3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Spatio-temporal trends in vegetation dynamics across a savanna-dominated national park(2018) Ernst, Yolandi-MariThe Kruger National Park (KNP) is a savanna-dominated landscape upon which complex processes interact to result in dynamic patterns. Evidently, climate change is already impacting the KNP landscape. A major objective in the KNP’s Strategic Adaptive Management approach (SAM) is therefore to maintain ecological integrity through an informed, objective-driven decision-making process that involves Thresholds of Potential Concern. Continuous and informative monitoring at the landscape-scale is therefore essential, but challenging to do for such dynamic savanna environments, over large spatial extents. To address this concerning issue, I aimed to develop and evaluate a remote sensing-based methodological approach for the assessment and monitoring of landscape-scale spatio-temporal trends in vegetation greenness dynamics in relation to the influence of precipitation, fire and elephants across the Kruger National Park. My approach is novel in its combination of methods to monitor dynamic landscapes over large extents. Chapter 2 comprises of a comparison of different NDVI data products within the framework of mean-variance and spatial persistence analyses, thereby building the foundation upon which I based data analyses in the following chapters. Comparison of NDVI data derived from different satellite sensors revealed that the overall mean-variance trajectories and spatial persistence were relatively similar, but some large variations were evident due to differences in sensor characteristics. In Chapter 3, I exploited the fact that the relationship between phenology and vegetation greenness are confounded by the effect of other drivers. Through subjecting NDVI, phenology metrics and precipitation to spatial persistence analyses and then quantifying the converging and diverging change trends, I was able to show that precipitation is the primary driver of the general spatial greenness trends across the park but that persistent changes in vegetation greenness at finer spatial scales were more likely caused by other factors, such as fire and herbivory during the period of observation. Following this, I evaluated the role of fire and elephants as drivers of vegetation change trends with the use of pheno-season (defined by phenology metrics) vegetation greenness in correlation analyses. Here, the results seemed to suggest a combined association of elephants and fire frequency with vegetation greenness change trends, although the results showed much variability. Elephant bull and herd densities iii also seem to play different roles in their effects on vegetation greenness Through further development and adjustment of data input the proposed monitoring approach could be optimised for the broad-scale monitoring of vegetation pattern and processes within the SAM framework.