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South African Journal of Botany 74 (2008) 401–411 www.elsevier.com/locate/sajb

Description of reference conditions for restoration projects of riparian vegetation from the species-rich biome ⁎ E.J.J. Sieben a, , M.K. Reinecke b

a Department of Botany, University of , Private Bag X1, Matieland 7602, b Ecologic Environmental Consulting cc, PO Box 16386, Vlaeberg 8018, , South Africa Received 27 July 2007; accepted 22 January 2008

Abstract

When considering revegetation strategies for particular restoration projects, data on community composition and structure should, whenever possible, be obtained from reference sites. Revegetation is an important restoration strategy especially since riverbanks that have been cleared of alien vegetation are extremely susceptible to erosion. The presence of lateral zonation in riparian vegetation is well documented: flooding events shape the vegetation on riverbanks and the zones that are inundated annually have different vegetation than those that are inundated interannually. This can be referred to as the demerse ecotope, or Wet Bank, and the emerse ecotope, or Dry Bank, and these zones can also be further subdivided. There is a need for species descriptions from undisturbed riparian zones to guide post-project appraisal and revegetation strategies, especially in areas with high species turnover like the fynbos biome. Braun–Blanquet vegetation belt transects were sampled on five undisturbed rivers that originate in the Hottentots Holland mountain range. Relevés were sampled from as many Wet Bank and Dry Bank subzones as were present in each case. Twenty-six riparian communities were recognized, which were clustered into ten community Groups based on physical bank attributes. The most dominant species for each of these community types have been listed in a synoptic table that can be used for revegetation purposes. It is recommended that revegetation plans make use of a mixture of the listed species, whilst maintaining separation of Wet and Dry Bank species. Prior to species selection, it is necessary to assess the range of riparian habitats available in the project reach. Though revegetation is more expensive than allowing for natural recruitment, recent evidence has shown that recovery of the natural vegetation without intervention may be limited, and not without risks. Revegetation may be a cheaper strategy in the long term, avoiding the maintenance costs that are required to stabilize banks and to remove re-invading alien species. © 2008 SAAB. Published by Elsevier B.V. All rights reserved.

Keywords: Alien clearing; Mountain streams; Revegetation; Riverbanks

1. Introduction slows down turbulent floods, consumes water and adds to species and habitat diversity (Kopecky, 1963; Rogers and Van Currently most rivers in the are dammed in at der Zel, 1989; Birkhead et al., 1996). The role of riparian least one place and few experience natural flood regimes. This vegetation in bank stability is of particular importance, has an impact on vegetation and currently it is only in the higher especially following the clearing of riparian alien vegetation, reaches, the mountain streams, that riparian vegetation is found and exacerbation of bank erosion that delivers more sediment in a more or less natural state (King et al., 1979; Davies and downstream. Revegetation strategies can ameliorate the pro- Day, 1998). Riparian vegetation plays a very important role in blems, to some extent, that occur after alien are cleared the functioning of riverine ecosystems: it prohibits erosion, and also decrease the site's susceptibility to new invasions. Reference sites provide necessary data to guide such revegeta- ⁎ tion strategies (Davy, 2002). Corresponding author. Present address: Department of Sciences, Univ- ‘ ’ ‘ ersity of the Free State, Qwaqwa Campus, Private Bag X13, Phuthaditjhaba 9866, The term restoration is often defined as the re-establish- South Africa. ment of pre-disturbance ecological functions and related phys- E-mail address: [email protected] (E.J.J. Sieben). ical, chemical, and biological characteristics’ (Palmer et al.,

0254-6299/$ - see front matter © 2008 SAAB. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.sajb.2008.01.176 402 E.J.J. Sieben, M.K. Reinecke / South African Journal of Botany 74 (2008) 401–411

2006). The difficulty or impossibility of achieving restoration is and Johnson, 1999). For rehabilitation work, it is mostly im- widely recognised largely due to difficulties with the pre- portant to distinguish between the lateral zones that are disturbance state and its use in goal setting. Lockwood and inundated annually and those that are inundated interannually. Pimm (1999) recognize several levels of ambition of restoration The first zone is referred to as the demerse ecotope (also called practitioners and recognize that it is not always necessary to Wet Bank), and the second as emerse ecotope (also called Dry restore the exact natural species composition. Restoration of Bank), based on Kopecky (1969) and Mucina et al. (2006).Wet functional characteristics is in many cases feasible even if the Banks and Dry Banks contain distinct vegetation types in any species composition in the natural state is unknown. Since particular site and the border between them is often quite sharp. ecosystems are naturally dynamic, restoration targets should not A previous study of riparian reference sites in the Western always be set in terms of static species composition or structural Cape by Prins et al. (2004) only considered the vegetation attributes of a past state. Other reasons why such ‘rigid’ re- within single “riparian bands” and did not consider riparian storation targets are sometimes not effective are the irreversi- zonation. The aim of this present study is to describe the veg- bility of some system changes (Pickett and Parker, 1994) and a etation zonation and communities of riparian sites along five lack of sufficient data to recreate this past state (Hobbs and mountain streams in the Hottentots Holland Nature Reserve, Harris, 2001). These issues apply specifically to the restoration and to assess how useful the described vegetation patterns are of rivers (Downs et al., 2002). for revegetation practice. Rivers, especially mountain streams, are dynamic ecosys- tems with extremely heterogeneous and patchy habitats (Downs 2. Study area et al., 2002). Western Cape rivers, in particular, have a large turnover of species among different catchments (King and This study focused on the riparian vegetation of moun- Schael, 2001; Reinecke et al., 2007). These papers introduce the tain streams in the Hottentots Holland Nature Reserve, situ- concept of ‘catchment signatures’: mountain stream and foothill ated between Stellenbosch, Franschhoek, and sites within one catchment are more similar to each other than to Grabouw in the Western Cape. This area has the highest rainfall other mountain stream or foothill sites respectively, when it in the Western Cape. Five different rivers originate here: 1) the comes to the species composition of riparian plants or macro- Berg River that flows north through the West Coast forelands; invertebrates. These findings complicate the role of reference 2) the Riviersonderend River that flows east through the sites in restoration projects and their use in post-project ap- Overberg Region, and joins the Breede River near Swellendam; praisal, since it cannot always be assumed that rivers within a 3) the Palmiet River that flows southwards through the specific catchment are similar (Reinecke et al., 2007). Kogelberg State Forest; 4) the Eerste River that flows west The correlation between natural species composition and through Stellenbosch towards the coast and 5) the ecosystem functioning can be studied in nearby reference sites Lourens River that flows south-west via Somerset West directly located in an ecological setting that is similar to the site that is into False Bay (Fig. 1). The Hottentots Holland Nature Reserve being restored. There are, however, some requirements for the is a biodiversity hotspot within the fynbos biome (Boucher, use of reference sites. Firstly, a restoration plan should be based 1978; Cowling et al., 1992) and was selected as a case study on more than just one reference site, since one site cannot because of the high rainfall, the high diversity of plant species display the essence of naturally functioning systems in which and variety of riverine habitat. many different community compositions are possible. Sec- ondly, the restoration should not be seen as a single discrete 3. Methods event towards the restoration target, but rather as a step on the way, after which the need for monitoring and adjusting remains Reference conditions of riparian vegetation have been de- (Pickett and Parker, 1994). scribed by using vegetation relevés. The structure and species Western Cape riparian vegetation has been described rather composition of the communities described can serve as generally by Campbell (1986), Kruger (1978), Mucina et al. (2006) and Taylor (1978). The scrub vegetation of riparian sites was described by Taylor (1978) and Campbell (1986) as ‘Closed-scrub Fynbos’ and consists mainly of tall shrubs such as Brachylaena neriifolia and Metrosideros angustifolia. This is, however, not the only vegetation type found in riparian areas and riparian vegetation types range from forest to tall herbland (Kruger, 1978; Mucina et al., 2006). If the knowledge of veg- etation patterns is to be applied in restoration ecology in the form of reference sites, the data to be used needs to display a greater level of detail. A description of riparian vegetation that is useful for ref- Fig. 1. Transect blocks sampled depicting lateral zonation of riparian vegetation. erence sites has to take into account the specific zonation pat- The relevé area is variable, being dependent on the local width of each riparian terns that result from the flood regime in the stream (Kopecky, zone. The total length of the transect is also variable, depending on the width and 1969; Hupp and Osterkamp, 1985; Glavaç et al., 1992; Dixon number of each riparian zone. E.J.J. Sieben, M.K. Reinecke / South African Journal of Botany 74 (2008) 401–411 403

Table 1 transect, several more or less homogeneous vegetation zones Number of transects and relevés in each river catchment were recognized and sampled separately. The width of the Catchment No. of transects No. of relevés vegetation zone varied in the field but the length was Eerste River 21 50 consistently 10 m, so that a representative stretch of riverbank Berg River 19 42 could be sampled. The relevé areas for each vegetation zone Riviersonderend River 28 82 varied depending upon the lateral width of each zone up the Paalmiet River 14 38 bank: plot sizes ranged from 2 m2 in a narrow Wet Bank zone, Lourens River 11 17 2 Total: 93 229 up to 100 m in a riparian forest or a broad Dry Bank zone. Many transects contained more than one Wet or Dry Bank zone. These relevé areas match those recommended by Tüxen (1970) guidelines for species to be used in revegetation trials. Veg- for different structural vegetation types (see also Westhoff and etation relevés were laid out in transects across the riverbanks Van der Maarel, 1973). In every vegetation relevé, a full survey from the Aquatic zone up to the Dry Bank zone (Fig. 1). In each of all species was recorded together with an estimate of cover-

Fig. 2. Location of the study area and the location of riparian transects along the rivers. Each number indicates a separate transect. Transects are located in order to represent the maximum geographical spread and the maximum variation in vegetation types. 404 E.J.J. Sieben, M.K. Reinecke / South African Journal of Botany 74 (2008) 401–411 abundance. The sampling followed the Braun–Blanquet meth- Table 2 od (Westhoff and Van der Maarel, 1973). Proposed classification of riverine vegetation of the Hottentots Holland Mountains A total of 93 transects were laid out across riverbanks in the Community Group 1: Aquatic communities Hottentots Holland Mountains, resulting in a database of 229 Ass. 1.1: Fontinali antipyreticae–Isolepidetum digitata – vegetation relevés (Table 1). The number of relevés per transect Ass. 1.2: Pentaschistido capensis Isolepidetum digiatatae Community Group 2: Pioneer Wet Banks was not always equal; when banks were very heterogeneous, this Comm. 2.1: Symphyogyna podophylla–Sematophyllum dregei Moss Community resulted in extra relevés, whereas sometimes specific vegetation Comm. 2.2: Brachylaena neriifolia–Metrosideros angustifolia Pioneer Community zones were absent (for example, when there was no vegetation Community Group 3: Erosion Wet Banks growing in the Aquatic zone). Vegetation transects were located in Ass. 3.1: Symphyogyno podophyllae–Schizietum tenellae – such a way that they had maximal geographical spread within the Ass. 3.2: Sphagno capensis Disetum tripetaloidis Ass. 3.3: Pseudobaeckeo africanae–Prionietum serrate area, but at the same time, rare vegetation types that were unique Community Group 4: Deposition Wet Banks were sampled additionally to improve their characterization Ass. 4.1: Wimmerello bifidae–Juncetum lomatophylli (Fig. 2). The aim was that every described vegetation type should Community Group 5: Ericaceous Fynbos be based on at least four relevés. This was not always possible, so Comm. 5.1: Ischyrolepis triflora– grandiceps Closed Shrubland – that some ‘provisional’ types have been described as well. Comm. 5.2: Nebelia fragarioides Staberoha cernua Short Closed Shrubland Ass. 5.3: Erico longifoliae–Tetrarietum crassae The vegetation database was sorted using TWINSPAN (Hill, Ass. 5.4: Cliffortio atratae–Restionetum purpurascentis 1979), but improvements on the initial classification were made Subass. 5.4a: typicum by manual tabulation, using the criteria in Feoli and Orloci (1985) Subass. 5.4b: Centelletosum erianthae to cluster the presence and absence of species into blocks. The Ass. 5.5: Restio purpurascenti–Cliffortietum hirsutae clusters formed were named according to the International Code Community Group 6: Transitional Fynbos Comm. 6.1: Elegia capensis–Cliffortia hirsuta Tall Closed Shrubland of Syntaxonomic Nomenclature of Weber et al. (2000),ifthey Ass. 6.2: Muraltio heisteriae–Ericetum pineae were based upon at least four relevés. Community names for local Comm. 6.3: Haplocarpha lanata–Euryops abrotanifolius Closed Shrubland use (for example by managers) were based on the vegetation Community Group 7: Asteraceous Fynbos structure and the names of two important species (Edwards, 1983) Ass. 7.1: Wahlenbergio parvifoliae–Pentameritetum thuarii – and have been given to all the communities described. Ass. 7.2: Helichryso cymosi Myrsinietum africanae Subass. 7.2a: Ficinietosum acuminatae Subass. 7.2b: inops 4. Results Subcomm. 7.2c: Cullumia setosia Variant Ass. 7.3: Pelargonio tomentosi–Chasmanthetum aethiopicae Twenty-six riparian communities were recognized together Community Group 8: Cliffortia odorata dominated Shrublands – with five subcommunities and have been clustered into ten Ass. 8.1: Pteridio aquilini Cliffortietum odoratae Comm. 8.2: Rubus rigidus–Cliffortia odorata Shrubland different Community Groups (Table 2). A detailed description of Community Group 9: Afromontane Forests these communities is already presented in Sieben (2003),and Comm. 9.1: Platylophus trifoliatus– Forest hence not included here (see Discussion). Species considered Ass. 9.2: Platylophietum trifoliate important for revegetation are those consistently found in a Ass. 9.3: Curtisio dentatae–Diospyretum whyteanae – particular vegetation type at a sufficiently dominant cover, namely Ass. 9.4: Todeo barbarae Cunonietum capensis Subass. 9.4a: typicum a frequency of at least 40% within a community and a minimum Subass. 9.4b: Hymenophylletosum peltatae average cover of 10% (Table 3). Some of the communities are not Community Group 10: Riparian Scrub suitable as reference sites, such as Aquatic and Pioneer com- Ass. 10.1: Ischyrolepido subverticillatae–Metrosiderotetum angustifoliae munities, but are included for the sake of completeness. Subass. 10.1a: Podalyrietosum calyptratae Vegetation data is provided, together with the situations in Subass. 10.1b: typicum which specific vegetation types may be expected. The soils Syntaxa recognized as associations (Ass) or subassociations (Subass) are indi- adjacent to mountain streams are poorly developed and contain cated as are the communities (Comm or Subcomm) of which the hierarchical status was not recognized. a high proportion of rocks. In many instances, the topsoil is completely washed away and the banks consist entirely of bed- rock, boulders and large cobbles. The best-developed (deepest) ficult. Further stresses include shading from trees and water poor soils are found higher up the bank, away from the water's edge, in nutrients. Few plants are adapted to these extreme conditions. on the Dry Bank. Deeper soils, normally of the Oakleaf, The aquatic communities are differentiated by only two species: Glenrosa or Fernwood Forms, are associated with forests, shale- Isolepis digitata and the exotic moss Fontinalis antipyretica. bands, seepage areas and floodplains. In most riparian sites, however, soils are very shallow overlaying bedrock or boulders 4.2. Community Group 2: pioneer wetbanks and belong to the Mispah Form. This Community Group consists largely of pioneer commu- 4.1. Community Group 1: aquatic communities nities that occur under severe stress. The banks are erosion dominated resulting in a rocky substratum, which perpetuates Aquatic communities in mountain streams must survive the the ‘pioneer’ or early successional character of this community. stresses of high stream velocities and dynamically changing sub- Ferns and seedlings of riparian shrubs and trees are the only strata. These conditions make rooting by young seedlings dif- higher plant species that occur here. Characteristic species for E.J.J. Sieben, M.K. Reinecke / South African Journal of Botany 74 (2008) 401–411 405

Table 3 Synoptic table of riparian vegetation in the Hottentots Holland Mountains indicating species suitable for use in revegetation

(continued on next page) 406 E.J.J. Sieben, M.K. Reinecke / South African Journal of Botany 74 (2008) 401–411

Table 3 (continued)

As an example: the occurrence of Schizaea tenella as V5 means that the species occurs in 81–100% of the plots, with a typical (average) cover of 5–12.5%. E.J.J. Sieben, M.K. Reinecke / South African Journal of Botany 74 (2008) 401–411 407 this Community Group are Blechnum capense, M. angustifolia Campbell (1986) classifies all these types in the Nuweberg and several moss species. The vegetation is sparse and limited Mesic Ericaceous Fynbos. The five communities described to those areas where small pockets of soil persist between rocks. below all occur on shallow acid soils of medium-textured sands derived from Group sandstones, but differ in 4.3. Community Group 3: erosion wetbanks other respects. Community 5.1 is represented by only two relevés from high altitude ephemeral rivers on the steep slopes These Wet Bank vegetation types occur on banks where erosion of the Lourens River catchment and community 5.2 is found predominates. They form the more consistent Wet Bank commu- only at high altitudes on the Palmiet River system. Associations nities that occur in sheltered places on the riverbanks, where small 5.3 and 5.4 are the most important communities, association 5.3 pockets of soil are protected from washing away. There is often an being present at altitudes higher than 700 m and association 5.4 Upper Wet Bank and a Lower Wet Bank Zone present. The Lower common on altitudes below that. Association 5.5 occurs where Wet Bank occurs as a narrow strip along the waterlevel and also in seepage flows down the valley slope and into the river. Com- small pockets within the Upper Wet Bank Zone. It may be ignored munities 5.2 and 5.3 are structurally low vegetation types with when dealing with revegetation issues due to its small scale and its few species taller than 50 cm. On the other hand, community 5.5 scattered occurrence. Palmiet (Prionium serratum)occursonthe is a very tall community. All of these communities are rich in Upper Wet Bank with several shrubs (Erica lutea, Penaea cneorum typical fynbos elements and consist of a mixture of riparian and Pseudobaeckea africana) growing in and amongst rocks and species and upland fynbos species. boulders on the riverbank. These species play an extremely important role in bank stability. 4.6. Community Group 6: Transitional Fynbos Two Lower Wet Bank types (Associations 3.1 and 3.2) and one Upper Wet Bank type (Association 3.3) are recognized. For Three communities are transitional between the Ericaceous revegetation work, it is recommended that a mixture of species Fynbos of Community Group 5 and the Asteraceous Fynbos from all these associations be used since they tend to occur in a of Community Group 7, of which one type was sufficiently mosaic with one another. sampled for use as a restoration target. Community 6.2 is tran- sitional between the Ericaceous Fynbos communities and the 4.4. Community Group 4: deposition wetbanks Riparian Scrub communities of Community Group 10. It is structurally similar to the Helichryso-Myrsinietum africanae This Community Group consists of only one Deposition Wet of Community Group 7 but contains many elements of the Bank community. It was found in the Foothill Zone where de- Ericaceous Fynbos group. There is a dense herb layer present, position of sediment is more prominent forming lateral bars of with characteristic species Erica nudiflora, E. pinea and Elegia sand or cobble, with little canopy cover. The vegetation mainly asperiflora, covering more than 70%, as well as a shrub layer consists of sedges, with some Restionaceae and grasses. On with stellatifolium, L. xanthoconus (dominant), M. cobble bars, there is hardly any vegetation. On the broad sandy angustifolia and Podalyria calyptrata. The shrub layer covers beaches, some zonation occurs: Isolepis prolifer grows at the on average 30% of a relevé and ranges in height from 1.5 to water's edge trapping finer sediment that is colonized by Juncus 3.0 m. The herb layer also contains some tall species, especially lomatophyllus at elevations a few centimetres higher. Higher up Restionaceae, like Cannomois virgata, Restio dispar and Pla- the bank Calopsis paniculata, Pennisetum macrourum and tycaulos callistachyus, which grow to 1.5 m tall. Pentameris thuarii are found. These gramminoids occur to- In the Hottentots Holland Mountains, community 6 was gether with several juveniles of the shrubs B. neriifolia and found in the north, at Jan Joubertsgat in the Riviersonderend Morella serrata. River catchment. The deep mineral soils have a relatively high pH between 4.5 and 5.0, which contrast starkly with the neigh- 4.5. Community Group 5: Ericaceous Fynbos bouring community on the stony Wet Bank.

The Communities of Groups 5, 6 and 7 are typical Dry Bank 4.7. Community Group 7: Asteraceous Fynbos communities and they contain a large terrestrial element. Since they share many species with the surrounding fynbos, they are This Community Group consists of Asteraceous Fynbos, very rich in species. Vegetation height ranges from dwarf shrubs where ‘typical’ fynbos elements like ericas, restios and 0.5 m in height to shrubs up to 3.0 m in height, with total are less pronounced: the only important erica species is Erica vegetation cover always more than 70%. Erica hispidula occurs hirta. In their place, many species of Asteraceae, ferns and in all these communities and is shared with Asteraceous Fynbos sedges occur. Asteraceous Fynbos is distinctly taller than most (Community Group 7) and with the Upper Wet Bank Zones Ericaceous Fynbos types. These communities occur on yellow, (Community Group 3). The following important species are plinthic soils found on granites or shale; mostly on the western shared with the Upper Wet Bank community of Community side of the mountain range and in Assegaaiboschkloof. They are Group 3: P. cneorum, E. lutea, Berzelia squarrosa and Restio similar to the Talus Asteraceous Fynbos or Waboomveld de- purpurascens. The shrubs xanthoconus and scribed by Campbell (1986). Brunia alopecuroides are shared with Transitional Fynbos This Community Group shares many species with forest and (Community Group 6). scrub, namely: Asparagus scandens, Blechnum punctulatum, 408 E.J.J. Sieben, M.K. Reinecke / South African Journal of Botany 74 (2008) 401–411

Halleria elliptica, Ischyrolepis gaudichaudiana, Myrsine afri- prevalent scrub layer. Two shrub species characteristic of this cana and Pteridium aquilinum. The only tree that typically occurs association are Erica caffra and M. angustifolia. There are two outside of the forest, oleoides, is regularly found in subassociations: one dominated by M. angustifolia and the these communities while another, Cassine schinoides,isrestricted other with B. neriifolia and M. angustifolia co-dominant. Scrub to the lower shrub stratum. Community 7.1 is dominated by the communities generally occur downstream of riparian forest. grass P. thuarii, probably as a result of the sites’ fire history. They are poor in species and most of these species are widely Community 7.2 is the most common vegetation type found on distributed across Western Cape riverine habitats. (Boucher, granite substrates and it occurs with two subassociations and one 1978; Taylor, 1996). poorly-described variant. Community 7.3 is an extremely species- rich community known only from Malmesbury Shales in the 5. Discussion western part of the mountain range. Rivers have a very high ‘self-designing capacity’ (Mitsch 4.8. Community Group 8: Cliffortia odorata shrublands and Wilson, 1996; Downs et al., 2002) as new habitat is continually re-created through stochastic disturbance events. These communities are nearly monospecific due to dom- Bare riverbanks, left to revegetate naturally following alien inance by C. odorata. This tall herb can grow up to 2.0 m tall clearing, are unstable and prone to bank collapse and excessive forming a dense bush as lower leaves die off. Strong com- erosion. Vegetation plays an important role in preventing ex- petitors such as P. aquilinum and Rhus angustifolia co-occur. cessive erosion, but erosion is a natural element in a river Of the two communities in this group, only Association 8.1 ecosystem and is an important element in the ‘self-designing is useful as a restoration target, since Community 8.2 is only capacity’ of rivers. It is recommended that revegetation plans known from a single relevé. The former was found on make use of a mixture of species allowing the elements more Malmesbury shales in the Eerste River catchment. suited to a site to predominate over others in time. In this sense, the widespread species, such as those listed lower down in 4.9. Community Group 9: Afromontane Forests Table 3, are the most valuable for rehabilitation. Many of these species also have a more extensive distribution in the fynbos Afromontane forests are generally restricted to kloofs, screes biome (Prins et al., 2004). The natural dynamics of the river and riparian zones (Campbell, 1986; Cowling et al., 1992). In system, by filtering out species that are not suitable for the local riparian forests, some elements of riparian scrub occur together habitat, determine which communities will become established with the Afromontane vegetation. In their study of the extensive and for this reason it is not strictly necessary to ‘design’ reveg- forest communities of Table Mountain, Campbell and Moll etation at the community level. Choosing suitable species at the (1977) recognized a few forest communities that are typically level of the Community Groups should be sufficient to provide riparian. The single species that distinguishes riparian forest an opportunity for the river to ‘self-design’ riparian vegetation. from other forest types is Cunonia capensis (rooiels) and, in Some species occurring in a wide range of riparian habitats some cases, Platylophus trifoliatus (witels). These forests typi- and especially the Dry Bank vegetation, are also common in cally occur on deeper soils and are most extensive in gorges that upland fynbos vegetation, for example Ehrharta rehmannii and seldom burn. The pH of the soil ranges between 4.5 and 5.0. E. hispidula. These species can be recruited from upland fynbos In this study, riparian forest was found in all catchments, vegetation and do not necessarily need to be brought in from with the exception of the communities typical for the Lourens elsewhere during the revegetation process, unless the erosion River (Associations 9.2 and 9.3; this catchment has some quite risk is too high to wait for natural recruitment. Obligate riparian extensive forests with a higher species diversity). There are not species, such as E. caffra and Ischyrolepis subverticillata are many differences between the forests of the various catchments probably more important to plant during revegetation. (Association 9.4). In most cases, forests occur at low altitudes at Prins et al. (2004) did a comparable study and even though the bottoms of the valleys, while structurally-lower vegetation their rivers have a larger geographical spread, they did not find a types dominate at the higher altitudes. There are exceptions, larger diversity of community types, with only four main com- however, and forest sites have been found in steep gorges at munities described. This confirms that most of the dominants high altitudes as well. Typical species of the Afromontane species, that are useful for revegetation purposes, have a wide- Forest in the tree layer are Apodytes dimidiata, C. capensis, Ilex spread distribution within the fynbos biome. The subdivision of mitis, and Rapanea melanophloeos. Dry and Wet Bank is useful, however, for revegetation purposes, since the disturbance regimes are very different. For example, 4.10. Community Group 10: Riparian Scrub many of the Dry Bank species that are shared with the upland fynbos vegetation would not be able to cope with frequent This Community Group forms the typical riparian scrub de- inundation that occurs close to the river. Some of the Wet Bank scribed by Campbell (1986) as Closed-Scrub Fynbos. In the types that are described in this paper have a strong pioneering study area, it consists of only one association with two sub- character and can probably grow quickly from seed and do not associations. Its most conspicuous characteristic is a layer of necessarily have to be planted (Vosse et al., 2008-this issue). shrubs between 2.0 and 4.0 m tall. This covers on average 45% Prior to selecting species from Table 2, an assessment must of the relevé. Sometimes a sparse tree layer is present above the be made of the range of riparian habitats available along the E.J.J. Sieben, M.K. Reinecke / South African Journal of Botany 74 (2008) 401–411 409 project reach. It is not necessary to maintain species in their and 9) is found; not all combinations are likely to occur. The Community Groups as self re-adjustment will occur following a most important examples are shown in Fig. 3, but there are number of seasonal cycles. It is preferable, however, to coarsely many variations of these similar banks that include the less imitate a general riparian structure, for example by choosing a common vegetation types described in this paper. combination of shrubs, trees and restios. It is also preferable to Research into the different riparian vegetation types through- separate out the Wet Bank from the Dry Bank areas and plant out the fynbos biome is needed to highlight some of the rare vegetation specifically suited to these different lateral zones. vegetation types that require extra attention during rehabilita- Typically, a combination of one or more of the Wet Bank com- tion projects. The findings of Reinecke et al. (2007) suggest that munities (Community Groups 2, 3, 4, 9 and 10) and one or more turnover in riparian vegetation types may be quite high in the of the Dry Bank communities (Community Groups 5, 6, 7, 8 fynbos biome, but this is likely to affect mainly the Dry Bank

Fig. 3. Some examples of lateral vegetation zonation patterns from rivers in this study. 410 E.J.J. Sieben, M.K. Reinecke / South African Journal of Botany 74 (2008) 401–411

(Fynbos) vegetation. Some rare vegetation types recorded in the Galatowitsch, S., Richardson, D.M., 2005. Riparian Scrub recovery after clear- Hottentots Holland Mountains might be more common in other ing of alien invasive trees in headwater streams of Western Cape, South Africa. Biological Conservation 122, 509–521. parts of the fynbos biome and some common types in the Glavaç, V., Grillenberger, C., Hakes, W., Ziezold, H., 1992. On the nature of Hottentots Holland Mountains may be largely restricted to this vegetation boundaries, undisturbed flood plain forest communities as an area. Dominant species in the present study, like R. purpur- example — a contribution to the continuum/discontinuum controversy. ascens, only have a limited distribution outside the study area. Vegetatio 101, 123–144. — Perhaps the most unique vegetation types found during this Hill, M.O., 1979. TWINSPAN a FORTRAN Program for arranging multi- variate data in an ordered two-way table for classification of the individuals study were those from the granites and shales, since these and the attributes. Cornell University, Department of Ecology and System- substrates are rare in the mountains of the fynbos biome. atics, Ithaca, New York. More research is needed generally on species distributions Hobbs, R.J., Harris, J.A., 2001. Restoration ecology: repairing the earth's eco- and community types from a larger number and more varied systems in the new millennium. Restoration Ecology 9, 239–246. types of rivers in the Western Cape, and indeed from other parts Holmes, P.M., Richardson, D.M., Esler, K.J., Witkowski, E.T.F., Fourie, S., 2005. A decision-making framework for restoring riparian zones degraded of South Africa. A central database of species data would be by invasive alien plants in South Africa. 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Edited by ETF Witkowski