(a) Highlight the distinguishing characteristics of the natural vegetation associated with either the cool temperate (eastern margin type) or the tropical c...

Answer Details

Selected vegetation: the tropical continental (savanna) climate.

(a) Distinguishing characteristics of the tropical continental (savanna) vegetation

1. It is dominated by tall grasses (which may grow 1-3 metres high) that turn brown and dry during the dry season.
2. Trees are scattered and short, growing in isolation or small clusters rather than forming a continuous canopy (open woodland/parkland).
3. The trees are deciduous or drought-resistant, shedding their leaves in the dry season to reduce water loss; many are umbrella-shaped (e.g. acacia) with broad, flat crowns.
4. Trees have adaptations such as thick, fire-resistant bark, long tap roots, small waxy leaves and thorns to survive drought and bush fires.
5. Vegetation becomes thicker and taller towards the wetter margin and thins into semi-desert scrub towards the drier margin (a clear north-south gradation).
6. Characteristic trees include the baobab, acacia, shea and locust bean.

(b) Factors that have aided the occurrence of this vegetation

1. Rainfall regime: a marked wet season followed by a long dry season allows grasses to flourish in the rains but prevents the growth of dense forest.
2. Moderate to low total rainfall: decreasing away from the equator, favouring grassland rather than rainforest.
3. High temperatures throughout the year which increase evaporation and moisture stress during the dry season.
4. Seasonal bush fires: frequent burning in the dry season kills seedlings of trees but favours the regrowth of fire-resistant grasses.
5. Human activities: farming, grazing by cattle and clearing of land have opened up the woodland and encouraged grassland.
6. Soil and relief: porous soils that dry out quickly and gently undulating land also favour grass over forest.