Physiographic Region 62: Southern Rocky Mountains
Description and Ecology: Spruce-fir forest in Physiographic Area 62 is present at 2750 to 3650
m (9,000-12,000 ft) in elevation. Engelmann spruce and subalpine fir are the dominant tree
species. Engelmann spruce is found without subalpine fir at the lower elevations, but only on
cool, sheltered sites. Lodgepole pine and aspen are often mixed in at lower and middle elevations,
and limber pine and bristlecone pine are present at middle and higher elevations. At the highest
elevations, where spruce-fir gives way to alpine tundra, the harsh climate restricts these trees to a
small, contorted, often ground-hugging growth form known as "krummholz." Most precipitation
is in the form of snow, which remains on the ground well into spring. Because spruce-fir forests
are cooler and wetter than other forests in Physiographic Area 62, fire is comparatively
uncommon, with perhaps several hundred years passing between fires at a given location. As a
result, these forests produce large trees, with mature specimens reaching 90 cm (3 ft) dbh and 35
m (120 ft) tall. Understory vegetation can vary from sparse to quite dense, perhaps the densest of
the conifer forests in this region with the exception of dense Gambel oak under ponderosa pine.
Blueberry, shrubby cinquefoil, and Colorado currant are common components. The primary
disturbance agents are blowdown and insect infestations (Engelmann spruce beetle and western
spruce budworm). When fires do occur, they are often stand-replacement fires, fed by the dense
trees and understory, although moisture and other factors result in patchy dispersal across the
landscape. Recovery from disturbance is slow due to the cold winters and a short, cool growing
Importance and Conservation Status: In comparison with spruce-fir forests of eastern North
America, which generally support more insects and insectivorous birds, many of which are
Neotropical migrants, spruce-fir forests in the Southern Rocky Mountains support fewer insects
and insectivorous birds and fewer Neotropical migrants. Instead, the avian community in this area
has a comparatively large number of seed-eating birds, a reflection of the abundant cone crops
available here. Compared to eastern spruce forests, fewer birds of this region are of conservation
concern. Birds commonly found in this forest type include the Gray Jay, Mountain Chickadee,
Red-breasted Nuthatch, Ruby-Crowned Kinglet, Hermit Thrush, Pine Grosbeak, and Pine Siskin.
Spruce-fir forests are a valuable source of timber in Colorado; the resulting logging pressure
along with slow regeneration may have negative consequences for avian communities.
Priority Species Accounts: Three species are identified as high priority in Spruce-Fir habitats
in Physiographic Area 62: Boreal Owl, Olive-sided Flycatcher, and Hammond's Flycatcher.