Ecological site group R007XG130WA
Loamy
Last updated: 09/22/2023
Accessed: 12/22/2024
Ecological site group description
Key Characteristics
None specified
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): 7 – 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:
At 8 to 10 inches precipitation, Loamy ecological site is extensive on the landscape but much more limited at 6 to 7 inches precipitation. At lower elevation and lower precipitation, the Loamy ecological site may be found only on north aspects. Loamy does not occur at 4 to 5 inches precipitation.
Loamy ecological site is an upland site occurring on 20 inches and deeper non-skeletal loamy soils. Soils have a loamy surface texture and limited rock fragments (generally 10 percent or less) in the root-growing portions of the soil profile. Silt loam, fine sandy loam and sandy loam are most common, but a variety of soils and landforms are possible.
Fire-sensitive shrubs dominate the reference state overstory, while perennial, cool-season bunchgrasses and forbs fill the interspaces. The shrub layer is typically waist- to shoulder-high Wyoming sagebrush. The natural fire regime maintains a patchy distribution of shrubs. Depending on the time interval since the last fire, the shrub canopy can be as little 0 to 3 percent or as much as 40 percent. Bunchgrasses form two distinct layers. Bluebunch wheatgrass is the dominant bunchgrass in the top grass layer, while Sandberg bluegrass is the major grass of the lower grass layer.
The Loamy ecological site is the same as the Stony ecological site, except it is a little more productive. In some areas, the Stony ecological site is found on west-facing slopes and the Loamy ecological site on east-facing slopes.
Carey balsamroot is a common marker for MLRA 007X (less than 10 inches of precipitation).
Principle Vegetative Drivers:
The moderately deep to deep silt loam soils drive the vegetative expression of this productive site. Most species have unrestricted rooting on this site.
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 Loamy sites with water infiltrating into the soil. These sites are well drained and are saturated for only a short period.
Physiographic features:
The landscape is part of the Columbia basalt plateau. Loamy sites occur on broad ridges and plateaus, stream terraces, and east-facing hillslopes.
Physiographic Division: Intermontane Plateau
Physiographic Province: Columbia Plateau
Physiographic Sections: Walla Walla Plateau Section
Landscapes: Basin and hills
Landform: Terraces, hillslopes, foot slopes, nose slopes, outwash plains, plateaus
Elevation:
Range: 200 to 3,500 feet
Central tendency: 1,000 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 Wyoming sagebrush-bluebunch wheatgrass areas are both warmer and drier than grasslands or other sites with threetip sagebrush or bitterbrush (Daubenmire).
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 Loamy is mostly between 6 and 9 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. Winter fog is variable and often quite localized, as the fog settles on some areas but not others.
Mean Annual precipitation
Range: 6 - 9 inches (6 - 10 inch zone)
Soil moisture regime is aridic.
Mean Annual Air Temperature
Range: 46 to 54 F
Central Tendency: 48 – 52 F
Soil temperature regime is mesic.
Frost-free period (days)
Total range: 115 to 200
Central tendency: 140 to 170
The growing season for Loamy is March through June.
Soil features
Edaphic:
The Loamy ecological site commonly occurs with Stony, Very Shallow and Cool Loamy ecological sites.
REPRESENTATIVE SOIL FEATURES
This ecological site components are dominantly Xeric taxonomic subgroup of Haplocambids, Haplodurids, Haplocalcids great group of the Aridisols taxonomic orders. Soils are dominantly deep and very deep but can range to moderately deep. Average available water capacity of about 6.5 inches (16.5 cm) in the 0 to 40 inches (0 to 100 cm) depth range.
Soil parent material is dominantly eolian, loess and lacustrine deposits.
The associated soils are Burke, Kiona, Malaga, Neppel, Prosser, Royal, Sagehill, Sagemoor, Scooteney, Shano, Taunton, Warden, Wiehl and similar soils.
Dominate soil surface is silt loam to very fine sandy loam.
Dominant particle-size class is Fine-silty to 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: 15
Average: 2
Fragments within surface horizon ≤ 3 inches (% Volume):
Minimum: 0
Maximum: 15
Average: 10
Subsurface fragments > 3 inches (% Volume)
Minimum: 0
Maximum: 15
Average: 5
Subsurface fragments ≤ 3 inches (% Volume):
Minimum: 0
Maximum: 35
Average: 10
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 and high
10 to 40 inches: Moderately high and high
Depth to root-restricting feature (inches):
Minimum: 20
Maximum: Greater than 60
Electrical Conductivity (dS/m)
Minimum: 0
Maximum: 2
Sodium Absorption Ratio
Minimum: 0
Maximum: 2
Calcium Carbonate Equivalent (percent):
Minimum: 0
Maximum: 30
Central tendency: less than 15 within 15 inches of surface, can go higher with depth
Soil Reaction (pH) (1:1 Water):
0 - 10 inches: 6.1 to 9.0
10 - 40 inches: 6.1 to 9.0
Available Water Capacity (inches, 0 – 40 inches depth)
Minimum: 2.1
Maximum: 8.3
Average: 6.5
Vegetation dynamics
ECOLOGICAL DYNAMICS:
Vegetation Dynamics:
Loamy produces about 600 to 1200 pounds per acre of biomass annually.
Wyoming big sagebrush and bluebunch wheatgrass are at the core of the Loamy ecological site and warrant a degree of understanding.
Wyoming sagebrush in a long-lived, multi-branched, evergreen shrub. Size varies from three to five feet depending on soil and site conditions. Wyoming big sagebrush has a significant rooting system, composed of a two-part rooting structure with a primary deep taproot, and a shallow extensive network of finer roots that spread laterally. This rooting system allows Wyoming big sagebrush to survive in the hottest and driest portions of the sagebrush range by tapping into groundwater sources deep into the soil profile itself. This also allows Wyoming big sagebrush to be more competitive with bunchgrasses when the landscape positions and/or soils are less ideal for grass species to maintain the competitive advantage.
Bluebunch wheatgrass is a long-lived, mid-sized bunchgrass with an awned or awnless seedhead arranged is a spike. Bluebunch provides a crucial and extensive network of roots to the upper portions (up to 48 inches deep in soils with no root-restrictive horizons) of the soil profile. These roots create a massive underground source to stabilize the soils, provide organic matter and nutrients inputs, and help maintain soil pore space for water infiltration and water retention in the soil profile. The extensive rooting system of mid-sized bunchgrasses leave very little soil niche space available for invasion by other species. This drought resistant root can compete with, and suppress, the spread of exotic weeds.
The stability and resiliency of the reference communities is directly linked to the health and vigor of bluebunch wheatgrass. Further details about bluebunch physiology described later in the document. 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 we lose the bluebunch wheatgrass, 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 years was chosen for Wyoming 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 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 cover increases, and the more bunchgrasses decline. As sagebrush cover increases bluebunch wheatgrass cover declines but individual plants may persist underneath the sagebrush. 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. As bluebunch wheatgrass continues to decline, invasive species such as cheatgrass and knapweed colonize the site
3. 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 1–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 topgrowth: (1) so plants have enough energy 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:
Loamy is associated with other ecological sites in MLRA 7, including Stony, Cool Loamy, Dry Loamy, Sandy and Sandy Loam. It is also associated with Very Shallow, Loamy Bottom and Alkali Terrace.
Similar sites:
Loamy sagebrush in MLRA 8 Columbia Plateau is similar. Loamy grassland in MLRA 9 Palouse Prairie does not have sagebrush but is similar otherwise.
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
Stage
Provisional
Contributors
Provisional Site Author: Kevin Guinn
Technical Team: R. Fleenor, W. Keller, K. Bomberger, K. Lefferts
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