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) '' in the
Mogollon Mountains The Madrean Lower Montane Woodlands ecoregion covers the slopes of the Guadalupe, Sacramento,
Mimbres,
Big Burro, and
Mogollon Mountains, extending into the
Mogollon Transition 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. 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. ==Flora==