A Dissertation Submitted in Partial Fulfilment of the Requirements for the Degree of
Master’s in Life Sciences of the Nelson Mandela African Institution of Science and
Technology
Habitat degradation, caused in particular by woody plant encroachment, has been a common
phenomenon in savanna ecosystems. With increasing woody plant cover in open savanna
grassland, structural changes and their associated impact need to be assessed and quantified.
We analyzed the extent of woody plant encroachment via remote sensing and assessed
encroached sites and open grassland of Maswa Game Reserve on the ground to identify and
examine encroaching woody plant species and their associated impacts on herbaceous plant
and herbivore species. We found that woody plant cover increased by 0.5% to 2.6% per
annum. Acacia drepanolobium dominated the woody encroaching species, and the number of
stems in heavily encroached sites was seven times and three times higher than in open
grassland and at medium encroached sites, respectively. Our results show that woody plant
encroachment reduces grazers and mixed feeder species occurrence. Furthermore, the number
of herbaceous species slightly increased with increase of woody plant encroachment, while
herbaceous cover was negatively correlated with increase of woody plant cover. Fire
significantly reduced germination success of A. drepanolobium. Intermediate simulated
rainfall was more beneficial to seedling emergence success than infrequent simulated rainfall,
while seedling shoots growth was significantly higher in frequent and intermediate simulated
rainfall treatments than under infrequent simulated rainfall. Hence, our study suggests that the
recent bush encroachment phenomena might have been stipulated by suppression of bush
fires and frequent low rainfall. This understanding will contribute in management of
vegetation specifically woody plants in savanna ecosystems that are important wildlife
habitats.