Dune Vegetation and Coastal Thicket Plant Communities in Threatened Limestone Fynbos of Andrew’S Field and Tsaba-Tsaba Nature Reserve, Struisbaai, Western Cape

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Dune vegetation and coastal thicket plant communities in threatened limestone fynbos of Andrew’s Field and Tsaba-Tsaba Nature Reserve, Struisbaai, Western Cape

M.M. ZIETSMAN and G.J. BREDENKAMP

Zietsman, M.M. and G.J. Bredenkamp. 2006. Dune vegetation and coastal thicket plant communities in threatened Limestone Fynbos of Andrew’s Field and Tsaba-Tsaba Nature Reserve, Struisbaai, Western Cape. Koedoe 49(1): 33–47. Pretoria. ISSN 0075- 6458. The coastal thicket and dune vegetation of Andrew’s Field and Tsaba-Tsaba Nature Reserve was classified using Braun-Blanquet procedures and TWINSPAN. The vegetation was sampled using 74 randomly stratified sample plots. The floristic composition, cover-abundance of each species, and several environmental variables were recorded in each sample plot. Six plant communities were identified, namely, Rhus glauca - Euclea racemosa low to tall closed thicket community; Chrysanthemoides monilifera - Solanum africanum low closed dune shrub community; Chrysanthemoides monilifera - Ehrharta villosa var. maxima low to high closed dune shrub community; Ehrharta villosa var. maxima low to short closed dune grassland community; Ammophila arenaria low to short closed dune grassland community; and Arcthotheca populifolia - Thinopyrum distichum low to short open beach community. These were subdivided into eight sub- communities and four variants. All communities, sub-communities and variants were described and ecologically interpreted. The distribution of the communities, sub-communities and variants can mainly be ascribed to differences in landform, rockiness of the soil surface the degree of protection / exposure of the vegetation to the dominating winds of the area. Key words: coastal thicket, conservation area, endemic plants, Limestone Fynbos, phy- tosociology, plant communities, TWINSPAN, Western Cape

M.M. Zietsman and G.J. Bredenkamp, African Vegetation and Plant Diversity Research Centre, Department of Botany, University of Pretoria, Pretoria, 0002 Republic of South Africa. Introduction level of organisation (Bredenkamp & Brown 2001). Studying the vegetation of an area A sound knowledge of the ecology of the area is an essential prerequisite for the estab- allows the identification, description and lishment of efficient wildlife management classification of plant communities. On the programmes and compilation of conservation basis of the plant communities as vegetation policies for any area (Edwards 1972). Vege- units, management units can be delineated. tation science has been applied in the fields Vegetation studies also allow the identifica- of nature conservation for years, but recent tion of ecologically sensitive areas, bush developments relate to the application of encroached areas or areas infested with alien plant ecological knowledge to environmental plants, degraded areas, habitats of rare or management (Scheepers 1983). Bredenkamp endangered plant species, and habitats of & Brown (2001) emphasise the use of plant specific animals. communities as a reliable basis for any eco- The Andrew’s Field and Tsaba-Tsaba logical planning and management. Reserve is situated in the Bredasdorp/Rivers- To obtain knowledge of the ecology of the dale Centre of Endemism (Cowling 1992). study area, a study of the vegetation of the This centre of endemism refers to a well- area should be made at the plant community defined group of plants, confined to the lime-

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stone of the Bredasdorp Formation and asso- namely Strandveld and Waenhuiskrans for- ciated colluvial deposits (Heydenrych 1994). mations are found in the study area (Malan et According to Hilton-Taylor & Le Roux al. 1994). Beach and terrace deposits, not (1989) Limestone Fynbos is one of the most formally named as a formation, but forming threatened vegetation types in the Cape part of the Bredasdorp Group, are found in Floristic Region. Factors threatening Lime- the form of roll-stones on the coastal beach stone Fynbos vegetation include alien plants (Malan et al. 1994). Previous changes in sea (considered the biggest problem), land clear- level resulted in the presence of roll-stones ing, resort development, inappropriate fire of Table Mountain Sandstone. management and over-harvesting of flowers The Strandveld Formation is restricted to the (Heydenrych 1994). coast. It consists of white to light-grey dune Thicket encroachment into the adjacent sands with a high percentage shell frag- Limestone Fynbos and Renosterveld is ments. Partial cementing of sands is a result therefore a serious threat to the species-rich of the high calcium carbonate content in the Fynbos with many endemic and red data sand. The lithology of this formation is species. The species richness of coastal described as white dune sand, strand sand thicket in the reserve is very low compared with finely divided shell and alluvial stones to those of the adjacent Limestone Fynbos (Malan et al. 1994). and Renosterveld communities (Zietsman & The Waenhuiskrans Formation forms out- Bredenkamp in press) and the true thicket crops adjacent to the current coastline. The species like Rhus glauca and Euclea race- Waenhuiskrans stratiotype is 12.4 m deep, is mosa are neither rare nor endemic. Regard- locally overlain with 1 m thick calcretes and ing the importance of the conservation of consists of medium-grained cross-layered Limestone Fynbos in areas where the thicket calcarenite with well-rounded quartz and a communities occur, the effective manage- few glauconite grains. Large-scale aeolic ment of the area becomes all the more cross-layers are characteristic of the unit. important, and fully justifies a detailed vege- The lithology of this formation is described tation study of the coastal thicket. as partially calcified dune sand (Malan et al. 1994).

Study area The study area is situated on the Agulhas Plain, a coastal lowland. The majority of the The reserve is situated in the Bredasdorp dis- area falls below the 10 m contour (Jefferey trict, Western Cape, between Struisbaai 1996). Coastal dunes and dune plains are North in the south and De Mond State Forest typical in this area, with the highest point on in the north. It is bordered in the west by the a ridge 31 m above sea level. Bredasdorp/Struisbaai road, and in the south by the coastline. The study area is situated The soil can be described as shallow sandy close to the coastal town of Struisbaai. The soil, overlying limestone, or shallow to deep Andrew’s Field (129 ha) and Tsaba-Tsaba sandy soil, overlying clay, silt and gravel. Nature Reserve is approximately 979 ha in Four different soil forms have been distin- extent. Approximately one third of the study guished in the area (MacVicar 1991): area consists of the coastal vegetation, which - Coega: Orthic A on hard bank carbonate is dealt with in this report. The remainder of horizon; family Marydale: lime containing A-horizon. This soil form is found on the the study area consists of inland plains and limestone hills and shallow-soil limestone hills, described by Zietsman & Bredenkamp plain. (in press). - Immerpan: Melanic A on hard bank car- The dominant substrate in the study area is bonate horizon; family Kalkpan: lime con- the Bredasdorp Group (Malan et al. 1994). taining A-horizon. This soil form is found Two formations of the Bredasdorp Group on the proteoid dominated limestone plain

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A = Altitude, B = Mean Annual Temperature, C = Mean Annual Rainfall, D = Mean Daily Minimum (Coldest Month), E = Mean Daily Maximum (Hottest Month) Fig. 1. A Walter climatic diagram for Andrew’s Field and Tsaba-Tsaba Nature Reserve.

where the soil is deep. The study area is situated in the transitional - Brandvlei: Orthic A on soft carbonate zone between the winter-rainfall region in horizon; family Kolke: signs of wetness in the west and the non-seasonal rainfall region carbonate horizon. The marsh area is char- in the east (Mustart et al. 1997). The south acterised by this soil form. coast has a warm temperate climate with all- - Namib: Orthic A on regic sand; family seasons and bimodal equinoctial rainfall Beachwood: containing lime within 1500 (Strydom 1992). The average annual precip- mm from soil surface. This soil form is itation of the area is 444 mm. Precipitation is found on the dune plain and the deep-sand mostly rain, but it also occurs in the form of plains. fog. The maximum precipitation is in June, and the minimum during February and According to Tinley (1985) two distinct sand December. According to Heydorn & Tinley characteristics occur in dune fields. Bare (1980) the study area is situated in a low dune sands, yellow in colour, absorbs all rain rainfall region, within an arid belt protruding and consequently there is no surface runoff. into the interior from the coast. The low rain- Grey sands, stained by humus and covered fall appears to be the result of cold inshore with woody vegetation, have a water repel- waters that inhibit shoreline rains. A Walter lent layer near the surface, beneath the litter, climatic diagram was compiled (Fig. 1) from causing a massive surface runoff when data obtained from the Agulhas weather sta- heavy rains follow a dry period (Tinley tion. 1985). The average annual maximum and minimum The main factors affecting the climate are temperatures for the area are 6 ºC and 13.3 ºC the contrasting sea surface temperatures of respectively. The maximum temperature for the two major ocean currents and the inshore the area was 36.1 ºC, obtained in February. circulation (Tinley 1985). According to the The minimum temperature for the area is geographical division of Heydorn & Tinley 3.9 ºC, obtained in June (Zietsman & Bre- (1980), the reserve is situated on the south denkamp in press). coast, which is a transitional zone between The wind along the south coast is bidirec- tropical and temperate waters. tional. Southeasterly winds alternate with

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northwesterly and southwesterly winds Sub-community (Heydorn & Tinley 1980). 1.2.1 Olea exasperata - Euclea racemosa Short to High Closed Thicket Variant 1.2.2 Carissa bispinosa - Euclea Methods racemosa short to Tall Closed Thicket Variant Relevés were compiled in 74 stratified sample plots, 1.3 Acmadenia obtusata - Euclea racemosa placed in relatively homogeneous areas, representa- Short to Tall Closed Thicket Sub- tive of particular plant communities that occur in a community mosaic distribution pattern. A plot size of 10 m² was 1.4 Helichrysum dasyanthum - Euclea used, and considered as large enough to ensure that racemosa Low to Short Closed Thicket all species of regular occurrence in the stand are pre- Sub-community sent in the sample plot. Sample plots were placed in 1.5 Acacia cyclops - Euclea racemosa High such a way as to ensure that each plot adequately to Tall Closed Thicket Sub-community 1.6 Thamnocortus insignis - Euclea racemosa represents the structure of the particular vegetation High to Tall Closed Thicket Sub- (Werger 1974). A list of plant species found in each community sample plot was compiled. The cover-abundance of 1.6.1 Elytropappus rhinocerotus - each species in the sample plot was assessed, using Euclea racemosa Short to Tall the Braun-Blanquet cover-abundance scale (Werger Closed Thicket Variant 1974). Cover of the height classes of the different 1.6.2 Leucadendron coniferum - Euclea strata (Edwards 1983) was estimated and the vegeta- racemosa High to Tall Closed tion was structurally classified according to the Thicket Variant Edwards (1983) structural classification system. The 2. Chrysanthemoides monilifera - Solanum africanum following habitat characteristics were recorded in Low Closed Dune Shrub Community each sample plot: altitude, topographical position, exposure to wind (seaward or towards the land), 3. Chrysanthemoides monilifera - Ehrharta villosa slope angle, slope direction, geology, soil, percent- var. maxima Low to High Closed Dune Shrub age rock cover and biotic influence. Six main differ- Community ent habitat types are found in the study area, namely 3.1 Chrysanthemoides monilifera - Rhus crenata Short to High Dune Shrub Sub- dune plain, Renosterveld plain, limestone plain, community limestone hills, dunes and beach. These were record- 3.2 Chrysanthemoides monilifera - Morella ed in each sample plot. cordifolia Low to Short Closed Shrub To obtain a first approximation of the plant commu- Sub-community nities of the area, relevés were classified using 4. Ehrharta villosa var. maxima Low to Short TWINSPAN (Hill 1979), and these results were then Closed Dune Grassland Community refined by application of the classical Braun- Blanquet methodology (Behr & Bredenkamp 1988). 5. Ammophila arenaria Low to Short Closed Dune Grassland Community

6. Arcthotheca populifolia - Thinopyrum distichum Results Low to Short Open Beach Community Classification The cover and height of various strata of the The results obtained from the classification main plant communities are given in Table 2. are presented in a phytosociological table The hierarchical classification and associat- (Table 1). In naming the plant communities, ed environmental interpretation of the plant diagnostic and/or dominant species were communities is given in Fig. 2. The commu- used in combination with the Edwards nity numbers in Fig. 2 correspond with the (1983) structural classification. plant community numbers used in the descriptions in the text. 1. Rhus glauca - Euclea racemosa Low to Tall Closed Thicket Community 1. Rhus glauca - Euclea racemosa Low to Tall Closed Thicket Community 1.1 Rhus lucida - Euclea racemosa Low to Short Closed Thicket Sub-community 1.2 Pterocelastrus tricuspidatus - Euclea The community is found close to the sea on racemosa Short to Tall Closed Thicket the dune plains, limestone plains, Renoster-

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Flat dune plain sandy shallow 1.1 limestone plain Deep limestone plains Dune plains peaks, foot-slopes of 1.2.1 Deep to flat limestone plains limestone hills Sandy footslopes, slopes and Flat limestone plains shoulders of limestone hills Peaks and shoulders of 1.2.2 limesone hills Dune plains Limestone plains Sheltered, steep Rhenoster plains north-facing slopes 1.3 Dune slopes of back-dune slopes and peaks of limestone hills Dune plain Deep sandy slopes and shoul- 1.4 ders of limestone hills Limestone plains

Acacia cyclops encroachment in 1.5 community 1

Rhenosterveld plain 1.6.1 Rhenosterveld plains Limestone hills, foot- slopes Limestone hills 1.6.2 foot-slopes

Very steep dry, warm 2 dune slopes Dune slopes sheltered from 3.1 Coastal dunes south-eastern wind and dune troughs Dune slopes parallel to 3.2 south-eastern wind

South-facing slopes, sparsely vegetated 4 dunes

Northern steep dry mid-slopes of 5 dunes

Beach and gravel plain 6 frontal dune slopes

Fig. 2. Hierarchical classification and associated environmental characteristics of the coastal thicket, dunes and strand of Andrew’s Field and Tsaba-Tsaba Nature Reserve.

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Table 1 Phytosociological table of coastal thicket, dunes and strand of Andrew's Field and Tsaba-Tsaba Nature Reserve zietsman.qxd 2006/04/1708:48PMPage39

Table 1 (continuerd) zietsman.qxd 2006/04/1708:48PMPage40

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veld plains, northern slope of back-dunes, 1.1 Rhus lucida - Euclea racemosa Low to and on the slopes and peaks of limestone Short Closed Thicket Sub-community hills. These areas have a low cover of small irregular white-grey limestone pebbles. This sub-community is found on the flat to undulating dune plain, Namib soil form and The Rhus glauca - Euclea racemosa short to limestone plain, Brandvlei and Coega soil tall closed thicket community consists of forms (Fig. 2). The vegetation forms scat- scattered, dense groups of broad-leaved tered groups of low to short broad-leaved shrubs. These groups have high shrubs near shrubs. the centre and lower shrubs near the Rhus lucida (Species Group B, Table 1) is periphery. The structure of the vegetation is the only diagnostic species for this sub-com- given in Table 2. The shrub layer is most munity. The shrubs Euclea racemosa, Rhus prominent, while restioid and grass layers glauca and Rhus laevigata var. laevigata for. cover 10 % or less. Forbs and sedges have a coangoa (Species Group A, Table 1) are the very low cover. dominants in this sub-community. The The shrubs Euclea racemosa, Rhus glauca shrubby Helichrysum dasyanthum (Species and Rhus laevigata (Species Group A, Group G) and Passerina paleacea (Species Table 1) are diagnostic and dominant in this Group I) are locally prominent in the sub- community. Chrysanthemoides monilifera community. and Metalasia muricata (Species Group Q) An average of only four species per relevé are also prominent in the community. was recorded in this sub-community. In the absence of fire, these thickets tend to encroach into adjacent threatened Limestone 1.2 Pterocelastrus tricuspidatus - Euclea Fynbos and Rhenosterveld communities racemosa Short to Tall Closed Thicket which have several endemic and Red Data Sub-community species (Cowling & Richardson 1995; Hey- The sub-community is found on the Namib denrych 1994; Zietsman & Bredenkamp in soil form on the dune plain and on the press). Immerpan and Coega soil forms on sandy Six sub-communities, two of which have foot-slopes and shoulders of limestone hills two variants, were identified: (Fig. 2).

Table 2 Percentage Cover (C ) (%) and Height (H)(m) of the strata of the main plant communities Community 1 2 3 4 5 6 Stratum C H C H C H C H C H C H Tall shrub 14 2.5 6 2.5 6 2.5 ------High shrub 20 1.5 5 1.5 10 1.5 - - 10 1 - - Short shrub 28 0.75 5 0.75 29 0.75 - - - - Low shrub 15 0.4 51 0.15 16 0.3 - - - - Forb 3 0.3 1 0.3 2 0.3 - - - - 10 0.5 Short restoid 4 0.75 - - 0.3 0.2 - - - - Low restoid 7.5 0.4 ------Sedge 1 0.15 - - 0.5 0.15 - - - - High grass - - - - 0.5 1.5 3.5 1.5 - - Short grass 0.5 0.5 0.6 0.75 2 0.75 25 0.75 44 0.7 5 0.5 Low grass 10 0.3 - - 2 0.3 15 0.3 - - 2 0.3

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The vegetation forms scattered groups of An average of 13 species per relevé was short to tall broad-leaved shrubs, with some recorded for this variant. lower shrubs at the periphery. Species Group C (Table 1) is diagnostic for 1.3 Acmadenia obtusata - Euclea racemosa Short to Tall Closed Thicket Sub-community this sub-community, with the shrubby trees Robsonodendron maritimum and Pterocelas- The sub-community is restricted to a small trus tricuspidatus dominant diagnostic patch close to the sea, in the central part of species. The shrubs Euclea racemosa, Rhus the reserve, on a steep (26° to 45°), sheltered glauca and Rhus laevigata var. laevigata for. northern slope of a back-dune. The soil is of coangoa (Species Group A), are also very the Namib form and no rocks are found here. prominent in the sub-community. Only a single relevé represents this sub-community. 1.2.1 Olea exasperata - Euclea racemosa Short to High Closed Thicket Variant The vegetation forms scattered groups of short to tall closed broad-leaved shrubs, with The variant occurs on the slopes and peaks some lower shrubs at the periphery. of the limestone hills, and on the sandy, Species Group F (Table 1) is diagnostic, with deep-soil limestone plains (Fig. 2). the shrub Acmadenia obtusata, the forbs Arctopus echinatus and Zaluzianskya villosa Species Group D (Table 1) is diagnostic, and the grass Festuca scabra, as diagnostic with Olea exasperata and Osyris compressa species. The shrubs Euclea racemosa prominent diagnostic species. (Species Group A), Otholobium bracteola- The diagnostic species of the community and tum (Species Group G), Rhus crenata sub-community, namely the shrubs Euclea (Species Group N) and Passerina rigida racemosa, Rhus glauca and Rhus laevigata (Species Group P) are dominant. var. laevigata for. coangoa (Species Group Eighteen species were recoded in the single A), Robsonodendron maritimum and Ptero- releve. celastrus tricuspidatus (Species Group C) are dominant in the variant. 1.4 Helichrysum dasyanthum - Euclea racemosa An average of 12 species per relevé was Low to Short Closed Thicket Sub-community recorded for this variant. This sub-community is widespread on the 1.2.2. Carissa bispinosa Short to Tall dune plain, Namib soil form, the sandy shal- Closed Thicket Variant low-soil limestone plain and sandy slopes of limestone hills, Immerpan and Coega soil This variant is restricted to the flat limestone forms (Fig. 2). plains and the shoulders and peaks of lime- The vegetation forms scattered groups of stone hills (Fig. 2). This soil is of the Immer- low to short broad-leaved shrubs, with some pan and Coega forms. high shrubs at the centre. Species Group E (Table 1) is diagnostic with Otholobium bracteolatum and Helichrysum the shrubs Carissa bispinosa and Sideroxy- dasyanthum (Species Group G, Table 1) are lon inerme the most prominent diagnostic the diagnostic species for this sub-communi- species. The shrubs Euclea racemosa, Rhus ty. The shrubs Euclea racemosa, and Rhus glauca (Species Group A), Robsonodendron laevigata var. laevigata for. coangoa maritimum and Pterocelastrus tricuspidatus (Species Group A) are dominant, while Rhus (Species Group C) are dominant whereas the glauca (Species Group A), Pterocelastrus alien shrub Acacia cyclops (Species Group H) tricuspidatus (Species Group C), Passerina is also locally prominent. paleacea (Species Group I), Chrysanthe-

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moides monilifera (Species Group Q) are 1.6.1 Elytropappus rhinocerotus Short to also locally prominent. Tall Closed Thicket Variant The sub-community contains an average of The variant is found at an altitude of 3 m on only six species per relevé. the Renosterveld plain, Brandvlei soil form (Fig. 2). 1.5 Acacia cyclops - Euclea racemosa High to Tall Closed Thicket Sub-community The vegetation scattered groups of short to tall broad-leaved shrubs, with some lower Locally the alien Acacia cyclops encroached shrubs at the periphery, as well as some high restioids. into the Rhus glauca - Euclea racemosa short to tall closed thicket community. The diagnostic species are listed in Species Group K (Table 1), which includes the Acacia cyclops, the shrubby tree Protea shrubs Elytropappus rhinocerotis, Leuca- obtusifolia, and the shrub Passerina galpinii dendron linifolium, Oedera uniflora, Lycium are the diagostic species for this sub-com- afrum, Rhus laevigata var. villosa, Aspara- munity (Species Group H, Table 1). Acacia gus lignosus, Euryops hebecarpus, and the cyclops and the shrubs Euclea racemosa, forbs Limonium scabrum var. scabrum, Her- Rhus glauca and Rhus laevigata var. laevi- mannia althaeifolia and Pelargonium gata for. coangoa (Species Group A), and myrrhifolium. The shrubs Euclea racemosa Metalasia muricata (Species Group Q) are and Rhus glauca (Species Group A) and the dominant in the sub-community. restioid Thamnochortus insignis (Species The sub-community contains an average of Group I) are dominant whereas the shrubs seven species per relevé. Helichrysum patulum, Passerina paleacea (Species Group I), Chrysanthemoides monil- ifer and Metalasia muricata (Species 1.6 Thamnochortus insignis - Euclea racemosa Group Q) are locally prominent. High toTall Closed Thicket Sub-community The variant has an average of 22 species per The sub-community is found on the Renos- relevé. terveld plain, Brandvlei soil form and on sandy foot-slopes of limestone hills, Namib 1.6.2 Leucadendron coniferum High to soil form (Fig. 2). Tall Closed Thicket Variant The vegetation forms scattered groups of The variant is found on the sandy foot-slopes high to tall broad-leaved shrubs, with some of limestone hills, Namib soil form (Fig. 2). low and short shrubs at the periphery. Low forbs and some high, low and short restioids The vegetation forms scattered groups of are also present in the sub-community. high to tall closed broad-leaved shrubs, with some low to short shrubs at the periphery, as Species Group I (Table 1) is diagnostic for well as some high and low restioids. this sub-community with the restioid Tham- nochortus insignis and the shrubs Helichry- A large number of species given in Species sum patulum, Passerina paleacea, Metalasia Group K (Table 1) are diagnostic for this densa the most prominent diagnostic variant, the most prominent being the shrubs species. The shrubs Euclea racemosa, Rhus Eriocephalus kingesii, Leucadendron conifer- glauca (Species Group A), Chrysanthemoides um, Protea susannae, Maytenus procum- monilifera and Metalasia muricata (Species bens, Agathosma serpyllacea, Agathosma Group Q), are also prominent in the sub- collina, Phylica stipularis, Trigogyne repens community. and Tephrosia capensis and the restioid Chondopetalum microcarpum. The shrubs Two variants are recognised within this sub- Euclea racemosa and Rhus glauca (Species community: Group A), and the restioid Thamnochortus

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insignis (Species Group I) are dominant, as well as some low forbs, and low and short while the shrubs Olea exasperata (Species grasses present (Table 2). Group D), Cassine peragua (Species Group The shrub Stoebe cinerea and the grass I), Solanum africanum (Species Group L), Ehrharta villosa var. maxima (Species Chrysanthemoides monilifera (Species Group M, Table 1), are diagnostic for the Group Q) are locally prominent. community and Chrysanthemoides monilif- The variant is rich in species and has an era (Species Group Q) is the dominant average of 43 species per relevé. species. The shrubs Solanum africanum (Species Group L), Stoebe cinerea (Species 2. Chrysanthemoides monilifera - Solanum Group M), Morella cordifolia (Species africanum Low Closed Shrub Dune Community Group O), Passerina rigida (Species Group P) and Metalasia muricata (Species Group The sparsely vegetated community is found Q) are locally prominent species. in the shifting sand dune area adjacent to the The community has an average of ten sea. It occurs in a mosaic distribution pattern species per relevé. with communities 3, 4 and 5. The community is situated at an altitude of 1–20 m, on steep gradients. This vegetation is restricted 3.1 Chrysanthemoides monilifera - Rhus crenata Short to High Dune Shrub Sub-community to the drier northerly mid-slopes of coastal dunes, facing inland (Fig. 2). The soil is of The sub-community is found on north-facing the Namib form and no rocks are present. coastal dune slopes with steep gradients of The vegetation consists of low prostrate 26°–45°, sheltered from the south-eastern shrubs, with a few short, high and tall shrubs wind carrying salt spray. No rocks are found also present. The low shrub stratum is promi- here (Fig. 2). nent with an average cover of 51 % (Table 2). The vegetation consists of short to high The low shrub Solanum africanum (Species shrubs, with a few tall shrubs. Low forbs, Group L, Table 1) is not only diagnostic but low restios, low sedges, and low, short and also dominant in the community. The shrub high grasses have low cover values. Chrysanthemoides monilifera (Species The shrub Rhus crenata (Species Group N, Group Q) is also locally prominent. Table 1) is the only diagnostic species. The community contains an average of only Passerina rigida (Species Group P), four species per relevé. Chrysanthemoides monilifera and Metalasia muricata (Species Group Q) are dominant 3. Chrysanthemoides monilifera - Ehrharta villosa whereas the shrubs Solanum africanum var. maxima Low to High Closed Dune Shrub (Species Group L), Stoebe cinerea (Species Community Group M), Morella cordifolia (Species Group O), and the grass Ehrharta villosa The community is found in the sparsely veg- var. maxima (Species Group M) are also etated shifting dune area adjacent to the sea, locally prominent in the sub-community. in a mosaic distribution pattern with communities 2, 4 and 5. It is also present in a mosa- The sub-community contains an average of ic distribution pattern with communities 2 12 species per relevé. and 4 in the more densely vegetated sand dune area at the seashore and directly behind 3.2 Chrysanthemoides monilifera - Morella to the shifting sand dune area (Fig. 2). No cordifolia Low to Short Closed Dune Shrub Sub-community rocks are present in this habitat and the soil is of the Namib form. The steep (16–>45°) southerly-facing mid- The vegetation consists of short and low slopes dunes where this sub-community shrubs, with some short, high and tall shrubs occurs are larger, more exposed areas than

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those where sub-community 3.1 occurs. The tribution pattern with communities 2, 3 and 4 vegetation is exposed to sea mist (Fig. 2). (Fig. 2). The leaf structure and orientation of the most dominant plant species, Morella cordifolia, The vegetation is low to short dune grass- enhances the ability of the plant to catch land. The shrub stratum has an average moisture from sea fog. height of 1 m and an average canopy cover of 10 % and the grass stratum has an average The vegetation consists of low to short height of 0.7 m and an average canopy cover shrubs, with some high and tall shrubs, as of 44 % (Table 2). well as some low forbs, low restios, low sedges, and low, short and high grass. The exotic grass Ammophila arenaria (Species Group R, Table 1) is the diagnostic The shrubs Morella cordifolia, Lessertia and dominant species in the community. frutescens (Species Group O, Table 1), are Other species present are Lessertia dominant diagnostic species, and Chrysan- frutescens and Senecio arenarius. themoides monilifera (Species Group Q is also dominant. The shrubs Stoebe cinerea The community contains an average of only (Species Group M), Passerina rigida three species per relevé. (Species Group P) and Metalasia muricata (Species Group Q), and the grass Ehrharta 6. Arctotheca populifolia - Thinopyrum distichum villosa var. maxima (Species Group M) are Short to Low Open Beach Community locally prominent. The community is situated on the beach and The sub-community contains an average of south-facing slopes of low fore dunes, direct- 11 species per relevé. ly adjacent to the sea, and also on gravel plains behind the low fore dunes (Fig. 2). 4. Ehrharta villosa var. maxima Low to Short Closed Dune Grassland Community There are no rocks on the beach and dunes and 30–50 % rock cover on the gravel plain. The community is found on steep, exposed The rocks on the gravel plain are mostly southern slopes of sparsely vegetated stable sandstone and quartzite roll-stones, deposit- sand dunes, or the more mobile shifting sand ed by the sea while the lea level was higher. dunes adjacent to the sea. (Fig. 2). No rocks are present in the Namib soil form. The vegetation consists of short to low open beach grassveld with low forbs (Table 2). The community is found in a mosaic distribution pattern with communities 2, 3 and 5 The forb Arctotheca populifolia and the and also in a mosaic distribution pattern with grass Thinopyrum distichum (Species Group community 6 in the coastal beach area, adja- S, Table 2) are diagnostic and are the only cent to the sea. species found in this community. The vegetation is low to short dune grass- The community contains an average of only land, with a few high grasses. (Table 2). two species per relevé. The grass Ehrharta villosa var. maxima (Species Group M, Table ) is the sole diag- Discussion nostic and dominant species in the community. No other species occur here. The use of TWINSPAN and the application of Braun-Blanquet procedures for refinement, 5. Ammophila arenaria Low to Short Closed Dune were successful to classify the plant commu- Grassland Community nities of this vegetation type. Six plant communities, with eight sub-communities and The community occurs on the steep, dry and four variants, were identified. The plant warm north-facing slopes of sparsely vege- communities could all be related to specific tated shifting sand dunes, in a mosaic dis- environmental conditions and are therefore

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floristically and ecologically distinguishable The presence of sub-community 1.5 (Acacia and interpretable. cyclops - Euclea racemosa High toTall Closed Thicket Sub-community) is a reason The thicket community (community 1) for concern. Acacia cyclops occurs scattered forms part of the Dune Thicket vegetation in various communities, fairly well distrib- type of the Thicket Biome (Low & Rebelo uted throughout Andrew’s Field and Tsaba- 1998), whereas the other communities form Tsaba Nature Reserve, but the larger stands part of the Fynbos Biome (Low & Rebelo). found locally represent sub-community 1.5. The thicket was mostly found in a mosaic All areas containing Acacia cyclops, should with the vegetation of the inland plains and be managed by implementing regular pre- hills (Zietsman & Bredenkamp in press). scribed burning, and alien-invasive plant The thicket community does not only differ control, ideally by means of the cut-and-burn from the Fynbos communities concerning method (Cowling 1992), but the current species composition and structure, but also woodcutting method (promoting job provi- in conservation importance. According to sion), can also be followed. The conserva- Low & Rebelo (1998) 14.49 % of Dune tion of Limestone and Renosterveld vegeta- Thicket is currently being conserved, as tion should be treated as a high priority. opposed to the 1.42 % of South and South- west Coast Renosterveld and the 13.84 % of Fire should be kept out of the dune area, Limestone Fynbos (Low & Rebelo 1998). because, according to Tinley (1985) fire might cause an increase in dune instability. According to Cowling & Richardson (1995), Fire should also be kept out of areas that are if fire could be excluded from Fynbos for a heavily infested with the Cape dune molerat. century or two, many of the landscapes According to Tinley (1985) fire would lead would become densely populated with just a to an undesired increase in burrowing by few species of thicket shrubs and trees. Cape dune molerats to obtain sufficient food Inland thicket development is therefore a (roots). Therefore, as extensive dune molerat feature of vegetation that has not been sub- burrowing is already a problem in some jected to fire for some time. The species rich- areas in the reserve, fire should be kept out ness of this thicket is very low compared to of those areas. Other areas should be burned those of Fynbos and Renosterveld (Zietsman using a 15-year block-burn cycle to avoid the & Bredenkamp in press) and the true thicket possible substitution of Limestone and species like Rhus glauca and Euclea race- Renosterveld vegetation by dense thickets. mosa, are neither rare nor endemic. The Limestone communities and the Renoster- A single Red Data species (Solanum veld community, within which the thicket africanum) is found quite abundantly in the patches are found, have high conservation dune area (communities 2 and 3). The pres- priority. Renosterveld has a very high con- ence of Limestone endemic species in the servation priority due to the small portion dune area can be explained by the fact that left, mainly because of agricultural land both the dune sands and the limestone soil clearing (Low & Rebelo 1998; Zietsman & are alkaline. The shifting sand dune area Bredenkamp in press). Limestone Fynbos is should be protected from disturbances, like one of the most threatened vegetation types trampling and vehicle tracks. Protection in the Cape Floristic Region (Hilton-Taylor from disturbances should also provide suffi- & Le Roux 1989). There are 110 plant cient protection to the Red Data and Lime- species endemic to limestone outcrops. stone endemic species. Limestone Fynbos also contains many Community 9 is dominated by Ammophila species that are classified as rare (Heyden- arenaria, an exotic grass which is an Euro- rych 1994). Thicket forming should be seen pean weed, commonly found on coastal as a threat to the natural Fynbos and Renos- dunes (Goldblatt & Manning 2000). terveld vegetation, and should not be encour- aged above the conservation of the other Although community 6 contains no rare or Fynbos and Renosterveld vegetation. endemic species, the vegetation unit should

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be protected due to its uniqueness, and due to southern Cape. Kirstenbosch: Botanical Society the fact that this gravel-plain is the breeding of South Africa. (Flora Conservation Committee site of the rare Damara Tern Sterna balae- report no. 94/1.) narum (Jeffery 1996). HILL, M.O. 1979. TWINSPAN: A Fortran program for arranging multivariate data in an ordered Andrew’s Field and Tsaba-Tsaba Nature two-way table by classification of the individuals Reserve is an area of great conservation sig- and attributes. New York: Cornell University. nificance. This area comprises an important HILTON-TAYLOR, C. & A. LE ROUX. 1989. Conserva- tion status of the Fynbos and Karoo biomes. Pp. part of the natural heritage found at the 202–233. In: HUNTLEY, B.J. (ed.). Biotic diver- southern tip of Africa, and should be protect- sity in Southern Africa: concepts and conserva- ed and conserved for future generations. The tion. Cape Town: Oxford University Press. resulting classification provides a useful HEYDORN, A.E.F. & K.L. TINLEY. 1980. Estuaries of tool, not only for the management of the the Cape, part 1: Synopsis of the Cape coast nat- plant communities of Andrew’s Field and ural features, dynamics & utilization. Stellen- Tsaba-Tsaba Nature Reserve, but also for bosch: Council for Scientific & Industrial Research, National Research Institute for similar vegetation areas, found in the sur- Oceanology. (Council for Scientific & Industrial rounding region. Research research report; no. 380.) JEFFERY, D. 1996. An abbreviation of the botanical sensitivity analysis report for portion 7 and Acknowledgements remainder portion 8 of the farm Zoetendalsvlei no. 280 of July 1995. Environmental consulting Mrs. F. Siebert is thanked for her assistance during and facilitation services, Klapmuts. data processing. Low, A.B. & A.G. Rebelo. 1998. Vegetation of South Africa, Lesotho and Swaziland: A companion to the vegetation map of South Africa, Lesotho and References Swaziland. Pretoria: Department of Environ- mental Affairs & Tourism. MACVICAR, C.N. 1991. Grondklassifikasie ‘n tak- BEHR, C.M. & G.J. BREDENKAMP. 1988. A phytosociological classification of thevegetation of the sonomiese sisteem vir Suid-Africa. Pretoria: Witwatersrand National Botanic Garden. South Departement van Landbou-Ontwikkeling, African Journal of Botany 54(6): 525–533. MALAN, J.A., J.H.A. VILJOEN, H.P. SIEGFRIED & H. DE V. WICKENS. 1994. Die geologie van die BREDENKAMP, G.J. & L.R. BROWN. 2001. Vegetation – a reliable ecological basis for environmental gebied Riversdale. Pretoria: Staatsdrukker. planning. Urban Greenfile Nov-Dec 2001: MUSTARD, P., R. COWLING & J. ALBERTYN. 1997. 38–39. Southern Overberg: South African wildflower COWLING, R.M. (ed.). 1992. The ecology of Fynbos: guide 8. Cape Town: National Book Printers. nutrients, fire and diversity. Cape Town: Oxford SCHEEPERS, J.C. 1983. Vegetation studies in South University Press. Africa. Bothalia 14: 683–690. Cowling, R.M. & D. Richardson. 1995. Fynbos: STRYDOM, S. 1992. A classification of Southern Cape South Africa’s Unique floral kingdom. Cape coastal dunes and the associated vegetation. Town: Fernwood Press. MSc: thesis, University of Port Elizabeth, Port EDWARDS, D. 1972. Botanical survey and agriculture. Elizabeth. Proceedings of the Grassland Society of South- TINLEY, K.L. 1985. Coastal dunes of South Africa. ern Africa 7: 15–17. Pretoria: Council for Scientific and Industrial EDWARDS, D. 1983. A broad-scale structural classifi- Research, National Scientific Programmes Unit. cation of vegetation for practical purposes. (South African National Scientific Programmes Bothalia 14: 705–712. report; no. 109.) GOLDBLATT, P. & J. MANNING. 2000. Cape plants – a WERGER, M.J.A. 1974. On concepts and techniques conspectus of the Cape Flora of South Africa. applied in the Zürich-Montpellier method of Pretoria: National Botanical Institute of South vegetation survey. Bothalia 11: 309–323. Africa. ZIETSMAN, M.M. & G.J. BREDENKAMP (in press). HEYDENRYCH, B.J. 1994. Limestone Fynbos – Threatened Limestone Fynbos plant communi- Unique but Threatened. An investigation into the ties of Andrew’s Field and Tsaba-Tsaba Nature conservation status of Limestone Fynbos in the Reserve. Bothalia.

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