Physiographic features

This site usually occurs on sand sheets and stabilized dunes atop mesas, structural benches, plateaus, and buttes. Slopes are typically between 0-15% and elevations typically range from 5500 to 7500 feet.

Table 2. Representative physiographic features

Climatic features

The climate of this site is characterized by warm summers and cold winters. Average annual precipitation ranges from 10-16 inches. June is typically the driest month, as well as April and May. About 35% of the precipitation occurs as cool-season moisture from January to March, while 40% of the moisture occurs as convective thunderstorms from July through October. Large fluctuations in daily temperature are common, and precipitation varies greatly from month to month and from year to year.

Modeled climate data (PRISM) was used to develop this section.

Table 3. Representative climatic features

Influencing water features

Due to its landscape position, this site is not typically influenced by streams or wetlands.

Soil features

These soils are typically deep fine sands derived primarily from eolian deposits over sandstone residuum. Very few rock fragments occur on the soil surface and throughout the soil profile. The soil moisture regime is aridic ustic and the soil temperature regime is mesic. These soils are well-drained to excessively-drained, with moderately rapid to very rapid permeability. They can be calcareous or non-calcareous, depending on the parent material. Water holding capacity ranges from 2.4 to 3.6 inches of water in the upper 40 inches of soil.

This site has been correlated to soil components in the following soil surveys:

UT629-Loa Marysvale Area - Royosa;
UT641-Washington County Area - Mespun;
UT643-San Juan County - Shedado;
UT685-Capitol Reef National Park - Mido family, Pinepoint;
UT686-Escalante Grand Staircase National Monument - Pinepoint, Tenneycanyon;

Table 4. Representative soil features

Animal community

--Livestock and Wildlife Grazing--

This site provides fair/good grazing conditions for livestock and wildlife during spring, summer, and fall when in good ecological condition due to accessibility and nutritious forage. However, this site often lacks natural perennial water sources, which can influence the suitability for livestock and wildlife grazing. Care should be taken to maintain the native perennial grasses and shrubs due to the poor suitability for re-seeding or restoring this site. The suitability for reseeding and/or restoration is poor due to the lack of precipitation at critical times and shallow soil characteristics. This site may occur in mule deer and desert bighorn sheep habitat; however in many places the populations will be small and have little grazing impact on the site.

The plant community is primarily shrubs, including mountain big sagebrush, green jointfir, broom snakeweed, and antelope bitterbrush, which provide browse for cattle, sheep, goats, mule deer, and bighorn sheep. The presence of grasses, including Indian ricegrass, blue grama and needleandthread, provide desirable grazing conditions for all classes of livestock and wildlife. Utah juniper and pinyon pine provide good cover for livestock and wildlife. Mule deer and goats may utilize these trees as forage. Forb composition and annual production depends primarily on precipitation amounts and thus is challenging to use in livestock grazing management decisions. However, forb composition should be monitored for species diversity, as well as poisonous or injurious plant communities which may be detrimental to livestock if grazed. Before making specific grazing management recommendations, an onsite evaluation must be made.

Recreational uses

Recreational activities include aesthetic values, hiking, and hunting.

Wood products

The site index for this site is 50. Wood is used for fenceposts and firewood.

Other information

--Poisonous/Toxic Plant Communities--

Toxic plant communities associated with this site include broom snakeweed, sand sagebrush, and freckled milkvetch. Broom snakeweed contains steroids, terpenoids, saponins, and flavones that can cause abortions or reproductive failure in sheep and cattle, however cattle are most susceptible. These toxins are most abundant during active growth and leafing stage. Cattle and sheep generally will only graze broom snakeweed when other forage is unavailable, typically in winter when toxicity levels are at their lowest. Sand sagebrush is toxic to horses, but not to other livestock and wildlife ruminants. This plant contains sesquiterpene lactones and monoterpenes, where toxic concentrations are greatest in the late fall and winter. Horses develop neurological signs and exhibit abnormal behavior, such as ataxia and the tendency to fall down, after eating sand sagebrush for several days. Freckled milkvetch is toxic to all classes of livestock and may be toxic to wildlife. This plant is palatable and has similar nutrient value to alfalfa, which may cause animals to consume it even when other forage is available. Milkvetch contains swainsonine (indolizdine alkaloid) and is poisonous at all stages of growth. Poisoning will become evident after 2-3 weeks of continuous grazing and is associated with 4 major symptoms: 1) neurological damage, 2) emaciation, 3) reproductive failure and abortion, and 4) congestive heart failure linked with “high mountain disease”.

Potentially toxic plants associated with this site include mountain and Wyoming big sagebrush, which contain sesquiterpene lactones and monoterpenes which have been suspected of being toxic to sheep. An experimental dosage of ¾ lbs of big sagebrush fed to sheep for three days was found to be lethal.

Russian thistle is an invasive toxic plant, causing nitrate and to a lesser extent oxalate poisoning, which affects all classes of livestock. The buildup of nitrates in these plants is highly dependent upon environmental factors, such as after a rain storm during a drought, cool/cloudy days, and soils high in nitrogen and low in sulfur and phosphorus, all which cause increased nitrate accumulation. Nitrate collects in the stems and can persist throughout the growing season. Clinical signs of nitrate poisoning include drowsiness, weakness, muscular tremors, increased heart and respiratory rates, staggering gait, and death. Conversely, oxalate poisoning causes kidney failure; clinical signs include muscle tremors, tetany, weakness, and depression. Poisoning generally occurs when livestock consume and are not accustomed to grazing oxalate-containing plants. Animals with prior exposure to oxalates have increased numbers of oxalate-degrading rumen microflora and thus are able to degrade the toxin before clinical poisoning can occur.

--Invasive Plant Communities--

Generally as ecological conditions deteriorate and perennial vegetation decreases due to disturbance (fire, over grazing, drought, off road vehicle overuse, erosion, etc.) annual forbs and grasses will invade the site. Of particular concern in semi-arid environments are the non-native annual invaders including cheatgrass, Russian thistle, kochia, halogeton, and annual mustards. The presence of these species will depend on soil properties and moisture availability; however, these invaders are highly adaptive and can flourish in many locations. Once established, complete removal is difficult but suppression may be possible.

--Fire Ecology--

The ability for an ecological site to carry fire depends primarily on the present fuel load and plant moisture content—sites with small fuel loads will burn more slowly and less intensely than sites with large fuel loads. Many plant communities in the Colorado Plateau may have evolved without the influence of fire. However a year of exceptionally heavy winter rains can generate fuels by producing heavy stands of annual forbs and grasses. When fires do occur, the effect on the plant community may be extreme due to the harsh environment and slow rate of recovery.

The pinyon and Utah juniper communities in the Colorado Plateau are unique. These sites have a natural occurring fire regime, but this is not understood very well due to the difficulty in reconstructing fire histories in these ecosystems. The difficulty results from a lack of living fire-scarred trees in this area. These trees can support stand-replacing fires, though historically, fires were likely a mixture of surface and crown fires with intensities and frequencies dependent on site productivity. Most research agrees that historic fire return intervals are at a minimum 100 years, indicating that fire may have not played an important role in community dynamics. Fires are more common when trees are stressed or dead due to drought and/or beetle infestations. Pinyon-juniper stands reestablish either by seeds dispersed from adjacent unburned patches or by unburned seeds found at the burn site. Continuous (every 20-40 years) burning of these ecological sites can result in shrub dominated communities, due to the relatively fast recovery of shrubs when compared to trees. If invasive annual grasses are allowed to establish fires may become more frequent, inhibiting the site’s ability to recover.

Other references

Knight, A. P. and R. G. Walter. 2001. A guide to plant poisoning of animals in North America. Jackson, WY: Teton NewMedia. 367p.

Mason LR, Andrew HM, Carley JA, Haacke ED. 1967. Vegetation and soils of No Man’s Land Mesa relict area, Utah. Journal of Range Management 20(1):45–9.

Relative Forage Preference of Plants for Grazing Use by Season: Plants commonly found in Major Land Resource Area D35 --The Colorado Plateau. 2007

Stubbendieck, J., S. L. Hatch, and C. H. Butterfield. 1997. North American range plants. Lincoln, NE: University of Nebraska Press. 501p.

USDA, Forest Service. 2007. Fire effects information: plant species life form. Available at http://www.fs.fed.us/database/feis/plants/index.html. Accessed 7 August 2007.

Contributors

Susanne Mayner