Question

Which one or more of the following conditions can lead to an increase in tree densities in tropical savannas?

• A. Fire suppression
• B. Increase in mean annual rainfall
• C. Increased levels of browsing by herbivores
• D. Increased atmospheric CO2

Hint:

Fire suppression, increased rainfall, and higher CO2 levels can all lead to increased tree densities in savannas by reducing the limitations on tree growth.

Answer 1

The Correct Option is A, B, D

Step 1: Understand the dynamics of savanna ecosystems.
Savannas are grasslands with sparse trees. Several factors influence tree density in these ecosystems, including fire frequency, rainfall, browsing by herbivores, and atmospheric CO2 levels.
Step 2: Analyze the options.
- (A) Fire suppression can increase tree densities because fire is a key factor in limiting tree growth in savannas. When fire is suppressed, tree densities can increase.
- (B) An increase in mean annual rainfall provides more water for tree growth, promoting an increase in tree density.
- (C) Increased browsing by herbivores generally reduces tree densities by damaging or eating the trees. Therefore, this option is not correct.
- (D) Increased atmospheric CO2 enhances photosynthesis and can lead to increased tree growth, thus increasing tree densities.
Step 3: Conclusion.
The correct answers are (A), (B), and (D), as these factors all contribute to an increase in tree densities in tropical savannas.