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

Modal LRU: 43A01 - Okanogan Plateau

This LRU is composed predominantly of low to mid-elevation slopes of hills, outwash terraces, alluvial fans and escarpments. The soils tend to be loamy mollisols, entisols and inceptisols with mixed ash surfaces. Till, outwash and some residuum or colluvium from granitic rock are the dominant parent materials. Soil climate is mesic temperature regime and xeric moisture regime with average annual precipitation around 405 mm (16 inches).



Other LRU where occurring: 43A03 - Columbia-Colville Valleys
44A01 - Spokane-Rathdrum Outwash Plains
43A02 - Western Selkirk Highlands


Ecological Site Group Concept:

The data below describes the physiographic, climatic and other parameters for the Ponderosa Pine/ Dry Shrub, Grass ES group as a whole. This vegetation alliance is widespread so a Core Concept for each parameter is also described. See Appendix A for a finer division of the alliance based on selected soil features.
The bulk of this ecological site lies along the river valleys and slopes along the Columbia and Spokane Rivers. It’s dominated by a cover of bitterbrush with patches of ponderosa pine. Fire disturbance is the key factor in vegetation cover. With short fire intervals a pine/grass savanna exists, longer fire intervals allow bitterbrush and pine to establish and a pine/shrub savanna occurs. Extended fire intervals allow a pine woodland to develop and maintain a forest ecosystem.

Physiographic Features
This ecological site occurs mainly on forested glaciated hill or mountain back slopes, summits and foot slopes. It is found between 1,165 feet and 4,830 feet in elevation on southeast to northwest aspects. Slopes generally range from 15 to 40 percent, but can be found on slopes up to 80 percent.

Landscapes: Mountains, Foothills, Valleys

Landform: Mountain slopes, Hill slopes, Outwash terraces, Escarpments
Elevation
Total range: 355 – 1,470m
(1,165 to 4,830 feet)
Core Concept: 665-990m
(2,180 to 3,245 feet)
Slope (percent): Total range: 0-80
Core Concept: 15-40 Water Table Depth >200 cm
(>80 inches)

Flooding: Frequency: None
Duration: None
Ponding:
Depth (inches): 0
Frequency: none Duration: None

Aspect: Range: 90-205-320
Core Concept: 170-205-280

Climate

Climatic Features

During the spring and summer, a circulation of air around a high-pressure center brings a prevailing westerly and northwesterly flow of comparatively dry, cool and stable air into the region. As the air moves inland, it becomes warmer and drier which results in a dry season beginning in the late spring and reaching a peak in mid-summer. In the fall and winter, a circulation of air around two pressure centers over the ocean brings a prevailing southwesterly and westerly flow of air into the Pacific Northwest. This air from over the ocean is moist and near the temperature of the water. Condensation occurs as the air moves inland over the cooler land and rises along the windward slopes of the mountains or highlands. This results in a wet season beginning in October, reaching a peak in winter, then gradually decreasing in the spring.

The elevation within the LRU varies from approximately 1,000 feet in the lower river valleys to 3,500 feet over the Okanogan highlands. North-south ranges of mountains extending into southern British Columbia reach elevations of 4,000 to 5,000 feet within a few miles of the Okanogan River. The annual precipitation increases from 11 inches in the valley to 23 inches over some of the Plateau. Winter season snowfall varies from 30 to 70 inches. Both rainfall and snowfall increase in the higher elevations. Snow can be expected after the first of November and to remain on the ground from the first of December until March or April. The few snow survey reports available for elevation above 5,000 feet indicate six to eight feet of snow on the ground the first of April and four to five feet the first of May.

In January, the average maximum temperature is near 30° F and the minimum temperature is 15° F. Minimum temperatures from -10° to -20°F are recorded almost every winter and temperatures ranging from -25° to -42° F have been recorded in the colder valleys. In July, the average maximum temperature is 85° to 90° and the minimum temperature 45° to 50° F. Maximum temperatures reach 100° F on a few afternoons each summer and temperatures between 105° to 110° F have been recorded. Temperatures in the mountains decrease three to five degrees Fahrenheit with each 1,000 feet increase in elevation. The average date of the last freezing temperatures can be expected in the colder valleys by the first of September and before mid-October in the warmer areas.(from WRCC: Climate of Washington)
Mean Annual precipitation
Total Range: 260-680 mm
(10 to 27 inches)
Core Concept: 340-475 mm
(13 to 19 inches)

MAAT
Total Range 4.2-10.7 C
(40 to 51 F)
Core Concept: 7.0-8.6 C
(45 to 47 F)

Frost free period (days)
Total range: 90-140
Core Concept: 110-120

Climate Stations: CHIEF JOSEPH SUBSTN, TIMENTWA, Kettle Falls

Soil features

Representative Soil Features

This ecological site group is associated with several soil components. The most soil components can be grouped into three soil subgroups: Vitrandic Haploxerolls, Typic Xeropsamments, Vitrandic Argixerolls. Soils in this ecologic site are very deep to moderately deep with available water holding capacities mostly equal to or greater than 6.7 cm (in 100cm). Most of these soils have developed in over till, outwash and residuum and colluvium from granitic rock that has some influence from Mazama tephra. The soils are mostly well-drained to somewhat excessively drained. Surface textures include ashy fine sandy loam, ashy silt loam, stony and/or ashy loam.

Soil series occuring in this ES group:
Bong, Burnscreek, Dart, Donavan, Ewall, Georgecreek, Hellgate, Leiko, Northstar, Peka, Setill, Sinlahekin, Skanid, Spokane, Springdale, Thowson, Vanbrunt, Wadams, Whitestone, Winthrop


Parent Materials:
Kind: Volcanic ash, Till, Outwash, Residuum, and Colluvium
Origin: Granite, Rhyolite and Quartzite

Surface Texture: (<2mm fraction)
(1)Ashy Sandy Loam (2)Ashy Loam
Subsurface Texture Groups: Loamy, Sandy Surface Fragments


Appendix A

Examination of map unit components assigned to the Ponderosa Pine Dry Shrub, Grass alliance showed four possible subdivisions of the larger ecological group.

These are:
1) Warm Mesic Xeric Loamy Foothills/Mountainsides, ashy surface (Ponderosa Pine Dry Shrub, Grass)
2) Warm Mesic Xeric Loamy Foothills/Mountainsides, mixed ash surface (Ponderosa Pine Dry Shrub, Grass)
3) Warm Mesic Xeric Loamy Foothills/Mountainsides, low AWC subsoils (Ponderosa Pine Dry Shrub, Grass)
4) Warm Mesic Xeric Sandy Hill slopes and Outwash terraces (Ponderosa Pine Dry Shrub, Grass)


A.1 Warm Mesic Xeric Loamy Foothills/Mountainsides, ashy surface (Ponderosa Pine Dry Shrub, Grass)

Most commonly found in LRU 43A01 (Okanogan Plateau). Climate parameters were obtained from PRISM and other models for the area. Landscape descriptors are derived from USGS DEM products and their derivatives.

Physiographic Features
Landscapes: Mountains, Foothills, Canyons
Landform: sideslopes, foot slopes, toe slopes

Elevation (m): Total range = 555 to 1135 m
(1,820 to 3,725 feet)
Core Concept = 695 to 870 m
(2,280 to 2,855 feet)



Slope (percent): Total range = 0 to 65 percent
Core Concept = 15 to 35 percent

Water Table Depth (cm):
>200 cm
(>80 inches)

Flooding:
Frequency: None
Duration: None


Ponding:
Frequency: None
Duration: None


Aspect:
115-195-295
Core Concept: 145-195-215

Climatic Features
Frost-free period (days): Total range = 105 to 135 days
Core Concept = 110 to 120 days

Mean annual precipitation (cm): Total range = 370 to 540 mm
(15 to 21 inches)
Core Concept = 430 to 510 mm
(17 to 20 inches)



MAAT (C): Total range = 7.3 to 8.8
(45 to 48 F)
Core Concept = 7.8 to 8.1
(46 to 47 F)

Climate Stations: CHIEF JOSEPH SUBSTN



Representative Soil Features

This ecological subsite is associated with several soil series (e.g. Thowson, Wadams). The soils are Typic Vitrixerands. These soils have developed in Mazama tephra deposits over till, glaciolacustrine material, outwash and residuum and colluvium from granitic and metasedimentary rock. The tephra layers are important for forest productivity in that they retain large amounts of water compared to other parent materials, have high cation exchange capacity and high availability of organically bound plant nutrients. The soils range from moderately deep to very deep and have adequate available water capacity to a depth of 1 m. The soils are mostly well-drained.


Parent Materials:
Kind: Tephra (volcanic ash)
Origin: mixed
Kind: till,
Origin: unspecified

Surface Texture:
(1)Ashy Sandy Loam
(2)Ashy Coarse Sandy Loam

Fragment content of surface (hard fragments): 0 to 5 percent (median = 2%)

Subsurface Texture Group: Loamy
Fragment content of subsurface (25 to 100cm): 5 to 20 percent (median = 15%)
Most components lack surface fragments
Drainage Class: Well drained
Saturated Hydraulic conductivity: High
Soil Depth: >200 cm
Calcium Carbonate Equivalent (percent): 0
Soil Reaction (1:1 Water): 6.7 to 7.0
Available Water Capacity (total in 100cm): 13.06-14.53cm (median = 13.06cm)

A.2 Warm Mesic Xeric Loamy Foothills/Mountainsides, mixed ash surface (Ponderosa Pine Dry Shrub, Grass)

Most commonly found in LRU 43A03 (Columbia-Colville Valleys). Also found in areas of 43A01, 43A02. Climate parameters were obtained from PRISM and other models for the area. Landscape descriptors are derived from USGS DEM products and their derivatives.

Physiographic Features
Landscapes: Foothills, Valleys, Mountains
Landform: sideslopes, foot slopes, lake terraces, outwash terraces

Elevation (m): Total range = 355 to 1495 m
(1,165 to 4,900 feet)
Core Concept = 685 to 1,010 m
(2,245 to 3,310 feet)

Slope (percent): Total range = 0 to 80 percent
Core Concept = 15 to 40 percent

Water Table Depth (cm) : >200 cm
(>80 inches)

Flooding:
Frequency: None
Duration: None


Ponding:
Frequency: None
Duration: None


Aspect:
70-200-295
Core Concept: 120-200-240

Climatic Features
Frost-free period (days): Total range = 85 to 145 days
Core Concept = 105 to 125 days



Mean annual precipitation (cm): Total range = 265 to 735 mm
(10 to 29 inches)
Core Concept = 335 to 495 mm
(13 to 19 inches)


MAAT (C Total range = 4.4 to 10.3
(40 to 51 F)
Core Concept = 7.0 to 7.9
(45 to 46 F)

Climate Stations: none

Representative Soil Features

This ecological subsite is associated with several soil series (e.g. Bong, Burnscreek, Donavan, Georgecreek, Hellgate, Leiko, Peka, Setill, Sinlahekin, Spokane, Whitestone). The soil components can be grouped into: Vitrandic Haploxerolls, Vitrandic Argixerolls, Pachic Ultic Haploxerolls, and Ultic Haploxerolls. These soils have developed in mixed Mazama tephra, loess and other deposits over till, outwash, residuum and colluvium from granitic and metasedimentary rock, and glaciolacustrine material. The soils range from moderately deep to very deep and have adequate available water capacity to a depth of 1 m. The soils are mostly well-drained (~90% by area).

Parent Materials:
Kind: Tephra (volcanic ash) mixed with loess and other material
Origin: mixed
Kind: till, residuum and colluvium, outwash and alluvium
Origin: Granite, volcanic and sedimentary

Surface Texture:
(1)Ashy Loam
(2)Ashy Sandy loam
(3)Ashy Silt loam

Fragment content of surface: 3 to 25 percent (median = 10%)

Subsurface Texture Group: Loamy
Fragment content of subsurface (25 to 100cm): 4 to 70 percent (median = 25%)
Most components lack surface fragments
Drainage Class: Well drained (small areas Somewhat Excessively drained components)
Saturated Hydraulic conductivity: Moderately high to High
Soil Depth: Moderately deep to very deep
Paralithic contacts when present are at 84 to 140cm (median = 112 cm)
Densic contacts when present are at 66 to 124cm (median = 97 cm)
Calcium Carbonate Equivalent (percent): 0 to 5 percent (median = 0%)
Soil Reaction (1:1 Water): 5.5 to 7.4
Available Water Capacity (total in 100cm): 7.40-15.90cm (median = 9.04cm)

A.3 Warm Mesic Xeric Loamy Foothills/Mountainsides, low AWC subsoils (Ponderosa Pine Dry Shrub, Grass)

Most commonly found in LRU 43A01 (Okanogan Plateau). Also found in areas of 43A03. Climate parameters were obtained from PRISM and other models for the area. Landscape descriptors are derived from USGS DEM products and their derivatives.

Physiographic Features
Landscapes: Foothills, Mountains, Canyons
Landform: sideslopes, foot slopes, summits q

Elevation (m): Total range = 365 to 1475 m
(1,195 to 4,840 feet)
Core Concept = 705 to 1,015 m
(2,310 to 3,330 feet)

Slope (percent): Total range = 0 to 85 percent
Core Concept = 15 to 45 percent

Water Table Depth (cm) : >200 cm
(>80 inches)

Flooding:
Frequency: None
Duration: None


Ponding:
Frequency: None
Duration: None


Aspect:
90-208-315
Core Concept: 170-208-280

Climatic Features
Frost-free period (days): Total range = 85 to 150 days
Core Concept = 105 to 125 days



Mean annual precipitation (cm): Total range = 260 to 660 mm
(10 to 26 inches)
Core Concept = 335 to 465 mm
(14 to 18 inches)


MAAT (C Total range = 4.3 to 10.3
(40 to 51 F)
Core Concept = 6.9 to 7.8
(45 to 46 F)

Climate Stations: TIMENTWA

Representative Soil Features

This ecological subsite is associated with several soil series (e.g. Leiko, Northstar, Skanid, Vanbrunt, Whitestone). The soil components are Vitrandic Haploxerolls. These soils have developed in mixed Mazama tephra, loess and other deposits over till, outwash, residuum and colluvium from granitie, rhyolite, or quartzite. The soils range from moderately deep to very deep and have adequate available water capacity to a depth of 1 m. The soils are mostly well-drained (~90% by area).

Parent Materials:
Kind: Tephra (volcanic ash) mixed with loess and other material
Origin: mixed
Kind: till, residuum and colluvium, outwash
Origin: Granite, rhyolite, quartzite

Surface Texture: (<2mm fraction)
(1)Ashy Sandy Loam
(2)Ashy Coarse Sandy loam
(3)Ashy Loam

Fragment content of surface: 10 to 38 percent (median = 25%)

Subsurface Texture Group: Loamy
Fragment content of subsurface (25 to 100cm): 10 to 67 percent (median = 50%)
Most components lack surface fragments
Drainage Class: Well drained (small areas Somewhat Excessively drained components)
Saturated Hydraulic conductivity: Moderately High to High
Soil Depth: Shallow to very deep
Lithic contacts – 50-100 cm (median = 64)
Paralithic contacts when present are at 25 to 50cm (median = 46 cm)
Calcium Carbonate Equivalent (percent): 0
Soil Reaction (1:1 Water): 5.5 to 6.7
Available Water Capacity (total in 100cm): 3.71-7.18cm (median = 5.23cm)

A.4 Warm Mesic Xeric Sandy Hill slopes and Outwash terraces (Ponderosa Pine Dry Shrub, Grass)

Most commonly found in LRU 43A03 (Columbia-Colville Valleys). Also found in areas of 43A01, 44A01. Climate parameters were obtained from PRISM and other models for the area. Landscape descriptors are derived from USGS DEM products and their derivatives.

Physiographic Features
Landscapes: Foothills, Valleys
Landform: sideslopes, foot slopes, toe slopes q

Elevation (m): Total range = 365 to 1410 m
(1,195 to 4,625 feet)
Core Concept = 485 to 860 m
(1,590 to 2,820 feet)

Slope (percent): Total range = 0 to 60 percent
Core Concept = 1 to 25 percent

Water Table Depth (cm) : >200 cm
(>80 inches)

Flooding:
Frequency: None
Duration: None


Ponding:
Frequency: None
Duration: None


Aspect:
100-197-300
Core Concept: 115-197-245

Climatic Features
Frost-free period (days): Total range = 95 to 150 days
Core Concept = 110 to 130 days



Mean annual precipitation (cm): Total range = 265 to 635 mm
(10 to 25 inches)
Core Concept = 350 to 465 mm
(14 to 18 inches)


MAAT (C Total range = 4.8 to 10.7
(41 to 51 F)
Core Concept = 7.1 to 8.3
(45 to 47 F)

Climate Stations: Kettle Falls

Representative Soil Features

This ecological subsite is associated with several soil series (e.g. Bong, Dart, Ewall, Springdale, Winthrop). The soil components are Entic Ultic Haploxerolls, Typic Xeropsamments, Vitrandic Haploxerepts, and Vitrandic Haploxerolls. These soils have developed in mixed Mazama tephra, loess and other deposits over till, outwash, residuum and colluvium from granitie, rhyolite, or quartzite. The soils range from moderately deep to very deep and have adequate available water capacity to a depth of 1 m. The soils are mostly well-drained (~90% by area).

Parent Materials:
Kind: Tephra (volcanic ash) mixed with loess and other material
Origin: mixed
Kind: outwash and alluvium
Origin: Granite, or unspecified

Surface Texture: (<2mm fraction)
(1)Ashy Sandy Loam
(2)Ashy Coarse Sandy loam
(3)Coarse Sand
(4) Loamy Coarse Sand
(5) Loamy Sand

Fragment content of surface: 4 to 33 percent (median = 6%)

Subsurface Texture Group: Sandy
Fragment content of subsurface (25 to 100cm): 4 to 57 percent (median = 10%)
Most components lack surface fragments
Drainage Class: Somewhat Excessively and Excessively drained
Saturated Hydraulic conductivity: High to Very High
Soil Depth: very deep
Calcium Carbonate Equivalent (percent): 0
Soil Reaction (1:1 Water): 6.1 to 7.3
Available Water Capacity (total in 100cm): 4.50-7.37cm (median = 6.48cm)

Vegetation dynamics

Ecological Dynamics of the Site

This ecological site can be highly variable depending on fire occurrence and severity, and seed source of shrubs and pine. It is mainly located on foothills and side slopes next to the Columbia and Spokane Rivers. Through the ages it has had much human disturbance from Native Americans and from European settlement. Sites can be described as pine/savanna to pine/woodland depending on fire occurrence and occur throughout the landscape. Ponderosa pine and bitterbrush are the main cover species with Idaho fescue and bluebunch wheatgrass inversely proportionate to bitterbrush depending on fire disturbance. Soils will vary from sandy to loamy.

Ponderosa pine/shrub savanna will occur when fire intervals are 20 – 30 years allowing the bitterbrush to dominate the cover with scattered pine clusters. Frequent ground fires every 7-10 years will lead to a ponderosa pine/grass savanna with the bitterbrush killed by fire and bunchgrasses increasing. When fire occurrence is extended in the pine/shrub savanna pine cover increases with a mosaic of medium density pine stands with bitterbrush in the openings. Mix severity fires maintain this mosaic pine woodland/shrub savanna. In long extended fire periods a multi-story dense ponderosa pine woodland will establish with shrubs and grass in small percentages in the understory.


Relationship to Other Established Classifications:

United States National Vegetation Classification (2008) – A3446 Ponderosa Pine / Shrub Understory Central Rocky Mt. Forest & Woodland Alliance

Washington Natural Heritage Program. Ecosystems of Washington State, A Guide to Identification, Rocchio and Crawford, 2015 – Northern Rocky Mountain Ponderosa Pine Woodland and Savanna

Description of Ecoregions of the United States, USFS PN # 1391, 1995 - M332 Middle Rocky Mountain Steppe– Coniferous Forest -Alpine Meadow Province

Level III and IV Ecoregions of WA, US EPA, June 2010 - 15r Okanogan – Colville Xeric Valleys & Foothills

This ecological site includes the following USDA Forest Service Plant Associations: PIPO/PUTR, PIPO/PUTR-FEID, and PIPO/PUTR-PSSP. (Williams et. al. 1995)

Major Land Resource Area

MLRA 043A
Northern Rocky Mountains

Subclasses

• F043AY505WA–Warm Mesic Xeric Loamy Foothills/Mountainsides, ashy surface (Ponderosa Pine Dry Shrub, Grass) Pinus ponderosa / Purshia tridentata – Festuca idahoensis - Pseudoroegneria spicata
• F043AY506WA–Warm Mesic Xeric Loamy Foothills/Mountainsides, mixed ash surface (Ponderosa Pine Dry Shrub, Grass) Pinus ponderosa / Purshia tridentata – Festuca idahoensis - Pseudoroegneria spicata
• F043AY507WA–Warm Mesic Xeric Loamy Foothills/Mountainsides, low AWC subsoils (Ponderosa Pine Dry Shrub, Grass) Pinus ponderosa / Purshia tridentata – Festuca idahoensis - Pseudoroegneria spicata
• F043AY508WA–Warm Mesic Xeric Sandy Hill slopes and Outwash terraces (Ponderosa Pine Dry Shrub, Grass) Pinus ponderosa / Purshia tridentata – Festuca idahoensis - Pseudoroegneria spicata

Stage

Provisional