S. Afr. J. Bot., 1988, 54(1); 1 - 10

A classification of the vegetation of the

C.J.G. Ie Roux*, J.O. Grunowt, J.W. Morris" G.J. Bredenkamp and J.C. Scheepers1 Department of Nature Conservation and Tourism, S.W.A.! Administration; Department of Production, Faculty of Agricultural Sciences, University of Pretoria, Pretoria, 0001 Republic of South ; 1Botanical Research Institute, Department of Agriculture and Water Supply, Pretoria, 0001 Republic of and Potchefstroom University for C.H.E., Potchefstroom, 2520 Republic of South Africa Present addresses: C.J.G. Ie Roux - Dohne Agricultural Research Station, Private Bag X15, Stutterheim, 4930 Republic of South Africa and J.W. Morris - P.O. Box 912805, Silverton, 0127 Republic of South Africa t Deceased Accepted 11 July 1987

The Etosha National Park has been divided into 31 plant communities on the basis of floristic, edaphic and topographic features, employing a Braun - Blanquet type of phytosociological survey. The vegetation and soils of six major groups of plant communities are described briefly, and a vegetation map delineating the extent of 30 plant communities is presented.

Die Nasionale Etoshawildtuin is in 31 hoof plantgemeenskappe verdeel op basis van floristiese, edafiese en topografiese kenmerke met behulp van 'n Braun - Blanquet-tipe fitososiologiese opname. Die plantegroei en gronde van ses hoofgroepe plantgemeenskappe word kortliks beskryf en 'n plantegroeikaart wat 30 plantgemeenskappe afbaken, word aangebied. Keywords: Edaphic features, phytosociological survey, vegetation map *To whom correspondence should be addressed

Introduction with aeolian Kalahari-type sands. The first two major soil The Etosha National Park is situated in the north of South groups are probably related to shrinking of the Pan, and the West Africa/Namibia and straddles the 19° South latitude aeolian sands are a more recent overburden. The soils in the between approximately 14° and 16° East longitude. It has an western regions of the Park are influenced by the range of area of 2,2 million ha and is one of the largest national parks dolomite hills and the geological components of the escarp­ in the world. ment. In the 1960's it was decided to 'develop' the Park as a The temperatures are quite high (the average temperature tourist attraction, and it was realized that an ecological survey at Okaukuejo is 22,1°C) and most of the rain falls in the was a prerequisite to the sound development of the Park. It summer months between November and April (Figure 1). was considered necessary: There is a pronounced rainfall gradient with rainfall dimi­ (1) to map reasonably homogeneous units of study; nishing from about 450 mm in the east to about 300 mm per (2) to investigate plant/environment relationships; annum in the west (Figure 2) (Dept. of Water Affairs 1973). (3) to study the production of herbage and its utilization in The relatively high temperatures, low rainfall and poor soils the more important grazing areas; suggest that vegetative growth is determined largely by the (4) to survey the less intensively used vegetation types and available moisture, although trees may bloom and commence investigate the feasibility of increasing their utilization; growth before effective rain falls. Drought may cause these and, early leaves to drop. 'Spring' conditions commence with the (5) to study possible developments in the field of tourism. onset of the major rainy season in about February. In this paper a vegetation map of Etosha National Park Figures 1 and 2 indicate that the rainfall decreases quite based on the first objective is presented, together with a markedly from east to west. In the east, where the rainfall description of the major vegetation types and soils revealed is nearly 450 mm per year, the trees reach 6 m in height, in the course of the study. whereas in the west with about 300 mm rain per year, the trees on similar calcareous soil barely reach 2 m in height. The study area Although some of the plant occur throughout the The Park lies in the vast geosyncline into which the Damara range of rainfall conditions, there are some which are confmed supergroup was deposited. Owing to the tectonic stability in to either the higher-rainfall (e.g. Spirostachys africana) or the the area since then, most of the Park is very flat. Although drier regions (e.g. Sesamothamnus guerichiz). there are a few inselberge in the area south of the Etosha Pan, The origins of the soils have been discussed by Verster it is mainly in the extreme south and west of the Park that (1980), who also described their nature. The present soil map there are any hills or escarpments. A range of dolomite hills (Figure 3) is more detailed than Verster's (1980), being based skirts the Park in the south, and just enters the Park in the on a larger number of soil profiles. In Figure 3 it can be seen west. Here the geological features are more varied and that in the eastern and central regions of the Park a relatively granites, andesites, shales, quartzites and pyroclastic material small number of soil classes each cover relatively large areas. can be found in addition to the more general limestones and In the west of the Park the soils are more heterogeneous. dolomites. The greater diversity of soils in the western region of the In general terms the area south and south-west of the Park as opposed to the uniformity in the east is associated Etosha Pan is a karstveld, with calcrete rubble on the surface. with geological and geomorphological features. Most of the West of the Pan there is an extensive area with calcareous Park lies on the central African plateau, and the underlying loamy soils and the north of the Park is mainly covered geological features of the Damara supergroup have largely 2 S.-Afr. Tydskr. Plantk., 1988, 54(1)

• b d Tsumeb (1311 m) 532,0 a) Station; (55 - 57) b) Height above sea level; c) Mean annual temperature in °C; d) Mean aooual precipitation in mm; e) Duration of observations, of two figures the first indicates temperature, second indiCates precipitation; f) Highest temperature recorded; 142,7 g) Mean daily maximum temperature of warmest month; h) Mean daily minimum temperature of coldest month; i) Lowest temperature recorded; j) Mean duration of frost free period in days; 933,6 k) Curve of mean monthly precipitation; I) Curve of mean monthly temperature; m) Months with absolute minimum temperature below 10°C .

Scale: 5,7 mm = 10°C; = 20 mm rainfall

h 7,

i -3,9 J A S o N o J F M A M J Ot jovasandu (1200 m) 323,9 Okaukuejo (1103m) 418,3 (2-3) (3-73·)

39,6

35,0

5,9

J A S 0 N 0 J M A M J -3,3 J A S 0e N 0 J F M A M J Oi~inuous

Figure 1 Climatic diagrams after Walter (1973) .

550 ~550

_----500

. Tsumeb

.Otavi

2,0 4p 6.0 80 1qOkm

~ 50 100 150 200 2SO 300 350 400 0450 SOD SOD 450 450

Figure 2 Rainfall isohyets (mm). S. AfT. 1. Bot., 1988,54(1) 3

been covered by an overburden of aeolian sand. The west x 10 m for herbs and 100 m x 100 m for trees and . of the Park lies on the western escarpment, and the geological If necessary, the areas were increased to give a more repre­ features of the Damara supergroup, intrusive granites, the sentative sample. These sampling inventories are referred to Khoabendes group and Basement complex granites are visible. as releves. The releve data were synthesized into plant com­ In the Park about 32 ()()() , 9 ()()() , 2 500 munities using a Braun - Blanquet type of procedure and the , 725 ostriches, 650 and 125 red computer program described by van der Meulen, Morris & hartebeest (Berry 1980) are concentrated on about 150 ()()() Westfall (1978), and other programs compiled by Kingman ha of plain. A further population of at least 500 elephant, (1979). 900 kudu, 400 and 130 eland (Ebedes, Maritz & de In the following account, the nomenclature of plant species Jager 1971) are to be found in wooded areas. There are also referred to follows Gibbs-Russell et al. (1984). The soils of some black-faced impaia and roan antelope, chiefly in the the'S' sampling units and releves were classified according Otjovasandu area. Among the carnivores there are 300 to 400 to the South African binomial soil classification system , a similar number of spotted hyaena, 70 to 80 cheetah (MacVicar et al. 1977) (Figure 3). Soils from the releve sites and 1 ()()() to 2 ()()() black-backed jackal (Berry 1980). were analysed for: exchangeable cations, pH (H20 and KCI), phosphorus and texture. Soils of the'S' sampling sites were analysed for: first-mentioned two plus clay, silt and sand Methods percentages, electric resistance and carbon in all horizons; and Vegetation units were identified on vertical monochrome aerial nitrogen and phosphorus in the A horizon (Fertilizer Society photographs at roughly 1: 75 ()()() scale and the boundaries of South Africa 1974). For the horizons of the'S' sampling transferred to existing topocadastral maps of that scale. In units available soil moisture storage capacity was determined some cases LANDSAT A false-colour infra-red photographs from their depth, salinity and clay content using the graph were consulted for additional information. The boundaries of du Plessis & Hutson (1974). A moisture index was obtained were verified in the field as far as possible. These units were by multiplying the moisture storage capacity of the soil by later grouped to form what were regarded as major mapping the estimated rainfall at the site. or management units, on the basis of edaphic, topographic, physiognomic and floristic features. The major mapping units Results and Discussion were used for an initial grouping of releves and other sampling The constancy values of a selection of species in the major units in the subsequent Braun - Blanquet type of classification plant communities are given in Table 1. The edaphic features procedure. refer only to the upper horizon or layer. The species listed During 1972 and 1974, 59 stand ('S') samples were taken are approximately 171I70 of the total number of species en­ for ordination studies not dealt with here. During 1975, the countered during the phytosociological survey. To be included vegetation was sampled by 203 sampling units (see Figure 4) in Table 1, a species had to be reasonably diagnostic with using procedures similar to that of the Zurich - Montpellier regard to presence in or absence from a particular noteworthy School of Phytosociology (Werger 1974). Plot size was 20 m type.

50 km

DOMINANT SOIL SERIES DOMINANT SOIL SERIES SANDY SOILS KARST VELD SOILS

51 FW lANGEBAAN (-) Kl MS KAlKBANK 52 HU ROODEPOORT K2 GS LEKFONTEIN 53 CV SUNBURY K3 MS KAlKBANK / liTHOSOL 54 CV SUNBURY K4 CV DUDfIELD 55 HU ZWARTFONTEIN K5 LlTHOSOL 56 FW LANGEBAAN (-) K6 AR ARCADIA / LlTHOSOl 57 HU ZWARTFONTEIN K7 AR ARCADIA DEEP SOILS OF OYAMBQ PLAINS MISCelLANEOUS LAND CLASSES II ES HEIGHTS R DOlOMrrE/ MARBt£ / CALCRETE l2 FW LANGEBAAN (+) I: RHYOLITIC ROCK

L3 VA VAlSRIVIER P SALINE PAN

Figure 3 Major soil mapping units. ""'"

10 20 30 40 50km

93 91 N 92 '109 90 80 553' 94 ·543 e ·45 95 554 81· ·96 '127 82 S. .108 "83 126. 16f! ·97 54,4 .89 124 125 122 • • 123 542 .88 0 120 • 121 ,110 119 111 ·84 090 ·87 .85 ·112 118 ·113 1~9. 131 ~17 S~4 86 549 32 115 l~.B 31 520 130 • '32 116 ·48 o 114 527 33 30 S~7 204 .133 2CiJ H, 193 .134 L 6, 'S16 188 551 7. 6k 2\ S1? .17 51 558 167 S5~ 187 53 56 55. S12 '20 202 ·35 • 54 546 57 .191 190 556'0 515 .25 186 514 55 .135 555,5 {66 .26 192 • "85 52 60 184 48 526 59 .61 101 557 519 536' 100 ~9 14 6~ ·23 181 195 136 .180 12 10 '179 .S18.t9 q ·11 .103 .178 .S35 T .183 • 177 • 176 4, 170 106 533 --..: . ,,171'7 2 534 • .:.-475 ·...-"174 . 173 en :l> :=;' Figure 4 Location of sampling units. ...., '< 0- ~ -0 OJ ;;.::>

\0 00 00 v. ~ S. Afr. 1. Bot., 1988,54(1) 5

Table 1 Synoptic table of major vegetation types

Major vegetation types

Species groups A B C Dl D2 D3 E F GI G2 H

I. Differential species of tall grassveld communities (mapping units 3, 4 & 5) Euphorbia inaequilatera III Aizoon virgatum III Eragrostis annulata III III II Eragrostis glandulosipedata III I I paucinervis IV II I II Indigofera charlieriana IV II I Triraphis purpurea III Salsola arborea II Zygophyllum simplex II 2. Differential species of Andoniveld (mapping unit 2) Sporobolus spicatus V Eragrostis biflora III Craspedorhachis sarmentosa III III Mariscus squarosa III Sporobolus consimilis III 3. Differential species of the sweet grassveld on lime (mapping unit I) Geigeria odontoptera III Cyathula hereroensis III Hirpicium gazanioides III II Ruel/iopsis setosa III 4. Differential species of Mopane treeveld (mapping units 8, 9, 10 & II) , Vernonia cinerascens II I II Triraphis ramosissima IV III II III Seddera suffruticosa III III I divaricata II I I Aristida rhiniochloa III III II I 5. Differential species of Marula associations (mapping units 12, 13, & 14) Securinega virosa II IV I Blepharis obmitrata I III II II Spirostachys africana IV I I Euclea undulata III III Acacia nilotica IV 6. Differential species of dolomite inselberge (mapping unit IS) Kirkia acuminata IV Cissus nymphaeifolia III Kalanchoe brachyloba III Euphorbia guerichiana III Commiphora glaucescens III 7. Differential species of the eastern Karst woodlands Oropetium capense III III III II Grewia vil/osa III IV III I Bidens biternata II III II I II Maytenus senegalensis II III I

8. Differential species of Kaokoveld (mapping units 25 - 30) Lantana dinteri II Aptosimum angustifolium III Mundulea sericea III Requienia sphaerosperma III Grewia retinervis II Ptycholobium biflorum II

9. Species common to D & E Fingerhuthia africana III III III foetida II III III Acacia senegal II II I Combretum apiculatum III IV V IV Abutilon fruticosum III III I II Anthephora schinzii III IV II II Eragrostis nindensis II III III IV III Chascanum pinnatifidum I II II II III Justicia platysepala II II II 6 S.-Afr. Tydskr. Plantk., \988, 54(1)

Table 1 Continued

Major vegetation types

Species groups A B C Dl D2 D3 E F GI G2 H Melhania virescens II III I II III Pupalia lappacea I I II I II 10. Species common to F & G Commiphora angolensis II IV IV Tephrosia purpurea IIJ IV IV Colophospermum mopane () II II IV IV I II 11. Differential species of G. sandveJd Grewia deserticola II II III Acacia fleckii I II III III IV II Indigofera daleoides II II Lonchocarpus nelsii II III Aristida meridionalis II IV III Ocimum canum II II Acacia ataxacantha II II Acacia erioloba III II Merremia tridentata III III 12. Differential species of western sandveld Elephantorrhiza suffruticosa II II IIJ Kohautia caespitosa III Schizachyrium exile II 13. Differential species of eastern sandveJd Bauhinia petersiana III Combretum col/inum II 14. Differential species of bottom lands Acacia kirkii II Rhynchosia minima II IJI Nidorel/a resedijolia III Eragrostis rotijer IJI Corchorus asplenijolius IV

Thirty-one mapping umts or plant communities (with sionis has a high cover in the Ekuma grasslands. Forbs include subdivisions), were recogmzed (Figure 5) and these were Hirpicium gazanoides, Zygophyllum simplex, Hermannia arranged in six major groups. There is similarity between the modesta, Euphorbia inaequilatera, Kohautia azurea and boundaries of some of the vegetation umts and some of the Merremia palmata. soil mapping umts (Figure 3). The major groups of plant commumties are in some cases named after the most salient B. Adoniveld pedological or geological feature, as in 'Karst woodlands', This commumty is represented by mapping umt 2 (Figure 5). 'sandveld areas', and 'shrub-mopane on loamy soils'. Within The shallow soils of this vegetation type, which is generally a group the various plant commumties are frequently sepa­ found within a metre above the level of the Pan, are quite rated on the basis of relatively minor pedological features. saline and more or less alkaline with a pH (KCI) of about 8,5. They are of the Heights series of the Estcourt form, and A. Tall grassveld communities the sodium status of the impervious clay layer is 5 000 to The Okondeka duneveld, Poachers' pemnsula and Ekuma 10 000 ppm. Historically the Andomveld was grazed during grasslands (mapping umts 3, 4 and 5, Figure 5) are included the rainy season only. However, owing to the provision of in this major commumty. The soils of these commumties are permanent waterholes they are now grazed chiefly during the frequently of the Langebaan series (Fernwood), and are of late dry season when forage is scarce elsewhere. recent aeolian origin. The sands often overlie calcrete and free The differential species of Andoniveld are listed in species lime is often present. Most of these commumties are ecolo­ group 2, Table 1. The most prormnent species in this vege­ gically fragile and it is fortunate that they are not grazed to tation type are the very coarse stolomferous Sporobolus any extent. The differential species for this commumty are spicatus, while Odyssea paucinervia and Craspedorachis listed in species group 1, Table 1. Woody are not sarmentosa are common. In areas from which these grasses prormnent in these grasslands. However, the shrubs Salsola have disappeared, probably as a result of grazing pressure or tuberculata, Leucosphera bainesii, Dichostachys cinerea and trampling, Aristida adscensionis and Enneapogon desvauxii alexandri are locally common. Grass species sometimes occur in almost pure stands. Shrubs such as frequently found in the herbaceous layer include Triraphis Indigofera sUffruticosa and Dichrostachys cinerea are locally purpurea, Monelytrum luederitzianum, Stipagrostis uniplumis, invading the plains. Eragrostis lehmanniana, Eragrostis sabinae, Eragrostis porosa, Enneapogon cenchroides and Enneapogon desvauxii. In the C. Sweet grassveld on lime Poachers' pemnsula area, Stipagrostis uniplumis is physio­ Mapping umt 1 (Figure 5) represents this vegetation type. gnormcally the most important species, while Aristida adscen- These extensive grasslands, bordering the southern edge of S. Afr. 1. Bot., 1988,54(1) 7

the pan, constitute the most important grazing land in the these regions become severely overgrazed. Park. These grassy plains are grazed extensively during the The soils of these sweet grasslands are loamy, silty or clayey, rainy season by large numbers of herbivores. During the long usually shallow and underlain by a hardpan, in this case, dry season, the animals are forced to concentrate near the calcrete. The dominant soil forms and series are lithosols, waterholes, mostly along the southern edge of the Pan, and Mispah form, Kalkbank series; Glenrosa form, Lekfontein

LEGEND

MAJOR COMMUNITIES

A TALL GRASSLAND COMMUNITIES OKONDEKA DUNEVELD .. .. POACHERS PENINSULA 5 ::::::: EKUMA GRASSLANDS 6 :::::: OMURA MBA ONAISO I7 KARST VELD TURF PANS B ANDONIVELD

G:::bd SWEET GRASSVELD ON LIME

EASTERN KARST WOODLANDS MOPANE TREEVELD CMOPANE/CAPICULATUM/TpRUNIOIDES iiUNGARIES - VEGET ATION MAPPING UNIT MARBLE HILLOCK THAI- TKAB WOODLANDS MARULA ASSOCIATIONS !-PRUNIOIDES/'?AFRICANA WOODLAND DOLOMITE INSELBERGE

KAOKOVELD A.REFICIENS/CMOPANEITPRUNIOIDES THORN SCRUB C.MOPANEICAPifOLArUM/S.GUERICHIl BUSHVELD OTJOVASANDU HILLY MOPANE SAVANNA ----KAROSS GRANITIC MOPANEVELD 1...... RENOSTERVLEI CMOPANEICHEREROENSEI .?GUERICHII SHRUBLAND - SHRUB MOPANE ON LOAMY SOILS NINETEENTH LA TlTUDE SHRUB MOPANEVELD NARAWANDU SHRUB MOPANEVELD EKUMA WOODLANDS SHRUB MOPANE ON ES HOURT -FORM SOILS

SANDVELD AREAS SANDY SHRUB MOPANEVELD PARADYS VEGETATION MAPPING UNIT SANDY TERI1INALIA ACAOA SHRUBLAND SOUTH-EASTERN SANDY BUSHVELD NORTH-EASTERN SAND VELD WARES SANDY I10PANE ICot18RETlJt1 HEREROENSEI SESAHOTHAt1NUS GUERICHH SHRIJ8LAND H 8OTTOf1 LAIIlS SALINE Alii/OR DEPRESSED AREAS

Figure 5 Map of vegetation types. 8 S.-Afr. Tydskr. Plantk., 1988,54(1) series; and Valsrivier form, Lindley series. They generally have 8, 9, 10 and 11) on shallow lithosols with coarsely frac­ a reasonably high cation exchange capacity, with a high tured calcrete on the soil surface. proportion of adsorbed calcium and magnesium. They are (2) Marula associations and Terminalia prunioides/ Spiro­ frequently oversaturated and the pH is high (7,5 to 8,0 or stachys ajricana woodland (mapping units 12, 13 and 14) higher, in CaCh). The high salinity may cause physiological in the wetter eastern parts on very shallow soils which dryness. These soils have, as a rule, the lowest available water overlie calcified dolomite or low-grade marble. indices in the Park. They also have high nitrogen levels in (3) Dolomite inselberge (mapping unit 15). the A horizons. The high nitrogen levels may be associated with the occurrence of the blue-green alga Nostoc sp., which 1. Mopane treeveld and related vegetation is relatively abundant on these saline soils. These vegetation types include Mopane treeveld (mapping unit The differential species for these grasslands are listed in 8), Co!ophospermum mopane/ Combretum apiculatum/ species group 3, Table 1. Although these stands are typically Terminalia prunioides bushveld (mapping unit 9), Dungaries treeless plains, woody plants may be present in localized areas. vegetation (mapping unit 10) and Marble hillock (mapping The more common woody plants are Acacia nebrownii, A. unit 11). tortilis, A. mellifera, A. reficiens, Aloe littoralis and Albizia The soils are similar to those of the adjoining sweet anthelmintica. A. nebrownii occurs in extensive thickets. In grassveld. Lithosols, representing the Kalkbank series (Mispah these situations there may be up to 850 trees per hectare. form) and Glenrosa form. The calcrete is generally in a Catophractes alexandri may also be present but then usually coarsely fractured form when superficial. The available in association with other trees. moisture indices are generally higher than the grassveld. The more important shrubs are Leucosphaera bainesii, The differential species of this vegetation type are listed in Cyathula hereroensis, Monechma tonsum, M. genistifolium species group 4, Table 1. In some of the stands, Co!ophos­ and Petalidium englerianum. Salsola aphylla forms occasional permum mopane may be the sole woody species. In other pure stands and Suaeda articulata is found typically on the cases, Catophractes alexandri, Acacia reficiens, Acacia melli­ saline soils of the Lindley series (Valsrivier form). jera, Grewia spp., Montinia caryophyllacea, Commiphora Protected sites show that this veld type is quite capable of pyracanthoides, Acacia senegal, Boscia joetida, Boscia a/bi­ supporting taller-growing perennial grasses such as Stipagrostis trunca, Acacia nebrownii and Gossypium triphyllum may be hochstetteriana and Cenchrus ciliaris. However, most of the present in the tree or shrub stratum. The herbaceous layer veld type is at present in a relatively stable dis-climax stage is quite similar to that of the sweet grassveld on lime (C). induced biotically by excessive grazing. In this condition the In some cases where the soils are even shallower, and where more important herbs are Enneapogon desvauxii, E. cen­ the soil surface is almost completely covered with calcrete chroides, Aristida adscensionis, Eragrostis nindensis, Euphor­ rubble, Combretum apiculatum and Terminalia prunioides bia inaequilatera, Tragus berteronianus, Oropetium capense, become more prominent. Here the shrub layer consists of Tribulus terrestris, Kohautia azurea, Indigojera charleriana, young individuals of the tree species and a few others, such Eragrostis annulata and Geigeria odontoptera. In the Spring­ as Commiphora pyracanthoides, Gymnemma sylvestre, bok and Charistsaub Plains areas Monelytrum luederitzianum Vernonia cinerascens, Grewia flava and Leucosphaera bainesii. becomes more important. In the most heavily grazed (Namu­ The herb stratum is usually poorly developed, probably toni) area, this relatively stable dis-climax has been destroyed because the surface is almost pure calcrete rubble. and sheet erosion is taking place. Here Sporobolus coroman­ delianus is important and in some areas S. spicatus and 2. Marula associations and Terminalia prunioides/ Spi­ Geigeria species are physiognomically very conspicuous. On rostachys africana woodland the fertile Lindley series (Valsrivier form), the herb layer has This vegetation type includes mapping units 12, 13 and 14 been destroyed and Sporobolus coromandelianus may be (Figure 5). important. In the eastern areas with slightly higher rainfall, a further variation of the Karstveld is found, usually on boulder D. Eastern Karst woodlands calcrete. The soils are very shallow and overlie a calcified These woodlands are situated south of the Etosha Pan and dolomite or a low-grade marble. They are, however, relatively extend westwards. They are usually separated from the saline fertile and have nitrogen and phosphorus values of 2 300 and pans by a strip of sweet grassveld on lime. 57 ppm, respectively. The higher-lying areas generally have The soil is generally a calcrete litho sol representing the a few centimetres of heavy clayey soil between the calcrete Kalkbank series (Mispah form) or Lekfontein series (Glenrosa boulders, which erupt on the surface. The soils of the low­ form). There are a few dolomite inselberge and some outcrops lying areas are typically Arcadia form and series, but one of a low-grade marble. In some areas there is a matrix of profile was recorded as Swartland form (Broekspruit series). calcrete high ground and clayey depressions. The vegetation is characterized by the differential species , These vegetation types are easily identified by the presence listed in species group 5, Table 1. Colophospermum mopane of the differential species listed in species group 7, Table 1. and Terminalia prunioides are the most important trees. The woodlands are generally mopaneveld Colophospermum Towards the east, Spirostachys ajricana becomes more mopane, except in the extreme east, where Spirostachys important and can have importance values of about 15070 in ajricana is prominent in a small area. Near the edges of the the tree stratum. Securinega virosa, Gymnemma sylvestre and pans Colophospermum mopane forms almost pure stands, Euclea undulata are quite frequent additions to the list of but further away Combretum apiculatum, Terminalia pru­ shrubs. The herb stratum is fairly well represented and has nioides and Acacia nilotica become more important as the a high proportion of perennial grasses e.g. Eragrostis nin­ vegetation becomes richer in species. This greater species densis. On some sites, Commiphora pyracanthoides becomes richness is related to an increase in the soil's moisture index. prominent forming a dense canopy with Cenchrus ciliaris in Eastern Karst woodlands comprise three major subtypes: the herb stratum having a canopy cover of usually more than (1) Mopane treeveld in the drier western parts (mapping units 1%. The typical T. prunioides - S. ajricana woodland near S. Afr. J. Bot., 1988,54(1) 9

Namutoni is distinguished mainly by the absence of Colo­ Terminalia prunioides, Colophospermum mopane and Se­ phospermum mopane, and the presence of Combretum samothamnus guerichii, the shrubby Lantana dinteri, imberbe and Ximenia americana, although both these species Vernonia cinerascens, Indigofera texeirae, Euphorbia gue­ may occur elsewhere. richiana and Montinia caryophyllacea may be present. The In these woodlands, Terminalia prunioides becomes domi­ herbaceous stratum is perennial with Eragrostis nindensis very nant, while Spirostachys africana, Acacia rejiciens and Di­ prominent. Other prominent grasses include Anthephora chrostachys cinerea may also be important. The trees are up pubescens, Triraphis ramossissima, Stipagrostis hochstet­ to 6 to 7 m tall. There are approximately 475 trees and 3 450 teriana, Fingerhuthia africana, Stipagrostis uniplumis and shrubs per hectare. The herbaceous layer consists mainly of Aristida adscensionis. On the relatively acid soils of granitic annuals. origin in the area, Schmidtia kalahariensis and Microchloa kunthii become prominent, while the clay loam soils of the 3. Dolomite inselberge Clovelly form above the edge of the escarpment carry Com­ There is a range of Otavi dolomite inselberge along the bretum hereroense and Sesamothamnus guerichii. Here southern boundary and in the western Otjovasandu area. Eragrostis annulata, E. nindensis, Anthephora pubescens and There are also a few isolated outcrops, as in the Halali area. Aristida adscensionis are of the more prominent species. The Otavi group dolomite outcrops are bare rock with a very small amount of soil in the fissures or cavities. The soils F. Shrub mopane on loamy soils generally have very high phosphorus values (more than This vegetation type comprises mapping units 21 to 24. 90 ppm). Mopane trees and shrubs occur over an extensive area in a Differential species of this vegetation type are listed in region commonly called the nineteenth latitude. On the aerial species group 6 in Table 1. The vegetation of these inselberge photographs this area was characterized by the presence of is characteristic as regards composition and structure. Kirkia small depressions. There are four or five distinct physiognomic acuminata, Cissus nymphaefolia, Moringa ovalijolia and types in the area but the boundaries between the types could Euphorbia guerichiana which are relatively rare elsewhere frequently not be identified on the aerial photographs. occur on most of these sites. Other common trees are Ter­ In the region under discussion, the more common soils minalia prunioides, Combretum apiculatum, C. mopane and belong to the Estcourt form, Valsrivier form, Fernwood form in some areas Sclerocarya caffra. (Langebaan series) and the Arcadia series. The area has a loamy substrate or, if it is sandy, the clay content is reasonably E. Kaokoveld high and the calcium content is also high. In the extreme west of the Park the geological and geo­ The depressions are characterized by their soils which belong morphological nature of the terrain change abruptly. Although to the Arcadia form and series. Although the occasional tree much of the material is still calcareous, there are large areas may occur in these small pans (often on termitaria), they are of rhyolitic, andesitic and granitic origin. This large area is typically open grassy patches. The most conspicuous grasses mainly mopane veld representing the following mapping units are Eragostis rotijer and Bothriochloa radicans. (Figure 5). The shrub mopane vegetation on loamy soils has no Mapping unit 25 - Acacia rejiciensl Colophospermum differential species, but can be distinguished from other mopanel Terminalia prunioides thorn vegetation types by the presence of species group 10 in the scrub. absence of species group 11. Colophospermum mopane in Mapping unit 26 Colophospermum mopanel Com­ shrub form is clearly the dominant species. Other species bretum apiculatuml Sesamothamnus include Catophractes alexandri, Leucosphaera bainesii, Di­ guerichii bushveld. chrostachys cinerea and Grewia jlava. Prominent species Mapping unit 27 Otjovasandu hilly mopane savanna. in the herbaceous layer include Aristida adscensionis, A. Mapping unit 28 Kaross granitic mopaneveld. rhiniochloa, A. hordeacea, A. effusa, Geigeria acaulis, Mapping unit 30 Renostervlei Colophospermum mo­ Pogonarthria jleckii, Hermannia modesta, Monelytrum panel Combretum hereroensel Sesa- luederitzianum, Stipagrostis uniplumis, Heteropogon contortus mothamnus guerichii shrubland. and Limeum fenestra tum . The differential species of the Kaokoveld are listed in species group 8, Table 1. Species group 9 indicated the floristic G. Sandveld relationships between the Kaokoveld vegetation type and the There are areas of deep Kalahari-type sand in the north-east eastern Karst woodlands. and north-west corners of the Park. The sand in the west is In some areas the soils are very similar to those of eastern finer than that in the east indicating that it was transported Karst woodlands, i.e. very shallow lithosols on a calcrete farther than the eastern sand. In the extreme west the sand substrate. Here Acacia rejiciens, Terminalia prunioides and is also shallower than that in the east, and the underlying especially Colophospermum mopane are dominant. Shrubs calcrete is exposed in some western situations. The western of Gossypium triphyllum, Boscia foetida, Monechma genisi­ parts are also markedly drier than the eastern parts. The tijolium, Petalidium englerianum and Leucosphaera bainesii sandveld covers mapping units 16, 17, 18, 19, 20 and 29. are also frequently found. A sheet of aeolian sands locally A large number of species occur almost exclusively in the covers the calcrete boulders. On these sites, Sesamothamnus sandveld. Differential species are listed in species group 11, guerichii, Catophractes alexandri, Otoptera burchellii and Table 1. Two major sub-vegetation types are distinguished: Mundulea sericea also become prominent. The herbaceous (1) Dry western sandveld. layer is well developed here, with Anthephora schinzii, Ennea­ (2) Relatively wetter eastern sandveld. pogon desvauxii, Stipagrostis hirtigluma and Enneapogon cenchroides prominent. On the hilly areas on the andesites 1. Dry western sandveld of the Khoabendes group, the lithosolic soils are relatively Differential species for the drier vegetation type are listed in fertile. In addition to the dominant Combretum apiculatum, species group 12, Table 1. On the shallower sands in the west 10 S.-Afr. Tyd8kr. Plantk., 1988, 54(1) of the Park, shrub mopaneveld occurs. Here Colophosper­ be equated with mapping units (see Figure 5) that are relevant mum mopane is the prominent woody plant, while Leu­ for management purposes. cosphaera bainesii, Seddera sujjruticosa, Rhigozium brevi­ spinosum and Commiphora angolensis are often present. Grasses include A n theph ora pubescens, Pogonarthria jleckii Acknowledgements and Eragrostis dinteri. On some sites where the soils are deeper The authors wish to thank all individuals and organizations (Paradys vegetation, mapping unit 17), Terminalia sericea that provided support in various ways. The Administration becomes prominent, while Acacia erioloba, Dichrostachys of South West Africa/Namibia funded a major part of the cinerea and Croton gratissimus may also be present. study as Research Project 31 of the Division of Nature In local depressions, especially on the Hutton or Clovelly Conservation. The Soils and Irrigation Institute analysed some form soils, Acacia rejiciens is conspicuous. Important herbs 100 soil samples free of charge, and Mr Louis Sim arranged on these sites include Schmidtia kalahariensis, Eragrostis the same for some 300 soil samples. Mr Buys of the Fertilizer lehmannia, Acanthosicyos naudiniana, Fimbristylis exilis and Society arranged that the Citrus Exchange analyse some soil Aristida meridionalis. samples free of charge. The Botanical Research Institute identified plant specimens and supplied computer facilities . 2. Wetter eastern sandveld Dr Eben Verster classified the soils of 59 profiles. Mrs J. This vegetation can be identified by the presence of the Schaap of the Botanical Research Institute helped to finalize differential species listed in species group 13. the figures for publication. The soils are deep kalahari sands or coarse acid sands on fractured sandstone of the Nosib group. The woody plants in this vegetation type are dominated by Terminalia prunioides, References T. sericea, Croton menyhartii, Lonchocarpus nelsii, Grewia BERRY, H.H. 1980. Behavioural and ecophysiological studies on jlava, Combretum col/inurn, Bauhinia macrantha and Ochna blue wildebeest (Connochaetes taurinus) at the Etosha National pulchra. Important herbs include Schmidtia kalahariensis, Park. Ph.D. thesis, Univ. of Cape Town. Digitaria pole-evansii, D. perottetii, Oxygonum alatum and DEPARTMENT OF WATER AFFAIRS. 1973. Rainfall isohyets for South West Africa. Dept. of Water Affairs, Windhoek. Hirpicium gorteroides. DU PLESSIS, H.M. & HUTSON, J.L. 1974. Soil and water in H. Bottomlands irrigation. The Citrus and Subtropical Fruit Journal July: 4-11. Several communities occur scattered throughout the Park in EBEDES, H ., MARITZ, N. & DE JAGER, M. 1971. Interim slightly depressed areas and similar situations. The soils in report on aerial counts of wildlife in Etosha National these situations are typically Arcadia series (Arcadia form) Park. Unpublished progress report, Project 28, S.W.A.A. and similar clayey soils, usually with free lime. In some cases Windhoek. the individual communities were large enough to map sepa­ FERTILIZER SOCIETY OF SOUTH AFRICA. 1974. Manual of rately but usually this was not the case. soil analysis methods. FSSA Publication No. 37. GIBBS RUSSEL, G.E. AND THE STAFF OF THE NATIONAL Plants that often indicate these situations are Acacia kirkii, HERBARIUM 1984. A list of species of southern African Acalypha spp., Rhynchosia spp., Eragrostis rotijer, Corchorus plants. Mem. Bot. Surv. S. Afr. No. 48. asplenifolius and others. JENSEN, R.A.C. & CLINNING, C.F. 1976. Birds of the Etosha National Park. Division of Nature Conservation and Tourism, I. Saline pans S.W.A.A. Windhoek. The Etosha Pan and the other saline pans comprise the largest KINGMAN, E.R. 1979. Programmes to improve readability and single 'vegetation' unit in the Park. Their combined area is sort data on departmental computer. (Unpub\. Agricultural almost one quarter of the total area of the Park. These pans Research Station, Dohne). LE ROUX, c.J .G. 1980. Vegetation classification and related are largely without vegetation. studies in the Etosha National park. D.Sc.(Agric.) thesis, Univ. Ostriches nest on the Pan, as they are afforded some of Pretoria. protection from scavenging jackals. In seasons when water MACVICAR, C.N., DE VILLIERS, J.M., LOXTON, R.F., is available, flamingos (Jensen & Clinning 1976) and pelicans VERSTER, E., LAMPRECHTS, J.J.N., MERRYWEATHER, breed or nest on the Pan. F.R., LE ROUX, J., VAN ROOYEN, T.H. & VON The soil is a whitish clay which cracks into hexagonal HARMSE, H.I. 1977. Soil classification: a binomial system for South Africa. Department of Agricultural Technical Services, fragments on drying. The pH is very high (8,18 to 10,2) and Pretoria. the sodium content is in excess of 30 000 ppm. VAN DER MEULEN, F., MORRIS, I.W. & WESTFALL, R.H. Higher plants are rare on the Pan although in a year of 1978. A computer aid for the preparation of Braun - Blanquet above-average rainfall Sporobolus salsus may be present tables. Vegetatio 38: 129 - 134. especially near the edges (e.g. Homob). On smaller hummocks VERSTER, E. 1980. Die aard en genese van die gronde van die Suaeda sp. may be found. 'Islands' of vegetation, mainly Etoshawildtuin, Suidwes-Afrika. Proc. 9th Congo Soil Sci. Soc. sth. Afr. pp. 116 - 123. Sporobolus salsus, form on the larger hummocks. WALTER, H. 1973 . Vegetation of the earth in relation to climate Conclusions and the eco-physiological conditions. Springer, New York. WERGER, M.I.A. 1974. On concepts and techniques applied in The Etosha National Park has been divided into a number the Ziirich-Montpellier method of vegetation survey. Bothalia of major vegetation types using floristic data and these can II: 309 - 324.