May Almighty God protect and bless them all the days of their lives. I would like to thank Almighty God for giving me strength when I was weak, wisdom and courage to explore. My deepest gratitude goes to the management of Nylsvley Nature Reserve for allowing me to conduct my study in their reserve.
I thank all the graduate students in the Department of Botany who assisted me when I did fieldwork for my project. Its distribution area is from the South-West Cape northwards to Namibia, Angola, Botswana, Zambia and Zimbabwe. More mature healthy individuals were found in September and December than during June and July; this is of course because the early summer season, and in September most of the savanna plant species began to actively recover from the winter dry season.
GENERAL INTRODUCTION
- Background of the study
- Problem statement
- Research Questions
- Aim
- Objectives
- Null Hypothesis
- Alternative Hypothesis
- Justification for the study
Most of the nature reserves and parks are savanna ecosystems, for example Nylsvley Nature Reserve and Kruger National Park in South Africa. This results in seasons that are hot and dry lasting approximately 3 to 8 months, with wet seasons for the remainder of the year (Scholes and Archer, 1997). What management plan can be used to conserve V. The aim of the study was to assess the population biology and ecology of Vachellia karroo in the clay-flooded site of the NNR.
Vachellia karroo is one of the larger tree species of the savannah of the Nylsvley Nature Reserve. It is so important to understand the population structure of Vachellia karroo as it is one of the species characterizing the study area. It is therefore important to investigate the population biology of Vachellia karroo, as it is abundant in the clay-soaked soils of the Nylsvley Nature Reserve (NNR).
LITERATURE REVIEW
- Plant description
- Geography and Distribution
- Phenology and reproduction biology of Vachellia karroo
- Threats and Conservation status
- Taxonomy and ecology of Vachellia karroo
- Nutritive value of Vachellia karroo leaves
- Uses and cultural aspects
- Cultivation
Older branches are dark brown, fading to show a reddish understory (Barnes et al., 1996). It can form dense burrows in alluvium along rivers and in red clay (Bisby et al., 1994). Stone et al., (2003) also mentioned that contributors of the subgenus Phyllodinae have long and long plant lives, while most individuals of the subgenus Acacia and Aculeiferum have short-lived flora that appear as protandrous with a diurnal pattern in beneficial supply.
The tree usually has several leaves on the branches at all times of the year, even during periods of drought (Barnes et al., 1996). The tree also grows on acidic infertile soils with large temperature variations (Barnes et al., 1996). The plant has an elongated root that allows it to use water and nutrients from deep in the soil profile (Van Wyk and Gericke, 2000). Vachellia karroo contains high levels of crude protein (CP) and essential amino acids (Mapiye et al., 2011).
It is also used in the food, pharmaceutical, adhesive, detergent, ink, paint and agrochemical industries, as well as in glazing operations (Bisby et al., 1994). A substance has been discovered in the heartwood which is said to control high blood pressure (Bisby et al., 1994). The bark consists of 19% tannins and provides a dye which gives the leather a yellow-brown color (Bisby et al., 1994).
In drylands, it is mainly used to rehabilitate degraded land (which includes mine spoil) and to stabilize sand dunes (Bisby et al., 1994). Sweet thorn is also used for fiber and resin and the seeds are occasionally roasted to make a coffee substitute (Bisby et al., 1994). During the rest of the year, sweet thistle should be watered regularly from time to time until it is well established.
Vachellia karroo is susceptible to attack by whiteflies, and the Kew Botanic Gardens control pest populations by spraying the affected areas with a powerful jet water system (Barnes et al., 1996).
METHODS AND MATERIALS
Description of the study area
- Locality
- Geology
- Soils
- Drainage and Hydrology
- Vegetation
Savannah biomes cover about 20% of the world's land area and about half of the area of Africa and about 35% of South Africa (Scholes and Walker, 1993). In southern Africa, the bushveld is described by its vegetation structure, as the vegetation mainly consists of different layers of shrubs and trees occurring in a matrix with a herbaceous layer dominated by grass. The western and northern part of the reserve, especially along the plain surrounding the river Nyl, is covered with loam or clay soil.
Stemmerskop, which is one of the exits, is located in the central interior of the reserve at an altitude of 1,132 m above sea level. Maroelakop which is a second exit is positioned in the eastern corner of the reserve at an altitude of 1 154.2 m above sea level. A third and unidentified outlet is located inside the western corner of the nature reserve at an altitude of 1 122 m above sea level (LEDET, 2013).
The Central Sandy Bushveld found in the NNR is mainly covered with sedimentary rocks originating from the Waterberg Group. The NNR has the Nile River which flows through the central and north-eastern parts of the reserve thus forming a 70 km long grassy floodplain. Continuous flooding occurs at some point in the 12 months until the next wet season.
The dry season of the floodplain is generally characterized by a dry floodplain, with water only available in permanent pools located within the main stream of the Nile River. The Nylsvley floodplain wetland plays an important role in providing water for neighborhood flora and fauna, which is important in supporting the biodiversity of the area. The vegetation of the reserve accommodates Central Woodland vegetation units of the Savanna biome and a Freshwater Wetland vegetation unit (Alluvium plants) of Inland Azonal flora.
In Southern Africa, woodland is a description of the plant life form, as the vegetation is now mostly non-existent.
Sampling and measurements
Eighteen quadrats of 10 m x 10 m were sampled in September 2015 and data from one hundred and nine-one (191) individuals of V. Fourteen quadrats of 10 m x 10 m were sampled in December 2015 and data from one hundred and fifty-eight (158) individuals of V .
RESULTS AND DISCUSSION
If new seedlings are not recruited far into the adult population, this means that the population may additionally become locally extinct (Ryniker et al., 2006). Canopy coverage is the percentage of an area protected by the vertical projection of tree crowns (Jennings et al., 1999). Canopy cover plays an important role in defining present and future characteristics of forested areas through effects on the composition and structure of subsoil species (Canham et al., 1990).
Smith and Walker (1983) and Wiegand et al., (2005), indicated that larger plants have smaller neighbors due to their competitive effects. As the young plants grow, competition between young and mature plants will increase (Wiegand et al., 2006), so that the association disappears in the large length classes. Individuals with no damage were only 12% in July and 21% in September and in December it was 39% individuals with no damage of the total sampled individuals.
Fire appears to adversely affect mature trees by destroying their crowns and stems (Tshisikhawe et al., 2012). Competition also leads to negative spatial autocorrelation in plant size, such that taller plants have smaller neighbors (Cannell et al., 1984; Purves and Law, 2002). Despite the potential importance of variation in height, there have been few quantitative studies of the size distribution of tree species in unique forest communities (Porter et al., 2008).
Competition with herbaceous plants is also important at the seedling stage (Bush and van Auken 1990; McPherson 1993; Davis et al., 1998). The presence of a large number of juveniles compared to adults is understood to imply that a population is stable, perhaps increasing, while few juveniles may be seen as a warning that the population is declining (Condit et al., 1998). In the absence of direct estimates of population size over time, this appears to be a reasonable shortcut (Condit et al., 1998).
In most cases, it is easy to obtain estimates of the size distribution of a population, although it is much more difficult to establish long-term population trends (Condit et al., 1998). However, bell-shaped size class distributions are not always a problem for large, longer-living species, in which trees can maintain population levels with low or occasional recruitment (Condit et al., 1998). Condit et al., (1998) provide evidence that trees that develop rapidly in small size classes and trees that have a high survival rate will boast a flat size class distribution, and also that large, long-lived trees are capable of sustaining populations with low or periodic recruitment.
GENERAL CONCLUSION AND RECOMMENDATIONS
Conclusion
Recommendations
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How useful is the keystone species concept and can it be applied to Acacia erioloba in the Kalahari desert. Sprout selection and performance of goats fed on Acacia karroo coppice in the False Thornveld of the Eastern Cape, South Africa. Dynamics of shrub encroachment in an African savanna: Relative influences of fire, herbivory, rainfall and density dependence.
A comparison of the effects of different rangeland management systems on plant species composition, diversity and vegetation structure in a semi-arid savanna. The effect of competition on the structure and dynamics of Acacia savannas in southern Africa. The competitive interaction between Acacia karroo and the herbaceous layer and how it is affected by defoliation.
Relationships between woody and herbaceous components and the effects of shrub clearing in South African savannas. Effect of goat defoliation intensity in different phenophases on leaf and shoot growth of Acacia karroo Hyane. Baobab (Adansonia digitata L.) density, size class distribution and population trends among four land use types in northern Venda, South Africa.
Juvenile tree and seedling growth varies by both fire season and floor type: Fire trap trade-offs and transitions in an Australian savanna.
