(a) Draw an outline map of Nigeria and on it, show and name (i) the savanna belts and one important town in each of the belts (b) Highlight three vegetation...

(a) Outline map of Nigeria showing the savanna belts and one important town in each

Nigeria's savanna belts run in broadly east–west bands that succeed one another from south to north as rainfall declines. The map below shows the three belts and one representative town in each:

• Guinea Savanna (the southernmost, widest belt) — town: Ilorin (also Kaduna, Makurdi).
• Sudan Savanna (the middle belt) — town: Kano (also Sokoto).
• Sahel Savanna (the far north-eastern belt) — town: Maiduguri (also Nguru).

(b) Three vegetation characteristics of the Guinea Savanna belt

1. Presence of tall grasses. The ground is dominated by tall, coarse grasses that may reach about 3 metres in height by the end of the wet season.
2. Presence of tall, scattered trees. Fairly tall deciduous trees such as the locust bean and shea-butter tree stand scattered among the grasses, giving an open woodland (parkland) appearance. It is the wettest and most wooded of the savanna belts.
3. Trees shed their leaves in the dry season. The trees are drought- and fire-resistant, with thick bark, and shed their leaves during the long dry season to reduce water loss.

(By contrast, the Sudan Savanna has shorter grasses and shorter, thornier, more scattered trees such as acacia, while the Sahel Savanna carries only sparse short grasses and stunted thorn scrub.)

(c) Relationship between vegetation and rainfall in the savanna belts

The vegetation of the savanna is closely controlled by the amount and duration of rainfall, both of which decrease steadily from south to north. The main points of the relationship are:

1. Rainfall decreases from the Guinea Savanna in the south towards the northern (Sahel) limit; correspondingly the vegetation changes from tall grasses and numerous trees to short grasses and sparse thorn scrub.
2. The rainy season lasts longer in the Guinea Savanna than in the Sahel Savanna, so plants there enjoy a longer growing period, grow taller and remain green for more of the year.
3. The low rainfall of the Sahel (only about 20 cm falling to as little as 7 cm a year in the far north) is too little to support tall growth, so it leads to the stunted, thorny growth of trees and grasses.
4. The arrival of the rains marks the start of grass growth (the greening of the savanna), and the length of the dry season determines how long the grasses dry up and the trees stand leafless.

Thus the density, height and greenness of the savanna vegetation diminish in step with the declining rainfall from the Guinea belt in the south to the Sahel belt in the north.