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,
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
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
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.)