Life Zones

Pinyon pine (Pinus edulis) along the Warner Point Trail

NPS/Alice de Anguera

Life zones are ecosystems found at different elevations. Black Canyon is known for its vertical landscape; various life zones exist from the canyon rim, along the canyon walls, and at the river level. Plants and animals within each life zone are adapted to its conditions.

Pinyon-Juniper Forest

The Colorado Plateau is a geologic region characterized by high deserts, deep canyons and "pygmy forests". These features can be found along the Warner Point Nature Trail, the highest elevation on the south rim of Black Canyon. Pinyon pine (Pinus edulis) and juniper trees dominate this forest type known as the "pygmy forest" due to its small stature. Pinyon pine is most common here, but 11 species of North American nut pines are found throughout the desert southwest.

Junipers often mingle with Pinyon pine in the unique climate and soils of this area. The most common Juniper species at the park is the Utah juniper (Sabina osteosperma). The pinyon and juniper woodlands have provided food, fuel, building materials and medicines to American Indians for thousands of years. Still today, the pygmy forest provides the delicious pine nut and firewood for people of all walks of life on the Colorado Plateau.

 

Black bear (Ursus americanus) between Gambel oak trees

NPS/D. Goodman

Gambel Oak Shrubland

Gambel oak (Quercus gambelii) is dense along the canyon rim. Wildflowers, grasses, shrubs, and serviceberry bushes intertwine with Gambel oak providing an abundant habitat for wildlife. Tuber-like roots called lignotubers cause the deciduous Gambel oak to form thickets. This unique feature is embedded in the trunk beneath the bark and just below the soil. A swollen lignotuber houses hundreds of buds ready to transform into leafy sprouts. Underground stems called rhizomes also hold dormant buds ready to sprout after fires or heavy browsing by wildlife.

The oak flat is a dense, brushy environment that provides cover for wildlife and their young. Oak acorns take a year to mature. Being rich in carbohydrates, fats, and proteins, they are on top of the wildlife food list.

Hike along the Oak Flat Trail or Uplands Trail to discover this forest type. Be on the lookout for mule deer, black bears, rodents, and other small mammals who forage in this zone.

The north-facing walls (right) of the canyon are less steep and have more vegetation than the south-facing walls (left).

NPS

Inner Canyon

Just below the canyon rim, an entirely different world unfolds. Deeply etched walls provide shade for plants that you would expect at higher elevations. Tiny rock gardens burst with wildflowers. North-facing slopes are home to Douglas-fir (Pseudotsuga menziesii), Colorado blue spruce (Picea pungens), and quaking aspen (Populus tremuloides).

The towering Douglas-fir has a mutual relationship with a fungus that dwells on the forest floor. This close connection creates a new root structure. Part fungus and part tree root, botanists call this mycorrhizae. Mycorrhizal roots are efficient in absorbing water, helping the trees during dry years. While the fungus is unable to make its own carbohydrates, it absorbs them from the tree, which creates its own food through photosynthesis. These roots even have an antibiotic effect against other dangerous parasitic fungi that attack tree roots.

Bighorn sheep (Ovis canadensis), once common on the Colorado Plateau, can still be occasionally sighted in the canyon. The steep, rugged terrain provides protection from predators. Look for Peregrine Falcon (Falco peregrinus), Canyon Wren (Catherpes mexicanus), and White-throated Swifts (Aeronautes saxatalis) while picking your way down a wilderness route to the Gunnison River.

Each side of the inner canyon is different. The south-facing wall of the canyon is extremely steep and sparsely vegetated. The north-facing wall is not as steep and often thick with vegetation, making the canyon appear as a lop-sided “V” shape.

This striking difference is mainly due to the amount of sunlight hitting the walls. This determines the amount of freeze-thaw erosion occurring on each wall. The continuous cycle of freezing and thawing water—expanding and contracting within the canyon walls—weakens rocks and causes them to break off or erode. Since the south-facing wall receives more direct sunlight, moisture evaporates quicker, and less freeze-thaw occurs. In contrast, the north-facing wall is in shadow much of the day. Water evaporates slower in the cool shade, causing more freeze-thaw and increased erosion. Water, in all its stages, helps to erode rocks and create more soil. With more soil, chances for a plant to take root increase. Roots help to break up rock and make soil as well.

 

Gunnison River

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Along the River

Creeks and rivers create wetland areas as they weave their way through the arid landscape of the Colorado Plateau. The Gunnison River has been cutting through the hard rock of the Black Canyon for about two million years. Today, its powerful waters continue to sculpt the smooth Precambrian rock.

Water loving plants cling to the edge of the river. Rainbow and Brown trout inhabit the river's chilly waters. Box elder (Negundo aceroides) and Narrow-leaf cottonwood (Populus angustifolia) crowd the riverbank. Occasionally, Ponderosa pine (Pinus ponderosa) tower over surrounding trees. In early summer, the Narrow-leaf cottonwood nears seeds that drift through the air and float downstream. Viable for only a day or two, they must locate a sunny place that is wet with sand or gravel to continue their life cycle.

The American Dipper (Cinclus mexicanus), in search of insects, flies over shallow rapids or runs along the riverbed with half-open wings. Presence of the North American river otter (Lontra canadensis) indicates a healthy river ecosystem.