The Independence Pass corridor is notable for passing through three major life zones—the montane, subalpine and alpine, each of which has specific characteristics determined by elevation. In addition, the Roaring Fork River and its tributaries support riparian ecosystems along their banks. From the harsh, wind-blown tundra at the summit of the Pass, to the lush oxbow meadows of the North Star Nature Preserve, the Pass corridor presents a wide variety of flora and fauna which are characteristic of high valleys in the Rocky Mountains.
The montane zone extends from the lush meadows just east of Aspen to the Lincoln Creek drainage at around 10,000 feet. This zone is made up of relatively cool, moist upland slopes where large evergreens constitute the climax vegetative type. Douglas fir, aspen and Colorado blue spruce are typical tree types, and alder, narrowleaf cottonwood and willow lines the riparian corridors. Columbine, meadow rue, aster, Indian paintbrush and monkshood are typical wildflower types. Understory shrubs include kinnikinnick, mountain ash, thimbleberry, chokecherry, serviceberry and wild raspberry.
North Star Nature Preserve, which was acquired by Pitkin County in the late 70s, is the largest flat area in the montane zone. At this location, an ancient lateral moraine marked the end of the glaciers that filled the Pass corridor during the last ice age. The moraine dammed the Roaring Fork River as the glacier retreated, creating an ancient lake in this location. The lake, in turn, collected silt, plant debris and fine soils, which created the deep, peaty subsoil in this location. This area was a vast willow wetland before it was cleared for farming and ranching in the late 19th century. The total area now protected by public ownership in this location is over 150 acres between the east end of Aspen and Difficult Campground.
The old oxbow lakes on North Star and elsewhere at the lower end of the Pass corridor support a host of plants and animals ranging from microscopic plankton to fish, ducks, amphibians and wading birds. The Tagert Lake property, a private inholding near the Winter Gate on Highway 82, marks the uppermost end of these willow and sedge-dominated wetlands.
The subalpine zone extends from Lincoln Creek to the Linkins Lake Trailhead 1.5 miles below the summit of the Pass. Both Lincoln Creek and the upper Roaring Fork Valleys are marked by the glaciers that shaped them 10,000 years ago. Glacial debris, scoured rock faces and deeply incised river canyons are typical features. Short growing seasons, extreme temperature fluctuations and deep snow cover dictate that plants and animals in this zone are hardy, well-adapted, and slow-growing.
Englemann spruce, subalpine fir, aspen and lodgepole pine are typical in this zone, and common wildflowers include Parry's primrose, wild woods rose, marsh marigold, fireweed and calypso orchid. Beaver colonies are found in areas where the river can be dammed, and elk and mule deer use this area for summer grazing. Year-round animal inhabitants include marmots, pine marten, coyote, black bear and various small rodents.
The alpine zone extends from the Linkins Lake trailhead near mile marker 59 to the summit of the Pass. This zone is characterized by extreme temperature fluctuations, deep snowpack, high winds, and a very short growing season. Vegetation and wildlife use is limited by the short growing season and harsh conditions. Typical plants include mosses and lichen, wild strawberry, snowberry, willows, bog birch and a variety of hardy grasses and wildflowers. Wildlife living in the alpine zone year-round includes ptarmigan, pika, marmot, mountain goat and pocket gopher.