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A0636 Populus deltoides Floodplain Woodland Alliance

Type Concept Sentence: This alliance occurs near rivers and large streams throughout the Great Plains of the U.S. and Canada and extends west into Wyoming and New Mexico. It is dominated by Populus deltoides throughout its range. Secondary canopy species include Acer negundo throughout, Salix nigra (in the eastern part of its range), Fraxinus pennsylvanica and Ulmus americana (central and eastern), and Salix amygdaloides (central and western). The understory composition and structure are variable.

Common (Translated Scientific) Name: Eastern Cottonwood Floodplain Woodland Alliance

Colloquial Name: Eastern Cottonwood Floodplain Woodland

Hierarchy Level:  Alliance

Type Concept: This alliance occurs near rivers and large streams throughout the Great Plains and extends west into Wyoming and New Mexico. It is dominated by Populus deltoides throughout its range. Secondary canopy species include Acer negundo throughout, Salix nigra (in the eastern part of its range), Fraxinus pennsylvanica and Ulmus americana (central and eastern), and Salix amygdaloides (central and western). Fraxinus pennsylvanica and Ulmus americana often increase in abundance and dominance as stands of this alliance age. Populus deltoides does not reproduce well in established stands. The understory composition and structure are variable. A shrub layer may be present, with species such as Salix spp., Symphoricarpos occidentalis, and Prunus virginiana predominating. Sites experience seasonal floods, which, after receding, leave areas available for colonization. This process often favors the establishment of aggressive native and exotic plants. Among the species that are common in this alliance are Carex spp., Juncus spp., Spartina pectinata (in the east), Pascopyrum smithii (in the west), Elymus spp., Cenchrus longispinus, Melilotus officinalis, and Equisetum spp. Typical exotics found in this alliance are Poa pratensis and Bromus spp. Stands of this alliance are found on level to gently sloping topography near rivers, streams, lakes, and ponds. The areas may have been very recently deposited by water action, or they may have been deposited earlier and occupied by other communities. The water table fluctuates with the level of the adjacent waterbody. This can lead to periods of flooding and soil saturation in the spring and after heavy rains and also to periods of drought when the water level falls in the summer and fall. The soils are silts, loams, and sands, and are derived from alluvial material.

Diagnostic Characteristics: Woodland floodplains in the Great Plains, nearly always dominated by Populus deltoides. The understory often has mid- and tallgrass components from the surrounding prairie, though recently scoured sites can be barren or dominated by early-successional species.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: This alliance is similar to ~Populus deltoides Floodplain Forest Alliance (A3423)$$. The canopy tends to be more open in this alliance and the understory may have more mid- and tallgrass species but strong differential or characteristic species are not known at this time.

Should this alliance be split into a northern and southern alliance? Given the dominance of Populus deltoides throughout the range, there are no consistent canopy species to make the split. There may be a suite of overstory and understory species that could serve to differentiate the two new alliances (Platanus occidentalis, Celtis laevigata, Sapindus saponaria for the south and yet-to-be-determined species for the north) but the difference does not seem strong.

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: The tree layer is dominated by tall (20-35 m) single-stemmed, deciduous species. The canopy is open, generally forming 25-60% cover. The herbaceous layer is dominated by both graminoids and forbs with up to 20% cover. In parts of this alliance''s range, graminoid cover is primarily from introduced grass species.

Floristics: This alliance is dominated by Populus deltoides (either ssp. wislizeni or ssp. monilifera and perhaps ssp. deltoides in eastern extent) throughout its range. Secondary canopy species include Acer negundo throughout, Salix nigra (in the eastern part of its range), Fraxinus pennsylvanica and Ulmus americana (central and eastern), and Salix amygdaloides (central and western). Fraxinus pennsylvanica and Ulmus americana often increase in abundance and dominance as stands of this alliance age (Johnson et al. 1976). Populus deltoides does not reproduce well in established stands. The understory composition and structure are variable. A shrub layer may be present, with species such as Salix spp., Symphoricarpos occidentalis, and Prunus virginiana predominating. Sites experience seasonal floods which, after receding, leave areas available for colonization. This process often favors the establishment of aggressive native and exotic plants. Among the species that are common in this alliance are Carex spp., Juncus spp., Spartina pectinata (in the east), Pascopyrum smithii (in the west), Elymus spp., Cenchrus longispinus, Melilotus officinalis, and Equisetum spp. Typical exotics found in this alliance are Poa pratensis and Bromus spp.

Dynamics:  Cottonwood forests grow within an alluvial environment that is continually changing due to the ebb and flow of the river. Riparian vegetation is constantly being "re-set" by flooding disturbance. Cottonwood communities are early-, mid- or late-seral, depending on the age class of the trees and the associated species of the stand. Mature cottonwood stands do not regenerate in place, but regenerate by "moving" up and down a river reach. Over time, a healthy riparian area supports all stages of cottonwood communities. The process of cottonwood regeneration is well-documented. Periodic flooding events can leave sandbars of bare, mineral substrate. Cottonwood seedlings germinate and become established on newly-deposited, moist sandbars. In the absence of large floods in subsequent years, seedlings begin to trap sediment. In time, the sediment accumulates and the sandbar rises. The young forest community is then above the annual flood zone of the river channel. In this newly elevated position, with an absence of excessive browsing, fire, or agricultural conversion, this cottonwood community can grow into a mature riparian forest. At the same time, the river channel continually erodes streambanks and creates fresh, new surfaces for cottonwood establishment. This results in a dynamic patchwork of different age classes, plant associations and habitats. As cottonwoods mature, other tree species may become established. If the land surface is subject to reworking by the river, the successional processes will start over with erosion and subsequent flooding deposition. If the land surface is not subject to alluvial processes, for example on a high terrace, the cottonwoods will be replaced by upland shrub or tree species from adjacent areas.
Environmental Description:  Stands of this alliance are found on level to gently sloping topography near rivers, streams, lakes, and ponds throughout the Great Plains, extending west into Wyoming and New Mexico to the western slope of Colorado and extending into mountain valleys and on to Colorado Plateau. The areas may have been very recently deposited by water action or they may have been deposited earlier and occupied by other communities (Wilson 1970). The water table fluctuates with the level of the adjacent waterbody. This can lead to periods of flooding and soil saturation in the spring and after heavy rains and also to periods of drought when the water level falls in the summer and fall. The soils are silts, loams, and sands, and are derived from alluvial material (Wilson 1970, Hansen et al. 1984, Thilenius et al. 1995).
Geographic Range: This alliance is found in the Great Plains from southern Alberta and Saskatchewan and southwestern Manitoba, through the Dakotas and Montana south to the Texas Panhandle, Oklahoma, and northeastern New Mexico. This alliance probably extends east along the Missouri River and major tributaries into western Iowa and western Missouri.

Nations: CA,US

States/Provinces:  AB, CO, KS, MB, MO?, MT, ND, NE, NM, OK, SD, SK?, TX, WY


Confidence Level: Moderate

Confidence Level Comments: No Data Available
Grank: GNR

Greasons: No Data Available
Type Name Database Code Classification Code
Class 1 Forest & Woodland Class C01 1
Subclass 1.B Temperate & Boreal Forest & Woodland Subclass S15 1.B
Formation 1.B.3 Temperate Flooded & Swamp Forest Formation F026 1.B.3
Division 1.B.3.Na Eastern North American-Great Plains Flooded & Swamp Forest Division D011 1.B.3.Na
Macrogroup 1.B.3.Na.4 Eastern Cottonwood - Green Ash / Willow species Flooded & Swamp Forest M028 1.B.3.Na.4
Group 1.B.3.Na.4.a Eastern Cottonwood - Green Ash / Western Wheatgrass Floodplain Forest Group G147 1.B.3.Na.4.a
Alliance A0636 Eastern Cottonwood Floodplain Woodland Alliance A0636 1.B.3.Na.4.a
Association CEGL000659 Eastern Cottonwood - (Peachleaf Willow) / (Narrowleaf Willow, Sandbar Willow) Floodplain Woodland CEGL000659 1.B.3.Na.4.a
Association CEGL000660 Eastern Cottonwood / Western Snowberry Floodplain Woodland CEGL000660 1.B.3.Na.4.a
Association CEGL001454 Eastern Cottonwood / Switchgrass - Little Bluestem Floodplain Woodland CEGL001454 1.B.3.Na.4.a
Association CEGL002017 Eastern Cottonwood - (Black Willow) / Prairie Cordgrass - Sedge species Floodplain Woodland CEGL002017 1.B.3.Na.4.a
Association CEGL002152 Eastern Cottonwood / Rocky Mountain Juniper Floodplain Woodland CEGL002152 1.B.3.Na.4.a
Association CEGL002649 Eastern Cottonwood / Woolly Sedge Floodplain Woodland CEGL002649 1.B.3.Na.4.a
Association CEGL004919 Eastern Cottonwood / Black Willow Floodplain Woodland CEGL004919 1.B.3.Na.4.a
Association CEGL005024 Eastern Cottonwood / Western Wheatgrass - Switchgrass Floodplain Woodland CEGL005024 1.B.3.Na.4.a
Association CEGL005025 Eastern Cottonwood - Sugarberry / Wingleaf Soapberry Floodplain Woodland CEGL005025 1.B.3.Na.4.a
Concept Lineage: This alliance equals the Great Plains portion of old alliance A.636.

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: ? Populus deltoides woodland alliance (Hoagland 1998a)
>< Cottonwood: 63 (Eyre 1980)
>< Eastern Broadleaf Forests: 98: Northern Floodplain Forest (Populus-Salix-Ulmus) (Küchler 1964)
Concept Author(s): D. Culver and K.A. Schulz, in Faber-Langendoen et al. (2013)

Author of Description: J. Drake

Acknowledgements: No Data Available

Version Date: 06-30-17
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