Vegetation belts of Nigeria
Moving from south to north, Nigeria's natural vegetation shifts with the climate: mangrove swamp forest along the coast, tropical rainforest just inland (dense, evergreen, multiple canopy layers), guinea savanna in the middle belt (mixed grassland and trees), and Sudan/Sahel savanna in the far north (short grass, scattered thorny trees, adapted to low rainfall).
Example 1: Explain why Nigeria's vegetation changes from rainforest in the south to savanna in the north.
Vegetation closely follows rainfall amount and reliability. Southern Nigeria's high, year-round rainfall supports dense rainforest; as rainfall decreases and becomes more seasonal moving north, only more drought-tolerant grassland and scattered trees (savanna) can survive, since full rainforest needs far more consistent moisture than the north receives.
Farming systems
Shifting cultivation involves farming a plot of land for a few seasons until its fertility drops, then abandoning it to recover naturally (fallow) while a new plot is cleared -- traditional in areas with abundant land and low population density. Mixed farming combines crop growing and livestock rearing on the same farm, letting animal manure fertilize the soil. Modern, more intensive farming methods (irrigation, fertilizers, mechanization) are increasingly used where population pressure makes traditional shifting cultivation impractical.