Browsing by Author "De Agrela, Robert Joao"

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    The relationship between multispectral satellite-derived vegetation indices and forage quantity and quality indicators in Mountain Zebra National Park
    (Stellenbosch : Stellenbosch University, 2019-12) De Agrela, Robert Joao; Raffrenato, Emiliano; Gaylard, Angela; Ramoelo, Abel; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science.
    ENGLISH ABSTRACT: Climate change and human population growth has put pressure on protected areas and wilderness in southern Africa, consequently limiting food availability for herbivores. This is a major concern as forage quantity and quality available to herbivores affect the health and dynamics of herbivore populations. Therefore, the monitoring and assessment of forage quantity and quality across a landscape can potentially help ecologists make appropriate management decisions for herbivore populations in protected areas. Remote sensing measuring techniques, specifically multispectral satellite-derived vegetation indices (VI’s), can be a useful tool in providing information and knowledge about forage quantity and quality for herbivores, and the possible changes in these resources. However, for the accurate interpretation and implementation of multispectral satellite-derived VI’s, their relationship between forage quantity and quality indicators within the desired area needs to be determined. Therefore, this study assessed the relationship between multispectral remote sensors, onboard the MODIS and Sentinel-2 satellites, and forage quantity and quality indicators in MZNP. Forage biomass was estimated and used as a forage quantity indicator and forage nutrients were analysed and used as an indicator for forage quality. Correlations and regression techniques were applied, and results showed different multispectral satellite-derived VI’s have, at different strengths, relationships with the different forage quantity and quality indicators. The MODIS Normalized Difference Vegetation Index (NDVI), rather than the MODIS Enhanced Vegetation Index (EVI), showed a strong relationship with biomass and was more related to the amount of high forage quality in MZNP. The Sentinel-2 Chlorophyll Red-Edge index (Chlred-edge) had a very strong relationship with forage quality indicator total N concentration. Strong relationships were also found between the Green Chlorophyll Index (Clgreen), NDVI and MODIS NDVI and the forage quality indicators fiber (NDF, NDFd and ADL) and potassium. Herbivore faecal samples from the dominant ungulate species in MZNP were also analysed for forage quality indicators and related to the multispectral satellite-derived VI’s, to determine the relationship between VI’s and the diets of the herbivores in MZNP. Results showed associations between the MODIS NDVI and EVI can be generally related to dietary nitrogen, phosphorus and magnesium for the park’s dominant ungulate species. The research in this study also found valuable information on the relationship between remote sensing and forage quantity and quality, which up to now has lacked sufficient research. This study shows the implementation of multispectral satellite-derived VI’s can assist with the monitoring and assessment of forage quantity and quality for the herbivores of MZNP and will aid in making appropriate herbivore management decisions. The information uncovered by this study also demonstrates relationships between VI’s and forage quantity and quality that require improved understanding across a wider range of ecosystems.