Wetland Ecology and Delineation Terminology

Vocabulary flashcards defining fundamental concepts, wetland classifications, biogeochemical processes, and delineation methods from the lecture notes.

Wetland (General Definition)

An ecosystem that arises when inundation by water produces soils dominated by anaerobic processes, which, in turn, forces the biota, particularly rooted plants, to adapt to flooding.

Wetland (Legal Definition)

Defined by the U.S. Army Corps of Engineers as areas that are inundated or saturated by surface or ground water at a frequency and duration to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soils.

Hydroperiod

The seasonal pattern of the water in a wetland that acts as its ecohydrological signature, defining the rise and fall of its water over time.

Recharge wetland

A wetland that collects surface water and allows it to slowly infiltrate the ground, replenishing underground aquifers and groundwater supplies.

Discharge wetland

An ecosystem that receives water flowing upward or outward from the groundwater system to the surface.

Spring tide wetland

A coastal or estuarine wetland located channelward of the high tide line that is routinely inundated by the highest high tides occurring twice a lunar month.

Neap tide wetland

The portion of a tidal wetland or coastal marsh that is hydrologically defined or bounded by the reach of a neap tide, representing a specific zone within an intertidal habitat governed by the minimum tidal ranges of the lunar cycle.

Seiche

A large standing wave that oscillates back and forth in an enclosed or semi-enclosed body of water, typically triggered by strong winds or sudden shifts in atmospheric pressure.

Intermediate Disturbance Hypothesis (IDH)

An ecological hypothesis stating that species diversity in wetlands is highest when ecological disturbances—such as periodic flooding, drying, or ice scouring—happen at moderate frequencies and intensities.

Redox potential

A numerical measure in millivolts ($\text{mV}$) of the electron availability and oxygen status in saturated soils or water, determining whether an environment is oxidizing (aerobic) or reducing (anaerobic).

Anoxia

A condition where molecular or free oxygen ($O_2$) is completely or virtually absent.

Hypoxia

A condition in wetlands and aquatic environments where dissolved oxygen concentrations drop below $2\text{ to }3\text{ mg/L}$, restricting normal respiration for most aerobic marine and aquatic life.

Denitrification

A microbially mediated process occurring in low-oxygen wetland soils where facultative anaerobic bacteria convert nitrate ($NO_3^{-}$) through intermediate gases into harmless nitrogen gas ($N_2$).

Nitrogen mineralization

The microbially mediated process in wetlands where organic nitrogen from dead plants, animals, and soil organic matter is broken down and converted into inorganic, plant-available forms such as ammonium ($NH_4^{+}$).

Nitrogen fixation

The biological process in which specialized microorganisms convert inert atmospheric nitrogen gas ($N_2$) into reactive, plant-usable forms such as ammonia ($NH_3$) or ammonium ($NH_4^{+}$).

Redoximorphic features

Characteristic soil color patterns and morphological traits formed by the reduction, translocation, and oxidation of iron ($Fe$) and manganese ($Mn$) oxides in seasonally or prolonged saturated and anaerobic wetland soils.

Histosol

A major soil order defined primarily by a thick layer of organic material—commonly known as peat or muck—that accumulates under waterlogged or cold wetland conditions.

Peat

A coarse, fibrous organic soil material composed of partially decayed plant matter where structural plant parts are still recognizable, accumulating under waterlogged, anoxic conditions.

Muck

A hydric soil made of heavily decomposed plant material that is fine-grained, smooth, and mostly pulverized, lacking recognizable coarse plant parts.

Ombrogenous raised bog

An acidic, dome-shaped wetland that rises above the surrounding landscape and receives water and nutrients exclusively from precipitation rather than from groundwater or streams.

Paludification

The ecological process where previously dry, vegetated land—such as a forest or grassland—transforms into a peatland or bog as organic matter accumulates and water is trapped at the surface.

Hue

The specific spectral color of soil (such as red, yellow, green, or blue), written as a letter and number combination in the top right corner of a Munsell chart page (e.g., 10YR or 2.5YR).

Value

The relative lightness or darkness of a soil color measured vertically on a Munsell scale from $0$ (absolute black) to $10$ (absolute white).

Chroma

The purity, intensity, or saturation of a soil color measured horizontally on a Munsell scale from weak/gray (low numbers like $1$ or $2$) to vivid/strong (high numbers like $6$ or $8$).

Redox concentrations

Rust-colored spots, masses, or pore linings formed in wetland soils when iron and manganese are mobilized under wet, anaerobic conditions and subsequently reoxidized.

Redox depletions

A redoximorphic feature where chemical reduction and saturation have stripped or transformed colored iron and manganese oxides from the soil matrix, leaving behind a grayish or light-colored zone of low chroma.

Depleted matrix

A soil layer where iron has been removed or transformed due to prolonged saturation and lack of oxygen, creating a grayish or bluish background color with low chroma and high value.

Gleyed matrix

A dominant background soil layer in wetland soils that exhibits low-chroma, bluish, greenish, or gray colors caused by prolonged saturation and iron reduction under anaerobic conditions.

Aerenchyma

A spongy plant tissue with large, interconnected air spaces that allows wetland and aquatic plants to transport oxygen from above-water parts down into their flooded, low-oxygen roots.

Adventitious roots

Specialized roots that grow from a plant's stem, trunk, or non-root tissues when the soil becomes flooded or soaked with water.

Pneumatophore

A specialized upward-growing aerial root that sticks out of water or mud in a wetland to help a plant breathe by taking in oxygen through lenticels.

Ecosystem engineer

An organism in a wetland that directly creates, significantly modifies, or maintains the physical habitat and water conditions, controlling resource availability for other species.

Hydrophytic vegetation

Plant life growing in water or in soil that is at least periodically deficient in oxygen due to excessive water content.

National Wetland Plant List (NWPL)

A standardized reference tool managed by the USACE, EPA, USFWS, and NRCS used to classify plant species based on their likelihood of occurring in wetlands versus non-wetlands.

Wetland Indicator Status

A designated rating assigned to a plant species that indicates how likely it is to grow in a wetland versus a non-wetland (upland) area.

Ecological disturbance

A physical or biological event that disrupts the structure of an ecosystem, community, or population and changes resource availability or the physical environment.

Forested wetland

A wetland dominated by large woody trees and hardwoods or conifers with an understory of ferns, mosses, and shrubs, fed by overflowing rivers, streams, or high groundwater tables.

Wet meadow

A wetland dominated by non-woody herbaceous plants such as grasses, sedges, rushes, and wildflowers (lacking trees and shrubs), with seasonally saturated or briefly flooded mineral hydric soils.

Marsh

A wetland frequently or continually inundated with standing water and dominated by soft-stemmed, emergent herbaceous vegetation such as cattails, reeds, bulrushes, and grasses.

Shallow water pond

A wetland permanently or semi-permanently flooded with open standing water ranging from $1$ to several feet deep, characterized by aquatic beds of submerged, floating-leaved, or free-floating plants.

Bog

An ombrotrophic peatland fed exclusively by precipitation, characterized by a thick carpet of Sphagnum moss, ericaceous shrubs, carnivorous plants, and highly acidic, nutrient-poor deep peat soils.

Fen

A minerotrophic peat-forming wetland fed by mineral-rich groundwater and surface runoff, dominated by grasses, sedges, and reeds, with soils that are less acidic and higher in nutrients than bogs.

Ramsar Convention

An international environmental treaty for the conservation and sustainable use of wetlands, signed on February 2, 1971, in Ramsar, Iran.

Hydrarch succession

A form of primary ecological succession (also known as hydrosere) that begins in an aquatic environment and gradually transitions into a stable, terrestrial land community as the basin fills with sediment and muck.

50/20 Rule

A delineation method for selecting dominants in a stratum by ranking species by cover, selecting those that cumulatively exceed $50\%$ of total cover, and including any additional species accounting for at least $20\%$ of the cover.

Rapid Test

A visual field method for hydrophytic vegetation where a site passes if all dominant plant species across all vegetation strata are rated as Obligate ($\text{OBL}$) or Facultative Wetland ($\text{FACW}$).

Dominance Test

A vegetation test where a community meets the hydrophytic criterion if more than $50\%$ of the combined dominant species across all strata have an indicator status of $\text{FAC}$, $\text{FACW}$, or $\text{OBL}$.

Prevalence Index

A cover-weighted average of the wetland indicator statuses of all plant species present within a sample plot, used to evaluate the presence of hydrophytic vegetation.

Halophytes

Specialized salt-tolerant plants that utilize anatomical and physiological adaptations to cope with osmotic stress and ion toxicity in high-salinity environments.