Physiognomy and Structure: No Data Available

Floristics: Because stands of this association are isolated from flood events and from the water table, the canopy generally consists of mature to decadent gallery stands of Populus deltoides ssp. wislizeni with no saplings or seedlings present. Canopy closure ranges between 10 and 40%. Other trees present in the canopy or subcanopy may include individuals or clumps of Acer negundo, Juniperus scopulorum, or exotic species Elaeagnus angustifolia and Tamarix ramosissima. The understory is composed primarily of upland plants, although relict riparian species such as Salix exigua or Juncus arcticus ssp. littoralis (= Juncus balticus) may be present. Herbaceous species, especially invasive exotics, dominate the understory; the exotic grasses Bromus tectorum, Bromus diandrus ssp. rigidus (= Bromus rigidus), Poa pratensis, or Elymus repens (or a hybrid of Pascopyrum smithii and Elymus repens) can contribute up to 65% cover. Other stands have high cover of the exotic forbs Lepidium latifolium, Acroptilon repens (= Centaurea repens), or Sisymbrium altissimum. Relict native species may occur scattered throughout stands, including Hesperostipa comata, Sporobolus cryptandrus, Iva axillaris, and Heterotheca villosa. Shrubs such as Artemisia tridentata ssp. tridentata and Ericameria nauseosa are often present, although they do not contribute enough cover (less than 5%) to constitute a stratum.

Dynamics:  This association represents a degraded successional endpoint for low- and middle-elevation Colorado Plateau riparian woodlands. Because stands are isolated from floods, scouring and sediment deposition, the cottonwood canopy is not reproducing. Because they are generally isolated from the water table, riparian shrubs and herbaceous species have been replaced by upland species. Because of their shade, easily accessible forage and proximity to perennial streams, these stands supported heavy domestic livestock grazing for decades. This use removed most of the native understory, allowing aggressive exotic grasses and forbs to take over. In a few stands, pasture grasses were planted for forage. Along relatively free-flowing rivers, the process of lateral channel migration eventually will remove these terraces.