Floristic analysis of the Mountain Zebra National Park, Eastern Cape

As part of a larger project to assess the vegetation dynamics and conservation potential of the enlarged Mountain Zebra National Park, a checklist was produced to determine the plant species richness for this area. Six hundred and eighty species, represented by 333 genera and 87 families were identified. One hundred and eighty species belong to the Monocotyledoneae and 479 species to the Dicotyledoneae. By far the largest families are the Asteraceae with 129 and the Poaceae with 82 species. Thirteen Red Data species were recorded. A number of fynbos elements were encountered, the most noteworthy being two families endemic to the Cape Floristic Region, the Penaeaceae and Grubbiaceae. A very high species to square kilometre ratio of 5.05 supports the area’s rich floristic composition.


Introduction
The Mountain Zebra National Park (MZNP) was proclaimed a protected area in 1937 (Wahl & Naude 1996).It is situated in a zone transitional between the Nama Karoo Biome in the west and the Grassland Biome in the east (Hoffman 1998), but classified as being part of the Nama Karoo (Low & Rebelo 1998).The primary objective for this park is to conserve a viable, genetically uncontaminated, representative population of the Cape Mountain Zebra Equus zebra zebra.Secondary objectives are the conservation of a representative spectrum of the typical faunal elements under natural conditions, and secodly, vegetation types that are unique to this region (Van der Walt 1980).
In 1996, a process was initiated to incorporate adjacent farmland into the park.This will increase the park's area substantially, from the original 6 536 ha to approximately 18 000 ha (Brown & Bezuidenhout 2000), once current negotiations have been completed.Two extensive vegetation studies have been conducted: a phytosociological reconnaissance of the original MZNP by Van der Walt (1980); and a phytosociological account, describing and mapping the plant communities of the newly acquired De Rust section of the MZNP (Brown & Bezuidenhout 2000).As part of a larger and long-term research project, the latter study aimed at assessing the habitat suitability to establish large herbivores on the new farms.
No annotated comprehensive plant species list of MZNP is available.Surveys of the floristic diversity and species richness of an area are fundamental to any wildlife management programme and conservation policy.A floristic database of an area serves as a permanent reference to establish site uniqueness and species richness, monitoring changes in species occurrence and the distribution of endemic and Red Data species.This study set out to provide a floristic checklist for the MZNP including the newly acquired farms De Rust, Doornhoek and Welgedacht.

Topography
The southern parts of the MZNP are characterised by mountainous terrain with steepsided drainage lines from mountaintops (Bankberg 1 927 m and Rooiplaat 1 360 m above sea level.The Wilgerboom River traverses the central valley of the southern section and exits the park at 1 200 m a.s.l. to the north.The northwest (De Rust) is dominated by Salpeterkop (1 514 m a.s.l.), a typical mesa of the Karoo landscape with a steep gradient.This gives way to a mid-slope plateau, footslopes and an undulating plain with seasonally dry river beds towards the eastern and central part of the park, at approximately 1 000 m above sea level.The heterogeneous vegetation is co-dominated by dwarf shrubs and grasses, with patches of incipient forest in drainage lines and the extensive grass plain of Rooiplaat.

Climate
The mean rainfall for the area is 382 mm per annum , ranging from the highest rainfall of 651 mm (1977) to the lowest rainfall of 153 mm (1966), as measured at the MZNP weather station.The rainy season occurs mostly in late summer and autumn, and the winters are relatively dry.Mean monthly minimum and maximum temperatures vary from 6-28 ºC in summer (September-March) and from 0-20 ºC during winter (April-August) (Brown & Bezuidenhout 2000).Extreme temperatures range from -7 ºC to 37 ºC and severe frost is likely during the period May-October (Van der Walt 1980).Van der Walt (1980), further states that the vegetation is subjected to continuous climatic variables due to the influence of an arid climate from the east and a more moderate climate from the west.The southern mountainous peaks are exposed to increased cloud cover, extreme temperature and moisture regimes, with local climate variations resulting in a number of microhabitats.Bankberg forms a barrier to cold winter fronts, thus a warmer climate is experienced in the sheltered val-ley below whilst regular snowfall occurs on higher lying areas (Van der Walt 1980).

Geology and soil
Mudstone, sandstone and shale of the Beaufort Group of the Karoo Supergroup dominate the MZNP (Keyzer 1997).These mudstones and shales are relatively unstable and subject to mechanical and chemical weathering.The material derived from these processes is usually rich in clay and salts.In addition, the MZNP sediments have been penetrated on a large scale by Post-Karoo dolerite intrusions (Keyzer 1997), forming large sheets and a number of dykes.The southern part of the park is characterised by dolerite outcrops that are remnants of the former sheet, of which the resistant Bankberg is a prominent feature (Van der Walt 1980).Highly fertile clayey soils are also derived from the fairly resistant doleritic parent material.Calcareous bedrock (limestone) lines some river courses (pers.obs.), formed by chemical precipitation from sandstone or mudstone and found in tributaries of the Wilgerboom River from Kranskop peak (Brown & Bezuidenhout 2000).

Methods
Plant collections were undertaken over a two-year period during 1999 and 2000.The areas covered included De Rust, Doornhoek, Welgedacht and the following areas within the former MZNP: Rooiplaat, Kranskop, the top of Bankberg and along the kloofs down to Weltevrede and Fonteinkloof.Collection sites were selected randomly within the extensive area according to topography and plant phenology, ensuring that all variations in habitat were considered and sampled.All specimens were labelled, pressed and dried, then identified by the Selmar Schönland Herbarium in Grahamstown and form part of the collection of the Kimberley South African National Parks Herbarium.Selected duplicates are kept at the Selmar Schönland Herbarium and Technikon SA.
The final species list was compiled from various sources: Pond and Beesley's collection, van der Walt (1980) and a species list supplied by PRECIS (National Herbarium Pretoria Computerised Infor-mation System) for the MZNP.Plant names were entered into and consolidated by SaS (2002), a database for the Cape and Karoo floras.While Arnold & De Wet (1993) served as a basis for nomenclature and arrangement, SaS introduced the latest taxonomic changes and appropriate author updates.Only identified species were listed.Red Data status, also produced by SaS, follows Hilton-Taylor (1996).Introduced species were included and are followed by an asterisk (*).

Results
The MZNP plant species list totals 680 species, which represent 333 genera and 87 families.Flowering plants are represented by Monocotyledoneae with 180 species in 14 families (16 % of the total number of families) and Dicotyledoneae with 479 species in 62 families (71 %).The Bryophytes with seven families (8 %) and the Pteridophytes with four families (5 %) represent non-flowering plants (Fig. 2).The complete species list, separated into the different plant divisions, sorted by family and indicating the species' Red Data status where applicable, appears as Appendix 1.This study added 100 new species to previous records for the MZNP.Introduced species were included in all floristic calculations.
The MZNP flora is represented by 87 families, as reflected in Table 1.Eight families dominate the MZNP flora.By far the two largest families are the Asteraceae with 129 species, reflecting 19 % of the total flora and the Poaceae with 82 species (12 %).These are followed by much smaller, yet significant families, represented by the Fabaceae with 35 species (5.2 %), Scrophulariaceae 31 (4.6 %), Mesembryanthemaceae 22 (3.2 %), Geraniaceae 21 (3.1 %), Cyperaceae 18 (2.6 %) and the Crassulaceae also with 18 species and 2.6 % of the species total (Fig. 3).These eight fam-ilies represent 52.3 % of the MZNP flora, while the other families reflect the remaining 47.7 %.
Twenty-nine genera are represented by five or more species.These are listed in Table 2.
Thirteen Red Data species were found, representing 1.9 % of the MZNP flora (Fig. 4).Red Data species and the categorisation are indicated in the species list (Appendix 1).Symbols and terms used in Appendix 1:  There is a gradient of species replacement within the dry Karoo from winter to summer rainfall.For example, the Mesembryanthemaceae, represented by 3.2 % in the MZNP, ranked amongst the dominant families.However, the Mesembryanthemaeceae decline from the west (the centre of endemism and species radiation) to the east, where they are replaced by other groups, such as the Crassulaceae, which make up 2.6 % of the MZNP flora.
Of the 87 plant families, 71 % are Dicotyledoneae and 16 % Monocotyledoneae (Fig. 2).Monocoteae are generally herbaceous, whereas dicots are woody or herbaceous and in general much more diverse in habitat (Jones & Luchsinger, 1987), suggesting that they are also accustomed to greater edaphic and climatic variations.A ratio of 3.8 dicots to 1 monocot species for the MZNP is slightly higher than that of the Cape floristic region and the average for floras across the world at 3: The floristic region of southern Africa (Botswana, Lesotho, Namibia, South Africa and Swaziland) has about 20 400 native vascular plant species in an area of 2 674 000 km².South Africa alone may have some 18 500 species of these, considered a particularly rich and diverse flora for a predominantly temperate region.The Cape Floristic Region (CFR) at 90 000 km², with 9 000 species, is striking by world standards (Goldblatt & Manning 2000).At a smaller scale, however, the MZNP study area (13 464 ha of the entire 18 000 ha) and other Karoo floras were compared in Table 3 ( Zietsman & Bezuidenhout 1999;Zietsman et al. 1992;Van Rooyen & Bezuidenhout 1997;SaS 2002).
Plant species richness at 5.05 species per 100 ha is considerably higher when compared to the other parks and reserves.Thus the MZNP displays a rich floristic composition, a result of extreme habitat and substrate diversity, ranging from sandstones to shales and dolerite dykes to calcareous bedrock with extensive grass plains, shrublands, high altitude seeps and riverine thicket.Microclimatic conditions play an important role in the germination and establishment of seedlings of karoo plants (Roux & Theron 1987).
Geophytes seem best adapted to a seasonally extreme climate with a wet winter and dry summer, in semi-arid conditions (Goldblatt & Manning 2000).This is evident in the Succulent Karoo, where geophytes are most abundant, both in terms of species richness and cover (Hoffman & Cowling 1987).
There is a high incidence of geophytes in the MZNP (8 % of the total flora) represented by the Alliaceae, Amaryllidaceae, Asphodelaceae, Hyacinthaceae, Hypoxydaceae and Iridaceae.Despite the fact that most of the park experiences a semi-arid climate with erratic rainfall that occurs mainly in summer, Hoffman & Cowling (1987) remark that geophytes are very conspicuous in the eastern Karoo.

Conclusion
The

Figure 1 .
Figure 1.Location of the study area.

Fig. 3 .
Fig. 3. Dominant plant families reflecting the number of species and percentage of the total flora

Fig. 4 .
Fig. 4. Number and status of Red Data species according to Hilton-Taylor (1996).
(1980), also found the number of rare and endangered species for the Nama Karoo biome to be low.A unique feature of MZNP is the occurrence of two families that are endemic to fynbos, i.e., the Penaeaceae and Grubbiaceae.Whilst Penaea cneorum has been recorded from the Kogelberg and Riviersonderend Mountains to Port Elizabeth, Penaea acutifolia is a new record, previously only recorded from the Outeniqua Mountains to George.Also, Grubbia rosmarinifolia, whose current range of distribution is restricted from the Koue Bokkeveld to the Tsitsikamma Mountains(Goldblatt & Manning 2000), is a fynbos element and has been recorded in the park.
1 (Goldblatt &  Manning 2000).Although less diverse in habitat, monocot families have specialised to co-dominate in most floras of the sub-region.Graminoids, such as Restionaceae, Poaceae and Cyperaceae are respectively ranked as the 8 th , 11 th and 12 th largest families of the Cape flora(Goldblatt & Manning 2000).Whilst the Restionaceae depend on winter rainfall and are less prominent east of the Cape Floral Kingdom, the Poaceae emerge in the more arid summer rainfall areas and rate as the 2 nd largest family in the MZNP (12 % of the total flora).Hoffman & Cowling (1987)noted that an overall increase in grass cover from west to east correlated with an overall increase in rainfall and a decline in winter rainfall.The Cyperaceae (generally associated with impoverished sandstone soils of the Cape mountain ranges byGoldblatt & Manning, (2000)amount to 2.6 % of the flora (18 species) in the Mountain Zebra National Park.g., Augrabies Falls National Park with 0.6 %, Karoo National Park 2.2 %, Karoo Nature Reserve 1.6 %, Tankwa Karoo National Park 2.4 %, Goegap Nature Reserve 2.4 %.Richtersveld National Park has a contrasting high of 6 % (Sas 2002).Hall et al.Apart from the two records above, a number of fynbos elements were found in the park.According to Low (A.B.Low, P O Box 370, Rondebosch, 7701) (pers.comm.2000),locally occurring genera, such as Eriocephalus, Elytropappus, Euryops, Maytenus and Diospyros are normally associated with Renosterveld (on shale), while Passerina, Erica and Gnidia as well as the Amaryllidaceae are also associated with Fynbos.Passerina and Dodonaea spp.are known to link summer and winter rainfall areas.In addition, arid Fynbos is normally characterised by the absence of Ericaceae, and yet, here it is found in the more arid Karoo.To the same extent, Leucosidea sericea that commonly occurs in Drakensberg streams has also been recorded in the Mountain Zebra National Park.