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Difficulty: Very hardVegetation Zones and Distribution in Nigeria

A biogeographer mapping ecological transitions across Nigeria compiles data on four distinct vegetation belts based on their key morphological adaptations and climatic controls:

- Zone W: High concentration of stilt roots and pneumatophores (breathing roots), adapted to anaerobic, saline muds under continuous daily tidal inundation.
- Zone X: Multi-storied closed canopy with buttressed roots, broad evergreen leaves, and abundant woody lianas under annual rainfall exceeding 2000 mm2000\text{ mm}.
- Zone Y: Open tree canopy dominated by fire-adapted species such as *Isoberlinia doka*, with an understory of tall perennial grasses subjected to a 4 to 6 month4\text{ to }6\text{ month} dry period.
- Zone Z: Short tussock grasses interspersed with thorny acacias and baobabs exhibiting microphyllous foliage and deep taproot systems under a dry season exceeding 8 months8\text{ months}.

Based on these structural characteristics and climatic parameters, which sequence correctly arranges these vegetation zones in order of increasing latitude from south to north across Nigeria?

  1. Zone W → Zone X → Zone Y → Zone ZAnswer
  2. B
    Zone X → Zone W → Zone Y → Zone Z
  3. C
    Zone Z → Zone Y → Zone X → Zone W
  4. D
    Zone W → Zone Y → Zone X → Zone Z

Answer

Zone W → Zone X �� Zone Y → Zone Z
The correct sequence (Zone W → Zone X → Zone Y → Zone Z) accurately follows the latitudinal gradient across Nigeria from south to north. Zone W represents the coastal Mangrove Swamp Forest (4°N–6°N), Zone X represents the humid Tropical High Rainforest (6°N–7°30'N), Zone Y represents the sub-humid Guinea Savanna (7°30'N–11°N), and Zone Z represents the semi-arid Sudan/Sahel Savanna (11°N–14°N). As latitude increases northwards, annual rainfall decreases and dry season duration lengthens, governing this spatial succession.

Step-by-Step Solution

1
Identify each vegetation zone based on its structural adaptations and climatic parameters.
Zone W corresponds to Mangrove Swamp Forest (coastal tidal muds, stilt roots, pneumatophores). Zone X corresponds to Tropical High Rainforest (dense multi-layered canopy, buttress roots, heavy rainfall >2000 mm). Zone Y corresponds to Guinea Savanna (open woodland, Isoberlinia doka, tall grasses, 4-6 month dry season). Zone Z corresponds to Sudan/Sahel Savanna (stunted thorny trees, microphyllous foliage, baobab, dry season >8 months).
Matching structural adaptations with climatic parameters defines the precise vegetation belt.
2
Determine the spatial latitudinal distribution of these identified vegetation zones in Nigeria.
Mangrove Swamp Forest occupies the extreme southern coast (approx. 4°N–6°N). Tropical Rainforest occupies the humid belt immediately north of the swamps (approx. 6°N–7°30'N). Guinea Savanna occupies the central region (approx. 7°30'N–11°N). Sudan/Sahel Savanna occupies the extreme north (approx. 11°N–14°N).
Nigeria's vegetation belts strictly reflect the decrease in annual precipitation and lengthening of the dry season from south to north.
3
Order the vegetation zones by increasing latitude (South to North).
Increasing latitude corresponds to moving from 4°N to 14°N (south to north), yielding the sequence: Zone W (Mangrove Swamp) → Zone X (Rainforest) → Zone Y (Guinea Savanna) → Zone Z (Sudan/Sahel Savanna).
Increasing latitude specifies a south-to-north transect.

Key Concept

Latitudinal Zonation of Vegetation Belts in Nigeria
Estimated Time:2m 0s
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Topics

Vegetation Zones and Distribution in Nigeria

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