Content
Topic Introduction
In this final topic of Module 2, we bring together the material that you have examined in the first four topics, and show how patterns of vegetation in tropical forests vary over time and space. Each time a disturbance creates a gap in the canopy, it sets in motion a process that ultimately results in the gap being completely filled. Given what you have learnt about the diversity of tree species in tropical forests, it is easy to imagine that the infill occurs purely by chance. While chance certainly plays a major role, not every species will be able to fill the gap. Earlier in this module, we showed how some species had functional traits that gave them an edge over other species, although these traits often came at a cost. Success in filling a canopy gap very much depends on successful those trade-offs have been.
As gaps form frequently, and vary in size from individual trees, to small groups of trees to large areas, the forest can be seen as a mosaic consisting of numerous gaps, each at a different stage of development. While succession theory suggests that the development of vegetation in these gaps will ultimately reach a pre-determined point, this does not seem applicable to tropical forests. Rather than being a single end point, there are multiple end points, and these may not be reached before the cycle is renewed.
Outcomes
By the end of this topic, you should be able to:
- Describe how tropical forests are renewed.
- Demonstrate that patterns in tropical forests can be related to their recent and past history.
- Evaluate the relative benefits of different reproduction strategies in the persistence of species.
Topic Readings
Required Readings
- Ghazoul, J. and Sheil, D. 2010. Tropical Rain Forest Ecology, Diversity, and Conservation. Oxford, Oxford University Press, 516 pp. Sections 9.4 and 9.5.
Optional Readings
There are no supplementary readings for this topic
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 more important 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 2.5 to start taking the quiz.
Pre-readings and Discussion (For certificate learning only)
Once you have read Sections 9.4 and 9.5 of Ghazoul, J. and Sheil, D. 2010. Tropical Rain Forest Ecology, Diversity, and Conservation, choose to post one thought provoking question related to the material that you have read, and answer/respond to at least one other student’s question on Module 2 discussion board Module 2 Discussion.
Graded Assignments (For certificate learning only)
Six Sentence Answer #5
Please refer to the course pages on graded assessments to see details of the Six-sentence Answers (6SA) exercise. You should not attempt to do this assessment until you have read and fully understood the requirements.
The Case
You are a member of a major international forest consultancy firm that specializes in doing surveys of forests around the world. Your company is working on a contract looking at the effects of past and present management practices on the forests and savannahs of East Africa. This area is very diverse, including many different forest types. They range from grass and tree savannahs through seasonally dry woodlands and forests to Afromontane rain forest.
Your manager has suggested that you concentrate all your work on “climax” forests in the region. Using the 6SA format, explain why this approach is inappropriate.
Remember to follow the structure of the 6SA outlined in the section on graded assessments.
Formatting:
- Double-space the text.
- 12-point font in New Times Roman or Calibri.
- Put your name (Family or last name, followed by your first name), student number, the title “Topic 1.1 assignment”, and the date at the top of the first page.
- Name the e-file: your Family or last name_your first name_ Topic 1.1_Assignment.doc (or .docx). Example: Innes_John_Topic 1.1_Assignment (or .docx).
- Standard English usage, clear writing style.
- All assignments should be submitted through Canvas before the deadline.
Topic Summary
In this topic, we examined the patterns that occur in tropical forests, both in space and time. Most of the presentation concentrated on tropical moist forests as there is much less information available for seasonally dry forests. However, these marked spatial variation, especially between patches of grassland and patches of trees (see the case study on savannahs, Topic 5.16).
It is possible to recognize some species as characteristic of early colonization of gaps, whereas others only become established later. Species within some families appear to share a number of traits that enable them to be successful early colonizers. Others are better adapted to surviving in the understorey until a gap forms. The result is a mosaic of different patches, each developing at a different rate and with a different combination of species present. Some species may be relatively common in newly formed gaps, others may be more frequent 10–20 years after gap formation. In addition to these more common species, there will also be rarer species that are present by chance.
Topic 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 are the processes that stop stands entering what has sometimes been termed a ‘degenerate’ phase?
- What evidence would you use to demonstrate that patterns in tropical forests can be related to their recent and past history
- What are the relative benefits of different reproduction strategies in the persistence of species?
- How would describe the dynamics of a large area of tropical moist forest?
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