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North-West University (2019)

The effect of fire on savanna vegetation dynamics in the semi-arid Molopo Bushveld region of the North-West Province, South Africa

Esterhuizen, Anja

Titre : The effect of fire on savanna vegetation dynamics in the semi-arid Molopo Bushveld region of the North-West Province, South Africa

Auteur : Esterhuizen, Anja

Université de soutenance : North-West University

Grade : Master of Science in Environmental Sciences 2019

Résumé partiel
Land degradation in semi-arid areas is a worldwide phenomenon. Both land users and researchers have become increasingly aware of the environmental changes that occur over time due to land degradation. Among such changes, bush encroachment results from land degradation, especially in savanna rangeland areas. Fire is known as a major driver of the dynamics of woody and herbaceous vegetation dynamics in the savanna biome. A workshop held in Potchefstroom, North-West Province, South Africa, in 2015 for the IDESSA project (IDESSA : An integrative decision-support system for sustainable rangeland management in southern African savannas) within the BMBF (German Federal Ministry of Education and Research) SPACES framework (SPACES : Science Partnerships for the Assessment of Complex Earth System Processes) indicated that more in-depth scientific information was needed on the potential role of fires in the dynamics and shaping of the savanna vegetation of the Molopo Bushveld region in the North-West Province, which is a semi-arid area. Several studies have indicated the potential use of fire to maintain the balance between woody and grass species and to prevent bush encroachment. However, information is limited with regards to this specific area. The study area comprised three locations, namely the Molopo Nature Reserve (Molopo), Khamab Reserve (Khamab) and a commercial cattle farm (Farm) in the Molopo Bushveld region. Each area was divided into reference and burnt sites. The reference sites included unburnt sites within the Molopo and Khamab area and burnt sites within the Farm area as there were no non-burnt sites within the Farm area. The first objective of this study was therefore to assess the effects of fire on the vegetation composition and structure in the Molopo Bushveld region. This objective was achieved by conducting vegetation surveys that included the use of belt transects for the woody component and a step-point method for the herbaceous component. The second objective was to evaluate the use of fire as a management tool to make long-term predictions and management decisions in semi-arid savanna areas. This objective was achieved by using semi-structured interviews with land users and questionnaires which included relevant questions regarding management, vegetation, rainfall, causes of fires and damage suffered due to the fire ; as well as by analysing and comparing the gathered quantitative and qualitative data. Considering the various studies done on the influence of fire on savanna vegetation, the hypothesis for this study was that fire events influence the structure and composition of the vegetation in semi-arid savanna regions and can be used as a management tool, especially in terms of land degradation caused by bush encroachment. The results indicated vegetation differences within reference and burnt sites. However, the results were inconsistent, except for Grewia flava, which had higher densities in burnt sites than in reference sites.

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