The vegetation of grass lawn wetlands of floodplains and pans in semi-arid regions of 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 data as well as newly collected data.
• Grass lawn wetlands, represented by 947 plots, have been pulled out of the national database.
• Cluster analysis led to 37 clusters which have been summarized into 13 groups.
• Canonical ordination reveals that the main environmental gradient within these wetlands is made by sandy substrates on the coast versus clayey substrates inland.
• These wetlands are mainly found in a semi-arid region of the country where they may be affected by climate change and need to be monitored.

This paper describes grass lawn wetlands, which are wetlands subjected to dynamic conditions, particularly highly fluctuating water tables that regularly drop deep below the ground surface. This occurs mostly in floodplain wetlands, as well as in wetlands in semi-arid regions or coastal plains. These wetlands are often dominated by short lawn grasses, particularly Cynodon dactylon, while other life forms, from taller tufted sedges to trees and shrubs, occur less frequently. A subset of data from a nationwide survey of wetland vegetation representing these grass lawn wetlands was selected for analysis using clustering and ordination techniques. Thirty-seven wetland communities are described and are further summarized into 13 community groups. Wetland communities on the coastal plains were associated with sandy soils whereas most of the other communities had a high clay fraction. Grass lawn wetlands are commonly found in a zone along the central, semi-arid part of the country and for this reason will likely play an important role in wetland monitoring in the long term.