Classification > Ecological Systems > Wetland Ecological System Key

Ecological System Key

Important information for using this key

The scale at which ecological systems are delineated is important. Make sure to look at the larger landscape when using this key. A mosaic of herbaceous and shrubby vegetation patches does not necessarily mean multiple ecological systems. Changes in dominant soil type, however, can mean multiple ecological systems. Pay close attention to the size thresholds in the key when determining the ecological system or systems present. Percent cover thresholds are guidelines for the footprint of an entire stratum, not the percent cover of individual species, and are determined for the overall ecological system rather than the confines of a specific patch.



Field Key to Wetland and Riparian Ecological Systems of Colorado

1a. Wetlands and riparian areas of Colorado’s Great Plains, including all areas below ~6,000 ft. from the Front Range east to the Kansas boarder. Within Colorado, this area is referred to as the Eastern Plains, but from a national perspective, these are the Western Great Plains or the High Plains. [If on the edge of the foothills, try both Key A and Key B.]
Go to...............Key A: Wetlands and Riparian Areas of the Western Great Plains
1b. Wetland and riparian areas west of the Great Plains
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2a. Wetlands and riparian areas with alkaline or saline soils within the inter-mountains basins of the Rocky Mountains (San Luis Valley, South Park, North Park, etc.). [If the site does not match any of the descriptions within Key B, try Key C as well. Not all wetlands and riparian areas of the inter-mountain basis will fit within this key.]
Go to...............Key B: Wetlands and Riparian Areas of the Inter-Mountain Basins
2b. Wetlands and riparian areas of the Rocky Mountains, including the foothills of the Front Range and all of the West Slope. Localized “hanging garden” wetlands of the Colorado Plateau are also keyed here, as they are the only system specific to that region.
Go to........................................Key C: Wetlands and Riparian Areas of the Rocky Mountains



Key A: Wetlands and Riparian Areas of the Western Great Plains

1a. Low stature shrublands dominated by species such as Sarcobatus vermiculatus, Atriplex spp., Ericameria nauseosa, Artemisia cana, and Artemisia tridentata. Vegetation may be sparse and soils may be saline. Sites may be located on flats or in washes, but typically not associated with river and stream floodplains. [These systems were originally described for the Inter-Mountain Basins, but may extend to the plains.]
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1b. Wetland is not a low stature shrub-dominated saline wash or flat.
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2a. Shrublands with >10% total vegetation cover, located on flats or in temporarily or intermittently flooded drainages, and dominated by Sarcobatus vermiculatus and Atriplex spp. with inclusions of Sporobolus airoides, Pascopyrum smithii, Distichlis spicata, Puccinellia nuttalliana, and Eleocharis palustris herbaceous vegetation.
Go to........................................Inter-Mountain Basins Greasewood Flat
2b. Sites with < 10% total vegetation cover and restricted to temporarily or intermittently flooded drainages with a variety of sparse or patchy vegetation including Sarcobatus vermiculatus, Ericameria nauseosa, Artemisia cana, Artemisia tridentata, Grayia spinosa, Distichlis spicata, and Sporobolus airoides.
Go to........................................Inter-Mountain Basins Wash

3a. Sites located within the floodplain or immediate riparian zone of a river or stream. Vegetation may be entirely herbaceous or may contain tall stature woody species, such as Populus spp. or Salix spp. Water levels variable. Woody vegetation that occurs along reservoir edges can also be included here.
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3b. Herbaceous wetlands of the Western Great Plains that are isolated or partially isolated from floodplains and riparian zones, often depressional with or without an outlet.
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4a. Herbaceous wetlands within the floodplain with standing water at or above the surface throughout the growing season, except in drought years. Water levels are often high at some point during the growing season, but managed systems may be drawn down at any point depending on water management regimes. Vegetation typically dominated by species of Typha, Scirpus, Schoenoplectus, Carex, Eleocharis, Juncus, and floating genera such as Potamogeton, Sagittaria, and Ceratophyllum. The floodplain expression of this system is located on the floodplain, but may be disconnected from flooding regimes. The hydrology may be entirely managed. Water may be brackish or not. Soils are highly variable. This system includes natural warm water sloughs and other natural floodplain marshes as well as a variety of managed wetlands on the floodplain (e.g., recharge ponds, moist soil units, shallow gravel pits, etc.) .
Go to........................................Western North American Emergent Marsh
4b. Not as above. Wetland and riparian vegetation that typically lacks extensive standing water. Vegetation may be herbaceous or woody. Management regimes variable.
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5a. Large herbaceous wetlands within the floodplain associated with a high water table that is controlled by artificial overland flow (irrigation). Sites typically lack prolonged standing water. Vegetation is dominated by native or non-native herbaceous species; graminoids have the highest canopy cover. Species composition may be dominated by non-native hay grasses. Patches of emergent marsh vegetation and standing water are less than 0.1 ha in size and not the predominant vegetation.
Go to............................Irrigated Wet Meadow [Not an official Ecological System.]
5b. Predominantly natural vegetation (though may be weedy and altered) within the floodplain or immediate riparian zone of a river or stream, dominated by either woody or herbaceous species. Not obviously controlled by irrigation.
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6a. Riparian woodlands and shrublands of the Rocky Mountain foothills on the very western margins of the Great Plains. Woodlands are dominated by Populus spp. (Populus angustifolia, P. deltoides, or the hybrid P. acuminata). Common native shrub species include Salix spp., Alnus incana, Betula occidentalis, Cornus sericea, and Crataegus spp. Exotic shrub species include Tamarix spp. and Elaeagnus angustifolia. Sites are most often associated with a stream channel, including ephemeral, intermittent, or perennial streams (Riverine HGM Class). This system can occur on slopes, lakeshores, or around ponds, where the vegetation is associated with groundwater discharge or a subsurface connection to lake or pond water, and may experience overland flow but no channel formation (Slope, Flat, Lacustrine, or Depressional HGM Classes). It is also typically found in backwater channels and other perennially wet but less scoured sites, such as floodplain swales and irrigation ditches.
Go to........................................Rocky Mountain Lower Montane-Foothill Riparian Woodland and Shrubland
6b. Riparian woodlands, shrublands and meadows of Colorado’s Western Great Plains. Dominant native species include Populus deltoides, Salix fragilis, Salix amygdaloides, Salix exigua, Acer negundo, Fraxinus spp., and Ulmus spp. Dominant non-native species include Tamarix spp., Elaeagnus angustifolia, and other introduced woody species.
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7a. Woodlands, shrublands, and meadows of draws and ravines associated with steep north-facing slopes or canyon bottoms that do not experience prolonged flooding. Common tree species include Acer negundo, Populus tremuloides, Fraxinus spp., and Ulmus spp. Important shrub species include Crataegus spp., Prunus virginiana, Rhus spp., Rosa woodsii, Symphoricarpos occidentalis, and Shepherdia argentea. [It is uncertain how common this type is in Colorado. This type is more common on the plains to the north and east of Colorado (Wyoming, Nebraska, and South Dakota), where there is more relief to the landscape.]
Go to........................................Rocky Mountain Lower Montane-Foothill Riparian Woodland and Shrubland
7b. Woodlands, shrublands, and meadows of small to large streams and rivers of the Western Great Plains. Overall vegetation is lusher than above and includes more wetland indicator species.
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8a. Riparian woodlands, shrublands, and meadows along medium and small rivers and streams. Sites have less floodplain development and flashier hydrology than the next, and all streamflow may drawdown completely for some portion of the year. Water sources include snowmelt runoff (streams close to the Rocky Mountain front), groundwater (prairie streams), and summer rainfall. Dominant species include Populus deltoides, Salix spp., Fraxinus pennsylvanica, Artemisia cana ssp. cana, Pascopyrum smithii, Panicum virgatum, Panicum obtusum, Sporobolus cryptandrus, and Schizachyrium scoparium. Carex spp., Tamarix spp., Elaeagnus angustifolia, and less desirable grasses and forbs can invade degraded examples. Groundwater depletion, lack of fire, heavy grazing, and/or agriculture have resulted in species and hydroperiod changes.
Go to........................................Western Great Plains Riparian
8b. Woodlands, shrublands, and meadows along large rivers with extensive floodplain development and periodic flooding that is more associated with snowmelt and seasonal dynamics in the mountains than with local precipitation events. Dominant communities within this system range from floodplain forests to wet meadow patches, to gravel/sand flats dominated by early successional herbs and annuals; however, they are linked by underlying soils and the flooding regime. Dominant species include Populus deltoides and Salix spp., Panicum virgatum, Andropogon gerardii, and Carex spp. Tamarix spp., Elaeagnus angustifolia, and non-native grasses have invaded degraded areas within the floodplains, which are subjected to heavy grazing and/or agriculture. Groundwater depletion and lack of fire have created additional alterations in species composition and hydroperiod. In most cases, the majority of the native wet meadow and prairie communities may be extremely degraded or extirpated from examples of this system.
Go to........................................Western Great Plains Floodplain

9a. Natural shallow depressional wetlands in the Western Great Plains with an impermeable soil layer, such as dense hardpan clay, that causes periodic ponding after heavy rains. Sites generally have closed contour topography and are surrounded by upland vegetation. Hydrology is typically tied to precipitation and runoff and lacks a groundwater connection. Ponding is often ephemeral and sites may be dry throughout the entire growing season during dry years. Species composition depends on soil salinity, may fluctuate depending on seasonal moisture availability, and many persistent species may be upland species. [On Colorado’s Eastern Plains, wetlands within this group are collectively referred to playas or playa lakes. Ecological systems listed below separate playas based on the level of salinity and total cover of vegetation.]
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9b. Herbaceous wetlands in the Western Great Plains not associated with hardpan clay soils. Sites may or may not be depressional and may or may not be natural.
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10a. Shallow depressional wetlands with less saline soils than the next. Dominant species are typically not salt-tolerant. Sites may have obvious vegetation zonation of tied to water levels, with the most hydrophytic species occurring in the wetland center where ponding lasts the longest. Common native species include Pascopyrum smithii, Buchloe dactyloides, Eleocharis spp., Oenothera canescens, Ratibida tagetes, Plantago spp., Polygonum spp., and Phyla cuneifolia. Non-native species are very common in these sites, including Salsola australis, Bassia sieversiana, Verbena bracteata, and Conyza canadensis. Sites have often been disturbed by agriculture and heavy grazing. Many have been dug out or “pitted” to increase water retention and to tap shallow groundwater. [Most of the playas on Colorado’s Eastern Plains will likely fit within this ecological system.]
Go to........................................Western Great Plains Closed Depression Wetland
10b. Shallow depressional herbaceous wetlands with saline soils. Salt encrustations can occur on the surface. Species are typically salt-tolerant, including Distichlis spicata, Puccinellia spp., Salicornia spp., Schoenoplectus maritimus. Sporobolus airoides, and Hordeum jubatum. Other commonly occurring taxa include Puccinellia nuttalliana, Salicornia rubra, Schoenoplectus maritimus, Schoenoplectus americanus, Suaeda calceoliformis, Spartina spp., Triglochin maritima, and occasional shrubs such as Sarcobatus vermiculatus and Krascheninnikovia lanata. [It is not clear how common this system is in Colorado. This system occurs more commonly in surrounding states where plains soils are more saline. Note: Low stature shrub-dominant wetlands key in the flats and wash systems above.]
Go to........................................Western Great Plains Saline Depression Wetland

11a. Herbaceous wetlands with standing water at or above the surface throughout the growing season, except in drought years. Water levels are often high at some point during the growing season, but managed systems may be drawn down at any point depending on water management regimes. Vegetation typically dominated by species of Typha, Scirpus, Schoenoplectus, Carex, Eleocharis, Juncus, and floating genera such as Potamogeton, Sagittaria, and Ceratophyllum. The isolated expression of this system can occur around ponds, as fringes around lakes, and at any impoundment of water, including irrigation run-off. The hydrology may be entirely managed or artificial. Water may be brackish or not. Soils are highly variable.
Go to........................................Western North American Emergent Marsh
11b. Herbaceous wetlands associated with a high water table that is controlled by artificial overland flow (irrigation) or artificial groundwater seepage (including from leaky irrigation ditches). Sites typically lack prolonged standing water. Vegetation is dominated by native or non-native herbaceous species; graminoids have the highest canopy cover. Species composition may be dominated by non-native hay grasses. Patches of emergent marsh vegetation and standing water are less than 0.1 ha in size and not the predominant vegetation.
Go to......................Irrigated Wet Meadow [Not an official Ecological System.]

Key B: Wetlands and Riparian Areas of the Inter-Mountain Basins

1a. Depressional, herbaceous wetlands occurring within dune fields of the inter-mountain basins (e.g., Great Sand Dunes National Park and Preserve, North Sand Hills Recreation Area in North Park).
Go to........................................Inter-Mountain Basins Interdunal Swale Wetland
1b. Wetlands not associated with dune fields.
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2a. Depressional wetlands. Soils are typically alkaline to saline clay with hardpans. Salt encrustation typically visible on the soil surface or along the water edge. Water levels various. Cover of vegetation variable, can be extremely sparse (<10% cover) or moderate to high (30–60% cover). Typically herbaceous dominated, but may contain salt-tolerant shrubs on the margins.
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2b. Non-depressional wetlands on flats or in washes, with alkaline to saline soils. Cover of vegetation variable, can be extremely sparse (<10% cover) or moderate to high (30–60% cover). Typically shrub dominated. Most common species are Sarcobatus vermiculatus and Atriplex spp.
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3a. Depressional, alkaline wetlands that are seasonally to semipermanently flooded, usually retaining water into the growing season and drying completely only in drought years. Many are associated with hot and cold springs, located in basins with internal drainage. Seasonal drying exposes mudflats colonized by annual wetland vegetation. Vegetation cover is generally >10% and species are typically salt-tolerant such as Distichlis spicata, Puccinellia spp., Leymus sp., Poa secunda, Schoenoplectus maritimus, Schoenoplectus americanus, Triglochin maritima, and Salicornia spp. This system can occur in alkaline basins and swales and along the drawdown zones of lakes and ponds.
Go to........................................Inter-Mountain Basins Alkaline Closed Depression
3b. Barren and sparsely vegetated playas (generally <10% plant cover). Salt crusts are common throughout, with small saltgrass beds in depressions and sparse shrubs around the margins. These systems are intermittently flooded. The water is prevented from percolating through the soil by an impermeable soil subhorizon and is left to evaporate. Soil salinity varies with soil moisture and greatly affects species composition. Characteristic species may include Sarcobatus vermiculatus, Distichlis spicata, and/or Atriplex spp.
Go to........................................Inter-Mountain Basins Playa

4a. Shrublands with >10% total vegetation cover, located on flats or in temporarily or intermittently flooded drainages. Vegetation dominated by Sarcobatus vermiculatus and Atriplex spp. with inclusions of Sporobolus airoides, Pascopyrum smithii, Distichlis spicata, Puccinellia nuttalliana, and Eleocharis palustris herbaceous vegetation.
Go to........................................Inter-Mountain Basins Greasewood Flat
4b. Sites with < 10% total vegetation cover and restricted to temporarily or intermittently flooded drainages with a variety of sparse or patchy vegetation including Sarcobatus vermiculatus, Ericameria nauseosa, Artemisia cana, Artemisia tridentata, Distichlis spicata, and Sporobolus airoides.
Go to........................................Inter-Mountain Basins Wash

Key C: Wetlands and Riparian Areas of the Rocky Mountains

1a. Herbaceous wetlands associated with seeps and springs within canyons of the Colorado Plateau region, typically along drainages of the major rivers of the region and their tributaries. Vegetation is supported by perennial water sources (seeps) that form pocketed wetlands and draping vegetation across wet cliff faces. Typical plant species include southern maidenhair fern (Adiantum capillus-veneris), northern maidenhair fern (Adiantum pedatum), Eastwood’s monkeyflower (Mimulus eastwoodiae), common large monkeyflower (Mimulus guttatus), Hapeman's coolwort (Sullivantia hapemanii), Rydberg’s thistle (Cirsium rydbergii), and several species of columbine, including Mancos columbine (Aquilegia micrantha).
Go to........................................Colorado Plateau Hanging Garden
1b. Wetlands not as above. Not associated with seeps and springs within canyons of the Colorado Plateau.
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2a. Wetland defined by groundwater inflows and organic soil (peat) accumulation of at least 40 cm in the upper 80 cm. Vegetation can be woody or herbaceous. If the wetland occurs within a mosaic of non-peat forming wetland or riparian systems, then the patch must be at least 0.1 hectares (0.25 acres). If the wetland occurs as an isolated patch surrounded by upland, then there is no minimum size criteria.
Go to........................................Rocky Mountain Subalpine-Montane Fen
2b. Wetland does not have at least 40 cm of organic soil (peat) accumulation or occupies an area less than 0.1 hectares (0.25 acres) within a mosaic of other non-peat forming wetland or riparian systems.
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3a. Total woody canopy cover generally 25% or more within the overall wetland/riparian area. Any purely herbaceous patches are less than 0.5 hectares and occur within a matrix of woody vegetation. [Note: Relictual woody vegetation such as standing dead trees and shrubs are included here.]
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3b. Total woody canopy cover generally less than 25% within the overall wetland/riparian area. Any woody vegetation patches are less than 0.5 hectares and occur within a matrix of herbaceous wetland vegetation.
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4a. Riparian woodlands and shrublands of the foothill and lower montane zones on both the east and west slopes of Colorado’s Rocky Mountains. Woodlands are dominated by Populus spp. (Populus angustifolia, P. deltoides, or the hybrid P. acuminata). Common native shrub species include Salix spp., Alnus incana, Betula occidentalis, Cornus sericea, and Crataegus spp. Exotic shrub species include Tamarix spp. and Elaeagnus angustifolia. Sites are most often associated with a stream channel, including ephemeral, intermittent, or perennial streams (Riverine HGM Class). This system can occur on slopes, lakeshores, or around ponds, where the vegetation is associated with groundwater discharge or a subsurface connection to lake or pond water, and may experience overland flow but no channel formation (Slope, Flat, Lacustrine, or Depressional HGM Classes). It is also typically found in backwater channels and other perennially wet but less scoured sites, such as floodplain swales and irrigation ditches.
Go to........................................Rocky Mountain Lower Montane-Foothill Riparian Woodland and Shrubland
4b. Riparian woodlands and shrublands of the montane or subalpine zone.
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5a. Montane or subalpine riparian woodlands (canopy dominated by trees). This system occurs as a narrow streamside forest lining small, confined low- to mid-order streams. Common tree species include Abies lasiocarpa, Picea engelmannii, Pseudotsuga menziesii, and Populus tremuloides.
Go to........................................Rocky Mountain Subalpine-Montane Riparian Woodland
5b. Montane or subalpine shrub wetlands (canopy dominated by shrubs with sparse or no tree cover). This system is most often associated with streams (Riverine HGM Class), occurring as either a narrow band of shrubs lining streambanks of steep V-shaped canyons or as a wide, extensive shrub stand on alluvial terraces in low-gradient valley bottoms (sometimes referred to as a shrub carr). Beaver activity is common within the wider occurrences. In addition, this system can occur around the edges of fens, lakes, seeps, and springs on slopes away from valley bottoms. This system can also occur within a mosaic of multiple shrub- and herb-dominated communities within snowmelt-fed basins. In all cases, vegetation is dominated by species of Salix, Alnus, or Betula.
Go to........................................Rocky Mountain Subalpine-Montane Riparian Shrubland

6a. Herbaceous wetlands with a permanent water source throughout all or most of the year. Water is at or above the surface throughout the growing season, except in drought years. This system can occur around ponds, as fringes around lakes and along slow-moving streams and rivers. The vegetation is dominated by common emergent and floating leaved species including species of Scirpus, Schoenoplectus, Typha, Juncus, Carex, Potamogeton, Polygonum, and Nuphar.
Go to........................................Western North American Emergent Marsh
6b. Herbaceous wetlands that typically lacks extensive standing water. Patches of emergent marsh vegetation and standing water are less than 0.1 ha in size and not the predominant vegetation.
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7a. Herbaceous wetlands associated with a high water table or overland flow, but typically lack standing water. Sites with no channel formation are typically associated with snowmelt or groundwater and not subjected to high disturbance events such as flooding (Slope HGM Class). Sites associated with a stream channel are more tightly connected to overbank flooding from the stream channel than with snowmelt and groundwater discharge and may be subjected to high disturbance events such as flooding (Riverine HGM Class). Vegetation is dominated by herbaceous species; typically graminoids have the highest canopy cover including Carex spp., Calamagrostis spp., and Deschampsia caespitosa.
Go to........................................Rocky Mountain Alpine-Montane Wet Meadow
7b. Large herbaceous wetlands associated with a high water table that is controlled by artificial overland flow (irrigation). Sites typically lack prolonged standing water, but may have standing water early in the season if water levels are very high. Vegetation is dominated by native or non-native herbaceous species; graminoids have the highest canopy cover. Species composition may be dominated by non-native hay grasses.
Go to..........................Irrigated Wet Meadow [Not an official Ecological System.]