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): 8 – Columbia Plateau

Land Resource Unit (LRU) – Common Resource Areas (CRA):
8.1 - Channeled Scablands
8.2 - Loess Islands
8.3 - Okanogan Drift Hills
8.4 - Moist Pleistocene Lake Basins
8.5 - Moist Yakima Folds
8.6 - Lower Snake and Clearwater Canyons
8.7 - Okanogan Valley


Site Concept Narrative:

In the upland setting ecological sites are often expansive, and thus, can be delineated and separated on aerial photos.

But in the landscape position of bottoms, basins and depressions this is rarely the case as small changes in soil chemistry, the water table and elevation or aspect results in significant changes in plant community composition. In short distances there are often big swings of available water holding capacity, and soils can go from hydric to non-hydric, or from saline-sodic to not. So, in bottoms, riparian areas and depressions, ecological sites and community phases occur as small spots, strips and patches, or as narrow rings around vernal ponds. And generally, in a matter of steps one can walk across several ecological sites. On any given site location, two or more of these sites often occur as a patchwork – Loamy Bottom, Alkali Terrace, Sodic Flat, Wet Meadow, Herbaceous Wetland and Riparian Woodland. These ecological sites may need to be mapped as a complex when doing resource inventory.


Diagnostics:
Wet Meadow sites have hydric soils and experience seasonal flooding. The water table drops 12-36 inches (approximation) during late spring and summer. Wet Meadow stands out because this ecological site is much wetter than adjacent upland sites. It is green in summer when the uplands are dry. This site is part of the lentic (standing water) ecosystem.

Wet Meadow occurs on non-saline or non-sodic bottoms, depressions, floodplains, channel shelves and terraces (first, stream, pond). This site also occurs as a zonal band near springs, lakes, perennial streams or intermittent streams with spring-fed reaches. Sites with perennial streams experience overbank flooding as a seasonal event in most years during late winter to early spring.

The soils are moderately deep to deep silt loam or sandy loam texture. Upper layer of soil profile is often deposited or captured from the current year’s flood. The soils have mottling or greying high in the profile, and thus, are hydric. There are also redoximorphic features (color patterns) in the upper 20 inches.

Loamy Bottom, Wet Meadow, and Wetland Complex ecological sites, all bottomland sites, are home to different groups of plant species. Upland and facultative upland species (UPL & FACU) are found on Loamy Bottom. Wet Meadow is largely facultative wetland species (FACW), while Wetland complex is dominated by obligate wetland species (OBL).

The reference community is largely grass-sedge-rush with a few forbs. Shrubs are virtually nonexistent. Tufted hairgrass, slender wheatgrass, northern reedgrass, bluejoint, clustered field sedge, smallwing sedge and Baltic rush are important grass and grass-like species. Cinquefoil, iris, camas and sagewort are common forbs.


Principle Vegetative Drivers:
The vegetative expression of Wet Meadow is driven by the magnitude and duration of flooding and groundwater discharge. The water table level during mid- and late-season determines the production potential. Wet Meadow is far more productive and any upland 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

Wet Meadow experiences seasonal flooding and discharging groundwater from nearby uplands which creates saturated soil conditions in late winter to early spring. By late summer the water table may be as shallow as 12” or as deep as 36”. (approximated)

Physiographic Features:
The landscape is part of the Columbia basalt plateau. This site is often associated with stream terraces and valleys having less than 3% gradient. Wet Meadow usually appears near bank full. This site also occurs as a zonal band near springs, lakes, perennial streams or intermittent streams with spring-fed reaches. Wet Meadow occurs on non-saline or non-sodic bottoms, depressions, floodplains, channel shelves and terraces (first, stream, pond). There are also Riparian Complex patches on draws, basins, depressions, and near ponds, lakes or springs. In the upland setting ecological sites are often expansive, and thus, can be delineated and separated on aerial photos. But in the landscape position of bottoms, basins and depressions this is rarely the case as small changes in soil chemistry, the water table and elevation or aspect results in significant changes in plant community composition. In short distances there are often big swings of available water holding capacity, and soils can go from hydric to non-hydric, or from saline-sodic to not. So, in bottoms, riparian areas and depressions, ecological sites and community phases occur as small spots, strips and patches, or as narrow rings around vernal ponds. Generally, in a matter of steps one can walk across several ecological sites. On any given site location, two or more of these sites occur as a patchwork – Loamy Bottom, Alkali Terrace, Sodic Flat, Wet Meadow, Wetland Complex and Riparian Complex. These ecological sites may need to be mapped as a complex when doing resource inventory.

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

Landscapes: Valleys, plateaus and hills
Landform: depressions, floodplains and drainageways

Elevation: Dominantly 1,000 to 3,600 feet
Slope: Total range: 0 to 5 percent
Central tendency: 0 to 3 percent
Aspect: Occurs on all aspects


Geology:
This MLRA is almost entirely underlain by Miocene basalt flows. Columbia River basalt is covered in many areas with as much as 200 feet of loess and volcanic ash. Small areas of sandstones, siltstones, and conglomerates of the Upper Tertiary Ellensburg Formation are along the western edge of this area. Some Quaternary glacial drift covers the northern edge of the basalt flows, and some Miocene-Pliocene continental sedimentary deposits occur south of the Columbia River, in Oregon.

A wide expanse of scablands in the eastern portion of this MLRA, in Washington, was deeply dissected about 16,000 years ago, when an ice dam that formed ancient glacial Lake Missoula was breached several times, creating catastrophic floods. The geology of the northernmost part of this MLRA is distinctly different from that of the rest of the area. Alluvium, glacial outwash, and glacial drift fill the valley floor of the Okanogan River and the side valleys of tributary streams. The fault parallel with the valley separates pre-Tertiary metamorphic rocks on the west, in the Cascades, from older, pre-Cretaceous metamorphic rocks on the east, in the Northern Rocky Mountains. Mesozoic and Paleozoic sedimentary rocks cover the metamorphic rocks for most of the length of the valley on the west.

Climate

The climate is characterized by moderately cold, wet winters, and hot, dry summers, with limited precipitation due to the rain shadow effect of the Cascades. Taxonomic soil climate is either xeric (12 – 16 inches ppt.) or aridic moisture regimes (10 – 12 inches ppt.) with a mesic temperature regime.

Mean Annual Precipitation:
Range: 10 – 16 inches
Seventy to seventy-five percent of the precipitation comes late October through March as a mixture of rain and snow. June through early October is mostly dry.

Mean Annual Air Temperature:
Range: 44 to 54 F
Central Tendency: 48 – 52 F
Freezing temperatures generally occur from late-October through early-April. Temperature extremes are 0 degrees in winter and 110 degrees in summer. Winter fog is variable and often quite localized, as the fog settles on some areas but not others.

Frost-free Period (days):
Total range: 90 to 200
Central tendency: 110 to 160
The growing season for Wet Meadow is March through mid-August or later depending on water table.

Soil features

Edaphic:
Wet Meadow has deep, well drained to poorly drained soils formed in loess. Wet Meadow commonly occurs adjacent to Alkali Terrace, Sodic Flat, Loamy Bottom Herbaceous Wetland and Riparian Woodland, ecological sites. It also occurs near upland sites such as Loamy, Stony, and Cool Loamy.


Representative Soil Features:
This ecological site components are dominantly Cumulic, Typic and Fluvaquentic taxonomic subgroups of Haploxerolls, Endoaquolls and Vitraquands great groups of the Mollisols and Andisols taxonomic orders. Soils are dominantly very deep but can be as shallow as moderately deep. Average available water capacity of about 7 inches (17.8 cm) in the 0 to 40 inches (0-100 cm) depth range.

Soil parent material is dominantly mixed alluvium and loess with possible mixed ash.

The associated soils are Aquolls, Cocolalla, Haploxerolls, Konert, Munset, Toppenish and similar soils.

Dominate soil surface is silt loam to gravelly fine sandy loam, with ashy modifier sometimes occurring as well.

Dominant particle-size class is fine to fine-loamy but includes limited ashy.

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

Fragments within surface horizon > 3 inches (% Volume):
Minimum: 0
Maximum: 10
Average: 1

Fragments within surface horizon ≤ 3 inches (% Volume):
Minimum: 0
Maximum: 30
Average: 5

Subsurface fragments > 3 inches (% Volume):
Minimum: 0
Maximum: 30
Average: 5

Subsurface fragments ≤ 3 inches (% Volume):
Minimum: 0
Maximum: 30
Average: 10

Drainage Class: Range from very poorly drained to moderately well drained.
Water table depth: 5 to 40 inches

Flooding:
Frequency: Rare to frequent

Ponding:
Frequency: None to frequent

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: 10

Sodium Absorption Ratio:
Minimum: 0
Maximum: 10

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

Soil Reaction (pH) (1:1 Water):
0 - 10 inches: 5.6 to 8.4
10 - 40 inches: 5.6 to 9.0

Available Water Capacity (inches, 0 – 40 inches depth):
Minimum: 2.6
Maximum: 9.6
Average: 7

Vegetation dynamics

Ecological Dynamics:
Wet Meadow produces about 6000-7500 pounds/acre of biomass annually.

Regarding saline-alkali soils Daubenmire (page 50) wrote, “It seems impossible to find areas where one can be confident that the vegetation has not been somewhat altered by domesticated animals.” The same is also true of meadows, riparian areas and wetlands. Some areas were also manipulated by tillage or other farming practices.

Plant production at the site level and individual species level can vary greatly depending on soil properties (depth to permanent water table) and growing conditions (timing and amount of precipitation, temperature). This site, because of the permanent water table, provides a very favorable soil-water-plant relationship.

Northern reedgrass and bluejoint are perennial rhizomatous, cool season grasses of the Calamagrostis genus. Tufted hairgrass is a low, dense cool season bunchgrass that prefers poorly drained soil. Clustered field sedge plants are often dioecious, bearing male or female flowers but not both. Smallwing sedge has a dense cluster of green or brown spikes packed tightly. Baltic rush is the most common of the rushes found in the Intermountain West as it occurs in both salt and freshwater habitats.

Wet Meadow is dominated by grasses, sedges and rushes in the reference community. Wet Meadow remains green late into the season and rarely burns.

Grazing by big game and livestock is a common disturbance that occurs to this ecological site. Grazing pressure can be defined as heavy to severe grazing intensity, or frequent critical period (vulnerable time of reproductive growth) grazing, or season-long grazing. As grazing pressure increases the plant community unravels in stages:

1. Tufted hairgrass, bluejoint and other grasses decline while Baltic rush, silverweed cinquefoil and clustered field sedge increase.
2. With further decline, invasive species such as Kentucky bluegrass, Canada bluegrass, reed canarygrass, redtop, quackgrass and Canadian thistle increase and become co-dominant. Eventually these invasive species dominate the site.
3. Eventually all the reference state species are replaced by invasive species.

In Washington, Wet Meadow communities provide habitat for a variety of upland and wetland wildlife species.


Supporting Information:

Associated Sites:
Wet Meadow is associated with other ecological sites in bottoms and basin areas of MLRA 8, including Loamy Bottom, Alkali Terrace, Sodic Flat, Wetland Complex and Riparian Complex. Wet Meadow is also associated with upland sites such as Loamy, Stony, and Cool Loamy.

Similar Sites:
There is no similar ecological site at this time.

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 008X
Columbia Plateau

Stage

Provisional