Where are mangrove forests found?
- found in areas experiencing tropical climate
- especially along sheltered coastal regions
- these are places where rivers constantly deposit clay and silt
How do mangrove forests adapt to the environment?
1. Structure
- 3 horizontal zones – coastal, middle and inland
- height: 2- 40m (why? muddy soil along coastal areas cannot provide firm support for very tall trees)
- average height of 15m, generally shorter than trees in tropical rainforests
- tress are salt tolerant plants known as halophytes – 4 main species (Avicennia, Sonneratia, Rhizophora and Bruguiera)
2. Roots
- 3 types of unusual roots which are adapted to soft, waterlogged soil
- in waterlogged conditions, soil lacks oxygen
- the roots are specially adapted to oxygen-deprived soil
AERIAL ROOTS
- during high tide, the roots are flooded with seawater (salt water)
- at low tide, the roots are exposed, allowing them to take in oxygen
- also known as breathing roots
- types of trees found at the coastal zone – Avicennie and Sonneratia
PROP ROOTS
- these roots anchor the trees firmly in the muddy soil
- also known as stilt roots
- types of trees found in the middle zone – Rhizophora
Knee Roots
- also known as kneed or knee-like roots
- tress that grows in the inland areas are the least tolerant to salt water
- types of trees found in the inland zone – Bruguiera
3. Flowers and Fruits
- flowers of mangrove trees are colourful
- e.g. Bruguiera – has bright red lantern-shaped flowers to attract insects to pollinate the flowers
- fruits of Avicennia (coastal zone) are buoyant – when they drop into water, the waves and current carry them to a new coastal location where they take root.
- fruits of Rhizophora (middle zone) have elongated structure with sharp tips – it will help the fruits to anchor themselves onto soft muddy ground – the fruits will grow while still attached to the parent tree and will eventually drop to the ground to take root.
4. Leaves
- evergreen
- broad with drip-tips – to allow water to flow off easily
- thick and leathery – to reduce water loss through transpiration
- leaves are adapted to regulate the amount of salt
- Avicennia (coastal zone) – salt secretors – remove excess salt on their leaves, which will then be removed by wind or rain
- Bruguiera, Rhizophora and Sonneratia (inland, middle and coastal zone) – ultrafiltrators – absorb salt – remove excess salt by storing it in old leaves, which will then fall off
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