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

A PROVISIONAL ECOLOGICAL SITE is a conceptual grouping of soil map unit components within a Major Land Resource Area (MLRA) based on the similarities in response to management. Although there may be wide variability in the productivity of the soils grouped into a Provisional Site, the soil vegetation interactions as expressed in the State and Transition Model are similar and the management actions required to achieve objectives, whether maintaining the existing ecological state or managing for an alternative state, are similar. Provisional Sites are likely to be refined into more precise group during the process of meeting the APPROVED ECOLOGICAL SITE DESCRIPTION criteria.

This PROVISIONAL ECOLOGICAL SITE has been developed to meet the standards established in the National Ecological Site Handbook. The information associated with this ecological site does not meet the Approved Ecological Site Description Standard, but it has been through a Quality Control and Quality Assurance processes to assure consistency and completeness. Further investigations, reviews and correlations are necessary before it becomes an Approved Ecological Site Description.

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
7.4 – Dry Yakima Folds
7.5 – Yakima Valley – Pleistocene Lake Basins

Site Concept Narrative:
Diagnostics:
Cool Loamy ecological site in MLRA 007X is much more limited in extent than the Cool Loamy ecological site in MLRA 008X.
This site is confined to north to north-east facing slopes on Saddle Mountain and Frenchman Hills at elevations of 1500 to 2000 feet. Cool Loamy ecological site is also found on the MLRA 007X portions of Rattlesnake Hills, Horse Heaven Hills and Beazley Hills, again on north to northeast slopes. Below 8 inches of precipitation, the Cool Loamy ecological site may be virtually nonexistent even on north aspects.

This is an upland site occurring on 20 inches and deeper loamy soils. These sites occur most commonly on silt loam, sandy loam and stony loam soils.

Cool Loamy ecological site in MLRA 007X has less threetip sage, less Idaho fescue, but more bluebunch wheatgrass than Cool Loamy in MLRA 008X. The shrub layer is generally a mixture of Wyoming big sagebrush, threetip sagebrush, horsebrush and rabbitbrush. The cover of Wyoming and basin big sagebrush will depend on how long it has been since the site burned. Bluebunch wheatgrass dominates the herbaceous layer with Idaho fescue a minor to co-dominant species.

Carey balsamroot is a common marker for MLRA 007X (less than 9 inches of precipitation).

Principle Vegetative Drivers:
The vegetative expression of this productive site is driven by two factors: (1) moderately deep to deep soil depth provides unrestricted rooting for most species, and (2) the microclimate which allows the shift in major plant species. With higher elevations or northerly facing slopes this ecological site has cooler temperatures year-round and longer lasting snowpack than other MLRA 007X ecological sites. This site provides crucial water to the vegetation at the hottest time of the growing season allowing the ecological site more resilience when impacted by disturbances. Also, being wetter and cooler, Cool Loamy ecological site supports a denser plant cover than the Loamy ecological 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 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

Cool Loamy ecological site has cooler temperatures and longer lasting snow than other MLRA 008X ecological sites. Thus, this site supports a denser plant cover and provides water crucial to vegetation when it becomes hot.

Physiographic features:
The landscape is part of the Columbia basalt plateau. Cool Loamy sites are most commonly found on broad ridges, benches and plateaus, stream terraces, drier draw bottoms, north and northeast-facing hillslopes and in small basins

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

Landscapes: Basin and hills
Landform: Terraces, hillslopes, footslopes, nose slopes

Elevation:
Range: 220 to 3,500 feet
Central tendency: 1,500 to 2,000 feet

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

Aspect: Dominantly northern 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. Areas with threetip sagebrush and Idaho fescue when compared to Wyoming big sagebrush-bluebunch wheatgrass regions, are cooler from late-fall to early-spring (October through April), and has higher precipitation and precipitation-transpiration for five months (September, November, December, January and March) (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 for Cool Loamy ecological site is mostly between 6 and 10 inches. Seventy to seventy-five percent of the precipitation comes late October through March as a mixture of rain and snow. For Cool Loamy, March-May rains ensure good production and seed formation for Idaho fescue. 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 - 10 inches
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 Cool Loamy ecological site is March through June.

Soil features

Edaphic:
The Cool Loamy ecological site occurs with Loamy, Stony and Very Shallow ecological sites.

REPRESENTATIVE SOIL FEATURES
This ecological site components are dominantly Xeric taxonomic subgroup of Haplocambids great group of the Aridisols taxonomic orders. Soils are dominantly deep and very deep. Average available water capacity of about 7.0 inches (17.8 cm) in the 0 to 40 inches (0 to 100 cm) depth range.

Soil parent material is dominantly loess.

The associated soils are Adkins, Royal, Shano and similar soils.

Dominate soil surface is silt loam to very fine sandy loam.

Dominant particle-size class is coarse-silty.

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

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

Fragments within surface horizon ≤3 inches (% Volume):
Minimum: 0
Maximum: 10
Average: 2

Subsurface fragments > 3 inches (% Volume)
Minimum: 0
Maximum: 5
Average: 1

Subsurface fragments ≤ 3 inches (% Volume):
Minimum: 0
Maximum: 20
Average: 5

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 greater than 60 inches
Maximum: Greater than 60

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

Sodium Absorption Ratio
Minimum: 0
Maximum: 0

Calcium Carbonate Equivalent (percent):
Minimum: 0
Maximum: 15

Soil Reaction (pH) (1:1 Water):
0 - 10 inches: 6.6 to 8.4
10 - 40 inches: 6.6 to 8.4

Available Water Capacity (inches, 0 – 40 inches depth)
Minimum: 2.7
Maximum: 8.3
Average: 7.0

Vegetation dynamics

ECOLOGICAL DYNAMICS:
Idaho fescue is dominant on Cool Loamy ecological site in MLRA 008X. Not so in MLRA 007X, where Idaho fescue is at best codominant to subdominant.

Vegetation Dynamics:
Cool Loamy ecological site produces about 800 to 1200 pounds per acre of biomass annually.

On MLRA 008X Cool Loamy ecological sites, Idaho fescue and threetip sagebrush are dominant species. MLRA 007X is enough drier so that Cool Loamy ecological site is far more restricted on the landscape and Idaho fescue and threetip sagebrush are not as prominent in the plant community.

Compared to other upland ecological sites in MLRA 007X, Cool Loamy has more available soil moisture. This happens twofold: (1) there is more moisture (more spring rain, deeper snowpack, more fog), and (2) the precipitation is more effective (cooler temperatures, less runoff and less evaporation due to closer spacing of plants, and hence, more soil cover). Threetip sagebrush and Idaho fescue are especially linked to the additional soil moisture on this ecological site. The third dominant species in the Reference State, bluebunch wheatgrass, is not as linked to the additional soil moisture.

Threetip sagebrush is a short, shallow-rooted, evergreen shrub. Leaves are more deeply lobed than big sagebrush. Compared to big sagebrush, threetip sagebrush grows on sites that are moister or at higher elevations. Threetip sagebrush has a very slow growth rate, reaching a height of one foot after twenty years. In Washington threetip sagebrush generally sprouts following fire but it is not a big-time sprouter like rabbitbrush. It can take years for threetip sagebrush to get back to pre-burn conditions.

Idaho fescue is shorter and has a dense clump of shoots, while bluebunch wheatgrass is taller and is less dense. Both species are long-lived bunchgrasses. Bluebunch has an awned or awnless seed head arranged in a spike, while Idaho fescue has an awned seed head arranged in a panicle. The ratio of Idaho fescue to bluebunch wheatgrass plants on any site can vary due to aspect and elevation.

Both grasses provide 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 Idaho fescue and bluebunch wheatgrass. More details about bunchgrass physiology included 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). These two bunchgrasses hold the system together. If we lose either or both bunchgrass the ecosystem begins to unravel.

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 10-20 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 big sagebrush communities (Rapid Assessment Model). Threetip sagebrush-Idaho fescue areas should have a comparable fire return interval.

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 main species is mixed for the Cool Loamy site. Threetip sagebrush in Central Washington sprouts from lateral roots or the root crown following fire and bluebunch wheatgrass is fire tolerant. Threetip sagebrush is also a vigorous, wind-dispersed seeder and in many cases, after fire, threetip sagebrush will both re-sprout and disperse new seed from the surviving plants. Both species recover quickly. But Idaho fescue is much more sensitive to fire. Under windy conditions, a fire can burn into the crown of Idaho fescue, leaving behind “black holes” or nothing but ash. When a site loses Idaho fescue, the holes will be filled by vigorous native species or exotic weeds. Threetip sagebrush and bluebunch wheatgrass keeps the site resistant to change, while Idaho fescue makes the site more at risk.

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. Idaho fescue plants are very much at risk with a severe burn coupled with wind. The result can be “black holes” or ash two to three inches into the crown. The death of Idaho fescue plants creates holes in the community, and the opportunity for exotic species to colonize. Needle and thread is one native species that can increase via new seedlings.

Idaho fescue and bluebunch wheatgrass exhibit rapid tillering when there is light severity fires and favorable soil moisture. But, the longer the site goes without fire and the more grazing pressure added, the more threetip sagebrush cover increases and the bunchgrasses decline.

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 plants grazed more than once). As grazing pressure increases the plant community unravels in stages:
1. Idaho fescue declines while bluebunch wheatgrass and threetip sagebrush increase
2. Both Idaho fescue and bluebunch wheatgrass decline while threetip sagebrush and threadleaf sedge increase
3. With further decline invasive species colonize the site
4. The site can become a threetip sagebrush-threadleaf sedge 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. Given the opportunity Idaho fescue readily produces new seedlings while bluebunch wheatgrass plants rely principally on tillering. During seed formation, the growing points of bluebunch wheatgrass become elevated and are vulnerable to damage or removal. Idaho fescue has weak stems and is much more sensitive to grazing than bluebunch wheatgrass.

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 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 – July 15). And each pasture should be rested the entire growing-season every third year (approximately March 1 – July 15).

In the spring each year it is important to monitor and maintain an adequate top growth: (1) so plants have enough energy to replace basal buds annually, (2) to optimize regrowth following spring grazing, (3) to protect the elevated growing points of bluebunch wheatgrass, and (4) to avoid excessing defoliation of Idaho fescue with its weak stems.

These grasses remain 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, threetip sagebrush – Idaho fescue/bluebunch wheatgrass communities provide habitat for a variety of upland wildlife species.

Supporting Information:

Associated Sites:
Cool Loamy ecological site is associated with other sites in MLRA 007X including, Loamy, Stony and Very Shallow ecological sites.

Similar sites:
Cool Loamy ecological site in MLRA 007X has sagebrush with bluebunch wheatgrass and Idaho fescue. In MLRA 008X, the Cool Loamy ecological site has more Idaho fescue and threetip sagebrush.

North Aspect grassland in MLRA 8 Columbia Plateau, and North Aspect bunchgrass in
MLRA 9 Palouse Prairie do not have threetip sagebrush but otherwise are 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

• R007XY153WA–Cool Loamy

Stage

Provisional

Contributors

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