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OF
Figure 3
zo
% volume
roots excluded
90
10
noz
OFzo : zoogenic transformed material >
10 % of the volume of the horizon after
removing living roots.
OFnoz : non zoogenic transformed
material >= 90 % of the volume of the
horizon after removing living roots.
ZOOGENIC TRANSFORMED MATERIAL = RECOGNIZABLE
REMAINS AND HUMIC COMPONENTS processed by animals
= leaves, needles and other plant residues more or less degraded
by soil animals, mixed with animal droppings. A fine powdered
and/or grained structure (less than 1 mm) is typical in a terminal
stage of faunal attack in an organic horizon. At this last level of
biotransformation, the substrate (OH horizon) is essentially
comprised of organic animal droppings of varying size (droppings
of epigeic earthworms, macroarthropods such as millipedes,
woodlice and insect larvae, microarthropods such as mites and
springtails and enchytraeids dominate). Within hemorganic
horizons, animal activity leads to different types of A horizons,
depending on the animals’ ability to dig into the mineral soil and
thoroughly mix organic and mineral matter.
NON ZOOGENIC TRANSFORMED MATERIAL = REMAINS AND
HUMIC COMPONENT processed by fungi or other non-faunal
processes = leaves, needles and other plant residues more or
less fragmented and transformed into fibrous matter by fungi.
Recognizable and recent animal droppings are absent or not
detectable by the naked eye in the organic horizons; fungal
hyphae can be recognized as white, brown or yellow strands
permeating the organic or hemorganic substrates; traces of animal
activity (old bite marks, mucus) may sometimes be detectable but
are always marginal. In the last stage of biodegradation of an
organic horizon, non zoogenic substance may essentially be
composed of brown, dry plant residues more or less in powder
form or tiny fragments (OF and OH horizons), or be massive like a
dark wet plastic clay (OH or very organic A horizons).