Browsing by Author "Sieben, Erwin"

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    The contribution of wetlands to regional plant diversity in South Africa
    (2018-06-21) Sieben, Erwin
    On an evolutionary time-scale, wetlands are transient habitats across the landscape. The populations of plant species that are adapted to the wetland environment are maintained by the regional supply of propagules following continuing local colonisations and extinctions in the metapopulation. For this reason, it is useful to consider the bioregional species pools for each bioregion and consider which species within these species pools have adaptations to grow in the wetland environment. Species were classified as obligate wetland species, facultative wetland species or non-wetland species. The proportion of obligate and facultative wetland species for each bioregion was correlated to various variables that are associated to those bioregions. This proportion has no correlation to the total surface area of wetland habitat (derived from the National Wetland Map 5) so this means that a bigger surface area does not automatically mean that more species have evolved or colonised the wetland habitat (thereby not following the neutral theory of biodiversity). The proportion of wetland species is however correlated to the mean annual precipitation for each bioregion, so this suggests that more rainfall results in steeper wetness gradients and thereby more species diversity. This also corresponds to the finding that wetter bioregions also contain more wetland vegetation types.
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    Distribution of wetland vegetation types, their conservation importance and their ecological drivers in South Africa
    (SANBI, 2015-06-25) Sieben, Erwin; Mtshali, Hlengiwe; Janks, Matthew
    Wetlands are recognized as delivering important ecosystem services especially in the light of an impending water crisis in the country. For this reason, wetlands have played an important role in strategic conservation planning for the purpose of water resource management, but they also play an important role as habitats for biodiversity. The plants that make up the various vegetation types in wetlands form important components of this biodiversity and an overview of plant community composition and the physical environment of wetlands is a useful tool in the management of wetlands for biodiversity. For this reason, a database was set up with wetland vegetation data compiled from various historical studies and supplemented with additional fieldwork. 28 The final database that has emerged from this effort has a total of 5583 vegetation plots and is still growing. This dataset has been classified into 244 plant community types each of which can be recognized by a specific combination of indicator species and widespread species. Ordination diagrams produced by Canonical Correspondence Analysis outline the most important environmental factors that drive wetland community composition. The most species-rich wetland communities are found in the high mountains, the mistbelt region of KwaZulu-Natal and the renosterveld in the Western Cape. Some areas are very rich in community types, among them the Western Cape and Maputaland stand out.
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    Factors controlling wetland formation
    (Elsevier, 2021) Job, Nancy; Sieben, Erwin
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    South African Inventory of Inland Aquatic Ecosystems
    (CSIR and SANBI, 2018-07-01) van Deventer, Heidi; Smith-Adao, Lindie; Mbona, Namhla; Petersen, Chantel; Skowno, Andrew; Collins, Nacelle; Grenfell, Michael; Lötter, Mervyn; Ollis, Dean; Scherman, Patricia; Sieben, Erwin; Job, Nancy; Snaddon, Kate