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Norwegian University of Science and Technology (NTNU) 2019

The impact of wild and domestic herbivores on aboveground productivity in an East-African savannah

Arneberg, Marit Klemetsen

Titre : The impact of wild and domestic herbivores on aboveground productivity in an East-African savannah

Auteur : Arneberg, Marit Klemetsen

Université de soutenance : Norwegian University of Science and Technology (NTNU)

Grade : Master’s thesis in Biology 2019

Résumé partiel
Plant productivity in African savannahs is widely recognized to depend on temporal and spatial variations in climate, soil properties and disturbances, mainly fire and herbivory. Human driven land-use change has increased over the last few decades, and is altering the dominant herbivores in savannahs from highly mobile assemblages of wild herbivores to less mobile and typically higher densities of livestock. This shift in herbivory impact is likely to affect the temporal patterns in productivity of the savannahs. In this study, we quantified the impacts of livestock and wildlife grazing on net aboveground productivity and herbivore consumption inside wildlife protected areas in the Serengeti National Park, Tanzania, and adjacent livestock dominated pasturelands outside protected areas. This was achieved by harvesting vegetation using moveable exclosures and paired open plots. Herbaceous biomass was destructively measured seven times over a 15 months period. Additionally we surveyed dominant and subordinate plant species consumption and determined cumulative rainfall between harvest periods using remote satellite images. Overall we found that net aboveground primary productivity is mainly driven by rainfall and maintained at relatively high levels in both livestock dominated pastures and wildlife protected areas. Despite similar productivity between land-uses, rates of herbivore consumption was higher in livestock dominated pastures compared to wildlife protected areas, especially when rainfall and plant biomass was scarce. Over the duration of our experiment accumulated productivity did not differ between land-uses ; however, the magnitude of total consumption in the livestock dominated pastures is much greater and less dependent on accumulated rainfall, compared to the wildlife protected areas. Local dominant grass species did not differ in productivity between land-uses and were equally productive as the subordinate species. Furthermore, the dominant plant species were consumed to a much lower extent than subordinate species, regardless of land-use.

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