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Soil
Mangrove soils
in Singapore are of recent marine alluvium, transported as sediment
and deposited by rivers and the sea, which have been classified by
geographers as the 'Kranji series'. Soils are made up of sand, silt
and clay in different combinations, and 'mud' actually refers to a
mixture of silt and clay, both of which are rich in organic matter
(detritus).
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Mangrove
Ecosystem
Abiotic components
Soil
pH
Oxygen
Nutrients
Winds and currents
Light, temperature, humidity
Tides
Salinity
Biotic components
Vegetation
Zonation |
Clayey-type
topsoil Sungai Mandai
Besar mangroves |
What
we see on the surface is topsoil, and are loosely recognised as sandy
or clayey types. The lighter-coloured sandy topsoils are porous and
facilitate water percolation and aeration during low tide. The darker-coloured
clayey topsoils, however, are less well aerated. |
Localised variation
can be further caused by burrowing animals like the Mud
lobster or Fiddler crabs.
| Soils
below the surface (subsoils) are typically waterlogged, have little
aeration which decreases with depth and contain a lot of organic matter
decomposing at a very slow rate. |
Sandy-type
topsoil Sungai Mandai
Besar mangroves |
"How
do I avoid sinking in the mud?"
Look for sand! Or make your way to tree roots or pneumatophores. Spread
over a wide area, roots offer good support to both the tree and yourself!
In a stream, walk in its centre - the coarser, heavier material such
as sand and pebbles found there provide relatively firm support. |
The
dark grey or black soil which produces a strong odour when unearthed
indicates the presence of hydrogen sulphide, the result of anaerobic
sulphur-reducing bacteria (e.g. Desuifovibrio sp.) which thrive
in the anoxic condition. |
Soil condition is one
of the contributing factors of zonation among animals and plants, e.g.,
different species of Fiddler crabs thrive in different soil conditions,
and while plants like Avicennia and Sonneratia
do well in sandy areas, Rhizophora copes better
with soft hurnus-rich mud while Bruguiera
favours stiff clay containing little organic matter. |
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