Arizona Mountains forests
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Introduction
The Arizona Mountain Forest extends from the Kaibab Plateau in northern Arizona to south of the Mogollon Plateau into portions of southwestern Mexico and eastern Arizona. This area consists mainly of steep foothills and mountains, but includes some deeply dissected high plateaus. Elevations range from 1,370 to 3,000 meters (m) with some peaks to 3,840 m. Soil types have not been well defined; however, most soils are entisols with alfisols and inceptisols in upland areas. Stony land and rock outcrops occupy large areas on the mountains and foothills.
Vegetation zones in this ecoregion resemble the Rocky Mountain Life Zones but at higher elevations. Although forests in this ecoregion are too far south to support distinct alpine communities, they do have a well-defined Transition Zone at 1,980-2,440 m where a cool, moist climate supports pine forests above the drier pinyon-juniper-oak woodlands of lower elevations. These forests are both wet and cold, averaging 635 millimeters (mm) to 1,000 mm with annual precipitation increasing in the upper elevation Canadian Zone. The growing season is typically less than 75 days with occasional nighttime frosts.
The Transition Zone in this region comprises a strong Mexican fasciation, including Chihuahua pine (Pinus leiophylla) and Apache pine (P. engelmannii) and unique varieties of ponderosa pine (P. ponderosa var. arizonica). Such forests are open and parklike and contain many bird species from Mexico seldom seen in the U.S.. The Canadian Zone (above 2,000 m) includes mostly Rocky Mountain species of mixed-conifer communities such as Douglas-fir (Pseudotsuga menzeisii), Engelmann spruce (Picea engelmanni), subalpine fir (Abies lasiocarpa), and white fir (corkbark variety, A. lasiocarpa var. arizonica). Dwarf juniper (Juniperus communis) is an understory shrubby closely associated with spruce/fir forests. Exposed sites include southwestern white pine (P. strobiformis, a variety of limber pine), while disturbed north-facing sites consists primarily of lodgepole pine (P. contorta) or Quaking aspen (Populus tremuloides).
Virgin forests in this region often exceed 25 m in height and are commonly layered in 2 or more age classes. Below 2,900 m one or more of the age classes may be composed solely of Quaking aspen, an important wildlife habitat component and pioneer species following fire. Wetter sites contain Rocky Mountain maple (Acer glabrum), Bebb willow (Salix bebbiana), scouler willow (S. scouleriana), blueberry elder (Sambucus glauca), thin-leafed alder (Alnus tenuifolis), or bitter cherry (Prunus emarginata). Dry windy sites may be occupied by limber pine (P. flexis) and Bristelcone pine (P. aristata). At lower elevations (less than 2,600 m) Douglas-fir intermingles with ponderosa pine and white fir (A. concolor).
Biological Distinctiveness
In general, this ecoregion was considered regionally outstanding because of its relatively high levels of species richness (2,817 spp) and endemism (132 spp). Plants were the richest (78% of the total species) taxa, followed by birds (7%) and butterflies (7%), snails (3%) and mammals (3%) and other taxa. Most (26%) endemics were also plants.
This ecoregion was also the southern extent of spruce/fir forests and northern extent of many Mexican wildlife species, including tropical birds and reptiles. The Gila Wilderness in southwestern New Mexico contains perhaps the largest and "healthiest" ponderosa pine forest in the world. The region also has outstanding subterranean biodiversity with an extensive cave fauna in Guadelupe. In addition, there is great potential for restoring Mexican wolf (Canis lupus) and grizzly bear (Ursus arctos horribilis) populations in the area because of its remoteness and juxtaposition to other ecoregions where these species were formerly prevalent.
Of local conservation importance is the status of riparian areas. Riparian areas, in general, represent less than 1 percent of southwestern landscapes yet are critically important to wildlife, water quality, and fish habitat.
Conservation Status
Habitat Loss and Degradation
In general, the ecoregion was considered relatively stable with approximately 25 percent of it still intact. However, several threats to the ecoregion were identified by workshop participants and the published literature, including the following:
- logging and related fragmentation of old growth and roadless areas
- severe overgrazing in wilderness areas
- heavily degraded stream channels and loss of habitat for the endangered Gila trout (Oncorhynchus gilae) and southwestern willow flycatcher (Empidonax traillii extimus).
- global endangerment of Freemont cottonwood (P. fremontii) and Goodding willow (S. gooddingii). These trees grow primarily in wet soils along streams.
- timber harvest in mature and old growth forests preferred by the Mexican spotted owl (Strix occidentalis lucida and northern goshawk (Accipiter gentalis) (particularly on the Kaibab Plateau).
Remaining Blocks of Intact Habitat
Several sizable blocks of intact habitat remain in this ecoregion including the following areas:
- Aldo Leopold-Gila Wilderness - southwestern New Mexico
- Blue Range Primitive Area - eastern Arizona
- Guadalupe-Carlsbad area - southeastern New Mexico and western Texas
- Kaibab Plateau and national forest - north-central Arizona
- Grand Canyon National Park - northwestern Arizona
- Chuska Mountains on Navaho lands - northeastern Arizona and northwestern New Mexico
- Mazatzal Complex - central Arizona
- Superstition Mountains - central Arizona
- El Malpais National Monument and Conservation Area - western New Mexico
In addition, Foreman and Wolke identified several large (40,000 hectares) roadless areas, including:
- Sycamore Canyon-Secret Mountains - north-central Arizona
- Hellsgate - central Arizona
- Four Peaks - central Arizona
- Salt River; Baldy Bill - central Arizona
- Eagle Creek; Gila Mountains - eastern Arizona
- Galiuro Mountains - eastern Arizona
Degree of Fragmentation
Habitat fragmentation in this region has been primarily related to timber harvest in roadless areas and old age forest classes. Several areas were recommended by workshop participants as potential corridors for minimizing fragmentation and insularization effects, including connecting the Gila complex with the Sky Islands to the south for future wolf movements; connecting the Gila complex with the Mataxal complexes at Showlow New Mexico; and connecting riverine habitat through stream buffers designed to restore degraded fish populations.
Degree of Protection
The large wilderness areas identified above are largely protected from logging; however, grazing continues to be a concern in some wilderness areas. In general, about 9 percent of the ecoregion is in areas permanently protected from industrial logging and mining.
Types and Severity of Threats
There are several threats to the ecoregion, including conversion (road building, timber harvest); degradation (fire suppression, mining, ORV use, logging, fuel gathering); and potential wildlife losses (high threat to future Mexican wolf reintroduction from poaching). Additional threats to riparian areas, and old growth forests and roadless areas were identified in the literature.
Suite of Priority Activities to Enhance Biodiversity Conservation
Within this ecoregion the best opportunities for conservation include the following:
- control overgrazing on the Diamond Bar allotment in the Gila Wilderness
- protect and restore degraded native fish populations, particularly endemic trout through habitat restoration in degraded riparian areas
- protect remaining old growth and roadless areas
- promote reintroduction of the Mexican wolf and maintain habitat connections across ecoregions of suitable occupation
- designate Blue Range Wilderness area
- restore fire to fire-suppressed forest types
Conservation Partners
- Sierra Club
- Sky Island Alliance
- Southern Rockies Ecosystem Project
- Southwest Center for Biological Diversity
Relationship to Other Classification Schemes
This ecoregion corresponds to Omernik's ecoregion #23 (Arizona/New Mexico Mountains) and there is a fair degree of overlap with Bailey's M313; Arizona-New Mexico Mountains Semi-Desert-Open Woodland-Coniferous Forest-Alpine Meadow Province.
Additional Information on this Ecoregion
- For a shorter summary of this entry, see the WWF WildWorld profile of this ecoregion.
- To see the species that live in this ecoregion, including images and threat levels, see the WWF Wildfinder description of this ecoregion.
- World Wildlife Fund Homepage
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