Natural Resources
Conservation Service
Ecological site R043AY509ID
Loamy Floodplains
23-25" PZ Mesic
Clearwater Canyons
Last updated: 10/15/2020
Accessed: 04/21/2026
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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.
MLRA notes
Major Land Resource Area (MLRA): 043A–Northern Rocky Mountains
Description of MLRAs can be found in: United States Department of Agriculture, Natural Resources Conservation Service. 2006. Land Resource Regions and Major Land Resource Areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296.
Available electronically at: http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/ref/?cid=nrcs142p2_053624#handbookLRU notes
Major land resource area (MLRA): 043A-Northern Rocky Mountains
Modal LRU – 43A08 Clearwater Canyons
This LRU is composed predominantly of low to mid elevation foothills, structural benches, valleys, flats, mountain slopes and ridges. The soils tend to be loamy argixerolls. Volcanics are the dominant parent materials, along with occasional granite and other intrusives. Soil climate is a mesic temperature regime and xeric moisture regime with average annual precipitation around 675 mm (27 inches).Classification relationships
This ES fits into the National Vegetation Standard’s Rocky Mountain-Great Basin Riparian Shrubland Group (Compare to previous Idaho range sites: R009XY031ID, STONY RIPARIAN POBAT-ALNUS/ELYMU; R009XY032ID, RIPARIAN DECA5-CAREX; R009XY033ID, STONY BOTTOMLAND SYAL/PSSP6)
Ecological site concept
This ES is found on somewhat poorly drained to well drained, loamy sites on floodplains. A water table can be present but is usually not within 75 cm of the surface during the May-Oct period. They have mesic temperatures and a plant community that varies from riparian woody species to sedges and grasses. They are Riparian woodlands and shrublands found on canyon floors of the Ponderosa Pine Zone. These riparian areas are associated with all streams at and below lower treeline, including permanent, intermittent and ephemeral streams with woody riparian vegetation.
Table 1. Dominant plant species
Tree (1) Populus balsamifera ssp. trichocarpa
(2) Crataegus douglasiiShrub (1) Salix
(2) Philadelphus lewisiiHerbaceous (1) Galium trifidum
(2) Elymus glaucusPhysiographic features
This ecological site occurs mainly on floodplains and stream terraces in canyons. Parent materials are alluvium from basalt.
Landscapes: Canyonlands, plateaus
Landforms: Floodplains, stream terraces
Elevation:
Total range = 265 to 840 m
(870 to 2,755 feet)
Central tendency = 350 to 575 m
(1,150 to 1,885 feet)
Slope (percent):
Total range = 0 to 4 percent
Central tendency = 0 to 2 percent
Water Table Depth: 53 - >200 cm
(21 - >80 inches)
Flooding:
Frequency: none - occasional
Duration: None - long
Ponding:
Frequency: None
Duration: None
Aspect: NATable 2. Representative physiographic features
Landforms (1) Canyonlands > Flood plain
(2) Canyonlands > Terrace--stream or lake
Flooding duration Brief (2 to 7 days) Flooding frequency Occasional Elevation 1150 – 1885 ft Slope 0 – 2 % Water table depth 47 in Aspect Aspect is not a significant factor Table 3. Representative physiographic features (actual ranges)
Flooding duration Long (7 to 30 days) Flooding frequency None to occasional Elevation 870 – 2755 ft Slope 0 – 4 % Water table depth 21 – 0 in Climatic features
The climate of this portion of the MLRA is controlled by a combination of large-scale and small-scale factors. The large-scale factors here include latitude, relative position on the North American continent, prevailing hemispheric wind patterns, and extensive mountain barriers. Small-scale or local factors include the topographic setting and position (valley, slope, or ridge location), as well as orientation or aspect, and vegetative cover. Elevation may cover various scales. Broadly, the climate is transitional between a northern Pacific coastal type and a continental type. The Pacific influence is noted particularly by the late autumn and winter maximum in cloudiness and precipitation; also in the relatively moderate average winter temperatures, compared with areas east of the Rocky Mountains. Summer is characteristically sunny and dry, though July and August are the only distinct summer months. July and August are thus also the peak fire-danger months. Annual precipitation (rain and melted snow) averages as little as 10 inches at the lowest canyon floors; over 100 inches at the highest elevations. Wettest months are normally November, December, and January. Close to 60 percent of the annual total occurs during the period November through March. A slight, secondary peak in precipitation normally appears in May and June, followed by a sharp decrease in July. Snowfall accounts for more than 50 percent of the total precipitation at elevations above 4,800 ft. Snow cover usually persists in the mid elevation valleys from early December through the end of March. High-elevation snowpack reaches a depth of 5 ft (1.5 m) or more in March and April and may linger into June. The main season of lightning (or thunderstorm) activity extends from late May through August. Storms occur on an average of 3 or 4 days each in June, July, and August. Monthly mean temperatures in populated valley locations range from 24 F (-4 C) in January to 65 F (18 C) in July; these are midpoint values between the average daily maximum and minimum temperatures. The annual mean is 43 F (6 C). A large diurnal range occurs in summer. Extreme temperatures have been as high as 103" to 105" F (about 40" C) and as low as -36" F (-38" C). Temperature inversions are commonplace, particularly on the clear summer and early autumn nights. The frost-free season, defined as the period with minimum temperatures staying above 32" F (0" C), varies widely with elevation and topographic position. The season is generally longer at lower elevation locations and on slope positions in the "thermal belt" around 3,500 ft. The season is shorter in positions affected by cold air drainage and slopes above the “thermal belt” at elevations >5,500 ft. Relative humidity is usually high throughout the day in late autumn and winter, averaging 70 to 80 percent or higher in midafternoon. In July and August, afternoon values average near 35 percent in the mid elevation valleys and 45 percent at 5,500 ft. Summer nighttime humidity in these valleys typically recovers to over 90 or 95 percent by dawn. On the slopes above the temperature inversion, at the same time, humidity may average only 50 to 60 percent. Winds have a prevailing (most frequent) direction from the southwest during all or most of the year. Local terrain effects modify the larger-scale wind that occurs in the adjacent free atmosphere. A nighttime drainage effect is common. Sunshine duration is at a minimum in December, when it may average only 20 percent of the maximum possible. July has close to 80 percent of the maximum possible.
(from Finklin, A. 1983. Climate of Priest River Experimental Forest, Northern Idaho.GTR-INT-159)
Frost-free period (days):
Total range = 100 to 175 days
Central tendency = 130 to 170 days
Mean annual precipitation (cm):
Total range = 400 to 720 mm
(16 to 28 inches)
Central tendency = 540 to 635 mm
(21 to 25 inches)
MAAT (C)
Total range = 7.9 to 11.6
(46 to 53 F)
Central tendency = 9.1 to 10.6
(48 to 51 F)
Climate stations: noneTable 4 Representative climatic features
Frost-free period (characteristic range) 100-130 days Freeze-free period (characteristic range) 150-180 days Precipitation total (characteristic range) 20-30 in Frost-free period (actual range) 100-140 days Freeze-free period (actual range) 140-190 days Precipitation total (actual range) 20-30 in Frost-free period (average) 120 days Freeze-free period (average) 170 days Precipitation total (average) 30 in Characteristic rangeActual rangeBarLineFigure 1. Monthly precipitation range
Characteristic rangeActual rangeBarLineFigure 2. Monthly minimum temperature range
Characteristic rangeActual rangeBarLineFigure 3. Monthly maximum temperature range
BarLineFigure 4. Monthly average minimum and maximum temperature
Figure 5. Annual precipitation pattern
Figure 6 Annual average temperature pattern
Climate stations used
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(1) KAMIAH [USC00104793], Kamiah, ID
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(2) DWORSHAK FISH HATCH [USC00102845], Orofino, ID
">Influencing water features
Water Table Depth: 53 - >200 cm<br />
(21 - >80 inches)<br />
<br />
Flooding: <br />
Frequency: none - occasional <br />
Duration: None - Long<br />
<br />
Ponding:<br />
Frequency: None<br />
Duration: NoneSoil features
This ecological site is associated with several soil components (Tombeall, Joseph, Bridgewater). These components can be grouped into the soil subgroups Cumulic Haploxerolls and Aquic Xerofluvents. These soils are often composed of gravelly alluvium derived from basalt.
Parent Materials:
Kind: alluvium
Origin: basalt
Surface Texture:
(1)Extremely Cobbly-Loamy Coarse Sand
(2) Extremely Gravelly-Silt LoamTable 5. Representative soil features
Parent material (1) Alluvium – basalt
Surface texture (1) Extremely cobbly loamy coarse sand
(2) Extremely gravelly silt loam
Drainage class Well drained Permeability class Moderate Depth to restrictive layer Not specified Surface fragment cover <=3" Not specified Surface fragment cover >3" Not specified Available water capacity
(0-40in)2.3 in Calcium carbonate equivalent
(0-60in)Not specified Electrical conductivity
(0-60in)Not specified Sodium adsorption ratio
(0-60in)Not specified Soil reaction (1:1 water)
(0-60in)7.2 Subsurface fragment volume <=3"
(10-60in)40 % Subsurface fragment volume >3"
(10-60in)35 % Table 6. Representative soil features (actual values)
Drainage class Somewhat poorly drained to well drained Permeability class Moderate to rapid Depth to restrictive layer 0 in Surface fragment cover <=3" 0 % Surface fragment cover >3" 0 % Available water capacity
(0-40in)1.2 – 4.7 in Calcium carbonate equivalent
(0-60in)0 % Electrical conductivity
(0-60in)0 mmhos/cm Sodium adsorption ratio
(0-60in)0 Soil reaction (1:1 water)
(0-60in)6.4 – 7.3 Subsurface fragment volume <=3"
(10-60in)34 – 47 % Subsurface fragment volume >3"
(10-60in)20 – 35 % Ecological dynamics
State and transition model
Custom diagramStandard diagramAdditional community tables
Interpretations
Supporting information
References
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1980. USNVC [United States National Vegetation Classification]. 2019. United States National Vegetation Classification Database, V2.03. Federal Geographic Data Committee, Vegetation Subcommittee, Washington DC.. USNVC: http://usnvc.org/.
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Finklin, A.I. 1983. Climate of Priest River Experimental Forest, northern Idaho. Gen. Tech. Rep. INT-159. U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station, Ogden, UT. 53.
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Jim Cornwell. 2009. NRCS Idaho Draft Range Site Descriptions.
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Kovalchik, B.L. and R.R. Clausnitzer. 2004. Classification and Management of Aquatic, Riparian, and Wetland Sites on the National Forests of Eastern Washington: Series Description. General Technical Report PNW-GTR-593. United States Department of Agriculture, Forest Service, Pacific Northwest Research Station. 1–354.
Contributors
Stephanies Shoemaker
Brian GardnerApproval
Curtis Talbot, 10/15/2020
Rangeland health reference sheet
Interpreting Indicators of Rangeland Health is a qualitative assessment protocol used to determine ecosystem condition based on benchmark characteristics described in the Reference Sheet. A suite of 17 (or more) indicators are typically considered in an assessment. The ecological site(s) representative of an assessment location must be known prior to applying the protocol and must be verified based on soils and climate. Current plant community cannot be used to identify the ecological site.
Author(s)/participant(s) Contact for lead author Date 04/21/2026 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
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Presence of water flow patterns:
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Number and height of erosional pedestals or terracettes:
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Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
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Number of gullies and erosion associated with gullies:
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Extent of wind scoured, blowouts and/or depositional areas:
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Amount of litter movement (describe size and distance expected to travel):
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Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
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Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
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Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
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Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
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Functional/Structural Groups (list in order of descending dominance by above-ground annual-production or live foliar cover using symbols: >>, >, = to indicate much greater than, greater than, and equal to):
Dominant:
Sub-dominant:
Other:
Additional:
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Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
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Average percent litter cover (%) and depth ( in):
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Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
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Potential invasive (including noxious) species (native and non-native). List species which BOTH characterize degraded states and have the potential to become a dominant or co-dominant species on the ecological site if their future establishment and growth is not actively controlled by management interventions. Species that become dominant for only one to several years (e.g., short-term response to drought or wildfire) are not invasive plants. Note that unlike other indicators, we are describing what is NOT expected in the reference state for the ecological site:
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Perennial plant reproductive capability:
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