Physiognomy and Structure: Vegetation included in this alliance has a moderately dense to dense tree canopy dominated by cold-deciduous broad-leaved trees (5-20 m tall). Evergreen needle-leaved trees may be present, but do not codominate the tree canopy. The understory is variable. Sparse to dense, tall- and short-shrub layers may be present and are typically dominated by deciduous broad-leaved species; however, a scale-leaved short shrub dominates the understory of some stands. Sparse to dense tall or short herbaceous layers may also be present and may be dominated by perennial forbs or graminoids.

Floristics: Populus tremuloides is typically the sole dominant canopy tree, and stands may have open to closed cover. Other canopy associates may include Abies lasiocarpa, Picea engelmannii, Populus angustifolia, Populus balsamifera, and Pseudotsuga menziesii. Common shrubs include Acer glabrum, Amelanchier alnifolia, Artemisia tridentata, Juniperus communis, Mahonia repens, Prunus virginiana, Rosa woodsii, Shepherdia canadensis, Symphoricarpos oreophilus, and Vaccinium myrtillus. The herbaceous layer may be lush and diverse. Common graminoids may include Bromus carinatus, Calamagrostis rubescens, Carex siccata (= Carex foenea), Carex geyeri, Carex rossii, Elymus glaucus, Elymus trachycaulus, Festuca thurberi, and Hesperostipa comata (= Stipa comata). Associated forbs may include Achillea millefolium, Eucephalus engelmannii (= Aster engelmannii), Delphinium x occidentale, Geranium viscosissimum, Heracleum sphondylium, Ligusticum filicinum, Lupinus argenteus, Osmorhiza berteroi (= Osmorhiza chilensis), Pteridium aquilinum, Rudbeckia occidentalis, Thalictrum fendleri, Valeriana occidentalis, Wyethia amplexicaulis, and many others. Exotic grasses, such as the perennial Poa pratensis and the annual Bromus tectorum, are often common in stands disturbed by grazing.

Dynamics:  Stands in this alliance often originate and are likely maintained by stand-replacing disturbances such as crown fire, disease and windthrow, or cutting by man or beaver. The stems of these thin-barked, clonal trees are easily killed by surface fires, but they can quickly and vigorously resprout in densities of up to 30,000 stems per hectare (Knight 1993). The stems are relatively short-lived (100-150 years), and the stand will succeed to longer-lived conifer forest if undisturbed. Stands are favored by fire in the conifer zone (Mueggler 1988). With adequate disturbance a clone may live many centuries. Although Populus tremuloides produces abundant seeds, seedling survival is rare because of the long moist conditions required to establish are rare in the habitats that it occurs in. Superficial soil drying will kill seedlings (Knight 1994).