Which of the following abiotic factors is MOST responsible for determining the distribution of vegetation zones across Nigeria, from the mangrove swamps in the south to the Sahel savanna in the north?

Rainfall is the primary abiotic factor responsible for the distribution of vegetation zones in Nigeria, with the south receiving over 2,500 mm annually supporting rainforests and mangroves, while the north receives less than 500 mm supporting Sahel savanna. Temperature remains relatively high across Nigeria and does not vary as dramatically as rainfall. Soil type and wind speed are secondary factors influenced partly by rainfall patterns.