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): 6 – Cascade Mountains, East Slope

Land Resource Unit (LRU) – Common Resource Areas (CRA):
6.1 – North Cascades Subalpine/Alpine
6.2 – Pasayten/Sawtooth Highlands
6.3 – Okanogan Pine/Fir Hills
6.4 – Chelan Tephra Hills
6.5 – Chiwaukum Hills and Lowlands
 
Site Concept Narrative:
For MLRA 6 four ecological site descriptions (ESD) use Shallow Stony in the name:
1. Shallow Stony, prairie
2. Shallow Stony, 2,800 - 4,000 feet
3. Shallow Stony, 4,000 – 6,000 feet
4. Shallow Stony, 6,000 – 7,600 feet
The ESD below is for Shallow Stony 4000-6000 feet.


Diagnostics:
More than 80% of the landscape of MLRA 6 is forest. This site stands out because of a lack of trees.

Shallow Stony, 4,000-6,000 feet, is an upland site at mid-elevations in the 18-25” precipitation zone of MLRA 6. Soils are both shallow (10-20” deep) and stony to extremely stony. Soils have a stony or cobbly surface and rock fragments (35% or more) throughout the profile. Soil textures loam, silt loam and clay loam are most common. The soil surface is mostly bare soil, soil biotic crust or rock.

Shallow Stony, 4000-6000 feet is a sparsely vegetated grass-forb site. This ecological site exhibits species richness in a diverse array of grasses and forbs. In the reference state Idaho fescue, prairie junegrass and bluebunch wheatgrass are dominant, while native forbs are subdominant. Sedges, bluegrasses, other mid-grasses and shrubs are present but minor species on the reference community.


Principle Vegetative Drivers:
The soil (dominantly shallow soil depth and stones throughout the profile) and the elevation (4000-6000 feet) drive the vegetative expression of this site. The soil depth limits deep-rooted species, plus the soil depth and stones limit the water holding capacity in the profile. Thus, plant production is quite limited for Mountain Shallow Stony sites. The elevation plays an important role in the diversity and composition of species.

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

With adequate cover of live plants and litter, there are no restrictions on this ecological site with water infiltrating into the soil. In some years Shallow Stony sites can become saturated due to the shallow soil depth, but with good drainage would remain anaerobic for only a short period of time. This site has an extremely restricted water holding capacity, so plant production is quite limited.


Physiography of MLRA 6:
Most of MLRA 6 in Washington State is in the Northern and Middle Cascade Mountains. This mountainous area consists of sharp alpine summits with some higher volcanic cones to the west, and lower lying foothills to the east. Strongly sloping mountains and U-shaped valleys are dominant in the north, with eroded basalt plateaus more typical in the south. The East Slope of the Cascades is a transitional area between the moist, rugged Cascade Mountains to the west and the drier, lower lying Columbia Basalt Plateau to the east. MLRA 6 has some of the landforms typical of both mountains and plateaus.

Physiographic Division: Pacific Mountains
Physiographic Province: Cascade-Sierra Mountains
Physiographic Sections: Northern Cascade and Middle Cascade Mountains

Landscapes: Mountains
Landform: Side-slopes, shoulders, summits, benches

Elevation: Dominantly 3,500 to 6,500 feet
Central tendency: 4,000 to 6,000 feet
Slope: Total range: 15 to 90 percent
Central tendency: 30 to 60 percent
Aspect: Occurs on all aspects


Geology:
MLRA 6 consists of Pre-Cretaceous metamorphic rocks cut by younger igneous intrusives. Tilted blocks of marine shale, carbonate, and other sediments occur in the far north, and some younger continental, river-laid sediments occur around Leavenworth, WA. Columbia River basalt is dominant in the southern portion of the state. Alpine glaciation has left remnants of glacial till, debris, and outwash in the northern part of this MLRA.

Climate

The climate across MLRA 6 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 most of the East Slope of the Cascades is 16-50 inches. Seventy-five to eighty percent of the precipitation comes late October through March as a mixture of rain and snow. The lowest precipitation occurs along the eastern edge, then increasing with rising elevation to the west. Most of the rainfall occurs as low-intensity, Pacific frontal storms during the winter, spring and fall. Rain turns to snow at the higher elevations. All areas receive snow in winter. Summers are relatively dry. The East Slopes experience greater temperature extremes and receive less precipitation than the west side of the Cascades. The shortest freeze-free periods occur along the western edge and the northern end of this MLRA, which are mountainous. The longest freeze-free periods occur along the Columbia River Gorge.

Mean Annual Precipitation:
Range: 16-28 inches
Central tendency: 18 – 22 inches
Soil moisture regime is xeric

Mean Annual Air Temperature:
Range: 40 to 52 degrees
Central tendency: 42 to 48 degrees
Soil temperature regime is frigid and mesic

Frost-free period (days):
Total range: 70 to 140
Central tendency: 90 to 120
The growing season is early May through July.

Soil features

Edaphic:
Shallow stony, 4,000 – 6,000 feet, ecological site commonly occurs with Very Shallow, Stony South Aspect 4,000 – 6,000 feet and forest ecological sites. This ecological site is often associated with rock outcrop.


Representative Soil Features:
This ecological site components are dominantly Lithic taxonomic subgroup of Haploxerolls great group of the Mollisols. Soils are dominantly shallow. Average available water capacity of about 2.0 inches (5.1 cm) in the 0 to 40 inches (0-100 cm) depth range.

Soil parent material is dominantly loess and volcanic ash mixed with colluvium in the upper part of the soil over colluvium and residuum.

The associated soils are Johntom, Wynhoff and similar soils.

Dominate soil surface is gravelly loam to very stony ashy sandy loam.

Dominant particle-size class is loamy-skeletal.

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

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

Fragments within surface horizon ≤ 3 inches (% Volume):
Minimum: 5
Maximum: 30
Average: 15

Subsurface fragments > 3 inches (% Volume):
Minimum: 10
Maximum: 50
Average: 25

Subsurface fragments ≤ 3 inches (% Volume):
Minimum: 10
Maximum: 50
Average: 30

Drainage Class: Well drained
Water table depth: 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: 10
Maximum: 40

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

Sodium Absorption Ratio:
Minimum: 0
Maximum: 0

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

Soil Reaction (pH) (1:1 Water):
0 - 10 inches: 5.6 to 7.3
10 - 40 inches: 5.6 to 7.8

Available Water Capacity (inches, 0 – 40 inches depth):
Minimum: .7
Maximum: 2.7
Average: 2.0

Vegetation dynamics

Ecological Dynamics:
Shallow Stony, 4,000-6,000 feet produces about 300-600 pounds/acre of biomass annually.

Idaho fescue, bluebunch wheatgrass and prairie junegrass, three mid-sized perennial cool-season bunchgrasses, are at the core of Shallow Stony 4000-6000 feet and warrant a degree of understanding.

Idaho fescue, bluebunch wheatgrass and prairie junegrass, three mid-sized bunchgrasses, are at the core of this ecological site and warrant a degree of understanding. Idaho fescue is a shorter grass and has a dense clump of shoots with a more open awned panicle inflorescence. Prairie junegrass has a narrow and dense panicle inflorescence with a gap, while bluebunch wheatgrass has an awned or awnless inflorescence arranged in a spike.

These three grasses provide a crucial and extensive network of roots to the upper portions (up to 48” 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, bluebunch wheatgrass and prairie junegrass. As long as a good population of these three bunchgrasses is maintained, the ecological sites is stable. If we lose these grasses the ecosystem crashes or unravels.

Shallow Stony 4000-6000 feet is resistant to most natural disturbances and ecologically stable. Due to 35-75% surface rocks and limited forage, this ecological site is not attractive to grazing animals and so are rarely if ever grazed. The vegetative cover is too low to carry fire, so these sites rarely burn. Based on inherent protection from both fire and grazing, and the fact that invasive species are not very well adapted at this elevation range, most Shallow Stony sites at 4000-6000 feet are stable.

However, if this site does experience a major disturbance it is not resilient and may be extremely difficult to stabilize once altered. For example, vehicle traffic when the soil is saturated will leave ruts that remain for years to come.

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, bluebunch wheatgrass communities provide habitat for a variety of upland wildlife species.


Supporting Information:

Associated Sites:
Shallow Stony, 4,000-6,000 feet is associated with other ecological sites at mid-elevations in MLRA 6 including Stony South Aspect, 4000-6000 feet, Very Shallow and various forest sites.

Similar sites:
Within MLRA 6, Shallow Stony 2800-4000 feet and Shallow Stony 6000-7600 feet in MLRA 6 are similar. Other MLRAs also have Shallow Stony ecological sites.

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

Major Land Resource Area

MLRA 006X
Cascade Mountains, Eastern Slope

Stage

Provisional

Contributors

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