(a) Draw an outline map of Nigeria. On the map, show the annual distribution of rainfall.

(b) Highlight three effects of rainfall on the distribution of vegetation in Nigeria.

(c) Describe four characteristics of the Guinea Savanna

This was an unpopular question among the candidates.  Many of those who attempted it could not draw the map outline well. Many of them that answered the question could not state the effects of rainfall on the distribution of vegetation. The effects of rainfall on the distribution of vegetation include:

• as rain decreases northwards, density of vegetation decreases
• areas which have rainfall between 1000 mm and 1500 mm produces Guinea Savanna type of vegetation
• areas which have rainfall under 500 mm produces Sudan savanna type of vegetation
• areas with rainfall between 1500 mm – 2000 mm produces montane vegetation (e.g. Jos and Eastern highlands)
• high and continuous rainfall give rise to evergreen vegetation
• high rainfall areas of over 2000 mm gives rise to forest vegetation
• heavy rainfall supports tall trees in the south
• low rainfall supports growth of short deciduous trees in the north

The characteristics of the Guinea Savanna include:

• the largest of all vegetation belts in Nigeria;
• tall grasses;
• few scattered trees;
• tree types are oil palm, dum palm, shea butter, isoberlina, etc;
• trees are deciduous;
• trees have thick barks;
• trees have long tap roots;
• trees have tiny leaves to reduce transpiration;
• some trees have umbrella shaped canopy;
• grasses are green during rainy season and turn brown in the dry season.