Content

Introduction
Readings
Fundamental Concepts
Self Check
Case Study Discussion
Summary
Self Review

Introduction

For many people, the mention of tropical forests conjures up images of rain forests dominated by very large trees. However, in reality, the area of dry forest in the Tropics exceeds the area of humid forest. With increasing dryness, the forests give way to woodlands, then shrublands, grasslands and eventually bare rock and sand. Within this gradient, there are numerous exceptions and outliers, and sometimes the observed vegetation patterns are very difficult to explain. An example is provided by some of the patches of savannah in western Africa, which are completely surrounded by rain forest.

In dry forests and woodlands, the balance between grassland and woodland is maintained by a complex set of interacting factors. Moisture availability, soil nutrition, herbivory and fire all play a role, as is shown when one of these is changed. For example, the occurrence of rinderpest in the Serengeti ecosystem of Tanzania resulted in major losses of ungulates, which in turn reduced browsing pressure and allowed woodland to develop in areas that were previously grassland. Similarly, changes in fire regimes can have a major effect on the balance between grasses and trees.

In this topic, we will first examine the different communities found in the savannahs of eastern and southern Africa. Although these range from tropical to sub-tropical, many species are shared. The emphasis in the first presentation is on mammals. In the second presentation, we will look at the bird communities. In the final presentation, we will examine both the direct and indirect processes that maintain the balance between trees and grasses in savannahs.

Outcomes

By the end of this topic, you should be able to:

Define savannahs and explain their place amongst the range of forests and woodlands found in the Tropics
Describe the major types of savannah found in eastern and southern Africa
Recall the main mammals found in each savannah type
Compare the different mammal faunas in each
Explain the importance of insects in savannahs
Describe some of the bird species present in savannahs
Compare the characteristics of birds in different groups, such a granivores and frugivores
Assess how birds contribute to the biodiversity of savannahs
Explain the principal environmental drivers that determine the balance between grassland and forest
Describe the main plant life forms found in savannahs
Assess the role of fire in maintaining savannahs
Compare the importance of fire and herbivory in savannahs
Evaluate the role of past events in explaining current patterns in savannah landscapes

Readings

Optional Readings

Du Toit, J.T., Rogers, K.H. and Biggs, H.C. (eds.) 2003. The Kruger experience. Ecology and management of savanna heterogeneity. Washington DC, USA: Island Press. 519 pp.
Scholes, R.J. and Walker, B.H. 1993. An African savannah. Synthesis of the Nylsvley study. Cambridge, UK: Cambridge University Press. 306 pp. Chapter 15.
Scogings, P.F. and Sankaran, M. (eds.) 2020. Savanna woody plants and large herbivores. Chichester, UK: John Wiley & Sons. 756 pp.
Shorrocks, B. and Bates, W. 2015. The biology of African savannahs. 2^nd Oxford, UK: Oxford University Press. 330 pp.
Sinclair, A.R.E. and Arcese, P. (eds.) 1995. Serengeti II. Dynamics, management, and conservation of an ecosystem. Chicago, Illinois, USA: University of Chicago Press. 665 pp.
Sinclair, A.R.E. and Norton-Griffiths, M. (eds.) Dynamics of an ecosystem. Chicago, Illinois, USA: University of Chicago Press. 389 pp.

Fundamental Concepts

PPT Presentations

This module contains three presentations:

5.1.11a Case study - The Savannahs of Southern and East Africa.pptx

5.1.11b Case Study - The birds of African savannas.pptx

5.1.11c Case study - The Savannahs of Southern and Eastern Africa (processes).pptx

Self-check Quiz (For certificate learning only)

After viewing topic presentations, take this self-check quiz to check your own progress. This quiz is designed to see how well you remember some of the issues presented in the topic. There are five questions, and each has a potential of 4 answers, only one of which is correct. When you are ready, click the link 'Self-check Quiz 5.1.11' to start taking the quiz.

Case Study Discussion (For certificate learning only)

Once you have have read the presentation, post a question about the ecology of the eastern and southern African savannahs, and answer/respond to at least one other question on the discussion board Case Study 11 Discussion - Savannahs of Southern and Eastern Africa.

Summary

Savannahs appear to be relatively simple ecosystems, but they reflect a complex balance between a range of ecological processes. They have been intensively studied, and our understanding of many (but not all) of these processes is quite well understood. Long-term studies at sites such as the Serengeti and Kruger National parks have enabled some of the population dynamics of species to be evaluated, and many ecological relationships, such as predator-prey dynamics have been studied in depth.

While emphasis is often placed on current processes, it is now clear that the recent history of savannas needs to be examined if the current distribution of grasslands and woodlands is to be fully explained. The ecological processes that determine this balance can vary over time, and are sometimes deeply perturbed. This can result in major changes to the ecosystem, moving it to a new state that may or may not be maintained.

Self-review (For self learning)

To review what you have learned in the topic, you are encouraged to use the following reflection questions as a study guide to do a self-review for the topic:

What defines a savannah, and how do they relate to other forests and woodlands found in the Tropics?
What are the major types of savannah found in eastern and southern Africa?
Which larger mammals would be you associate with each savannah type?
How to the mammals assemblages compare between different types of savannah?
What roles do insects play in savannah ecology?
Which broad types (e.g. frugivores) of birds would you expect to encounter in savannahs, and why?
How do the characteristics of birds in different groups, such a granivores and frugivores, compare?
What roles do birds play in the biodiversity of savannahs?
What are the principal environmental drivers that determine the balance between grassland and forest, and how do they work?
Which main plant life forms are found in savannahs?
What is the role of fire in maintaining savannahs?
What is the relative importance of fire and herbivory in the maintenance of savannahs?
What roles do past events play in explaining current patterns in savannah landscapes?

FODE 008-02