Short-term vegetation change on rehabilitated peatland on Rietvlei Nature Reserve

Abstract

Natural peatlands occur on the Rietvlei Nature Reserve. Before the Pretoria City Council acquired the land, these peatlands were mined by private land-owners. Ditches were constructed to drain the area for mining and the peatlands became desiccated. Later the area was proclaimed as a nature reserve and has since then been managed as such. Rehabilitation of the drained peatland on Rietvlei Nature Reserve first started in 2000 as a Working for Water project. The aim of the rehabilitation was to close the ditches and rewet the peatland, to enable possible revival of the peatland. A baseline vegetation survey was undertaken during the summer (March to April) of 2001 to determine the nature of the pioneer communities that established on the rehabilitated area. This survey was repeated during the summer (March to April) of 2002 to detect changes in the vegetation. The same sample plots were used on both occasions. The initial pioneer vegetation was mostly composed of weedy annuals. Three communities were identified from the 2001 data set using the classification algorithm TWINSPAN. DECORANA ordination showed a clear distinction between the community on the mined and the communities on the drained areas. A specific pioneer community dominated by Persicaria species established on the rehabilitated ditches. Phragmites australis reed communities, with Phytolacca octandra, were prominent on the least disturbed sites. Cyperus dominated communities, without reeds (Phragmites australis), occurred on areas that were mined extensively, but not rehabilitated. The 2002 floristic data was added to the baseline data and the ordination procedure as performed on the 2001 data set was repeated on this new data set. The results indicate that within a single year the vegetation already started to change in the direction of the climax communities.