Faculty of Education and Human Sciences

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Browsing Faculty of Education and Human Sciences by Advisor "Nakanyala, J."

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    Assessing savanna shrub roots deployment using radiogenic strontium isotopes in the North-Eastern Kalahari, Namibia
    (University of Namibia, 2024) Iipinge, Helalia N.; Nakanyala, J.
    The belowground interaction between trees and grasses in the savanna biome and mechanisms of moisture and nutrient uptake are poorly understood due to methodological challenges. To fill this gap, this study tested the robustness of the radiogenic strontium isotope method to study plant roots. The study was carried out at a landscape level, in Northeastern, Namibia. Plant leaves of four randomly selected shrubs and their 16 nearest neighborhood shrubs were collected within a 20 m x 20 m plot for isotopic analysis. This was done to assess the method’s performance. The study characterised the belowground structure and roots deployment of 17 of the 20 shrubs, sampled for isotopic analysis. It also assessed soil isotope, soil physicochemical properties, and the distribution of root biomass and density. Soil isotopes and soil physicochemical properties were analysed in the laboratory from 50 samples taken from five soil cores (10 cm interval, down to 1 m depth). A total of 450 soil samples were taken from 45 soil cores, spaced 2.5 m in 5 transects to determine root density and biomass. Data analysis was done in R.4.2.1. Results showed a relatively poor soil nutrient at the study site, but a high concentration of nutrients was recorded in the first 50 cm soil profile, where 75% of the root biomass is invested. Comparable strontium ratios were recorded along the soil profile, which did not vary significantly with soil depth (p = 0.44). Results indicated that plants’ isotopic ratios are neither attributed to rooting depths, nor to plant species. This study concluded that the isotope method lacks precision to establish shrubs’ rooting depths for ecological studies. However, an overlap between sampled plants and soils’ Sr ratios was recorded at the site, which makes the results precise for studies with interest in geographical variations of isotopes such as archaeology.