Global change drivers and their impact on herbaceous, ant, and grasshopper assemblages in an African semi-arid savanna
type: CreativeWork
description: Assessments of the anthropogenic threats to savanna ecosystems are primarily focussed on land use change, bush encroachment, and biological invasions. There is, however, very little understanding as to the threats from atmospheric pollution. South Africa is the major emitter of CO2 on the African content while the Mpumalanga region bordering the Kruger National Park (KNP) is among the leading regions for nitrous oxide pollution in the world. It is not only increasing atmospheric pollution, but rainfall intensity is also predicted to increase for southern Africa. As savannas are nutrient limited, an increase in nitrogen deposition will have major consequences for vegetation structure and this can only be exacerbated by increased rainfall amounts. Current research suggests that these predicted increases in water and nutrients will result in increasing grass biomass and decreasing herbaceous species richness. The effects of global change drivers on savanna vegetation are also likely to propagate through to multiple trophic levels, with changes in vegetation structure cascading down to invertebrate assemblages. As invertebrates are ubiquitous, form the bulk of metazoan species diversity and biomass on earth, and play a pivotal role in many ecosystems, I discuss in the introductory chapter of this thesis why the influence of global change on these assemblages should not be ignored. In my first data chapter, Chapter 2, I examine the effect that increases in available nutrients and water may have on vegetation structure, and how this may cascade down to grasshopper and ant assemblages. I do this using a fully factorial experiment in KNP with nutrient and water additions where I assessed both herbaceous (forb and grass) and insect (ant and grasshopper) assemblages five years after resource additions began. My results show that there was a substantial increase in grass biomass while plant and insect species richness declined with water addition alone and that a combination o…
abstract: Assessments of the anthropogenic threats to savanna ecosystems are primarily focussed on land use change, bush encroachment, and biological invasions. There is, however, very little understanding as to the threats from atmospheric pollution. South Africa is the major emitter of CO2 on the African content while the Mpumalanga region bordering the Kruger National Park (KNP) is among the leading regions for nitrous oxide pollution in the world. It is not only increasing atmospheric pollution, but rainfall intensity is also predicted to increase for southern Africa. As savannas are nutrient limited, an increase in nitrogen deposition will have major consequences for vegetation structure and this can only be exacerbated by increased rainfall amounts. Current research suggests that these predicted increases in water and nutrients will result in increasing grass biomass and decreasing herbaceous species richness. The effects of global change drivers on savanna vegetation are also likely to propagate through to multiple trophic levels, with changes in vegetation structure cascading down to invertebrate assemblages. As invertebrates are ubiquitous, form the bulk of metazoan species diversity and biomass on earth, and play a pivotal role in many ecosystems, I discuss in the introductory chapter of this thesis why the influence of global change on these assemblages should not be ignored. In my first data chapter, Chapter 2, I examine the effect that increases in available nutrients and water may have on vegetation structure, and how this may cascade down to grasshopper and ant assemblages. I do this using a fully factorial experiment in KNP with nutrient and water additions where I assessed both herbaceous (forb and grass) and insect (ant and grasshopper) assemblages five years after resource additions began. My results show that there was a substantial increase in grass biomass while plant and insect species richness declined with water addition alone and that a combination o…
author: Trisos, Matthew Owen
language: eng
date published: 2020
date modified: 2026-07-22T22:23:30Z
provider: University of Cape Town
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cape Town

PropertyValue
property ID: Handle
value: http://hdl.handle.net/11427/32517