**5. Discussion**

wetness zones indicated in Table 3. Usually species richness decrease with increasing wetness levels as few plant species are adapted to waterlogged soil [12]. However, in this study species richness in the permanently wet (therefore high organic and peat substrate) zones is actually

> **1** 9 3 2 4 **2** 32 6.4 4 10 **3** 22 4.4 3 7 **4** 19 6.33 5 7 **5.1** 58 9.7 5 13 **5.2** 103 17.17 14 24 **6.1** 59 14.75 12 19 **6.2** 75 10.7 8 17 **7.1** 33 6.6 4 10 **7.2** 26 6.5 2 10 **7.3** 79 8.78 4 14 **8.1** 70 11.7 6 17 **8.2** 67 7.44 4 10

**System Community Average species per 4 m2**

**Zone Community Average species per 4 m2**

PP & DP 1; 2; 3; 6.2 6.1 MS 6.1; 7.1; 7.2; 7.3 9.2 IDD 8.1; 4; 5.2 11.7 PL 5.1; 8.2 8.6

Permanently wet 8.1; 7.3; 7.2 8.993 Seasonally wet 8.2; 7.1; 4; 1; 2; 3 5.695 Terrestrial 6.2; 6.1; 5.1; 5.2 13.08

**4m2 Lower Higher**

much higher than that of seasonally wet zones.

286 Biodiversity - The Dynamic Balance of the Planet

**Table 1.** Species richness of each community.

**Table 2.** The average species richness for the various systems.

**Table 3.** The average species richness for the various wetness levels.

**Community Species richness Average species per**

#### **5.1. Muzi Swamp (MS) system**

#### **Characteristic plant species of the Muzi Swamp System**

**Terrestrial zone:***Acacia nilotica* & *Hyperthelia dissoluta*

#### **Seasonal zone:***Imperata cylindrica*

**Permanently wet zone:***Cladium mariscus, Phragmites australis, Stenotaphrum secundatum, Cynodon dactylon, Dactyloctenium aegyptium*

### **Typical plant communities:** 6.1, 7.1, 7.2, 7.3

There is a distinct division between the terrestrial zones (sub community 6.1) and the perma‐ nently and seasonally wet zones of the MS System (Community 7). The grass *Imperata cylindrica* invariably characterizes the seasonal zone (sub community 7.1); even though this zone is very closely associated with the permanently wet zones (sub community 7.2 and 7.3). This community is described in Matthews *et al.* [31]. It also correlates with the "proximalseasonally inundated floodplain" in Patrick & Ellery [30], in that it is functionally connected to the channel by being exposed to seasonal flood events and sedimentation.

The MS system is characterized by both a peat substrate which has a relatively high species richness as well as clay lenses on its edges which, in this study, has shown to have a lower species richness.

#### **5.2. Perched Pans (PP) and Depressions (DP) clay systems**

#### **Characteristic plant species of the PP and DP (clay) systems (Figure 9)**

**Terrestrial zone:***Acacia nilotica, Acacia karroo, Justicia flava, Panicum maximum*

**Seasonal zone:***Cyperus fastigiatus* (PP System) & *Echinochloa colona* (DP System)

#### **Permanently wet zone:***Lemna gibba*

#### **Typical plant communities:** 1, 2, 3, 6.2

Matthews [30] describe two communities which occur on clay pans in the TEP-a "grassland on clay between thicket and pan marsh edges" Community, which does not correlate with what was found in the PP System; and a "*Nymphaea nouchali* aquatic vegetation in marshes and pans" which do correlate with the inundated zones found in the PP and DP Systems. There is a strong division between zone 1 (Community 1) and zone 2 (Community 2) of the PP System; as well as zone 1 (Community 1) and the seasonal zone 2 (Community 3) of the DP System. Community 3 is composed of many species that are regarded obligate hydrophytes such as *Marsilea sp., Pistia stratiotes*, and *Nymphaea nouchali*, yet it is regarded a seasonal zone. This classification of this community is as a result of the prominence of *Echinochloa colona* which didn't occur in open water, but in the area which is still waterlogged and able to host hydro‐ phytic species such as those named above. *Echinochloa colona* is indicative of overgrazing and trampling [32], and occur in wetlands due to human influences. The PP System is utilized by animals of the Tembe Elephant Park as a water hole. The trampling of the pans by large animals decreases the open water zone and compacts the seasonal zone, destructing the habitat of the hydrophytes that could have occurred there.

**Permanently wet & seasonal zone:***Cladium mariscus, Cyperus natalensis, Hemarthria altissima,*

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The species composition of Community 4 illustrates the over-exploitation of the IDD system for the fertile, high organic substrate in the waterlogged areas. The permanently wet and seasonal zones are drained by trenches and drains through the wetland. The drainage lines stay visible, coining the term "fossil gardens" [33] (Figure 9 b). Only the seasonal zones from the disturbed wetlands form part of the disturbed Community 4. The permanently wet zone 1 doesn't floristically show disturbance as much as the seasonal zone, and seems to be buffered to some extent. A disturbance regime therefore has a much larger effect on the seasonal zones

The IDD and the PL Systems are generally grouped very closely together. The wet zones of both these systems occur close together in the ordination space, despite the IDD System having a permanently wet peat substrate and the PL System being periodically flooded open sandy plains. The only explanation that can be put forward for the similarity in species is that the peat might be shallow enough that the plants in the IDD System is rooted in the underlying sand substrate beneath the peat, and not necessarily in the peat itself. There is also a high similarity between the terrestrial zones of the PL (sub community 5.1) and IDD (sub com‐

In the ordination results, however, these sub communities are far removed from each other. The zone differentiation in the IDD System is somewhat different to that of the other systems, as there is only a permanently wet zone and a terrestrial zone. Zones 1 and 2 cluster together in the highly organic, waterlogged community, and Zones 3 and 4 clusters together in the sandy grassland terrestrial community. This is because the transition between the permanently wet zone and the terrestrial zones is so sharp due to the steep slope of the depression, that the "seasonally wet zone" is just a small area at the slope foot. This zone is still high in organic

The IDD system has the highest species richness of all the systems. This can be attributed to the high organic substrate that dominates this system. It is also devoid of clay, which seems

**"Wet" and seasonal zone:***Cyperus natalensis, Centella asiatica, Hemarthria altissima, Eragrosits*

munity 5.2) systems, probably due to the sandy substrate of these terrestrial zones.

carbon content, and therefore shares many species with the permanently wet zone.

*Thelypteris interrupta*

**Disturbed seasonal zone:***Scleria sobolifer, Xyris capensis*

**Typical plant communities:** 8.1, 4, 5.2

where the hydrological regime is variable.

to support a lower species diversity.

**5.4. Upland Wetland (PL) System**

**Typical plant communities:** 5.1, 8.2

*heteromera*

**Characteristic plant species of the PL system**

**Terrestrial zone:***Cyperus natalensis, Bulbostylis contexta*

The terrestrial zones cluster together into one community (Community 6), despite the differ‐ ences that divide the inundated zones of the DP and PP System. Community 6 is far removed from Communities 1-3 (the wet and seasonal zones of the PP and DP Systems). The association of sub community 6.1 (MS System) with 6.2 (PP System) is based on the similarity of the substrate – a sandy topsoil underlain by a horizon with a significant increase in clay (duplex soil).

**Figure 9.** The floristic differences between the two clay systems with a) PP System and the b) DP System.

The species richness in Community 1 (the inundated community of both the PP and DP systems) is much lower than in Community 2 and 3 (the seasonal zones) and sub community 6.2 (the terrestrial zones). These results highlight the difference between species richness in high organic, fertile substrate versus the poor species richness on clay substrates, and supports the general rule of decreasing species richness with increasing wetness. As with the other systems the species richness is higher in the terrestrial zones, although still somewhat less in these clay systems as opposed to the other systems' terrestrial zones.

#### **5.3. Interdune-depression (IDD) system**

#### **Characteristic plant species of the IDD system**

The terrestrial zones of the IDD System have exclusive species assemblages. The disturbed community (Community 4) and the permanent-and seasonal zones, share many species with the PL System.

#### **Terrestrial zone:***Themeda triandra, Trachypogon spicatus*

**Permanently wet & seasonal zone:***Cladium mariscus, Cyperus natalensis, Hemarthria altissima, Thelypteris interrupta*

**Disturbed seasonal zone:***Scleria sobolifer, Xyris capensis*

#### **Typical plant communities:** 8.1, 4, 5.2

trampling [32], and occur in wetlands due to human influences. The PP System is utilized by animals of the Tembe Elephant Park as a water hole. The trampling of the pans by large animals decreases the open water zone and compacts the seasonal zone, destructing the habitat of the

The terrestrial zones cluster together into one community (Community 6), despite the differ‐ ences that divide the inundated zones of the DP and PP System. Community 6 is far removed from Communities 1-3 (the wet and seasonal zones of the PP and DP Systems). The association of sub community 6.1 (MS System) with 6.2 (PP System) is based on the similarity of the substrate – a sandy topsoil underlain by a horizon with a significant increase in clay (duplex

**Figure 9.** The floristic differences between the two clay systems with a) PP System and the b) DP System.

these clay systems as opposed to the other systems' terrestrial zones.

**5.3. Interdune-depression (IDD) system**

the PL System.

**Characteristic plant species of the IDD system**

**Terrestrial zone:***Themeda triandra, Trachypogon spicatus*

The species richness in Community 1 (the inundated community of both the PP and DP systems) is much lower than in Community 2 and 3 (the seasonal zones) and sub community 6.2 (the terrestrial zones). These results highlight the difference between species richness in high organic, fertile substrate versus the poor species richness on clay substrates, and supports the general rule of decreasing species richness with increasing wetness. As with the other systems the species richness is higher in the terrestrial zones, although still somewhat less in

The terrestrial zones of the IDD System have exclusive species assemblages. The disturbed community (Community 4) and the permanent-and seasonal zones, share many species with

hydrophytes that could have occurred there.

288 Biodiversity - The Dynamic Balance of the Planet

soil).

The species composition of Community 4 illustrates the over-exploitation of the IDD system for the fertile, high organic substrate in the waterlogged areas. The permanently wet and seasonal zones are drained by trenches and drains through the wetland. The drainage lines stay visible, coining the term "fossil gardens" [33] (Figure 9 b). Only the seasonal zones from the disturbed wetlands form part of the disturbed Community 4. The permanently wet zone 1 doesn't floristically show disturbance as much as the seasonal zone, and seems to be buffered to some extent. A disturbance regime therefore has a much larger effect on the seasonal zones where the hydrological regime is variable.

The IDD and the PL Systems are generally grouped very closely together. The wet zones of both these systems occur close together in the ordination space, despite the IDD System having a permanently wet peat substrate and the PL System being periodically flooded open sandy plains. The only explanation that can be put forward for the similarity in species is that the peat might be shallow enough that the plants in the IDD System is rooted in the underlying sand substrate beneath the peat, and not necessarily in the peat itself. There is also a high similarity between the terrestrial zones of the PL (sub community 5.1) and IDD (sub com‐ munity 5.2) systems, probably due to the sandy substrate of these terrestrial zones.

In the ordination results, however, these sub communities are far removed from each other. The zone differentiation in the IDD System is somewhat different to that of the other systems, as there is only a permanently wet zone and a terrestrial zone. Zones 1 and 2 cluster together in the highly organic, waterlogged community, and Zones 3 and 4 clusters together in the sandy grassland terrestrial community. This is because the transition between the permanently wet zone and the terrestrial zones is so sharp due to the steep slope of the depression, that the "seasonally wet zone" is just a small area at the slope foot. This zone is still high in organic carbon content, and therefore shares many species with the permanently wet zone.

The IDD system has the highest species richness of all the systems. This can be attributed to the high organic substrate that dominates this system. It is also devoid of clay, which seems to support a lower species diversity.

#### **5.4. Upland Wetland (PL) System**

#### **Characteristic plant species of the PL system**

**Terrestrial zone:***Cyperus natalensis, Bulbostylis contexta*

**"Wet" and seasonal zone:***Cyperus natalensis, Centella asiatica, Hemarthria altissima, Eragrosits heteromera*

#### **Typical plant communities:** 5.1, 8.2

Moist grasslands feature strongly in all vegetation studies done on the MCP, and are termed "hygrophilous grasslands". Various studies [9, 34, 35, 36] detail 'high water-table grassland' communities termed 'hygrophilous grasslands', which corresponds loosely to both The PL and IDD systems. All the above studies noted dominant occurrence of *Ischaemum fascicula‐ tum*, which was not found abundantly in the PL System. The water table of the PL System (> 3 m deep) is in most areas not as high as the hygrophilous grassland communities described by the above authors. The absence of *I. fasciculatum* from the PL System might thus be a result of the variable hydrological regime. This argument is supported by Matthews [33] who states that *I. fasciculatum* is a species which reflects periods of inundation.

**6. Conclusion**

**•** a seasonal zone; and

logical zones set out above.

and a terrestrial hydrological zone:

**•** a terrestrial zone.

in terms of plant communities and species richness.

The clay systems (PP and DP) have three distinct zones:

trial zones separately, due to the substrate type.

MCP, few have focused on wetlands specifically.

regime and organic content of soils are interlinked.

The results from this study indicate clear differences between the different wetland systems

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The DP System has more vegetation zones than only three, but they cluster with the hydro‐

The sandy and organic wetlands (including the duplex MS System) are characterized by more than three vegetation zones, which can be grouped into a permanently and seasonally wet,

**•** The permanently and seasonally wet zones were found to group together, with the terres‐

**•** The permanently and seasonally wet zones of the wetlands on the MCP are extremely high

Few of the communities, sub-communities and variants in this study are floristically associated with other vegetation communities described in the literature, probably due to the detailed scale of this wetland study. Although some vegetation studies have been conducted on the

The statement by Matthews [31]: '…the important determinants of vegetation communities (are) the interconnected effects of water table (moisture), soil type and topography ….' is supported by this study. Although the specific type of wetland systems add to the various vegetation assemblages found, it does not account for all the differences encountered between vegetation communities. The main difference between vegetation compositions can be accounted for by the substrate type. In the ordination following the removal of the clay substrate type, the main division made was based on substrate (organic versus sand) and hydrological regime (a terrestrial group, and a combined seasonally and permanently wet group (Figure 8)). Although it is unclear at this stage which of these two factors is the main divisive factor, it is deemed unnecessary to investigate in detail as it is known that hydrological

The specific type of system from which a relevé originates is the final classification factor. In certain instances the whole system is characterized by a specific substrate (such as the DP and PP systems), in which case it can be said that their vegetation types are limited to that specific system. The rest of the wetlands on the MCP occur on a predominantly sandy substrate, and

in organic carbon content, and thus have similar vegetation assemblages.

**•** The PL System also varies a bit, as there is a lot of overlap from zone 1 to zone 4.

**•** a wet zone (not permanently wet, but saturated for at least 6 months of the year);

There is therefore a large overlap between the terrestrial zones and the wetter zones of the PL and IDD Systems (e.g. *Sorghastrum stipoides*, which occurs in high abundances and in Com‐ munity 5 and sub community 8.2). The terrestrial zones of the PL System (sub community 5.1) are similar to the wet and seasonal zones of both the PL and IDD system (sub community 8.2), and not so much similar to the terrestrial zones of the IDD System (sub community 5.2). This is because the transition between the zones of the open PL System is much more gradual than that of the closed and sharply demarcated IDD System.

As a result of the hydrological regime and gradual zone transition, the zones of the PL System are difficult to delineate with certainty, and display a lot of species overlap. Still there is a strong division between the 'wet' zones and the terrestrial zones of the PL System. Zones 1 and 2 occur together as the 'Sandy Organic Grasslands' (sub community 8.2), and Zones 3 and 4 occur as the 'Terrestrial Sandy Grassland' (sub community 5.1). *Cyperus natalensis* occurred in most of the zones in the PL System, as well as in some IDD communities. *Centella asiatica* occurred abundantly in the wet zones of the PL and IDD Systems, but not at all in the terrestrial zones. These two species together seem to be indicative of some signs of 'wetland' conditions on sandy substrates (they were absent in the clay systems).

One of the biggest threats to seasonally wet, event-driven, rainwater-dependent, hygrophilous grasslands such as the PL System is a drop in the water table [9, 36]. This is mostly caused by afforestation, and can already be seen as the numerous informal plots of *Eucalyptus* trees (Figure 10 d). These hygrophilous grasslands are an essential and important part of the wetland catchment area of the Kosi Bay lake system and Lake Sibaya, and are also responsible for the recharge of the lower lying wetland areas such as the Muzi Swamp to the west and the numerous swamp forests occurring in the drainage lines to the east of the PL System [9, 17]. The drop of the water table over the past 20 years have had a significant effect on the PL System, and might explain the floristic and hydrological differences that exist between this system and the other described hygrophilous grasslands on the MCP.

Subsistence agriculture also poses a threat to the wetlands of the PL System (Figure 10 a). These gardens make use of the organic rich and moist soil in the wettest portions of the wetlands. No drainage lines are usually necessary, as the PL System is not permanently wet. Because it is mainly a sedge and grassland system, the vegetation removal to make space for crops is minimal. The effect of the gardens are thus less severe in this system, but a lot of the soil organic carbon still goes lost during the agriculture practices.
