Common (Translated Scientific) Name: Fremont Cottonwood Great Basin Riparian Forest Alliance
Colloquial Name: Great Basin Fremont Cottonwood Riparian Forest
Hierarchy Level: Alliance
Type Concept: This alliance contains riparian woodlands dominated by Populus fremontii. Individuals of Populus fremontii are scattered or occur in groves and may reach 30 m in height and 2 m in diameter. Other species that may occur in the canopy/subcanopy include Baccharis salicifolia, Celtis laevigata var. reticulata, Fraxinus berlandieriana, Fraxinus velutina, Juglans microcarpa, Populus deltoides ssp. wislizeni, Prosopis glandulosa, Prosopis pubescens, Prosopis velutina, Salix amygdaloides, Salix exigua, Salix gooddingii, and Salix lasiolepis. The understory of most examples has been considerably altered by grazing and other factors, thus the composition and cover of the native understory are difficult to ascertain, but frequently consists of shrubs and small trees (1-5 m tall). The herbaceous stratum varies in composition and coverage but is characterized by mixed annuals and short-lived perennials. Some areas have high amounts of Tamarix spp. and other exotic invasive trees. This woodland alliance occurs as small isolated stands or as linear bands that parallel stream channels on alluvial fans, in lower canyons in desert mountains, and valleys with dependable subsurface groundwater that varies considerably during the year. In the southwestern U.S., it occurs in western New Mexico, throughout Arizona, lower elevations of Utah, southern and central Nevada and just into the eastern desert of California.
Diagnostic Characteristics: Populus fremontii has >30% relative cover.
Rationale for Nominal Species or Physiognomic Features:
Classification Comments: No Data Available
Similar NVC Types:
Physiognomy and Structure: The tree stratum is dominated by a tall (10-25 to 30 m) broad-leaved deciduous tree. The canopy is open to dense (25-60%) depending on the stand. The tree subcanopy is dominated by multi-stemmed, broad-leaved shrubs. The herbaceous layer is sparse and often dominated by introduced hay grasses.
Floristics: The canopy is dominated by open stands of Populus fremontii generally forming 30-70% cover; individuals may be scattered or occur in groves. This species may reach 30 m in height and 2 m in diameter. Other woody species that may occur in the canopy/subcanopy include Baccharis salicifolia, Celtis laevigata var. reticulata, Fraxinus berlandieriana, Fraxinus velutina, Juglans microcarpa, Populus deltoides ssp. wislizeni, Prosopis glandulosa, Prosopis pubescens, Prosopis velutina, Salix amygdaloides, Salix exigua, Salix gooddingii, and Salix lasiolepis. The understories of most examples have been considerably altered by grazing and other factors, thus the composition and cover of the native understory is difficult to ascertain, but frequently consists of shrubs and small trees (1-5 m tall) of the above species. The herbaceous stratum varies in composition and coverage, but is characterized by mixed annuals and short-lived perennials.
Dynamics: This alliance is dependent on a subsurface water supply and varies considerably with the water table levels. Major flood events and consequent flood scour, overbank deposition of water and sediments, and stream meandering are important factors that shape these woodlands.
Environmental Description: This riparian alliance is found in floodplains and on lower alluvial terraces along the perennial streams that occur in the southern deserts. Elevations range from 335-2500 m. Stands are restricted to the floodplains and corridors of perennial streams by the arid upland environment. This vegetation type is dependent on a subsurface water supply and varies considerably with the water table levels. Major flood events and consequent flood scour, overbank deposition of water and sediments, and stream meandering are important factors that shape these woodlands. These woodlands occur as small isolated stands or as linear bands that parallel stream channels. Sites are flat to gently sloping and occur in lower canyons in desert mountains, alluvial fans and valleys. Substrates are generally well-drained, coarse-textured soils derived from stratified alluvium composed of sand, loam, gravel and cobbles. The soils may be slightly alkaline and saline. Climate is arid to semi-arid with hot summers and typically mild winters, but with freezing temperatures not uncommon in northern stands. Mean annual precipitation ranges from 15-28 cm, but can vary greatly from year to year. Drought is not uncommon.
Geographic Range: This alliance is found in southeastern California, southern and central Nevada, Utah, Arizona and New Mexico.
States/Provinces: AZ, CA, NM, NV, UT
|US Forest Service Ecoregions (1994/1995)|
Confidence Level: Low
Confidence Level Comments:
Concept Lineage: [check A.644 for edits]
Synonomy: >< Populus fremontii (Fremont cottonwood forest) Alliance (Sawyer et al. 2009) [61.130.00]
? Populus fremontii Alliance (Fremont cottonwood forest) (Buck-Diaz et al. 2012)
? Broadleaf Cottonwood-Mixed Deciduous Series (Dick-Peddie 1993) [included in the Montane Riparian Vegetation Type.]
>< Central Coast Cottonwood-Sycamore Riparian Forest (#61210) (Holland 1986b)
>< Cottonwood - Willow: 235 (Eyre 1980)
? Cottonwood Series (Dick-Peddie 1993) [included in the Floodplain Riparian Vegetation Type.]
? Cottonwood-Willow Series (Dick-Peddie 1993) [included in the Floodplain Riparian Vegetation Type.]
? Cottonwood-Willow Series (224.53) (Brown 1982a) [included within Sonoran Riparian and Oasis Forests]
>< Fremont Cottonwood series (Sawyer and Keeler-Wolf 1995)
>< Great Valley Cottonwood Riparian Forest (#61410) (Holland 1986b)
>< Great Valley Mixed Riparian Forest (#61420) (Holland 1986b)
>< IIA7d. Western Cottonwood - Willow Riverfront Forest (Allard 1990)
>< Modoc-Great Basin Cottonwood-Willow Riparian Forest (#61610) (Holland 1986b)
>< Mojave Riparian Forest (#61700) (Holland 1986b)
>< Sonoran Cottonwood-Willow Riparian Forest (#61810) (Holland 1986b)
>< Southern Cottonwood-Willow Riparian Forest (#61330) (Holland 1986b)
Concept Author(s): K.D. Patterson, D. Culver, G. Kittel, J. Evens, in Faber-Langendoen et al. (2013)
Author of Description: G. Kittel
Version Date: 26Sep2014
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