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Termites
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Termites interfere with many soil-forming processes that take
place in tropical regions through
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nest-building
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Fig.1 Termite mound Nigeria |
(
Source: Prof. Horst Fölster, Göttingen.) |
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enhancing soil horizon formation by mixing or sorting soil
constituents, i.e. relocation of material: clay migration and formation of a
textural gradient, and
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decomposition of SOM
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Termites have no carapace (panzer) and are prone to desiccation (construct
tunnels) and therefore build tunnels. They collect fresh and old plant materials,
often as far as 50 m away from their nest. They can collect up to 3800 kg per
hectare (~ 25 % of the total leaf fall) (Fölster, personal
communication).
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Fig.2 Termite mounds and tunnels |
(
Source: Prof. Horst Fölster, Göttingen.) |
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Termites bring fine soil material (0.5 bis 2 mm) to the surface
together with moisture leading to the formation of a textural gradient. The
diameter of the particles that termites transport is limited by the maximum
size they can carry in their mandibles. Generally, no gravel size grain can be
transported.
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Fig.3 |
(
Source: Prof. Horst Fölster, Göttingen.) |
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Termites dig into subsoil horizons and constantly bring new
materials to the surface. The amount of fine soil material (0.5 bis 2 mm)
displaced from the sub-soil to the surface can be as high as 300 to 1000
kg/ha/year (corresponding to 0.02 to 0.1 mm/year; Nye, 1955). At the surface
the impact of raindrops disrupts the aggregates and detaches clay from them.
Clay is removed as a suspension by runoff water to the valleys leaving behind
the coarse sand particles.
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Nye (1955) calculated that the mounds of Macrotemes bellicosus
on soils derived from gneiss near Ibadan, Nigeria could account for the
accumulation of a 30 cm surface mantle above the stone-line. The time required
for the accumulation was estimated at 12.000 years.
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A close correlation of the mineralogy of the sand fraction in
the surface soil and underneath in the stone line would acknowledge this
theory.
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