Abstract
The aim of this study was to create sown multi-layered communities of Mediterranean South African plants based on Fynbos and Renosterveld species. These communities were designed to test naturalistic design principles as to achieve long flowering designed plantings involving three canopy heights (tall, medium and low). Competition between shrubs/forbs/succulents and geophytes by using microcosm experiments mirrors the form of actual designed vegetation in practice. The experiments prior to the competition experiment provided the understanding of germination, winter cold and summer wetness tolerance of a large number of SA species (over 300 species) from Western Cape. All winter growing and summer dormant geophyte species had the capacity to emerge from autumn sowings, and some were able to do the same from spring sowing. Smoke treatment prior to sowing is effective on many forb and small shrub species from Fynbos and Renosterveld, but much less useful (or necessary) on geophyte species. Species such as Gladiolus carneus, Gladiolus tristis and Ixia curvata tolerated -8°C in winter 2010/11, and many more species survived -5°C in winter 2011/12. Bulbinella elata, Bulbinella elegans, Bulbinella nutans, Moraea tripetala, Kniphofia uvaria, Romulea atrandra and Romulea sabulosa suffered no loss at -5°C and no loss over summer 2012 (historically the wettest summer in the UK since 1910). Altitude and the resulting number frost days which individuals experience at the collection locations were critical factors influencing their winter mortality in Northern England. Habitat soil conditions and other environment factors are important in relation to their summer mortality. Species naturally occuring in Renosterveld and seasonally wet habitats are typically more wet tolerant response in Uk summers (i.e. many Bulbinella, Kniphofia, Gazania and Romulea species). Specific geographical provenances were explored to find more useful genotypes that can survive well in the UK. Species collected from the inland Roggeveld region, including the provenances Sutherland, Rooiwal, Groot Swartberg mountains, and the Komsberg, were the most successful species in response to winter cold in Sheffield. Fifteen plant community types were designed to access competition amongst 30 selected species in terms of mortality and biomass production within the studies main microcosm experiment. The most successful communities were generally those composed of tall canopy layer geophytes and forbs/shrubs. Geophytes suffered less mortality than shrub/forb/succulent species but contributed less biomass in the first two years, particularly in low height geophytes. Medium height geophytes formed a more extensive canopy and had higher competition capacity to increase their coverage and biomass in communities from the third year on. Species that did this included Watsonia ‘Tresco Dwarf Pink’, Gladiolus cardinalis and Watsonia schlechteri. Some small Fynbos and Renosterveld geophytes tested in the combinations demonstrated a degree of shade tolerance, as in Romulea komsbergensis, Ixia and Hesperantha species. These communities were managed by annual cutting in late summer-early autumn.
