A brief account of coast vegetation near Port Elizabeth

The environment and vegetation o f an area o f coast north-east o f Port Elizabeth, South Africa, are briefly de­ scribed. Five major vegetation categories are recognized. These are: 1. Scaevola thunbergii Pioneer Vegetation o f littoral dunes and Ficinia lateralis Sedgeland o f calcrete gravel; 2. Olea exasperata Bush, Pterocelastrus tricuspidatus Bushclumps and Dune W oodland; 3. Sundays River Scrub; 4. Fynbos o f calcrete areas; and 5. The­ meda triandra Grassland. Invasion o f the area by Acacia cyclops (Australian W'attle) is described. A recommenda­ tion for the conservation o f the area as a nature reserve is made.


IN T R O D U C T IO N
Some years ago the Botanical Research Institute was asked to report on the plant communities and rare and endangered species, if any, to be found within an area proposed for the development of an iron-ore loading berth on the coast opposite St Croix Island, approximately 25 km north-east of Port Elizabeth.An account of the results of the investiga tion, based on a number of visits to the area by the authors of this paper, was given by Taylor (1976).As no prior detailed ecological studies had been under taken in the area, a relatively intensive study had to be made for reporting purposes.It is intended that this brief account will make the interesting informa tion collected more readily available than in an un published Departmental report.
The area of the investigation, from the Coega River in the west to the Sundays River in the east, is bounded by the sea to the south-east and the national road from Port Elizabeth to Grahamstown to the north-west.The area extends about 18 km along the coast and about 4 km inland (Fig. 1).
Regional accounts by Schonland (1919) and Dyer (1937) have included brief descriptions of vegetation similar to that found in the study area.Olivier (1977) compiled a checklist from a nearby area while Penzhorn et al. (1974) described the vegetation of the Addo Elephant National Park which contains some of the same veld types although it is not on the coast.Edwards (1971) briefly described the terrestrial vegetation of the Swartkops Estuary area, a few km west of the study area.

P H Y SIC A L F E A T U R E S
For approximately 300 m inland from the high water mark the area consists of relatively flat calcrete beds with occasional sand dunes.The ground then rises, gently at first and later sharply, until it forms a low ridge which runs roughly parallel to the beach, approximately 1 km from the sea and 60 m above sea level.The seaward slope of the ridge consists of deep sand, partly exposed as open dunes and partly bushcovered.Inland of the ridge the land slopes gently downward toward the national road and is relatively flat with occasional depressions and high points.There are no permanent water bodies except for the two rivers bounding the area to the east and west.
Geologically, the area is underlain by shelly and chalky limestones, sandstones and conglomerates of the Alexandria Beds.These are exposed along parts of the ridge, inland of which the Beds are covered by a layer of sandy soil 10 to 40 cm deep.
The area is classified as semi-arid, with a tempe rate, oceanic climate.The average maximum tempe rature at Port Elizabeth, 25 km to the south-west, is 25,5°C, the average minimum is 7,1°C, the extreme maximum is 34°C and the extreme minimum is 0°C (Fig. 2).The prevailing winds are south-west, east and south-east in January and west in July (Fig. 3).The average annual rainfall over a recent five-year period was 456 mm and the long-term average for Port Elizabeth is 614 mm (Anon, 1965).

N A T U R A L V E G E T A T IO N
Floristically, the area is by no means poor in species, except for the pioneer vegetation of the lit toral dunes.Phytogeographically, this area of coast is surprisingly interesting, containing elements of the fynbos flora of the south-western Cape, the grass lands of the interior plateaux, the subtropical to temperate coastal forests, and the possibly forestderived woody flora peculiar to the semi-arid valleys of the eastern Cape.Although these elements inter mingle to some extent, especially the grassland and fynbos, a single element usually predominates in each of the major vegetation types.
Five major vegetation categories are each briefly described below in terms of habitat, formation class, cover, physiognomy, species numbers in releves, dominance (if any), phytogeography and probable floristic affinities (where known).
•S p ecim en s have been deposited in STE with duplicates in P R E.

Pioneer Vegetation
Two communities occur on the coast edge.Des criptions of both are given below.

(a) Scaevola thunbergii Pioneer Vegetation
This community occurs on the littoral dunes.It is a semi-succulent herbland/dwarf shrubland with 20 to 65% cover, dominated by Scaevola thunbergii (Fig. 4).It is a very simple, pioneer community with an average height of 30 cm and rarely exceeds 50 cm.It consists mostly of individual erect stems of S. thun bergii with its spreading, fleshy leaves.The only other species are, in order of decreasing abundance, Tetragonia decumbens, Chrysanthemoides monilifera, Gazania rigens and the intrusive plant invader, Acacia cyclop s.

(b) Ficinia lateralis Sedgeland o f calcrete gravel
This community occurs inland of the littoral dunes and is developed on calcrete.It is a low (15 cm), closed community dominated by the sedge Ficinia lateralis, with a few emergent shrubs of Passerina vulgaris, which are 60 to 90 cm tall.In places Flelichrysum sp.(Taylor 9139)* takes the place of F. lateralis.This is another simple community and is not extensive.

Forest Precursor C om m unities
Three communities are recognized, all on recent sands, usually old dunes, on top of and on either side of the ridge.All contain, as dominants, species found in the early successional stages of Coast Forest.

(a) Olea exasperata Bush
Total cover in this woody community is 65 to 85%.It is dominated by Olea exasperata which forms an almost closed, woody layer 0,5 to 1,2 m tall (Fig. 5).An open, lower layer, characterized by Restio eleocharis, with spreading, succulent and ericoid sub shrubs and about 20 cm tall, is present.There is a sparse to very sparse ground layer of small succulents and annuals, 5 to 10 cm tall.Species numbers in releves were between 30 and 40.The Bush occurs on shallow sand over calcrete on the ridge and is thought to be similar to Olea exasperata Bush on the Cape Flats.

(b) Pterocelastrus tricuspidatus Bushclumps
Within the general area of Olea Bush, scattered Bushclumps occur where the blown sand is slightly deeper (25 to 50 cm) over the calcrete of the ridge (Fig. 6).Only a small number of clumps, each from 30 to 50 m2 in area, are present.Total cover is from 95 to 100%, dominated by Pterocelastrus tricuspida tus, which is 3 to 4 m tall, with other woody species including Olea exasperata, Rhus cf.glauca, Euclea undulata, E. natalensis and E. racemosa.Lower lay ers are sparse and generally poorly defined.Species numbers in releves were between 20 and 30.

(c) Dune Woodland
This closed woodland formation, probably a higher successional stage beyond Pterocelastrus tri cuspidatus Bushclumps, occurs on deep dune sand sheltered from on-shore winds.The only sample ex amined was on the lee side of the dune just west of the Sundays River bridge on the national road (Fig. 7).Total cover is 95% and average height from Knysna region, with a few additional Natal elements, including Brachylaena discolor and Sanseviera thyrsiflora.

Sundays River Scrub
Although containing a few elements also found in the Forest Precursor Communities (e.g.Sideroxylon inerme, Pterocelastrus tricuspidatus and Rhus crenata), this Scrub is nevertheless physiognomically and floristically distinct and probably has a different origin and history.Acocks (1975), in his broad scale treatment, mapped the whole of the study area as Valley Bushveld, a specialized and complex group of vegetation units.In his Memoir, the description of Valley Bushveld Variation (d) (ii), Sundays River Scrub, fits this community very well.Practically all the trees, shrubs and climbers that he lists as of general occurrence in the Sundays River Scrub were found in at least one of the four samples studied, and many of the species of less general occurrence were also present.Acocks considered that the Sundays River Scrub Variation was derived directly from the Alexandria Forest, which he described as a decidedly xerophytic variation of coastal tropical forest.This explains the lack of close relationship with the Forest Precursor Communities, which appear to represent the beginnings of the more typical coastal subtropi cal-temperate forest in this region.Acocks also con sidered that the Sundays River Scrub was closely related to the Gouritz River Scrub of the valleys west of the Knysna forest region.A brief investigation of Gouritz River Scrub in the Klein Brak River Valley confirmed Acocks's surmise, but further com parative study is needed to clarify the relationships.
In the area studied, Sundays River Scrub is a bush formation occurring chiefly on light brown, shallow sandy soils in the Coega River Valley, spreading in land onto the flats near the national road.West of the Coega River it occurs extensively on similar flats as far as the Swartkops River.Where relatively un disturbed, it consists of a thicket of stout, often thorny shrubs, with a 2 to 3 m canopy and a total cover of 95 to 100%.In parts where browsing cattle have penetrated in numbers, as in the lower part of the Coega Valley, the canopy has been reduced to 75 to 80% cover and to 1 to 2 m in height.On the borders of openings and along edges is a sparse, lower layer of soft-leaved herbs and where openings are extensive, smaller (20 to 30 cm), predominantly ericoid dwarf shrubs occur which, in a more detailed treatment, might be considered a separate communi ty.There is also a high proportion of succulents, especially along the margins and in small openings.Many climbing species are present, often sprawling over the top of the canopy.
The community is floristically the richest encoun tered, with 50 to 60 species being recorded in 300 m2 plots (Fig. 8).Euclea undulata was present in every releve and was usually dominant.Other species with high frequency, and sometimes attaining dominance or sub-dominance, are Rhus longispina, Cassine tetragona, Schotia afra, Sideroxylon inerme, Azim a tetracantha and a climber Rhoicissus tridentata.Aloe ferox is a prominent emergent, sometimes being up to 4 m tall.Portulacaria afra, though not in every releve, appears to be associated with high successional development and high species diversity.Panicum maximum was found in every releve and is a characteristic margin species.

Calcrete Fynbos
This is a dwarf shrubland formation occurring on very shallow soil (about 10 cm deep) over calcrete on the ridge, or its inland slopes (Fig. 9).Total cover is from 65 to 70%.An upper layer (barely 20 to 30 cm tall) of dwarf or sprawling shrubs (including ericoids) constitutes over 50% of the cover.A few emergents (40 to 50 cm tall) and a lower layer of creeping succu lents and very short grasses, 10 cm tall, are present.
Species numbers in releves were between 25 and 35 and characteristically there is no single species domi nant in the less disturbed stands, but the family Rutaceae is prominent and a Restio sp.(Taylor 9132) is occasionally present.No close affinities are known, but Ficinia truncata, a species found in all releves, relates this community, at a high phytosociological level, to communities in similar habitats along the southern Cape coast, e.g. in the vicinity of Bredas dorp.

Grassland
Themeda triandra Grassland is found on the flat plateau inland of Calcrete Fynbos, where the soil is not quite as shallow but is still underlain by calcrete (Fig. 10).Its upper layer is similar in height to that of Calcrete Fynbos (10 to 30 cm), but denser with over 50% of the 75 to 95% total cover being contributed by Themeda triandra, which is clearly dominant.Ehrharta calycina is sometimes subdominant.The ten other grass species found in the three samples studied do not contribute greatly to the cover, but in dicate the mixed origin of this community.Elionurus muticus, Eustachys paspaloides, Setaria sphacelata and Digitaria sp.(Taylor 9091) are mainly distributed to the north and east, whereas Cymbopogon marginatus and Plagiochloa uniolae are mainly concentra ted to the south-west.Among the forbs, too, there is a mixture of tropical-derived genera, like Barleria, Blepharis, Euphorbia and Tephrosia, with genera typical of the fynbos of the south-western Cape, e.g.Diosma, Ficinia, Stoebe and Passerina.Due, perhaps to its mixed nature, this community had the second highest species numbers in releves in the area, namely, 30 to 45.
On overgrazed sites, Themeda triandra assumes a minor role and dominance is taken over by Aspalathus lactea ssp.adelphea, Osteospermum imbricatum, Selago corymbosa, Psoralea fruticans and Euphorbia rhombifolia, amongst others.On pro tected sites, by contrast, individual pioneer elements and isolated small thickets of Sundays River Scrub were noted which, from the nature of their margins, suggest that the Scrub may be spreading at the ex pense of the Grassland (Fig. 10).According to one local landowner, this is substantiated by accounts of early settlers who referred to the whole area as a grassy plain.
The balance between Grassland and Calcrete Fyn bos also appears to be delicate, being influenced by depth of soil and by degree of grazing and trampling.Local farmers consider that fire is of minor impor tance as an ecological factor because the evenlyspread rainfall (Fig. 2) creates conditions that limit the occurrence and spread of wildfires, and the palatable grazing makes the use of intentional burn ing to produce new growth unnecessary.

EXO TIC P L A N T IN V A D E R S
About thirty-five years ago a landowner intro duced the Australian Wattle, Acacia cyclops (also known as Rooikrans), to stabilize the driftsands on his property.This species now forms a thicket on the seaward escarpment and is actively invading the Forest Initial Communities on the ridge and the Grassland and Fynbos beyond (Fig. 11).The Sundays River Scrub, due to the density of its canopy, is as yet largely free of Wattle, but where openings are being enlarged by cattle trampling, the Australian invader is gradually penetrating.
The farmer maintains that the infestation has not noticeably increased over the years, but judging from the abundant young growth of Wattle, especially along tracks, and its active suppression of the grass cover, colonization by this invader is proceeding apace.The tempo may, however, be less than in the Mediterranean-type climate of the south-western Cape where frequent dry-season fires encourage very dense regeneration from the heavy seed load in the soil.
Infestation in the Forest Precursor Communities, Grassland and Fynbos has now reached the critical stage where further spread of the invader will destroy the structure of the natural vegetation over one quarter to one third of the study area.If these plant communities are worth saving, both for their value as grazing and for their scientific interest and natural beauty, prompt action is necessary.

C O N S E R V A T IO N
As far as is known, none of the communities described in this report are conserved at present, ex cept for a few areas of Sundays River Scrub in the Tippers Creek Aloe Reserve at Swartkops, an area too small for viable ecosystem conservation.The Addo National Park consists of Addo Bush which, according to Acocks (1975), is a different variety of Valley Bushveld.The plant communities of the study area are of great variety, scientific interest and economic and recreational value.Some of them, such as Calcrete Fynbos, are not extensive elsewhere.It is our recommendation that the entire study area, bounded on three sides by natural features (Sundays River, Indian Ocean and Coega River) and on the fourth by a major road, should be conserved.A nature reserve of this size would be a worthy asset to the country as a sample of relatively well-maintained vegetation and a place for recreation and scientific study within 25 km of the fast-growing city and third largest port in South Africa, Port Elizabeth.

UITTREKSEL Die omgewing en plantegroei van *n gedeelte van die kus oos van Port Elizabeth, word kortliks beskryf. Die volgende v y f hoof-vegetasiekategoriee word onderskei: 1. Scaevola thunbergii-pioniervege-
scribed.Five m ajor vegetation categories are recognized.T hese are: 1. Scaevola thunbergii Pioneer Vegetation o f littoral dunes and Ficinia lateralis Sedgeland o f calcrete gravel; 2. Olea exasperata Bush, Pterocelastrus tricuspidatus Bushclum ps and D une W oodland; 3. Sundays River Scrub; 4. F ynbos o f calcrete areas; and 5.The m eda triandra G rassland.Invasion o f the area by Acacia cyclops (Australian W'attle) is described.A recom m enda tion for the conservation o f the area as a nature reserve is m ade.

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Fig. 1.-Location of the study area.

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ig .10 -Themeda triandra G rass land with isolated pocket o f Sundays R iver Scrub o n right.N o te windspray 'pruning' o f canopy.