Arizona Plateau Chaparral

This ecological system occurs across central Arizona (Mogollon Rim), western New Mexico, and southern Utah and Nevada. It often dominates along the mid-elevation transition from the Mojave, Sonoran, and northern Chihuahuan deserts into mountains (1000-2200 m). It occurs on foothills, mountain slopes and canyons in hotter and drier habitats below the encinal and Pinus ponderosa woodlands. Stands are often associated with more xeric and coarse-textured substrates such as limestone, basalt or alluvium, especially in transition areas with more mesic woodlands. The moderate to dense shrub canopy includes species such as Quercus turbinella, Quercus toumeyi, Cercocarpus montanus var. paucidentatus, Canotia holacantha, Ceanothus greggii, Garrya wrightii, Purshia stansburiana, Rhus ovata, Rhus trilobata, and Arctostaphylos pungens and Arctostaphylos pringlei at higher elevations. Scattered remnant pinyon and juniper trees may be present. Most chaparral species are fire-adapted, resprouting vigorously after burning or producing fire-resistant seeds. Stands occurring within montane woodlands are seral and a result of recent fires.

The vegetation is characterized by a moderate to dense, evergreen-dominated shrub canopy with Quercus turbinella or Quercus toumeyi often dominant or codominant. Other shrubs that may be present to dominant include Cercocarpus montanus, Canotia holacantha, Ceanothus greggii, Forestiera pubescens (= Forestiera neomexicana), Garrya flavescens, Garrya wrightii, Purshia stansburiana, Rhus ovata, Rhus trilobata, Arctostaphylos pungens, and at higher elevations Arctostaphylos pringlei. Scattered remnant pinyon and juniper trees may be present, especially Pinus edulis, Juniperus deppeana, Juniperus monosperma, and Juniperus osteosperma (Carmichael et al. 1978). The herbaceous understory is variable depending on density of the shrub layer, but is usually low and dominated by perennial graminoids such as Aristida purpurea var. fendleriana (= Aristida fendleriana), Aristida ternipes, Bouteloua curtipendula, Bouteloua hirsuta, Bothriochloa barbinodis, Eragrostis intermedia, Leptochloa dubia, Lycurus phleoides, Poa fendleriana ssp. longiligula (= Poa longiligula), and Digitaria californica (= Trichachne californica) with scattered forb species of Boerhavia, Heterotheca, and Penstemon (Brown 1982). The floristic description is based on several references, including Cable (1975a), Carmichael et al. (1978), Brown (1982), Dick-Peddie (1993), Reid et al. (1999), Tirmenstein (1999d), Comer et al. (2003), and NatureServe Explorer (2011).

This chaparral system occurs across central Arizona (Mogollon Rim), western New Mexico, and southern Utah and Nevada. It does not occur as far west as California. It often dominates along the mid-elevation transition from the eastern Mojave, Sonoran, and northern Chihuahuan deserts into mountains (1000-2200 m). It occurs on foothills, mountain slopes and canyons in hotter and drier habitats below the encinal and Pinus ponderosa woodlands. Stands are often associated with more xeric and coarse-textured substrates such as limestone, basalt or alluvium, especially in transition areas with more mesic woodlands. Adjacent upland systems include Southern Rocky Mountain Ponderosa Pine Woodland (CES306.648), Madrean Encinal (CES305.795), Madrean Pinyon-Juniper Woodland (CES305.797) or Great Basin Pinyon-Juniper Woodland (CES304.773) above and at lower elevations, Sonoran Mid-Elevation Desert Scrub (CES302.035) and Mojave Mid-Elevation Mixed Desert Scrub (CES302.742). The environmental description is based on several references, including Cable (1975a), Carmichael et al. (1978), Brown (1982), Dick-Peddie (1993), Reid et al. (1999), Tirmenstein (1999d), Comer et al. (2003), and NatureServe Explorer (2011).

Most chaparral species are fire-adapted, resprouting vigorously after burning or producing fire-resistant seeds. Stands occurring within montane woodlands are seral and a result of recent fires. Disturbance dynamics in this system are variable because of variation in composition of dominant species; however, most dominant shrubs are evergreen species that are adapted to medium frequency, medium to large-sized and medium- to high-intensity fire, in late summer or fall. Some species such as Cercocarpus montanus, Garrya wrightii, and Quercus turbinella are generally top-killed in burns, but then vigorously resprout from root crown or buried lignotubers (Uchytil 1990, Tirmenstein 1999d, Gucker 2006e). Most also have seeds stored in soil and duff that need fire scarification to germinate. Other chaparral shrub such as Arctostaphylos pungens, Ceanothus greggii, and Purshia stansburiana are killed or sprout only weakly after fire and regenerate from fire-scarified seeds in the seedbank (Howard 1995, Zouhar 2000, League 2005). Some deciduous species such as Rhus trilobata are also adapted to fire, vigorously resprout after burning and have fire-scarified seeds (Anderson 2004a). Fire-return interval (FRI) for this systems is medium (5-70 years) on most of the dominant species (Howard 1995, Tirmenstein 1999d, Zouhar 2000, Anderson 2004a, League 2005, Gucker 2006e). Recovery times after fire for Quercus turbinella-dominated chaparral stands range from 4 to 8 years or more (Tiedemann and Schmutz 1966). Cable (1957) observed that this shrub regained preburn density within 5 years after fire in Arizona.

The foliage of most of these chaparral shrubs is utilized as browse at least to some degree (new growth) by big game species with Ceanothus greggii, Cercocarpus montanus, Purshia stansburiana, Garrya wrightii, and Rhus trilobata being especially important (Uchytil 1990, Howard 1995, Zouhar 2000, Anderson 2004a, Gucker 2006e). Small mammal and birds use the acorns and fruits of many of the dominant chaparral species (Cable 1975a, Howard 1995, Tirmenstein 1999d, Zouhar 2000, Anderson 2004a, League 2005, Gucker 2006e).

Chaparral stands dominated by Quercus turbinella are used by cattle, domestic sheep (USFS 1937), and domestic goats at least moderately (Cable 1957, 1975a). Much of this chaparral system has been impacted by livestock use because of high accessibility and relatively gentle terrain, especially in lower-elevation stands (Brown 1982a).

Human development has impacted many locations throughout the ecoregion. High- and low-density urban and industrial developments also have large impacts. For example, residential development has significantly impacted locations within commuting distance to urban areas. Impacts may be direct as vegetation is removed for building sites or more indirectly through natural fire regime alteration, and/or the introduction of invasive species. Mining operations can drastically impact natural vegetation. Road building and power transmission lines continue to fragment vegetation and provide vectors for invasive species.

This system occurs across central Arizona (Mogollon Rim), western New Mexico and southern Utah. It often dominates along the mid-elevation transition from the Mojave, Sonoran, and northern Chihuahuan deserts into mountains (1000-2200 m elevation). It does not occur as far west as California.