TITLE: An Ecological Study of the Plant Communities and Degraded Areas
of the Highveld National Park, North West Province, South Africa
Mahlomola Ernest Daemane
BSc.; BSc Hons.
Thesis submitted in partial fulfillment for the degree
MAGISTER SClENTlAE (BOTANY)
School of Environmental Sciences and Development,
North West University
Potchefstroom
Supervisor: Prof. S. S. Cilliers
Co-supervisor: Dr. H. Bezuidenhout
November 2007
PREFACE
The research described in this dissertation was carried out in the School of
Environmental
Sciences
and
Development,
North
West
University
(Potchefstroom) and in the proposed Highveld National Park (HNP), from 2005 to
2007, under the supervision of Prof. Sarel Cilliers and co-supervision of Dr. Hugo
Bezuidenhout
This study represents original work by the author and has not otherwise been
submitted in any form for any degree or diploma to any other University. Where
use has been made of the work of other authors it has been duly acknowledged
in the text.
ACKNOWLEDGEMENTS
I would like to thank God for keeping me strong and courageous. "He
brought me this far and I know he is going to take me all the way".
I would also like to express my deepest gratitude towards the following persons
and institutions for positive contributions towards the completion of this study:
North West Parks and Tourism Board; Potchefstroom City Council, South
African Defense Force and Barolong Community for the opportunity to
undertake this study in the Highveld National Park.
South African National Parks for financial support.
My supervisors, Prof. Sarel Cilliers and Dr. Hugo Bezuidenhout: for their
guidance, encouragement and unconditional support when I needed it
most.
Dr. Steven Holness and Ms. Phozisa Mamfengu for assisting me with the
maps, your help is highly appreciated.
Dr. Hector Magome, Managing Exucutive Conservation Services
Department for his encouragement, guidance, friendship and inspiration
throughout all the years.
Mr. Abbey Legari for his help with the field work; without him this project
would not have been completed.
To my wife and kids, whose love makes my life so complete.
ABSTRACT
The objectives of the study were to identify, classify, describe and map the plant
communities in the proposed Highveld National Park, including the degraded
Spitskop areas. Vegetation sampling was done by means of the Braun-Blanquet
method and a total of 108 stratified random releves were sampled. A numerical
classification technique (TWINSPAN) was used and the result was refined by
Braun-Blanquet procedures. The final results of the classification procedure were
presented in the form of phytosociological tables and twelve plant communities
were described. For indirect ordination, a Detrended Correspondence Analysis
(DCA) algorithm was applied to the data set to confirm the phytosociological
association and to assess floristic relations between communities. For direct
environmental gradient analysis the Canonical Correspondence Analysis (CCA)
was applied to the data using the CANOCO software program. The plant
communities were combined into six management units based on similarities
regarding vegetation composition, habitat, topography and soil characteristics.
Characterization of land degradation was done by grouping erosion into different
classes and different degrees of severity. Degraded areas in need of
rehabilitation and restoration were identified and described. Recommendations
were made with regard to rehabilitation and monitoring of all degraded areas in
the HNP.
Keywords: Braun-Blanquet, classification,
degradation, erosion, Highveld
National Park (HNP), management units, ordinations, plant communities.
Die doelwitte van hierdie studie was om die plantgemeenskappe in die
voorgestelde
Spitskopareas,
Hoeveld
te
Nasionale
identifiseer,
Park,
insli~itende die
klassifiseer,
beskryf
gedegradeerde
en
karteer.
Plantegroeiopnames is gedoen met behulp van die Braun-Blanquetmetode en 'n
totaal van 108 gestratifiseerd-ewekansige releves is gedoen. 'n Numeriese
klassifikasietegniek (TWINSPAN) is gevolg en die resultaat is deur middel van
die Braun-Blanquetprosedure verfyn. Die finale resultate is in die vorm van
fitososiologiese tabelle aangebied en twaalf plantgemeenskappe is beskryf. Vir
indirekte ordening is 'n DCA (Detrended Correspondence Analysis) algoritme op
die datastel toegepas om fitososiologiese assosiasies te bevestig en om
moontlike floristiese verhoudings tussen gemeenskappe te bepaal. Vir direkte
omgewingsgradientanalise is 'n CCA (Canonical Correspondence Analysis)
algoritme met behulp van die CANOCO-rekenaarprogram op die data toegepas.
Die plantgemeenskappe is op grond van ooreenkomste ten opsigte van
plantegroeisamestelling, habitat, topografie en grondeienskappe in ses
bestuurseenhede saamgevoeg.
Velddegradasie is gekarakteriseer deur erosie in verskillende klasse en grade
van hewigheid te groepeer. Gedegradeerde gebiede wat rehabilitasie en
restorasie benodig is gei'dentifiseer en beskryf. Aanbevelings is ten opsigte van
rehabilitasie en monitering van alle gedegradeerde gebiede in die HNP gemaak.
Sleutelwoorde: bestuurseenhede, Braun-Blanquet, degradasie, erosie, Hoeveld
Nasionale Park (HNP), klassifikasie, ordenings, plantgemeenskappe
TABLE OF CONTENTS
CONTENT
PREFACE................................................................................. ii
ACKNOWLEDGEMENTS ............................................................. iii
ABSTRACT .............................................................................. iv
OPSOMMING ...........................................................................
v
LIST OF FIGURES ...................................................................
X
LIST OF TABLES ...................................................................
xii
-
CHAPTER 1: INTRODUCTION
1.IBackground ..........................................................................
1.2 Aims of the study ..................................................................
1.3 Content of this thesis .............................................................
CHAPTER 2: MATERIALS AND METHODS
2.1 STUDY AREA
2.1 .IProposed area ...................................................................
2.1.2 Historical overview ..........................................................
2.1.3 Climate ............................................................................
2.1.4 Geology ...........................................................................
2.1.5 Land type and soil ..............................................................
2.1.6 Vegetation ........................................................................
2.1.7 Cultural. Historic and Archeological Resources .........................
2.2 METHODOLOGY
I
Ir5
2.2.1 Vegetation sampling ............................................................
2.2.2 Vegetation data processing ..................................................
I
2.2.3 Characterization of degraded areas .......................................
b 7
CHAPTER 3: CLASSIFICATION AND DESCRIPTION OF THE
VEGETATION OF 'THE HNP
3.1 lntroduction .........................................................................
3.2 Classification ........................................................................
3.3 Brief description of plant communities .......................................
3.4 Detailed description ...............................................................
3.5 Ordination ...........................................................................
3.6 Conclusion ..........................................................................
CHAPTER
4:
CLASSIFICATION
AND
DESCRIPTION
OF
VEGETATION IN THE DEGRADED SPITSKOP AREA
4.1 Introduction .........................................................................
4.2 Classification .......................................................................
4.3 Brief description of plant communities .......................................
4.4 Detailed description of plant comniunities .................................
vii
4.5 Ordination ........................
4.6 Conclusion ..........................................................................
CHAPTER 5: SOIL EROSION IN THE SPITSKOP AREA
5.1 Introduction .........................................................................
5.2 Results ...............................................................................
5.3 Discussion ...........................................................................
5.4 Conclusion ..........................................................................
CHAPTER 6: MANAGEMENT UNITS IN THE HNP
6.1 Introduction .........................................................................
6.2 Description of Management Units .............................................
6.2.1 Management Unit 1 ...........................................................
6.2.2 Management Unit 2
..........................................................
6.2.3 Management Unit 3 ............................................................
6.2.4 Management Unit 4 ............................................................
6.2.5 Management Unit 5 ............................................................
6.2.6 Management Unit 6 ............................................................
6.3 Conclusion ..........................................................................
CHAPTER 7: MANAGEMENT RECOMMENDATIONS FOR THE HNP
7.1 Introduction ........................................................................
7.2 Soil erosion control measures .................................................
7.3 Eradication of alien vegetation ................................................
7.4 Burning regime .....................................................................
7.5 Conclusion ..........................................................................
CHAPTER 8: CONCLUDING REMARKS .......................................
REFERENCES ..........................................................................
LIST OF FIGURES
FIGURE
PAGE
Figure 1. Location of Potchefstroom, North West Province, South 10
1 Africa, showing the Highveld National Park.
Figl~re2. The average annual rainfall (mm) for the area allocated for 11
the Highveld National Park.
Figure 3. Vegetation map of the Highveld National Park.
21
Figure 4. First Detrended Correspondence Analysis ordination with all 41
1 releves in the Highveld National Park.
1
Figure 5. Second Detrended Correspondence Analysis ordination with 42
87 releves in the Highveld National Park.
Figure 6. Vegetation map of the Spitskop area in the Highveld National 47
1
Park.
Figure 7. A Detrended Correspondence Analysis ordination with all 61
releves in the Spitskop area in the Highveld National Park
Figure 8. Canonical Correspondence Analysis showing correlation 62
I
between plant communities and soil erosion gradients in the Spitskop
area in the Highveld National Park.
Figure 9. A pie chart showing the dominance of erosion types and 67
severity classes in the Spitskop area in the Highveld National Park.
Figure 10. Sheet and rill erosion in the Spitskop area in the Highveld 68
National Park.
F i g ~ ~11.
r e Gully formation and infilling of a gully in the Spitskop area in
the Highveld National Park.
Figure 12. The destruction of protective vegetation cover by
overgrazing, fire impact and wood harvesting in the Highveld National
Park.
Figure 13. Ecological management units of the Highveld National Park.
Figure 14. Four subunits found in management unit 5 of the Spitskop
area in the Highveld National Park.
Figure 15. Exposed soil with eroded stones and rock particles in the
Spitskop area in the Highveld National Park.
Figure 16. Cattle dung providing a good growth medium in the area
affected by sheet erosion in the Spitskop area in the Highveld National
Park.
Figure 17. The soil erosion control measures using stone packing in the
Spitskop area in the Highveld National Park.
Figure 18. The soil erosion control measures using brush packing in the
Spitskop area in the Highveld National Park.
LIST OF TABLES
TABLE
PAGE
Table 1. Braun-Blanquet cover-abundance scale used for species in
pytosociological studies (Mueller-Dombois & Ellenberg, 1974).
Table 2. Field attributes describing soil degradation classes and the
extent of severity in the Highveld National Park (modified from Torrion,
Table 3. A phytosociological table of the Highveld National Park.
Table 4. Average height and cover values of the trees, shrubs and
herbaceous layers of the different plant communities in the Highveld
National Park.
Table 5. A phytosociological table of the Spitskop degraded areas in
the Highveld National Park.
Table 6. Summary of soil degradation types affecting plant communities
in the Spitskop area in the Highveld National Park.
Table 7. Average height and cover values of the trees, shrubs and
herbaceous layers of the different plant communities in the Spitskop
area in the Highveld National Park.
xii
Table 8. Information used in a Canonical Correspondence Analysis of
the Spitskop area in the Highveld National Park; showing correlation
coefficients, eigen values and percentage variance of ordination axes 1
and 2.
Table 9. Approaches in monitoring degradation status in the Highveld
National Park (Adopted & modified from Savory, 1990).
...
Xlll
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND
The effort to establish the proposed Highveld National Park (HNP) on the urban
,fringe of Potchefstroom in the North West Province resulted in an immense
enthusiasm between the different stakeholders. The Potchefstroom City Council
together with the South African Defence Force and the Highveld Barolong Local
Commur~itydonated a core area of more than 10 000 hectares of commonage for
the establishment of the HNP (Legari et a/., 2004). The land consolidation goals
for the HNP are aiming primarily to the rationalisation of the park boundaries, the
proclamation of properties incorporated but not yet proclaimed and the
identification and development of opportunities to link the park to other
conservation areas (Spies, 2004).
South Africa stands at the threshold of important and difficult socio-political
decisions with respect to land (Hoffman & Meadows, 2002). Within conservation
biology, human factors are treated as driving forces of biodiversity loss, yet there
are few empirical studies on how human actions affect biodiversity (Forester &
Machlis, I996). Ecosystem conservation in southern Africa (in particular South
Africa, Zimbabwe, Botswana, and Namibia) is characterised by high levels of
past and present conflicts (Fabricius et a/., 2001). More recently, after 1990,
there were many interrelated aspects to redressing land tenure inequity in the
country and two of these are land restitution and land redistribution. These new
policies allowed communities a better access to natural resources, called for their
participation in protected area management, and facilitated the restitution of land
from which they had been forcibly removed. Conservation strategies are being
developed to expand the number and size of protected areas by incorporating
communal lands (Fabricius et a/., 2001). In some cases conservation agencies
were able to expand the size of the protected wildlife estate by entering into
negotiations with local residents. This has resulted in a new category of protected
areas called "contractual parks", where communal land is incorporated into game
reserves so that it can be used for conservation and development purposes
(Fabricius et a/., 2001). The Richtersveld National Park in South Africa and the
more recent agreement with the Makuleke people for co-management of the
northern parts of the Kruger National Park are examples of this development
(Archer, 1999; Steenkamp, 1999). Although the HNP is not regarded as a
contractual park, all the stakeholders (South African National Parks, Barolong
Community, North West Parks & Tourism Board and Potchefstroom City
Council), will constitute what is known as the " Founding Partners" and have an
agreement (Memorandum of Understanding) which regl-~latestheir respective
rights and obligations within the park. This agreement also defines roles and
responsibilities of different partners as well as defining the ongoing management
and administration. Effective communication is seen as an essential element and
attention must be given to ensure the success of this initiative.
The HNP is aimed at conserving a considerable area of the western Grassland
Biome in South Africa and aesthetically it is one of the most scenic landscapes in
the western Grassland Biome (Mucina & Rutherford, 2006). The HNP is situated
in the Grassland Biome which will conserve the characteristic biological qualities
of the Highveld and Bankenveld grasslands (Rutherford & Westfall, 1986). Land
cover data (Fairbanks et a/., 2000) indicated that almost 30% of the Grassland
Biome of South Africa has been permanently transformed, primarily as a result of
cultivation (23%), plantation forestry (4%), urbanisation (2%) and mining (1%). A
further 7% has been severely degraded by erosion, agricultural improvement and
other factors (Mucina & Rutherford, 2006).
According to the State of
Environment Report, the formally protected areas in North West amount to
approximately 2.44% of the Province, which falls well below the 10% of each
vegetation type suggested by the Rio Convention to be set aside for officially
protected areas (Mangold et a/., 2002). The Grassland Biome also contains 640
Red Data Species (Hilton-Taylor, 1996), excluding species categorized as 'not
threatened', of which 136 are threatened with extinction and six are already
extinct. The need to conserve the Grassland Biome cannot be overemphasized
and the inventiveness towards the establishment of the HNP is ,therefore a
positive strategy towards achieving the goal set to prevent the decline of
biodiversity.
The need to address the global problem of land degradation is also increasingly
urgent (Hannah et a/., 2002) and can no longer be ignored when undertaking
vegetation studies. Barrows (1994) referred to land degradation as a reduction in
rank or status of the land. Hill efa/. (1995) defined land degradation as a process
which implies a reduction of potential productivity of the land. In summary, land
degradation is considered to be a collective degradation of different components
of the land such as water, biotic and soil resources (Hennemann, 2001). Loss of
vegetation cover and change in species composition are probably the first visible
forms of degradation, although it remains difficult to separate changes in veld
condition due to environmental factors (such as fluctuations in mean annual
precipitation) from those due to mismanagement (Hoffman & Meadows, 2002).
An increase in the human population also has an impact on land degradation due
to the increased demand on soil resources, resulting in soil degradation (Hurni,
1988; Lal, 1997; Hennemann, 2001). The area allocated for the HNP has already
been altered by human use to a great extent and, according to Beckerling (1989),
stock farming in the Highveld region has become increasingly important as a
result of the decrease in profit made on annual maize production. This problem
resulted in an inevitable increase in the number of livestock in the Highveld
region. Hoffman ef a/. (1999), however, certainly highlights that many, if not all, of
the changes occurl-ing across the corr~munallands in particular are components
of degradation expressed as, for example, human-induced reduction in
productivity and loss of biodiversity.
The natural resources of the HNP are essentially characterized by two important
elements, namely the landscape with its associated underlying soils and geology
and the biotic cornmur~itieswhich exist within this environment (Davies, 2003).
Both of these aspects have been impacted to some degree in the past and the
vegetation has been subjected to long and heavy utilization, probably from
overgrazing. It was observed that the main causes of degradation contributing
towards severe soil erosion in the area proposed for the HNP are overgrazing,
trampling by livestock and fire (Bezuidenhout, 1993). This resulted in severe soil
loss in some areas as well as to a change in species composition and vegetation
structure (Davies, 2003).
Land degradation requires rehabilitation and
restoration as it contributes to loss of biodiversity (Wilson, 1988; Meffe & Carroll,
1994; Primack, 1994), species extinction and loss of the earth's biomass and bioproductivity (C hown et a/., 2003).
The terms rehabilitation and restoration are frequently used interchangeably,
although incorrectly, to describe the same process and there is no common and
agreed upon set of definitions for these two terms (Roe & Van Eeten, 2002).
According to Rhoads et a/. (1999), the National Research Council defines
rehabilitation as 'a partial structural or functional return to the pre-disturbance
state'. Callicot et a/. (1999) defined ecological rehabilitation as the process of
returning, as nearly as possible, an ecosystem to a state of health or biological
integrity. Bradshaw (2002) defined ecological restoration as 'the return of an
ecosystem to a close approximation of its condition prior to disturbance with
ecological damage to the resource repaired and the structure and functioning
self-regulating system that is integrated within the landscape in which it occurs'.
The Society for Ecological Restoration (SER) gives its own definition of
ecological restoration as 'the process of assisting the recovery of an ecosystem
that has been degraded, damaged or destroyed1(Ormerod, 2003). According to
Coetzee (2005), rehabilitation emphasizes the reparation of the ecosystem
process, productivity and services. It returns some of the functions of the original
pre-disturbance ecosystem and the historical or pre-existing ecosystem.
Restoration shares with rehabilitation the repair of ecosystem processes, to as
close to the original structure and function as possible, but differs in that it also
includes the re-establishment of the pre-existing biotic species composition and
community structure (Coetzee, 2005). Restoration generally requires more postrehabilitation after-care and it takes much longer to achieve the desired result
(Coetzee, 2005).
Biodiversity loss is largely viewed as a function of human action (Soule, 1991;
World Resource Institute, 1992) and case studies are often used as subjective
evidence (Dale ef al., 1994; Kattan ef all 1994; Downing ef all 1990). Specific
human activities such as agric~~ltural
practices, deforestation efc., which may
influence biodiversity loss, have been empirically examined and found to be
crucial (Rudel, 1989; Koopowitz ef al., 1994). These potential driving forces of
land degradation and ultimately biodiversity loss include human population
growth (Meffe ef al., 1993; Meffe & Carroll, 1994), habitat loss, habitat
fragmentation, introduced species and diseases, population, and climate change
(Soule, 1991). In order to achieve biodiversity objectives, it is therefore iniportant
to conserve elements such as vegetation and soil as their loss enhances erosion
and reduces the productive value of the land (Hoffman & Todd, 2000; O'Brien,
2004). An understanding of the existence of specific plant communities and their
associated habitats is of fundamental importance for compilirlg sound
management and conservation strategies (Cleaver ef al., 2005). The description
of plant communities and mapping of both vegetation and degraded areas will
serve as the basis for formulating the management plan for the HNP.
1.2 AIMS OF THE STUDY
The aims of this study are:
To obtain data on the floristic composition and structure of the plant
communities in the HNP.
To classify, describe and map the plant communities in the HNP including
the degraded areas around Spitskop.
To identify the soil erosion types in the Spitskop area and their extent of
severity.
To provide recommendations towards effective future management of the
HNP based on specific management units.
1.3 CONTENT OF THIS THESIS
The thesis consists of eight chapters including this introductory chapter. In
Chapter 2, an overview of the materials and methods is given with particular
reference to the study area; history of the park; climate; geology; land types and
soil; vegetation; and cultural, historical and archeological resources. The
description of the scientific methods employed in the execution of this study is
also discussed in this chapter.
In Chapters 3 and 4, the classification and description of the vegetation of the
HNP and Spitskop degraded areas are given. Chapter 5 deals with the soil
erosion and other factors such as fire, overgrazing and wood harvesting
contributing to degradation in the Spitskop area. Chapter 6 entails the
identification and description of management units in the HNP. The management
recommendations for the HNP with regard to soil erosion control, eradication of
exotic species, fire regime and monitoring of degraded areas are provided in
Chapter 7. Chapter 8 provides the concluding remarks concerning the study as a
whole.
CHAPTER 2
MATERIALS AND METHODS
2.1 STUDY AREA
2.1 .IProposed area
The study area is situated between latitudes 26" 32' E - 26" 51' S and 26" 51' E 27" 08' S west of Potchefstroom (Figure 1). The area for park development lies
between the N12 running from Potchefstroom to Klerksdorp, Ikageng, Promosa
and the Eleazer road. The core area of the park occupies approximately 10 200
hectares, and consists of the Potchefstroom local authority land (5 500 ha), the
farm Modderfontein belonging to the Defence Force (2 700 ha), the farm
Nooitverwacht (1 500 ha) and a farm belonging to the Agricultural college (500
ha).
2.1.2 Historical overview
The proposal for the development of the HNP dates back from as early as 1984,
when the Department of Agriculture decided to inspect the campsites of the
townlands of the surrounding area of Potchefstroom with the aim to rent it
(Visser, 2005). During this stage it became clear that the value of the HNP
grassland was by far higher than the mere agricultural value and the thought of
establishing the park was brought into perspective. During 1990 the Department
of Agriculture started an initiative to investigate the possibility of the conservation
of grassland as well as the development of a national park in Potchefstroom
(Visser, 2005). Due to the fact that the land belonged to the municipality the
challenge was to convince the local ml.lnicipality of the importance of the
conservation of the grassland in order for them to donate the land to the National
Parks Board.
During this period of negotiations, a working committee was
established to gather information and to negotiate with the municipality with
regards to the development of the HNP (Visser, 2005). The development of the
HNP was approved by the National Parks Board (now known as SANParks) in
1992. However, due to pending land claini issues from the Barolong community,
the process of the development of the HNP was put on hold, but it was revived
again during 1996 and eventually led to the launching of the HNP in February
1997.
The park warden was appointed in 1996 and the Minister of Environmental
Affairs and Tourism formally approved the project for the development of the
HNP in August 1997. At this stage, which is known as the second phase in the
development of the HNP, the City Council of Potchefstroom donated some 5500
ha for the park, while negotiations to acquire a further 2700 ha (Modderfontein)
from the South African National Defence Force (SANDF) was well advanced.
During 1997, the South African Parks Trust purchased a nearby farm,
Nooitverwacht. This opened a corridor to privately owned land to the west which
was needed for viable park development. Plans were also completed to fence
the land and introduce game (Visser, 2005).
Due to the Barolong's determination of pursuing their land claims at all cost in
1997 and 1998, the SANDF withdrew from the project on 19 June 1998. A
written promise was made to the City Council that, if the current problems are
resolved, SANParks could again consider the opinion in future. This was a major
blow to tourism development in Potchefstroom, because of the loss of a great
opportunity (Visser, 2005). The third phase of the development of the HNP
started again during July 2001 with the consent of SANParks to investigate the
renaissance of the HNP. One of the recommendations during the third phase
was to ensure that the land claim issue has been laid to rest. At a special
meeting in Potchefstroom on 6 August 2002, all parties (including the Barolong
and SANDF) were in full agreement that the HNP was a hidden treasure which
could be a first national park for the North West Province and must therefore be
re-instituted (Visser, 2005).
The Barolong seemed to be very positive about the development of the HNP, as
it holds many benefits for them. The development of visitor facilities in the HNP
will be undertaken primarily through partnership with the Barolong community,
private sector developers and Small Mediuni and Micro Enterprises (SMMEs)
(Davies, 2003). The land of the Barolong that will be incorporated into the park
will be utilized as a community conservation area, where a community lodge will
be developed in the park (Visser, 2005). It was stated that, in 2004, SANParks
and the North West Parks and Tourism Board were negotiating with the SANDF
and private landowners to incorporate their land into the park. It was generally
accepted that the development would commence in 2005.
2.1.3 Climate
The area experiences a cool dry steppe climate with summer rainfall (Van der
Walt & Bezuidenhout, 1996). The rainfall is erratic and varies from an average of
600 mm per annum to exceptional occlrrrences of more than 900 mm per annum
(Figure 2). The area is characterised by great seasonal and daily variation in
temperature, being very hot in summer (daily average terr~peraturesmay exceed
32°C in January) and mild to cold in winter with average minimum monthly
temperatures of up to -12°C (ISCW, 2003). Hail occurs sporadically in summer,
with the southeast part of the province receiving 3-5 hailstorms per year and the
rest of the province approximately 1-3 per year (Mangold et a/., 2002).
Relative humidity is also typically low throughout the province, being below 28%
in the northern part of the province in July and between 28 - 30% for the central
and eastern regions (Mangold et a/., 2002). No long-term data is available for
wind speed and dominant wind direction for the North West Province, although,
the predominant wind direction is from a northerly direction (Mangold et a/.,
2002). There is a trend that August to November are the windy months (Mangold
et a/., 2002).
-
Nathnal Route
-
S m d a r y Road
-
Main Road
Figurel. Location of Potchefstroom, North West Province, South Africa, showing
the Highveld National Park.
1000 -
900 -
- 800 E
700 -
V
=
tu
600 -
.c
-5 500 -
z
m
400 -
3
a
300 200 100 0
1
1
7960
1
1
1
1
1965
1
1
1
1
1
1970
1
1
1
1
1
I975
1
1
1
1
1
1
1
1980
1
1
1
1
1985
1
1
1
1
1
1990
1
1
1
1
1
1995
1
1
1
1
1
,
1
2000
Year
Figure 2. The average annual rainfall (mm) for the area allocated for the Highveld
National Park.
2.1.4 Geology
The geology of the area is diverse and the core area is mainly represented by the
Transvaal Sequence. Three groups based on lithogical differences have been
established under the Transvaal Sequence (Bezuidenhout, 1993), of which the
Chuniespoort Group forms part of the study area. The dolomite of the
Chuniespoort Group (Malmani Subgroup) is found in the study area representing
the Fa-land type and continues to the south-west to Stilfontein and Orkney
(Bezuidenhout, 1993; Truswell, 1977). Rocky outcrops of dolomite and chert are
abundantly present (Bezuidenhout, 1993; Holness, 2003) and characterized by
the presence of sinkholes (Von Backstrom et a/, 1953). The flat or undulating
plains of the dolomites are dissected by prominent chert ridges (Bezuidenhout,
I993).
2.1.5 Land types and soil
A land type denotes an area that can be shown at 1:250 000 scale and that
displays a marked degree of uniformity with respect to terrain form, soil pattern
and climate (Land Type Survey Staff, 1984). Researchers such as Bredenkamp
& Theron (1978), Bredenkamp et a/. (1983), Bezuidenhout et a/. (1988), Cilliers
(1998) and others have established that geology; soil and climate are important
environmental factors which correlate well with plant communities of South
African grasslands. Land types therefore played an important role in the
stratification of study areas in a number of major studies in the Grassland Biome
(Bezuidenhout, 1993).
Four land types occur in the HNP, namely the Ba-, Bc-, Fa- and Fb-land types
(Bezuidenhout, 1993). The soil forms as well as technical terms used are
according to MacVicar et a/. (1977). The Ba-land type is characterized by red
and/or yellow apedal soils. Dystrophic and/or mesotrophic soils predominate over
red andlor yellow apedal soils that are eutrophic and in which red soils occupy
more than a .third of ,the area (Land Type Survey Staff, 1984). Tlie dominant soil
form in the Ba-land type is Hutton. The Bc-land type is dominated by both Hutton
and Mispah soil forms (21 % of the land type). The dominant soil forms in the
Fa-land type are Gler~rosaand Mispah (50 % of the land type), while the Hutton
soil form (39 % of the land type) is also present. The Fb-land type indicates land
where lime occurs regularly (in small quantities) in one or more valley bottom
soils. The dominant soil forms in the Fb-land type are Glenrosa (25 % of the land
type) and Mispah (24 % of the land type) with rocks (20 % of the land type) also
prominent in this land type (Bezuidenhout, 1993).
-The vegetation classification by Mucina & Rutherford (2006) classified the study
area within the Grassland and Savanna Biomes. The Grassland Biome is
represented by ,the Dry Highveld Grassland Bioregion Unit of which the study
area is represented by Vaal Reefs Dolomite Sinkhole Woodland (Gh 12), Rand
Highveld Grassland (Gm I I ) , Klerksdorp Thornveld (Gh 13), and Carletonville
Dolomite Grassland (Gh 15). 'The conservation status of the Rand Highveld
Grassland is endangered and whilst the conservation target is 24%, only 1% is
statutorily conserved. This vegetation unit has been transformed mostly by
cultivation, plantations, urbanisation or dam-building. The conservation status of
the Klerksdorp Thornveld (Gh 13) is vulnerable and only about 2.5% statutorily
conserved. Almost a third is already transformed by cultivation and urban sprawl
(Mucina & Rutherford, 2006). This vegetation unit has a high grazing capacity
which leads to overutilization and degradation, and subsequent invasion of
Acacia karroo into adjacent dry grassland. Due to the great habitat and floristic
diversity and for aesthetical reasons, the landscape deserves to be conserved
(Mucina & Rutherford, 2006). The conservation status of the Carletonville
Dolomite Grassland (Gh 15) is vulnerable and whilst the conservation target is
24%, only a small extent is currently protected and 23% is considered to be
transformed, mostly by cultivation (17%), urbanization (4%), forestry (1%) and
mining (1%) (Mucina & Rutherford, 2006).
-The Savanna Biome is represented by the Central Bushveld Bioregion Urrit of
which the study area is represented by Andesite Mountain Bushveld (SVcb 11)
(Mucina & Rutherford, 2006). According to Mucina & Rutherford (2006), the
proposed HNP is supposed to conserve a considerable area of the Vaal Reefs
Dolomite Sinkhole Woodland vegetation unit (Gh 12). 'The conservation status of
the Vaal Reefs Dolomite Sinkhole Woodland vegetation unit (Gh 12) is vulnerable
and whilst the conservation target is 24%, orlly a sniall patch is conserved in the
statutory conservation area of the Sterkfontein Caves (Mucina & Rutherford,
2006). Almost a quarter of this vegetation unit is already transformed, mainly by
mining, cultivation, urban sprawl and road-building.
2.1.7 Cultural, Historical and Archaeological Resources
'There is no direct evidence of any cultural, historical or archaeological resources
within the HNP (Davies, 2003). However, these issues must always be
considered when planning any new developments. They must form an integral
part of any Environmental Impact Assessment which is undertaken for setting out
any new infrastructure, as well as when removing old infrastructure if appropriate
(Davies, 2003)
2.2 METHODOLOGY
2.2.1 Vegetation Sampling
Vegetation sampling was firstly undertaken for the entire park consisting of 88
stratified, random, 900 m2 (30 m x 30 m) sample plots in accordance to
(1993). Stratification was done on I:50 000 scale
Bredenkamp & Bezuidenho~~t
aerial orthophotographs, on the basis of relatively homogeneous physiographic
and physiognomic units (Bezuidenhout, 1993). Secondly, vegetation sampling
was undertaken in the Spitskop area, consisting of 20 stratified, 900 m2 sample
plots located in the degraded areas. Stratification was done on 1.50 000 enlarged
(x10) aerial orthophotographs of the Spitskop area. -The approach of
Bezuidenhout (1993) for further stratification was followed, namely recognition of
the terrain types with topographical positions such as crest, scarp, midslope,
footslope, valley bottomlands and floodplains.
Plant species were identified in each plot during the time of sampling and the
cover abundance of each species was visually estimated using the BraunBlanquet scale (Mueller-Dombois & Ellenberg, 1974) (Tablel). Plant species
names were used according to Germishuizen & Meyer (2003). Exotic species are
indicated by an asterisk in the phytosociological tables. Additionally, average
height and canopy cover of tree, shrub and herbaceous strata were estimated.
The structural vegetation classification system for this study followed that of
Edwards (1983). Environmental data included identification of soil type, slope
(where applicable) and rockiness of the soil surface. The soil depth was
determined by using the soil auger and the soil forms were identified. The soil
clay content was determined by the 'feel-ribbon method' (Foth et a/., 1978) and
was expressed as a percentage. An estimation of the rockiness of the soil
surface was expressed in percentage rocks or stones covering the total sample
plot.
2.2.2 Vegetation data processing
The TWINSPAN classification algorithm (Hill, 1979a), which is regarded as a
very successful approach by many phytosociologists all over the world (Mucina &
Van der Maarel, 1989; Bredenkamp & Bezuidenhout, 1995; Cilliers, 1998) was
used as a first analysis for the floristic data. The TWINSPAN classification was
then refined further by application of Braun-Blanquet procedures by means of the
BBPC-program (Bezuidenhout et a/. 1996). For indirect ordination, a Detrended
Correspondence Analysis (DCA) algorithm (Hill 1979) was applied to the data set
to confirm the phytosociological association and to assess floristic relations
between communities. For direct environmental gradient analysis, the Canonical
Correspondence Analysis (CCA) was applied using the CANOCO software
program (Ter Braak, 1986). Descriptive terms such as differential species,
dotmillant species and co-dominant species were used according to Kent & Coker
(1992).
Table 1. Braun-Blanquet cover-abundance scale used for species in
phytosociologicalstudies (Mueller-Dombois & Ellenberg, 1974)
Cover values
r
Description
One or few individuals with less than 1% cover of the total
sample plot area
+
Occasional and less than 1% cover of the total sample plot area
1
Abundant with low cover, or less abundant but with higher
cover, I- 5% cover of the total sample plot area
2
Abundant with >5 - 25% cover of the total sample plot area,
irrespective of the number of individuals
2a
>5 - 12.5% cover
26
>12.5
3
>25 - 50% cover of the total sample plot area, irrespective of
- 25% cover
the number of individuals
4
>50 - 75% cover of the total sample plot area, irrespective of
the number of individuals
5
>75% cover of the total sample plot area, irrespective of the
number of individuals
2.2.3 Characterization of degraded areas
Characterization of the degradation in Spitskop followed that of Torrion (2002)
and this method was modified in the present study when measuring sheet
erosion (Table 2). Sheet erosion mostly occurs on the non-gradual slopes and it
is therefore very difficult to measure the amount of topsoil removed (Macdonald
et a/., 1990; Coetzee, 2005).
The description of soil erosion forms follows that of Macdonald et a/. (1990).
Sheet erosion: is the progressive removal of topsoil across extensive
areas by wind and water. This is not always easy to detect with certainty
and may need to be inferred from other soil surface features, such as
eroded material or surface nature. When at an advanced stage, many
sheeted surfaces are covered by layers of gravel or stone left behind after
the erosion of finer material.
Rill erosion: terrain deformation as a result of surface r ~ ~ n oforming
ff
shallow, well-defined channels (less than 30 cm deep)
Gully erosion: terrain deformation as a result of surface runoff forming
deeper, well-defined channels (more than 30 cm deep).
Expanded upon the Torrion (2002) classification, 'compacted soil' was added to
the degradation classes (Table 2). These areas are often overgrazed which
resulted in an advanced stage of degradation indicated by large areas of bare,
compacted soil (Bredenkamp et a/, 1988; Bezuidenhout, 1993).
Table 2: Field attributes describing soil degradation classes and the extent
of severity in the Highveld National Park (modified from Torrion, 2002).
Sub type
Class
Loss of
Sheet Erosion
Topsoil
/ Terrain
1
deformation
I Rill Erosion
I
Sub class
Subclass
(Torrion)
(Modified)
Loss of topsoil <5 cm
Bare soil 0 - 25 %
Slight
Loss of topsoil 5-15 cm
Bare soil 25 - 50 %
Moderate
Loss of topsoil 15-25 cm
Bare soil 50 - 75 %
High
Loss of topsoil > 25 cm
Bare soil > 75%
Severe
Severity
Shallow rills <3 cm
Slight
Incision rills occurring on steep
Moderate
slopes < I 0 cm
Gully
Tramplirlg
Compacted Soil
Wider braided rills 10-15 cm
High
Wider braided rills 15-20 cm
Severe
Shallow gully 30 cm-1 m
Slight
Deep gully 1-5 m
Moderate
Very deep gully >5 m
High
Extremely deep >30 m
Severe
Bare soil 0 - 25 %
Slight
Bare soil 25 - 50 %
Moderate
Bare soil 50 - 75 %
High
Bare soil > 75%
Severe
CHAPTER 3
CLASSIFICATION AND DESCRIPTION OF THE
VEGETATION OF THE HNP
3.1 1NTRODUCTION
The aim of this chapter was to classify, describe and map the plant communities
occurring in the HNP. The floristic composition of the different plant communities
was also obtained. The geology of ,the area, soil forms, terrain units, and
rockiness of the surface area was used when describing the plant communities.
The percentages of exotic species in different communities were also indicated to
show their extent of invasion and the need for management intervention. A
comparison (where applicable) was also made between the plant communities
found in the HNP and communities previously described by other researchers in
the former western Transvaal grassland.
The vegetation analyses are given in a phytosociological table (Table 3) and
resulted in the formulation of a vegetation map (Figure 3) and the recognition of
nine major plant communities. The non-hierarchical classification of these
communities is as follows:
1. Mystroxylon aethiopicum - Pavetta zeyheri S hrubland
2. Loudetia simplex - Vangueria infausta subsp. infausta Shrubland
3. Diheteropogon amplectens - Trachypogon spicatus Grassland
4. Schizachyrium sanguineum - Cymbopogon excavatus Grassland
5. Rhuspyroides - Acacia erioloba Woodland
6. Setaria sphacelata var. sphacelata - Acacia caffra Woodland
-
7. Ziziphus zeyheriana Acacia karroo Woodland
8. Cymbopogon pospischilii - Themeda triandra Grassland
9. Setaria incrassata - Hyparrhenia hirta Grassland
Figure 3. Vegetation map of the Highveld National Park.
3.3 BRIEF DESCRIPTION OF PLANT COMMLlNlTlES
1. The Mystroxylon aethiopicum - Pavetta zeyheri Shrubland was mainly limited
to the plateaus of the rocky quartzite hills and ridges.
2. The Loudetia simplex - Vangueria infausta subsp. infausta Shrubland was
associated with the midslopes of the rocky chert outcrops and quartzite ridges.
3. The Diheteropogon amplectens - Trachypogon spicatus Grassland occurred
on stony plains and midslopes of quartzite hills.
4. The Schizachyrium sanguineum
-
Cymbopogon excavatus Grassland was
associated with the midslopes of the shallow rocky soils of the chert outcrops.
5. The Rhus pyroides - Acacia erioloba Woodland was limited to the valley
bottomlands of the chert and dolorr~iticareas.
6. The Setaria sphacelata var. sphacelata
-
Acacia cafira Woodland was
associated with the midslopes of the rocky outcrops and quartzite hills.
7. The Ziziphus zeyheriana - Acacia karroo Woodland occurred on the footslopes
of the quartzite hills, valley bottomlands and along the drainage lines.
8. The Cymbopogon pospischilii
-
Themeda triandra Grassland was associated
with the midslopes of the rocky outcrops.
9. The Setaria incrassata
- Hyparrhenia hirfa
Grassland was restricted to the
bottomlands and floodplains in or along drainage lines.
3.4 DETAILED DESCRIPTION OF PLANT COMMUNITIES
-
1. Mystroxylon aethiopicum Pavetta zeyheri Shrubland
This community was mainly limited to the plateaus of the rocky quartzite hill and
ridges of the Bc- and Fb- land types. 'The soil surface was relatively rocky (>
10%) and the soil forms consisted of Mispah, Glenrosa and Hutton. The soil was
relatively shallow (< 0.2 m) with a relatively low clay content (< 10%).
The differential species of this community were those of species group A
(Table3). They included mainly indigenous species such as the shrubs Pavetta
zeyheri, Mystroxylon aethiopicum, Grewia occidenfalis, Vangueria parvifolia, the
indigenous trees Pappea capensis, Olea eumpaea subsp. africana and the grass
Panicum maximum.
Other species in this community included Vangueria
infausfa subsp. infausta (species group C, Table 3), Zanthoxylum capense
(species group C, Table 3) and Rhus magalismonfana (species group C, Table 3)
forming the major component of the shrub stratum (canopy cover of 38% and up
to 2.6 m tall). The indigenous fern, Pellaea calomelanos var. calomelanos
(species group C, Table 3), the tree, Acacia caffra (species group N, Table 3),
the herbaceous climber Clematis brachiafa (species group N, Table 3) and the
indigenous Aloe greafheadii var. davyana (species group N, Table 3) were also
found in this community. Species of general occurrence were fo~.~ndin species
group U (Table 3) and included two grasses, Themeda friandra and Elionurus
muficus. The average height of the tree stratum was 5.3 m with a canopy cover
of 19% (Table 4). The average height of the herbaceous stratum was 0.9 m and
with a canopy cover of 41% (Table 4). An average number of 33 species was
recorded per sample plot of which 1.2% was exotic species. Exotic plants
included species such as Gomphrena celosioides and Opunfia ficus-indica
(species group V , Table 3).
Table 3. A phytosociological table of the Highveld National Park.
Releve number
Plant community
415127146[49 8 115)18]54161)63164[66162[651673 1 2 6 1 3 7 1 3 9 ) 5 6 1 7 0 1 T i l 8 1 1 6 3 I 6 0 ) 6 8 [ 6 B ~ ~ l 8280 1 ~ o l 3 1 1 3 5 l 7 221]29
3
1
2
4
SPECIES GROUPA
Paveaa zeyhen
Mystraxylon aelhiop~cum
Pappea c a p n s s
Panrcum maxrmum
Olea eumpaea subsp afncana
Gmwa oc~nenlal~s
Vawuena pawifoh
-lA+
1+
1A
1
.A+
+ A
B
+
1+
R
A
+
B
+
3
1
1
+
+
B
+
1
A
SPECIES GROUP B
Loudeba srnplex
Mundulea sencea
Heltchrysum kraussi,
SPECIES GROUP C
Vanguena rnfausta subsp rnfausta
Zanthoxylum mpense
Pellaea calomelanos vai cabmelanos
Rhvr magal~smontana
3
1
A
3 3 B
+
+ +
+
3
1
33
1
l A + + A
A
+ I +
I +
+
z
+ 1
-c
+
+
+
+
l A +
c + +
+
+ +
+
+
+ +
+
+
I
A
4
+
+ + + +
SPECIES GROUP D
Chascanum adenostachyum
Hel~chrysumnuUtfolrum var nudiblrurn
Aloe zebnne
Brach~snangmpedata
+
+
I
1
t I
SPECIES GROUP E
Sene& venosus
+
Trachypogon sptcaf~s
Andmpopwr sch~rensrs
Gnldra captata
++ + + +
+ +
+ 3 1 1 +
+
+ + +
+
* + + +
t
*
+
+
1+
A A + B
+ +
- - + ' ~ j a e -an
+
- 1+
+ + + +
*
1
+ + +
.?.+~+++
+ +
*
n t
A
+ +
+
+
3 +
i
+
+
+
SPECIES GROUP F
Cymbopogon excavalus
Schmchynum sangutneum
Brachiana semfa
D m a anornala
Acalypha angunala
D~hetempogonampleclens
Elephaniorrhm eelpphanbna
EragmsbS racemosa
Melinrs nerv!glumis
Nolleba i-8df0.f~
Anstida m e n d ~ ~ n a k
SPECIES GROUP G
E m g m s ~ ssupe!ba
Celhs afncana
Acacia embba
S I ~ dfege~
?
Stoga a w k a
Eagrosr~strichophora
Diospyms lyciiniles subsp guerker
Spombolus afncana
l p m o e a oblongata
*
+
+
I *+
+.
* + + + A +
?
+
$
.+ + + +
. + . .
I+
:t
+ +
+
' + +
, . +
%
SPECIES GROUP J
Delospenna herbeurn
Ndorella enomak
S~dasplrwsa var sphosa
P a m e bufChel111
Poll~mVacarnpestns
Penbre globosa
Eragmstrs lehmannfana
f
A
I A
A
+
+
+
+
- * 4 .++ + +
+%-~:$~--=&
,
?fq+4&&
g,
. I .
+
+
*
. +
, + + ~
., +
.+
-
+
1
+ + +
+
+ +
+
+ +
+ +
R
+
+
+
+
+
+
A
+
+
+
+
+
+
+
+
+?,
+
+
+
c 4
+ + +
+
> *
+
+ +
+
1
+
+
+
+
.+
1
+
+
+
+
t
+
+
+
+
1
1
+
+
-
+ +
+
++
+
+
+-
+ ?
+ +
+ + +-y,
+
b
B
+
f
+
+
5
R R R
+
+ +
1A
R
SPECIES GROUP I
Dg~tariaenanlba
Crabbea angustrfolia
Blephans integnfol~a
Euclea undulata
Emgmsbs rigrdlor
Ind~goterahelerotncha
Chaerawofhus costatus
Anstrda fransvaalensis
Rhus leplod~crya
+
A+
'
1 1 +
t
1
I
+ +
1
+ + + + + +
SPECIES GROUP H
Tnaphis andmpcqomdes
lpwroee obscura mar obscura
PogonarMna s q u a w
Chascanum W r a c e u m
U m m a nana
1
+
+
+
+
+
1 1
+
I
A
+
+
++ + +
+
*
+
+ +
A
R
+
t
+
+
+
+
A
R
+
+
A
I
+
4
SPECIES GROUP M
SPECIES GROUP N
Aloe grealheadi, var. davyana
Clemaus brachrak
+
Hemennia depressa
Hypoxis hememcallidea
&/ago densf&
Wahlenberg;; undulata
SPECIES GROUP Q
Cymbooogon pospischili!
Heferopogon WntORuS
firphus zeyheriana
Teucrium tniidum
spa reg us laricinus
Verbena offWWh'
+
t
+ +
+
+
i
+
+
+
*
Releve number
Plant communlly
Conyza bonanensis'
Achyranlhes aspera'
Asparagus africanus
Helich~ysumzeyhen
Rhynchos~anervosa var. nervose
Macled~umzeyheri
Ammocharis mraniw
Grewia flava
Avena fatua'
Cryptoleprs oblongilblia
Hibiscus mrcfanrhus
Nfdorplla hoflenlot~ca
Charnaecflsla mimosoides
BoscB albilrunca
k m b e y a m~undifo!ia
Osycis lanceo1a:a
Pupalia lappacea war. lappacea
Ennespogon scoparius
Oldenlandia hetbacea var. herbacea
Sefaria sphacslala var. foca
Cussonia pniculala subsp. sinuaie
Lantana nrgosa
Zziphus mucmnaia subsp. mucfonala
Brjens bipinnata'
Hehchrysum setosurn
Gomphfena celosio~des'
Jamesbrfnenia aurantiaca
Triumfena sonden
Senecio oxynfolius
RhynchosM sp.
Cyperus indecorvs var. inflatus
Lotononis Ksti!
Boophone disticha
Thesrum utile
Gladiolus sp.
Indigofera comosa
Echinochlw holub!;
Hypoxis rigrdula var ngldula
Leesia hexandra
Seneuo wnrathii
P e a r s c n ~wpnirolia var. cajanfolta
Lepidium bonaflensa'
Acalypha peduncularis
Hypoxis sp.
Sebaea sphafhulala
Ba biana Rlaverensis
Becium anguslirolium
Cheilanfhes vifidis
Crabbea ecaulis
Trichoneura grandiglumis
Feiia'a filfolia
Senecio replans
Tragus bpdemnranus
Amiida biparlira
Kalanchoe rorundifolra
Schkuhria prnnata'
Jusuw anegalloides
Slnga elegans
Solanurn Ichlensteineinii
Tripleris aghillana
Raphmnacrne hrrsula
Scabiosa columbaria
Gomphocarpus ITUtzwsu~subsp ~ N ~ ~ O J S U S
Eragmsfis micrantha
C;clospermumleptophyllum '
Cyperus escuIenf~svar. esculantus
Ledebouria revoluta
Pamnychia brasiliana var. pubesens'
Physalis angulale'
Schizowrphus nervosus
Senecc bachypodus
Slachys spathulala
Trigonella anguina
Xysmalobium undulatum
Zornra capens$ subsp. capansrs
Aliemisia afra
Blepharis aspsra
Bonatea speciosa var. speciosa
Enneapogon cenchfoides
Emgmsfis oblusa
EucCa ctfspa
Gnidia capitala
Gusemineadensa'
Lantana camam'
Pemtis patens
Piantago IdnCeolata'
Sida monbifoh subsp, rhombilDlia
Solanum sisymbnfolium'
4 [ 5 ] 2 7 ] 4 6 1 4 9 61 151 1 8 / 5 4 621 631 641 661 621 651 67 31261 371391 561 701 771811 831 601 681691 8 4 88 201 301 311 351 72 211 29L
3
1
2
4
f
+
+
+
+
.+
+
t
+
5
+
+ +
+
+
k
R
+
t
+ +
+
+
+
c
t
+
1
+
+
f
+
+
+
+
1
+
+ + +
+
+
+
+
+
+
+
.
R
+
t
t
+ +
+
+
+ + + +
1
+ +
+
t
+
+
+
+
+
+
+
+
+
+
+
+
+
A
+
t
t
+
+
+
i
+
+
+
+
+
+
+
t
+
t
+ +
+
+
+
+ +
+
L
+
+
+ +
+
+
+
Releve number
Plant cornmunlty
I So~anumsu~inum
Spamania afncari~
Umchloa rnosambi#nsis
Wahlenbergiadenticu!afa
Aerva leucura
Chenopodum album'
EWDS~S m o m
Hypoxis argenlea
Meinie longiffora
Microglossa caffrorum
Euwrnis aulumnalis subsp. clavata
Haplocarpb8 Scaposa
Hibiscus tfionum
Oxalis sp.
Persicaria lapafhifolia'
Mornomiica balsamrna
Chamaecrisfa Diensis
Commelina bella
Stenolaphmm secundatum
Aristida spectabitis
Bewsia bAom
Crassula capdella
Cyanotis speciosa
Herrnaonia depressa
Indigofera mslmta
Ledebouna ovati(o1ia
Ulhops lesliei
Oxygonum drepeanum
Pachystigma pygmaeum
Phyllanlhus p a ~ u l u s
Vigna sp.
Vernonia poskeana
Gerbera piloselloides
Gnidia s%ncocephala
~n~figofeera
dalmrdes ver, daleoides
Kyphowrpa angusMoba
~icotiana~ongiflora'
Phyllanlhus mademspatensis
Polygala amafymbica
Jalinum caffmlrum
Jephmsia longipes subsp. bngrpes
Tephrosia sem.@labra
Acacia heremensis
~ibuca
sefosa
Chlomphylum coopen'
Eragrostis cepensis
Opuntia ficus-indicd '
Oxalis wmiculataAnlizoma anguslitol~a
Solanum nigrum'
Soianum pandunforme
Urochloe peniooides
Zmnia peruviana'
Salvia wncinala
Emgmstis ed~inochloidea
Osfeospennum murkalum subsp. muricalum
Oenothera msea'
Senecio inomatus
EragmsA gurnmflua
Cypcrvs pseudovestitus
OenoYlera tetmpkra'
Spombolus fimbnalus
Leucas capensrs
Badena macmstegh
AnstIda scabn'velv~s
16/51 271461 49181 161 181 541611 631 641 661 621 651 67131 261 371 391 561701 771 811 83160] 681 691 641 881 201 301 311 351 721 211 29
I
1
I
2
3
4
I
I
1
I
I
I
I
I
Table 4. Average height and cover values of the trees, shrubs and herbaceous layers of the different plant
communities in the Highveld National Park.
Stratum
Community
Shrubs
Trees
1. Mystroxylon aethiopicum
-
Herbaceous
Average
Average
Average
Average
Average
Average
height (m)
Cover PA)
height (m)
Cover PA)
height (m)
Cover PA)
19.0
2.6
38.0
0.9
41.O
6.8
1.5
12.9
0.8
53.6
Pavetta zeyheri 5.3
Shrubland
2. Loudetia simplex
-
Vangueria infausta subsp. 4.6
infausta Shrubland
3.
Diheteropogon amplectens
-
Trachypogon 4.6
3.8
1.5
9.0
0.9
65.0
-
Cymbopogon 6.8
1.5
3.0
17.3
0.7
66.3
4.8
2.8
15.6
0.8
67.0
11.2
1.9
17.9
0.9
61.7
17.2
1.8
21.9
0.9
66.5
9.8
1.2
8.2
0.9
77.0
6.0
0.8
1.3
0.9
69.0
spicatus Grassland
4.
Schizachyrium sanguineum
excavatus Grassland
5. Rhus pyroides - Acacia erioloba Woodland
6. Setaria sphacelata var. sphacelata
-
5.7
Acacia 5.0
caffra Woodland
7. Ziziphus zeyheriana - Acacia karroo Woodland
8. Cymbopogon pospischillii
-
4.5
Themeda triandra 5.4
Grassland
9. Setaria incrassata - Hyparrhenia hirta Grassland
3.0
-
2. Loudetia simplex Vangueria infausta subsp. infausta Shrubland
This con-~mur~ity
was associated with the rrlidslopes of the rocky chert outcrops of
the Fa-land type and quartzite ridges of the Fb-land type. The Mispah soil form
was associated with the rocky chert outcrops, whereas the Glenrosa soil form
was associated with the quartzite ridges. The soil in this community was relatively
shallow (< 0.2%) with relatively low clay content (< 10%) and more than 10%
surface rocks.
The differential species of this community were found in species group B (Table
3). These included indigenous species such as the grass Loudetia simplex, the
shrub Mundulea sericea and the forb Helichrysum kraussii. The dominating
shrubs in tl- is con-~mur~ity
included species such as Vangueria infausta subsp.
infausta (species group C , Table 3) and other conspicuous species such as
Zanthoxylum capense and Rhus magalismontana (species group C , Table 3)
forming the shrub component of this community (average canopy cover of 12.9%
and average height of 1.5 m, Table 4). The average height of the tree stratum
was 4.6 m and the average canopy cover was 6.8% with Acacia caffra (species
group N , table 3) forming the major tree component of this community. -The
average canopy cover of the herbaceous stratum was quite high with 53.6% and
an average height of 0.8 m (Table 4). Species forming the herbaceous layer
included grasses such as Trachypogon spicatus, Andropogon schirensis (species
group
El
Table
3),
Schizachyrium
sanguineurn,
Brachiaria
serrata,
Diheteropogon amplectens, Eragrostis racemosa, Melinis nerviglumis, Aristida
meridionalis (species group F, Table 3), Setaria sphacelata var. sphacelata,
Eragrostis curvula (species group T, Table 3), the forb Senecio venosus (species
group E, Table 3) and the succulent Aloe greatheadii var. davyana (species
group N , Table 3). An average number of 34 species was recorded per sample
plot of which 1.6% was exotic species. Exotic plants included species such as
Tagetes minuta (Species Group L, Table 3), Verbena officinalis (Species Group
S, Table 3), Conyza bonariensis, Achyranthes aspera and Nicotiana longiflora
(Species Group V, Table 3).
Cilliers et al. ( I 999) described a closely related community (Vangueria infausta
subsp. infausta - Rhus pyroides Shrubland) sharing a similar habitat with
Loudetia simplex - Vangueria infausta subsp. infausta Shrubland. A similar
community, the Vangueria infausta subsp. infausta
- Acacia
caffra Wood land
was described for the Bc-land type by Bezuidenhout & Bredenkamp (1991).
Although the habitats were quite similar in the communities described, the
dominance of the grass Loudetia simplex in the Loudetia simplex - Vangueria
infausta subsp. infausta Shrubland currently described was one of the major
differences between this
and
other
previously described
communities
(Bezuidenhout & Bredenkamp, 1991; Cilliers et a/., 1999).
-
3. Diheteropogon amplectens Trachypogon spicatus Grassland
Tlie Diheteropogon amplectens - Trachypogon spicatus Grassland occurred
mostly on the stony plains and midslopes of quartzite hills of the Bc- and Fb-land
types. The soil was relatively shallow (< 0.2 m) and consisted of the Hutton,
Mispah and Glenrosa soil forms with relatively rocky surfaces (> 10%).
The species of species group D (Table 3) were the differential species of this
community. These species included the grass Brachiaria nigropedata, the forbs
Helichrysum nudifolium var. nudifolium and Chascanum adenostachyum and the
succulent Aloe zebrina. The dominant grass species in this community were
Diheteropogon amplectens (species group F, Table 3) and Trachypogon spicatus
(species group E, Table 3). These species are typically characteristic for the
relatively dry habitats with shallow rocky soils (Bezuidenhout et al., 1994d).
Other dominant grass species occurring in this community included Cymbopogon
excavatus, Schizachyrium sanguineum, Brachiaria serrata, Eragrostis racemosa,
Melinis nen~iglumis(species group F, Table 3) and Heteropogon contortus
(species group Q, Table 3). The forbs included species such as Senecio
venosus, Gnidia capitata (species group El Table 3), Dicoma anomala (species
group F, Table 3), Aloe greatheadii var. davyana (species group N, Table 3),
Teucrium trifidum (species group Q, Table 3) and Vernonia oligocephala (species
group TI Table 3). The average height of the herbaceous stratum was 0.9 m and
the canopy cover was quite high with 65%. The average height of the tree
stratum was 4.6 m with a canopy cover of 3.8% and Acacia caffra (species group
N, Table 3) formed the main component of this stratum. The average height of
the shrub stratum was 1.5 m with a canopy cover of 9.0% and consisted of
species such as Acalypha angustata, Elephantorrhiza elephantina (species group
F, Table 3) and Ziziphus zeyheriana (species Group Q, Table 3). An average
number of 33 species was recorded per sample plot of which 0.2% was exotic
species. Conyza bonariensis (species group V, Table 3) was the exotic species
found in this community.
A similar community, the Diheteropogon amplectens - Trachypogon spicatus
Grassland from the dolomitic region in the Potchefstroom - Ventersdorp Randfontein area (Bezuidenhout & Bredenkamp, 1990) was previously
described.
Other
closely
related
communities
described
include
the
Diheteropogon amplectens - Schizachyrium sanguineum Grassland from the Fbland type (Bezuidenhout et al., 1994b) and the Schizachyrium sanguineum Diheteropogon amplectens Grassland in the Lichtenburg area (Bezuidenhout et
al., 19944). Cilliers et a/. (1999) also described a closely related community
(Diheteropogon amplectens - Schizachyrium sanguineum Grassland) of the
natural and semi-natural areas in the municipal area of Potchefstroom.
-
4. Schizachyrium sanguineum Cymbopogon excavatus Grassland
This Schizachyrium sanguineum - Cymbopogon excavatus Grassland community
was associated with the rr~idslopesof the relatively shallow rocky soils of the
chert outcrops in the Fa-land type. Mispah and Glenrosa soil forms were
dominant in this community. The ground surface was relatively rocky (> 10%)
with relatively shallow soil (< 0.2 m).
No differential species were identified in this community but it was characterized
by the absence of the species of species groups A and C (Table 3). The
dominant
species were
the
grasses
Schizachyrium
sanguineum
and
Cymbopogon excavatus (species group F, Table 3). Other species such as ,the
grasses Brachiaria serrata, Diheteropogon amplectens (species group F, Table
3), Heteropogon contortus (species group Q , table 3), Eragrostis cun/ula (species
group T, Table 3), and the forbs Dicoma anomala (species group F, Table 3) and
Pseudognaphalium undulatum (species group S, Table 3) in some of the sample
plots, had large cover abundance values. The average height of the herbaceous
stratum was 0.7 m and it had a canopy cover of 66.3 %. The average height of
the tree stratum was 6.8 m with a poor canopy cover of 1.5%. Celtis africana and
Acacia erioloba (species group G, Table 3) were the only tree species occurring
in this community and were very poorly represented. The average height of the
shrub stratum was 3 m and the canopy cover was 17.3%. Rhus pyroides
(species group MI Table 3) was the dominant shrub in this community. An
average number of 54 species was recorded per sample plot of which 0.7% was
exotic species. Exotic plants included species such as Conyza bonariensis and
Achyranthes aspera (species group V , Table 3).
Bezuidenhout & Bredenkamp (1990) described a closely related community,
Aristida diffusa - Cymbopogon excavatus Grassland, also occurring on the stony
chert
areas.
Another
related
community,
Cymbopogon
excavatus
-
Diheteropogon amplectens Grassland, found in the dolomitic and chert outcrops
was described by Bezuidenhout (1994a).
-
5. Rhus pyroides Acacia erioloba Wood land
The Rhus pyroides - Acacia erioloba Woodland was limited to the valley
bottomlands of the chert and dolomitic areas of the Fa-land type. This commurrity
was characterized by relatively rocky ground surface (> 10%) and relatively
shallow soil (< 0.2 m) with a clay content of less than 10%. Sinkholes were
characteristically present in this habitat which was underlain by dolomite and
mostly filled by deep sandy soil (> 1.2 m). Mispah was the dominant soil form in
this community.
The differential species in this community were found in the species group G
(Table 3) and included grasses such as Eragrostis superba, Sporobolus africana,
Eragrostis trichophora, Celtis africana, Acacia erioloba, Diospyros lycioides
subsp. guerkei, lpomoea oblongata, Sida dregei and Striga asiatica. Dominant
plants included species such as Rhus pyroides (species group M, Table 3) and
Acacia erioloba (species group G, Table 3). The average height of the tree
stratum was 5.7 m with a canopy cover of 4.8%. The trees were normally
restricted to the deep sandy soils in the sinkholes. The average height of the
shrub stratum was 2.8 m with a canopy cover of 15.6 m. Other dominant species
in this community included the exotic weed Tagetes minuta (species group L,
Table 3), the shrub Ehretia rigida (species group L, Table 3), the grasses
Triraphis andropogonoides (species group H , Table 3) and Cymbopogon
pospischilii (species group Q, Table 3). The average height of the herbaceous
stratum was 0.8 m with a high canopy cover of 67%, with the succulent Lithops
lesliei also found in this corr~munity(species group V ) . An average number of 40
species was recorded per sample plot of which 4.5% was exotic species. Exotic
plants included species such as Tagetes minuta (Species Group L, Table 3),
Conyza bonariensis, Achyranthes aspera, Bidens bipinnafa and Solanum nigrum
(Species Group V , Table 3).
A closely related community, Rhus lancea - Acacia erioloba, was described by
Bezuidenhout et a/. (1994b).
This comm~~nity
shares a similar floristic
composition with the Rhus pyroides - Acacia erioloba Woodland, except for the
fact that Rhus pyroides was the dominant species in the Rhus pyroides - Acacia
erioloba Woodland described in this study.
-
6. Setaria sphacelata var. sphacelata Acacia caffra Woodland
The Setaria sphacelata var. sphacelata - Acacia caffra Woodland was associated
with the midslopes of the rocky outcrops and quartzite hills. The habitat was
relatively dry with shallow soil (< 0.2 m) and a well-drained systeni and was
characterized by a relatively low clay content (< 10%). Mispah, Glenrosa and
Hutton were the dominant soil forms.
The differential species in this community were found in species group I (Table
3). These included species such as the grasses Digitaria eriantha, Eragrostis
rigidior, Aristida transvaalensis, the forbs Crabbea angustifolia, Blepharis
integrifolia, Indigofera heterotricha, Chaetacanthus costatus, the tree Euclea
undulata and the shrub Rhus leptodictya. Dominant species in this community
included species such as Setaria sphacelata var. sphacelata (species group T,
Table 3) and Acacia caffra (species group N , Table 3). Other co-dominant
species in this community included the forbs Pseudognaphalium undulatum, the
succulent Aloe greatheadii var. davyana, the climber Clematis brachiata (species
group N , Table 3), the shrub Ziziphus zeyheriana (species group Q , Table 3) and
the tree Acacia karroo (species group S, Table 3). -The average height of the tree
stratum was 5.0 m and had a canopy cover of 11.2%. -The average height of the
shrub stratum was 1.9 m with a canopy cover of 17.9%. The herbaceous stratum
was 0.9 m high on average, and had a canopy cover of 61.7%. An average
number of 40 species was recorded per sample plot of which 6.6% was exotic
species. Exotic plants included species such as Tagetes minuta (Species Group
L, Table 3), Verbena officinalis (species group S, Table 3), Paspalum dilatatum,
Conyza bonariensis, Achyranthes aspera, Bidens bipinnata, Gomphrena
celosioides, Schkuhria pinnata, Verbena bonariensis, Gulleminea densa,
Plantago lanceolata, Solanum sisymbriifolium, Chenopodium album, Opuntia
ficus-indica, Oxalis corniculata, Zinnia peruviana, Oenothera tetraptera and
Cirsium vulgare (Species Group V , Table 3).
Bezuidenhout et a/. (1994~)and Cilliers et a/. (1999) described a closely related
community, Rhus leptodictya - Acacia caffra Woodland.
The reason for the
difference in floristic composition between these two communities might be due
to the fact that the vegetation was often subjected to overgrazing, resulting in
degradation and the subsequent presence of many pioneer species and exotic
species. Another related community, Vangueria infausta - Acacia caffra
Woodland, described by Bezuidenhout & Bredenkamp (1991), occurs in a similar
habitat but with Eragrostis cun/ula and Panicum coloratum as dominant grasses.
The Setaria sphacelata var. sphacelata
- Acacia
caffra Woodland described in
this study consists of Setaria sphacelata var. sphacelata, Digitaria eriantha,
Eragrostis rigidior and Aristida transvaalensis as dominant grasses. Uncontrolled
fires, gathering of firewood and accompanying disturbances such as trampling
and soil compaction are the most important threats to these communities (Cilliers
et al., 1999).
-
7. Ziziphus zeyheriana Acacia karroo Woodland
The Ziziphus zeyheriana
-
Acacia karroo Woodland occurred on footslopes,
valley bottomland areas, and along ,the drainage lines and midslopes of the
quartzite hills. This community was characterized by relatively deep soil (> 0.5 m)
with a relatively high clay content (> 25%). Hutton and Shortlands were the
dominant soil forms in this community.
The differential species in this community were found in species group J (Table
3). These species included Delosperma herbeum, Nidorella anomala, Sida
spinosa, Pavonia burchellii, Pollichia campestris, Pentzia globosa and Eragrostis
lehmanniana. Dominant plants included species such as Ziziphus zeyheriana
(species group Q , Table 3) and Acacia karroo (species group S, Table 3). Other
co-dominant species in this community included species such as Asparagus
suaveolens (species group K, Table 3), Ehretia rigida (species group L, Table 3),
Aloe greatheadii var. davyana (species group N , Table 3), Clematis brachiata
(species group N , Table 3),
Acacia caffra (species group N , Table 3),
Cymbopogon pospischilii (species group Q, Table 3), Ziziphus zeyheriana
(species group Q , Table 3), Teucrium trifidum (species group Q , Table 3),
Cynodon dactylon (species group S, Table 3), Asparagus laricinus (species
group S, Table 3) and Setaria sphacelata var. sphacelata (species group T,
Table 3). The average height of the tree stratum was 4.5 m and it had a canopy
cover of 17.2% (Table 4). The average height of the shrub stratum was 1.8 m
with a canopy cover of 21.9%. The average height of the herbaceous stratum
was 0.9 m and had a canopy cover of 66.5% (Table 4). An average number of 41
species was recorded per sample plot of which 7.2% exotic species. Exotic
plants included species such as Tagetes minuta (Species Group L, Table 3),
Verbena officinalis (Species Group S, Table 3), Conyza bonariensis, Achyranthes
aspera, Bidens bipinnata, Gomphrena celosioides, Lepidium bonariensis,
Schkuhria pinnata, Solanum sisymbriifolium, Opuntia ficus
-
indica, Oxalis
corniculata and Zinnia peruviana (Species Group V , Table 3).
Bredenkamp et al. (1988) described a similar community (Acacia karroo
Woodland) in the Potchefstroom-Fochville-Parys area with Ziziphus zeyheriana
abundantly occurring on severely degraded areas. Bezuidenhout & Bredenkamp
(1 991) also described an Acacia karroo community with a similar floristic species
composition such as Asparagus laricinus, Acacia karroo, Pavonia burchellii and
Teucrium trifdum. -TI-ris commurrity also corresponds to the Thornveld described
by Louw (1951).
-
8. Cymbopogon pospischilii Themeda triandra Grassland
The Cymbopogon pospischilii - Themeda triandra Grassland was associated with
the midslopes of the rocky quartzite outcrops. This corr~munitywas characterized
by a relatively shallow soils (> 0.2 m) of the Hutton and Glenrosa soil forms with
a low clay content (>looh) and a good drainage regime.
The differential species in this community were found in species group 0 (Table
3). Cymbopogon pospischilii (species group Q , Table 3) and Themeda triandra
(species group U, Table 3) were the dominant species in this community. Other
co-dominant species in this community included species such as Hermannia
depressa (species group P, Table 3), Ziziphus zeyheriana (species group Q,
Table 3), Berkheya radula (species group R, Table 3), Hyparrhenia hirta (species
group R, Table 3), Setaria incrassata (species group R, Table 3), Helichrysum
nudifolium var. nudifolium (species group R, Table 3), Acacia karroo (species
group S, Table 3) and Conyza podocephala ((species group S, Table 3). The
average height of the tree stratum was 5.4 m with a canopy cover of 9.8%. The
average height of the shrub stratum was 1.2 m with a canopy cover of 8.2%. The
average height of the herbaceous stratum was 0.9 m with a high canopy cover of
77%. An average number of 31 species was recorded per sample plot of which
6.3% was exotic species. Exotic plants included species such as Tagetes minuta
(Species Group L, Table 3), Verbena officinalis (Species Group S, Table 3),
Conyza bonariensis, Achyranthes aspera, Avena fatua, Bidens bipinnata,
Gomphrena celosioides, Physalis angulata, Oenothera rosea, Oenothera
tetraptera and Cirsium vulgare (Species Group V , Table 3).
Bredenkamp et al. (1989) described a closely related community (Themeda
triandra - Elionurus muticus Grassland) similar to the Themeda triandra Heteropogon contortus variant described by Bredenkamp & Bezuidenhout
(1989), with an absolute dominance of Themeda triandra. The Cymbopogon
pospischilii -
Themeda triandra Grassland also
shows similar floristic
characteristics with the Themeda trianda variant described by Bezuidenhout &
Bredenkamp (1991) in the Bc-land type. The dominant grass species in these
communities are Eragrostis plana, Cymbopogon pospischilii and Themeda
triandra with Berkheya radula as the prominent forb.
9. Setaria incrassata - Hyparrhenia hirta Grassland
The Setaria incrassata - Hyparrhenia hirfa Grassland was mostly a wetland
community restricted to the valley bottomlands and floodplains in or along
drainage lines. The geology comprises mostly of alluvial deposited from the
upper slopes. The relatively high clay content (> 25 %) causes soil to swell and
shrink on wetting and drying. This habitat was fairly unstable due to seasonal
flooding and drying. Hutton and Swartland were the dominating soil forms found
in this community.
No differential species were identified in this community. Setaria incrassata
(species group R , Table 3) and Hyparrhenia hirta (species group R , Table 3)
were the dominant species in this community. The average height of the
herbaceous shrub stratum was 0.9 m with a high canopy cover of 69% (Table 4).
Other co-dominant species found in this community included Berkheya radula
(species group R , Table 3), Eragrostis plana (species group R , Table 3), Conyza
podocephala (species group S , Table 3), Acacia karroo (species group S, Table
3), Asparagus laricinus (species group S , Table 3) and Cynodon dactylon
(species group S , Table 3). The average height of the shrub stratum was 0.8 m
with a poor canopy cover of 7.3 % (Table 4). The average height of the tree
stratum was 3 m with a canopy cover of 6% (Table 4). An average number of 24
species was recorded per sample plot of which 12% was exotic species. Exotic
plants included species such as Verbena officinalis (Species Group S , Table 3),
Paspalurn diiataturn, Conyza bonariensis, Ciclospermum leptophyllum, Persicaria
lapathifolia, Oenothera rosea and Oenothera fetraptera (Species Group V , Table
3).
Several studies have been done on similar wetland grassland communities by
different researchers. Bredenkamp et a/.(1989) described an Aristida bipartita -
Eragrostis plana - Setaria sphacelata Grassland in the Potchefstroom-FochviIleParys area; Bezuidenhout & Bredenkamp (1991) described an Eragrostis plana
Grassland in the vegetation of the Bc-land type in the western Transvaal;
Bredenkamp et al. (1994) described a Hyparrhenia hirta Grassland in the Boskop
Dam Nature reserve; Bezuidenhout et a/.(1994c) described a Hyparrhenia hirta -
Eragrostis plana Grassland in the Fb-land type in the old western Transvaal; and
Cilliers et a/. (1998) described a Hyparrhenia hirfa Grassland in the
Potchefstroom municipal area. The similarity found in all these communities is
that their habitats are fairly unstable due to seasonal flooding and drying which,
together with the frequent overgrazing of these sites, caused an advanced state
of degradation of the vegetation.
3.5 ORDINATION
A Detrended Correspondence Analysis (DCA) ordination algorithm was applied
to the data set to confirm the existence of the different plant communities and to
determine whether the gradients in plant communities along different ordination
axes could be explained by gradients in specific environmental characteristics. It
will be an indirect gradient, as few quantitative environmental characteristics
were studied and therefore impossible to study direct gradients using Canonical
correspondence analysis (CCA).
The stepwise ordination approach followed by Mucina & van Tongeren (1989)
was adopted to cope with the heterogeneity of the data set and therefore, two
different ordinations were completed (Figures 4 and 5). The scatter diagram in
Figure 4 shows the DCA ordination with all releves of the entire HNP. The
relative positions of points on the second axis are clustered and the different
plant communities cannot be clearly distinguished from each other (Figure 4).
The scatter diagram in Figure 5 shows a second DCA ordination after the
removal of an outlier relev6 80. There is a significant change in the distribution of
points on the second axis and the plant communities 1, 2, 3, 4 and 5 show some
dissimilarity with the other communities (Figure 5). The gradient along ordination
axis 1 (E = 0.65) could be explained by environmental characteristics such as
moisture, surface rockiness, soil depth and soil clay content (Figure 5). Plant
communities to the left side of the scatter diagram are characterized by a
relatively dry habitat, high percentage of surface rockiness, shallow soil and
relatively low clay content, while those on the right are characterized by a
relatively wet habitat, low percentage of surface rockiness, deeper soil and
reiatively high clay content (Figure 5). The gradient along ordination axis 2 (E =
0.45) could be explained by altitude.
Plant communities at the top of the scatter diagram (Figure 5) are mainly limited
to the upper slopes, rocky quartzite hills and ridges, crests and dolomitic areas in
the HNP. These are mainly woodlands and shrublands communities found in
high altitudes, Plant communities found at the bottom of the scatter diagram
(Figure 5) are associated with low altitudes and occur mainly in the footslopes
and bottomlands in the HNP.
I
4
r
I
I
I
1
-2
I
Ordination Axis I
8
Figure 4. First Detrended Correspondence Analysis ordination with all
releves in the Highveld National Park (Plant community 1 = Mystroxylon
aethiopicum - Pavetta zeyheri Shrubland; 2 = Loudetia simplex - Vanguen'a
infausta subsp. infausfa Shrubland; 3 = Diheteropogon arnplectens Trachypogon spicatus Grassland; 4 = Schizachyrium sanguineum Cymbopogon excavatus Grassland; 5 = Rhus pyroides - Acacia erioloba
Woodland; 6 = Setaria sphacelata var. sphacelata - Acacia caffra Woodland;
7 = Ziziphus zeyheriana - Acacia karroo Woodland; 8 = Cymbopogon
pospischilii - Themeda triandra Grassland; 9 = Setan'a incrassata Hyparrhenia hirta Grassland).
Reladvely Dry
Relaet.elym
Relatively SWolr
Rehtively LOIT
+
+
+
-
Ordination Axis -l
E = 0.65
hloisnn'e
>-
Roc.hess
D e p ~
Clay C'outeut
>>-
ReQtix:ely \Vet
Relatively LOW
Relatively Deey
Relatively
Figure 5. Second Oetrended Correspondence Analysis ordination with
87 releves in the Highveld National Park (Plant community I= Mystroxylon
aethiopicum - Pavefta zeyheri Shrubland; 2 = Loudetia simplex
-
Vangueria
infausta su bsp. infausta S hru bland; 3 = Diheteropogon amplectens Trachypogon spicatus Grassland; 4
= Schizachyrium sanguineum -
Cymbopogon excavatus Grassland; 5 = Rhus pyroides - Acacia eriuloba
Woodland; 6 = Setaria sphacelata var. sphacelata - Acacia caffra Woodland;
7 = Ziziphus zeyheriana
- Acacia karroo Woodland;
8 = Cymbopogon
pospischilii - Themeda triandra Grassland; 9 = Setaria incrassata Hyparrhenia hirta Grassland).
3.6 CONCLUSION
Three structural vegetation units, namely woodland, shrubland and grassland
were identified in the HNP. The DCA-ordination also confirmed the relationship
between the plant communities and the environmental gradients in the HNP.
Many of the communities showed some floristic similarity to previously described
plant communities for the Bc- (Bezuidenhout & Bredenkamp, 1991), f a (Bezuidenhout et a/., 1994b) and Fb-land types (Bezuidenhout et a/., 1994~).
Similar communities were also described by Cilliers et a/. (1998, 1999) in the
phytosociological studies of the urban spaces in Potchefstroom. Differences in
floristic composition were also found between plant communities of the HNP and
those previously described in the grassland of the former western Transvaal. The
differences are probably due to the effect of numerous disturbances such as
uncontrolled fires and other accompanying factors such as overgrazing and
trampling, which result in soil compaction. The habitat and floristic composition of
the plant communities of the rocky hills and ridges and shallow soils in the
undulating landscape indicated that these communities represent Bankenveld
rather than Cymbopogon - Themeda Veld of Acocks (1988). The description of
the plant communities in the HNP also showed floristic similarities to the broader
Grassland Bioregion Unit (Gh 12, Gh 13, Gh 15 and Gm 11) and the Central
Bushveld Bioregion Unit (SVcb 11) described by Mucina & Rutherford (2006).
The current classification, together with the description and ecological
interpretations of the vegetation and associated habitats should form a basis for
all vegetation-related management and conservation planning in the region.
CHAPTER 4
CLASSIFICATION AND DESCRIP-UON OF VEGETATION
IN THE DEGRADED SPITSKOP AREA
4.1 INTRODUCTION
The relationship between vegetation and soil erosion deserves attention due to
its scientific importance and
practical applications (Guerrero-Campo &
Montserrat-Marti, 2000). Vegetation reduces soil erosion and, as a consequence,
many studies have been devoted to understanding the interaction between
vegetation and erosion (Morgan & Rickson, 1995). However, the effect of soil
erosion on vegetation is still poorly understood, especially with regard to the
ecological aspects. Phytosociological studies of vegetation from eroded areas
are also rare, but could be quite useful in providing vegetation and habitat
information of degraded areas (Morgan & Rickson, 1995). This scarcity is
possibly due to the characteristicly poor species composition of such degraded
communities in comparison to those of the better conserved neighbouring areas
(Guerrero-Campo & Montserrat-Marti, 2000). From an ecological viewpoint it is
considered that the erosion process provokes high levels of stress and
disturbance on plant species of the affected communities (Guerrero-Campo &
Montserrat-Marti, 2000).
The Spitskop area in the HNP is characterized by pronounced soil degradation
and therefore necessitates a detailed survey in order to determine plant
communities and different types of soil erosion in the area. The objective of this
chapter was therefore to classify, describe and map the plant communities
occurring in the degraded sites of the Spitskop area. The geology of the area, soil
forms, terrain units, and rockiness of the surface area were used in describing
the plant communities. The types of erosion associated with the plant
communities are briefly mentioned in this chapter but a detailed description will
follow in Chapter 5. The percentages of exotic species in different communities
are also indicated to show the extent of their invasion and the need for
management intervention. A comparison (where applicable) was made between
the plant communities of the degraded areas and those described for the HNP
(Chapter 3) and previously described communities in the grassland of the former
western Transvaal.
4.2 CLASSIFICATION
The vegetation analyses are given in a phytosociological table (Table 5) and
resulted in the formulation of a vegetation map (Figure 6) and the recognition of
three major plant communities and three sub-communities. The hierarchical
classification of these communities was as follows:
1 . Seriphium plumosum- Acacia caffra Woodland
I. 1Melinis repens - Acacia robusta Woodland
1.2 Eragrostis racemosa - Mundulea sericea Shrubland
1.3 Asparagus suaveolens - Acacia karroo Shrubland
2. Setaria sphacelata var. torta - Eragrostis curvula Grassland
3. Cymbopogon pospischilii - Eljonurus rnuticus Grassland
4.3 BRIEF DESCRIPTION OF PLANT COMMUNITIES
1, The Senphiurn plumosum - Acacia caffra Woodland was situated on the rocky
quartzite midslopes of the Spitskop hill.
1.I. The Melinis repens - Acacia robusta Woodland was limited to the northeastern gradual midslope of the quartzite Spitskop hill.
1.2.
The Eragrostis racemosa - Mundulea sericea Shrubland was limited to the
north-eastern steeper midslope of the rocky quartzite Spitskop hill.
1.3.
The Asparagus suaveolens - Acacia karroo Shrubland generally occurred
on gradual footslopes in the south-western areas of the quartzite Spitskop
hill.
2. The Setaria sphacelata var. torta - Eragrostis cuwula Grassland occurred on
the footslopes of the quartzite Spitskop hill.
3. The Cyrnbopogon pospischili
- Elionurus muticus
Grassland occurred in the
valley bottomland and floodplains along the drainage lines.
4.4 DETAILED DESCRIPTION OF PLANT COMMUNITIES
I. Seriphium plumosum- Acacia caffra Woodland
The Seriphium plumosum - Acacia caffra Woodland occurred on the rocky
quartzite midslopes of the Spitskop hill. This community was characterized by the
presence of sheet gully and rill erosion (Table 6). The habitat was relatively dry
and characterized by well-drained, relatively shallow soil (< 0.2 m), with a
relatively low clay content (< 10%). Glenrosa was the dominant soil form in this
community. The percentage of surface rocks was high (> 10%).
The differential species of this community were found in species group A (Table
5) and included species such as Acacia caffra, Seriphium plumosum,
Gomphocarpus fruticosus subsp. fruticosus, Aristida bipartita and Convolvulus
sagittatus. The abundance of karroid shrubs such as Seriphium plumosum
(species group A, Table 5) may become dominant in degraded and overgrazed
areas (Acocks, 1988; O'Connor & Bredenkamp, 2003). Other dominant species
found in this community included the forb Convolvulus sagiffatus, the grasses
Aristida bipartita (species group A, Table 5), Eragrostis racemosa, Urochloa
panicoides (species group H , Table 5) and the two shrubs Rhus pyroides and
Euclea undulata (species group H, Table 5). Species of general occurrence were
found in species group M (Table 5).
Table 5. A phytosociological table of the Spitskop degraded area in the Highveld National Park.
Number of releves
Plant Community
Sub-community
SPECIES GROUP A
1121 3
1.I
17
13 1 4 1 5
1
1.2
6
8
9
10
11112
.14
- - 15
2
1.3
16
17
18119
3
20
Plant Community
Sub-community
Setaria pallide-fusca
Sida rhornbifolia subsp. rhombifolia
Sida spinosa var, spinosa
1
c
1
Plant Community
Sub-cornmunit
Table 6. Summary of soil degradation types affecting plant communities in
the Spitskop area in the Highveld National Park.
Plant community
I . Seriphiurn plumosum
- Acacia cafra
Woodland
I.I Melinis repens
-
Acacia
Severity class
Sheet
High - Severe
Rill
Severe
Gully
Slight
robusfa Sheet
Wodland
1.2 Eragrostis racemosa
Degradation type
Gully
-
Mundulea Rill
sericea Shrubland
Sheet
1.3 Asparagus suaveolens
-
Acacia Sheet
karroo Shrubland
2. Setaria sphacelata var. torta
3 . Cymbopogon pospischilli
- Elionurus
Slight
Severe
High - Severe
Slight - Moderate - Severe
Rill
Severe
Gully
Slight
- Sheet
Eragrostis curvula Grassland
Severe
High -Severe
Rill
High - Severe
Gully
Slight
Compact soil
Severe
mutichus Grassland
The average height of the tree stratum was 1.6 m with a canopy cover of 10.5%
(Table 7). The average height of the shrub stratum was 0.5 m with a canopy
cover of 5.7% (Table 7). The average height of the herbaceous layer was 0.2 rn
with a canopy cover of 3.1% (Table 7). An average number of 18 species was
recorded per sample plot of which 2.1% was exotic species. Exotic plants
included species such as Gomphrena celosioides (Species Group I, Table 5),
Solanum elaeagnifolium and Opuntia ficus-indica (Species Group N, Tabie 5).
The Seriphium plumosum - Acacia caffra Woodland was related to the Setaria
sphacelata var. sphacelata - Acacia caffra Woodland described in chapter 3, but
the Seriphiurn plumosum - Acacia caffra Woodland was mainly restricted to the
-
degraded areas at Spitskop hill. Wood harvesting also contributed to degradation
of this community. Bezuidenhout et a/. (1994~)also stated that the reason for
differences in floristic composition might be due to the fact that the vegetation is
often subjected to overgrazing, resulting in degradation and subsequent
presence of many pioneer species and exotic species. Bezuidenhout et al.
(1994~)and Cilliers ef a/. (1999) described a similar, but less degraded
community (Rhus leptodictya - Acacia caffra Woodland) in the Potchefstroom
area.
The Seriphium plumosum
-
Acacia caffra community was divided into three
subcommunities, which are discussed below.
-
1.1 Melinis repens Acacia robusta Woodland
The Melinis repens - Acacia robusta Woodland was limited to the gradual northeastern midslope of the quartzite Spitskop hill. This community was severely
affected by sheet erosion (Table 6) and was characterized by well-drained,
relatively shallow soil (< 0.2 m) with a relatively low clay content (< 10%).
Glenrosa was the dominant soil form in this community.
The differential species of this community were found in species group B (Table
5) and included the grass Panicum maximum and the tree Acacia robusta.
Dominant shrubs in this community included species such as Diospyros lycioides
subsp. lycioides (species group D, Table 5) and Euclea undulata (species group
H , Table 5). The average height of the herbaceous stratum was 0.2 m with a low
canopy cover of 1.O% (Table 7). The average height of the tree stratum was I.3
m with a canopy cover of 5.2% (Table 7). The average height of the shrub
stratum was 0.5 m with canopy cover of 1.8 % (Table 7). An average number of
16 species was recorded per sample plot of which 3.7% was exotic species.
Exotic plants included species such as Gomphrena celosioides, Solanum
elaeagnifolium and Opuntia ficus-Mica (species group N , Table 5).
I .2 Eragrostis racemosa - Mundulea sericea S h rubland
The Eragrostis racemosa - Mundulea sericea Shrubland was limited to the
gradual north-eastern midslope of the rocky quartzite Spitskop hill. This
community was affected by sheet and rill erosion (Table 6). The soil was
relatively shallow (< 0.2 m), well-drained and characterized by a relatively low
clay content (< 10%) and a relatively high percentage of surface rocks (> 10%).
The dominant soil form was Glenrosa.
The differential species in this community was found in species group C (Table 5)
consisting of only one species, lndigofera sp. and the community was
characterized by the absence of species group B (Table 5). Dominant species in
this community were Eragrostis racemosa (species group H , table 5) and
Mundulea sericea (species group F , Table 5). Other co-dominant species found
in this community included trees such as Acacia caffra (species group A, Table
5), Acacia karroo (species group L, Table 5), the shrubs Diospyros iycioides
subsp. lycioides (species group D, Table 5), Rhus pyroides (species group H ,
table 5) and the grasses Eragrostis lehmanniana (species group K, Table 5),
Urochloa panicoides (species group H , Table 5) and Setaria sphacelata var.
sphacelata (species group L, Table 5). The average height of the herbaceous
layer was 0.1 m with a canopy cover of 2.3 % (Table 7). The average height of
the tree stratum was 1.5 m with a canopy cover of 9.3 % (Table 7). The average
height of the shrub stratum was 0.5 m with a canopy cover of 5.3 % (Table 7). An
average number of 17 species was recorded per sample plot and no exotic
species were recorded.
Table 7. Average height and cover values of the trees, shrubs and herbaceous layers of the different plant
communities in the Spitskop area in the Highveld National Park.
Stratum
Community
Trees
Herbaceous
Shrubs
Average
Average
Average
Average
Average
Average
Height (m)
Cover (%)
Height (m)
Cover (%)
Height (m)
Cover (%)
1. Seriphium plumosum - Acacia caffra Woodland
7.6
10.5
0.5
5.7
0.2
3,l
I.7 Melinis repens - Acacia robusta Wodland
1.3
5.2
0.5
7.8
0.2
1.0
7.2 Asparagus
suaveolens
-
Acacia
karroo I.5
9.3
0.5
5.3
0.7
2.3
suaveolens
-
Acacia
karroo 2.1
77.0
0.6
70.0
0.2
6.0
- Eragrostis cun/ula 7.2
71,2
0.3
6.8
0.2
5.4
Elionurus mutichus
0.5
0.6
1.0
0.4
2.9
Shrubland
1.3 Asparagus
Shrubland
2. Setaria sphacelafa var. torta
Grassland
3. Cymbopogon pospischilli
Grassland
-
I.0
-
1.3 Asparagus suaveolens Acacia kanoo Shrubland
This sub-community occurred in the south-western footslopes of the quartzite
Spitskop hill and can be regarded as a transition from Acacia caffra to Acacia
karroo Woodland. This community was affected by sheet, rill and gully erosion
(Table 6). The soil was moderately deep (0.2 - 0.5 m) with less than 10% surface
rocks. Hutton and Glenrosa were the dominating soil forms in this subcommunity.
The differential species in this community were found in species group E (Table
5) and included species such as Senecio sp., Atriplex sp. and Lantana rugosa.
Acacia karroo (species group L, Table 5) and Acacia caffra (species group A,
Table 5) were the dominant trees in this community. The average height of the
tree stratum was 2.1 rn with a canopy cover of 17% (Table 7). Dominating shrubs
included species such as Asparagus suaveolens (species group M , Table 5),
Seriphium plumosurn (species group A, Table 5), Rhus pyroides (species group
H , Table 5) and Ziziphus zeyheriana (species group L, Table 5). The average
height of the shrub stratum was 0.6 m with a canopy cover of 10% (Table 7).
Dominating grasses included species such as Aristida biparfita (species group A,
Table 5), Eragrosfis racemosa (species group H , Table 5), Urochloa panicoides
(species group H , Table 5) and Setaria sphacelata var. sphacelafa (species
group L, Table 5). The average height of the herbaceous stratum was 0.2 m with
a canopy cover of 6.0% (Table 7). An average number of 21 species was
recorded per sample plot of which 1.9% was exotic species. Exotic plants
included species such as Gomphrena celosioides and Opunfia ficus-indica
(Species Group N , Table 5).
This community is related to the Ziziphus zeyheriana - Acacia karroo Woodland
described in Chapter 3. The difference between the two communities is the
dominance of Ziziphus zeyheriana (species group Q, Table 3) in the Ziziphus
zeyheriana - Acacia karroo Woodland and Asparagus suaveolens (species
group M, Table 5) in the Asparagus suaveolens - Acacia karroo Woodland. This
degraded community was characterized by a low average number of indigenous
species and a high percentage of exotic species in comparison to the Ziziphus
zeyheriana - Acacia karroo Woodland described in Chapter 3. A similar
community (Acacia karroo Woodland) was described by Bredenkamp ef a/.
(1988) in the Potchefstroom-Fochville-Parys area. A similar community was also
described by Bezuidenhout & Bredenkamp (1991) for the footslope and
bottomlands of the Bc-land type in the Potchefstroom area. Cilliers &
Bredenkamp (1998) described another similar community in the vegetation
analysis of railway reserves in Potchefstroom area. The Asparagus suaveolens Acacia karroo Shrubland also corresponded to the Thornveld described by Louw
(1951).
-
2. Setaria sphacelata var. torta Eragrostis curvula Grassland
The Sefaria sphacelafa var. forta - Eragrostis curvula community occurred on the
footslopes of the quartzite Spitskop hill and was also affected by sheet, rill and
gully erosion (Table 6). The soils were relatively deep (> 0.5 m) and had a
relatively high clay content (> 25%). The soil forms that were present in this
community were Hutton and Mispah. This community represented a transitional
zone between woodland and grassland.
The differential species in this community were found in species group G (Table
5). These species included grasses such as Eragrostis curvula, Digitaria eriantha
and Setaria sphacelata var. torfa, the shrubs Grewia flava and Asparagus
lan'cinus and the forb Solanum lichtensteinii, Other dominating species included
Acacia karroo (species group L, Table 5), Rhus pyroides (species group H , Table
5) and Chrysocoma ciliata (species group K). The average height of the tree
stratum was 1.2 m with a canopy cover of 11.2% (Table 7). The average height
of the herbaceous layer was 0.2 m with a canopy cover of 5.4 % (Table 7).
Species such as Aloe greatheadii var. davyana occurred abundantly and its
cover seemed to increase under conditions of severe degradation. The average
height of the shrub stratum was 0.3 m with a canopy cover of 6.8 % (Table7). An
average number of 23 species was recorded per sample plot of which 4.2% was
exotic species. Exotic plants found in this community included species such as
Gomphrena celosioides, Plantago lanceolata, Oxalis corniculata and Solanum
elaeagnifolium (Species Group N , Table 5).
This community was encroached by Acacia karroo and disturbed areas were
enhanced by changes in the competitive balance between grasses and bush,
brought about by changes in grazing and/or fire regimes in the management of
the grasslands (Friedel, 1987). Related communities were described by
Bezuidenhout et al. (I
994) for the Ba-land type in the former western T ransvaal,
Bezuidenhout & Bredenkamp (1991) for the Bc-land type and Bredenkamp et a/.
(1989) in the Potchefstroom-Fochville-Parysarea.
-
3. Cymbopogon pospischilii Elionurus muticus Grassland
The Cymbopogon pospischilii - Elionurus muticus Grassland occurred in the
valley bottomland and floodplains along drainage lines. The geology of this
landscape mostly comprised of alluvial deposits from the upper slopes. This
community was also characterized by bare batches of compacted soil resulting
from overgrazing and trampling (Bezuidenhout ef al., 1994). Mispah and Hutton
were the dominant soil forms in this community.
The differential species for this community were found in species group I (Table
5). These species included grasses such as Elionurus muticus, Eustachys
paspaloides and Aristida congesta su bsp. congesta, the dwarf shrub Sida alba,
the forb Vernonia oligocephala and the exotic plant Gomphrena celosioides.
Dominant plants in this community included the grasses Cymbopon pospischillii
(species group J ) and Elionurus muticus (species group I, Table 5). Other codominant species included Setaria sphacelata var. sphacelata, the tree Acacia
karroo and the shrub Ziziphus zeyheriana (species group L, Table 5). The
average height of the tree stratum was 1.0 m with a canopy cover of 0.5% (Table
7). The average height of the shrub stratum was 0.6 m with a canopy cover of
1.0% (Table 7). The average height of the herbaceous layer was 0.4 m with a
canopy cover of 2.9 % (Table 7). An average number of 17 species was recorded
per sample plot of which 4.4% was exotic species. Exotic plants included species
such as Gomphrena celosioides and Oxalis corniculata (Species Group N , Table
5).
A Similar community (Elionurio mutici - Cymbopogonnefum plurinodis ass. nov.)
was described by Bezuidenhout et a/. (1994) for the Ba-land type in the former
western Transvaal grassland. Another related community (Elionurus muticus Acacia karroo Woodland) for the Bc-land type in the former western Transvaal
grassland was described by Bezuidenhout & Bredenkamp (1991).
4.5 ORDINATION
A DCA ordination algorithm was applied to the data set to confirm the existence
of the different plant communities and to determine whether the gradients in plant
communities along different ordination axes could be explained by gradients in
specific environmental characteristics. A scatter diagram was produced to show
the relationship between the plant communities in the Spitskop area, HNP
(Figure 7). Plant communities 1 and 2 and to a lesser extent plant community 3
form clear and separate groups. The three subcommunities of plant community I
did not, however, show any clear dissimilarity. The gradient along ordination axis
I (E = 0.39) could be explained by soil depth, soil moisture, surface rockiness
and clay content (Figure 7). The plant communities on the left of the scatter
diagram are characterized by relatively shallow soil with relatively low clay
content and dry habitat, while those on the right are characterized by relatively
deep soil with relatively high clay content and wet habitat. The gradient along
ordination axis 2 (E = 0.23) could be explained by altitude. The grassland
communities at the top centre of the scatter diagram are more or less found at
lower altitudes and shrubland and woodland communities at the bottom left of the
scatter diagram are found at relatively high altitudes (Figure 7).
For the environmental gradient analysis, the direct ordination (Canonical
Correspondence Analysis
between
plant
- CCA)
communities
was employed to determine the correlation
and
soil
erosion
gradients
(quantitative
environmental variables). This was done using the CANOCO software
programme (Ter Braak, 1986). The environmental gradients and the relative
importance and intercorrelation of the environmental variables and the position of
the releves of the different plant communities in relation to the environmental
gradient are shown in Figure 8. The length of an arrow is proportional to its
importance and the angles between the arrows reflect the intercorrelations
between the variables. The angle between an arrow and each axis is a
representation of its degree of correlation w~ththe axis.
Compacted soil (Corn.) is most highly correlated with ordination axis 1 (figure 8)
and the CANOCO results confirms this correlation as 0.82 (Table 8). Sheet
erosion is most highly correlated with ordination axis 2 and the correlation
coefficient is 0.65 (Table 8). In other words there is a soil compaction gradient
along ordination axis 1 with higher percentage to the right and lower percentage
to the left, and a sheet erosion gradient along ordination axis 2 with higher
percentage at the top and lower percentage at the bottom.
Plant Communities
f.1
Ordination Axis I
-<
-<
Relatively Dry
Relatkely High
Relathreh' S M l o ~ r-<
Relak:e@ ~ o r r
<
,-
>-
Moisture
Rockiness
Soil depth
Clay content7
-
>>-
Relatjvell-Ket
Relativeb Lorr
Relath:eQ DecV
Relati~.eh.Bgh
Figure 7. A Detrended Correspondence Analysis ordination with all releves
in the Spitskop area in the Highveld National Park (Plant community 1.1 =
Melinis repens - Acacia robusta Woodland; 1.2 = Eragrostis racemosa Mundulea sericea Shrubland; I .3 = Asparagus suaveolens - Acacia karroo
Shrubland; 2 = Setaria sphacelata vat-. torfa - Eragrostis curvula Grassland; 3 =
Cymbopogon pospischilii - Elionurus muticus Grassland).
Plant Communities
a
1.1
mr.2
+ 1.3
A z
3
..-...-----A-
20 l
-0-6
Ordination Axis 1
E = 0.28
a
1-0
Figure 8. Canonical Correspondence Analysis showing correlation between
plant communities and soil erosion gradients in the Spitskop area in the
Highveld National Park (She. = Sheet erosion, Gufcm = Gully erosion, Rilcm =
Rill erosion, Com. = Compacted soil. Plant community 1.1 = Meiinis repens
-
Acacia robusta Woodland; 1.2 = Eragrostis racemosa - Munduiea sericea
Shrubland; 1.3 = Asparagus suaveolens - Acacia karroo Shrubland; 2 = Setaria
sphacelata var. totfa
-
Eragrostis curvula Grassland; 3 = Cymbopogon
pospischilii - Eiionurus muticus Grassland).
Table 8. Information used i n a Canonical Correspondence Analysis of the
Spitskop area i n the
Highveld National Park, showing correlation
coefficients, eigen values and percentage variance of ordination axes 1 and
2.
Factor
Axis I
Axis 2
Sheet
-0.53
0.65
Gully
-0.54
-0.28
Rill
-0.24
-0.23
Compacted Soil
0.82
-0.45
Eigen value
0.28
0.23
Oh variance
34.9
63.5
The Eigen value for ordination axis 1 of the plant community/environment biplot
is 0.28 and the second axis is 0.23, representing 34.9 % and 63.5% of the total
variance respectively (Table 8). Thus, the first two axes account for 28% of the
variance in the plant community/environment data. Releves of plant community 3
occur to the bottom right of Figure 8, and are associated with compacted soil.
Sheet erosion is associated with plant community 1 (1.I,
1.2 and I.3) and 2, and
occur mostly to the top of the scatter diagram (Figure 8). Rill (Rilcm) and gully
(Gulcm) erosion are shown to be of lesser significance in explaining the variation
in plant communities, although in some of the releves of plant communities 1.I,
1.3 and 2, gully andlor rill erosion was observed (Figure 8).
4.6 CONCLUSION
The descriptions and ecological interpretations of the plant communities
described contribute significantly to the studies previously undertaken in the
former western Transvaal grassland. Of special interest was the comparison of
the degraded communities described in this chapter with other previously
described communities in the area (Bredenkamp ef a/., 1988; Bezuidenhout &
Bredenkamp, 1991; Bredenkamp et a/., 1994; Bezuidenhout et a/., 1994 and
Cilliers & Bredenkamp, 1998). The vegetation was divided into woodland,
shrubland and grassland communities. Woodland communities were mostly
caffra, Acacia karroo and Acacia robusfa.
Shrubs such as Seriphium plumosurn, Mundulea sericea and Asparagus
composed of trees such as Acacia
suaveolens grew in abundance and indicated the state of degradation.
The plant communities in the degraded areas of Spitskop were associated with
big patches of bare ground characterized by different types of erosion which
possibly resulted from overgrazing and trampling by livestock. The presence of
exotic species also reflected the status of degradation in these communities.
Uncontrolled fires, gathering of firewood and accompanying disturbances such
as trampling and soil compaction are the most important threats to these
communities (Cilliers & Bredenkamp,
1998). The current demands on
woodlands, especially for fuel wood, exceed the supply to a significant degree
and the estimation is that parts of South Africa may be totally denuded of their
natural woodlands within the next 25 years (Hoffman et a]., 1999). Taking
vegetation degradation in its entirety, the degree, extent and rate of veld
deterioration in South Africa is markedly higher in communal districts (Hoffman ef
al., 1999). The proclamation of the HNP is therefore anticipated to contribute
towards the conservation of these plant communities in the grassland biome.
CHAPTER 5
SOIL EROSION IN THE SPITSKOP AREA, HNP
5.1 INTRODUCTION
Land degradation is considered to be a collective degradation of different
components of the land such as water, biotic and soil resources (Hennemann,
2001; Visser et a/., 2007). Soil erosion is one component of land degradation
and is defined as a naturally occurring process on land and may be a slow
process that continues relatively unnoticed, or it may occur at an alarming rate
causing a serious loss of topsoil (Wall et a/., 1987). From Chapter 4 it was clear
that different types of erosion could be observed around the Spitskop area of the
HNP. Factors controlling the rate and magnitude of soil erosion by water include
rainfall intensity, water runoff; soil erodibility, slope gradient, slope length, and
vegetation cover (Wall et a/., 1987). Loss of vegetation cover and change in
species composition are probably the first visible forms of degradation, although
it remains difficult to separate changes in veld condition due to environmental
factors (such as fluctuations in mean annual precipitation) from those changes
which are a result of mismanagement (Hoffman & Meadows, 2002). Despite this,
the conclusion of most historical reviews and official investigations in South
Africa in the past has been that it is people and their land use practices and not
climate that should be blamed for the current state of the environment (Hoffman
& Todd, 2000). For example, human alterations to the environment include
fragmentation which, among other things, increases habitat isolation and
changes the disturbance regime (ostman et a/.,2006).
In summary it can be said that a multitude of environmental and historical factors
simultaneously interact in causing land degradation (Ostman et a/., 2006). This
chapter focuses on soil erosion as one component of land degradation and the
aim is therefore to identify and classify the types of soil erosion occurring in the
Spitskop area. Other causes of soil erosion, such as overgrazing, trampling by
livestock, frequent fires and wood harvesting, are also briefly discussed in this
chapter.
5.2 RESULTS
In the Spitskop area, vegetation cover was strongly and negatively associated
with the degree of soil erosion. Sheet erosion was prominent in areas where
there was less vegetation cover and the extent of severity ranged from slight to
severe, affecting 57% of the total area sampled (Figure 9). The number of
indigenous species per releve was generally low in the degraded Spitskop areas
(Chapter 4) when compared to non degraded areas (Chapter 3). Table 6 in
Chapter 4 showed a summary of the Spitskop area classified according to the
soil degradation types and classes associated with the plant communities. Sheet
erosion was found to occur in most of the vegetation communities in the Spitskop
locality except in the Cymbopogon pospischilii - Elionurus muticus Grassland
(Chapter 4). The Cymbopogon pospischilii - Elionurus muficus community was
also not affected by rill and gully erosion, but showed a severe stage of
degradation indicated by large areas of bare, compacted soil. This severe stage
of degradation in the area is possibly due to overgrazing and trampling as
described by Bredenkarnp et a/. (1989) and constituted 14% of the area sampled
(Figure 9).
Rill erosion affected 15% of the total area sampled (Figure 9) and formed
integrated drainage networks leading to formation of gullies in most cases. The
Seriphiurn plumosum
- Acacia caffra Woodland and the Melinis repens - Acacia
robusfa Woodland were severely affected by rill erosion (Table 6). Gully erosion
was not so severe in all affected plant communities and covered 74% of the total
area sampled (Figure 9).
lGul(y SligM
0 Rill High
OR1 Sevwe
BSheal High
BSheet Moderate
Figure 9. A pie chart showing the dominance of erosion types and severity
classes in the Spitskop area in the Highveld National Park.
5.3 DISCUSSION
Sheet erosion leads to the formation of rill erosion and gully erosion (Figure 10)
on lower slopes due to the inability of the water to infiltrate the compacted soil
and therefore reaching the lower slopes with intense velocity (Valentin et a/.,
2005). Cattle tracks were also observed to cause the formation of waterways in
the form of rills or gullies where a concentration of water runoff can occur.
Manyatsi (1998) found that cattle grazing around active gullies can also increase
the dimension of gullies. The increase in the dimension of gullies results from the
falling in of the gully walls. Rill and sheet erosion have always been measured
together and the results could not be separated (Hoffman et a/., 1999). However,
Kakembo's (1997) sequential aerial photographic study of the Pedi district in the
Eastern Cape showed that the area of land affected by both rill and sheet erosion
had increased by some 12 -13% of the total area between 1938 and 1988.
Morgan (1995) quoted studies from Belgium in which rills accounted for 20 70% of soil movement on hillsides. The soil affected by sheet erosion in the
Spitskop area was prone to crusting and vegetation re-establishment in these
affected areas was almost impossible except in areas where there was brush
packing after wood harvesting or rare occurrences where seedlings were growing
in cattle dung.
(c)
Figure 10. Sheet (a
- b) and rill (c -
Highveld National Park.
(dl
d) erosion in the Spitskop area in the
Several studies on soil erosion revealed that, where gully systems form
integrated drainage networks with eroding or highly eroded channels, further
deterioration could occur due the absence of monitoring and rehabilitation
(Hanvey et a/., 1991; Brady, 1993). This was evident in the study by Brady
(1993) where the volume of gullies increased by 1348 m2 in the seven years
between 1984 and 1991 due to irresponsible land use. Gully formation processes
in South Africa do not vary significantly from those in other parts of the world
(Hoffman ef a/., 1999). Hanvey ef a/. (1991) and Brady (1993) all considered
sidewall erosion and collapse to be a major active gullying process.
Deepening of gullies is not mentioned anywhere in literature and some authors
are of the opinion that the gullies they studied are either stable in depth or filling
up due to sediment deposition. It is important to note that, in the long term, gully
erosion can be a cycling phenomenon, with identifiable periods of erosion and
infilling, although different areas may reach different stages at different times
(Hoffman et a/., 1999). Sediments are sometimes deposited within the rill or gully
and when those sediments are deposited for a variable period of time, they result
in infilling and establishment of vegetation (Figure 11). These small infilling
depressions also accumulate and hold water and provide a useful seedbed for
plants.
The destruction of the protective vegetation cover by overgrazing, wood
harvesting, fire and trampling (Figure 12) accelerates soit erosion and the
resultant impoverished hydrological status of the soil is the ultimate cause of soil
degradation (Tyson, 1986). The combination of factors such as overgrazing and
trampling indirectly enhance the aridity of the area because of the reduction in
vegetation cover (Beckerling, 1989). The study by Scott (1981) on veld and
pasture management in South Africa revealed that excessive soil loss is due to
burning practices whereby frequent fires strip canopy and basal vegetation cover,
leaving an unprotected soil surface prone to erosion.
Sherry (1959) also
observed massive soil losses due to burning of trash after wattle harvesting in
Kwazulu Natal. Brady (1993) considered vegetation burning and the
indiscriminate veld burning policy to be an influential factor in rapid gully
expansion. On the contrary, Watson's (1981) study in experimental catchments
at Cathedral Peak indicated no increases in sediment yield after burning.
Garland's (1987) experimental plots at Kamberg and the Drakensberg showed
that soil losses caused by burning alone were insignificant, although erosion from
footpaths in burned grassland was much greater than that from tracks in
unburned areas.
(a)
(b)
Figure 11. Gully formation (a) and infilling of a gully (b) in the Spitskop area
in the Highveld National Park.
Several studies also revealed that the frequency of fires might affect the direction
of change in woody plant density (Thomas & Pratt, 1967; Sabiiti & Wein, 1987;
Walters et a\., 2004). Some studies reported that a decrease in grass cover
favours the establishment of woody seedlings due to reduced competition
(Schultz et a]., I955; Kanz, 2001) whereas other researchers challenged these
findings (O'Connor, 1995; Brown & Archer, 1999). There have been limited
attempts in African savannas and grassland to quantitatively measure the
intensity of fires and to relate fire intensity to the response of herbaceous and
woody plants in terms of mortality and changes in physical structure (Trollope,
2001). Such research appears to be limited to studies conducted in the savanna
areas of South Africa (Trollope, 1993). The contradictory results from literature
concerning the effect of fire on vegetation and soil erosion necessitates further
research, as it seems that continuous use of incorrect burning practices may
have disastrous consequences on both vegetation composition and structure and
soil (Walters et a/.,2004).
Specific human activities such as deforestation have been empirically examined
and found to have an influence on biodiversity (Forester & Machlis, 1996). The
effect of wood harvesting on land degradation cannot be underestimated as the
removal of trees, shrubs and their litter exposes the surface soil to moving water
and encourages the concentration of flowing water (Showers, 1989). There has
also been a marked decline in the woodland resources, a decline that seems to
be accelerating (Du Toit et a/., 2003) with the majority of South Africa's rural
population remaining dependent upon fuel wood for their primary source of
domestic energy (Griffin et a/., 1993; Shackelton, 1994). Observations in the
Spitskop degraded areas showed significant changes in the height structure
class as compared to non degraded areas. Most woody plants in the Spitskop
area were new recruits possibly as a result of wood harvesting or fire. The
average heights of the tree and shrub strata in the Spitskop degraded areas were
found to be low (Table 7) compared to the non degraded areas (Table 4).
Shackelton et a/. (1994) studied the vegetation community structure and woody
plant species composition along a disturbance gradient in a communally
managed South African savanna. Their work showed that wood harvesting and
other impacts that are associated with communal area management have
caused a significant reduction in woody plant species richness with increasing
proximity to human settlements. Woody plant density is affected by management
practices, with some studies reporting a significant reduction in the number of
woody plant stems in a communally managed area as opposed to a conservation
area (Shackleton, 1993). The impact of natural resource harvesting on the woody
plant height structure class has also been studied, with some studies reporting a
significant difference between harvested and unharvested areas (Shackelton,
1993; Higgins et a/., 1999).
Figure 12. The destruction of protective vegetation cover by overgrazing
(a), fire impact (b) and wood harvesting (c) in the Highveld National Park.
The Acacia woodland communities form an important part of the vegetation in the
HNP, and these communities are adversely affected by unsustainable wood
collection (Daemane & Bezuidenhout, 2005). The current demands on
woodlands, especially for fuel wood, exceed the supply to a significant degree
and some estimates suggest that parts of South Africa may be totally denuded of
their natural woodlands within the next 25 years (Hoffman et a/., 1999). For
example, Williams et a/. (1996) suggested that woodlands in communal areas of
South Africa yield less than 5 million tonnes of harvestable fuel wood annually,
whereas the requirement under current population and levels of development is
for rather more than double this amount. Taking vegetation degradation in its
entirety, the degree, extent and rate of veld deterioration in South Africa is
markedly higher in communal districts (Meadows & Hoffman, 2002).
The rate of soil erosion is also highly dependent on land use, slope and climatic
factors (Garland, 1987). Observations in the HNP also reflected that the degree
of slope attributes to accelerated erosion in the area. Even though experimental
trials where not undertaken in this study to validate the effects of slope on
erosion, rill and gullies were found to occur on the lower slopes of the Spitskop
hill. Several studies on soil erosion all found rills and gullies rarely evident on
gradients greater than
lo0,
typically on unconsolidated colluvial or alluvial
materials (Snyman et a/., 1986; Liggit, 1988; Cobban & Weaver, 1993). The
influence of slope is strongly interrelated with factors such as soil type (Brady,
1993). The upper and mid-slopes of Spitskop were characterized by shallow
rocky soil and a low percentage of clay content with a good drainage system.
The lower slopes were composed of deeper soils that were less rocky and
relatively wetter with a high clay content and a poor drainage system, making
them susceptible to rill and gully erosion. This resulted in an accelerated velocity
of water runoff reaching the lower slopes with great force, causing the soil to be
washed away.
Rainfall also plays an important role in both soil erosion and forage availability
(Barker, 1985; Garland, 1987). Coetzee (2005) stated that runoff may occur for
two reasons. Firstly, if rain has a high intensity and falls too quickly for it to
infiltrate the soil (infiltration exceeds runoff), and secondly, if the soil has already
absorbed all the water it can hold. Rains with high intensity can therefore cause
significant soil damage, as the amount of water received by the soil can exceed
its absorption capacity (Liggit, 1988). Schulze (1997) and Hoffman's (I
999)
review of land degradation reflected the fact that topographic influence on rainfall
pattern in South Africa is evident. A review of some of the most recent
predictions suggested a 10-20% decrease in summer rainfall over the central
interior, as well as an increase in the frequency and intensity of floods and
drought (Joubert & Hewitson, 1997). It is also predicted that there will be a linear
increase in temperature with rising carbon dioxide levels, becoming 1.5 - 25°C
hotter than present by the year 2050, with an associated increased frequency of
higher temperature episodes (Joubert & Hewitson, 1997).
5.4 CONCLUSION
Degradation in the HNP was mainly evident in the form of soil erosion, habitat
destruction by overgrazing, frequent fires and wood harvesting. It can be
deducted from this study that soil erosion has an effect on species composition
as it stresses the plants by reducing the water retention and nutrient
accumulation of the soil. Soil erosion is also associated with human or natural
impacts that cause and maintain the erosion process such as grazing, trampling,
fire, etc. (Guerrero-Campo 8 Montserrat-Marti, 2000). Even though experimental
trials on overgrazing, fire effects and harvesting of wood were beyond the scope
of this study, their effects could not be overlooked. The intensity of the erosion
process was observed to depend on several factors such as slope, nature of
substrata, plant cover etc. (Morel, 1998). The intensity of soil erosion also
depends on several disturbance factors such as grazing, trampling, burning etc.
(Morel, 1998). The interaction of this complex group of factors and the long time
required for monitoring make studies of soil and vegetation dynamics very
difficult (Guerrero-Campo & Montserrat-Marti, 2000). In order to understand all
the factors contributing to degradation, the influence of humans on the land
should also never be under-estimated. It is widely accepted that human activities
are responsible for the vast majority of current habitat loss and that human
population density is correlated with habitat modification (Chown ef a/., 2003).
Understanding the relationship between human activity and biodiversity is
therefore critical for reducing the rate at which degradation occurs.
Several studies established a positive link between population growth and habitat
loss through deforestation (Rudel, 1989). Humans play an important role in
vegetation-climate feedback by igniting the majority of fires in the savanna
ecosystems (Hoffmann, 2002). However, it must be noted that climate largely
determines fire frequencies even where most fires are caused by people
(Barbosa et al, 1999) because fuel drying determines the success of both
intentional and accidental ignitions and the rate of fire spread (Chiney, 1981).
Livestock grazing in the HNP was observed to have an extensive impact on the
vegetation, especially around waterholes where habitat use is intensive. Freshly
burnt grasslands were found to be very attractive to herbivores, possibly because
of its increased protein concentration, thus resulting in concentrated grazing
pressure as soon as sufficient growth has occurred (Van Oudtshoorn, 1999). It is
expected that increases in grazing and trampling when plants are at an early
stage of growth will result in increased mortality of some plants.
Discussions of ecosystem impacts and conservation imptications of climate
change have not been included in the institutional frameworks of the
organizations responsible for the management of protected areas for a long time
(Thomas, 2006).
Protected areas offer limited resistance against problems
posed by rapid environmental change and those protected areas need to be
changed and adapted if they are to meet the challenges posed by global
warming (Markham et al., 1993; Scott, 2002; Van Jaarsveld et a/.,2003; Hannah
et a/., 2005). For instance, protected areas were proclaimed in the concept of
permanence, but under climate change, species for which a particular protected
area was established may no longer survive and protected areas could be faced
with the massive task of having to shift to keep up with moving habitats and
ecosystems (Markham et a/., 1993). More recently, shifting range boundaries as
a result of contemporary climate change has been observed for a multiple of
species, underscoring the potential for climate change effects on species
composition at fixed geographical points such as protected areas (Hannah et a/.,
2005). Increased drought and aridity could also lead to land degradation and
huge losses of biodiversity (Turpie et a/., 2002).
It is evident that climate change will introduce new challenges that will require a
different set of responses. These challenges impiy that some threats that have
been brought under control may re-emerge (i.e.,invasive species, erosion, bush
encroachment etc.) and in other cases completely new threats may be triggered
by changes in climate, suggesting a need for intensified management of present
threats (Hannah & Salm, 2003). Once fully effective management of present
threats is in place, or as climate-related impacts become apparent, strategies
specific to climate change may be put in place (Hannah & Salm, 2003). Clearly,
protected areas managers need to consider degradation and climate change in
their future plans and highlight these as imperative to management effectiveness.
In conclusion, soil should be considered the most fundamental natural resource
that sustains economic development and human well-being. This resource,
however, is experiencing degradation at an unprecedented rate (Hoffman &
Todd, 2000). Based on these predictions, it is evident that a subtle interaction
exists between climate patterns and land use, highlighting the necessity for
integrated studies looking at the impact of different land use practices under
currently changing climatic conditions. It is therefore highly recommended that
the future management of the HNP be aware of the threats of degradation to
biodiversity and aim to control it.
CHAPTER 6
MANAGEMENT UNITS IN THE HNP
6.1 INTRODUCTION
Ecological units such as association, population, community, or ecosystem, have
been defined and delineated in great multitudes and for many different purposes
(Jax ef at., 1998). For example, the concept of community is sometimes defined
simply as a recurring combination of species (e.g. for the purpose of classifying
vegetation), while in other cases the definition is based on interactions between
the component organisms (e.g. for the understanding and prediction of
succession). However, the different ways in which these units are defined and
used have a substantial influence on the way in which their identity through time
can be examined (Jax ef a/., 1998). If ecological vegetation units prove to be an
effective biodiversity management unit basis, the management efficiency could
potentially increase (Mac Nally, 2002). If all ecological vegetation units are
sufficiently well covered in a reserve or protected system, there would be high
confidence that biodiversity would be adequately represented (Pressey &
Nicholls, 1989; Margules & Pressey, 2000).
There has been growing interest in ecosystem-based management within
protected areas as a result of the recognition that protected areas are subjected
to many internal and external threats (Slocombe, 1993). This Interest in
ecosystem management has focused on internal ecosystem management in
order to maintain integrity and ecosystem health. On broader approaches,
ecosystem management seeks to recognize the need to manage an entire
ecologically coherent region that usually extends well beyond the protected area
boundaries to include the whole ecosystem (Slocombe, I993). However, this is
not the case in the HNP as there is urban development very close to one
boundary of the park. Urban areas represent a threat to a potential National Park
on a number of levels including noise pollution, visual pollution, loss of
wilderness ambiences, squatting and use of natural resources. The park will
therefore need to develop a Conservation Development Framework (Spies,
2004) in order to provide an overarching spatial planning framework. This
planning framework should have use zones, with management guidelines and
broad conservation and tourism infrastructural requirements designated for each
zone (Spies, 2004). The management units in the
HNP will provide valuable
information when drafting the Conservation Development Framework. The
framework should also address issues such as urban development close to the
park and future expansion of the park. Ascertaining whether an ecosystem, a
community or any other ecological unit has completely changed, been destroyed
or whether it remains the same is an important task that seeks the undertaking of
ecological studies (Jax et a/., 1988). From an ecological perspective, it is
essential to make a clear distinction between different plant communities
occurring within a given area because of the ecological characteristics separating
them from each other. It is therefore crucial to group these plant communities
together in broad management units, which can be incorporated into a
management plan (Van Wyk & Bredenkamp, 1986; Brown, 1997). Some of the
criteria used to determine management units are plant communities, land types,
broad soil patterns, geology, topography and land use (Brown, 1997).
The aim of this chapter is therefore to identify and describe the management
units of the
HNP. The compilation of management units is based on ecological
principles whereby differences in several attributes such as vegetation, habitat,
topography and soil characteristics are used. The suggested ecological
management units for the
HNP are not seen as units standing on their own, but
rather as areas which show similarities towards vegetation, habitat, topography,
soil characteristics etc. These ecological management units are therefore not
confined to one area alone, but exist in different areas of the park which have the
above-mentioned similarities and could therefore be similarly managed. A total
of six different management units were identified and are indicated on two
separate management unit maps of the park (Figures 13 and 14).
6.2. DESCRIPTION OF MANAGEMENT UNITS
6.2.1 Management Unit 1
Management unit I (Figure 13) consisted mainly of areas associated with the
midslopes and valley bottomlands of the dolomitic and rocky chert outcrops.
Sinkholes were characteristically present in this unit which was underlain by
dolomite. The soils of this unit were relatively shallow, well drained and with a
relatively low clay content, except the sinkholes which were filled with deep
sandy soil. The following plant communities occurred in management unit I of
the HNP:
Loudefia simplex
-
Vangueria infausfa subsp, infausta Shrubland (Plant
community 2 in the HNP)
Schizachyrium sanguineum - Cymbopogon excavafus Grassland (Plant
community 4 in the HNP)
Rhus pyroides - Acacia erioloba Woodland (Plant community 5 in the HNP)
The tree species dominating this management unit included Acacia erioloba,
Celfis africana and Acacia caffra. The dominant shrub species included Rhus
pyroides, Diospyros lycioides, Ehretia rigida and Vangueria infausta subsp.
infausta. The prominent grass species included Schizachyrium sanguineum,
Cymbopogon
excavafus,
Loudefia
simplex,
Trachypogon
spicatus,
Diheferopogon amplecfus and Melinis nen~iglumis.Exotic plants found in this
management unit included Tagetes minufa, Verbena officinalis, Conyza
bonariensis, Achyranthes aspera, Nicotiana longiflora, Bidens bipinnata and
Solanum nigrum. The floristic and habitat diversity of this management unit,
especially the Rhus pyroides - Acacia erioloba community had a high
conservation status and was similar to the Vaal Reefs Dolomite Sinkhole
Woodland (Gh 12) described by Mucina & Rutherford (2006). The conservation
status of the Vaal Reefs Dolomite Sinkhole Woodland is vulnerable and has a
conservation target of 24%.
Figure 13. Ecological management units of the Highveld National Park.
6.2.2 Management Unit 2
Management unit 2 (Figure 13) was associated with the stony plains and
midslopes of the rocky quartzite outcrops and hills. 'The soil in this unit was
relatively shallow, well drained and characterized by a relatively low clay content.
The following plant communities occurred in management unit 2 of the HNP:
Mystroxylon aethiopicum - Pavetta zeyheri Shrubland (Plant community 1 in the
HNP)
Diheteropogon amplectus - Trachypogon spicatus Grassland (Plant community 3
in the HNP)
Setaria sphacelata var. sphacelata - Acacia caffra Woodland (Plant community 6
in the HNP)
Dominant trees found in this management unit included species such as Acacia
caffra, Acacia karroo, Olea europaea subsp. africana and Pappea capensis.
Dominant shrubs were represented by species such as Pavetta zeyheri,
Mystroxylon aethiopicum, Grewia occidentalis, Tapiphyllum parvifolium, Rhus
pyroides, Ehretia rigida and Protasparagus suoveolens. Dominant grasses
included species such as Panicum maximum, Melinis nerviglumis, Themeda
triandra, Elionurus muticus, Diheteropogon amplectens, Trachypogon spicatus,
and Cymbopogon excavatus. Forbs such as Helichrysum rotundaturn, Senecio
venosus, Vernonia oligocephala, Dicoma anomala and Aloe greatheadii var.
davyana were also associated with the rocky habitat of this management unit.
This management unit had a high number of exotic species (18). These included
species such as Tagetes minuta, Verbena officinalis, Paspalum dilatatum,
Conyza bonariensis, Achyranthes aspera, Bidens bipinnata, Gomphrena
celosioides, Schkuhria pinnata, Verbena bonariensis, Gulleminea densa,
Plantago lanceolata, Solanum sisymbriifolium, Chenopodium album, Opuntia
ficus-indica, Oxalis corniculata, Zinnia peruviana, Oenothera tetraptera and
Cirsium vulgare.
6.2.3 Management Unit 3
Management unit 3 (Figure 13) was found on the footslopes, bottomlands and
n-lidslopes of the rocky quartzite hills. The unit was characterized by generally
medium to deep soil with a relatively high clay content and a poor drainage
regime. The following plant communities occurred in management unit 3 of the
HNP:
Ziziphus zeyheriana -Acacia karroo Woodland (Plant comm~~nity
7 in the HNP)
Cymbopogon pospischilii - Themeda triandra Grassland (Plant community 8 in
the HNP)
Dominant trees found in this management unit included species such as Acacia
karroo and Acacia caffra. Acacia karroo encroaches into the floodplains as a
result of overgrazing or other forms of disturbance of the vegetation. Shrubs such
as Rhus pyroides, Ehretia rigida, Ziziphus zeyheriana, Asparagus suaveolens,
Maytenus heterophylla and Asparagus laricinus were evenly distributed. Clematis
brachiata was also associated with this unit as a climber amongst the trees and
shrubs. Grasses associated with this unit included Cymbopogon pospischilii,
Themeda triandra, Elionurus muticus, Setaria sphacelata var. sphacelata, and
Eragrostis cuwula. Forbs such as Verbena officinalis, Teucrium trifidum,
Delosperma herbeum, Aloe greatheadii var. davyana, Sida spinosa and Pavonia
burchellii were prominent in this community. This unit was characterized by
pioneer species such as Conyza podocephala, Teucrium trifidium and Berkheya
radula. This management unit had the highest number of exotic species (19).
These included species such as Tagetes minuta, Verbena officinalis, Conyza
bonariensis, Achyranthes aspera, Avena fatua, Bidens bipinnata, Gomphrena
celosioides, Physalis angulata, Oenothera rosea, Oenothera tetraptera, Cirsium
vulgare, Lepidium bonariensis, Schkuhria pinnata, Solanum sisymbriifolium,
Opuntia ficus - indica, Oxalis corniculata and Zinnia peruviana.
6.2.4 Management Unit 4
Management unit 4 (Figure 13) occurred 011the valley floors and in most wetland
areas present at local depressions. The following plant community occurred in
this management unit:
Eragrostis plana - Hyparrhenia hirta Grassland (Plant community 9 in the HNP)
This management unit was generally fairly unstable, possibly due to seasonal
flooding and subsequent desiccation which, together with overgrazing, accelerate
an advanced state of degradation such as compacted, bare soil and loss of
vegetation cover. The soil surfaces closer to the artificial watering points
exhibited large bare patches with compacted soil. These areas were an
indication of overgrazing and trarr~pliqgby livestock in ,the past and had a lower
vegetation cover.
Trees were absent in this management unit and a few shrubs such as Asparagus
suaveolens and Asparagus laricinus were very pronounced and seemed to
increase with degradation. Prominent grass species in this unit were Eragrostis
plana, Hyparrhenia hirta, Cymbopogon pospischilii, Elionurus muticus, Eragrostis
chloromelas and Setaria sphacelata var. sphacelata. 'This unit was characterized
by pioneer species such as Verbena officinalis, Conyza podocephala and
Berkeya radula. Exotic plants found in this management unit included species
such as
Verbena officinalis, Paspalum dilatatum, Conyza bonariensis,
Ciclospermum leptophyllum, Persicaria lapathifolia, Oenothera rosea and
Oenothera tetraptera.
6.2.5 Management Unit 5
Spitskop
Management unit 5 (Figure 14) was associated with the valley bottomlands,
footslopes, midslopes and crest of the quartzite Spitskop hill. Two plant
communities, Loudetia simplex - Vangueria infausta subsp. infausta Shrubland
and Diheteropogon amplectens - Trachypogon spicatus Grassland were included
in management unit 2, but excluding the Spitskop area (Figure 9). These two
plant commur~itiesalso occurred in the Spitskop area and shared a similar
habitat with the degraded plant communities found in this area. All plant
communities occurring in the Spitskop areas were therefore grouped under
management unit 5, consisting of four sub-units.
Management Unit 5: Sub-unit 1
Sub-unit 1 (Figure 14) occurred on the crest and midslopes of the rocky quartzite
Spitskop hill and was characterized by shallow soil not affected by erosion. The
following plant communities occurred in this sub-unit:
Loudetia simplex - Vangueria infausta subsp. infausta Shrubland (Plant
community 2 in the HNP)
Diheteropogon amplectens - Trachypogon spicatus Grassland (Plant commur~ity
3 in the HNP).
Dominant species found in this community included grasses such as Loudetia
simplex, Diheteropogon amplectens and Trachypogon spicatus. These species
were typically characteristic for the relatively dry habitat and shallow rocky soils.
Shrubs in this sub-unit included species such as Vangueria infausta subsp.
infausta, Mundulea sericea and Zanthoxylum capense. Acacia caffra represented
the tree stratum in this management sub-unit. Exotic plants found in this sub-unit
included species such as
Tagetes mtnuta, Verbena officinalis, Conyza
bonariensis, Achyranthes aspera and Nicotiana longiflora.
Sub-Unit 1
26'43'305
Sub-Unit 3
o
P
0.06 0.1
o2
03K~~-,...
I
Sub-Un~t4
Figure 14. Four sub-units found in management unit 5 of the Spitskop area
in the Highveld National Park.
Management Unit 5: Sub-unit 2
Sub-unit (Figure 14) occurred on the rocky quartzite midslopes of the Spitskop
hill and was generally characterized by pronounced sheet, rill and gully erosion.
Wood harvestirlg was also evident in this subunit. The following plant
communites were found in this si-~b-unit:
Setaria sphacelata var. sphacelata - Acacia caffra Woodland (Plant Community 6
in the HNP).
Seriphium plumosum- Acacia caffra Woodland (Plant Community 1 in the
Spitskop area).
Acacia caffra was the dominant tree in this sub-unit and the abundance of
Seriphium plumosum was a clear indication of degradation in this sub-unit.
Setaria sphacelata var. sphacelata, Eragrostis racemosa, Aristida bipartita,
Eragrostis rigidior are the dominant grasses in this sub-unit. Shrubs present
included species such as Ziziphus zeyheriana, Rhus pyroides and Euclea
undulata. This sub-unit had a high number of exotic species (18). These included
plants such as Verbena oficinalis, Paspalum dilatatum, Conyza bonariensis,
Achyranthes aspera, Bidens bipinnata, Schkuhria pinnata, Verbena bonariensis,
Gulleminea densa, Plantago lanceolata, Solanum sisymbrifolium, Chenopodium
album, Oxalis corniculata, Zinnia peruviana, Oenothera tetraptera, Cirsium
vulgare, Gomphrena celosioides, Solanum elaeagnifolium and Opuntia ficusindica.
Management Unit 5: Sub-unit 3
Sub-unit 3 (Figure 14) occurred on the footslopes of the quartzite Spitskop hill
and was affected by sheet, rill and gully erosion. This sub-unit was encroached
by Acacia karroo due to changes in the grazing andlor fire regime in the
management of this grassland. The following plant community was found in this
sub-unit:
Setaria sphacelata var. torta - Eragrostis curvula Grassland (Plant community 2
of the Spitskop area).
Dominant grasses in this sub-unit included species such as Setaria sphacelata
var. torta, Eragrostis curvula and Digitaria eriantha. Shrubs included species
such as Grewia flava and Asparagus laricinus. Species such as Aloe greatheadii
var. davyana were abundant in this sub-unit and their cover seemed to increase
under severe conditions of degradation. Exotic plants found in this sub-unit
included species such as Gomphrena celosioides, Plantago lanceolata, Oxalis
comiculata and Solanum elaeagnifolium.
Management Unit 5: Sub-unit 4
Sub-unit 4 (Figure 14) occurred on the valley bottomlands and floodplains and
was characterized by bare patches of compacted soil resulting from overgrazing
and trampling. The following plant comm~~nity
was found in this sub-unit:
Cymbopogon pospischilii - Elionurus muticus Grassland (Plant community 3 in
the Spitskop area).
Dominant grass species found in this sub-unit included species such as
Cymbopogon pospischilii, Elionurus muticus, Eustachys paspaloides and Aristida
congesta subsp. congesta. Other dominant species included the dwarf shrub
Sida alba, the forb Vernonia oligocephala, the tree Acacia karroo and exotic
species such as Gomphrena celosioides and Oxalis corniculata.
6.2.6 Management Unit 6
DUMPING SITE
The existence of an official dumping site of the Potchefstroom Municipality
(Figure 13) within the protected area is one unique scenario that should be taken
into consideration in the HNP. The management of this area is exclusively
undertaken by a contracted private company (Millenium Utility Company). It must
be ensured that the highest standards are maintained to comply with the second
addition of the Minimum Requirements for Waste Disposal by Landfill (released
by the Department of Water Affairs and Forestry during 1998).
Proper management control in the dumping site is crucial and presently includes
the following (Millenium Utility Company, 2003):
Gate control
Record keeping (different waste stream)
Ensuring maximum compaction (air space control)
Daily cover
Methane monitoring
Nuisance control (flies, odours etc.)
Small quantities of hazardous waste are allowed from the residents of the
communities that the site serves and a container built for this purpose was
supplied for these wastes to be disposed. The container is emptied on a regular
basis at a permitted Landfill Facility (Millennium Utility Company, 2003). The
proper management of any land,fill cannot be overemphasized since this solely
determines the long-term success of a landfill (Millennium Utility Company,
2003).
6.3 CONCLUSION
The description of the plant communities together with the vegetation map
assisted in the formulation of management units for the HNP. The formulation of
management units based on ecological principles serves as the basic foundation
forming an integral part of future strategic management plans. The manqgement
units make it possible to manage the different sections of the park in collected
and identical units and not as broken and unmanageable areas.
Management unit 1 was associated with the Rhus pyroides - Acacia erioloba
community occurring in the dolomitic and rocky chert outcrops, and had a high
conservation status. The Rhus pyroides - Acacia erioloba community was similar
to the Vaal Reefs Dolomite Sinkhole Woodland (Gh 12) described by Mucina &
Rutherford (2006). The conservation status of the Vaal Reefs Dolomite Sinkhole
Woodland is vulnerable and has a conservation target of 24%. A study on the
historical background of ,the area may provide some answers concerning the
current state of degradation in certain areas of the park such as Spitskop. The
cause of degradation differs and includes factors such as wood harvesting,
overgrazing by livestock, soil erosion and frequent fires. Subunit 4 in
management unit 5 was characterized by areas of bare compacted soils
indicating overgrazing and trampling by livestock in the past and had less
vegetation cover. Of special interest were the exotic plant species found in these
management units and their association with degradation. Subunit 3 in
management unit 5 in the Spitskop area was adversely affected by sheet, rill and
gully erosion. Wood harvesting was also evident in this management unit. This
observation re-emphasizes the necessity for an alien eradication and
rehabilitation program in the park. Special attention must be given to
management units 2, 3 and 5 as they had a high number of exotic plant species.
Future park management should also ensure that biodiversity objectives are not
compromised by the existence of waste disposal sites within the HNP.
Management recommendations are provided in Chapter 7.
CHAPTER 7
MANAGEMENT RECOMMENDA'TIONS FOR 'THE HNP
7.1 INTRODUC'TION
The focus of degradation in this study was mainly limited to the Spitskop area
due to the pronounced impact on the surrounding area. It was observed that the
main cause of degradation in this area was soil erosion by water run-off from the
steep slopes of Spitskop. Other factors such as overgrazing, fire and trampling
by livestock contributed to the reduction of resource potential on land. Different
types of erosion were identified and some of the factors influencing erosion were
discussed in Chapter 5. Alien species also deteriorated the physical, chemical,
biological and economic properties of soil. They also had an effect on the
hydrological status and compete with the indigenous flora over the long-term.
Alien species occurring in the HNP were mentioned in Chapters 3, 4 and 6, and
the management of these species will be briefly discussed in this chapter. A
rehabilitation plan will be required in order to attain the recovery of ecosystem
processes, productivity and services.
Definitions of rehabilitation and restoration in this thesis follow that of Coetzee
(2005). According to Coetzee (2005) rehabilitation emphasize the recovery of
ecosystem process, productivity and services. It returns some of the functions of
the original pre-disturbance ecosystem and the historical or pre-existing
ecosystem. Restoration shares with rehabilitation the reparation of ecosystem
processes to as close to the original structure and function as possible, but
differs in that it also includes the re-establishment of the pre-existing biotic
species composition and community structure (Coetzee, 2005). Restoration
generally requires more post-rehabilitation after-care and it takes much longer to
achieve the desired result (Coetzee, 2005).
The aim of this chapter is therefore to recommend a rehabilitation plan that seeks
to achieve the following:
reduction of the speed of water run-off in order to reduce the erosive
force of water on unprotected soil surfaces,
retaining of soil, plant debris, and seed that may be carried away by
water run-off,
improving the vegetation cover of the degraded areas,
upholding and increasing the biodiversity of the land, and
eradication of all alien species found in the park
7.2 SOIL EROSION CONTROL MEASURES
The proposed strategies for soil conservation are based on covering the soil for
protection from raindrop impact; increasing the infiltration capacity of the soil to
reduce impact; increasing the infiltration capacity of the soil to reduce runoff;
improving the aggregate stability of the soil; and increasing surface roughness to
reduce the velocity of runoff (Wall et all 1987). The reduction of water runoff
velocity could increase the chance of vegetation re-establishment and thus
minimize the erosion problem. Control measures regarding sheet, rill and gully
erosion must also aim at slowing concentrated runoff water flow to reduce its
velocity and also to capture sediments (Valentin et al., 2005). The soil on sheet
erosion patches and other meagerly vegetated areas develop a hard surface
crust due to long exposure to sun, wind and raindrop impact (Figure 15),
inhibiting penetration of water into the soil. An appropriate organic substrate is
required to facilitate seed germination in hard surfaces such as in areas impacted
by sheet erosion. For example, small seedlings of Chenopodium album were
found growing on cattle dung in some of ,the areas affected by sheet erosio~i
(Figure 16). Other methods such as mechanical soil cultivation were found to be
effective in combating sheet erosion (Van der Merwe & Kellner, 1999). Subsoil
cultivation with a ripper is recommended in areas affected by sheet erosion and
the rip furrows must be at least 200 mm deep to ensure the best effect (Van der
Merwe & Kellner, 1999).
Mechanical soil cultivation facilitates better water
infiltration into the soil and also creates a favourable micro-habitat for the optimal
propagation of seedlings (Wight & White, 1974; Van der Mewe & Kellner, 1999).
Figure 15. Exposed soil with eroded stones and rock particles in the
Spitskop area in the Highveld National Park.
Figure 16. Cattle dung providing a good growth medium in an area affected
by sheet erosion in the Spitskop area in the Highveld National Park.
Two methods, namely stone packing and brush packing worked effectively in
areas that were previously affected by erosion in the HNP. Stone packing diverts
and reduces the speed and force of runoff water and traps water-carried soil
particles and organic matter (Figure 17). Stone packing also traps valuable plant
litter and keeps it in place over the soil, protecting and enriching the soil and the
important detritivores that live in it (Coetzee, 2005). Rows of stones can be
stacked along the contours to obstruct the runoff of water, thereby improving the
moisture status of the soil. Plants, especially grasses, can be established above
the rows of stones (Van Oudtshoorn, 1999).
Brush packing is also an effective and renewable resource if sensitively
harvested. Branches of trees can be packed over the bare patches (Figure 18a).
Brush packing, even at a very low scale (Figure 18 b-c), plays an important part
in capturing sediments. A very small amount of sediments can capture seeds and
ultimately result in the establishment of vegetation. Brush packing is effective in
protecting bare patches against the wind, sun and also probably new seedlings
against early grazing and other natural factors (Van Oudtshoorn, 1999). Brushpacking also provides cover for a large number of animals including reptiles,
rodents, hares, small carnivores and hosts of invertebrates (Coetzee, 2005).
These animals also leave their droppings and remnants of their meals, which
decompose and help to build up the organic components of the topsoil. Many of
these animals also burrow into the soil, which assists with infiltration of water
(Coetzee, 2005).
According to Coetzee (2005), the most effective method to reclaim gully erosion
is to stack stones in gabions (wire baskets) so as to catch sediments but allow
the water to pass through with a reduced velocity. Gabion constructions should
immediately be followed by seeding or planting for the establishment of
vegetation cover. Branches can also be piled in gullies to capture sediments
(Van Oudtshoorn, 1999). Research has shown that an increase in root density of
grass and other plants results in an exponential decrease of concentrated flow
erosion rates (Gyssels & Poesen, 2003). Care must be taken to ensure that the
removal of stones does not become the cause of a new erosion problem at the
source of the material (Coetzee, 2005). It is crucial to treat gullies in the early
stages of formation rather than to try to repair the damage once a deep gully has
formed (Coetzee, 2005). Small rills that are starting to open can be easily
controlled by filling them with brush or stones.
Figure 17. The soil erosion control measure using stone packing in the
Spitskop area in the Highveld National Park.
The recovery progress of the rehabilitated areas needs to be monitored at
regular intervals to evaluate the effectiveness of the methods employed (Table
9). A class score (1
- 4) is given for each level of erosion (soil movement,
surface litter, flow pattern, sheet erosion, flow patterns, rills, gullies) at four
different erosion severity classes (Table 9). For example, erosion severity class 1
has a total score of 6 points (Ix 6), class 2 has a total score of 12 points (2 x 6 )
etc. The presence of soil movement, surface litter and flow patterns indicate the
availability of transport of resources from upslope sources in the landscape and
imply some soil instability (Coetzee, 2005; Savory, 1990) . Little evidence of flow
patterns indicates slight erosion whereas numerous flow patterns indicate severe
erosion. A score of 6 points or less in Class 1 indicates conditions of stable soil
surface whereas a score of 24 points in Class 4 will be an indication of severe
soil erosion (Table 9). These guidelines can be used together with Table 2
whereby the severity of different types of soil erosion can be measured and
monitored over time. The rehabilitation of degraded areas in Spitskop can be
monitored by observing the condition of soil movement, surface litter, Row
patterns and also measuring the severity of sheet, rill and gully erosion in all
affected plant communities in each management unit.
This guide should be used together with vegetation monitoring methods,
including the fixed-point photographic method (Coetzee, 2005). Vegetation
monitoring in rehabilitated areas will provide information about the subtle
changes in species composition. Photographs at fixed points and directions
should be taken when undertaking the floristic composition survey, enabling the
comparison of different sets of photographs taken at different dates. The
individual photographs must be numbered reflecting the date that the
photographs were taken. By applying this guideline as a monitoring tool, the
distinction will be made between areas where erosion is likely to occur and areas
where erosion is becoming severe. The monitoring interval should be three to six
months but this will depend on rainfall and the rate of vegetation recovery in the
area.
1
Table 9. Approaches in monitoring degradation status in the Highveld National Park (Adapted & modified from
I
Savory, 1990).
I
Class
1
2
3
Soil movement
Little evidence of movement of soil
Moderate movement is visible and
Soil
particles.
recent
deposited against obstacles.
the area.
4
movement with
each
event
Sub-soil exposed over much of
Slight terracing evident.
Surface litter
Flow patterns
Litter accumulating and incorporated
Little movement by wind and water
Extreme movement, large deposits
Litter removed by animals, wind
into soil. Rapid breakdown
evident. Slow breakdown.
against obstacles
and water.
Little evidence of particle movement
Well-defined, small & intermittent.
Flow patterns evident with deposition
Patterns
numerous
of soil & litter
noticeable.
Large
and
barren fan
deposits
No evidence of sheet erosion.
Sheet
Low percentage of small scattered
High percentage of small scattered
Exposed
sub-soil
surface
developing into hard crust with
enuding
along 25 - 50% of their length.
becoming established.
scores
D
action rsquired.
erosio~
n.
Cons
intervebntion
anageme
ion contr01 programme
large areas. Wider
ullies actively eroding over 50%
mion corrtrol required.
7.3 ERADICATION OF ALIEN VEGETATION
The percentage of alien vegetation found in the degraded areas and the park as
a whole is very low in comparison to that of the natural vegetation (Table 3 & 5).
The following alien species were identified in different plant communities in the
HNP (Chapter 3 & 4):
A chyranfhes aspera, Bidens bipinnata, Cirsium vulgare, Conyza bonariensis,
Gornphrena celosiodes, Lepidium bonariensis, Nicotiana longiflom, Oenofhera
rosea, Oenofhera fetrapfera, Opunfia ficus-indica, Oxalis corniculata, Physalis
angulafa, Planfago lanceolata, Solanum elaeagnifolium, Solanum nigrum,
Solanum sisymbrifolium,
Zinnia peruviana. Additional
species
such as
Eucalypfus carnaldulensis were also identified in the HNP.
The Conservation of Agricultural Resources Act (CARA, Act No 43 of 1983,
amended, 2001) previously classified problem plants in two groups - declared
weeds and plant invaders (Henderson, 2001). The amended regulation makes
provision for four groups - declared weeds (Category 1 plants), plant invaders
(Category 2 & Category 3 plants) and indicators of bush encroachment. The
following species in the list above fall under Category Iweeds:
Achyranthes
aspera,
Cirsium
vulgare,
Opuntia
ficus-indica,
Solanum
elaeagnifolium and Solanum sisymbrifolium.
These are prohibited plants that should not be tolerated as they are able to
invade undisturbed environments and transform or degrade natural plant
communities. They also use more water than the plant communities they replace
or can be particularly difficult to control (Henderson, 2001). Most of the plants in
this category produce copious numbers of seeds, are wind or bird dispersed or
have highly efficient means of vegetation reproduction.
Eucalyptus camaldulensis falls under Category 2 plants. This plant has proven
potential of becoming invasive, but nevertheless has certain beneficial properties
that warrant its continued presence in certain circumstances (Henderson, 2001).
CARA makes provision for Category 2 plants to be retained in special areas
demarcated for that purpose, but those occurring outside demarcated areas have
to be controlled. The exception is that Category 2 plants may also be retained or
cultivated in biological control reserves, where the plants will serve as host plants
for the breeding of biological control agents (Henderson, 2001).
The presence of these alien invasive plants may jeopardize the existence of
other species by adversely affecting preferred habitats (USDA, 1999). Areas
invaded by these alien plants need to be classified according to the degree of
infestation. Although each species acts differently in the environment and in its
interaction with other species, eradication of all alien vegetation within the
boundaries of the HNP and surrounding areas should be considered a high
priority.
Monitoring of these species should aim at the long-term reduction in density and
abundance of an invasive species to below a pre-set acceptable threshold. The
damage caused by the species below this threshold is considered acceptable
with regard to damage to biodiversity (Foxcroft, 2003a). In order to evaluate the
success or failure of management efforts, the populations of invasive species,
the condition of the area under control and the changes in species composition
and dominance should be monitored. Targets for success may be the removal of
the invasive species if the option chosen is eradication, but if it is control, then
the criteria for success may be a measure of some other feature such as the
return of a plant. Plant control may involve manual methods (e.g. hand pulling,
cutting, mowing, etc.); herbicides or chemical methods, the release of biological
control agents, controlled use of browsing or grazing animals; prescribed fires;
and other land management practices (Foxcroft, 2003b).The use of chemical
control might have an adverse impact on the surrounding ecosystem and careful
consideration must be taken before application. However, it must be noted that
the complete eradication of alien plants is unrealistic (Coetzee, 2005) and it is
therefore crucial to rather prevent the further spread of alien plants into
uninfected areas and isolate the dense infestations within a landscape that is
maintained free of alien plants.
7.4 BURNING REGIME
Fire managers seeking to maintain b~odiversitymay have multiple objectives to
meet even in conservation areas (Gill, 2001). The protection of human life and
property is often paramount; aesthetics, cultural protection and smoke
management may also be of concern (Gill, 2001). Application of any fire policy
creates fire regimes that have implications for biodiversity and socio-economic
conditions (Gill, 2001). The basic role of protected areas was to separate
elements of biodiversity from processes that threaten their existence by
establishing them in remote areas (Margules & Pressey, 2000). A more
systematic approach to locating and designing protected areas has been
evolving and this approach will need to be implemented if a large proportion of
today's biodiversity is to exist in a future of increasing numbers of people and
their demands on natural resources (Margules & Pressey, 2000).
The challenge in the HNP is the presence of recent urban developments very
close to the N12 boundary. The HNP management will need an ecologically
sound and socially responsible fire regime policy and a monitoring and evaluation
system in order to reach amicable solutions with the community. The objectives
need to reconcile considerations of biodiversity conservation with fire security. It
is proposed that neighbouring communities should be approached with a view to
forming a Fire Protection Association in terms of Act 101 of 1998. Firebreaks
should be applied on the boundary between the park and any adjoining lands
and also in the park around fixed property, infrastructure improvements, movable
property, fauna and flora to limit and reduce the damage and tosses caused by
fires to life.
Fire is ecologically used to remove moribund and or unacceptable accumulated
grass material in order to maintain the natural habitat of the area (Trollope &
Potgieter, 1986; Trollope & Trollope, 2004). It is also used to create or maintain
an optimum relationship between herbaceous and woody vegetation where
necessary, and to encourage wildlife to move to less preferred areas in order to
minimize the overuse of preferred areas (Trollope & Trollope, 2004). A variety of
fire regimes incorporating different frequencies, intensities, seasons and types of
fire were described by Trollope & Trollope (2004) and can be applied in the HNP.
The total area to be burnt can be determined as a function of the estimated
standing grass fuel load at the end of the growing season. This is determined by
using a disc pasture meter (Bransby & Tainton, 1977; Trollope & Potgieter,
1986). The prescribed burns are applied when the grass sward is dormant to
avoid any detrimental effects on the re-growth and basal cover (Trollope &
Trollope, 2004).
The frequency of burning varies as a function of the stocking rate of grazing
animals and the amount of rainfall the park receives. When burning to remove
moribund material, the frequency of burning depends on the rate at which the
grass sward becomes moribund, i.e. accumulated grass fuel load greater than
4000 kglha (Trollope & Trollope, 2004). An increased burning frequency results
in an increased number of pioneer grass species due to nutritional attractiveness
of the burned areas and therefore heavy grazing by herbivores (Trollope and
Potgieter, 1985). Fire intensity varies according to the reason for burning
(Trollope & Trollope, 2004). When burning to remove moribund material, a cool
fire of < 1000 kJ/s/m is recommended. This is achieved by burning when the air
temperature is ~ 2 0 ° C
and the relative humidity >50 %. When burning to maintain
the balance between herbaceous and woody vegetation, an intense fire of >ZOO0
kJ/s/m is required (Trollope & Trollope, 2004). This is achieved when the grass
fuel load is >4000 kglha, air temperature is >25"C and the relative humidity is
~ 3 %.
0 This results in significant top-kill of stems and branches of trees and
shrubs up to a height of 3 m, making the vegetation more available for shorter
browsing animal species (Trollope & Trollope, 2004).
Limits are set to the area burnt to help ensure adequate supplies of forage for
herbivorous wildlife. It is recommended that no more than 50% of the area be
burnt in the grassland ecosystems (>700 mm rainfall per year). The application of
patch burns during the burning season has the effect of attracting grazing
animals to a different, newly burnt area after each fire (Brockett eta/., 2001). This
minimizes the possible deleterious impact of heavy, continuous grazing in any
one area after burning (Brockett et a/., 2001)
7.5 CONCLUSION
Over the past two decades, the science of ecology has undergone many
significant shifts in eniphasis and perspectives, which have important
implications for how we manage ecosystems and species (Wallington et a/.,
2005). Degradation (both natural and human induced), climate change and the
heterogeneous nature of vegetation communities are concepts that dominate
current ecological thinking (Wallington et a/, 2005). Worldwide, loss of habitat is
regarded as the foremost cause of loss of biodiversity, and South Africa is no
exception (Mucina & Rutherford, 2006). Management of protected areas needs
s only on species and ti-~reatsbut also on land degradation in general
to f o c ~ ~not
(RutherFord et a/., 1999a; RutherFord et a/., 1999b; Lovejoy, 2006).
Protected areas are the most important and effective components of current
conservation strategies, and they are the central elements of climate change
(Bruner et a/., 2001). This means that protected areas may not provide adequate
future safeguards for the continued survival of existing ecosystems and species
in a changing world (Bruner et a/., 2001). As climate changes, the role of
protected areas will certainly expand with associated shifts in species ranges and
new management strategies will be required (Hannah & Salm, 2003). Priority
needs to be given to threats that are most likely to be affected by, or interact with,
variation in climate (Hannah & Salm, 2003). Examples are fire management,
,flood regimes and invasive species. For example, combating erosion at much
earlier stages or eliminating an invasive species may be possible at a much
lower level of management resources prior to climate change, and be more
expensive or impossible once climate change is evident (Hannah & Salm, 2003).
Such steps to control current threats, while not tailored specifically for climate
change, are good initial investments in climate change management (Hannah &
Salm, 2003; IUCN, 1993; IPCC, 2002).
CHAPTER 8
CONCLLIDING REMARKS
The proposal to establish the HNP as one of the protected areas in the
Grassland Biome was a great initiative towards biodiversity conservation.
Grassland, which forms the major vegetation type in the natural and semi-natural
areas in .the Potchefstroom area of the North West Province in South Africa, is
not included in the eight conservation "hot-spots" of plant diversity and endemism
in southern Africa, described by Cowling & Hilton-Taylor (1994). The term 'hotspots" describes areas that are characterized by high species richness, a high
concentration of endemic species and which are experiencing high rates of
habitat modification or loss. It is therefore imperative to determine the location
and extent of the niajor vegetation types within the Grassland Biome. Over the
past years, significant information was gathered on the grassland of the former
western Transvaal (Bezuidenhout et a/. (1994a, b, c, d and e). The vegetation of
heavily disturbed areas in and around urban environments in Potcliefstroom was
also studied by Cilliers and Bredenkamp (1998); Cilliers et a/. (1998), Cilliers &
Bredenkamp (1998) and Cilliers et a/. (1999).
The objectives of the present study to obtain data on the floristic composition and
structure of the plant communities in the HNP were achieved. The plant
communities in the HNP were identified, described and ecologically interpreted,
resulting in a total of 12 plant communities and 3 subcomniur~ities.Ider~ttfication
of these plant communities resulted in detailed vegetation and management unit
maps. The Braun-Blanquet approach proved to be an accurate and effective way
to identify and classify plant cow~mur~ities
based on their floristic composition.
Indirect and direct gradient analyses were successfully used to confirm and
refine the classification and to determine any possible environmental gradients.
Different types of soil erosion were also identified and categorized according to
their severity classes. Future management recommendations on soil erosion,
eradication of alien vegetation, burning regime and monitoring were also made.
The achievement of all these objectives serves as a basis to develop the
management plan for the HNP to ensure the sustainable utilisation and
conservation of the vegetation of the area. This study will serve as a tool to give
decision-makers on local, provincial and national level enough information to
continue to protect and develop this Grassland National Park in a sound and
ecologically sustainable manner.
At the beginning of 2007 when this study was at the completion phase, the fence
surrounding the park was constructed, and the main entrance gate to the park
was about to be finished. However, problems such as fence cutting, harvesting of
trees for firewood, uncontrolled fire and livestock grazing were still evident in the
park. This signifies the importance of conservation to the economy and to
people's lives as it is evident that the rural and urban poor are those worst
affected because they depend directly on the environment for their livelihood
(Mucina & Rutherford, 2006). The HNP is threatened by increasing urbanization
and it is of the utmost importance to recognize the causes of loss of biodiversity,
and implement measures to reduce these pressures and impact. There is a need
for regular and open communication between conservation bodies and affected
communities living adjacent to the park. Low levels of conflict are associated with
open and regular communication; while the absence of communication or the
selective giving of information is associated with high conflict (Fabricius et a/.,
2001). Many of the past conflicts arose from differences in knowledge and
~"~nderstanding
between communities and conservationists. It is therefore clear
that problems arising from the HNP are not only confined to those that are
measured scientifically, but also include a multitude of social ones as the park
exist in a social as well as an ecological matrix. Few studies on relationships
between human activity, species richness, and conservation requirements have,
to date, been undertaken (Chown eta/., 2003; Forester & Machlis, 1996) and it is
therefore necessary to identify the major social and economic forces that are
currently driving the loss of functional diversity (Folke et a/. 1996).
Due to the scope of the study, all other relevant questions arising during the
period of the study could not be addressed. For example, biodiversity loss
includes not just the extinction of species, but any charrge in species and
ecosystems that results from human activity and therefore compromising the
structuring processes upon which the survival of human beings depends
(Perrings et a/., 1992). Therefore, the potential driving forces of environmental
degradation and biodiversity loss, including human population growth, economic
development and policies need further studies (Meffe et a/. 1993). This approach
to biodiversity conservation supports a strategy that refocuses biodiversity
research and policy away from genetic information and conservation of species
for tourism and recreation in nature reserves and national parks, and towards
conservation for protection of ecosystem function and resilience (Perrings et a/.,
1992). Social ecology studies looking at sustainable utilization of natural
resources will also be of the utmost importance to the management of the park.
Degradation within and outside protected areas is also becoming a serious
concern and therefore there is a need for research linking degradation with
recent threats such as climate change. Changes in climate will require
adjustments to management, both to maximize the effectiveness of existing
protected areas (which may not have been selected for their biodiversity or with
climate change in mind) and to ensure that change is managed in a coordinated
fashion throughout the protected areas in a given system (Hannah & Salm,
2003). A new synthesis of biogeography and conservation biology is necessary
to respond to the challenges posed by climate change to the conservation of
biological diversity (Hannah et a/., 2002). Biogeography has developed
increasingly detailed understanding of past and future biotic responses to climate
change, but the application of these results in reserves design, selection and
management has been limited (Hannah eta/., 2002). New collaboration between
these disciplines is urgently needed if the impending impacts of anthropogenic
climate charlge are to be addressed in the strategies for conserving biodiversity.
There is also a need to monitor soil erosion and the effect of fire in the HNP.
Further research will enable a greater understanding of the complexities of the
fire and soil erosion relationship. The floristic composition of the HNP grassland
can be investigated further in an attempt to identify how the species composition
reacts to the frequency and timing of burns, as well as the continued monitoring
of the vegetation cover in response to different burn treatments. Tlie conti-ibution
of overgrazing and fire to erosion in comparison to natural erosion also requires
further study. Other negative impacts in the HNP include alien and invasive
species. Five alien species (Achyranthes aspera, Cirsium vulgare, Opuntia ficusindica, Solanum elaeagnifolium and Solanum sisymbrifolium) of Category 1
declared weeds were identified in the HNP. These are prohibited plants that
should not be tolerated as they are able to invade undisturbed environments and
transform or degrade natural plant communities (Henderson, 2001). One
species, Eucalyptus camaldulensis, a Category 2 plant, also occurs in the HNP.
This category includes plant species with proven potential of becoming invasive,
but which nevertheless have certain beneficial properties that warrant their
continued presence in certain circumstances (Henderson, 2001).
The analysis of potential herbivore carrying capacity as well as the ability to
support stable carnivore populations was also beyond the scope of this study and
need further detailed research. Vegetation in the HNP is already subjected to
overgrazing, resulting in degradation and the subsequent presence of many
pioneer species and exotic species as discussed in this thesis. The potential to
support stable predator populations within the park will be extremely limited
(Holness, 2003). For example, a single pride of 10 lions require around 45 000
ha and this suggests that an introduction of larger predators would be impossible
in the park (Holness, 2003). Further research is also required after introduction of
game in the park in order to monitor their effects on vegetation.
The future success of the HNP depends not only on the different stakeholders
(Potchefstroom City Council, South African Defence Force, Barolong Local
Community and South African National Parks) involved, but also requires the
undivided s~~pport
of the community at large.
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