Physiognomy and Structure: The vegetation structure of stands in this alliance vary from open woodlands to closed-canopy forests composed of needle-leaved evergreen trees typically less than 30 m in height. Associated trees are primarily needle-leaved evergreen species, but cold-deciduous and broad-leaved evergreen trees may be present in the subcanopy. The understory is dry, often shrubby, with either tall or short layers, and sclerophyllous or cold-deciduous species dominant. Where there is no shrub layer, grassy understories are common, but perennial forbs are important in some stands.

Floristics: This mesic forest and woodland alliance is primarily dominated by Pinus ponderosa but may include a sparse to relatively dense subcanopy of Juniperus scopulorum (Hansen and Hoffman 1988). Deciduous trees such as Acer negundo, Betula papyrifera, Crataegus succulenta, Fraxinus pennsylvanica, Populus tremuloides, Quercus macrocarpa, and Ulmus americana are an important component in some areas, especially mesic draws and swales, and are sometimes codominant with the pines (Hansen and Hoffman 1988). The shrub layer is moderately dense to dense with characteristic species that include Amelanchier alnifolia, Physocarpus monogynus, Prunus virginiana, Ribes missouriense, Rosa woodsii, Spiraea betulifolia, Symphoricarpos occidentalis, and Toxicodendron rydbergii. The herbaceous understory can range from moderately dense to dense. The diversity of species is moderate. Species such as Antennaria rosea, Apocynum androsaemifolium, Carex inops ssp. heliophila, Cerastium arvense, Elymus caninus, Galium boreale, Maianthemum stellatum, Pulsatilla patens, and Schizachne purpurascens are typical components of the herbaceous layer. Mosses and lichens are typically found in this community.

Dynamics:  Presettlement stands in the warm, moist Pinus ponderosa habitat types were often open and park-like. Surface fires kept stands in open condition by thinning out seedling and sapling trees. However, many modern stands have become overstocked as a result of fire suppression. These overstocked stands are more prone to stand-replacing crown fires (Fischer and Clayton 1983). Apparently Populus tremuloides may occasionally be a seral species (Roberts 1980). Populus tremuloides is often a component of stands in this alliance. Populus tremuloides abundance often increases in response to disturbance and clones will vigorously resprout (Knight 1994). The stems are relatively short-lived (100-150 years), and the stand will succeed to longer-lived conifer forest if undisturbed. 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). In the Dakotas and Wyoming, these stands may remain successionally stable for many dozens of years (Girard et al. 1989).