Some
terms for forest soils folks. 17.02.2003. jrb
(And, for those trying to write about forest
soils.)
(modestly edited from: SSSA
Glossary (http://www.soils.org/sssagloss/
) .
screefing: A method of preparing forest soils for planting or
seeding that consists of mechanically pushing aside the humus layer to expose
mineral soil.
litter: The surface layer of the forest floor which is not
in an advanced stage of decomposition, usually consisting of freshly fallen
leaves, needles, twigs, stems, bark, and fruits.
duff: See litter.
forest floor: All organic matter generated by forest vegetation,
including litter and unincorporated humus, on the mineral soil surface.
humus form: A group of soil horizons located at or near the
surface of a pedon, which have formed from organic residues, either separate
from or intermixed with, mineral material.
humus: Total of the organic compounds in soil exclusive of
undecayed plant and animal tissues, their "partial decomposition"
products, and the soil biomass. The term is often used synonymously with soil
organic matter.
mor: A type of forest humus characterized by an
accumulation or organic matter on the soil surface in matted Oe(F) horizons,
reflecting the dominant mycogenous decomposers. The boundary between the
organic horizon and the underlying mineral soil is abrupt. Sometimes
differentiated into the following groups: Hemimor, Humimor, Resimor, Lignomor,
Hydromor, Fibrimor, and Mesimor.
mull: A forest humus type characterized by intimate
incorporation of organic matter into the upper mineral soil (i.e. a well
developed A horizon) in contrast to accumulation on the surface. (Sometimes
differentiated into the following Groups: Vermimull, Rhizomull,
and Hydromull).
moder: A type of forest humus transitional between mull and
mor (term used mostly in Europe; also called duff mull in USA and Canada).
Sometimes differentiated into the following groups: Mormoder, Leptomoder,
Mullmoder, Lignomoder, Hydromoder, and
Sapimoder.
duff mull: A forest humus type, transitional between mull and
mor, characterized by an accumulation or organic matter on the soil surface in
friable Oe horizons, reflecting the dominant zoogenous decomposers. They are
similar to mors in that they generally
feature an accumulation of
partially to well-humified organic materials resting on the mineral soil. They
are similar to mulls in that they are zoologically active. Duff mulls usually
have four horizons: Oi(L), Oe(F), Oa(H), and A. Sometimes differentiated into
the following Groups: Mormoder, Leptomoder, Mullmoder, Lignomoder, Hydromoder,
and Saprimoder.
mesofauna:
Nematodes, oligochaete worms, smaller insect larvae, and microarthropods.
mesobiota:
See mesofauna.
microbiota:
Microflora and protozoa.
Oa horizon (H layer): A layer occurring in mor humus consisting of
well-decomposed organic matter of unrecognizable origin
(sapric material). See also
soil horizon and Appendix II.
Oe horizon (F layer): A layer of partially decomposed litter with portions
of plant structures still recognizable (hemic material).
Occurs below the L layer on
the forest floor in forest soils. It is the fermentation layer. See also soil
horizon and Appendix II.
Oi horizon [L layer
(litter)]: A layer of organic
material having undergone little or no decomposition (fibric material). On the
forest
floor this layer consists of
freshly fallen leaves, needles, twigs, stems, bark, and fruits. This layer may
be very thin or absent during
the growing season. See also
soil horizon and Appendix II.
mineral soil: A soil consisting predominantly of, and having its
properties determined predominantly by, mineral matter. Usually contains
<200 g kg-1organic carbon (< 120-180 g kg-1 if saturated with water), but
may contain an organic surface layer up to 30
cm thick.
surface soil: The uppermost part of the soil, ordinarily moved in
tillage, or its equivalent in uncultivated soils and ranging in depth from 7 to
25 cm. Frequently designated as the plow layer, the surface layer, the Ap
layer, or the Ap horizon. See also topsoil
topsoil: (i) The layer of soil moved in cultivation.
Frequently designated as the Ap layer or Ap horizon. See also surface soil.
(ii) Presumably fertile soil material used to topdress roadbanks, gardens, and
lawns.
krotovina: Irregular tubular streaks within one layer of
material transported from another layer by filling of tunnels made by burrowing
animals with material from outside the layer in which they are found.
agric horizon: A mineral soil horizon in which clay, silt and humus
derived from an overlying cultivated and fertilized layer have
accumulated. The wormholes and illuvial clay, silt and humus, occupy at
least 5% of the horizon by volume. The illuvial clay and humus occur as
horizontal lamellae or fibers, or as coatings on ped surfaces or in
wormholes.
organic soil: A soil in which the sum of the thicknesses of layers
containing organic soil materials is generally greater than the sum of the
thicknesses of mineral layers.
peat soil: An organic soil in which the plant residues are
recognizable. The sum of the thicknesses of the organic layers are usually
greater than the sum of the thicknesses of the mineral layers. See also peat,
muck, muck soil, and Histosol
.
muck soil: An organic soil in which the plant residues have
been altered beyond recognition. The sum of the thicknesses of organic layers
is usually greater than the sum of the thicknesses of mineral layers.
stony: (i) A stoniness class in which there are enough
stones at or near the soil surface to be a continuing nuisance during
operations that the mix the surface layer, but they do not make most such
operations impractical. (ii) Containing appreciable quantities of
stones. See also rock
fragments.
stoniness: Classes based on the relative proportion of stones
at or near the soil surface. Used as a phase distinction in mapping soils. See
also rock fragments
coarse fragments: See rock fragments
rock fragments: Unattached pieces of rock 2 mm in diameter or larger that are strongly cemented or more resistant to rupture. See Table 3 - http://www.soils.org/sssagloss/table3.gif - for terms that are used to classify rock fragments in soils.
boulders: Rock or mineral fragments >600 mm in
diameter. See also rock fragments.
bouldery: Containing
appreciable quantities of boulders..
stones: Rock or mineral fragments between 250 and 600
mm in diameter if rounded,
and
380 to 600 mm if flat.
flagstone: A relatively thin, flat rock fragment, from
150 to 380 mm on the long axis.
cobblestones: Rounded or partially rounded rock or mineral
fragments
between 75 and
250 mm in diameter. See also rock fragments
cobbly: Containing
appreciable quantities of cobblestones.
pebbles: Rounded or partially rounded rock or mineral
fragments between 2 and 75 mm
in
diameter. Size may be further
refined as fine pebbles (2-5 mm diameter), medium pebbles (5-20 mm diameter),
and coarse pebbles (20-75 mm diameter).
gravelly: Containing appreciable amounts of pebbles.
channer: In Scotland and
Ireland, gravel; in the USA, thin, flat rock fragments up to 150 mm on the long
axis. See also rock fragments.
channery: See rock
fragments..
laggy: Containing appreciable
quantities of flagstones. See also rock fragments.
Ground-Water Podzol soil: A great soil group of the intrazonal order and
hydromorphic suborder, consisting of soils with an organic mat on the surface
over a very thin layer of acid humus material underlain by a whitish-gray
leached layer, which may be as
much as 2 or 3 feet in
thickness, and is underlain by a brown, or very dark-brown, cemented hardpan
layer; formed under various types of forest vegetation in cool to tropical,
humid climates under conditions of poor drainage. (Not used in current U.S.
system of soil taxonomy.)
Tundra soils: (i) Soils characteristic of tundra regions. (ii) A
zonal great soil group consisting of soils with dark-brown peaty layers over
grayish horizons mottled with rust and having continually frozen substrata;
formed under frigid, humid climates, with poor drainage, and native
vegetation of lichens, moss, flowering plants, and shrubs. (Not used in current
U.S. system of soil taxonomy.)