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Each year the South African National Biodiversity Institute awards the Compton Prize for the best research paper in South African Journal of Botany. In January 2010, it was announced that the 2009 prize (for a paper published in 2008) would be awarded to the authors of a paper entitled “Can riparian seed banks initiate restoration after alien plant invasion: Evidence from the Western Cape, South Africa?”. The paper, part of special issue of the journal on “Riparian Vegetation Management in Landscapes Invaded by Alien Plants: Insights from South Africa”, was published by C·I·B Masters student Shelly Vosse (who graduated cum laude in December 2007) and her co-authors and supervisors, C·I·B core team members Profs Karen Esler and Dave Richardson and Dr Patricia Holmes (City of Cape Town).

Shelly Vosse at work in the greenhouse at Stellenbosch University. Seeds collected from soils in riparian zones were subjected to smoke and abrasion treatments to induce germination to enable the identification of species represented in the soil seed bank.

Riparian zones are complex disturbance-mediated systems that are highly susceptible to invasion by alien plants. They are prioritized in most alien-plant management initiatives in South Africa. The current practice for the restoration of cleared riparian areas relies largely on the unaided recovery of native species from residual individuals and regeneration from soil-stored seed banks. Little is known about the factors that determine the effectiveness of this approach. We need to know how seed banks of native species in riparian ecosystems are affected by invasion, and the potential for cleared riparian areas to recover unaided after clearing operations. Riparian seed banks were studied in four river systems in the Western Cape, and a comparison between invaded and uninvaded systems was done. Seed bank communities were clearly defined by the state of the river (reference or invaded) and moisture regimes (wet and dry bank zones). Comparisons at a landscape scale showed no clear pattern, as the composition of both aboveground and seed bank species assemblages were strongly influenced by site history, especially the extent of invasion and fire frequency. Even after heavy and extensive invasion, riparian seed banks have the potential to initiate the restoration process. However, not all riparian species are represented in the seed bank. Based on these results, restoration recommendations were outlined for alien invaded riparian zones.

Shelly Vosse now works as a freelance consultant in the fruit and wine sector, assisting clients with climate change mitigation and adaptation issues, such as improved conservation farming methods and carbon footprinting.