Browsing by Author "Holmes, Patricia M."

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    Guidelines for restoring Lowland Sand Fynbos ecosystems
    (2022-02) Holmes, Patricia M.; Esler, Karen J.; Geerts, Sjirk; Ngwenya, Duduzile K.; Rebelo, Anthony G.; Dorse, Clifford; van der Merwe, Jacques; Retief, Jacobus; Hall, Stuart A.; Grey, Penelope; Nsikani, Mlungele N.; Faculty of AgriSciences, Department of Conservation Ecology and Entomology.
    Lowland Sand Fynbos ecosystems are among the most threatened terrestrial systems in South Africa. Of the ten Sand Fynbos veld types, seven are Critically Endangered or Endangered according to the IUCN Red List of Ecosystems. They are all either poorly protected, or not protected at all in the conservation network. Sand Fynbos ecosystems harbour unique biodiversity, but owing to their lowland locations experience extensive losses to other land uses. Some natural pockets remain scattered within agricultural or urban developments. They are, however degraded due to invasive alien plants, inappropriate fire regimes or pollution and are an urgent priority to restore. National biodiversity targets aim for a minimum proportion of an ecosystem type to be retained in a natural or near-natural state. The minimum target for Sand Fynbos ecosystems is mostly 30% of the original extent – a target no longer attainable for several of these ecosystems, such as Cape Flats Sand Fynbos. For many of these precious systems, this means a necessary focus on their restoration. The purpose of these guidelines is to assist managers and landowners of degraded Sand Fynbos vegetation to restore biodiversity and contribute to the conservation of these threatened ecosystems. The guidelines outline appropriate methods to restore degraded Sand Fynbos ecosystems, based on the latest research and field trial outcomes.
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    Heat and smoke pre-treatment of seeds to improve restoration of an endangered Mediterranean climate vegetation type
    (John Wiley & Sons Australia Ltd, 2017) Hall, Stuart A.; Newton, Rosemary J.; Holmes, Patricia M.; Gaertner, Mirijam; Esler, Karen J.
    Invasive alien plants impact ecosystems, which often necessitates their removal. Where indigenous species recovery fails following removal alone, an active intervention involving reintroduction of seed of native species may be needed. This study investigated the potential for a combination of the fire cues of smoke and heat as a pre-treatment of seeds in breaking dormancy and facilitating increased germination. Species were selected to represent different functional types within Cape Flats Sand Fynbos; a fire-prone, critically endangered vegetation type in South Africa. Seeds were exposed to either a heat pulse (temperatures between 60 and 300°C for durations of between 30 s and 20 min) or dry after-ripening (1 or 2 months at milder temperatures of 45°C or less). Thereafter, seeds were soaked in smoke solution for 18 h and subsequently placed on agar at 10/20°C for germination. Most species fell into one of two main groups: Seed germination in the first group was greatest following a lower temperature (60°C) heat pulse, an extended period of mild temperature (20/40°C or 45°C) exposure, or no pre-treatment with heat. Seed germination in the second group was promoted after brief exposure to higher (100°C) temperatures. No germination occurred in any species following heat treatments of 150°C or higher. Species which responded better to higher temperatures were mainly those possessing physical dormancy, but seed morphology did not correlate with germination success. This study showed that heat stimulation of seeds is more widespread in fynbos plant families than previously known and will enable the development of better seed pre-treatment protocols before large-scale sowing as an active restoration treatment after alien plant clearing.
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    Invasive potential and management of naturalised ornamentals across an urban environmental gradient with a focus on Centranthus ruber
    (AOSIS, 2018-08-16) Holmes, Patricia M.; Rebelo, Anthony G.; Irlich, Ulrike M.
    Background: Predicting which alien species may become invasive is important in prioritising scarce resources for management. Objectives: Sixteen naturalised ornamentals in Cape Town were assessed for invasion potential in relation to a mechanistic framework. The recently spreading species, Centranthus ruber (L.) DC., was studied in detail following management actions and vegetation fires. Method: The mechanistic framework was developed using nine features most likely to promote invasiveness. Species were assessed from their known characteristics, local usage and distribution records, including citizen science surveys. Surveys were conducted for C. ruber to assess its ability to survive and spread post-fire. Control efficacy for Centranthus ruber was assessed in plots at two sites. Results: Nine species with more than 25 naturalisation records had a median of seven features that promote invasion compared to five features in the less recorded group of seven species. Centranthus ruber was widespread in modified urban habitats and persisted in natural habitats following vegetation fires and is a high priority for control. Post-fire mechanical and chemical control of C. ruber significantly reduced its density and cover, but did not eliminate it. Conclusion: Naturalised ornamentals can move rapidly from latent to invasive phases; therefore, monitoring should start during the latent phase to detect sudden change. In firedriven ecosystems it is essential to have good pre-fire baseline data. More residents should be encouraged to become spotters through citizen science programmes and to report new naturalised ornamentals. It is important to act early in the invasion process and to allocate sufficient resources, if a newly invasive species is to be contained.