R.A. Lubke

Aspects of the vegetation and soil relationships in the Andries Vosloo Kudu Reserve, Cape Province

The soils of the grasslands and bushclumps within permanent 100-m2 quadrats in the Andries Vosloo Kudu Reserve, Cape Province, were examined. Eight soil variables (moisture content, organic content, conductivity, pH, Ca, Mg, K and Na concentration) were determined. The soils of the grasslands were found to be poorer than those of the bushclumps in Ca, Mg, K and Na. Soils of the grasslands had lower conductivity and pH values than the soils of the bushclumps. Bushclumps soils contained higher percentages of organic material, with higher moisture content, Mg and Ca. Ordination by means of principal component analysis of the eight variables revealed a relationship between phytosociological classification and soil attributes.

The role of European marram grass in dune stabilization and succession near Cape Agulhas, South Africa

The coastline near the southern tip of Africa is characterized by large mobile dunes that are driven along wide beaches by strong winds throughout the year. This results in the blockage of the river mouths causing severe flooding of the low-lying farmland of the Agulhas Plain during the rainy winter season. Large parts of the driftsands were stabilized with the European dune pioneer species Marram grass (Ammophila arenaria), which has proved highly invasive along the North American west coast. In order to establish the potential invasiveness ofA. arenaria in South African coastal dune systems and its role in the succession of a large stabilization area, studies were carried out on De Mond Nature Reverve. Using aerial photos, maps and planting records, the vegetation of sites of various ages were sampled. By means of this chronosequence of stands, there is clear evidence that succession takes place at De Mond. Four communities are distinguished, varying from recent plantings ofA. arenaria to mature dune thicket or dune fynbos (heath) vegetation. These relate to four different stages of succession,A. arenaria occurring in reduced abundance in the older communities. After 50 years, formerA. arenaria areas are usually covered by dense dune scrub and in some places even in asteraceous dune fynbos. Succession is most rapid in sheltered, moist dune slacks, butA. arenaria remains vigorous in conditions favourable for its growht, i.e. on exposed, steep dune slopes with strong sand movement.A. arenaria does not appear to spread unaidedly at De Mond and has been successfully used for temporary dune stabilization.

IsAmmophila arenaria (Marram grass) a threat to South African dune fields

Ammophila arenaria (marram grass) was introduced to South Africa from Europe as a means of stabilizing the Cape Flats in the 1870s, but was only successfully established in the 1890s as it was found that seeds from the first introductions did not readily germinate. By the end of the last century, it was successfully used as a dune stabilizing grass. It is now widely used in stabilization projects along the Cape coastline, being established by planting cuttings or whole plants. Because of problems experienced of marram becoming invasive, especially on the west coast of North America, and the fact that we have many invasive species which threaten our indigenous dune fields, studies have been initiated on this plant in South Africa. Most work to date has involved investigating the methods used to establish the plant in stabilization sites, and very little has been done on the biology of the species in this country. Marram is generally thought not to seed in South Africa, and thus its spread has been limited.However, in the light of recent reports of successful germination of the seed, detailed studies on the phenology of seed production and establishment in natural areas will be undertaken. Studies on the natural control by fungal species and nematodes will be carried out in conjunction with work done in the Netherlands, so that a comparison of the biology of the species in South Africa can be made with that in Europe, where it is used extensively to stabilize dunes.

The effect of wind-borne sand and salt spray on the growth of Scirpus nodosus in a mobile dune system

Much of the coastline along the eastern Cape consists of Shifting sand dunes with little vegetation cover. It was postulated that in the Kleinemonde River area Scirpus nodosus Rottb., a pioneering sedge of the dune slacks, was limited to this region of the dune system because of the effect of wind-borne sand and salt spray. This was tested by planting seedlings of S. nodosus at seven selected sites from the edge of the spring high water mark to the coastal scrub and monitoring their growth and corresponding environmental factors. Of the soil factors, a detrimentally high conductivity was recorded only on the foredunes. Salt spray had a deleterious effect on plant growth on the foredunes, Whereas sand movement was important along the entire profile; at some sites the only factor causing the death of plants. It appears that sand movement and low percentage soil moisture were the major factors preventing S. nodosus plants from becoming established throughout the dune system. Groot dele van die kuslyn langs die oos-Kaap bestaan uit bewegende sandduine met min plantegroeibedekking. Dit is aanvaar dat Scirpus nodosus Rottb., ’n pionier watergras van die tussenduin-holtes in die Kleinemonderivier gebied, beperk is tot ’n streek van die duinsisteem as gevolg van die effek van verwaaide sand en soutsproeireen. Saailinge van S. nodosus was uitgeplant op sewe uitgesoekte persele van die springty-hoogwatermerk tot by die kusstruikgewasse om die aanname te toets deur monitoring van hul groei en ooreenstemmende omgewingseienskappe. Van al die grondeienskappe was ’n nadelige hoer elektriese geleiding net op die voorduin bepaal. Soutsproeireen het ’n nadelige effek op plantegroei op die voorduine uitgeoefen, terwyl sandbeweging belangrik was langs die hele profiel en op sekere persele was dit die enigste faktor wat plant-mortaliteit veroorsaak het. Dit lyk asof sandbeweging en ’n lae persentasie vogligheid die belangrikste faktore is wat die vestiging van S. nodosus-plante dwarsdeur die duinsisteem verhinder.

Indigenous and Ammophila arenaria-dominated dune vegetation on the South African Cape coast

. Communities formed by the potentially invasive European Ammophila arenaria (marram grass) are compared with those dominated by indigenous dune plant species in coastal dune systems. Sampling of communities was carried out along the Cape coast for species richness, species diversity, importance values and species associations. The influence of soil and other environmental factors on vegetation were also compared. While species richness values in A. arenaria communities appear similar to those of indigenous dune plant communities, diversity indices are significantly lower. However, on the basis of importance values of individual species, A. arenaria does not show extreme dominance to the exclusion of other species, as it does on the North American Pacific coast, where it has also been introduced. Because of its growth in dense tufts, A. arenaria is accompanied mostly by small chamaephytes and therophytes, while indigenous stands support more phanerophytes. Moreover, A. arenaria forms weaker species associations than dominant indigenous dune plant species. The alien status of A. arenaria in South Africa is confirmed by applying classification and ordination analyses which failed to differentiate A. arenaria communities according to their geographical origin as achieved with indigenous communities. This may be attributed to the lack of vigorous indigenous plants in A. arenaria communities, which accounts for the low variety in species composition of A. arenaria communities along the coastline. With regard to environmental factors, A. arenaria communities were observed to be less sensitive to extrinsic factors, such as climate, than indigenous dune plant communities. Results confirm that A. arenaria is an alien plant species in South Africa, but do not imply its invasiveness in the present or near future.

Reproductive phenology of Scaevola plumieri; a key coloniser of the coastal foredunes of South Africa

Given the role of Scaevola plumieri as a major pioneer species in the dune environment, as well as the need forindigenous sand stabilisers for South Africa’s coastal dunes, the reproductive phenology was unravelled as a firststep to establish the potential usefulness of the species in dune stabilisation programmes. In the highly variablecoastal environment the plants must cope with many problems for successful reproduction to take place. Theplants of S. plumieri overcome these difficulties through vegetative reproduction, but sexual reproduction is byno means insignificant. Numerous peduncles, each carrying multiple buds, were produced per stem, but only fewdeveloped into ripe seeds. Several of the flowers were unfertilised and of the seeds produced many were infectedand/or aborted. There was a strong effect of dune position on the reproductive phenology of S. plumieri. Thestems situated at the landward face of the foredunes showed an overall higher reproductive performance numberof buds, flowers, unripe seeds, ripe seeds. The phenogram showed that the reproduction of stems at the landwardside of the foredunes started on average 34 days earlier and showed a tendency for a longer reproductionperiod. For the duration of the different stages in the reproduction sequence, the bud stage’ took the shortesttime and the ‘ripe seed stage’ longest time. Between the different sample years, the production of the number ofpeduncles, buds, flowers and seeds was the similar; only differences in reproduction time (duration) of the differentstages were observed for the bud, flower an unripe seeds stage between the sample years.

Restoration of Dune Ecosystems Following Mining in Madagascar and Namibia: Contrasting Restoration Approaches Adopted in Regions of High and Low Human Population Density

In this study a proposed site for heavy mineral dune mining in southwestern Madagascar, and an experimental study on desert dunes following mining for diamonds on the southwestern corner of Namibia are compared. Madagascar is very rich in flora and fauna and has become a center for studies on endemism and unusual biota. The Namib Desert region of Namibia is no less important as a conservation hot spot. The two areas are very different in physical, biological, and social environments, which make for very different approaches to the restoration of the sites following mining. The low rainfall southwestern coastal region of Madagascar is fairly heavily populated and the restoration strategy is to provide natural vegetation, woodlots for timber or fuel or crop plants for the surrounding villages. In the Namib Desert, following mining, a restoration project was designed and implemented where dwarf shrubs were transplanted and the site was left to recover naturally by spontaneous restoration. Wind-blown seeds of plants in adjacent areas were established in the mined areas amongst the transplants resulting in a community similar to that of the pre-mining state. Seedlings were able to survive partial burial and exhibit increased growth in conjunction with sand accumulation.

Short term changes in the woody vegetation of Nylsvley

The woody plant vegetation in 416 permanent quadrats in five areas of the Eragrostis pallens — Burkea africana savanna has been monitored at intervals since 1974. The data were analysed to describe changes in individual trees and woody plant communities. Frequency, density, biomass and importance values of the trees and shrubs for successive years are summarized in the form of tables and graphs. Most interesting are the changes in abundance and biomass of the dominant woody species. The significance of these changes can be related to population structure as influenced by climate and management (mainly fire) over this eight-year period.

The effect of salt spray on the growth of Scirpus nodosus

Field studies suggested that salt spray may have a detrimental effect on the growth of Scirpus nodosus plants. In a controlled greenhouse experiment plants of three different height classes were sprayed with varying concentrations of salt water. It was found that only plants in the seedling stage were significantly affected by the salt spray. The amount of chloride ions received by the treated plants was equivalent to that deposited by wind-borne salt on plants growing on the foredunes. Thus the position on the shore where S . nodosus seedlings become established may be controlled by the amount of salt spray that they receive.

Arenicolous marine fungi from southern Africa

A survey was conducted to determine the distribution of marine fungi on sandy beaches along the coast of southern Africa. Foam samples collected from twelve beach sites in South Africa and Namibia were examined microscopically for the spores of marine fungi. A total of 38, 1 and 6 species from each of the Ascomycota, Basidiomycota and mitosporic fungi, respectively, were identified. Samples indicated that fungi were present in large numbers on most beaches. While some species were shown to have a wide distribution, others were restricted either to warm east coast or to cold west coast waters. Corollospora fusca was restricted to the east and south coasts, but numbers were low in the cooler waters from which spores of significantly smaller size were collected. Relative abundances of individual species of fungi showed interesting variations and, generally, could be related to water temperature around the coast. Computer analysis using TWINSPAN and DECORANA revealed that sample sites could be divided into five regions, viz. extreme west coast, south-west coast, south coast, wild coast, and KwaZulu-Natal coast. Information from areas to the north of southern Africa is needed to provide a more complete picture of distribution patterns. Marine fungi appear to have an important role to play in organic matter decomposition in our sandy beach ecosystems. Management of sandy beaches should take the role of these organisms into consideration.