The vegetation of inland wetlands with salt-tolerant vegetation in South Africa: Description, classification and explanatory environmental factors

• A database of wetland vegetation plots for South Africa has been constructed on the basis of existing and newly collected data.
• Inland saline wetlands, represented by 506 plots, have been pulled out of the national database.
• Cluster analysis led to 29 clusters which have been summarized into 15 groups.
• Canonical ordination reveals that the main environmental gradients are made by electrical conductivity and sodium content of the soil.
• These wetlands are mainly found in the arid regions and their extent may expand under the prospects of climate change.

Knowledge and understanding of wetland vegetation is an important component of sound wetland ecosystem management as vegetation represents a link between biota and ecosystem processes. In this paper, the saline wetlands of the arid inland regions of South Africa are discussed. Even though these wetlands contain water only occasionally they are among the largest wetland ecosystems in the country and their ecosystem processes are mostly determined by hydrological processes and particularly clay and salt deposition. These wetlands are dominated by three different groups of plants: salt-tolerant lawn grasses, sedges (occasionally) or halophytic shrubs. A subset of data from the South African National Wetland Vegetation Database, representing these vegetation types was used for analysis by means of clustering and ordination techniques. Twenty-nine saline wetland communities are described and these are further summarized into 15 community groups. Of the environmental variables used to explain the variation in the vegetation patterns, wetness appears to have the most important effect as it is also negatively correlated with electrical conductivity. Among the cations, it is sodium that has the greatest influence on species composition. Most of the types of saline wetlands are restricted to the Northern Cape and Free State Provinces, but plots with salt-tolerant grasses are found in all provinces except Gauteng.