Petran Subalpine Conifer Forests and Alpine Tundra
Petran subalpine conifer forests are at the southern end of their range in Arizona. Typically above 8,500 ft. above sea level, these forests are variable and complex. They occur at the highest elevations of plateaus and mountain ranges in northern Arizona (e.g., Kaibab Plateau, San Francisco Mountain, White Mountains) as well as in the southern reaches of the state (e.g., Pinaleño, Chiricahua and Santa Catalina mountains).
A number of coniferous and deciduous species characterize these forests. At higher elevations and on north facing slopes the dominant conifers are usually Engelmann spruce and subalpine fir. On drier and more exposed sites, limber and bristle-cone pines may dominate. At lower elevations these forests are composed of a broad mix of coniferous species including blue spruce, white fir, and Douglas fir. This elevational band is often referred to as the cool/moist mixed conifer forest (Margolis et al. 2013). Quaking aspen is the dominant deciduous species and is found intermixed with the conifers, however pure aspen stands may be found post-fire. Dense overstories limit or prevent growth of herbaceous vegetation except in aspen stands and along forest edges where bunchgrasses are common. Otherwise, understory vegetation is limited to mosses, lichens, and prostrate junipers (Brown et al. 2020; Margolis et al. 2013).
Historically, Petran subalpine conifer forests were subject to a high-severity fire regime where fires were infrequent and stand-replacing. Patch sizes varied from as small as 74 acres to greater than 2,400 acres. After a high-severity fire, these forests followed a fairly predictable successional pathway beginning with aspen regeneration, followed by shade-tolerant conifer regeneration, and eventually forming an aspen/mixed conifer forest. Due to the patchiness of high-severity fires, irregular forest structures were common across stands and at landscape scales. Stands were multi-storied due to the shade tolerance of mixed-conifer tree species and the infrequency of high-severity fires that did not have the effect of “thinning from below.” While high-severity fire patches from recent fires may be larger than historical ones, the fire regime and resulting forest structures have not changed as dramatically in these forests as they have in drier forest communities at lower elevations (e.g., ponderosa pine-dominated forests). Petran subalpine conifer forests may be within their natural range of variability and do not necessarily indicate a need for restoration (Margolis et al. 2011; Margolis et al. 2013).
However, due to their limited distribution in Arizona, Petran subalpine conifer forests have been disproportionately affected by a small number of development projects such as ski runs, communication towers, and observatories (Patten and Stromberg 1995; Dahms and Geils 1997). They have also been degraded by a century of livestock grazing and fire suppression and have experienced significant tree mortality due to drought and insect infestation. In 2019, beetle-caused tree mortality in Douglas fir, white fir, and subalpine fir increased in Arizona and affected about 35,000 acres, primarily on the Apache-Sitgreaves and Coconino national forests and on the Navajo Nation. However, spruce beetle mortality has been consistently low in Arizona (120 acres in 2019) with most of the activity observed on White Mountain Apache lands (USFS 2020). In addition, invasive pests affect Engelmann and blue spruce (spruce aphid) and more recently aspen (oystershell scale). Recent monitoring indicates the emergent oystershell scale is widespread in northern Arizona and is contributing to aspen mortality on the Coconino, Kaibab, Apache-Sitgreaves, and Prescott national forests. A new effort to evaluate aspen decline was initiated in 2019 (USFS 2020).
Alpine tundra is found above 11,500 ft above sea level. Restricted to a few thousand acres above timberline on the highest peaks of San Francisco Mountain and on Mount Baldy, it is one of the rarest biotic communities in Arizona. This community is extremely isolated from any other alpine tundra, with the closest being in central New Mexico. Extreme cold temperatures exclude trees. Dominant plants are ground-hugging forbs and grasses (Brown 1990). Some recreational activity and past sheep grazing have affected this community. However, the largest threat is climate change which could lead to the elimination of alpine tundra habitats in Arizona.
The following describes habitat features or microhabitats in this habitat type that are of particular importance to certain species:
Sinkholes are important as they can provide important sources of water and feeding and nesting habitat for many species of mammals, birds, reptiles, and amphibians in an otherwise xeric environment.
Wet meadows and vernal pools typically have surface water only during the wetter periods of the year and do not usually support fish unless they are connected to perennial water. These habitats are important for amphibians such as leopard frogs and tiger salamanders, because their early life stages can thrive free of fish and other predators.
Talus slopes and boulder piles along hillsides and canyon drainages provide essential sheltering habitat for native land snails like talussnails and mountainsnails during hot, dry periods of the year. These mollusks aestivate for months in the cool and damp interstitial spaces in talus, under boulders, and deep rock crevices.
Aspen stands provide important habitats for many species at these high altitudes, including mule deer and red-naped sapsucker. Many aspen stands are in decline thanks to fire-suppression, conifer encroachment, and over-browsing by elk.
Maple draws provide important breeding and foraging habitats for many neotropical migrant bird species, such as red-faced warbler and hermit thrush.
The following list represents SGCN in this habitat type that AZGFD actively manages or are watching closely due to some level of concern:
American Pipit, American Three-toed Woodpecker, Canada Jay, Clark's Nutcracker, Evening Grosbeak, Golden-crowned Kinglet, Hermit Thrush, American Goshawk (Northern Goshawk), Pine Grosbeak, Red-faced Warbler, Swainson's Thrush, Mountain West White-crowned Sparrow
The following list represents plant species that are known to occur in this habitat type:
The following are other wildlife species, native and non-native, that can have particular influence in this habitat type. Influential species can affect SGCN and their habitats directly and indirectly, for example altering predator/prey interactions, overgrazing, outcompeting natives, creating microhabitats, and others.
Arizona Tiger Salamander
Dusky Grouse, Northern Saw-whet Owl, Red-breasted Nuthatch, Red-naped Sapsucker, Ruby-crowned Kinglet, Williamson's Sapsucker
American Black Bear, Long-legged Myotis, Mt Graham Red Squirrel, Rocky Mountain Elk, Silver-haired Bat
San Francisco Peaks Ragwort
The following describes the primary threats facing this habitat type, adapted from Salafsky et al. (2008). First-level threats (i.e. Agriculture, Climate Change) represent broad categories while second-level threats reflect more specific stressors to the system. For detailed information on threats to this habitat type and conservation actions being taken, see Chapter 8: Threats and Conservation Actions.
3. Climate Change and Severe Weather
5. Disease, Pathogens, and Parasites
7. Human Intrusions and Disturbance
11. Transportation and Service Corridors
The following describes specific conservation actions that can be taken to reduce or eliminate threats to this habitat type, adapted from Salafsky et al. (2008). Level 1 conservation actions (i.e. Land and Water Protection) represent broad categories of potential actions, while the Level 2 conservation actions (i.e. Resource and habitat protection) are more specific.
2. Land and Water Management
- Collaborate with local land management agencies and utility companies to ensure that recreational use and transportation and service corridors do not further negatively impact habitats. (Threats 7.1, 11.2)
- Support the USFS effort to evaluate aspen decline. (Threat 5)
4. Education and Awareness
- Develop public understanding and support for ecosystem services provided by healthy natural communities (e.g., clean water, clean air). (Threats 3.1, 7.1, 11.2)
- Develop public understanding and support for limited and unique communities that provide essential wildlife habitats. (Threats 3.1, 7.1, 11.2)
5. Law and Policy
- Support ongoing efforts to better understand diseases, pathogens and parasites in Petran subalpine conifer forests. (Threat 5)
The following describes some of the conservation strategies that may mitigate the effects of a changing climate for this habitat type. Strategies have been adapted from guidelines by the Association of Fish and Wildlife Agencies (AFWA 2009).
Implement long-term monitoring protocols for vulnerable species and habitats to inform adaptive management.
Establish new wild and/or captive populations of climate vulnerable SGCN.
Conduct research targeting species and habitat types likely to be vulnerable to climate change impacts.
Collect specimens or samples for taxonomic analysis, genetics, research, and/or disease testing.
Test novel husbandry techniques, new technology, and/or life history research on native aquatic wildlife to improve survival, growth, production, health, condition, transportation, release, and post-release performance of captive progeny.
The following describe other routine or on-going conservation actions AZGFD regularly performs in this habitat type:
- Conduct surveys and monitor populations of SGCN as specified in work plans and job statements.
- Survey the influential species (when possible) within these habitats to minimize negative impacts to habitat and associated species.
- Fund or work with partners to conduct conservation-related research.
- Manage recreational activities and OHV use of conifer habitats to minimize negative impacts to habitat and associated species.
- Collect specimens or samples for taxonomic analysis, genetics, research, and/or disease testing.
The following represents identified COAs where conservation efforts would benefit wildlife and their habitats.
The following is a list of the organizations and agencies that AZGFD regularly partners with on conservation efforts in this habitat type:
- US Forest Service
- USFWS Arizona Ecological Services
- Private Landowners
- Grazing Permitees
- White Mountain Apache Tribe
- University of Arizona
- Arizona Field Ornithologists
- The Nature Conservancy
- The Grand Canyon Trust
The following are relevant conservation agreements, plans, and other documents or particular interest regarding wildlife in this habitat type: