Washington State Wetlands Identification And Delineation Manual Glossary

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Active Water Table

Back 1

A condition in which the zone of soil saturation fluctuates, resulting in periodic anaerobic soil conditions. Soils with an active water table often contain bright mottles and matrix chromas of 2 or less.

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Aerenchymous Tissue

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A type of plant tissue in which cells are unusually large and arranged in a manner that results in air spaces in the plant organ. Such tissues are often referred to as spongy and usually provide increased buoyancy.

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Aquatic Roots

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Roots that develop on stems above the normal position occupied by roots in response to prolonged inundation.

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Aquic Moisture Regime

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A mostly reducing soil moisture regime virtually free of dissolved oxygen due to saturation by ground water or its capillary fringe and occurring at periods when the soil temperature at 19.7 in. is greater than 5 degrees Celsius.

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Arched roots

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Roots produced on plant stems in a position above the normal position of roots, which serve to brace the plant during and following periods of prolonged inundation

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Backwater flooding

Back 6

Situations in which the source of inundation is overbank flooding from a nearby stream.

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Basal area

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The cross-sectional area of a tree trunk measured in square inches, square centimetres, etc. Basal area is normally measured at 4.5 ft above the ground level and is used as a measure of dominance. The most easily used tool for measuring basal area is a tape marked in square inches. When plotless methods are used, an angle gauge or prism will provide a means for rapidly determining basal area. This term is also applicable to the crosssectional area of a clumped herbaceous plant, measured at 1.0 in. above the soil surface

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Buried soil

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A once-exposed soil now covered by an alluvial, loessal, or other deposit (including
man-made).

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Canopy layer

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The uppermost layer of vegetation in a plant community. In forested areas, mature trees comprise the canopy layer, while the tallest herbaceous species constitute the canopy layer in a marsh.

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Capillary fringe

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A zone immediately above the water table (zero gauge pressure) in which water is drawn upward from the water table by capillary action

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Chroma

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The relative purity or saturation of a color; intensity of distinctive hue as related to grayness; one of the three variables of color.

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Comprehensive wetland determination

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A type of wetland determination that is based on the strongest possible evidence, requiring the collection of quantitative data.

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Deepwater aquatic habitat

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Any open water area that has a mean annual water depth >6.6 ft, lacks soil, and/or is either unvegetated or supports only floating or submersed macrophytes

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Drift line

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An accumulation of debris along a contour (parallel to the water flow) that represents
the height of an inundation event

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Duration (inundation/soil saturation)

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The length of time during which water stands at or above the soil surface (inundation), or during which the soil is saturated. As used herein, duration refers to a period during the growing season.

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Emergent plant

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A rooted herbaceous plant species that has parts extending above a water surface.

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Flooded

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A condition in which the soil surface is temporarily covered with flowing water from
any source, such as streams overflowing their banks, runoff from adjacent or surrounding slopes, inflow from high tides, or any combination of sources

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Frequently flooded

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- A flooding class in which flooding is likely to occur often under normal weather conditions (more than 50-percent chance of flooding in any year or more than 50 times in 100 years).

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Gleyed

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A soil condition resulting from prolonged soil saturation, which is manifested by the presence of bluish or greenish colors through the soil mass or in mottles (spots or streaks) among other colors. Gleying occurs under reducing soil conditions resulting from soil saturation, by
which iron is reduced predominantly to the ferrous state.

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Growing season

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The portion of the year when soil temperatures at 19.7 inches below the soil surface are higher than biologic zero (5 degrees Celsius)

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Headwater flooding

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A situation in which an area becomes inundated directly by surface runoff from upland areas

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Field capacity

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The percentage of water remaining in a soil after it has been saturated and after free drainage is negligible

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Herb

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A nonwoody individual of a macrophytic species. In this manual, seedlings of woody
plants (including vines) that are less than 3.2 ft in height are considered to be herbs.

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Herbaceous layer

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Any vegetative stratum of a plant community that is composed
predominantly of herbs.

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Histic epipedon

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An 8- to 16-in. soil layer at or near the surface that is saturated for 30 consecutive days or more during the growing season in most years and contains a minimum of 20 percent organic matter when no clay is present or a minimum of 30 percent organic matter when 60 percent or greater clay is present.

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Histosols

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An order in soil taxonomy composed of organic soils that have organic soil materials
in more than half of the upper 80 cm or that are of any thickness if directly overlying bedrock.

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Hue

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A characteristic of color that denotes a color in relation to red, yellow, blue, etc; one of the
three variables of color. Each color chart in the Munsell Color Book (Munsell Color 1975) consists
of a specific hue

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Hydric soil

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A hydric soil is a soil that formed under conditions of saturation, flooding, or ponding
long enough during the growing season to develop anaerobic conditions in the upper part. (USDANRCS
1995, Federal Register, 7/13/94, Vol. 59, No. 133, pp 35680-83). Hydric soils that occur in
areas having positive indicators of hydrophytic vegetation and wetland hydrology are wetland
soils.

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Hydric soil condition

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A situation in which characteristics exist that are associated with soil
development under reducing conditions

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Hydrologic regime

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The sum total of water that occurs in an area on average during a given
period.

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Hydrologic zone

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An area that is inundated or has saturated soils within a specified range of
frequency and duration of inundation and soil saturation

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Hydrophyte

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Any macrophyte that grows in water or on a substrate that is at least periodically
deficient in oxygen as a result of excessive water content; plants typically found in wet habitats.

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Hydrophytic vegetation

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The sum total of macrophytic plant life growing in water or on a
substrate that is at least periodically deficient in oxygen as a result of excessive water content.
When hydrophytic vegetation comprises a community where indicators of hydric soils and
wetland hydrology also occur, the area has wetland vegetation.

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Hypertrophied lenticels

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An exaggerated (oversized) pore on the surface of stems of woody plants through which gases are exchanged between the plant and the atmosphere. The enlarged lenticels serve as a mechanism for increasing oxygen to plant roots during periods of inundation
and/or saturated soils.

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Indicator

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As used in this manual, an event, entity, or condition that typically characterizes a
prescribed environment or situation; indicators determine or aid in determining whether or not
certain stated circumstances exist.

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Indicator status

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One of the categories (e.g. OBL) that describes the estimated probability of a
plant species occurring in wetlands.

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Intercellular air space

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A cavity between cells in plant tissues, resulting from variations in cell
shape and configuration. Aerenchymous tissue (a morphological adaptation found in many
hydrophytes) often has large intercellular air spaces.

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Inundation

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A condition in which water from any source temporarily or permanently covers a
land surface.

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Liana

Back 39

As used in this manual, a layer of vegetation in forested plant communities that consists
of woody vines. The term may also be applied to a given species.

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Limit of biological activity

Back 40

With reference to soils, the zone below which conditions preclude
normal growth of soil organisms. This term often is used to refer to the temperature (5’ C) in a soil
below which metabolic processes of soil microorganisms, plant roots, and animals are negligible

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Long duration (flooding)

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A flooding class in which the period of inundation for a single event
ranges from 7 days to 1 month.

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Macrophyte

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Any plant species that can be readily observed without the aid of optical
magnification. This includes all vascular plant species and mosses (e.g., Sphagnum spp.), as well as large algae (e.g. Chara spp., kelp).

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Major portion of the root zone

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The portion of the soil profile in which more than 50 percent of plant roots occur. In wetlands, this usually constitutes the upper 12 in. of the profile.

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Mapping unit

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As used in this manual, some common characteristic of soil, vegetation, and/or
hydrology that can be shown at the scale of mapping for the defined purpose and objectives of a survey.

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Mesophytic

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Any plant species growing where soil moisture and aeration conditions lie
between extremes. These species are typically found in habitats with average moisture
conditions, neither very dry nor very wet

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Mineral soil

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A soil consisting predominantly of, and having its properties determined
predominantly by, mineral matter usually containing less than 20 percent organic matter.

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Mottles

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Spots or blotches of different color or shades of color interspersed within the dominant
color in a soil layer, usually resulting from the presence of periodic reducing soil conditions.

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Muck

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Highly decomposed organic material in which the original plant parts are not recognizable

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Multitrunk

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A situation in which a single individual of a woody plant species has several stems

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Nonhydric soil

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A soil that has developed under predominantly aerobic soil conditions. These soils
normally support mesophytic or xerophytic species.

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Nonwetland

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Any area that has sufficiently dry conditions that indicators of hydrophytic
vegetation, hydric soils, and/or wetland hydrology are lacking. As used in this manual, any area that is neither a wetland, a deepwater aquatic habitat, nor other special aquatic site.

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Organic pan

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A layer usually occurring at 12 to 30 inches below the soil surface in
coarse-textured soils, in which organic matter and aluminum (with or without iron) accumulate at the point where the top of the water table most often occurs. Cementing of the organic matter slightly reduces permeability of this layer.

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Organic soil

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A soil is classified as an organic soil when it is: (1) saturated for prolonged
periods (unless artificially drained) and has more than 30-percent organic matter if the mineral fraction is more than 50-percent clay, or more than 20-percent organic matter if the mineral fraction has no clay; or (2) never saturated with water for more than a few days and having more than 34-percent organic matter.

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Oxidation-reduction process

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A complex of biochemical reactions in soil that influences the valence state of component elements and their ions. Prolonged soil saturation during the growing season elicits anaerobic conditions that shift the overall process to a reducing condition.

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Oxygen pathway

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The sequence of cells, intercellular spaces, tissues, and organs, through
which molecular oxygen is transported in plants. Plant species having pathways for oxygen
transport to the root system are often adapted for life in saturated soils.

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Parent material

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The unconsolidated and more or less weathered mineral or organic matter
from which a soil profile develops.

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Ped

Back 57

A unit of soil structure (e.g. aggregate, crumb, prism, block, or granule) formed by natural
processes.

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Peraquic moisture regime

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A soil condition in which a reducing environment always occurs
due to the presence of ground water at or near the soil surface.

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Periodically

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Used herein to define detectable regular or irregular saturated soil conditions or
inundation, resulting from ponding of ground water, precipitation, overland flow, stream
flooding, or tidal influences that occur(s) with hours, days, weeks, months, or even years
between events.

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Permeability

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A soil characteristic that enables water or air to move through the profile,
measured as the number of inches per hour that water moves downward through the saturated
soil. The rate at which water moves through the least permeable layer governs soil permeability.

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Physiognomy

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A term used to describe a plant community based on the growth habit (e.g.,
trees, herbs, lianas) of the dominant species

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Pneumatophore

Back 62

Modified roots that may function as a respiratory organ in species subjected
to frequent inundation or soil saturation (e.g., cypress knees).

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Ponded

Back 63

A condition in which water stands in a closed depression. Water may be removed only
by percolation, evaporation, and/or transpiration.

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Poorly drained

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Soils that commonly are wet at or near the surface during a sufficient part of
the year that field crops cannot be grown under natural conditions. Poorly drained conditions are caused by a saturated zone, a layer with low hydraulic conductivity, seepage, or a combination of these conditions.

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Prevalent vegetation

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The plant community or communities that occur in an area during a
given period. The prevalent vegetation is characterized by the dominant macrophytic species that
comprise the plant community.

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Redox potential

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A measure of the tendency of a system to donate or accept electrons, which is
governed by the nature and proportions of the oxidizing and reducing substances contained in the system.

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Reducing environment

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An environment conducive to the removal of oxygen and chemical
reduction of ions in the soils.

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Rhizosphere

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The zone of soil in which interactions between living plant roots and
microorganisms occur.

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Root zone

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The portion of a soil profile in which plant roots occur.

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Routine wetland determination

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A type of wetland determination in which office data and/or relatively simple, rapidly applied onsite methods are employed to determine whether or not an
area is a wetland. Most wetland determinations are of this type, which usually does not require
collection of quantitative data

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Sapling/shrub

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A layer of vegetation composed of woody plants <3.0 in. in diameter at breast
height but greater than 3.2 ft in height, exclusive of woody vines.

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Saturated soil conditions

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A condition in which all easily drained voids (pores between soil
particles in the root zone are temporarily or permanently filled with water to the soil surface at pressures greater than atmospheric.

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Soil -

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Unconsolidated mineral and organic material that supports, or is capable of supporting,
plants, and which has recognizable properties due to the integrated effect of climate and living
matter acting upon parent material, as conditioned by relief over time.

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Soil horizon

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A layer of soil or soil material approximately parallel to the land surface and
differing from adjacent genetically related layers in physical, chemical, and biological properties
or characteristics (e.g. color, structure, texture, etc.).

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Soil matrix

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The portion of a given soil having the dominant color. In most cases, the matrix
will be the portion of the soil having more than 50 percent of the same color.

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Soil permeability

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The ease with which gases, liquids, or plant roots penetrate or pass through a
layer of soil.

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Soil phase

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A subdivision of a soil series having features (e.g. slope, surface texture, and
stoniness) that affect the use and management of the soil, but which do not vary sufficiently to
differentiate it as a separate series. These are usually the basic mapping units on detailed soil
maps produced by the Soil Conservation Service.

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Soil pore

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- An area within soil occupied by either air or water, resulting from the arrangement of
individual soil particles or peds.

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Soil series

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The combination or arrangement of primary soil particles into secondary
particles, units, or peds

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Somewhat poorly drained

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Soils that are wet near enough to the surface or long enough that
planting or harvesting operations or crop growth is markedly restricted unless artificial drainage is provided. Somewhat poorly drained soils commonly have a layer with low hydraulic conductivity, wet conditions high in the profile, additions of water through seepage, or a
combination of these conditions.

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Stilted roots

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Aerial roots arising from stems (e.g., trunk and branches), presumably providing
plant support (e.g., Rhizophora mangle)

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Stooling

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A form of asexual reproduction in which new shoots are produced at the base of
senescing stems, often resulting in a multitrunk growth habit.

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Transition zone

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The area in which a change from wetlands to nonwetlands occurs. The
transition zone may be narrow or broad.

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Uniform vegetation

Back 84

As used herein, a situation in which the same group of dominant species
generally occurs throughout a given area.

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Upland

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As used herein, any area that does not qualify as a wetland because the associated
hydrologic regime is not sufficiently wet to elicit development of vegetation, soils, and/or
hydrologic characteristics associated with wetlands. Such areas occurring within floodplains are more appropriately termed nonwetlands.

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Value (soil color)

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The relative lightness or intensity of color, approximately a function of the
square root of the total amount of light reflected from a surface; one of the three variables of color.

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Vegetation layer

Back 87

A subunit of a plant community in which all component species exhibit the
same growth form (e.g., trees, saplings/shrubs, herbs).

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Very long duration (flooding)

Back 88

A duration class in which the length of a single inundation event is greater than 1 month.

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Very poorly drained

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Soils that are wet to the surface most of the time. These soils are wet
enough to prevent the growth of important crops (except rice) unless artificially drained.

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Watermark

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A line on a tree or other upright structure that represents the maximum static water
level reached during an inundation event.

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Water table

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The upper surface of ground water or that level below which the soil is saturated with
water. It is at least 6 in. thick and persists in the soil for more than a few weeks.

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Wetlands

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Those areas that are inundated or saturated by surface or ground water at a frequency
and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas.

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Wetland plant association

Back 93

Any grouping of plant species that recurs wherever certain wetland
conditions occur.

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Wetland vegetation

Back 94

The sum total of macrophytic plant life that occurs in areas where the
frequency and duration of inundation or soil saturation produce permanently or periodically
saturated soils of sufficient duration to exert a controlling influence on the plant species present. As used herein, hydrophytic vegetation occurring in areas that also have hydric soils and wetland hydrology may be properly referred to as wetland vegetation.

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Xerophytic

Back 95

A plant species that is typically adapted for life in conditions where a lack of water
is a limiting factor for growth and/or reproduction. These species are capable of growth in extremely dry conditions as a result of morphological, physiological, and/or reproductive adaptations.