Masters Degrees (Conservation Ecology and Entomology)

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Browsing Masters Degrees (Conservation Ecology and Entomology) by Author "Arendse, Lee-Roy"

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    The Properties and Effects of Dust from Unpaved Roads on Vegetation and Microbes in the Karoo
    (Stellenbosch : Stellenbosch University, 2020-03) Arendse, Lee-Roy; Jacobs, Shayne Martin; Crous, Casparus J.; Milton, Suzanne; Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology.
    ENGLISH ABSTRACT: There is minimal information on how dust from unpaved roads affects plant communities in the semi-arid Nama and Succulent-Karoo. One site per biome were used for conducting research, including the Square Kilometre Array (SKA), falling within the Nama Karoo biome and Wolwekraal Nature Reserve, falling within the Succulent Karoo biome. Each site was divided into four distance categories (D1 = 0–20 m; D2 = 20–100 m; D3 = 100–400 m; and D4 = 400–1000 m) from their respective unpaved roads. Within each distance category Modified Wilson and Cooke (MWAC) samplers were placed, on the soil surface and 1,3 m above the surface using steel rods and soil samples (including the road) were taken to a depth between 5 to 10 cm. After two months of dust sampling, samplers were collected to analyze the physical characteristics of dust (load and particle size); and microbial characteristics (fungal and bacterial composition and species richness) were determined in both the samplers and soil samples. Leaves from two shrubs (Pteronia glauca and Rhigozum trichotomum) in SKA and one shrub (Pteronia pallens) and a succulent (Ruschia spinosa) in Wolwekraal were sampled in each distance category. The leaves were analyzed for their leaf specific area (SLA), leaf stable carbon and nitrogen isotopes and metal ion deposits (Cu, Zn Cr, Pb and Ni). Results indicated unique patterns between sites. Mean dust loads were highest closest to the road (0-20 m) at both sites, and decreasing mean dust loads and particle size with increasing distance from the road were evident at SKA whereas mean dust loads and particle size displayed an inconsistent pattern along the distance gradient at Wolwekraal. Among the five metals Cr, Pb and Ni are carcinogenic and only these three metals had the highest concentration in the distance category closest to the road (0-20 m). Despite high dust loads and metal concentrations in the distance closest to the road it did not seem to significantly impact, with the exception of δ15N in P. glauca at SKA, the physiological indicators included (δ15N, δ13C, and SLA), which suggests only minor water and nitrogen-use impacts on plants, due to dust deposition. Dust transported from the road had low microbial species richness and influenced the samplers in the 0-20 m zone and associated soil samples by diminishing their microbial richness and diversity at SKA. Understanding the effects of dust pollution on plants and soil microorganisms would aid conservationists to better understand the nature of the environmental impacts facing arid and dust-prone areas. Based on the findings of the study it is recommended that implementation of dust mitigation techniques is applied in order to minimize dust generation from unpaved roads.