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CEGL000940 Populus deltoides ssp. wislizeni / Rhus trilobata Riparian Woodland

The U.S. National
Vegetation Classification
Type Concept Sentence:
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Common (Translated Scientific) Name: Rio Grande Cottonwood / Skunkbush Sumac Riparian Woodland
Colloquial Name:
Hierarchy Level: Association
Type Concept: This woodland association is documented from the Colorado, Yampa and San Miguel/Dolores river basins in western Colorado and northeastern Utah below 1680 m (5500 feet) in elevation. An ecologically similar association with a different subspecies of cottonwood, Populus deltoides ssp. monilifera, is known from southeastern Colorado. Both of these associations represent a late-seral stage of maturing cottonwoods. The trees are usually large and widely spaced with thick patches of Rhus trilobata in between and underneath the overstory canopy. Populus deltoides ssp. wislizeni with a Rhus trilobata understory form this late-seral plant association. Populus angustifolia becomes an important overstory component at higher elevations in the Colorado River basin. Other shrubs commonly present are Artemisia tridentata ssp. tridentata, Cornus sericea, Chrysothamnus linifolius, Symphoricarpos spp., Shepherdia argentea, Tamarix ramosissima (an exotic), and Salix exigua. The forb understory is usually sparse and consists mainly of Cirsium arvense (an exotic), Asclepias speciosa, and Melilotus officinalis (another exotic). Graminoid cover ranges from 10-30% and consists mostly of introduced species such as Poa pratensis, Bromus inermis, and Elymus repens.
Diagnostic Characteristics: No Data Available
Rationale for Nominal Species or Physiognomic Features:
Classification Comments: No Data Available
Similar NVC Types:
Physiognomy and Structure: No Data Available
Floristics: This association is dominated by broad-leaved deciduous species, both in the tree canopy and shrub layer. Populus deltoides ssp. wislizeni dominates the canopy, with cover varying from 15% to over 50%. Older, more mature stands will be characterized by a few large (up to 1 m dbh) trees with less canopy cover but large basal areas. Other trees occasionally present include Populus angustifolia and Populus x acuminata. The understory has a shrub layer also of varying cover but characterized by the presence of Rhus trilobata. Density and cover of shrubs, including Rhus, are related to the degree of livestock grazing, the age of the stand, and the density of the tree canopy. Middle-aged stands have dense Rhus cover, while in older stands individual shrubs are widely spaced. Other shrubs commonly present include Artemisia tridentata ssp. tridentata, Chrysothamnus linifolius, Forestiera pubescens, Rosa woodsii, and Symphoricarpos occidentalis, and the woody liana Clematis ligusticifolia. The herbaceous layer is generally sparse to moderately so, with an average cover less than 30%. Species composition varies somewhat, and many stands have abundant introduced grass species. Graminoids present in relatively undisturbed stands may include Juncus arcticus ssp. littoralis (= Juncus balticus), Carex nebrascensis, Eleocharis palustris, Distichlis spicata, Elymus trachycaulus, and Hordeum jubatum. Forbs are sparse. Most (and maybe all) stands of this association have been severely impacted by livestock use and can have abundant introduced herbaceous species, particularly the grasses Elymus repens (= Elytrigia repens), Bromus inermis, and Poa pratensis, and the forb Melilotus officinalis. The low shrub Symphoricarpos occidentalis may be abundant in undisturbed stands.
Dynamics: No Data Available
Environmental Description: This type is found along moderately large, snow-fed rivers on the west slope of Colorado and adjacent Utah, from roughly 1370 to 1720 m (4500-5640 feet) elevation. Climate is continental, with hot summers and cold winters. Precipitation is less than 38.1 cm (15 inches) annually. Sites where this association occurs vary from point bars and other depositional features (early-seral stands) to alluvial terraces (mature stands) that may be many meters away from the main channel and several meters above the high-water mark. It also occurs in depressions associated with upland springs. Mature cottonwoods are able to tap deeper water tables than seedlings. Soils are derived from alluvium and are deep, stratified sandy loams with cobbles. Point bars within the channels are composed of fresh alluvial sands and gravels.
Geographic Range: This woodland association is documented from the Colorado, Yampa, and San Miguel/Dolores river basins in western Colorado and adjacent Utah.
Nations: US
States/Provinces: CO, UT
US Forest Service Ecoregions (1994/1995)
Domain Name:
Division Name:
Province Name: Southern Rocky Mountain Steppe - Open Woodland - Coniferous Forest - Alpine Meadow Province
Province Code: M331    Occurrence Status: Confident or certain
Section Name: Uinta Mountains Section
Section Code: M331E     Occurrence Status: Confident or certain
US Forest Service Ecoregions (2007)
Domain Name:
Division Name:
Province Name: Southern Rocky Mountain Steppe - Open Woodland - Coniferous Forest - Alpine Meadow Province
Province Code: M331    Occurrence Status: Confident or certain
Section Name: Uinta Mountains Section
Section Code: M331E     Occurrence Status: Confident or certain
Omernik Ecoregions:
Confidence Level: Moderate
Confidence Level Comments:
Grank: G3
Greasons: This association has only been documented from river floodplains of the lower Colorado, Yampa, and San Miguel rivers in extreme western Colorado (Keammerer 1974a, 1974b, Kittel and Lederer 1993). It has also been tentatively reported to occur in degraded stands along the Rio Grande in northern New Mexico. Nearly all the existing stands are considered to be in decline due to altered hydrology from upstream impoundments and the long-term effects of livestock grazing. Populus regeneration is poor at all sites, and tamarisk (Tamarix ramosissima) is invading stands of this type on the lower Colorado River near Grand Junction, Colorado.
Concept Lineage:
Obsolete Names:
Obsolete Parents:
Synonomy: = Populus deltoides / Rhus trilobata Woodland (Carsey et al. 2003a)
Concept Author(s): M.S. Reid
Author of Description: M.S. Reid and J. Coles
Version Date: 07Sep2005
  • Bourgeron, P. S., and L. D. Engelking, editors. 1994. A preliminary vegetation classification of the western United States. Unpublished report. The Nature Conservancy, Western Heritage Task Force, Boulder, CO. 175 pp. plus appendix.
  • Carsey, K., G. Kittel, K. Decker, D. J. Cooper, and D. Culver. 2003a. Field guide to the wetland and riparian plant associations of Colorado. Colorado Natural Heritage Program, Fort Collins, CO.
  • CNHP [Colorado Natural Heritage Program]. 2006-2017. Tracked natural plant communities. Colorado Natural Heritage Program, Colorado State University, Fort Collins. []
  • Coles, J., D. Cogan, D. Salas, A. Wight, G. Wakefield, J. Von Loh, and A. Evenden. 2008a. Vegetation classification and mapping project report, Dinosaur National Monument. Natural Resource Technical Report NPS/NCPN/NRTR-2008/112. National Park Service, Fort Collins, CO. 814 pp.
  • Keammerer, W. R. 1974a. Vegetation of the Grand Valley area. Pages 73-117 in: Ecological inventory of the Grand Valley area Unpublished report prepared for the Colony Development Operation, Atlantic Richfield Company, Denver, CO.
  • Keammerer, W. R. 1974b. Vegetation of Parachute Creek Valley. Pages 4-91 in: Environmental inventory and impact analysis of a proposed utilities corridor in Parachute Creek Valley, Co. Unpublished report prepared for Colony Development Operation, Denver, CO.
  • Kittel, G. M., and N. D. Lederer. 1993. A preliminary classification of the riparian vegetation of the Yampa and San Miguel/Dolores river basins. Unpublished report prepared for Colorado Department of Health and the Environmental Protection Agency by The Nature Conservancy, Colorado Field Office, Boulder.
  • Kittel, G., E. Van Wie, M. Damm, R. Rondeau, S. Kettler, and J. Sanderson. 1999a. A classification of the riparian plant associations of the Rio Grande and Closed Basin watersheds, Colorado. Unpublished report prepared by the Colorado Natural Heritage Program, Colorado State University, Fort Collins.
  • Reid, M. 1990. Yampa River Basin riparian vegetation classification project. Unpublished data prepared for The Nature Conservancy, Colorado Field Office and Western Heritage Task Force, Boulder, CO.
  • USBOR [U.S. Bureau of Reclamation]. 1976. Flora and terrestrial vertebrate studies of the Grand Valley, Colorado. Pages 56-85 and 283-354 in: Final report to the U.S. Bureau of Reclamation by Ecology Consultants, Inc., Fort Collins, CO.
  • Western Ecology Working Group of NatureServe. No date. International Ecological Classification Standard: International Vegetation Classification. Terrestrial Vegetation. NatureServe, Boulder, CO.