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"Lubke, R.A"
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Use of Ammophila arenaria for dune stabilization in South Africa and its current distribution--perceptions and problems
/ This paper examines the use of the European dune pioneer plant Ammophila arenaria (marram or European beach grass) for dune stabilization in South Africa in the past and present, its present distribution in South Africa, and the perceptions of coastal management agencies and the public about its further use. The planting of A. arenaria became the most important means of dune stabilization, by human intervention, along the South African Cape coast in this century. Its modern distribution from the semiarid west coast to the subtropical shores of the Eastern Cape extends through various climatic zones. Although historical data are missing for some areas, there is no indication of its unaided spread. A. arenaria occurs at most sites because of its prior planting. The South African climate appears to affect its vigor. However, concern about the use of the alien grass has been raised since it has proved to be a highly invasive species in other parts of the world, particularly along the North American west coast and in Tasmania. While the CSIR (Council of Scientific and Industrial Research) promotes its use, CNC (Cape Nature Conservation) follows a policy that restricts the use of any alien plant, including A. arenaria, and requests further research on its invasive properties. Although a questionnaire survey shows that stabilization sites featuring large areas of A. arenaria are accepted by the South African public, current coastal management practices need to be analyzed critically. A thorough investigation of the potential invasiveness of A. arenaria on South African coastal dunes will be essential and shed new light on the American A. arenaria problem.KEY WORDS: Ammophila arenaria; Marram; European beach grass; Dune stabilization; South Africa; Coastal managementhttp://link.springer-ny.com/link/service/journals/00267/bibs/24n4p467.html
Journal Article
The search for indigenous dune stabilizers: Germination requirements of selected South African species
The coastline of South Africa is characterized by extensive dune fields which are threatened by development, and thus the demand of stabilization of drift sand will increase. The non-invasive alien grass species Ammophila arenaria is at present the dominant sand stabilizer. Due to its foreign origin and invasiveness in North America its use was criticized and indigenous sand-binding species would be preferred. The germination requirements of the native Arctotheca populifolia, Ipomoea pes-caprae, Myrica cordifolia and Scaevola plumieri were investigated. The results showed that for all four species the total germination time and germination phase could be shortened and germination success (number of germinated seeds) improved. The different scarification and stratification treatments broke the dormancy of I. pes-caprae, M. cordifolia and S. plumieri, whereas the seeds of A. populifolia were not dormant. Seeds of I. pes-caprae and M. cordifolia had induced an innate dormancy, respectively, whereas the type of dormancy in seeds of S. plumieri dormancy processes remained unknown. Nomenclature: Arnold & De Wet (1993)
Journal Article
Is Ammophila 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.
Journal Article
High-Probability Uniquantal Transmission at Excitatory Synapses in Barrel Cortex
The number of vesicles released at excitatory synapses and the number of release sites per synaptic connection are key determinants of information processing in the cortex, yet they remain uncertain. Here we show that the number of functional release sites and the number of anatomically identified synaptic contacts are equal at connections between spiny stellate and pyramidal cells in rat barrel cortex. Moreover, our results indicate that the amount of transmitter released per synaptic contact is independent of release probability and the intrinsic release probability is high. These properties suggest that connections between layer 4 and layer 2/3 are tuned for reliable transmission of spatially distributed, timing-based signals.
Journal Article