General information

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

This ecological site currently resides in the Major Land Resource Area (MLRA) 43A Northern Rocky Mountains. The area of MLRA 43A is expansive and is further divided into Land Resource Units (LRU). A detailed description of MLRA 43A can be found at:
https://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/ref/?cid=nrcs142p2_053624
Major Land Resource Area (MLRA): 043A–Northern Rocky Mountains

This MLRA is located in Montana (43 percent), Idaho (34 percent), and Washington (23 percent). It makes up about 31,435 square miles (81,460 square kilometers). It has no large cities or towns. It has many national forests, including the Okanogan, Colville, Kootenai, Lolo, Flathead, Coeur d’Alene, St. Joe, Clearwater, and Kaniksu National Forests.

This MLRA is in the Northern Rocky Mountains Province of the Rocky Mountain System. It is characterized by rugged, glaciated mountains; thrust- and block-faulted mountains; and hills and valleys. Steep-gradient rivers have cut deep canyons. Natural and manmade lakes are common.

The major Hydrologic Unit Areas (identified by four-digit numbers) that make up this MLRA are: Kootenai-Pend Oreille-Spokane (1701), 67 percent; Upper Columbia (1702), 18 percent; and Lower Snake (1706), 15 percent. Numerous rivers originate in or flow through this area, including, the Sanpoil, Columbia, Pend Oreille, Kootenai, St. Joe, Thompson, and Flathead Rivers.

This area is underlain primarily by stacked slabs of layered sedimentary or metasedimentary bedrock. The bedrock formations range from Precambrian to Cretaceous in age. The rocks consist of shale, sandstone, siltstone, limestone, argillite, quartzite, gneiss, schist, dolomite, basalt, and granite. The formations have been faulted and stacked into a series of imbricate slabs by regional tectonic activity. Pleistocene glaciers carved a rugged landscape that includes sculpted hills and narrow valleys filled with till and outwash. Continental glaciation over road the landscape in the northern half of the MLRA while glaciation in the southern half was confined to montane settings.

The average annual precipitation is 25 to 60 inches (635 to 1,525 millimeters) in most of this area, but it is as much as 113 inches (2,870 millimeters) in the mountains and is 10 to 15 inches (255 to 380 millimeters) in the western part of the area. Summers are dry. Most of the precipitation during fall, winter, and spring is snow. The average annual temperature is 32 to 51 degrees F (0 to 11 degrees C) in most of the area, decreasing with elevation. In most of the area, the freeze-free period averages 140 days and ranges from 65 to 215 days. It is longest in the low valleys of Washington, and it decreases in length with elevation. Freezing temperatures occur every month of the year on high mountains, and some peaks have a continuous cover of snow and ice.

The dominant soil orders in this MLRA are Andisols, Inceptisols, and Alfisols. Many of the soils are influenced by Mount Mazama ash deposits. The soils in the area have a frigid or cryic soil temperature regime; have an ustic, xeric, or udic soil moisture regime; and dominantly have mixed mineralogy. They are shallow to very deep, are very poorly drained to well-drained, and have most of the soil texture classes. The soils at the lower elevations include Udivitrands, Vitrixerands and Haplustalfs. The soils at the higher elevations include Dystrocryepts, Eutrocryepts, Vitricryands , and Haplocryalfs. Cryorthents, Cryepts, and areas of rock outcrop are on ridges and peaks above timberline

This area is in the northern part of the Northern Rocky Mountains. Grand fir, Douglas-fir, western red cedar, western hemlock, western larch, lodgepole pine, subalpine fir, ponderosa pine, whitebark pine, and western white pine are the dominant overstory species, depending on precipitation, temperature, elevation, and landform aspect. The understory vegetation varies, also depending on climatic and landform factors. Some of the major wildlife species in this area are white-tailed deer, mule deer, elk, moose, black bear, grizzly bear, coyote, fox, and grouse. Fish, mostly in the trout and salmon families, are abundant in streams, rivers, and lakes.

More than one-half of this area is federally owned and administered by the U.S. Department of Agriculture, Forest Service. Much of the privately-owned land is controlled by large commercial timber companies. The forested areas are used for wildlife habitat, recreation, watershed, livestock grazing, and timber production. Meadows provide summer grazing for livestock and big game animals. Less than three percent of the area is cropland.

LRU notes

LRU D-RATTLESNAKE, MISSION MOUNTAINS, AND BOB MARSHALL.
The landscape is mountains, and the landforms are mountain slopes, alpine ridges and cirquelands and valley floors. The area includes the Whitefish, Swan and Flathead mountains. The Whitefish/Swan Mtns. are block faulted mountain ranges are formed from argillite, siltite and dolomite and strongly shaped by alpine glaciation. Glacial till covers much of the landscape. Some volcanic ash deposits. Flathead Mtns. are thrust faulted mountains that formed from shale, sandstone, limestone and conglomerate. These mountains have been strongly shaped by alpine glaciation. The elevation ranges from 2900 feet to 8000 feet for the Whitefish and Swan mountains and 3680 feet to 8500 feet for the Flathead mountains. The drainage density for both areas is moderate. The geology is mainly Belt series (Missoula group and others) and alluvium in the valley areas. There is Cambrian in the eastern portion of and Glacial geology throughout, Kootenai in the northeastern portion and Tertiary geology in the northern portion of the area. The soils of the mountains are predominantly till with volcanic ash and in the valley areas alluvium or outwash. The soil temperature regime is mainly cryic, and the soil moisture regime is mainly udic. The mean annual precipitation ranges from 50 inches to 70 inches with about 80 percent falling as snow for the entire area. Lakes occur in glacial cirques and in glacial valleys in the Whitefish and Swan mountains and a few in the glacial cirque basins in the Flathead mountains. The main vegetation for the area is Douglas fir forest types and western spruce-fir forest types. This LRU is predominantly all federally owned lands including Bob Marshall Wilderness, Flathead N.F., Great Bear Wilderness and Flathead Indian Reservation. There are small areas of Lolo N.F., Mission Mountain Wilderness, National Bison Range and Scapegoat Wilderness. Borders Swan River NWR, Glacier N.P. and the Lewis and Clark N.F. Land cover is predominantly conifer xeric-mesic and mesic-wet type, recently burned, Alpine sparse and barren and harvested forest areas. Specifically, in the Whitefish and Swan mountains, the land use is predominantly rural and suburban development and some timber harvest. In the Flathead mountains, the land use is predominantly wilderness and therefore human disturbances are minor. The primary natural disturbances are fire, insects and windthrow.

Classification relationships

This is related to the EPA land classification framework of: Level 3- 41 Canadian Rockies. Specifically, it includes Levels 41c, 41e, minor 41b (tiny amount of 41d, 15l and 15a).
This area is related predominantly to the USFS Province M333Cb Whitefish/Swan Mtns., and M333Ce Flathead Thrust Faulted Mtns. This LRU is roughly two-thirds Province Cb and a third Province Ce.

Ecological site concept

It is in cool, moist mid-elevations that span the lower subalpine zone. This ecological site is found on back, foot and toeslope positions, on mountain slope and stream terrace landforms, on slopes less than forty percent, at elevations ranging 1,300 to 1400 meters. Subalpine fir (Abies lasiocarpa) and Engelmann spruce (Picea engelmannii) are the dominant overstory species with co-occurring Douglas-fir (Pseudotsuga menziesii) and lodgepole pine (Pinus contorta). The main understory species are the medium sized shrub Rocky Mountain Maple, the mid height shrub Thinleaf huckleberry (Vaccinium membranaceum) with an understory of wild sarsaparilla, threelaf foamflower and queencup bead lily (Clintonia uniflora). Soils associated with this Ecological Site are very deep, well drained or somewhat excessively drained and have subsoils with abundant rock fragments. There is no flooding or ponding on this site. The parent material is colluvium, alluvium or glacial till from metasedimentary rock. If volcanic ash is found in these soils, it originates from the eruption of Mount Mazama (Crater Lake, Oregon) and is apparent in the soil profile as a surface mantle or series of layers in the upper part of the soil profile. Volcanic ash has properties that provide important additions to the subsurface soils that occur below the ash cap. Low bulk density, typically less rock fragments, and high water holding capacity increase the storage of water near the surface in soils with volcanic ash. In Soil Taxonomy, these soils classify primarily as loamy-skeletal Inceptisols soil order and fine-loamy Alfisols. Some areas may have Alfisols (with a volcanic ash cap).

Table 1. Dominant plant species