Browsing by Author "Ndagurwa, H.G.T."

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    Functional and species composition of understory plants varies with mistletoe-infection on Vachellia karroo trees in a semi-arid African savanna
    (Elsevier, 2021-10-27) Maponga, T.S.; Ndagurwa, H.G.T.; Witkowski, E.T.
    In savanna ecosystems, tree canopy patches differ in plant species composition compared to adjacent intercanopy spaces due to different levels of resource availabilities. Mistletoes further augment nutrients underneath tree canopies whilst reducing their hosts’ competitive edge, thus providing more resources and creating patches that support higher understory species richness. However, little is known on how understory species and functional trait assemblages, in both canopy and intercanopy spaces, are affected by varying overstory mistletoe infection intensities. This study investigated how functional and species diversity/composition varied within and between canopy patches and intercanopy spaces of high- and low mistletoe-infected Vachellia karroo trees. The affinity of individual species to the different canopy patches and intercanopy spaces was also assessed. Microhabitats had significantly different species compositions. A higher proportion of species (34%) showed a strong positive affinity towards canopy patches whilst intercanopy spaces were strongly associated with only 9% of recorded species, indicating greater dominance of some species there. Generally, subcanopy patches had significantly higher species richness and diversity, and functional diversity, compared to adjacent intercanopy spaces. These variables increased with increasing mistletoe infection, thus grass, forb and tree species diversity were 17–43% higher, and functional diversity indices were 0.5–28% greater in high- compared to low mistletoe-infection canopy patches. Furthermore, species richness and diversity of C3, C4, annual and perennial plants were 1.27–3.13-fold higher within canopy patches compared to intercanopy spaces and 1.28–1.74-fold greater within high- compared to low mistletoe-infection microhabitats. Consequently, high mistletoe-infection canopy patches had between 1.08 and 3.76-fold greater species richness and diversity of C3, C4, annual and perennial plants compared to the other three microhabitats. Our findings suggest that by enhancing spatial heterogeneity, variations in mistletoe infection facilitate biodiversity and to a lesser extent vegetation structural diversity in these semi-arid savannas.
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    Woody Species Diversity and Surface Soil Nutrients in an Opuntia Fulgida Engelm Invaded Semi-Arid Savannah Rangeland of South-West Zimbabwe
    (2018) Francis, B.; Pepler, D.; Ndagurwa, H.G.T.
    This study assessed the impact of the Opuntia fulgida invasion on the native vegetation in the south·western partt of Zimbabwe. Random sampling was used with three categories which were based on the history of invasion, namely, not invaded (O. fulgida absent), recently invaded (invaded in the mid-1990s) and historically invaded (invaded over 50 years ago}. Woody species richness and diversity and soil nutrient concentrations were assessed in each category. Soil samples were collected from the surface (O to 1Ocm) to determine the levels of pH, nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg), and their significant differences were realised. Woody species diversity and the levels of N declined with the increase of density levels of O. fulgida, while Mg increased. Generally, pH was low in all the sites while levels of P, K and Ca were insignificant. The significant differences in soil and vegetation variables suggest that O. fuLgida is altering soil nutrient, native vegetation structure and composition. The management of O. fulgida is therefore recommended.