The Arizona/New Mexico Mountains ecoregion is a Level III ecoregion designated by the United States Environmental Protection Agency (EPA) in the U.S. states of Arizona and New Mexico, with a small extension into the Guadalupe Mountains in Texas. The World Wildlife Fund named this ecoregion Arizona Mountains forests, and classified it as a temperate coniferous forests ecoregion. The ecoregion has a rich variety of woodland habitats and wildlife.
Setting The region is a transition region from the lower elevation Sonoran Desert (81) to the southwest and Chihuahuan Desert (24) southeast; the west is bordered by the mid-elevation Mojave Desert (14).
The north is bordered by the east–west Arizona/New Mexico Plateau (22), ecoregion which is part of and is the southern region of the Colorado Plateau. The north region of the Colorado Plateau covers eastern Utah/western Colorado and is the Colorado Plateaus ecoregion (20). The extreme southern perimeter of the Colorado Plateaus ecoregion extends east–west along the border regions of Arizona-New Mexico.
The ecoregion landscape of steep mountains and high stony plateaus with rocky outcrops from the Kaibab Plateau in northern Arizona south to the Mogollon Plateau, extending eastwards into southwestern New Mexico and into the Trans-Pecos region of West Texas. Elevations range from , with some peaks higher than that. Specific areas include the Gila Wilderness in New Mexico.
Approximately 57.6% of this ecoregion lies within Arizona, 42.3% within New Mexico, and less than 0.1% in Texas.
Subregions
This ecoregion spans the mountains of Arizona and New Mexico, and has a number of subregions, described below.
Chihuahuan Desert Slopes (23a)
The Chihuahuan Desert Slopes are found on the Guadalupe and Sacramento Mountains. The lower slopes of these mountains represent a continuation of the Chihuahuan Desert ecosystem; soils and vegetation in much of ecoregion 23a are similar to those in the low mountains and bajadas of the Chihuahuan Deserts. The lower slopes were once mostly grasslands overgrazed in the late 19th century and subsequently invaded by desert shrubs. Yucca, sotol, lechuguilla, ocotillo, and cacti now dominate the rocky slopes below . Grasslands persist near alluvial fans and on gentle slopes with deeper, sandstone-derived soils. Water is scarce; the few streams that originate from springs at higher elevations do not persist beyond the mouths of major canyons.
Madrean Lower Montane Woodlands (23b)
The Madrean Lower Montane Woodlands ecoregion covers the slopes of the Guadalupe, Sacramento, Mimbres, Big Burro, and Mogollon Mountains, extending into the Mogollon Transition/Mogollon Rim in Arizona. The ecoregion generally lies between in New Mexico and in Arizona, with densities of juniper, pinyon pine, and oak varying according to aspect. There are some similarities to ecoregion 23e; however, this has milder winters, wetter summers, and inclusions of alligator juniper and Madrean evergreen oak species, such as Gray and Emory oak. At middle elevations, dense thickets of shrubs such as desert ceanothus, alderleaf mountain mahogany, turbinella oak, manzanitas, and catclaw mimosa form chaparral communities. Other areas are grassy and park-like with mixed gramas and scattered trees. A few small areas of ponderosa pine, Douglas-fir, or southwestern white pine occur at the highest elevations, outliers of ecoregions 23c or 23f. The Arizona sycamore is also known from this ecoregion. In the west, the Gila River and tributaries have many endemic aquatic organisms including fish, amphibians, and insects.
Montane Conifer Forests (23c)
The Montane Conifer Forests are found west of the Rio Grande at elevations from about . Ponderosa pine and Gambel oak are common, along with mountain mahogany and serviceberry. Some Douglas-fir, southwestern white pine, and white fir occur in a few areas. Blue spruce may occasionally be found in cool, moist canyons. The influence of the Sierra Madre flora is seen mostly in the southern mountains and diminishes to the north. In the far south, other oaks appear, such as silverleaf oak, netleaf oak, Arizona white oak, and Emory oak. The summer rains are especially important for herbaceous plants. The region is geologically diverse with volcanic, sedimentary, and some intrusive and crystalline rocks. Endemic Gila trout occur in some of the region's streams. Livestock grazing, logging, and recreation are the primary land uses. Wildfire is an important feature influencing the forested ecosystems in this region.
Arizona/New Mexico Subalpine Forests (23d) The Arizona/New Mexico Subalpine Forests occur west of the Rio Grande at the higher elevations, generally above . The region includes parts of the Mogollon Mountains, Black Range, San Mateo Mountains, Magdalena Mountains, and Mount Taylor. In Arizona this region encompasses higher elevations in the San Francisco Peaks, White Mountains (Arizona), Kendrick Peak, Kaibab Plateau, and Escudilla Mountain. The peak elevations are mostly above . Although there are some vegetational differences from mountain range to mountain range within this ecoregion, the major forest trees include Engelmann spruce, corkbark fir, blue spruce, white fir, and aspen. Some Douglas-fir occurs at lower elevations. The ecoregion has a mixed geology of mostly Tertiary volcanics and intrusives, with only minor areas of Precambrian rocks in the Black Range.
Conifer Woodlands and Savannas (23e) The Conifer Woodlands and Savannas ecoregion is an area of mostly pinyon-juniper woodlands, with some ponderosa pine at higher elevations. It often intermingles with grasslands and shrublands. Although elevations are higher than surrounding ecoregion 22 areas, the boundaries tend to be transitional. The region is generally cooler, with more uniform winter and summer seasonal moisture compared to ecoregion 23b. It lacks the milder winters, wetter summers, chaparral, Madrean oaks, and other species of ecoregion 23b.
Rocky Mountain Conifer Forests (23f)
The Rocky Mountain Conifer Forests are found at elevations from about in the mountains east of the Rio Grande. Similar to Ecoregion 23c, ponderosa pine and Gambel oak are common, with mountain mahogany and a dense understory. Some Douglas-fir, southwestern white pine, and white fir occur in a few areas. Blue spruce may occasionally be found in cool, moist canyons. In the Sandia and Manzano Mountains, white fir and Douglas-fir are more extensive than in other parts of the region. Current forests have been shaped by fire and fire suppression. It differs from Ecoregion 23c by some of the flora, fauna, and water quality characteristics that more closely resemble the Southern Rockies. The region is geologically diverse with volcanic, sedimentary, and some intrusive and crystalline rocks.
Rocky Mountain Subalpine Forests (23g)
The Rocky Mountain Subalpine Forests ecoregion occurs east of the Rio Grande at high elevations, generally above . It includes parts of the Sandia Mountains, Capitan Mountains, and Sierra Blanca. The peak elevations are mostly above , with Sierra Blanca Peak nearing . There are some differences in flora, fauna, geology, and water quality from the subalpine ecoregion (23d) to the west. The major forest trees include Engelmann spruce, corkbark fir, blue spruce, white fir, and aspen. Some Douglas-fir occurs at lower elevations. There are a few small inclusions of montane grassland. A mix of geology occurs in the region. Sierra Blanca and the Capitan Mountains are composed of Tertiary volcanic and Intrusive rocks, while the Sandia Mountains to the north have a core of Precambrian rocks capped by Pennsylvanian sedimentary rocks.
Lower Mogollon Transition (23h) The Lower Mogollon Transition occurs at elevations mostly between and contains diverse vegetation, including desert scrub, semi-desert grasslands, and chaparral communities. Some juniper woodland occurs at higher elevations. The hilly to mountainous terrain has numerous canyons and valleys, and a variety of rock types. It is mostly lower, warmer, and drier than adjacent Ecoregion 23b. Precipitation averages . Vegetation includes canotia, mesquite, catclaw acacia, jojoba, turbinella oak, mountain-mahogany, ceanothus, shrubby buckwheat, skunkbush sumac, and silktassel. Grassy areas have tobosa, grama grass species, and plains lovegrass, along with scattered agaves, yuccas, sotol, opuntia, and snakeweed.
Montane and Subalpine Grasslands (23i) The Montane and Subalpine Grasslands ecoregion includes subalpine grasslands that occur above about in elevation, as well as some of the other larger montane grasslands of the Arizona/New Mexico Mountains, typically above . Precipitation averages about per year. The larger areas tend to be relatively flat with poorly drained soils. Vegetation includes mixed sedge species, Arizona fescue, mountain muhly, pine dropseed, ponderosa pine, spruce, fir, and quaking aspen. The high elevation grasslands and forest edges provide important habitat for elk, deer, gophers, and voles, as well as numerous bird species. Some of these areas have been used for summer forage for cattle and sheep, especially since the late 1800s, leading to erosion and changes in grass and forb communities. Exotic grasses such as Kentucky bluegrass have become more common.
Northern Woodlands and Sagebrush (23j)
The Northern Woodlands and Sagebrush ecoregion occurs at the lower elevations of the Kaibab Plateau and, to the east, surrounds the Defiance Plateau and the Chuska and Carrizo Mountains. Juniper and pinyon pine dominate the woodland similar to Ecoregion 23e to the south; however, in this northern region, sagebrush is a more conspicuous component, and there is a less diverse grass and forb community. The climate also differs from Ecoregion 23e in that the majority of precipitation here occurs in the low-sun, cold season.
Sunset Crater Volcanics (23k)
The Sunset Crater Volcanics ecoregion includes volcanic cones, lava flows, and cinder and ash deposits, and is distinguished from adjacent areas by its stunted conifer trees and several endemic species. Although some of these youngest Holocene and Pleistocene volcanic features extend to the east and north, this region encompasses only the forested or wooded portions of an area that was affected by the most recent eruptions about 900 to 1000 years ago. This is the youngest part of the San Francisco Volcanic Field, a field with a 6 million year history and an area that extends west to near Williams, Arizona. The San Francisco Volcanic Field contains more than 600 volcanic vents.
Mogollon Transition Conifer Forests (23l) The Mogollon Transition Conifer Forests ecoregion includes the areas of pine forests that occur below the Mogollon Rim and in scattered high-elevation patches on the southern side of Ecoregion 23. The ponderosa pine forests in these southern mountains have a Sierra Madre flora influence, with evergreen oaks such as silverleaf oak, netleaf oak, and Emory oak. These areas are generally less productive for commercial timber than the forests of Ecoregion 23c because of competition with dense understory brush and evergreen oaks.
Flora and Fauna The Arizona/New Mexico mountains ecoregion is exceptionally diverse in plant and animal life. According to a 1999 study published by the World Wildlife Fund there may be at least 2,817 species of native vascular plants in the Arizona/New Mexico mountains ecoregion. This number may be outdated as there is an estimated 12 new species of native vascular plants described from the state of Arizona annually according to SEINet. There are also a significant number of endemic species within the region.