venter.qxd Short-term vegetation change on rehabilitated peatland on Rietvlei Nature Reserve C.E. VENTER, G.J. BREDENKAMP and P-L. GRUNDLINGH Venter, C.E., G.J. Bredenkamp and P-L. Grundlingh. 2003. Short-term vegetation change on rehabilitated peatland on Rietvlei Nature Reserve. Koedoe 46(1): 53–63. Pre- toria. ISSN 0075-6458. Natural peatlands occur on the Rietvlei Nature Reserve. Before the Pretoria City Coun- cil 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. Reha- bilitation 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 sur- vey 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 vegeta- tion. 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 algo- rithm TWINSPAN. DECORANA ordination showed a clear distinction between the commu- nity on the mined and the communities on the drained areas. A specific pioneer com- munity dominated by Persicaria species established on the rehabilitated ditches. Phrag- mites australis reed communities, with Phytolacca octandra, were prominent on the least disturbed sites. Cyperus dominated communities, without reeds (Phragmites aus- tralis), 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 com- munities. Key words: vegetation survey; peatland; succession; rehabilitation. C.E. Venter, G.J. Bredenkamp and P-L. Grundlingh, African Vegetation and Plant Diversity Research Center, Department of Botany, University of Pretoria, Pretoria, 0002 Republic of South Africa. ISSN 0075-6458 53 Koedoe 46/1 (2003) Introduction Wetlands are very important in nature, because they form unique habitats for certain aquatic and hydrophilic plant species and also result in an increase in the number of waterfowl and other fauna typically associat- ed with wetlands. Wetlands lessen the devas- tating effects of floods and are responsible for clearer and healthier surface water. They act as a filter for debris and certain toxic sub- stances, such as heavy metals, and absorb large quantities of water that are eventually released over time into natural drainage channels (Hey & Philippi 1999). Wetlands in South Africa do not have high plant species diversity but some of the species that do occur in wetlands are restricted to these habi- tats (Bloem et al. 1993; Myburgh et al. 1995; Eckhardt et al. 1993; Smit et al. 1995). Addi- tional to these functional and biological val- ues, wetlands also have consumptive uses, e.g. they provide water to man and animals, they generate energy and can be used for fish farming. Non-consumptive uses include recreation, tourism and transport (Rand Water Scientific Services 1998). venter.qxd 2005/12/09 10:34 Page 53 The goal of a rehabilitation project may be to a particular species, or may include the reha- bilitaion of a whole ecosystem or landscape, or to restore the ecosystem functions (Ehren- feld 2000). South Africa ratified the Ramsar convention (Cowan & Marneweck 1996) and are therefore under an obligation to con- serve wetlands. The rehabilitation of wet- lands play an important role in wetland con- servation, as mentioned in the Ramsar con- vention. When rehabilitating wetlands it is important to understand wetland functions and to give the system time to react. Some rehabilitation projects may take up to 50 years before reha- bilitation has been accomplished (Middleton 1999; Mitsch & Wilson 1996). A wetland ecosystem is not a stable system, because many disturbances such as flood pulsing, fire and herbivory occur naturally in many wet- lands (Middleton 1999; Mitsch & Wilson 1996), especially in a country such as South Africa with its high frequency of thunder storms, fire-prone grasslands and large vari- ety of large herbivores. A restored wetland should be able to deal with these kinds of disturbances. Only a few peatlands have been rehabilitated in South Africa and information is limited. In 1995 it has been proposed that the Orange River Mouth salt marsh should be rehabili- tated (Marneweck 1995), but in 1998 almost no progress has been made and many prob- lems were experienced with the project (Dini 1998). Another similar project was the reha- bilitation of Blesbokspruit (Dini 1998). In 1996 the Free State Department of Environ- mental Affairs and Tourism and Rand Water started the rehabilitation of the Seekoeivlei as well as other wetlands in the north- east- ern Free State (Collins 1998). The rehabilita- tion of the Wilge River started as a Rand Water and Working for Water project in the same year (Rand Water & Working for Water Programme 1998). These projects take time and it is therefore difficult to determine if the projects have been successful. The Orange River Mouth, Blesbokspruit and Seekoeivlei are Ramsar sites (Cowan & Marneweck 1996). On the contrary, there is much infor- mation available on the rehabilitation of European peatlands, but those are complete- ly different ecosystems, which developed under very different climatic conditions. During peat mining operations in the past on Rietvlei Nature Reserve, ditches with sharp edges were constructed to drain the peatland. Some of the water was used for irrigation of farms in the area. There are four dolomite springs on the Reserve. The water from these springs is piped to the Rietvlei Water Works. A large amount of water was therefore drained from the peatland, which subse- quently became dry and resulted in the veg- etation being altered. Rehabilitation of the Rietvlei peatland start- ed as a "Working for Water" project. The aim of the rehabilitation project was mainly to rewet the peatland to allow hydrophytic veg- etation to re-establish. The sharp edges of the main channel were sloped and gabions were placed in the main channel to stop the peat from rapidly drying out and to allow flood- water to easily overspill onto the adjacent peatland, thus enhancing the rewetting process. The peat recovered from the sloping process was used to fill some of the smaller ditches. Soil and straw gabions were placed in the ditches to stabilise them and to retain the water. Rock filled gabions were placed in the main channel to slow the flow, increase the flooding frequency and duration and to promote the deposition of sediment. It was necessary to conduct a baseline vege- tation survey to determine the pioneer plant communities that established naturally on the rehabilitated peatland. The communities closer to the climax, that occur on areas with less disturbance, were also surveyed, to gain knowledge on the potential climax vegeta- tion. Study area The Rietvlei Dam Nature Reserve is located at about 25º50'S and 28º20'E. The reserve became established as a result of the Rietvlei Water Scheme to provide drinking water to the people of Pretoria. The Rietvlei Dam is Koedoe 46/1 (2003) 54 ISSN 0075-6458 venter.qxd 2005/12/09 10:34 Page 54 located in the northern portion of the reserve and the peatland is located upstream from the dam in the southern portion of the reserve. The City Council of Pretoria acquired the farm in 1929. The dam was built in the Ses Myl Spruit during the Great Depression and it was completed in 1934. The catchment area of the Ses Myl Spruit is to the south of Pretoria, towards Kempton Park. The area was declared the Rietvlei Game Reserve in 1937. In 1948 it became the Rietvlei Reserve for Game and indigenous Flora. In 1954 the area became the Van Riebeeck Nature Reserve and in 1992 the name was changed again to the Rietvlei Nature Reserve (Cul- ture and Recreation Department 1997). To drain the peatland, a deep ditch was dug through it, and this now forms part of the Ses Myl Spruit main channel. The main channel has been severely eroded and the water flows very fast, with high energy levels. The main channel and the peatland on the western side of the main channel have been rehabilitated. Certain portions of the peatland, on the east- ern side of the main channel, were exten- sively mined and almost all the peat was removed. This area has not been rehabilitat- ed. The underlying clay soil was exposed. On the western side of the main channel deep deposits of peat still remained intact, but they were severely disturbed by drainage ditches. The vegetation was disturbed during the construction of the ditches and the ditch- es altered the hydrological regime of the peatland. Methods The peatland area was stratified into the following units: ditches filled with peat; ditches filled with soil; sloped main channel edges; reed areas on old peat- deposits; and the mined area east of the main chan- nel. During the summer of 2001, 22 sample plots of 4 m x 4 m were placed randomly in these different units. The exact locality of each plot was recorded using a Global Positioning System (GPS). In each plot all plant species present were listed and each assigned the approriate Braun-Blanquet cover-abundance value (Werger 1974). Some aspects of the habitat were also noted such as soil type (peat or clay), degree of disturbance and rehabilitation measures. The floristic data were entered into the TURBOVEG data basis (Hennekens 1996a) and the data were sub- jected to classification and ordination procedures to identify plant communities. TWINSPAN (Hill 1979b) was used for the initial classification of the vegeta- tion, and the result was refined by using MEGATAB (Hennekens 1996b). The final classification is pre- sented in a phytosociological table. The procedure of Detrended Correspondence Analysis was performed by applying the DECORANA software (Hill 1979a). This ordination was used to indentify environmental gradients responsible for plant species distribution, and hence the occurrence of plant communities. To determine a probable change in vegetation (path of succession) after one year, the floristic survey was repeated during the summer of 2002 on the same sample plots as 2001. The data of the two surveys were pooled and to determine the direction of change in vegetation, the ordination was re-applied to the pooled data set. Results Classification The result of the classification is presented in the phytosociological table (Table 1). The classification of the plant communities found in the baseline survey (2001 data set) is as follows: 1. Amaranthus hibridus - Setaria ustilata Community on filled ditches. 1.1. Cynodon dactylon - Solanum sisym- brifolium Sub-community on soil filled ditch. 1.2. Persicaria species - Amaranthus hib- ridus Sub-community on peat filled ditch. 2. Phytolacca octandra - Solanum nigrum Wetland Community. 2.1. Phytolacca octandra - Datura stra- monium Disturbed Wetland Sub-com- munity. ISSN 0075-6458 55 Koedoe 46/1 (2003) venter.qxd 2005/12/09 10:34 Page 55 Koedoe 46/1 (2003) 56 ISSN 0075-6458 Table 1 Phytosociological table of pioneer vegetation on the rehabilitated peatland at Rietvlei Nature Reserve venter.qxd 2005/12/09 10:34 Page 56 ISSN 0075-6458 57 Koedoe 46/1 (2003) Table 1 (continued) The following species were encountered in the peat- land, but were not of any significant value to the phytosociological table Hyparrhenia hirta Setaria verticillata Alisma plantago-aquatica Schoenoplectus corymbosus Bidens formosa Panicum schinzii Hemarthria altissima Digitaria sanguinalis Askidiosperma albo-aristatum Ranunculus multifidus Cyperus eragrostis Sambucus nigra Helichrysum species Trifolium africanum Sisymbrium thellungii Pseudognaphalium species Xanthium strumarium 2.2. Phragmites australis - Chenopodium album Wetland Sub-community. 3. Cyperus species - Oenothera rosea Wet- land Community on clay. 3.1. Cyperus species - Paspalum dilata- tum Moist Wetland Sub-community on clay. 3.2. Typha capensis - Cyperus fastigiatus Wet Wetland Sub-community on clay. A hierarchical and habitat interpretation of the recognised plant communities is given in Fig. 1. Community description 1. Amaranthus hibridus - Setaria ustilata Community on filled ditches. The plant community occurs on the ditches that were filled with peat or soil during the rehabilitation of the peatland. The vegetation represents a pioneer stage, which established directly after the new disturbance caused by the rehabilitation. The vegetation is short, mostly below 0.5 m, and young. Some parts of the community have a dense vegetation (aerial) cover (80 %) while other parts have open patches with bare peat. The communi- ty is characterised by species group A. Persi- caria species is dominant and Amarathus hibridus and Setaria ustilata are conspicu- ously present. All these species are annual weeds, common in disturbed areas and are indicators of disturbance. A total of 38 species were noted in the community and an average of 14 species per relevé. 1.1. Cynodon dactylon - Solanum sisym- brifolium Sub-community on soil filled ditches. The sub-community is located on soil (not peat) filled ditches at the edge of the wet- land. This habitat is much drier that the rest of the wetland. The vegetation is open (about 30 % aerial cover) with large patches of bare soil surface visible. This sub-community is characterised by species group B. The stoloniferous perennial grass Cynodon dactylon is the dominant species and the annual weeds Solanum sisymbrifolium and Datura stramonium are conspicuous in this sub-community. Both these weeds occur in disturbed areas. Cynodon dactylon occurs in disturbed places on all soil types and is often found in damp areas (Van Oudtshoorn 1999). An average of 15 species per relevé and a total of 15 species were found in this sub- community. 1.2. Persicaria species - Amaranthus hib- ridus Sub-community on peat filled ditches. This sub-community is located on old drainage ditches filled with peat during the rehabilitation. The aerial cover of the vega- tion is about 50 %. Species group C charac- terises this sub-community and the dominant species is Persicaria. Furthermore Amaran- thus hibridus, Persicaria lapathifolia and Cyperus fastigiatus are also conspicuous. Phragmites australis is starting to establish within this sub-community. Persicaria lap- venter.qxd 2005/12/09 10:34 Page 57 athifolia is a weed that often occurs in wet areas and Amarathus hibridus is common in disturbed areas (Van Wyk & Malan 1988). A total of 32 species were noted in this sub- community with an average of 14 species per relevé. 2. Phytolacca octandra - Solanum nigrum Wetland Community. This is a weedy community on peat, proba- bly representing a further stage in the suc- cession. It is closer to the main channel and is moister than community 1. The communi- ty is characterised by species group D and shares species group F with community 1. The dominant species is Phytolacca octan- dra, which is a tall-growing annual weed (>2 m) restricted to disturbed areas (Van Wyk & Malan 1988). The community has a species diversity of 26 and an average of nine species per relevé. 2.1. Phytolacca octandra - Datura stramonium Disturbed Wetland Sub- community. The sub-community has been disturbed and the vegetation consists mainly of weeds. The vegetation is dense, with an aerial cover of almost 100 % and up to 2.5 m tall. This sub- community is characterised by the absence of species group E. The dominant species are Phytolacca octandra and Datura stramoni- um, while Persicaria lapathifolia and Solanum nigrum are also very conspicuous. Phytolacca octandra is a weed restricted to disturbed areas and Persicaria lapathifolia is a weed that often occurs in wet areas (Van Wyk & Malan 1988). The sub-community with 13 species is relatively poor in species Koedoe 46/1 (2003) 58 ISSN 0075-6458 Sub- community 1.1. 1 relevé Sub- community 1.2 6 relevés Sub- community 2.1 3 relevés Sub- community 2.2 6 relevés Clay soil Peat Weed dominated Phragmites dominated Rietvlei rehabilitated peatlands Filled ditches Disturbed area Drier area Wetter area Rehabilitated drained area Unrehabilitated mined area Sub- community 3.1 3 relevés Sub- community 3.2 3 relevés Community 1 Community 2 Community 3 Fig. 1. Dendrogram showing the hierarchy of TWINSPAN divisions for the vegetation data of the rehabili- tated peatlands on Rietvlei Nature Reserve on the 2001 dataset. venter.qxd 2005/12/09 10:34 Page 58 composition, probably due to the shading effect of the dominant species. Seven species on average were found in each relevé. 2.2. Phragmites australis - Chenopodium album Wetland Sub-community The sub-community represents a further suc- cessional stage, probably close to the reed dominated climax. It is located close to the main channel and is quite wet. Species group E characterises the sub-community. Phrag- mites australis is the dominant species and the weedy annuals Chenopodium album and Solanum nigrum are often present. Phytolac- ca octandra is present, but is relatively small in size in this sub-community, probably due to the competition from Phragmites aus- tralis. A total of 23 species were noted in this sub-community with an average of nine species per relevé. 3. Cyperus species - Oenothera rosea Wet- land Community on clay. This community is restricted to the eastern side of the main channel. The community is on a part of the wetland where the peat was mined extensively, and where the mined area is relatively flat without any drainage ditch- es. All peat was removed and the communi- ty is therefore on a clay soil. This area was not actively rehabilitated. Species group H characterises the community and the domi- nant species is Cyperus species. Oenothera rosea is a weed that occurs in moist dis- turbed areas and is an indicator of the past disturbance that occurred at the site (Van Wyk & Malan 1988). Only 14 species were recorded in this community with an average of six species per relevé. 3.1. Cyperus species - Paspalum dilata- tum Moist Wetland Sub-community on clay. This sub-community is drier than sub-com- munity 3.2, because is is on slightly higher ground, and the vegetation is shorter, mostly lower than 1 m. The sub-community is char- acterised by the absence of species group I and it is dominated by Cyperus species. Oenothera rosea and Cirsium vulgare are conspicuous in the vegetation. Paspalum dilatatum occurs mostly on clay and loam soil and in wet areas and is often a weed in disturbed areas (Van Oudtshoorn 1999). Cir- sium vulgare also occurs in moist disturbed areas (Van Wyk & Malan 1988). These species are indicators of the past disturbance, as well as the moist clayey soil. The sub- community has an average of six species in each relevé and a species diversity of only nine species. This is the sub-community with the lowest species diversity. 3.2. Typha capensis - Cyperus fastigiatus Wet Wetland Sub-community on clay. The sub-community occurs on moist clay soil and is located in a lower area of the wet- land. The vegetation is about 2 m tall. Species group I is characteristic of the sub- community and the dominant species is the perennial Typha capensis. Epilobium hirsu- tum, Persicaria lapathifolia, Cyperus sp., Cyperus fastigiatus and Oenothera rosea are conspicuously present. Typha capensis occurs in wet areas and Epilobium hirsutum occur in moist grassland and are often found in vlei areas (Van Wyk & Malan 1988). These species are indicators of the wet soil. The sub-community has 10 species and an average of seven species per relevé. Ordination In the ordination on the 2001 data set (Fig. 2), the separation of communities 1 and 2 on the drained, rehabilitated side of the channel and community 3 on the mined side of the channel is clear. Most of the relevès in a sub-community are close together but there are a few exeptions where the relevès are in a state of transition between two communi- ties. Although relevè 2 is still in Sub-com- munity 1.2 it is also close to Sub-community 2.2. It is therefore closer to the climax (Sub- community 2.2) than the other relevès in Sub-community 1.2. The environmental gra- dient from dry to wet can be seen in the ordi- nation as well as the gradients from the pio- neer community to the two different close- ISSN 0075-6458 59 Koedoe 46/1 (2003) venter.qxd 2005/12/09 10:34 Page 59 to-climax communities. These communities occur in the areas with less recent distur- bance and are more similar to climax vegeta- tion than the pioneer communities. The suc- cession of community 1 will be to either one of them. The one close-to-climax communi- ty should not change to become like the other close-to-climax community. Monitoring vegetation change The following is the result of the ordination as performed on the pooled data set for the specific purpose to monitor vegetation change from 2001 to 2002. The ordination (Fig. 3) indicates that the vegetation of sub- community 1.1 moved away (to the top left in the diagram) from the other communities. This is probably because it is situated at the edge of the wetland and has more terrestrial species than wetland species and is becom- ing more terrestrial, like the adjacent grass- land community. The vegetation of sub-community 1.2 changed (moved downwards in the diagram) in the direction of the of the reed-dominated community 2.2. This is probably an indica- tion of succession form a pioneer communi- ty towards the climax Phragmites australis dominated vegetation. The vegetation of Sub-community 2.1 stayed almost the same and although reeds are pre- sent it is dominated by the tall weed Phyto- lacca octandra. It does however share a lot of species with the reed-dominated sub-com- munity 2.2. Relevé 11 moved closer to 2.1 and it therefore seems that it has degraded, due to later disturbance by the floods. Sub-community 2.2 represents the close-to- climax vegetation dominated by Phragmites australis. This vegetation stayed almost the same, however, the vegetation of sample plots 14 and 15 seems to have degraded, and moved towards sub-community 1.2, which is an earlier successional stage. Community 3 stayed almost the same, but the vegetation at relevé 22 moved towards the more reed-dominated group. This may be because it is the only relevé in community 3 with Phragmites australis. Relevé 20 in community 3 was probably more disturbed Koedoe 46/1 (2003) 60 ISSN 0075-6458 Fig. 2. Scatter diagram of a DECORANA ordination illustrating the difference between the communities along an environmental gradient using the 2001 dataset. Axis 1 was plotted against Axis 2. venter.qxd 2005/12/09 10:34 Page 60 than the rest, because it is close to the reha- bilitation area and has been trampled. It moved closer to the rest of community 3. The two sub-communities in community 3 seem to become more similar, since it is more difficult to distinguish them from the ordination diagram. Discussion The baseline survey The first division of TWINSPAN on the 2001 baseline data separated the un-rehabilitated, mined areas and areas disturbed by the reha- bilitation. The rehabilitation disturbed the sites because of trampling, the construction of gabions and the movement of peat from one site to another. The mined area is on the eastern side of the main channel and the dis- turbed rehabilitated area is on the western side. These communities differ largely and have few species in common. These species are in species groups G and J and include Persicaria lapathifolia, Tagetus minuta and Cyperus fastigiatus, mostly pioneer, annual species. The DECORANA ordination diagram also shows significant separation between these plant communities. There are two com- munities on the western, rehabilitated, side of the main channel and each of these have two sub-communities. There is only one community on the eastern side, with two sub-communities. Each community and sub- community occurs on a particular habitat. Community 1 is on the filled ditches that were rehabilitated recently and the weedy pioneer plant species of the two sub-commu- nities are mostly the same. Most of the pio- neer species are exotic weeds. The vegeta- tion of sub-community 1.1 differs from 1.2, due to the dominance of the perennial stoloniferous grass Cynodon dactylon, while the annual weedy Solanum sisymbrifolium is very conspicuous in 1.1. Persicaria species and Amaranthus hibridus are more dominant in sub-community 1.2 and the annual grass Urochloa panicoides occurs in this sub-com- munity. Phragmites australis is becoming established in sub-community 1.2, but not in 1.1. The differences in the vegetation of the ISSN 0075-6458 61 Koedoe 46/1 (2003) Fig. 3. Scatter diagram of a DECORANA ordination illustrating the change of the vegetation of the commu- nities after one year using the pooled dataset of the 2001 and 2002 data. Axis 1 was plotted against Axis 2. venter.qxd 2005/12/09 10:34 Page 61 two sub-communities are probably a result of the difference in soil. Sub-community 1.1 is on relatively dry clay and sub-community 1.2 on moist peat. The two sub-communities of community 2 differ in the dominant vegetation and proba- bly the degree of disturbance. The vegetation of sub-community 2.1 consists mainly of tall growing weeds, mostly Phytolacca octan- dra. The vegetation of sub-community 2.2 is dominated by Phragmites australis which includes the older, well developed stands, probably closer to the climax vegetation, as well as the recently sloped area next to the river. The older and pioneer sub-communi- ties are floristically therefore combined in a single community. Sub-community 2.2 occurs on both peat and clay. It seems that a community completely different from the filled ditches (community 2.1) is therefore developing on the sloped area (part of com- munity 2.2). The difference in disturbance may be responsible for the difference in sub- communities 2.1 and 2.2. Another possibili- ty may be that they are at different succes- sional stages, or moving towards different new climaxes. Reeds were established on the sloped areas before and the reeds are grow- ing back rapidly. This may explain the sepa- ration of community 2.2 from community 1. Community 3 on the eastern side of the main channel is completely different from the communities on the western side. The area was mined and the peat removed and not rehabilitated. The community occurs on exposed clay, that was previously underlying the peat. The community that established is dominated by Cyperus species. This may be an example of a climax, or close to climax, community dominated by Cyperus and Typha. The wetter (slightly lower) sub-com- munity (3.2) is dominated by Typha capensis and the drier sub-community (3.1) is domi- nated by Cyperus species. There are very few general species. Commu- nities 1 and 2 share some species, but they do not share many species with community 3. Community 1 has the highest species rich- ness and community 3 has the lowest species richness. The pioneer communities therefore contribute more to species diversity than the close-to-climax communities, which are dominated by tall groups of reeds or sedges, with few other species present. Community 3 is already stable and there is probably more competition between dominant species, while community 1 is a pioneer community with many weeds and open spaces for plants to establish. Few individuals of these weeds occur in the established communities and they should disappear in time. In contrast, the flood regime of the wetland may cause sufficient disturbance for the weedy species to persist in the pioneer communities for some time. Wetland species are adapted to these disturbances, but they need time to establish in a disturbed wetland and the flooding regime still need to stabilise. Vegetation change The study was conducted over a short period with only two data sets one year apart. This is important to take into consideration, since wetlands take a long time to rehabilitate. The study is at the start of rehabilitation and it is difficult to predict what the vegetation will look like after a few years. This study will hopefully give us some indication. After the flooding disturbance at the end of the year, that destroyed most of the pioneer vegetation, the peat was wetter. This flood- ing was caused by the rehabilitation mea- sures. It seems that the rehabilitation was successful and that succession is taking place towards the climax vegetation, even after only a single year. Sub-community 2.1 may be a problem, because it does not seem to advance towards a reed-dominated commu- nity, but stays the same. This is a problem because this community are dominated by weeds. It would be interesting to see if this community would change over a longer peri- od of time. Further monitoring would con- firm whether the changes in vegetation is of a permanent nature, or whether the vegeta- tion is merely fluctuating due to yearly changes in the moisture regime. The mois- ture regime is changing due to the rehabili- Koedoe 46/1 (2003) 62 ISSN 0075-6458 venter.qxd 2005/12/09 10:34 Page 62 taion, but yearly fluctuations in the amount of rainfall also plays a role. Although it seems as if the peatland is recovering the time frame of the study is to short to confirm this as a fact. Other disturbances in the peatland are graz- ing, by the animals occuring in the reserve as well as trampling by the buffalo. Any of the disturbances could have caused the degener- ation of some of the relevés, for example relevé 15. Acknowledgements I would like to thank the University of Pretoria for funding and the use of equipment, and the manage- ment of Rietvlei Nature Reserve for allowing the study on the reserve. References BLOEM, K.J., G.K. THERON & N. VAN ROOYEN. 1993. Wetland plant communities of the Verlorenvalei Nature Reserve in the North-eastern Sandy Highveld, Transvaal. South African Journal of Botany 59: 281-286. COLLINS, N. 1998. Joint venture implemented between Free State Department of Environmen- tal Affairs and Tourism and Rand Water. South African Wetlands. Newsletter on activities relat- ing to the Ramsar Convention in South Africa 9: 5. COWAN, G.I. & G.C. MARNEWECK. 1996. South African National Report to the Ramsar Conven- tion 1996. Pretoria: Department of Environmen- tal Affairs and Tourism. CULTURE AND RECREATION DEPARTMENT. 1997. Rietvlei Nature Reserve. Pretoria: City Council of Pretoria. DINI, J. 1998. Montreux Record update. South African Wetlands. Newsletter on activities relat- ing to the Ramsar Convention in South Africa 9: 8. ECKHARDT, H.G., N. VAN ROOYEN & G.J. BRE- DENKAMP. 1993. Wetland plant communities of the Vrede-Memel-Warden area, northeastern Orange Free State. Navorsinge van die Nasion- ale Museum, Bloemfontein 9: 245-262. EHRENFELD, J.G. 2000. Defining the Limits of Restoration: The Need for Realistic Goals. Restoration Ecology 8(1): 2-9. HENNEKENS, S.M. 1996a. TURBO(VEG): software package for input, processing, and presentation of phytosociological data. User's guide. Version July 1996. Wageningen: IBN-DLO. HENNEKENS, S.M. 1996b. MEGATAB: a visual editor for phytosociological data. User's guide. Ver- sion October 1996. Wageningen: IBN-DLO. HEY, D.L. & N.S. PHILIPPI. 1999. A case for wetland restoration. New York: John Wiley. HILL, M.O. 1979a. DECORANA - A FORTRAN program for detrended correspondence analysis and reci- procal averaging. Ithaca, New York: Cornell University. HILL, M.O. 1979b. TWINSPAN - A FORTRAN program for arranging multivariate data in a ordered two-way table by classification of individuals and attributes. Ithaca, New York: Cornell Uni- versity. MARNEWECK, G.J. 1995. A first for South Africa. Joining efforts to manage and rehabilitate the first transborder Ramsar site. South African Wet- lands. Newsletter on activities relating to the Ramsar Convention in South Africa 5: 1. MIDDLETON, B. 1999. Wetland restoration. Flood pulsing and disturbance dynamics. New York: John Wiley. MITSCH, W.J. & R.F. WILSON. 1996. Improving the success of wetland creation and restoration with know-how, time, and self-design. Ecological Applications 6(1): 77-83. MYBURGH, W.J., P.J.J. BREYTENBACH, G.K. THERON & G.J. BREDENKAMP. 1995. Die fitososiologie van die vleie in die Grootvlei-omgewing, Suid- Transvaal. Suid-Afrikaanse Tydskrif vir Weten- skap en Tegnologie 14(2): 48-54. RAND WATER SCIENTIFIC SERVICES. 1998. The Socio- Econnomic Value of Wetlands in Highly Indus- trialized Catchments. Development of a Pro- gramme for the Klip River Catchment 2: 1. (Unpublished). RAND WATER & WORDING FOR WATER PROGRAMME. 1998. Wetland Rehabilitation Programme for the Wilge River. Harrismith: Department of Environmental Affairs & Tourism, Free State Conservation. SMIT, C.M., G.J. BREDENKAMP & N. VAN ROOYEN. 1995. The vegetation of the upper Klip River Valley in the north-eastern Orange Free State. Navorsinge van die Nasionale Museum, Bloem- fontein 11: 37-58. VAN OUDTSHOORN, F. 1999. Guide to grasses of southern Africa. Pretoria: Briza. VAN WYK, B. & S. MALAN. 1988. Veldgids tot die veldblomme van die Witwatersrand- & Pretoria- Gebied, insluitend Magaliesberg & Suiker- bosrand. Kaastad: Struik. WERGER, M.J.A. 1974. On concepts and techniques applied in the Zürich-Montpellier method of vegetation survey. Bothalia 11(3): 309-32. ISSN 0075-6458 63 Koedoe 46/1 (2003) venter.qxd 2005/12/09 10:34 Page 63 << /ASCII85EncodePages false /AllowTransparency false /AutoPositionEPSFiles true /AutoRotatePages /None /Binding /Left /CalGrayProfile (Dot Gain 20%) /CalRGBProfile (sRGB IEC61966-2.1) /CalCMYKProfile (U.S. Web Coated \050SWOP\051 v2) /sRGBProfile (sRGB IEC61966-2.1) /CannotEmbedFontPolicy /Error /CompatibilityLevel 1.4 /CompressObjects /Tags /CompressPages true /ConvertImagesToIndexed true /PassThroughJPEGImages true /CreateJDFFile false /CreateJobTicket false /DefaultRenderingIntent /Default /DetectBlends true /ColorConversionStrategy /LeaveColorUnchanged /DoThumbnails false /EmbedAllFonts true /EmbedJobOptions true /DSCReportingLevel 0 /EmitDSCWarnings false /EndPage -1 /ImageMemory 1048576 /LockDistillerParams false /MaxSubsetPct 100 /Optimize true /OPM 1 /ParseDSCComments true /ParseDSCCommentsForDocInfo true /PreserveCopyPage true /PreserveEPSInfo true /PreserveHalftoneInfo false /PreserveOPIComments false /PreserveOverprintSettings true /StartPage 1 /SubsetFonts true /TransferFunctionInfo /Apply /UCRandBGInfo /Preserve /UsePrologue false /ColorSettingsFile () /AlwaysEmbed [ true ] /NeverEmbed [ true ] /AntiAliasColorImages false /DownsampleColorImages true /ColorImageDownsampleType /Bicubic /ColorImageResolution 300 /ColorImageDepth -1 /ColorImageDownsampleThreshold 1.50000 /EncodeColorImages true /ColorImageFilter /DCTEncode /AutoFilterColorImages true /ColorImageAutoFilterStrategy /JPEG /ColorACSImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /ColorImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /JPEG2000ColorACSImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /JPEG2000ColorImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /AntiAliasGrayImages false /DownsampleGrayImages true /GrayImageDownsampleType /Bicubic /GrayImageResolution 300 /GrayImageDepth -1 /GrayImageDownsampleThreshold 1.50000 /EncodeGrayImages true /GrayImageFilter /DCTEncode /AutoFilterGrayImages true /GrayImageAutoFilterStrategy /JPEG /GrayACSImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /GrayImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /JPEG2000GrayACSImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /JPEG2000GrayImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /AntiAliasMonoImages false /DownsampleMonoImages true /MonoImageDownsampleType /Bicubic /MonoImageResolution 1200 /MonoImageDepth -1 /MonoImageDownsampleThreshold 1.50000 /EncodeMonoImages true /MonoImageFilter /CCITTFaxEncode /MonoImageDict << /K -1 >> /AllowPSXObjects false /PDFX1aCheck false /PDFX3Check false /PDFXCompliantPDFOnly false /PDFXNoTrimBoxError true /PDFXTrimBoxToMediaBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXSetBleedBoxToMediaBox true /PDFXBleedBoxToTrimBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXOutputIntentProfile () /PDFXOutputCondition () /PDFXRegistryName (http://www.color.org) /PDFXTrapped /Unknown /Description << /ENU (Use these settings to create PDF documents with higher image resolution for high quality pre-press printing. The PDF documents can be opened with Acrobat and Reader 5.0 and later. These settings require font embedding.) /JPN /FRA /DEU /PTB /DAN /NLD /ESP /SUO /ITA /NOR /SVE >> >> setdistillerparams << /HWResolution [2400 2400] /PageSize [612.000 792.000] >> setpagedevice