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
7.5 – Yakima Valley – Pleistocene Lake Basins
 
Site Concept Narrative:
Diagnostics:
Dry Loamy ecological site is an upland shrub steppe site that occurs on the driest and hottest portion of MLRA 007X including elevations below 1,000 feet, precipitation less than 7 inches, or south-facing slopes. This site occurs on terraces and hillslopes. The soils are moderately deep to deep silt loam and very fine sandy loam textures and have limited rock fragments (generally 10 percent or less) in the root-growing portions of the soil profile.

Between 4 and 7 inches of precipitation, the Dry Loamy ecological site is often extensive. But above 7 inches of precipitation, the Dry Loamy ecological site is much more limited in extent to south facing slopes. The Dry Loamy ecological site is much more extensive than the Calcareous Loam ecological site.

Dry Loamy ecological site has low species diversity. Spiny hopsage is a marker for MLRA 007X and identifies the Dry Loamy ecological site.

Principle Vegetative Drivers:
High temperatures coupled with low precipitation or dry, south slopes drive the vegetative expression on Dry Loamy ecological site. Annual production in quite limited.

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 run off-site or infiltrate into the soil
2. Whether soil condition remain aerobic or become saturated and anaerobic
3. How quickly the soil reaches the wilting point

With adequate cover of live plants and litter, there are no restrictions on the Dry Loamy ecological site with water infiltrating into the soil. These sites are well drained.

Physiographic features:
The landscape is part of the Columbia basalt plateau. Dry Loamy ecological sites occur mostly on terraces, terrace escarpments and hillslopes.

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

Landscapes: Plateaus and hills
Landform: Terraces, hillslopes and structural benches

Elevation:
Range: 400 to 1,500 feet
Central tendency: 400 to 1,000 feet

Slope:
Total range: 0 to 30 percent
Central tendency: 2 to 15 percent

Aspect: Occurs on all aspects

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 Dry Loamy ecological site is generally in the driest and hottest portion of MLRA 007X (Benton, western Franklin, southern Grant and eastern Yakima counties.

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 between 4 and 10 inches. Seventy to seventy-five percent of the precipitation comes late October through March as a mixture of rain and snow. For drier sites and lower elevations, precipitation that comes after March is not as effective for plant growth. But at higher elevations and higher precipitation, April and May rains make the difference between average and great production years. 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.

Mean Annual precipitation
Range: 4 - 10 inches
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: 140 to 200
Central tendency: 150 to 180
The growing season for Dry Loamy is March through mid-May.

Soil features

Edaphic:
Dry Loamy ecological site commonly occurs with Calcareous Loam, Sandy Loam, Sandy and Sands ecological sites.

REPRESENTATIVE SOIL FEATURES
This ecological site components are dominantly Xeric and Aridic taxonomic subgroups of Haplargids, Haplocambids and Petrocambids great groups of the Aridisols taxonomic order. Soils are dominantly deep and deeper. Average available water capacity of about 6.0 inches (15.3 cm) in the 0 to 40 inches (0-100 cm) depth range.

Soil parent material is dominantly loess and alluvium derived from mixed sources over residuum.

The associated soils are Clenage, Matson, Scooteney and similar soils.

Dominate soil surface is silt loam to very gravelly loam.

Dominant particle-size class is coarse-silty or coarse-loamy.

Fragments on surface horizon > 3 inches (% Volume):
Minimum: 0
Maximum: 2
Average: 0

Fragments within surface horizon > 3 inches (% Volume):
Minimum: 0
Maximum: 25
Average: 5

Fragments within surface horizon ≤ 3 inches (% Volume):
Minimum: 0
Maximum: 30
Average: 15

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

Subsurface fragments ≤ 3 inches (% Volume):
Minimum: 0
Maximum: 35
Average: 20

Drainage Class: Dominantly well 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
10 to 40 inches: Moderately high

Depth to root-restricting feature (inches):
Minimum: Dominantly 40 inches
Maximum: Greater than 60

Electrical Conductivity (dS/m)
Minimum: 0
Maximum: 4

Sodium Absorption Ratio
Minimum: 0
Maximum: 5

Calcium Carbonate Equivalent (percent):
Minimum: 0
Maximum: 5

Soil Reaction (pH) (1:1 Water):
0 - 10 inches: 6.6 to 8.8
10 - 40 inches: 6.6 to 9.0

Available Water Capacity (inches, 0 – 40 inches depth)
Minimum: 2.3
Maximum: 8.3
Average: 6.0

Vegetation dynamics

ECOLOGICAL DYNAMICS:
Vegetation Dynamics:
Dry Loamy ecological site produces about 300 to 550 pounds per acre of biomass annually.

Stands of spiny hopsage and winterfat represent the northernmost outpost of species that are best represented in the vegetation of the Great Basin in Utah and Nevada. In the Great Basin spiny hopsage occurs in the transition between big sagebrush and shadscale.

The Dry Loamy ecological site has low species diversity. In the Reference State, Wyoming big sagebrush and spiny hopsage are the shrub layer while bluebunch wheatgrass and Sandberg bluegrass are layers two and three. Stands of Wyoming big sagebrush, spiny hopsage and Sandberg bluegrass are common (Daubenmire).

Dry Loamy ecological site tips easily to an Altered State and most Dry Loamy ecological sites in Washington have already crossed the threshold to communities dominated by cheatgrass and Russian thistle with an overstory of Wyoming big sagebrush and spiny hopsage. These sites are a fire waiting to happen.

Spiny hopsage is a one to four foot high salt desert shrub with small, paddle-shaped leaves. Stems are reddish brown with spiny, pointed ends. This shrub sheds its leaves and flowers by summer and becomes a woody gray thicket.

The stability and resiliency of the reference communities is directly linked to the health and vigor of bluebunch wheatgrass. More details about bluebunch physiology occur later. Research has found that the community remains resistant to medusahead invasion if the site maintains at least 0.8 plants per square foot of mid-sized bunchgrass (K. Davies, 2008). It is bluebunch wheatgrass that holds the system together. If bluebunch wheatgrass is lost, the ecosystem crashes or unravels.

The natural disturbance regime for grassland communities is periodic lightning-caused fires. The fire return intervals (FRI) listed in research for sagebrush steppe communities is quite variable. Ponderosa pine communities have the shortest FRI of about 10 to 20 years (Miller). The FRI increases as one moves to wetter forested sites or to dries shrub steppe communities. Given the uncertainties and opinions of reviewers, a mean of 75 years and a range of 50 to 100 was chosen for Wyoming big sagebrush communities (Rapid Assessment Model).

Some fires are spotty or do not burn hot enough to fully remove the sagebrush. Fires with light severity will remove less sagebrush and open smaller patches for grass and forb recovery, whereas the more severe fires will remove almost all the sagebrush and leave vast areas open to return to bunchgrass dominance. This is how the patchy distribution occurs. Rabbitbrush and horsebrush are sprouting shrubs and may also increase following fire.

The effect of fire on the community depends upon the severity of the burn. With a light to moderate fire there can be a mosaic of burned and unburned patches of sagebrush. Sagebrush can return to pre-burn conditions quickly. Bunchgrasses thrive as the fire does not get into the crown. With adequate soil moisture Idaho fescue and bluebunch wheatgrass can make tremendous growth the year after the fire. Other than impacting the sagebrush layer, the community is not affected.

A severe fire puts stress on the entire community. The sagebrush layer is completely removed. Spots or patches with heavy sagebrush are sterilized by the fire and must be seeded to prevent invasive species (annual grasses, tumble mustard) from totally occupying the site. Bluebunch wheatgrass and basin wildrye will have weak vigor for a few years but generally survive. Needle and thread is one native species that can increase via new seedlings.

The longer the site goes without fire and the more grazing pressure added, the more sagebrush and spiny hopsage cover increases, and the more bunchgrasses decline. As sagebrush cover increases bluebunch wheatgrass cover declines but individual plants may persist underneath the sagebrush. And, the dense sagebrush community phase is more vulnerable to outside pressures. Invasive species take advantage of available soil rooting spaces. The once extensive grass roots are largely absent. Soils are no longer receiving the organic inputs, and there is less surface cover by grass litter. Both water infiltration into the soil, and water percolation through the soil, are affected, leaving open soil space that is drier and more vulnerable to wind and water erosion, and invasion by undesirable species. Once these undesirable species have colonized, the site is at high risk of crossing a threshold if a disturbance such as fire were to occur.

Grazing is another common disturbance that occurs to this ecological site. Grazing pressure can be defined as heavy grazing intensity, or frequent grazing during reproductive growth, or season-long grazing (the same plant grazed more than once). As grazing pressure increases the plant community unravels in stages:
1. Bluebunch wheatgrass declines while Sandberg bluegrass, needle and thread and sagebrush increase
2. Needle and thread declines along with bluebunch wheatgrass
3. As the bunchgrasses continues to decline, invasive species such as cheatgrass and knapweed colonize the site
4. With further decline the site can become a sagebrush-cheatgrass community

Managing sagebrush steppe to improve the vigor and health of native bunchgrasses begins with an understanding of grass physiology. New growth each year begins from basal buds. Bluebunch wheatgrass plants rely principally on tillering, rather than establishment of new plants through natural reseeding. During seed formation, the growing points become elevated and are vulnerable to damage or removal.

If defoliated during the formation of seeds, bluebunch wheatgrass has limited capacity to tiller compared with other, more grazing resistant grasses (Caldwell et al., 1981). Repeated critical period grazing (boot stage through seed formation) is especially damaging. Over several years each native bunchgrass pasture should be rested during the critical period two out of every three years (approximately April 15–June 30). And each pasture should be rested the entire growing-season every third year (approximately March 1 – June 30).

In the spring each year it is important to monitor and maintain an adequate top growth:
(1) to replace basal buds annually, (2) to optimize regrowth following spring grazing, and (3) to protect the elevated growing points of bluebunch wheatgrass.

Bluebunch wheatgrass remains competitive if:
(1) Basal buds are replaced annually,
(2) Enough top-growth is maintained for growth and protection of growing points, and
(3) The timing of grazing and non-grazing is managed over a several-year period. Careful management of late spring grazing is especially critical

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.

In Washington, Wyoming sagebrush – bluebunch wheatgrass communities provide habitat for a variety of upland wildlife species.

Supporting Information:

Associated Sites:
Dry Loamy ecological site in MLRA 007X commonly occurs with Calcareous Loam, Sandy Loam, Sandy, Sands, Stony and Very Shallow ecological sites.

Similar sites:
There is no ecological site similar to Dry Loamy ecological site as it occurs in the driest and hottest portion of Washington state.

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

• R007XY163WA–Dry Loamy

Stage

Provisional

Contributors

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