Brown described this biotic community as the Rocky Mountain (Petran) Subalpine Conifer Forest while Merriam referred to it as the Hudsonian or Subalpine Life Zone. Most people simply refer to this life zone as spruce-fir forest. Merriam placed it at 9,000 to 11,500 feet with 30 to 35 inches of precipitation annually. He listed the primary species as Abies lasiocarpa and Picea engelmanni. Brown places this community at 2,450 to 2,600 meters and up to timberline at 3,500 to 3,800 meters. These forests are cold (with an interrupted growing season of 75 days or less) and moist (635 to 1000+ mm of precipitation). On the San Francisco Peaks there is a unique subspecies of the subalpine fir, Abies lasiocarpa var. arizonica. Scattered throughout this biome, there are also two species of high elevation pines, Pinus aristata, which often grows at treeline, and P. flexilis, which is rare in the Inner Basin and adjacent slopes. In closed canopy forests, duff is deep and the understory sparse. Juniperus communis is a common understory shrub where the forest canopy is more open. Pure stands of Populus tremuloides can occur in areas of forest disturbance. The transition to Petran Montane Conifer Forests (Brown) also known as Canadian or Mixed Conifer Life Zone (Merriam) can be subtle and indistinct. A general rule of thumb is to look at regeneration or the seedling trees. If the seedlings are spruce and fir, you are probably in Subalpine Conifer Forest. If the seedlings are Psuedotsuga menziesii, you are probably in Mixed Conifer Forest.
Indicator tree species are: Picea engelmannii, Picea pungens, Abies lasiocarpa, Pinus aristata, with little Populus tremuloides. Comon shrubs are Lonicera involucrata, Juniperus communis, Ribes montigenum, Sambucus racemosa.