Ecological site group description

Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.

Physiography

Hierarchical Classification
Major Land Resource Area (MLRA): 007X – Columbia Basin

LRU – Common Resource Areas (CRA):
7.1 – Sandy Missoula Flood Deposits
7.2 – Silty Missoula Flood Deposits
7.3 – Dry Loess Islands
7.4 – Dry Yakima Folds
7.5 – Yakima Valley – Pleistocene Lake Basins

 
Site Concept Narrative
Diagnostics:
Very Shallow is a sparsely vegetated, low shrub-short grass, upland site on lithosols (very shallow soils generally less than 8 inches deep). Very Shallow sites are often found on windswept ridges and adjacent to exposed rocky ledges. Daubenmire writes that there appears to be no regular difference in either soils or vegetation between lithosols produced by glaciofluvial erosion or those or ridges where only wind and rain could have kept the basalt exposed.

Generally, there are sharp lines on the landscape between Very Shallow and the adjacent ecological site. One can stand with one foot on Very Shallow and the other foot on Stony or some other ecological site.

Occasionally the edge of very shallow is not so abrupt. This has been witnessed several times – less than 8 inches of soil depth has classic very shallow species, while 8-to 13 inches is a narrow band of Thurber needlegrass, and greater than 13 inches soil depth is a bluebunch wheatgrass site.

Usually, there are abundant rock and soil biotic crust cover, in the interspaces between plants. The lichen and moss play a critical role in water infiltration and resistance to erosion. On some but not all Very Shallow sites, are a few micro-pockets of taller vegetation in association with bedrock fracturing.

The most common reference community is stiff sagebrush-Sandberg bluegrass. Sandberg bluegrass is the short grass in all instances, but the low shrub component is variable. Stiff sagebrush is the predominant low shrub, but one to several different eriogonum species are present on some sites, instead of, or with stiff sagebrush. While there are minor ecological differences between these low shrubs, they are considered functionally equivalent for the purposes of this ecological site. These low shrubs have been combined into one site for several reasons: (1) the co-dominant short grass is Sandberg bluegrass in all cases, (2) Very Shallow has low plant productivity and extreme site limitations. (3) it is common to find three or more of these low shrub species on the same site, and (4) the hydrologic and watershed characteristics is similar regardless of low shrub.

According to Daubenmire, scabland sagebrush, locally known as stiff sagebrush, occurs on basalts with highly fractured parent material. Eriogonums occupy various parent materials and may dominate on gravelly soils and granitic parent materials.

Principle Vegetative Drivers:
The very shallow soil depth and the fracturing of, or the lack of fracturing in the underlying basalt bedrock drive the vegetative expression of this site. Deep-rooted steppe species do not grow on Very Shallow ecological site because of soil depth limitations. The fracture system accounts for variation in the low shrub component and the occasional mid-sized stature bunchgrass such as bluebunch wheatgrass or Thurber needlegrass.

INFLUENCING WATER FEATURES
A plant’s ability to grow on a site and overall plant production is determined by soil-water-plant relationships:
1. Whether rain and melting snow runs off-site or infiltrates into the soil
2. Whether soil condition remain aerobic or become saturated and become anaerobic
3. Water drainage and how quickly the soil reaches wilting point

The lower part of the soil profile of very shallow has high clay content. With winter rain and melting snow, water perches and creates saturated conditions.

In wet years during spring runoff, water runs on the surface of very shallow sites for a short period. Even more water runs beneath the surface to sites below. This increases the effective precipitation to the adjacent sites below.

Physiographic features:
The landscape is part of the Columbia basalt plateau. Very shallow sites occur on ridgetops, shoulders, benches, mesas, and hillslopes.

Physiographic Division: Intermontane Plateau
Physiographic Province: Columbia Plateau
Physiographic Sections: Walla Walla Plateau Section

Landscapes: Hills and plateaus
Landform: Hillslopes, ridges and structural benches

Elevation:
Range: 500 to 2,300 feet
Central tendency: 500 to 2,000 feet

Slope:
Range: 0 to 60 percent
Central tendency: 2 to 30 percent

Aspect: Occurs on all slopes.

Geology:
This is almost entirely underlain by Miocene basalt flows. Columbia River basalt is covered in most areas with as much as 200 feet of eolian, lacustrine, and alluvial deposits. This basin generally corresponds to the vast temporary lakes created by floodwaters from glacial Lakes Missoula and Columbia. Most of the fluvial and lacustrine sediments were deposited about 16,000 years ago, when an ice dam on the ancient Columbia River burst and when glacial Lake Missoula periodically emptied, creating catastrophic floods.

Climate

MLRA 007X is the lowest, driest and hottest portions of the entire Columbia River region and the sagebrush-bluebunch wheatgrass zone.

The climate across MLRA 007X is characterized by moderately cold, wet winters, and hot, dry summers, with limited precipitation due to the rain shadow effect of the Cascades. The average annual precipitation is mostly between 4 and 9 inches. Seventy to seventy-five percent of the precipitation comes late October through March as a mixture of rain and snow. Precipitation that comes after March is not as effective for plant growth. June through early October is dry. Freezing temperatures generally occur from late-October through early-April. Temperature extremes are -10 degrees Fahrenheit in winter and 110 degrees Fahrenheit in summer. Winter fog is variable and often quite localized, as the fog settles on some areas but not others.

Mean Annual precipitation
Range: 4 - 9 inches (6 - 10 inches zone)
Soil moisture regime is aridic.

Mean Annual Air Temperature
Range: 48 to 54 F
Central Tendency: 50 – 52 F
Soil temperature regime is mesic.

Frost-free period (days)
Total range: 135 to 210
Central tendency: 150 to 180
The growing season for very shallow is generally October through mid-November and March through mid-May.

Soil features

Edaphic:
The Very Shallow ecological site commonly occurs with rock outcrop, Loamy, and Stony ecological sites. Typical soil surface has about 40 percent rock, 10 to 20 percent bare ground, 10 to 20 percent biotic crust and 30 percent vegetative cover. Sites with less than 10 percent vegetative cover can be considered rock outcrop.

Very Shallow ecological site is sensitive to soil disturbances. When the Very Shallow ecological site is saturated and muddy, physical damage to the site, from vehicle ruts and hoof prints from cows, horses or deer for example, remain intact for many years.

Rocks or plants sitting on pedestals is called pedestaling. Two completely different processes cause the pedestaling. The first process is frost-heaving which pushes the plants upward and is evident across the entire site. The lower part of the soil profile has higher clay content. With winter rain and melting snow, water perches and creates saturated conditions. Freezing weather causes these saturated soils to frost-heave, and then during spring thaw, the site becomes muddy. The second pedestaling process is erosion which washes soil away from plants and rocks but only in water flow patterns.

The degree of pedestaling on the Very Shallow ecological site is quite variable. On many sites the soil surface is smooth and shows little to no evidence of pedestaling. But other sites show a high degree of pedestaling. The difference is presumed to be the amount of clay in the soil and the shrink-swell potential. In some years water runs on the surface and some erosion may occur.

If a site has a high degree pedestaling, the observer must determine whether this process is natural or human-induced (water running off cropland onto the rangeland for example).

REPRESENTATIVE SOIL FEATURES
This ecological site components are dominantly Xeric and Lithic taxonomic subgroup of Haplargids and Torriorthents great groups of the Aridisols and Entisols taxonomic orders. Soils are dominantly very shallow. Average available water capacity of about 0.8 inches (2.0 cm) in the 0 to 40 inches (0-100 cm) depth range.

Soil parent material is dominantly loess and colluvium over residuum.

The associated soils are Nevo, Schawana and similar soils.

Dominate soil surface is loamy fine sand to very cobbly loam.

Dominant particle-size class is loamy to loamy-skeletal.

Fragments on surface horizon > 3 inches (% Volume):
Minimum: 0
Maximum: 5
Average: 0

Fragments within surface horizon > 3 inches (% Volume):
Minimum: 0
Maximum: 35
Average: 15

Fragments within surface horizon ≤ 3 inches (% Volume):
Minimum: 0
Maximum: 30
Average: 20

Subsurface fragments > 3 inches (% Volume)
Minimum: 0
Maximum: 25
Average: 10

Subsurface fragments ≤ 3 inches (% Volume):
Minimum: 0
Maximum: 40
Average: 25

Drainage Class: Well to somewhat excessively drained.
Water table depth: Dominantly greater than 60 inches

Flooding:
Frequency: None

Ponding:
Frequency: None

Saturated Hydraulic Conductivity Class:
0 to 10 inches: Moderately high and high
10 to 20 inches: Moderately high and high

Depth to root-restricting feature (inches):
Minimum: 5
Maximum: 15

Electrical Conductivity (dS/m)
Minimum: 0
Maximum: 2

Sodium Absorption Ratio
Minimum: 0
Maximum: 0

Calcium Carbonate Equivalent (percent):
Minimum: 0
Maximum: 0

Soil Reaction (pH) (1:1 Water):
0 - 10 inches: 6.6 to 7.8
10 - 20 inches: 6.6 to 7.8

Available Water Capacity (inches, 0 – 40 inches depth)
Minimum: 0.4
Maximum: 1.5
Average: 0.8

Vegetation dynamics

ECOLOGICAL DYNAMICS:
Vegetation Dynamics:
Very Shallow produces about 75 to 200 pounds per acre of biomass annually.

The Very Shallow ecological site in MLRA 7 has at least four different variations on the low shrub-short grass theme for the Reference Community. Sandberg bluegrass is co-dominant in every variation:
1. Scabland sagebrush – Sandberg bluegrass
2. Scabland sagebrush / thymeleaf buckwheat / rock buckwheat – Sandberg bluegrass
3. Thymeleaf buckwheat – Sandberg bluegrass
4. Narrowleaf goldenweed (Stenotus s.) – Sandberg bluegrass

In the spring this site has a rich diversity of native annual and perennial forbs on most sites. Very Shallow ecological site supports edible species that have been an important food source for the Native Americans for many generations. Bitterroot and biscuitroot are the main species harvested for food.

Sandberg bluegrass is a shallow rooted, perennial bunchgrass, perfectly suited to Very Shallow sites. It has short leaves and a green to purplish panicle seed head. On most sites Sandberg is an understory grass, but on the Very Shallow ecological site it is the dominant grass. It begins growth in the fall then grows rapidly in the spring and sets seed before moisture is gone. Sandberg bluegrass is resistant to drought, grazing, trampling and fire.

In most years many bunchgrasses remain dormant in the fall. Sandberg bluegrass, however, greens up every year. And so, from late fall through winter and into early spring these Very Shallow ecological sites provide important green forage for deer, elk and upland birds. But these sites also dry up sooner than adjoining sites due to the very shallow soil depth. Grasses are dry from May through September.

Scabland sagebrush, locally known as stiff sagebrush, is low mounding and strongly scented with the characteristic sage odor. It is low and spreading with a conspicuously woody base. The base is often heaved from the soil by frost action. The trunk is very irregular, spreading above the base in a dense cluster of short, rigid, and rather brittle branches up to sixteen inches in length. Scabland sagebrush leaves are forked into three deep lobes like fingers. Unlike other sagebrush species, the leaves of scabland sagebrush are deciduous, and by fall, all the leaves have dropped. The ground under each plant will have a pile of dead leaves.

Fire: The vegetative cover is too low to carry fires, so these sites rarely burn
Grazing: In many pastures the Very Shallow ecological sites are not attractive to grazing animals and so are rarely if ever grazed.
Based on inherent protection from both fire and grazing, most Very Shallow ecological sites are stable and in excellent condition.

For more grazing management information refer to Range Technical Notes found in Section I Reference Lists of NRCS Field Office Technical Guide for Washington State.

Supporting Information

Associated Sites:
In MLRA 7 Very Shallow is associated with Sagebrush Steppe ecological sites (Shallow Stony Sand, Stony, Loamy, Cool Loamy, Dry Loamy, Calcareous Loam, Sandy, Sandy Loam) and Grassland Steppe ecological sites (Loamy and North Slope).

Very Shallow ecological site is also associated with rock outcrop. It is common for Very Shallow sites to transition back and forth with rock outcrop, Shallow Stony, Stony or other ecological sites.

Similar sites:
Very Shallow sites in MLRA 008X Columbia Plateau, MLRA 009X Palouse, and MLRA 006X East Slope of Cascades are quite similar.

Inventory Data References (narrative)
Data to populate Reference Community came from several sources: (1) NRCS ecological sites from 2004, (2) Soil Conservation Service range sites from 1980s and 1990s, (3) Daubenmire’s habitat types, and (4) ecological systems from Natural Heritage Program

State Correlation: Washington

References:

Boling M., Frazier B., Busacca, A., General Soil Map of Washington, Washington State University, 1998

Daubenmire, R., Steppe Vegetation of Washington, EB1446, March 1968

Davies, Kirk, Medusahead Dispersal and Establishment in Sagebrush Steppe Plant Communities, Rangeland Ecology & Management, 2008

Environmental Protection Agency, map of Level III and IV Ecoregions of Washington, June 2010

Miller, Baisan, Rose and Pacioretty, “Pre and Post Settlement Fire regimes in mountain Sagebrush communities: The Northern Intermountain Region

Natural Resources Conservation Service, map of Common Resource Areas of Washington, 2003

Rapid Assessment Reference Condition Model for Wyoming sagebrush, LANDFIRE project, 2008

Rocchio, Joseph & Crawford, Rex C., Ecological Systems of Washington State. A Guide to Identification. Washington State Department of Natural Resources, October 2015. Pages 156-161 Inter-Mountain Basin Big Sagebrush.

Rouse, Gerald, MLRA 8 Ecological Sites as referenced from Natural Resources Conservation Service-Washington FOTG, 2004

Soil Conservation Service, Range Sites for MLRA 8 from 1980s and 1990s

Tart, D., Kelley, P., and Schlafly, P., Rangeland Vegetation of the Yakima Indian reservation, August 1987, YIN Soil and Vegetation Survey


Site Development and Testing Plan
Future work, as described in a Project Plan, to validate the information in this Provisional Ecological Site Description is needed. This will include field activities to collect low, medium and high intensity sampling, soil correlations, and analysis of that data. Annual field reviews should be done by soil scientists and vegetation specialists. A final field review, peer review, quality control, and quality assurance reviews of the ESD will be needed to produce the final document.
Annual reviews of the Project Plan are to be conducted by the Ecological Site Technical Team.

Major Land Resource Area

MLRA 007X
Columbia Basin

Subclasses

• R007XY001WA–Very Shallow

Stage

Provisional

Contributors

Provisional Site Author: K. Guinn
Technical Team: R. Fleenor, W. Keller, K. Bomberger, K. Paup-Lefferts