Riparian areas are formed through interactions between soil, water and vegetation. Although easily recognized by their green trees and vegetation, these areas require permanent water to support the many plants and animals found only in these areas.
Water sources for riparian areas may not always be visible. Sometimes surface water is present as ponds, seeps or running streams, while other sources may be far underground.
In Paria Canyon, riparian areas vary greatly in appearance and are located along streams, "dry" washes, benches and cliffs. Differences between riparian areas are due to various soil types, amount of flooding, and distance to water both above and below ground. For instance, riparian areas near the confluence of Buckskin Gulch and Paria Canyon are fairly unique, with their tall, fragile benches and terraces, and graceful ash and box elder trees. These communities are very different from the cottonwood or willow groves of the lower canyon, or even the primitive horsetail communities found along the stream.
Upon closer inspection of a riparian area, certain patterns of vegetation, soil, and water can be seen. In most places through Paria Canyon, three different zones or bands of riparian vegetation communities run parallel along each side of the river.
Directly adjacent to the water grows more aquatic-type plants like cattails, common reed, sedges, rushes, and horsetails. Small cottonwood, willow and ash seedlings also struggle for a foothold where frequent flooding scours away most before reaching maturity. This wet zone can be narrower than one-foot wide and must remain moist all year.
Adjacent to the wet zone, in drier soils farther from the stream, grows woody vegetation which has survived the repeated flooding. Young Gooding and coyote willows, cottonwood, ash, tamarisk, and seep-willow continue to grow from seedling to sapling, but stay small enough to bend with the strong flooding waters. This zone is referred to as the regeneration site because some of these trees will survive to produce the next generation of mature canopy.
Beyond this regeneration site, slopes or terraces usually form where soil moisture and flooding decrease considerably. Older trees grow strong and tall, creating the shade and cover that is precious to both wildlife and recreationists. Severe flooding, occurring every few years, repeatedly carves high terrace sites, where most mature groves and campsites remain safe. Soil, water and other conditions determine which types of communities will grow, whether it will be cottonwood, willow, ash, or tamarisk dominant. These terraces become the fringes between riparian and desert uplands, often sharing vegetation like rabbitbrush, Indian ricegrass, arrowweed, and sand dropseed.
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The unique ecology of riparian areas demands that they constantly change as a result of river flows and flooding. Wet site vegetation will eventually dry, becoming regeneration sites as the river floods, changes course, or catches sediment. New terraces are cut by the river, removing some riparian sites, and, over time, creating others. In any particular location, one or more of these riparian sites may exist, depending on how recent flooding may have occurred, soil/moisture conditions, or even types of uses and impacts.
With every mature cottonwood or other tree naturally placed high on some terrace or cliff, remember its history of life. Each tree had to be planted by flood waters during just the right temperature and season, had to be nurtured through seedling stages with prolonged moisture, and had to survive alternate years of drought and flooding to exist. The flooding potential needed to revive some of these mature terraces and groves, which are popular camping sites and critical habitat for wildlife, can take 25 to 100 years.
Thus it becomes apparent how amazing, yet fragile, riparian ecosystems can be. Managed improperly, activities such as recreation, livestock or wildlife use, or changes in river flow can disrupt the balance of soil, water and vegetation, sometimes having long-term effects. As you travel through Paria Canyon and it tributaries, notice how the individual riparian sites change, both within and between similar areas. See how many plants you can identify, which give clues to their soil and water conditions. Yet be careful to minimize trails and "Leave No Trace" to help maintain a proper functioning riparian area.
Riparian Field Guide
|Commonly grows in patches in or along the stream. Well-known marsh plant with its long, straight leaves, tall stout stem, and dark brown seed head which produces "clouds of cotton." Roots were ground into flour by Native Americans.|
|This is a very primitive plant remaining much the same as it did in prehistoric times. One of its common names, scouring rush, comes from the silica in the plant, which gives it a "sandy" feeling. It was used to scour pans. The horsetail comes in two forms. One is bushy and looks like a horse's tail, while the other is a straight stalk with segments.|
|These are primitive grass-like plants which grow in or next to water. There are many different types, but generally sedges have triangular stems and rushes have round stems. Many have no leaves, but thread-like stems with one or more small- coned flowers on the top. Others have long strong leaves and tufts of pale flowers.|
|This plant looks somewhat similar to cattails, but has a jointed stem and pale bushy seedheads. It commonly grows from six to eight-feet tall, sometimes growing along the ground like a root.|
|Also known as sandbar willow, this bushy willow typically grows in clumps along river banks and floodplains. Commonly six to 12-feet tall with silver-green leaves and flowering catkins.|
|This large majestic tree often reaches 50 to 100 feet in height, forming the mature groves and desirable campsites found on high terraces. Its large triangular shaped leaves make this tree very noticeable as seedlings along the streamside. Common to southwest rivers, cottonwoods are known for their beautiful displays of fall color, similar to their cousins, the aspen and willow.|
|The largest native willow in Arizona, this tall, rough trunked tree is commonly associated with cottonwoods on higher terraces. It has long, narrow leaves, discernable from the coyote willow by its tiny sawtooth edge and greener color.|
|Also known as salt cedar, this dense shrub or tree is abundant in many rivers of the southwest deserts. Brought into the country in the 1800s, this tree has become an undesirable invader. Tamarisk has feathery foliage with tiny scale-like leaves, which are deciduous and drop in the fall. Thousands of spiked pink flowers dust the trees during spring bloom.|
|Also known as baccharis, this tall bush closely resembles a willow. The leaves, however, are evergreen, dark green, and resinous with prominent veins leading to small "nodes" along the edge. It requires moist soil conditions and is rarely found very far from water. Several different varieties may be seen, but most have rough wood stems and tufts of yellow ray flowers.|
|This large shrub can be found along the edges of the riparian zone. Sometimes taller than six feet, this plant is yellow-green in color with small yellow or white flowers. It has a pungent smell and oozes a milky substance when stems are broken.|
|Arrowweed gets its common name from the straight, light woody stems used by Native Americans for arrow shafts. It has small fuzzy grey-green leaves and purple flowers and prefers drier terrace soils.|
|A picturesque grass with lacy seedheads and tiny dark kernels which can be ground into flour. Tall, dark green, wire-like leaves grow in sandy soils of the upland and riparian zones.|
|Normally this tree has five to seven, long, oval leaves along the stems. Sometimes growing over 20-feet high, this tree can often be seen on rocky cliffs and high terraces. It displays yellow colors in fall.|
|A member of the maple family, the boxelder tree has the same characteristic three-leaf stem. It is often found in cooler locations of the canyon such as Buckskin Gulch and Wrather Canyon.|
Vermilion Cliffs National Monument
Monument Manager: Wayne Monger, Acting
345 E. Riverside Drive
St. George, UT 84790-6714
Hours: 7:45 a.m.-5:00 p.m. Monday through Friday
10:00 a.m.-3:00 p.m. Saturday