Physiographic features

Physiographic Features
This ecological site occurs mainly on concave slopes of mountains, drainageways and avalanche chutes. Parent materials are mostly colluvium derived from granitic or metamorphic rock mantled by volcanic ash and loess.

Landscapes: Mountains
Landforms: Mountain slopes, drainageways, avalanche chutes

Elevation:
Total range = 705 to 2110 m
(2,310 to 6,920 feet)
Central tendency = 1270 to 1645 m
(4,165 to 5,395 feet)

Slope (percent):
Total range = 0 to 125 percent
Central tendency = 45 to 75 percent

Aspect: Total range: 35-160-325
Central; tendency: 110-160-245

Table 2. Representative physiographic features

Table 3. Representative physiographic features (actual ranges)

Climatic features

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 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. 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 and 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 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 = 35 to 95 days
Central tendency = 45 to 70 days

Mean annual precipitation (cm):
Total range = 900 to 1845 mm
(35 to 73 inches)
Central tendency = 1225 to 1475 mm
(48 to 58 inches)
MAAT (C)
Total range = 2.6 to 8.2
(37 to 47 F)
Central tendency = 4.7 to 6.1
(40 to 43 F)

Influencing water features

Water Table Depth: >80 inches

Flooding:
Frequency: None
Duration: None

Ponding:
Frequency: None
Duration: None

Soil features

Representative Soil Features

This ecological site is associated with several soil components (e.g. Andic Cryumbrepts, Handoff, Stepoff, and Weitas). The soil components are Andic Humicryepts, Typic Udivitrands, and Vitric Fulvicryands. These soils have developed in thick (>7 inches) Mazama tephra deposits (often highly mixed with colluvium) over colluvium derived from granitic or metamorphic rock. They have adequate water holding capacity and are well drained.

Typically, silicon and aluminum contained in volcanic ash weather to form various combinations of allophane and imogolite, which are noncrystalline hydrous aluminosilicates. Soils dominated by allophane and imogolite in the clay-size fraction are referred to as allophanic soils. They are characterized by moderately-to-slightly acid pH and low aluminum availability. Under certain conditions, aluminum-humus complexes are preferentially formed instead of allophane and imogolite. This process gives rise to non-allophanic soils. This process is well documented in the Grand Fir Mosaic Ecological site. There is some evidence that a similar process can occur in organic enriched volcanic ash materials in the alder dominated avalanche chutes and drainages.

Fragment content of surface layers (% Volume): 0 to 11 percent (median = 5%)
Content Fragments

Table 4. Representative soil features

Table 5. Representative soil features (actual values)

References

• . Fire Effects Information System. http://www.fs.fed.us/database/feis/.

• Cooper, S.V., K.E. Neiman, R. Steele, and D.W. Roberts. 1991. Forest Habitat types of Northern Idaho, A Second Approximation.

• Ferguson, D.E. and F.D. Johnson. 1996. Classification of Grand Fir Mosaic habitats.. Gen. Tech. Rep. INT-159. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station. Ogden UT. 1–53.

• 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.

• Smith and Fischer. 1997. Fire Ecology of the Forest Habitat Types of Northern Idaho.

Approval

Curtis Talbot, 10/14/2020