They are important micromorphological features for two reasons:
They reflect environmental activity and a specific animal activity.
They often form an essential part of the soil structure.
They are mainly recognised by their shape, in accordance
with the terminology of Bal, Kooistra and Jongerius: spherical, ellipsoidal,
conoidal, cylindrical, mammillated, tuberous, etc.
Apart from intact excrements, aged excrements are very common in many soils.
Ageing is the alteration process of excrements resulting
from a loss of their original shape.
Coalescence. The excrements mix with each other to produce an undifferentiated mass.
Disintegration. The excrements disintegrate. First cracks appear and then the components separate, losing their cohesion.
Three degrees are recognised for both coalescence and for disintegration:
weak < 30%; moderate 30-70%; strong > 70%
Internal ageing. Excrements aggregate
to form higher units called micro-aggregates. Four degrees of micro-aggregates
are identified: very porous, porous, dense and very dense.
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