Life Zones

Juniper tree

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 park's south rim. Pinyon pine and juniper trees dominate this forest type known as the "pygmy forest" due to its small stature. Pinus edulis, Pinyon pine, is most common here, but 11 species of North American nut pines are found throughout the desert southwest.

Juniper always seems to mingle with the Pinyon pine thriving in the unique climate and soils of the area. While six species exist, here you are most likely to find Juniperus osteosperma. Junipers are commonly called cedars, but botanists tell us that true cedars are not native to North America.

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.

Gambel oak thicket

NPS photo by Lisa Lynch

OAK FLATS
Drive along the canyon rim and submerge yourself in a Gambel oak thicket. A kaleidoscope of wildflowers and grasses choke the roadsides. Serviceberry bushes and smaller shrubs intertwine with the Gambel oak providing an abundant habitat for wildlife.

Tuber-like roots called lignotubers cause the deciduous Gambel oak (Quercus gambelii) to form dense 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 bear dormant buds ready to sprout after fires or heavy browsing by wildlife.

 

Gambel oak leaves

NPS Photo by Lisa Lynch

The oak flat is a dense bushy environment that provides cover for animals and their young. The high tannin content of Gambel oak doesn't seem to bother the mule deer who flourish here, browsing year-round on its foliage. Though rarely seen, the shy black bear thrives in this thick forest taking advantage of the plentiful supply of rodents, berries and acorns.

Oak acorns take a year to mature. Being rich in carbohydrates, fats and proteins, they are on top of the wildlife food list. Serviceberry fruit is equally important. At least 60 species of wildlife are known to relish this purple berry!

Get in touch with this forest type on the Oak Flat Trail behind the South Rim Visitor Center.

 

 

NPS photo by Lisa Lynch

INNER CANYON
Just below the canyon rim, an entirely different world unfolds. Deeply etched walls provide a shady niche for plants that you would expect at higher elevations. Tiny rock gardens bursting with wildflowers invite you to explore this precarious chasm. Pockets of Douglas fir and aspen trees invade craggy slopes where snow lingers long into spring.

The towering Douglas fir (Pseudotsuga menziesii) 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 it "mycorrhizae". Mycorrhizal roots are efficient in absorbing water. This quality helps protect the tree during dry years. And 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, once common on the Colorado Plateau, can still be occasionally sited in the canyon. The steep rugged terrain provides them protection from predators like the mountain lion. Look for the rare Peregrine Falcon, the Canyon Wren, White-throated Swifts and Violet-green Swallows while picking your way through this twisted landscape on a backcountry route to the river.

 

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

NPS Photo by Lisa Lynch

Whether you view the canyon walls from an overlook, from one of the inner canyon routes, or even from the bottom looking up, you will probably notice a difference in its two walls. The south-facing wall of the canyon is extremely steep and is sparsely vegetated while the north-facing wall is not as steep and often thick with vegetation, making the canyon look somewhat like a lop-sided “V”. Basically, the rocks on one side of the canyon are being broken up or eroded more quickly than the rocks of the other side. This differential erosion occurs with the help of water, plants and the sun.

The striking difference between the canyon walls is mainly due to the amount of sunlight hitting these walls, which in turn 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 the rocks, and causes them to break off or erode. Since the south-facing wall receives more direct sunlight throughout the day, any moisture that falls there quickly evaporates. Without any moisture, freeze-thaw erosion is less likely to take place. In contrast, the north-facing wall is in shadow much of the day. Water evaporates much slower in the cool shade. The water that remains on the north-facing wall freezes and thaws throughout the winter, which increases the erosion that takes place.

Water, in all of its stages, helps to break rocks on the wall which in turn helps make more soil. With more soil, chances for a plant to take root increase. Roots help to break up rock and make soil as well. So, both the increased freeze-thaw erosion and increased vegetation on the north facing wall of the canyon have caused the rocks to erode at a quicker rate than the rocks on the south facing wall. This contributes to the lop-sided “V’ appearance of the Black Canyon.

 

Gunnison River at Red Rock Canyon

NPS photo by Lisa Lynch

ALONG THE RIVER
Water is the breath of life in the arid lands of the west. Creeks and rivers create ribbons of wetlands as they weave their way through the colorful and rugged tapestry of the Colorado Plateau. They carve through hidden layers of geologic history telling us of times long past: ancient oceans, windswept deserts and violent volcanic eruptions.

The Gunnison River has been cutting through the hard rock of the Black Canyon for about 2 million years. Today its powerful waters continue to sculpt the smooth Precambrian rock.

Water loving plants cling to the edge of the river. Trophy size Rainbow and Brown trout inhabit the river's chilly waters.

Chokecherry, Boxelder and Narrowleaf cottonwood crowd the riverbank. Often confused with willows, the Narrowleaf cottonwood (Populus angustifolia) provides vast stores of pulpy bark for the beaver to feed on. In early summer, its cotton bearing seeds drift through the air and float downstream. Viable for only a day or two, they must locate a sunny place that is wet and sandy or gravelly to continue their life cycle.

Watch for the unusual antics of the American Dipper. In search of insects, this chubby grey bird can be seen flying over the shallow rapids, or diving in the deeper waters and running along the riverbed with half open wings.