Physiognomy and Structure: This upland shrubland is typically dominated by a moderate to dense evergreen sclerophyllous (sometimes including winter deciduous) shrub canopy usually less than 3 m tall. Herbaceous layers may be present and are typically dominated by perennial graminoids.

Floristics: In California and the Oregon Cascades, these shrublands are typically dominated by evergreen sclerophyllous shrubs. Characteristic shrub species include Ceanothus cordulatus, Ceanothus diversifolius, Ceanothus integerrimus, Ceanothus velutinus, Ceanothus pinetorum, Chrysolepis sempervirens (= Castanopsis sempervirens), Notholithocarpus densiflorus var. echinoides (= Lithocarpus densiflorus var. echinoides), Quercus sadleriana, and Quercus vacciniifolia. Other evergreen species, such as Arctostaphylos nevadensis, Arctostaphylos patula, Arctostaphylos manzanita, and Garrya fremontii, are common in some stands. Characteristic winter-deciduous shrubs might dominate some stands, but are commonly present even where not dominant. They include Prunus emarginata, Prunus subcordata, and Ceanothus sanguineus (in Oregon), Prunus virginiana, Holodiscus discolor (= Holodiscus microphyllus), and Quercus garryana garryana var. fruticosa (= var. breweri). Other shrub species include Amelanchier alnifolia, Symphoricarpos mollis, Chamaebatia foliolosa, and Cercocarpus spp. Emergent Abies concolor, Pinus lambertiana, Pinus jeffreyi, Pinus sabiniana, Pinus ponderosa, Pseudotsuga menziesii, Quercus chrysolepis, Quercus wislizeni, and Quercus kelloggii trees may be present at sparse cover. The herbaceous layer is variable depending on cover of shrubs (dense shrublands have little understory) and substrate.

Further east, in the Great Basin, Colorado Plateau and Rocky Mountains, the diversity of shrubs tends to be less, but some species are shared with California montane chaparral. Characteristic shrubs include Arctostaphylos patula, Arctostaphylos nevadensis, Ceanothus velutinus, Ceanothus martinii, Ceanothus prostratus, and Purshia stansburiana. Other winter-deciduous shrubs are often present, including Amelanchier alnifolia, Artemisia tridentata, Eriogonum spp., Prunus virginiana, and Symphoricarpos spp. Emergent Abies concolor, Juniperus osteosperma, Juniperus scopulorum, Pinus edulis, Pinus flexilis, Pinus monophylla, Pinus ponderosa, Pseudotsuga menziesii trees may be present at sparse cover. The herbaceous layer is variable depending on cover of shrubs (dense shrublands have little understory) and substrate, but will include a variety of grass and forb taxa common to the Intermountain West and montane zones of the Rocky Mountains.

Further south, a moderate to dense evergreen shrub layer is dominated by the scrub oaks (Quercus turbinella, Quercus intricata, and Quercus toumeyi) along with wide diversity of other sclerophyllous shrubs that include Ceanothus greggii, Cercocarpus montanus var. paucidentatus, Garrya wrightii, and Rhus trilobata, with Arctostaphylos pringlei and Arctostaphylos pungens at higher elevations. In desert chaparral stands in the western extent, Arctostaphylos glauca, Arctostaphylos patula, Cercocarpus montanus var. glaber, Garrya flavescens, Juniperus californica, and Nolina parryi, Quercus cornelius-mulleri, Rhamnus ilicifolia, and Rhus ovata, characterize this shrubland. Scattered remnant pinyon and juniper trees may be present; however, in the western Mojave Desert, Juniperus californica sometimes forms an open, shrubby tree layer over the evergreen oaks and other shrubs. In the eastern extent, stands in the Chihuahuan Desert mountains and the Sierra Madre Oriental are dominated by evergreen shrub oak species, such as Quercus mohriana, Quercus pungens, and Quercus vaseyana, and several widespread chaparral species, such as Arctostaphylos pungens, Ceanothus greggii, Cercocarpus montanus, Eriodictyon angustifolium, Fallugia paradoxa, Garrya wrightii, and Quercus grisea. Other Madrean Orientale species include Arbutus xalapensis (= Arbutus texana), Fraxinus greggii, Fendlera rigida (= Fendlera linearis), Garrya ovata, Juniperus pinchotii, Purshia mexicana, Rhus virens var. choriophylla (= Rhus choriophylla), Salvia lycioides (= Salvia ramosissima), Salvia roemeriana, Salvia regla (Brown 1982a), and Viguiera stenoloba. The herbaceous layer is variable, but is generally composed of perennial grasses, such as Achnatherum speciosum, Bouteloua curtipendula, Bouteloua hirsuta, Bothriochloa barbinodis, Eragrostis intermedia, Lycurus phleoides, Muhlenbergia emersleyi, and several species of Aristida, which are largely restricted to rocky, protected areas because of past heavy livestock grazing. In rocky settings, pteridophytes (e.g., Astrolepis spp., Cheilanthes spp., Notholaena standleyi, Selaginella spp.) are often a component of this layer, and their abundance may exceed that of forbs.

Dynamics:  Most of these chaparral species are fire-adapted, resprouting vigorously after burning or producing fire-resistant seeds. Some types within this division, especially those found among cold-temperate montane forests, may be short-duration chaparrals in previously forested areas that have experienced crown fires or recent logging. These chaparral patches likely shift across montane forested landscapes with catastrophic fire events. Chaparral found within the context of cold and warm deserts are likely to be far more persistent.