault lines (Van den Heever 1983; Robinson cia-Salvadora communities of the Limpopo 1996). flats (including flood plains) and wetland areas, and the mixed mopane veld on ridges and flats south of the riparian fringe and Geology, geomorphology and soils flood plains. Other vegetation studies done The area is between 300 m and 780 m above in the Vhembe-Dongola National Park and sea level. South of the Limpopo River the surrounding areas in the past, include sever- ground tends to be flat with sandstone and al unpublished studies, namely a terrain and conglomerate ridges and koppies. Closer to vegetation evaluation by the former South

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African Defence Force (South African Braun-Blanquet cover abundance values were Defence Force 1986a, 1986b), a study of appointed to all plant species encountered in the vegetation types in the Limpopo-Venetia relevés (Table 1). Nature Reserve (O’Connor 1991) and a veg- Plant species identification was done by following etation survey of the Maramani/Tuli Area in Arnold & De Wet (1993), but are updated according Southwestern Zimbabwe (Timberlake & to the PRECIS floristic database of South Africa, Mapaure 1999). managed by the National Botanical Institute in Pre- toria. Soil classification is according to the Soil Clas- sification Work Group (1991). Trees and shrubs were Cultural historical assets distinguished from each other using the guidelines Robinson (1996) stated that the proposed set by Edwards (1983). Trees are classified as root- area of the Vhembe-Dongola National Park ed, woody, self-supporting plants over 2 m high with one or up to three definite trunks and shrubs are clas- has numerous archaeological sites dating sified as rooted, woody, self-supporting, multi- from the Early Stone Age to the present. stemmed or single-stemmed plants less than 2 m Many of these sites, which are concentrated high (Edwards 1983). in the area of the confluence of the Limpopo and Shashi Rivers, are of major importance The habitat conditions including geology, soil forms and scientific value. Of particular interest are and other edaphic factors, slope, aspect and the rock- the Zhizo site (AD 700-900) on the farm iness of the soil surface, of each relevé, were quali- tatively described. This information was used in the Schroda, and Mapungubwe Hill and the description of the different plant communities. The adjoining Bambandyanalo (AD 1100-1250) coordinates of each relevé were determined and situated on Greefswald. According to Voigt noted with the use of a GPS. & Plug (1981) the Mapungubwe site is con- sidered to be of major importance in Sub- Saharan Africa and is the most remarkable Data processing Iron Age site in South Africa. Additional fea- All relevé data has been imported into the database tures of importance are the numerous rock TURBOVEG (Hennekens 1996a). The numerical paintings and petroglyphs found in the area. classification technique TWINSPAN (Hill 1979a), which is regarded as a successful approach for classification by several phytosociologists (Mucina & Methods Van Der Maarel 1989; Bredenkamp & Bezuidenhout 1995; Cilliers 1998) was used as a first approximation for the floristic data. Subsequently Braun-Blan- Stratification quet procedures (Bezuidenhout et al. 1996) were used to refine data and construct a phytosociological With the aid of 1:50 000 topographical maps, geo- table (Table 1) using a visual editor, MEGATAB logical maps and vegetation and soil maps compiled (Hennekens 1996b). Uncommon species not diag- by the old South African Defence Force 1986 a,b), a nostic for any of the communities are not included in land type map of the area (Land Type Survey Staff 2000) and aerial photographs, a preliminary evalua- the table, but can be witnessed in Götze (2002). tion of the study area was made. In conjunction with Using the phytosociological table and the habitat the maps, a detailed reconnaissance of the area was information gathered during the sampling period, the done to determine homogeneous areas in the vegeta- different plant communities were identified and tion, before sampling commenced. Land types were described. No attempt was made in this study to for- used as a means of primary stratification of the study mally name the plant communities. This will only area. follow after extensive studies on Savanna vegetation in South Africa to prevent synonymy of syntaxa names. Sampling An ordination algorithm, DECORANA (Hill 1979b), Making visual estimates, sampling was done by was applied to the floristic data in order to illustrate means of the Braun-Blanquet method (Mueller- floristic relationships between plant communities Dombois & Ellenberg 1974). A total of 70 stratified and to detect possible habitat gradients and/or distur- random relevés were sampled in the Ia land type. bance gradients associated with vegetation gradients.

ISSN 0075-6458 49 Koedoe 46/2 (2003) gotze.qxd 2005/12/09 10:53 Page 50 Table 1 Table Phytosociological table of the vegetation Ia land type Vhembe-Dongola National Park.

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Results and discussion that are found in this community have a high silt and moderate clay content. Classification This community is situated higher above the annual flood level than its neighbouring From the phytosociological table (Table 1) communities, and as a result, appears to be the following plant communities, sub-com- drier. The slight slope is generally in the munities and variants were recognised: main direction leading towards the Limpopo 1. Salvadora australis-Cucumis zeyheri River. A further observation was that the soil Community surface is compacted through years of over- 1.1 Colophospermum mopane-Eragrostis grazing by cattle and a large number of game trichophora Sub-community that frequent the area, and therefore a high 1.2 Indigastrum costatum subsp. macu- degree of surface runoff is apparent. In some lata-Setaria verticillata Sub-com- extreme cases this has led to a degree of sur- munity. face erosion. 1.2.1 Aristida congesta-Leucas The vegetation of the Salvadora australis – sexdentata Variant. Cucumis zeyheri Community varies between 1.2.2 Eragrostis racemosa-Acacia open woodland, thickets and forests. The tortilis Variant diagnostic species of this community are 1.3 Combretum imberbe-Abutilon found in Species group A (Table 1), and ramosum Sub-community include the forbs Cucumis zeyheri, Boer- 2. Hyphaene petersiana - Acacia tortilis havia erecta, Heliotropium ovalifolium, Community Phyllanthus parvulus and Ipomoea sinensis 2.1 Ximenia americana-Flueggea virosa subsp. blepharosepala. Salvadora australis Sub-community (Species group K, Table 1) and the herba- 2.2 Cordia monoica Sub-community ceous Cucumis zeyheri, Boerhavia erecta (Species group A, Table 1) and Setaria verti- 3. Croton megalobotrys-Combretum micro- cillata (Species group P, Table 1) dominate phyllum Community the vegetation of this community. The 3.1 Cenchrus ciliaris-Faidherbia albida absence of the species that are found in Sub-community. Species group O (Table 1) differentiates this 3.2 Acacia schweinfurthii - Maytenus community from most of the other commu- senegalensis Sub-community. nities in the Ia land type. 4. Diplachne fusca - Acacia xanthophloea Three sub-communities were identified in Community this community:

1.1 Colophospermum mopane-Eragrostis Description of the plant communities trichophora Sub-community This sub-community is situated on the very 1. Salvadora australis-Cucumis zeyheri outskirts of the floodplain. It is situated on Community sandy Hutton soils with surface erosion This community mostly occurs on the flood- clearly visible as there are usually drainage plain, toward the outskirts of the lush river- systems running off towards the Limpopo River, bisecting this vegetation unit. ine forest belt found along the main river systems in the study area. A wide spectrum Diagnostic species of this sub-community of soil types was found, with Oakleaf being are found in Species group B (Table 1), the dominant soil form and Hutton, and Val- which includes the tree species Colophos- srivier soil forms in close support. With the permum mopane the grass Aristida adscen- exception of one sub-community, the soils sionis and the forbs Phyllanthus angolensis,

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Becium filamentosum and Melhania rehman- The tree layer of this sub-community reach- nii. The tree layer is dominated by Colophos- es heights of between 2.2 m and 8 m (in permum mopane (Species group B, Table 1) some cases > 8 m). The crown cover of the and to a lesser extent Salvadora australis tree layer varies between 20 % and 45 %. (Species group K, Table 1). The shrub layer The shrub layer has an average height of is sparse. The grass species Eragrostis tri- 1.4 m and the crown cover varies between chophora (Species group K, Table 1) and the 5 % and 25%. The herbaceous layer is well annual grass Aristida congesta subsp. con- developed with an average crown cover of gesta (Species group D, Table 1) dominate 80% and heights varying from 0.2 m to the herbaceous layer. 0.9 m. The tree layer of this sub-community reach- The Indigastrum costatum subsp. maculata – es heights of between 2.5 m and 4.0 m and Setaria verticillata sub-community has two has an average crown cover of 35 %. The variants, which differ from each other with shrub layer has an average height of 1.4 m respect to soil types and vegetation structure. and the cover varies between 10 % and 35 %. The herbaceous layer reaches an aver- 1.2.1 Aristida congesta-Leucas age height of 0.5 m and a crown cover of sexdentata Variant. between 45 % and 65 %. This variant comes in the form of open woodlands with Salvadora australis 1.2 Indigastrum costatum subsp. macu- (Species group K, Table 1) occurring in lata-Setaria verticillata Sub-com- bush-clumps. The soils that are found in this munity. variant have a high silt content and consist of The soil forms occurring in this sub-commu- the Hutton and Oakleaf soil forms. nity are Hutton, Oakleaf and Valsrivier. The There are no diagnostic species to this vari- sub-community is situated on a level flood- ant. The absence of Species groups E and H plain of which the soil surface gets trampled (Table 1) as well as a low frequency of the to a fine dust during the dry season. The area tree species Acacia tortilis and the shrub is targeted by high degree of grazing by Abutilon austro-africana (Species group K, game and, therefore the area shows signs of Table 1) do, however, differentiate this vari- degradation through the appearance of bare ant. It is further distinguishable from the patches in the grass layer. Due to flooding in Eragrostis racemosa – Acacia tortilis Vari- high rainfall years, as well as the high ant (1.2.2) by Species group D (Table 1) and resilience of this floodplain area, any the presence of the woody species Acacia restoration practices are uncertain at this stuhlmannii, and a high abundance of the stage. grass Eragrostis trichophora (Species group The vegetation of this sub-community varies K, Table 1). between open woodlands and thickets. The The tree cover of this variant is between species that are diagnostic to this sub-com- 20 % and 35 %, and the height of the trees munity are found in Species group C alternating between 2.2 m to 4.0 m. In some (Table 1) and include Indigastrum costatum isolated places there is no tree cover at all. subsp. maculata, Tribulus terrestris and the The shrub layer reaches an average height of scarce herbaceous climber Kedrostis lim- 1.3 m and the crown cover varies between pompensis. The species of Species group F 5 % and 20 %. The herbaceous layer covers (Table 1), indicates a similarity between this between 60 % and 90% of the variant area sub-community and the Colophospermum and reaches an average height of 0.5 m. mopane – Eragrostis trichophora Sub-com- 1.2.2 Eragrostis racemosa-Acacia munity (1.1). tortilis Variant

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This thicket variant of the Indigastrum ramosum (Species group H, Table 1) and the costatum subsp. maculata – Setaria verticil- grass Urochloa mosambicensis (Species lata Sub-community forms a boundary group K, Table 1) dominate the vegetation in between the open woodlands of the Aristida this sub-community. Diagnostic species of congesta – Leucas sexdentata Variant (1.2.1) the Combretum imberbe-Abutilon ramosum and the other riverine forest communities Sub-community is found in Species group G and sub-communities. The Valsrivier and (Table 1), which include the tree species Oakleaf soil forms found in this variant have Combretum imberbe and the herbaceous a high clay content and appear to be less dry Solanum species. The absence of the species compared to the open woodland communi- that are found in Species group F (Table 1) ties. differentiates this sub-community from the other two in the Salvadora australis- The species of Species group E (Table 1) are Cucumis zeyheri Community (1). Species diagnostic to this variant, which include the with high cover abundance values that fur- grass species Eragrostis racemosa and the ther differentiate this sub-community from forb Ctenolepis cerasiformis. A species with the Colophospermum mopane-Eragrostis high abundance that further differentiate this trichophora Sub-community (1.1) and the variant from the Aristida congesta-Leucas Indigastrum costatum subsp. maculata- sexdentata Variant (1.2.1) is the woody Setaria verticillata Sub-community (1.2) are species Acacia tortilis (Species group K, Lycium cinereum (Species group H, Table 1) Table 1). in the woody component and the shrub Abu- The vegetation cover of this variant is tilon austro-africanum (Species group K, markedly higher than that of the Aristida Table 1). The grasses Echinochloa colona congesta-Leucas sexdentata variant (1.2.1). (Species group H, Table 1) and Panicum Salvadora australis and Acacia tortilis maximum (Species group P, Table 1) and the (Species group K, Table 3) dominate the tree forbs Cucumis metuliferus and Dicliptera layer. The tree cover is 40 % on average and eenii (Species group H, Table 1) also differ- it reaches heights of between 3.5 m and entiate this sub-community. > 8 m. The shrub layer has an average height Trees with an average height of more than of 1.4 m with an average crown cover of 7 m and a crown cover of approximately 20 %. The herbaceous layer has an average 50 % dominate the vegetation of this sub- crown cover of 82 % and reaches an average community. The shrub layer reaches an aver- height of 0.5 m. age height of 1.4 m and the shrub cover varies between 5 % and 30 %. The herbaceous layer covers between 30 % and 70 % 1.3 Combretum imberbe-Abutilon of the sub-community with an average ramosum Sub-community height of 0.4 m. This sub-community is situated in the riverine forest and in some cases on the fringes of the Acacia xanthophloea - Diplachne fusca 2. Hyphaene petersiana - Acacia tortilis Community (4) on the floodplain of this land Community type. Soil forms include Valsrivier, Oakleaf This community occurs on the flood plains; and Arcadia. In most cases the aspect is adjacent to the dense forest belt that occurs towards the middle of the adjacent water sys- on the banks of the main rivers in the area. tem, the slope is usually not to steep (2 -5º) Soils of the Oakleaf form is the main soil and the soil surface is normally free of rocks. type found in this community, with Arcadia Tall Combretum imberbe (Species group G, and Valsrivier soils occurring on a more spo- Table 1), Lonchocarpus capassa (Species radic basis. The aspect and extremely grad- group P, Table 1) and to a lesser extent, Aca- ual slope are mostly in a northerly direction cia tortilis (Species group K, Table 1) trees as this is the general flow direction of the and a high abundance of the shrub Abutilon Limpopo River in respect to this community.

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Rockiness of the soil surface is 1–6 % and 1) and Acacia tortilis (Species group K, the rocks and/or pebbles are often of a cal- Table 1) as well as the grass species careous origin. This area is frequented by Urochloa mosambicensis (Species group K, elephants and as a result is heavily utilised. Table 1). Other species distinguishing this sub-community from the Cordia monoica The diagnostic plant species of this commu- Sub-community (2.2) is the woody Acacia nity are found in Species group I (Table 1) and include the woody species Hyphaene nigrescens (Species group J, Table 1), the petersiana and the forb Trianthema trique- grass Panicum maximum (Species group P, tra. Other species with high cover abun- Table 1) and the annual forb Tribulus zeyheri dance values are Acacia tortilis, Salvadora subsp. zeyheri (Species group J, Table 1). australis (Species group K, Table 1) and The tree layer has an average height of 5 m Grewia bicolor (Species group O, Table 1) (in some cases as high as 9 m) and the crown from the woody component as well as the cover varies between 10 % and 55 %. The grasses Enneapogon cenchroides, Urochloa shrub layer on the other hand enjoys a crown mosambicensis (Species group K, Table 1) cover of between 36 % and 63 % and an and Setaria verticillata (Species group P, average height of 1.7 m. The herbaceous Table 1). layer has an average height of 0.5 m and cov- The tree layer of this community covers ers 38 % to 80 % of the sub-community area. 10–60 % of the area. The height of the tree layer varies between 3 m and 9 m. The 2.2 Cordia monoica Sub-community height of the shrub layer varies between 1.2 m and 2.0 m and the crown cover The habitat of this sub-community is in between 10 % and 60 %. Grasses dominate many ways similar to that of the Ximenia the herbaceous layer. This layer has an aver- americana - Flueggea virosa Sub-communi- age height of 0.5 m and a crown cover of ty (2.1). The only difference being that this between 37 % and 82 %. sub-community has established under drier conditions and mainly occurs on somewhat This community is divided into two sub- higher lying areas further away from the communities based on differences in vegeta- Limpopo River. The soils are also of the tion structure. In the Ximenia americana - Oakleaf and Valsrivier forms with less Flueggea virosa Sub-community (2.1) the occurrences of the Arcadia soil form. shrub layer is dominant and in the Cordia monoica Sub-community (2.2) the tree layer There are no diagnostic species, which is dominant. define this sub-community. The dominant species are Acacia tortilis and Urochloa mosambicensis (Species group K, Table 1) 2.1 Ximenia americana-Flueggea virosa with Hyphaene petersiana (Species group I, Sub-community Table 1) not as dominant as in the Ximenia This sub-community covers the largest part americana - Flueggea virosa Sub-communi- of the Hyphaene petersiana - Acacia tortilis ty (3.1). Species that further differentiate this Community (2). The dominant soil forms are sub-community are the woody species Cor- Oakleaf and Valsrivier with high silt content dia monoica (Species group I, Table 1) and and a small number of the Arcadia soil form, the absence of the tree species Lonchocarpus which is a duplex soil with high clay content. capassa (Species group P, Table 1) and the grasses Panicum deustum (Species group O, Diagnostic species of this sub-community Table 1) and P. maximum (Species group P, are found in Species group J (Table 1) and Table 1). include the woody species Flueggea virosa subsp. virosa and Ximenia americana. The In the Cordia monoica Sub-community (2.2) dominant species are the tree species the tree layer dominates the shrub layer. The Hyphaene petersiana (Species group I, Table tree layer reaches an average height of 5 m

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and a crown cover of between 30 % and has an average height of 1.6 m and covers 60 % while the crown cover of the shrub between 18 % and 68 % of the total commu- layer varies between 10 % and 45 % and nity area. The herbaceous layer reaches an reach an average height of 1.6 m. The herba- average height of 0.7 m and a crown cover of ceous layer covers between 37 % and 82 % between 8 % and 90 %. of the sub-community and has an average height of 0.4 m. This community is divided into two sub- communities: 3. Croton megalobotrys-Combretum microphyllum Community 3.1 Cenchrus ciliaris-Faidherbia albida This riverine community is mainly situated Sub-community. on the banks of the Limpopo River and to a lesser extent on the floodplain. It is charac- This sub-community is found on the river- terised by tall trees and sometimes a dense bank of the Ia land type. The dominant soil undergrowth of shrubs, climbers and various form is Valsrivier and to a lesser extent the other forbs and grasses. The utilisation by Oakleaf soil form. The habitat differs from the Tuli elephants is of a big, but not totally the Acacia schweinfurthii – Maytenus sene- destructive measure. The elephants trample galensis Sub-community (3.2) because of it the area as they frequent it, mainly for shel- being more associated with low-lying areas ter at night. The soils of this unit consist of that are frequently flooded during the annual Oakleaf and Valsrivier soil forms. The aspect flooding of the Limpopo River, and its side is once more chiefly in a northerly direction branches. In some areas a layer of alluvial and the slope varies between gradual slopes sand and flood-debris cover the soil surface (1-5 º), leading from the flood-plain unit to only to be disturbed and washed away during the river, and short steep inclines (10-20 º) the next flooding. leading to the river itself. The tree species Faidherbia albida, the grass The diagnostic species is found in Species species Cenchrus ciliaris and Bothriochloa group L (Table 1) and in this case it is the insculpta and the herbaceous species Datura woody species Croton megalobotrys, which sp. and Phragmites australis are diagnostic occurs in tree and shrub form. The woody to this sub-community (Species group M, species Croton megalobotrys (Species group Table 1). Tall, sometimes-dense trees domi- L, Table 1), the creeper Combretum micro- nate the vegetation of this sub-community, phyllum (Species group O, Table 1) and the of which Croton megalobotrys (Species grass species Panicum maximum (Species group L, Table 1) is by far the most domi- group P, Table 1) dominate the vegetation of nant. Other species, which distinguish this this community. Other species with high cover abundance values are the tree species sub-community from the Acacia schwein- Acacia xanthophloea (Species group R, furthii – Maytenus senegalensis Sub-com- Table 1) and the grass species Setaria verti- munity (3.2) through their absence or low cillata (Species group P, Table 1) and Pan- abundance, are the tree species Grewia icum schinzii (Species group O, Table 1). bicolor, Grewia flavescens (Species group The community is further characterised by O, Table 1) and Lonchocarpus capassa the absence of the species of Species groups (Species group P, Table 1) and the grass I and K (Table 1) as well as the herbaceous species Panicum deustum (Species group O, Amaranthus sp. (Species group R, Table 1). Table 1). The Croton megalobotrys - Combretum The tree layer covers between 58 % and microphyllum Community has a high tree 90 % of this community and reaches a height layer with the height of the trees varying of between 7.8 m and 17.0 m. The shrub between 7.8 m and 20.0 m and a crown cover layer has an average height of 1.5 m and a of between 50 % and 90 %. The shrub layer crown cover of between 18 % and 60 %. The

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herbaceous layer covers between 10 % and height of 0.8 m and a crown cover varying 80 % and has an average height of 0.5 m. between 8 % and 90 %. 4. Diplachne fusca - Acacia xanthophloea 3.2 Acacia schweinfurthii - Maytenus Community senegalensis Sub-community. The Diplachne fusca – Acacia xanthophloea The habitat of this sub-community is some- Community commonly occurs on heavy what drier than that of the Cenchrus ciliaris clayey duplex soils in non-perennial pans – Faidherbia albida Sub-community (3.1). It and wetlands in the Ia land type. Soil types is situated on the floodplain and the river- commonly found in these areas belong to the bank of the Ia land type on areas that are less Rensburg, Arcadia, Valsrivier and Sepane frequently flooded. The soil forms are basi- soil forms. The soil surface, which is cov- cally the same as in the Faidherbia albida – ered by cracks in the dry season, is mostly Acacia xanthophloea Sub-community (3.1) clear of rocks. Aspect and slope is of no great only with the Oakleaf soil form being more significance in this community. It can how- dominant than the Valsrivier soil form. ever be stressed that most of the wetland/pan systems in the area drain towards the Diagnostic species to the Acacia schwein- Limpopo River. The major degradation furthii – Maytenus senegalensis sub-commu- problems of this community lie outside the nity are found in Species group N (Table 1). current boundaries of the Vhemeb-Dongola This includes the rambling woody species National Park, where large areas of these Acacia schweinfurthii, and the tree species wetlands have been cleared for cultivation Xanthocercis zambesiaca, Maytenus sene- purposes. Large dams have also been built galensis and Phyllanthus reticulatus as well for irrigation purposes and large-scale fish as the creeper Cocculus hirsutus. Tall trees farming is also practiced in these dams. with undergrowth, which proves to be impenetrable in places, dominate the vegeta- The diagnostic species to this community are tion of this sub-community. Croton mega- found in Species group Q (Table 1). They are lobotrys (Species group L, Table 1) is less the grasses Diplachne fusca, Dinebra dominant in this sub-community and have retroflexa, Echinochloa pyramidalis and the lower cover abundance values than in the forbs Corbichonia decumbens and Abutilon Faidherbia albida – Acacia xanthophloea sonneratianum. Dominant species are the Sub-community (3.1). Species, which fur- woody species Acacia xanthophloea ther distinguish the Acacia schweinfurthii – (Species group R, Table 1) and the grass Maytenus senegalensis Sub-community Diplachne fusca (Species group Q, Table 1). (3.2) from the Cenchrus ciliaris-Faidherbia The Diplachne fusca – Acacia xanthophloea albida Sub-community (3.1), are the tree Community is further characterised by the species Grewia bicolor, Grewia flavescens absence of the species found in Species (Species group O, Table 3) and Lonchocar- groups O and P (Table 1), which occur in pus capassa (Species group P, Table 1). most of the other communities in this land type. The tree layer of this sub-community covers between 50 % and 88 % of the area and the The tree layer has an average height of 8.2 m trees reach a height of between 8.0 m and and a crown cover varying between 25 % 20.0 m. The shrub layer has more crown and 35 %. The shrub layer is poorly devel- cover in this sub-community than is the case oped with an average crown cover of only in the Cenchrus ciliaris – Faidherbia albida 3 % and an average height of 1.0 m. The Sub-community (3.1). The shrub layer cov- herbaceous layer on the other hand is well ers between 30 % and 63 % of the sub-com- developed with an average height of 1.3 m munity and reaches an average height of and a crown cover varying between 60 % 1.7 m. The herbaceous layer has an average and 90 %.

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Fig. 2. The relative positions of the communities and sub-communities along the first two axes of the ordination of the relevés sampled in the Vhembe-Dongola National Park on the Ia land type.

Ordination be higher than is the case further away from the river in the Salvadora australis – The distribution of the relevés of the Ia land Cucumis zeyheri Community (1) and the type indicates a distinct discontinuity Hyphaene petersiana – Acacia tortilis Com- between the four communities along ordination axis one of the scatter diagram (Fig. 2). munity (2). This latter community is found The gradient illustrated along the first ordi- on an area between the drier Salvadora aus- nation axis could be related to soil moisture tralis – Cucumis zeyheri Community (1) and and to a lesser extent clay content and soil the wetter Croton megalobotrys - Combre- depth . tum microphyllum Community (3). The Salvadora australis – Cucumis zeyheri Community (1) is associated with flood plain Concluding remarks areas on the outskirts of the riverine vegetation. On the scatter diagram (Fig. 2) it is Some of the vegetation types described in clear that the habitat of this community is the Ia land type are similar to plant commu- virtually opposite to that of the Acacia xan- nities previously described in other studies. thophloea - Diplachne fusca Community (4), The vegetation and habitat of the Salvadora with regard to the gradients stipulated along australis – Cucumis zeyheri Community (1) the first ordination axis. The Acacia xan- are similar to the Salvadora australis Veld thophloea - Diplachne fusca Community (4) described in a vegetation report of the area is found in and around pans and other wet- by the former South African Defence Force land systems in the Vhembe-Dongola (1986b), but different communities of river- National Park on soils that are waterlogged ine vegetation have not been described for a long period during the year. The Croton (South African Defence Force 1986 a,b). The megalobotrys - Combretum microphyllum Hyphaene petersiana –Acacia tortilis Com- Community (3) is found on the very edge of munity (2) and the Croton megalobotrys- the Limpopo River and its tributaries. In Combretum microphyllum Community (3) these parts the water table should certainly thus occurs in the same vegetation unit,

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which is referred to as Riverine vegetation in and the South African Defence Force (1986 the vegetation report of the South African a,b) show similarities with the habitat Defence Force (1986a,b). An Eragrostis Vlei descriptions of the different plant communi- Grass vegetation unit of which the habitat ties of the Ia land type in this study. and vegetation compares well with the Aca- As a result of land clearing by intensive irri- cia xanthophloea - Diplachne fusca Commu- gation farming practices, as well as over-util- nity (4) have also been described in the stud- isation by small and large livestock and ies completed by the South African Defence game (especially elephants), most communi- Force (1986 a,b) in the area proposed for the ties of the Ia land type are degraded. Over- Vhembe-Dongola National Park. utilisation and destruction caused by migra- The riverine vegetation is more accurately tory Tuli-elephants, from neighbouring described in the study of Timberlake & Botswana, is a large cause for concern. The Mapaure (1999). The Acacia/Faidherbia South African National Parks and the man- Woodland Type described by Timberlake & agement of the Vhembe-Dongola National Mapaure (1999) is further sub-divided into Park consider this in a serious light and a four sub-types namely the Faidherbia albida number of monitoring sites have been estab- Woodland, the Xanthocercis-Schotia Wood- lished. Another issue of concern observed in land, the Acacia xanthophloea Woodland the Ia land-type was the damage caused by and the Acacia tortilis Woodland. The Faid- elephants to large trees through the stripping herbia albida Woodland shows similarities of bark which will eventually lead to the with the Cenchrus ciliaris-Faidherbia albi- death of these trees. The trees mostly affect- da Sub-community (3.1) and the Xanthocer- ed include Acacia xanthophloea, Faidherbia cis-Scotia Woodland with the Acacia schwe- albida and Ficus sycomorus. infurthii – Maytenus senegalensis Sub-com- Plant communities described in this study munity (3.2), Both are sub-communities of and in other land types in the Vhembe-Don- the Croton megalobotrys-Combretum micro- gola National Park (Götze 2002) should phyllum Community (3). In a phytosociolog- eventually be used in the compilation of a ical synthesis of the Mopane Veld, Du vegetation map of the park that can be used Plessis (2001) described the Croton mega- in the delineation of management units and lobotrys-Colophospermum mopane vegeta- the establishment of management plans. tion type. This vegetation type and the Cro- ton megalobotrys-Combretum microphyllum Community (3) described in the current Acknowledgements study show similarities with respect to habitat and floristic composition. South African National Parks and the Peace Parks Foundation are thanked for technical and financial The Hyphaene petersiana–Acacia tortilis assistance and the South African Defence Force for Community (2) is comparable with the providing soil and vegetation maps of the area. This Hyphaene Shrubland and to a lesser extent to study forms part of a MSc.-dissertation at the the Acacia tortilis Woodland described by Potchefstroom University for Christian Higher Edu- Timberlake & Mapaure (1999). The dry pan cation. and wetland areas in which the Acacia xanthophloea - Diplachne fusca Community (4) occurs was not specifically described by References Timberlake & Mapaure (1999). It does, how- ACOCKS, J.P.H. 1988. Veld Types of South Africa, ever, to a certain degree, resemble the Acacia 3rd ed. Memoirs of the Botanical Survey of xanthophloea Woodland described by these South Africa 57: 1-146. researchers. ARNOLD, T.H. & B.C. DE WET. 1993. Plants of Southern Africa: names and distribution. Mem- The habitats described in different vegeta- oirs of the Botanical Survey of South Africa 62: tion types by Timberlake & Mapaure (1999) 1-825.

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