Life Zones and Plant Communities
Plants and animals tend to form interdependent and distinct communities in their particular climate. Because the range of elevation in the Grand Canyon region is so great, 7,500 feet, there are five distinct lifezones in the Grand Canyon. These are marked by indicator plants typical of each lifezone. Nature is rarely as simple as it seems, and so it is with lifezones. Each lifezone merges gradually with the one above, and the lifezones occur higher or lower on south and north facing slopes, but still the lifezone concept is useful to understand how wild communities relate to their environment.
Along the Colorado River, the permanent streams, and the more reliable springs, riparian (streamside) plants and animals find a home. Arrowweed, catclaw acacia, western honey mesquite, and several willows are common native plants. Tamarisk and camel thorn, non-native introduced plants, thrive in the riparian zone and form dense thickets. The Colorado River and its permanent tributary streams support native fish. In fact, tributary streams are often the last refuge of native fish driven out of the main river by the changes brought by the construction of Glen Canyon Dam upstream of the Grand Canyon. If there is enough water and floods don't disrupt their growth, large cottonwood trees take root. Seeps and springs create small riparian zones that harbor plants such as maidenhair fern and redbud trees.
Mohave and Great Basin Desert Life Zones
Away from the Colorado River, at the lowest elevations of the Grand Canyon, are the desert communities- Mohave Desert in the western Grand Canyon, and Great Basin Desert in the eastern canyon, where the lowest elevations are 1,500 feet higher. Typical plants are creosote, white bursage, brittlebrush, western honey mesquite, four-wing saltbush, rabbitbrush, blackbrush, and big sagebrush.
At intermediate elevations, pinyon pines and juniper trees grow in an open woodland commonly referred to as pinyon-juniper. One-seed juniper grows about 10 to 15 feet high, and single leaf pinyon pine, which favors slightly moister slopes, grows 15 to 30 feet tall. In the open spaces between the little trees, Mormon tea, Utah agave, narrowleaf yucca, winterfat, dropseed, banana yucca, needlegrass, snakeweed, Indian ricegrass, and big sagebrush are common.
At the highest Grand Canyon elevations, on protected north-facing slopes, and on both rims, 100-foot tall ponderosa pines create an open, park-like forest. Gambel oak, which is deciduous, and Arizona white oak, which is evergreen, are common, as is fescue, mountain mahogany, manzanita, elderberry, and creeping mahonia.
On the Kaibab Plateau and on north-facing terraces just below the rims, an alpine forest typical of southern British Columbia contains a beautiful mix of ponderosa pine, Douglas fir, white fir, Colorado blue spruce, Englemann spruce, mountain ash, and quaking aspen. Cinquefoils, asters, lupines, grasses, groundsels, yarrow, and asters grow on the forest floor during the short summers.
On the highest parts of the Kaibab Plateau, at nearly 9,000 feet, big galleta, Indian ricegrass, three awns, and blue and black gramma grasses cover expansive alpine meadows such as DeMotte Park.