Physiographic features

This site occurs on alluvial fans, fan terraces, hills, and structural benches at elevations between 5,000 and 6,800 feet. Slopes typically range from 2 to 15%, but can be as high as 50%.

Table 2. Representative physiographic features

Climatic features

The climate of this site is characterized by hot summers and cool winters. Average annual precipitation ranges from 8 to 11 inches, with as much as 45% of the summer moisture coming as convective thunderstorms from July through October. June is typically the driest month during the growing season, while July and August are the wettest. Large fluctuations in daily temperatures are common, and precipitation varies greatly from month to month and from year to year.

Due to the lack of climate stations near this site, the climate section was developed using modeled climate data (PRISM) for soil map units correlated to this ecological site.

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

The soils are deep and loamy, usually with about 30-50% rock fragments in the soil profile. In some instances this site has fewer than 30% rock fragments in the soil, particularly in areas with droughty soil moisture conditions. These soils formed in alluvium and/or colluvium derived from sedimentary and igneous rock. Surface textures are loams, sandy loams or sandy clay loams, and rock fragements may or may not occur on the soil surface. The soil moisture regime is ustic aridic and soil temperature regime is mesic. Available water-holding capacity ranges from 2.5 to 4.0 inches of water in the upper 40 inches of soil.

This site has been correlated to soils in the following soil survey areas:

UT631 - Henry Mountains Area - Strych;
UT638 - San Juan County - Strych;
UT685 - Capitol Reef National Park - Abra, Beclabito, Begay family, Chilton, Clapper, Moab, Nihill family, Querencia, Saemo, Squawcave, Strych;

Table 4. Representative soil features

Animal community

--Livestock and Wildlife Grazing--

This site provides fair/poor grazing conditions for livestock and wildlife during fall, winter, and spring due to low availability of nutritious forage. This site also 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. Reseeding and/or restoration are difficult due to the extreme temperatures and variability in time and amount of precipitation. This site may occur in mule deer, desert bighorn sheep, pronghorn antelope, and elk habitat; however in many places the populations will be small and have little grazing impact on the site.

The plant community is generally an equal mixture shrubs and grasses. The dominant shrub specie, shadscale, provides good browse for mule deer and domestic sheep and goats in the winter, spring, and fall. It is a minor component of bighorn sheep and pronghorn antelope diets in the winter. Cattle will only utilize the fruits/seeds due to the spiny nature of the plant. Sub-dominant shrubs include Torrey jointfir, Bigelow sagebrush, and winterfat which provide good winter browse for cattle, sheep, goats, mule deer, bighorn sheep, elk, and pronghorn antelope. The presence of grasses including galleta and Indian ricegrass provide good spring and fall grazing conditions for cattle, horses, and sheep, bighorn sheep, and elk. 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.


--References--

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.

Hydrological functions

The soil is in hydrologic group b. The runoff curve numbers are 61 to 79 depending on the overall watershed condition.

Recreational uses

Recreation activities include hiking and hunting.

Wood products

None

Other information

--Poisonous/Toxic Plant Communities--

Toxic plants associated with this site include woolly locoweed and broom snakeweed. Locoweed is toxic to all classes of livestock and 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. Woolly locoweed 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”. 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 will generally only graze broom snakeweed when other forage is unavailable, typically in winter when toxicity levels are at their lowest.

Potentially toxic plants associated with this site include four-wing saltbush and some buckwheat species, which may accumulate selenium, but only when growing on selenium enriched soils. These plants, when consumed will cause alkali disease or chronic selenosis, which affects all classes of livestock (excluding goats). Typically animals consuming 5-50 ppm selenium will develop chronic selenosis and animals consuming greater than 50 ppm selenium will develop acute selenosis. Clinical signs include lameness, soughing of the hoof, hair loss, blindness, and aimless wondering. Horses tend to develop what is called a “bob” tail or “roached” main due to breakage of the long hairs.

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. Shadscale ecological sites occur on a wide variety of saline soils and thus invading plants will be tolerant of such conditions.

--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 semi-desert 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.
Due to the sparse plant cover and lack of fine fuels on this ecological site, historically shadscale dominated shrub communities were not influenced by fire. Fires were rare and non-existent; however increased presence of exotic annual grasses can greatly alter fire regimes due to the increase in fine fuels. The slow recovery period allows for cheatgrass invasions which can subsequently increase the fire regime. When fire does occur shadscale plants are killed and do not readily recover, except through re-establishment by seeds from adjacent unburned stands. Because shadscale seedlings lack spines, they are highly susceptible to browsing and thus grazing should be excluded for at least two years post fire.

--References--

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

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

George Cook
Jamin Johanson