chapter 6 lta descriptions section m332b bitterroot...

CHAPTER 6

LTA Descriptions

Section M332B Bitterroot Valley

This Section occurs in west central Montana. It is a portion of the SouthwestMontana Mountain and Valley area previously described. Forty eight LTAs weremapped in this Section. See Appendix F for a complete list of LTAs and theiracreages. Map unit descriptions are preceded by the following illustrations:

Figure 20: Map showing location of M332B within the Northern Region

Figure 21: M332B landscape photograph Bitterroot National Forest

Figure 22: Map showing distribution of LTAS within M332B

Figure 23: Bar chart showing abundance of landform groups within M332B

Figure 24: Bar chart showing abundance of geologic material groups within M332B

Landtype Associations of the Northern Region

LTA10-M332Bd

VALLEYS: RECENT COARSE ALLUVIUM

Location: This LTA is located in the Sapphire Mountains, Flint Range, and thePintler Range on the Beaverhead-Deerlodge National Forest in the upper ClarkFork River Basin in southwest Montana.

Acreage by Subsection 10-M332Bd 27,680

LTA Setting and General Characteristics:

Differentiating Characteristics: This LTA occurs in a valley bottom landscapesetting, which is typically composed of floodplains and terraces. Parentmaterial is alluvium deposited over a variety of bedrock types.

Accessory Characteristics: The primary soils are deep with cobbly sandy andloamy textures. The vegetation is a mosaic of grasslands, shrublands, andconiferous forest. Mean annual precipitation ranges from 41 to 102 centimeters(16 to 40 inches). The elevation range of this LTA is 1524 to 1829 meters(5000 to 6000 feet). The dominant slopes have gradients of 0 to 20 percent.This LTA is slightly dissected by streams, with the dominant stream patternbeing parallel. Wetlands are a major component of this LTA.

LTA Components: This landtype association consists of floodplains andterraces.

Floodplains are formed in coarse alluvium. Slope gradients range from 0 to 10percent. Soils on these landforms are deep, weakly developed, with cobblysandy and loamy textures. These soils are classified as Typic Cryaquepts andCryaquolls, and Typic and Oxyaquic Cryochrepts and Cryoborolls. Rock outcropdoes not occur on this landscape component. The dominant potential naturalvegetation is willow, sedge, spruce, and subalpine fir series. This componentrepresents 40 percent of this LTA.

Terraces are formed in coarse alluvium. Slope gradients range from 0 to 20percent. Soils on these landforms are deep, weakly developed, with cobblysandy and loamy textures. These soils are classified as Typic Cryoboralfs,Cryochrepts and Cryoborolls. Rock outcrop does not occur on this landscapecomponent. The dominant potential natural vegetation is Idaho fescue,sagebrush, Douglas-fir, and subalpine fir series. This component represents 60percent of this LTA.

Compiled by: Dave Ruppert, Beaverhead-Deerlodge National Forest

LTA10-M332B

VALLEYS: RECENT COARSE ALLUVIUM

Location: This unit is located in the major valley bottoms of west-centralMontana and is in the Bitterroot, Blackfoot, and Upper Clark Fork River Basins.

Acreage by Section

10-M332B 174,283 (Section except M332Bd)

LTA Setting and General Characteristics

Differentiating characteristics: This map unit occurs in a major valleybottom landscape setting which is typically composed of floodplains, terraces,and alluvial basins. Parent materials are recent alluvial deposits and olderoutwash deposits.

Accessory Characteristics: The primary soils are very deep with coarse tomedium textures. The vegetation is a mosaic of dry coniferous forest, ripariandeciduous forest, and wet meadows. Mean annual precipitation ranges from 28 to46 centimeters (11 to 18 inches). The elevation range is 975 to 1677 meters(3200 to 5500 feet). The dominant slopes gradients are 0 to 6 percent. Thisunit is moderately dissected by streams; the dominant stream pattern isdendritic. Wetlands are a major component of this unit.

LTA Components: This landtype association consists of stream terraces,floodplains, and alluvial basins.

Stream terraces are formed in mixed alluvium and glacial outwash. Slopegradients range from 2 to 6 percent. Soils on this landform are very deep andsomewhat excessively to somewhat poorly drained. These soils are weaklydeveloped and consist of thin layer of loamy material over sand and gravel tocobble-sized rocks. The dominant soils are classified as FluvaquenticHaploborolls and Typic Ustorthents. Rock outcrops do not occur in thislandscape component. The dominant potential natural vegetation is ponderosapine series. This component represents about 40 percent of this unit.

Floodplains are formed in extremely gravelly and cobbly, recent alluvium. Slopegradients range from 1 to 3 percent. Soils on this landform are very deep andpoorly drained. These soils are weakly developed and consist mostly ofcobbles, gravels and sands. The dominant soils are classified as TypicFluvaquents. Rock outcrop does not occur on this landscape component. Areasof cobbly to gravelly riverwash make up about 10 percent of this unit. Thedominant vegetation is a black cottonwood community type. The potentialnatural vegetation is not certain. This component represents about 35 percentof this unit.

Alluvial basins are formed in medium textured recent alluvium. Slope gradientsrange from 0 to 2 percent. Soils on this landform are very deep and verypoorly drained. These soils are weakly developed and consist of several feetof loamy and mucky alluvium over coarser sands and gravels. These soils areclassified as Fluvaquentic Endoaquolls. Rock outcrop does not occur on thislandform. The dominant potential natural vegetation is a complex of commoncattail and water sedge plant associations and Nebraska sedge community type.Mountain alder community type occupies many areas of this component. Thiscomponent represents 25 percent of this unit.

Compiled by: Bob Spokas, Bitterroot National Forest

LTA11-M332B

VALLEYS: LACUSTRINE DEPOSITS

Location: This unit is located primarily in the Upper Clark Fork River Basinof northwestern Montana.

Acreage by Section

11-M332B 117,468


Differentiating Characteristics: This map unit occurs in a valley terracelandscape setting, which is typically composed of Glacial Lake Missoulalacustrine deposits on terraces and benches that have slightly undulatingsurfaces. Parent materials consist of stratified lacustrine deposits of veryfine sand, silt and clay materials underlain by alluvial valley materials.

Accessory Characteristics: The primary soils are deep, layered, very finesand, silt and clay textured. Historically the vegetation was a continuous coverof open grown coniferous forest. Today home developments and farmland cover manyof the acres of this LTA. Mean annual precipitation ranges from 33 to 51centimeters (13 to 20 inches). The elevation range of this LTA is 616 to 1354meters (2000 to 4400 feet). The dominant slopes have gradients of 0 to 25percent except along incised draws. This unit is slightly dissected bystreams, where present, with the dominant stream pattern being dendritic.These are very dry landscapes and typically do not contain wetland features.

LTA Components: This landtype association consists of lacustrine terraces.

Lacustrine terraces are formed in fine stratified materials. These terraceshave slope gradients ranging from 0 to 25 percent. Soils on these landformsare deep, poorly developed and consist mostly of very fine sand, silt andclay. The major soils are classified as Typic Eutroboralfs. Rock outcropoccurs on less than 2 percent of this landscape component except as thelacustrine material was deposited around scoured landscapes. The dominantpotential natural vegetation is the Douglas-fir series.

Compiled by: Skip Barndt, Lolo National Forest

LTA12-M332B

VALLEYS: OUTWASH AND OTHER OLDER COARSE ALLUVIUM

Location: This unit is located in the major river valleys of west-centralMontana which includes the Bitterroot, Blackfoot, and Upper Clark Fork Riverbasins.

Acreage by Section 12-M332B 292,138


Differentiating characteristics: This map unit occurs in a major river valleysetting which is typically composed of coalescing glacial outwash fans andstream terraces and of lesser amounts of associated glacial moraines. Parentmaterials are coarse glacial outwash deposits that have high amounts of cobble,gravel overlain by finer alluvium and coarse, bouldery glacial till.

Accessory Characteristics: The primary soils are very deep with coarsetextures and numerous rock fragments. The vegetation is a mosaic of coniferousforest, savannahs, and dry grassland. Mean annual precipitation ranges from 28to 51 centimeters (11 to 20 inches). The elevation range is 914 to 1585 meters(3000 to 5200 feet). The dominant slopes have gradients of 2 to 30 percent.This unit is slightly dissected by streams, with the dominant stream patternbeing parallel on fans and terraces and deranged on rolling moraines. Wetlandsand ponds are a minor component of this unit.

LTA Components: This landtype association consists of coalescing fans andterraces, and rolling glacial moraines.

Coalescing fans and terraces are formed in coarse glacial outwash that isoverlain by a thin layer of medium textured alluvium. Slope gradients rangefrom 2 to 20 percent. Soils on this landform are very deep and somewhatexcessively drained. These soils are weakly developed and consist of dark,gravelly loam about 15 inches thick overlying extremely cobbly sand outwash.The dominant soils are classified as Typic Haploborolls and AridicUstochrepts. Rock outcrop does not occur in this landscape component. Thedominant potential natural vegetation is a complex of ponderosa pine, roughfescue and Douglas-fir series. This component represents 70 percent of thisunit.

Glacial moraines are formed in coarse, stony to bouldery glacial till. Slopegradients range from 5 to 30 percent. Soils on this landform are very deep andsomewhat excessively drained. These soils are weakly developed and consist ofextremely bouldery sandy loam surface layers overlying extremely cobbly loamysand substrata. The dominant soils are classified as Typic Ustochrepts. Rockoutcrop occurs on less than 5 percent of this landscape component. Thedominant potential natural vegetation is Douglas-fir series. This componentrepresents 20 percent of this unit.

Compiled by: Ken McBride, Bitterroot National Forest

Chapter 6

LTA14-M332B

VALLEYS: RECENT FINE ALLUVIUM

Location: This unit is located in the Sapphire Mountain Range of west-centralMontana and is in the Bitterroot River Basin.

Acreage by Section

14-M332B 33,479


Differentiating characteristics: This map unit occurs in a major valleybottom landscape setting which is typically composed of floodplains, streamterraces, and alluvial basins. Parent materials are recent alluvial deposits.

Accessory Characteristics: The primary soils are very deep with moderatelyfine to fine textures. The vegetation is a mosaic of dry coniferous forest,riparian deciduous forest, and wet meadows. Mean annual precipitation rangesfrom 46 to 61 centimeters (18 to 24 inches). The elevation range is 1341 to1524 (4400 to 5000 feet). The dominant slopes have gradients of 0 to 8percent. This unit is moderately dissected by streams, with the dominantstream pattern being dendritic. Wetlands are a major component of this unit.

LTA Components: This landtype association consists of alluvial basins, streamterraces, and floodplains.

Alluvial basins are formed in moderately fine textured recent alluvium.Slope gradients range from 0 to 3 percent. Soils on this landform are verydeep and poorly or very poorly drained. These soils are weakly developed andconsist of several feet of moderately fine and mucky alluvium over coarsersands and gravels. The dominant soils are classified as Cumulic Cryaquolls andHistic Cryaquolls. Rock outcrop does not occur on this landscape component.The dominant potential natural vegetation is a common cattail and water sedgeplant associations and Nebraska sedge community type. This componentrepresents about 35 percent of this unit.

Stream terraces are formed in mixed alluvium and glacial outwash. Slopegradients range from 2 to 8 percent. Soils on this landform are very deep andsomewhat poorly to well drained. These soils are weakly developed and consistof several feet of medium to moderately fine sediment over sands an d gravels. The dominant soils are classified as Oxyaquic Cryoborolls, and CumulicCryoborolls. Rock outcrop does not occur on this component. The vegetation onthis component has all been converted to hay meadows and the potential naturalvegetation is uncertain. This component represents about 30 percent of thisunit.

Floodplains are formed in extremely gravelly and cobbly, recent alluvium.Slope gradients range from 1 to 4 percent. Soils on this landform are verydeep and poorly drained. These soils are weakly developed and consist ofcobbles, gravels, and sands. The dominant soils are classified as TypicCryaquents. Areas of cobbly to gravelly riverwash also occur within thiscomponent. Rock outcrop does not occur on this component. The dominantvegetation is a black cottonwood community type. The potential naturalvegetation is uncertain. This component represents about 20 percent of thisunit.


LTA20-M332B

BREAKS: METASEDIMENTARY (BELT)

Location: This unit is located in the Sapphire and Bitterroot Mountains ofwest-central Montana and occurs in the Bitterroot, Blackfoot, and upper ClarkFork River Basins.

Acreage by Section

20-M332B 360,304


Differentiating characteristics: This map unit occurs on a very steep, deeplyeroded or faulted landscape setting which is typically composed of structuralor stream breaks. Parent material is colluvium and residuum derived frommetamorphosed Precambrian sedimentary bedrock and from small areas of volcanicbedrock (mostly rhyolite and andesite).

Accessory Characteristics: The primary soils are shallow to very deep withvery gravelly to very cobbly medium textures. The vegetation is a mosaic ofdry to moist coniferous forest. Mean annual precipitation ranges from 46 to 102centimeters (18 to 40 inches). The elevation range is 1219 to 2134 meters(4000 to 7000 feet). The dominant slopes have gradients greater than 60percent. This unit is moderately to highly dissected by streams, with thedominant stream pattern being parallel. Wetlands are a minor component of thisunit. Wide valley bottoms occur at the base of this unit, but are generallyconsidered as map unit inclusions.

LTA Components: This landtype association consists of structural and streambreaks:

These landforms are formed in colluvium and residuum. Slope gradients rangefrom 50 to 90 percent. Soils on these landforms are shallow to very deep andwell drained. These soils are weakly developed, and consist of very gravellysandy loam surfaces overlying extremely gravelly sandy loam substrata. Thedominant soils are classified as: Dystric and Lithic Cryochrepts, and Typicand Lithic Ustochrepts. Rock outcrop and talus occupy about 15 percent of thislandscape. On cool, mesic sites the dominant potential natural vegetation issubalpine fir series. On warmer, drier sites the dominant natural vegetationis Douglas-fir series. Stream and/or structural breaklands represent about 85percent of this unit.


LTA21-M332B

BREAKS: HIGHLY WEATHERED GRANITICS

Location: This unit is located in the southern end of the Bitterroot Mountainsand occurs in the Bitterroot River Basin of west-central Montana.

Acreage by Section

21-M332B 18,000


Differentiating characteristics: This map unit occurs on a very steep, deeplyeroded landscape setting which is typically composed of stream breaks. Parentmaterial is colluvium and residuum derived from highly weathered graniticbedrock.

Accessory Characteristics: The primary soils are shallow to deep, with verygravelly to extremely gravelly coarse, sandy textures. The vegetation is amosaic of dry to moist coniferous forest. Mean annual precipitation rangesfrom 41 to 102 centimeters (16 to 40 inches). The elevation range is 1280 to2073 meters (4200 to 6800 feet). The dominant slopes have gradients greaterthan 60 percent. This unit is moderately to highly dissected by streams, withthe dominant stream pattern being parallel. Talus and areas of rock outcropare major components of this map unit. Wetlands are a minor component of thisunit. Wide valley bottoms occur in this unit but are generally considered mapunit inclusions.

LTA Components: This landtype association consists of stream breaks.

These landforms formed in colluvium and residuum. Slope gradients range from50 to 90 percent. Soils on these landforms are shallow to very deep andsomewhat excessively drained. These soils are weakly developed and consist ofvery gravelly sandy loam surfaces overlying extremely gravelly loamy coarsesand substrata. The dominant soils are classified as: Dystric and LithicCryochrepts, and Typic and Lithic Ustochrepts. Rock outcrop and talus occupyabout 20 percent of this unit. On warmer, drier sites the dominant naturalvegetation is Douglas-fir series. On cool, mesic sites the dominant potentialnatural vegetation is subalpine fir series. Stream breaklands represent about85 percent of this unit.


Chapter 6

LTA22-M332B

BREAKS: WEAKLY WEATHERED GRANITICS

Location: This unit is located in the lower Bitterroot Mountains which is inthe Upper Clark Fork River Basin of northwest Montana.

Acreage by Section

22-M332B 59,119


Differentiating Characteristics: This map unit occurs on mountain sideslopelandscape settings, which are composed of structural or stream breaks. Parentmaterials are weakly weathered granitics. The landscape is dotted withgranitic tors, towers and rock outcrops due to the hardness of the material.

Accessory Characteristics: The primary soils are shallow extremely gravellysandy loams. The vegetation is a mosaic of coniferous forest and scree. Meanannual precipitation ranges from 76 to 190 centimeters (30 to 75 inches). Theelevation range of this LTA is 985 to 2031 meters (3200 to 6600 feet). Thedominant slopes have gradients are greater than 60 percent. This unit ismoderately to highly dissected by streams, with the dominant stream patternbeing parallel. Talus, tors, towers, and rock outcrops are major components ofthis map unit.

LTA Components: This landtype association consists of structural and streambreak components.

These landforms are developing on the steep mountain slopes adjacent todrainage bottoms. The slope gradients range from 50 to 100 percent. Soils onthese landforms are shallow with minimal development. The major soils areclassified as Dystric Eutrochrepts and Andic Cryochrepts. Rock outcrops occupyless than 15 to over 50 percent of the area. The dominant potential naturalvegetation is Douglas-fir and subalpine fir series.

Compiled by: Skip Barndt, Lolo National Forest.

LTA24-M332B

BREAKS: VOLCANICS

Location: This unit is located in the Sapphire and Bitterroot Mountains andoccurs within the Bitterroot River Basin of west-central Montana.

Acreage by Section

24-M332B 14,377


Differentiating characteristics: This map unit occurs on a very steep, deeplyeroded or faulted landscape setting which is typically composed of structuraland stream breaks. Parent material is colluvium and residuum derived fromvolcanic bedrock (mostly rhyolite and andesite).

Accessory Characteristics: The primary soils are shallow to very deep withvery gravelly medium to moderately fine textures. The vegetation is a mosaicof dry to moist coniferous forest. Mean annual precipitation ranges from 46 to76 cms. (18 to 30 inches). The elevation range is 1219 to 2012 meters (4000 to6600 feet). The dominant slopes have gradients greater than 60 percent. Thisunit is moderately to highly dissected by streams, with the dominant streampattern being parallel. Combined, rock outcrop and talus are major componentsof this map unit. Wetlands are a minor component of this unit. Wide valleybottoms occur in this unit, but are generally considered only map unitinclusions.

LTA Components: This map unit consists of structural and stream breaks.

These landforms are formed in colluvium and residuum. Slope gradients rangefrom 50 to 90 percent. Soils on these landforms are shallow to very deep andwell drained. These soils are weakly to moderately weathered, and consist ofgravelly loam surfaces overlying very gravelly clay loam or very gravelly loamsubstrata. The dominant soils are classified as: Typic Ustochrepts, TypicEutroboralfs, Lithic Argiborolls, and Dystric and Lithic Cryochrepts. Rockoutcrop and talus occupy about 15 percent of this map unit. On cool, mesicsites the dominant potential natural vegetation is subalpine fir series. Onwarmer, drier sites the dominant natural vegetation is Douglas-fir series.Stream and structural breaklands represent about 85 percent of this unit.


LTA25-M332B

BREAKS: SANDSTONES AND SHALES

Location: This LTA is located in the Flint Range on the Beaverhead-DeerlodgeNational Forest in the upper Clark Fork River Basin in southwest Montana.



Differentiating Characteristics: This LTA occurs in a mountain landscapesetting, which is typically composed of stream breaks. Parent materials areresiduum underlain by sandstone, shale and other mixed sedimentary bedrock.

Accessory Characteristics: The primary soils are shallow and moderately deepwith cobbly loamy textures. The vegetation is a mosaic of coniferous forestand rock. Mean annual precipitation ranges from 41 to 51 centimeters (16 to 20inches). The elevation range of this LTA is 1463 to 1982 meters (4800 to 6500feet). The dominant slopes have gradients of 60 to 100 percent. This LTA ismoderately dissected by streams, with the dominant stream pattern beingparallel. Wetlands are a minor component of this LTA.


Stream breaks are formed in very steep, stream dissected sandstone, shale, andother mixed sedimentary bedrock. Slope gradients range from 45 to 75 percent.Soils on these landforms are shallow and moderately deep, weakly developed,with cobbly loamy textures. These soils are classified as Lithic and TypicCryochrepts and Cryorthents, and includes some Lithic and Typic Cryoboralfs.Rock outcrop occurs on 10 to 30 percent of this landscape component, dependingon rock type. The dominant potential natural vegetation is the Douglas-firseries. This component represents 100 percent of this LTA.


LTA27-M332B

BREAKS: CARBONATES


Acreage by Section

27-M332B 9,864


Differentiating Characteristics: This LTA occurs in a mountain landscapesetting, which is typically composed of stream breaks. Parent materials areresiduum underlain by limestone bedrock.

Accessory Characteristics: The primary soils are shallow and moderately deepwith cobbly loamy textures. The vegetation is a mosaic of coniferous forestand rock. Mean annual precipitation ranges from 41 to 51 centimeters (16 to 20inches). The elevation range of this LTA is 1524 to 1982 meters (5000 to 6500feet). The dominant slopes have gradients of 45 to 80 percent. This LTA ismoderately dissected by streams, with the dominant stream pattern beingtrellis. Wetlands are a minor component of this LTA.


Stream breaks are formed in very steep, stream dissected limestone bedrock.Slope gradients range from 45 to 75 percent. Soils on these landforms areshallow and moderately deep, weakly developed, with cobbly loamy textures.These soils are classified as Lithic and Typic Cryochrepts. Rock outcropoccurs on about 15 percent of this landscape component. The dominant potentialnatural vegetation is Douglas-fir. This component represents 100 percent ofthis LTA.


Chapter 6

LTA29-M332B

BREAKS: QUARTZITES AND CALC-SILICATES

Location: This unit is located in the Sapphire Mountains and occurs in theBitterroot River Basin of west-central Montana.



Differentiating characteristics: This map unit occurs on a very steep, deeplyeroded landscape setting which is typically composed of stream breaks. Parentmaterial is colluvium and residuum derived from weakly weathered quartzite andcalc-silicates of the Belt Supergroup.

Accessory Characteristics: The primary soils are shallow to deep with verygravelly, very cobbly or extremely cobbly coarse to medium textures. Thevegetation is a mosaic of dry to moist coniferous forest. Mean annualprecipitation ranges from 46 to 89 cms. (18 to 35 inches). The elevation rangeis 1219 to 2134 meters (4000 to 7000 feet). The dominant slopes have gradientsgreater than 60 percent. This unit is moderately to highly dissected bystreams, with the dominant stream pattern being parallel. Rock outcrop, talus,and scree combined, are major components of this map unit. Wetlands are aminor component of this unit. Relatively wide valley bottoms occur in thisunit, but are generally considered only map unit inclusions.


These landforms are formed in colluvium and residuum. Slope gradients rangefrom 50 to 90 percent. Soils on these landforms are shallow to deep and welldrained. These soils are weakly to moderately developed, and consist of verycobbly loam surfaces overlying extremely cobbly fine sandy loam substrata. Thedominant soils are classified as: Typic and Lithic Ustochrepts, TypicEutroboralfs, Lithic Argiborolls, plus Dystric and Lithic Cryochrepts, Rockoutcrop, talus and scree occupy about 25 percent of this map unit. On warmer,drier sites the dominant natural vegetation is Douglas -fir series. On cool,mesic sites the dominant potential natural vegetation is subalpine fir series.Stream breaklands represent about 85 percent of this unit.


LTA34-M332B

HIGH RELIEF MOUNTAIN SLOPES: VOLCANICS

Location: This LTA is located in the Blackfoot River drainage.

Acreage by Section

34-M332B 46,982


Differentiating Characteristics: This LTA occurs in a mountainous landscapesetting which is typically composed of steep mountain slopes. Parent materialis colluvium and residuum underlain by weakly weathered andesite and othervolcanic rocks. In some areas the parent material is influenced by a complexof volcanic and metasedimentary Belt Series rocks.

Accessory Characteristics: The primary soils are moderately deep or deeper andare medium to moderately fine textured. The vegetation is coniferous forest.Mean annual precipitation ranges from 50 to 75 centimeters (20 to 30 inches).The elevation range of this LTA is 1464 to 2135 meters (4800 to 7000 feet).The dominant slopes have gradients of 25 to 60 percent. This LTA is moderatelydissected (moderately to widely spaced drainages) and deeply incised by streamswith the dominant stream pattern being dendritic. Small wetlands are sometimesassociated with slumpy areas.

LTA Components: This landtype association consists of high relief mountainslopes.

High relief mountain slopes are mostly formed in andesite and other volcanicrock. In some areas they are influenced by a complex of volcanic andmetasedimentary Belt Series rocks. Slope gradients range from 25 to 60percent. Soils on these landforms are moderately deep to very deep, moderatelydeveloped, and have very gravelly or gravelly loam, cobbly loam and stony loamsurfaces. Subsurface textures include very and extremely stony clay loam, veryand extremely cobbly loams, very gravelly clay loam and extremely gravellyloam. These soils are classified as Typic Cryoboralfs, Typic Eutroboralfs, andTypic Argiborolls. Rock outcrop occurs on less than 5 percent of thislandscape component. Small landslides are associated with basaltic andandesitic dikes and sills or local ash/tuff deposits. The dominant potentialnatural vegetation series are Douglas-fir and subalpine fir. This componentrepresents 100 percent of this LTA.

Compiled by: Larry Laing, Helena National Forest

Chapter 6

LTA35-M332B

WEAKLY GLACIATED MOUNTAIN SLOPES AND RIDGES: CALC-SILICATES AND QUARTZITES

Location: This unit is located in the Bitterroot and Sapphire mountain rangesof western Montana in the Bitterroot and Upper Clark Fork River Basins

Acreage by Section

35-M332B 27,909


Differentiating characteristics: This map unit occurs in a high elevationbroad ridgetop position which is typically composed of weakly expressedglaciated slopes and basins that were formed by ice -cap glaciers, minor valleyglaciers, and periglacial frost shattering. Parent materials are a complex offrost shattered residuum and colluvium intermixed with glacial till derivedfrom Precambrian calc-silicate and quartzitic rocks.

Accessory Characteristics: The primary soils are shallow to deep, mediumtextured soils with numerous rock fragments and have a volcanic ash surfacelayer. The vegetation is a mosaic of coniferous forest, stunted wind-deformedforest, and occasional small wet meadows. Mean annual precipitation rangesfrom 102 to 140 centimeters (40 to 55 inches). The elevation range is 1951 to2683 meters (6500 to 8800 feet). The dominant slopes have gradients of 20 to55 percent. This unit is slightly dissected by streams, with the dominantstream pattern being dendritic. Wetlands and ponds are a minor component ofthis unit.

LTA Components: This landtype association consists of weakly developed glacialcirques, and frost shattered mountain ridge tops.

Weakly developed glacial cirques are formed in residuum, colluvium, and till.Slope gradients range from 20 to 55 percent. Soils on this landform areshallow to deep and well drained. These soils are weakly developed and consistof extremely bouldery loam volcanic ash surface layers overlying very stonysandy loam substrata. The dominant soils are classified as Lithic and AndicCryochrepts. Rock outcrop occurs in about 10 percent of this landscapecomponent. The dominant potential natural vegetation is alpine larch-subalpinefir, whitebark pine-subalpine fir, and subalpine fir series. This componentrepresents 65 percent of this unit.

Frost shattered mountain ridge tops are formed in residuum and colluvium.Slope gradients range from 20 to 50 percent. Soils on this landform areshallow to deep and somewhat excessively drained. These soils are weaklydeveloped and consist of very stony loam volcanic ash surface layers overlyingvery cobbly coarse sandy loam substrata. The dominant soils are classified asLithic and Andic Cryochrepts. Rock outcrop occurs on about 15 percent of thislandscape component. The dominant potential natural vegetation is whitebarkpine-subalpine fir, alpine larch-subalpine fir, and subalpine fir series. Thiscomponent represents 35 percent of this unit.


LTA37-M332B

HIGH RELIEF MOUNTAIN SLOPES: CARBONATES

Location: This LTA is located in the Alice/Nevada Mountains within the ClarkFork basin.

Acreage by Section

37-M332B 6,635


Differentiating Characteristics: This LTA occurs in a mountainous landscapesetting which is typically composed of mountain slopes and narrow ridges.Parent materials are colluvium and residuum underlain by limestones andcalcareous argillite.

Accessory Characteristics: The primary soils are moderately deep and shallowwith extremely limey and rocky subsurface layers. The vegetation is a mosaicof coniferous forest with scattered grasslands and shrublands. Mean annualprecipitation ranges from 38 to 75 centimeters (15 to 30 inches). Theelevation range of this LTA is 1739 to 2288 meters (5700 to 7500 feet). Thedominant slopes have gradients of 40 to 60 percent. This LTA is moderately toslightly (moderately to widely spaced) dissected and weakly incised by streams,with the dominant stream patterns being subparallel and dendritic.

LTA Components: This landtype association consists of mountain slopes.

Mountain slopes are formed in limestone or calcareous argillite colluvium andresiduum. Slope gradients range from 40 to 60 percent. Soils on theselandforms are mostly moderately deep and shallow, weakly developed and areloamy. These soils are classified as Typic and Lithic Ustochrepts, and Typicand Lithic Cryochrepts. Rock outcrop occurs on about 15 percent of thislandscape component. The dominant potential natural vegetation is Douglas-firseries. Subalpine fir series dominates on northerly aspects.


LTA40-M332B

STEEP GLACIATED MOUNTAIN SLOPES: METASEDIMENTARY (BELT)

Location: This unit is located in the Lower Bitterroot Garnet, Sapphire andSwan Mountains of the Upper Clark Fork River basin of northwest Montana.

Acreage by Section

40-M332B 401,649


Differentiating Characteristics: This map unit occurs in a steep, alpineglacial landscape setting. Parent materials are metasediments composed ofargillites, siltites and quartzites with alpine glacial till scatteredthroughout; which is typically, medium textures.

Accessory Characteristics: The primary soils are shallow to moderately deepmoderately coarse to medium textured. The vegetation is a mosaic of coniferousforest, avalanche chutes, and rock outcrops. Mean annual precipitation rangesfrom 102 to 254 centimeters (40 to 100 inches). The elevation range of thisunit is 1785 to 2923 meters (5800 to 9500 feet). The dominant slopes havegradients greater than 60 percent. This map unit is moderately to highlydissected by streams, with the dominant stream pattern being parallel. Wetsidehill areas and grassy parks are a major component of this unit.

LTA Components: This landtype association consists of steep, glaciatedmountain slopes, and narrow valley trains.

Steep, glaciated mountain slopes are formed in metasediments that consist ofargillites, siltites and quartzites. Glacial trough walls, headwalls and ridgesystems are formed in the underlying bedrock. The convex uplands and sideslopes have been strongly scoured and contain shallow soils. The lower slopeshave glacial till accumulations. These areas have slopes that range from 45to 100 percent. Soils on the upper part of the landform are shallow tomoderately deep residuals and consist of rock and medium textured materials.The lower portion of the landform has deep soils, formed in the glacial tillmaterial. The major soils are classified as Cryandepts, Entic Cryandepts, andAndic Cryochrepts. Rock outcrops occupy more than 40 percent of the area. Thedominant potential natural vegetation is subalpine fir. This landformcomponent makes up 80 percent of the unit.

The narrow valley train glacial till is developed on valley bottoms landforms.Slope gradients range from 5 to 35 percent. Soils on these landforms are deep,moderately developed and consist mostly of loamy glacial till. The major soilsare classified as Entic Cryandepts. The dominant potential natural vegetationis subalpine fir. This landform component represents 20 percent of the unit.


LTA41-M332B

STEEP GLACIATED MOUNTAIN SLOPES: GRANITICS

Location: This unit is located in the Bitterroot and Anaconda Mountain Rangesof west-central Montana in the Bitterroot and Upper Clark Fork River Basins.

Acreage by Section

41-M332B 338,618


Differentiating characteristics: This map unit occurs on steep and very steepalpine glacial landscape settings. Parent material is colluvium, residuum, andscattered alpine glacial till, derived from granitic sources.

Accessory Characteristics: The primary soils are shallow to deep, coarsetextured, and contain numerous rock fragments throughout the profile.Additionally, avalanche chutes, rock outcrop, and rubble land are majorcomponents to this map unit. The vegetation is a mosaic of closed to openconiferous forest, and moist shrublands. Mean annual precipitation ranges from46 to 254 cms. (18 to 100 inches). The elevation range is 1219 to 3110 meters(4000 to 10200 feet). The dominant slopes have gradients of 15 to 100percent. This unit is moderately to highly dissected by streams, with thedominant stream pattern being parallel. Wetlands (wet side hills and avalanchechutes), lakes, and ponds are major components of this unit.

LTA Components: This landtype association consists of glacial trough walls,alpine ridges, and cirques (headwalls and basins).

Glacial trough walls were formed by alpine glacial scouring. After theglaciers retreated the walls were further modified by landslides and avalanchescreating avalanche chutes. Slope gradients range from 50 to 100 percent andslope shape is straight to concave. Soils on this landform are shallow to deepand very poorly to somewhat excessively drained. These soils are weaklydeveloped, and consist of very cobbly loam surfaces overlying very cobbly loamysand or very cobbly sandy loam substrata. The dominant soils are classifiedas: Lithic Cryochrepts, Andic Cryochrepts, Lithic Ustochrepts, and TypicUstochrepts. Typic Cryaquands occur extensively on northerly aspects in theheadwaters portion of these troughs. Rock outcrop, rubbleland, and avalanchechutes occupy about 45 percent of this component. The most common potentialnatural vegetation is subalpine fir, alpine larch-subalpine fir, andDouglas-fir. Avalanche chutes have a sitka alder community type. The TypicCryaquands soils that occur in the headwater portions of trough walls supporta sitka alder habitat type. This landform component represents about 60percent of this unit.

Cirque headwalls and basins were formed by alpine glacial erosion. Cirquebasins have slope gradients of 15 to 50 percent. Cirque headwalls have slopegradients greater than 60 percent (approaching vertical). Soils on thislandform are shallow to very deep, and very poorly drained to well drained.These soils are weakly developed and consist of very cobbly or extremelybouldery silt loam volcanic ash surfaces over very cobbly or very boulderyloamy sand substrata. The dominant soils on cirque headwalls are classified asAndic Cryochrepts and Lithic Cryochrepts. Soils in cirque basins areclassified as Typic Cryandepts and Histic Cryaquepts. Rock outcrop, talus, andscree occupy about 40 percent of this component. The dominant natural

vegetation is alpine larch-subalpine fir, whitebark pine-subalpine fir, andsubalpine fir on cirque headwalls and basins. The basins also contain Holm'sRocky Mountain sedge, and beaked sedge. This landform represents about 25percent of this unit.

Alpine ridges were formed by alpine glacial scouring and/or strong periglacialfrost shattering of exposed bedrock. Slope gradients range from 50 to 80percent. Soils on this landform are shallow and somewhat excessively drained.These soils are weakly developed and consist of very stony sandy loam surfacesoverlying extremely stony loamy sand substrata. Bedrock occurs at a depth ofless than 20 inches. The dominant soil is classified as Lithic Cryorthents;however, only about 20 percent of this landform has a soil cover. Rock outcrop,talus, and scree occupy about 80 percent of this component. The most commonpotential natural vegetation is alpine larch -alpine fir, whitebarkpine-subalpine fir, and subalpine fir series. This landform represents about15 percent of this unit.


LTA43-M332BdLTA43-M332Eb

STEEP GLACIATED MOUNTAIN SLOPES: CARBONATES

Location: This LTA is located in the Anaconda and Flint Ranges, and FleecerMountains on the Beaverhead-Deerlodge National Forest in the upper Clark ForkRiver Basin of southwest Montana.

Acreage by Subsection

43-M332Bd 77,602 43-M332Eb 2,698


Differentiating Characteristics: This LTA occurs in a glaciated mountainlandscape setting, which is typically composed of cirques, troughs, andmoraines. Parent materials are residuum underlain by limestone and glacialmoraines deposited on limestone and a variety of other bedrock types.

Accessory Characteristics: The primary soils are shallow to deep with cobblyloamy textures. The vegetation is a mosaic of grasslands, shrublands, andconiferous forest. Mean annual precipitation ranges from 51 to 127 centimeters(20 to 50 inches). The elevation range of this LTA is 1829 to 3049 meters(6000 to 10000 feet). The dominant slopes have gradients of 25 to 80 percent.This LTA is moderately dissected by streams, with the dominant stream patternbeing parallel. Wetlands are a major component of this LTA.

LTA Components: This landtype association consists of cirques and troughs, andmoraines.

Cirques and troughs are formed in limestone bedrock. Slope gradients rangefrom 45 to 100 percent. Soils on these landforms are shallow and moderatelydeep, weakly developed, with cobbly loamy textures. These soils areclassified as Typic and Lithic Cryorthents and Cryochrepts. Rock outcropoccurs on 30 to 90 percent of this landscape component. The dominant potentialnatural vegetation is Douglas-fir and subalpine fir series. This componentrepresents 40 percent of this LTA.

Moraines are composed of glacial deposits. Slope gradients range from 0 to 35percent. Soils on these landforms are deep, moderately developed, with cobblyloamy textures. These soils are classified as Typic Cryochrepts andCryoboralfs. Rock outcrop does not occur on this landscape component. Thedominant potential natural vegetation is sagebrush, Douglas -fir and subalpinefir series. The dominant vegetation in wetlands is willows, sedge, andsubalpine fir. This component represents 60 percent of this LTA.


Chapter 6

LTA44-M332B

STEEP GLACIATED MOUNTAIN SLOPES: SANDSTONES AND SHALES

Location: This LTA is located in the Flint Range on the Beaverhead-DeerlodgeNational Forest in the upper Clark Fork River basin in southwest Montana.


44-M332B 18,787


Differentiating Characteristics: This LTA occurs in a glaciated mountainlandscape setting, which is typically composed of cirques, troughs, andmoraines. Parent materials are residuum underlain by sandstone and shalebedrock, and moraines deposited on sandstone and shale and a variety of otherbedrock types.

Accessory Characteristics: The primary soils are shallow to deep with cobblyloamy textures. The vegetation is coniferous forest. Mean annualprecipitation ranges from 46 to 127 centimeters (18 to 50 inches). Theelevation range of this LTA is 1768 to 2988 meters (5800 to 9800 feet). Thedominant slopes have gradients of 25 to 100 percent. This LTA is moderatelydissected by streams, with the dominant stream pattern being parallel. Wetlandsare a major component of this LTA.

LTA Components: This landtype association consists of cirques and troughs, andmoraines.

Cirques and troughs are formed in sandstone and shale bedrock. Slope gradientsrange from 45 to 100 percent. Soils on these landforms are shallow andmoderately deep, weakly developed, and have cobbly loamy textures. Thesesoils are classified as Typic and Lithic Cryorthents and Cryochrepts. Rockoutcrop and scree occurs on 30-90 percent of this landscape component. Thedominant potential natural vegetation is subalpine fir series. This componentrepresents 60 percent of this LTA.

Moraines are composed of glacial deposits. Slope gradients range from 0 to 35percent. Soils on these landforms are deep, moderately developed, with cobbly loamy textures. These soils are classified as Typic Cryochrepts andCryoboralfs. Rock outcrop does not occur on this landscape component. Thedominant potential natural vegetation is Douglas-fir and subalpine fir series.This component represents 40 percent of this LTA.


LTA45-M332BLTA45-M332ELTA45-M333D

WEAKLY GLACIATED MOUNTAIN SLOPES AND RIDGES: GRANITE

Location: This unit is located in the Bitterroot and Sapphire mountain rangesof western Montana in the Bitterroot and Upper Clark Fork River Basins.

Acreage by Section

45-M332B 83,690 45-M332E 2,112 45-M333D 3,610


Differentiating characteristics: This map unit occurs in a high elevationbroad ridgetop position which is typically composed of weakly expressedglaciated slopes and basins that were formed by ice cap glaciers, minor valleyglaciers, and strong periglacial frost shattering. Parent materials are acomplex of frost shattered residuum and colluvium, intermixed with glacial tillderived from moderately weathered granite.

Accessory Characteristics: The primary soils are shallow to deep, coarse soilswith numerous rock fragments and have a volcanic ash surface layer. Thevegetation is a mosaic of coniferous forest, stunted wind-deformed forest, andoccasional small wet meadows. Mean annual precipitation ranges from 102 to 140centimeters (40 to 55 inches). The elevation range is 2073 to 2743 meters(6800 to 9000 feet). The dominant slopes have gradients of 20 to 55 percent.This unit is slightly dissected by streams, with the dominant stream patternbeing dendritic. Wetlands and ponds are a minor component of this unit.

LTA Components: This landtype association consists of weakly developed glacialcirques, and frost shattered mountain ridge tops.

Weakly developed glacial cirques are formed in residuum, colluvium, and tillderived from a variety of rock types. Slope gradients range from 20 to 55percent. Soils on this landform are shallow to deep and somewhat excessivelydrained. These soils are weakly developed and consist of extremely boulderyloam volcanic ash surface layers overlying very stony loamy sand substrata.The dominant soils are classified as Lithic and Andic Cryochrepts. Rockoutcrop occurs on about 10 percent of this landscape component. The dominantpotential natural vegetation is alpine larch -subalpine fir, whitebarkpine-subalpine fir, and subalpine fir series. This component represents 65percent of this unit.

Frost shattered mountain ridge tops are formed in residuum and colluvium.Slope gradients range from 20 to 50 percent. Soils on this landform areshallow to deep and somewhat excessively drained. These soils are weaklydeveloped and consist of very stony loam volcanic ash surface layers overlyingvery cobbly coarse sandy loam substrata. The dominant soils are classified asLithic and Andic Cryochrepts. Rock outcrop occurs on about 15 percent of thislandscape component. The dominant potential natural vegetation is whitebarkpine-subalpine fir, alpine larch-subalpine fir, and subalpine fir series. Thiscomponent represents 35 percent of this unit.


LTA50-M332B

GLACIATED MOUNTAIN SLOPES: METASEDIMENTARY (BELT)

Location: This unit is located in the lower Bitterroot, Garnet, Sapphire andSwan Mountains of the Upper Clark Fork River basin of northwest Montana.

Acreage by Section

50-M332B 312,518


Differentiating Characteristics: This map unit occurs on gently to moderatelysloping glacial landscape settings. Parent materials are undifferentiatedglacial drift composed of argillites, siltites and quartzites. Small areas ofresidual materials and rock outcrop are also included. These are mediumtextured.

Accessory Characteristics: The primary soils are deep, moderately coarse tomedium textured. The vegetation is, typically, a mosaic of coniferous forestand wetlands. Mean annual precipitation ranges from 64 to 127 centimeters (25to 50 inches). The elevation range of this unit is 1077 to 1692 meters (3500to 5500 feet). The dominant slopes have gradients less than 60 percent and,typically, range from 10 to 35 percent. This map unit is slightly dissected bystreams, with the dominant stream pattern being dendritic. Wetlands, seeps,bogs and riparian zones are common components of this unit.

LTA Components: This landtype association consists of gently to moderatelysloping glacial moraine.

Gently to moderately sloping glacial moraines are formed in theundifferentiated belt materials, both till and outwash. The rolling plains aredotted with wetlands, seeps, bogs and riparian zones. These areas have slopesthat range from 0 to less than 60 percent with moderately coarse to mediumtextured materials. The major soils are classified as Andic DystricEutrochrepts and Andic Cryochrepts. The dominant potential natural vegetationis subalpine fir, grand fir, Douglas-fir and spruce.


Chapter 6

LTA51-M332B

GLACIATED MOUNTAIN SLOPES: GRANITIC

Location: This unit is located in the Bitterroot, Sapphire and AnacondaMountain Ranges of western Montana and occurs in the Bitteroot, Upper ClarkFork, and the Blackfoot River Basins of western Montana.

Acreage by Section

51-M332B 197,817


Differentiating characteristics: This map unit occurs on gently to moderatelysloping glacial landscape settings. Parent material is alpine glacial till,alluvium, and residuum derived from granitic sources.

Accessory Characteristics: The primary soils are deep and very deep withcoarse to moderately coarse textures. Small inclusions of shallow soils, rockoutcrop, and rubble land can also be found within this unit. The vegetation isa mosaic of moderately dry, moist, and wet coniferous forest. Mean annualprecipitation ranges from 41 to 102 centimeters (16 to 40 inches). Theelevation range is 1158 to 2134 meters (3800 to 7000 feet). Slope gradientsrange from 1 to 60 percent. This unit is slightly to moderately dissected bystreams, with the dominant stream pattern being parallel. Wetlands, seeps,bogs and riparian zones are major components of this unit.

LTA Components: This landtype association consists of glacial moraines, andfloodplains.

Glacial moraines were formed in alpine glacial till. Slope gradients rangefrom 8 to 60 percent and slope shape is convex. Soils on this landform areshallow to deep, and moderately well to somewhat excessively drained. Thesesoils are weakly developed and consist of bouldery loam volcanic ash surfacelayers overlying very cobbly loamy sand substrata. The dominant soils areclassified as: Andic Cryochrepts, Lithic Cryochrepts, Lithic Ustochrepts, andTypic Ustochrepts. Rock outcrop and rubble land occupy about 10 percent ofthis component. The dominant potential natural vegetation is subalpine fir andDouglas-fir series. This landform component represents about 75 percent ofthis unit.

Floodplains were formed in coarse alluvium. Slope gradients range from 1 to 8percent. Soils on this landform are very deep and moderately well to verypoorly drained. These soils are very weakly develop and consist of cobbly loam surface layers overlying very gravelly loamy sand substrata. The dominantsoils are classified as: Typic Cryaquents, Oxyaquic Cryofluvents, and AndicCryofluvents. Rock outcrop occurs on less than 5 percent of this component.The dominant natural vegetation is western redcedar, grand fir, and subalpinefir series. This landform represents about 25 percent of this unit.


LTA53-M332BLTA53-M333BLTA53-M333C

GLACIATED MOUNTAIN SLOPES: SANDSTONES, SHALES, ANDCARBONATES

Location: This map unit is located in the Swan, Mission, Flathead, andWhitefish mountain ranges of the Flathead, Clearwater, and Blackfoot Riverbasins in northwest Montana.

Acreage by Section

53-M332B 6,926 53-M333C 100,613 53-M333B 8,091


Differentiating Characteristics: This map unit occurs in both valley bottomand upland landscape settings, which are primarily composed of glacial morainelandforms. Parent materials are continental or alpine glacial debris with orwithout volcanic ash surface layers; underlain by Paleozoic and Mesozoicsandstone, shale, and limestone bedrocks. In the North Fork of the FlatheadRiver areas of Tertiary siltstone are included in this map unit.

Accessory Characteristics: The primary soils are moderately deep to very deep,with gravelly medium and moderately fine textures. The major vegetative coveris a dense coniferous forest with occasional meadow openings. Mean annualprecipitation ranges from 51 to 178 centimeters (20 to 70 inches). Theelevation range is 1,036 to 2,316 meters (3400 to 7600 feet). The dominantslopes range from 5 to 50 percent. This map unit is moderately to highlydissected by streams, with the dominant stream pattern being dendritic.Wetlands are a minor component of this unit.

LTA Components: This landtype association consists primarily of glacialmoraine landforms. Glacially scoured ridge tops are a minor component.

On the valley bottom landscape setting the glacial moraines occur on rollinghummocky topography, with slopes that range from 5 to 30 percent slope. On theupland landscape setting the glacial moraines occur on straight to slightlyconcave slopes, with range from 20 to 55 percent in gradient. These glacialmoraines typically occur as the toe-slope associated with glacial troughwalls.

Soils on these landforms are moderately deep to very deep, and are moderate tohighly developed, with gravelly moderately-fine or fine textures. The majorsoils are classified as Typic Eutrochrepts and Andeptic Cryoboralfs. Rockoutcrops occupy less than 15 percent of the area. The dominant potentialnatural vegetation is Douglas-fir and subalpine fir.

A minor component of this map unit is glacially scoured ridge tops. Slopegradients range from 5 to 20 percent. Soils on these landforms are shallow tomoderately deep, moderately developed, with gravelly medium textures. Themajor soils are classified as Andic Cryochrepts. Rock outcrops occupy lessthan 15 percent of the area. The dominant potential natural vegetation issubalpine fir and Douglas-fir.This component represents 15 percent of thismap unit.

Compiled by: Dean Sirucek, Flathead National Forest

LTA57-M332B

GLACIATED MOUNTAIN SLOPES: SCHISTS

Location: This unit is located in the Bitterroot Mountain Range of westernMontana in the Bitteroot River basin.



Differentiating Characteristics: This map unit occurs in the lower to middleelevation portions of glaciated valleys. Parent material is alpine glacialtill, alluvium, and colluvium derived from schist.

Accessory Characteristics: The primary soils are deep and very deep withcoarse to moderately coarse textures. Inclusions of shallow soils, rockoutcrop, and rubble land occur within this unit. The vegetation is a mosaic ofmoderately dry, moist, and wet coniferous forest. Mean annual precipitationranges from 41 to 102 centimeters (16 to 40 inches). The elevation range is1280 to 2317 meters (4200 to 7600 feet). Slope gradients range from 5 to 60percent. This unit is slightly to moderately dissected by streams, with thedominant stream pattern being trellis. Wetlands, seeps, bogs and riparianzones are major components of this unit.

LTA Components: This landtype association consists of lateral moraines andfootslopes, terraces and ground moraines, and floodplains.

Lateral moraines were formed in alpine glacial till. Footslopes consist ofcolluvium from trough walls. Slope gradients range from 30 to 60 percent.Soils on this landform are deep and moderately well to somewhat excessivelydrained. These soils are weakly developed and consist of cobbly loam to sandyloam surface layers overlying very cobbly sandy loam substrata. North-facingslopes have a cobbly loam volcanic ash surface layer. The dominant soils areclassified as: Andic Cryochrepts, Dystric Cryochrepts, and Typic Ustochrepts.Shallow soils, rock outcrop and rubble land occupy about 15 percent of thiscomponent. The most common potential vegetation is the subalpine fir andDouglas-fir series. This component represents about 60 percent of this unit.Ground moraines formed in moderately coarse glacial till on valley floors.Terraces formed in coarse outwash and alluvium and represent formerfloodplains. Slope gradients range from 8 to 35 percent. Soils on thislandform are very deep and well drained to excessively drained. These soilsare weakly developed and consist of cobbly to bouldery loam surface layersoverlying very cobbly to very bouldery sandy loam or loamy sand substrata. Thedominant soils are classified as Andic Cryochrepts, Dystric Cryochrepts, andOxyaquic Cryofluvents. Rock outcrop occurs on about 10 percent of thiscomponent. The dominant potential natural vegetation is the grand fir andsubalpine fir series. This component comprises about 25 percent of this unit.

Floodplains were formed in coarse alluvium. Slope gradients range from 5 to 10percent. Soils on this landform are very deep and poorly to very poorlydrained. These soils are very weakly developed and consist of cobbly loamsurface layers overlying very gravelly to extremely cobbly loamy sandsubstrata. The dominant soils are classified as: Typic Cryaquents, TypicCryaquepts, and Oxyaquic Cryofluvents. Rock outcrop occurs on less than 5percent of this component. The dominant natural vegetation is the westernredcedar, grand fir, and subalpine fir series. Included in this component areareas of silty wet soils in alluvial basins. These soils support alder,willow, and sedge plant communities. Floodplains represents about 15 percentof this unit.


LTA60-M332B

MOUNTAIN SLOPES AND RIDGES: METASEDIMENTARY (BELT)

Location: This unit is located in the Bitterroot, Sapphire, and Anacondamountain ranges of western Montana. It occurs in the Middle and Upper ClarkFork River Basin which includes the Bitterroot, Blackfoot, Flint Creek, andClark Fork drainages.

Acreage by Section

60-M332B 767,352


Differentiating characteristics: This map unit occurs in a nonglaciated steepmountain slope setting, below the zone of strong frost shattering, which istypically composed of moderately dissected mountain slopes, ridge tops, andnarrow valley bottoms. Parent materials are colluvium and residuum underlainby Precambrian Belt rocks such as argillite, quartzite, and siltite.

Accessory Characteristics: The primary soils are shallow to deep,medium-textured, and have numerous rocks fragments throughout the profile. Thevegetation is a mosaic of coniferous forest and native grasslands. Mean annualprecipitation ranges from 36 to 89 centimeters (14 to 35 inches). Theelevation range is 945 to 2073 meters (3100 to 6800 feet). The dominant slopeshave gradients of 10 to 55 percent. This unit is moderately dissected bystreams, with the dominant stream pattern being dendritic. Wetlands are aminor component of this unit.

LTA Components: This landtype association consists of mountain slopes, andridge tops.

Mountain slopes are formed in colluvium and residuum. Slope gradients rangefrom 35 to 55 percent. Soils on this landform are shallow to deep and welldrained. Soils are weakly developed in areas underlain by the coarse-texturedrock types, such as quartzite, and having cooler forested habitat types. Thesesoils have gravelly fine sandy loam surface layers and extremely cobbly finesandy loam substrata. Soils that formed in material derived from fine-texturedrocks, such as argillite, and having warmer forested or grassland habitat typesare well developed. These soils have gravelly loam surface layers and verycobbly sandy clay loam or clay loam substrata. The dominant soils areclassified as Typic and Lithic Ustochrepts, Dystric Cryochrepts, TypicEutroboralfs, and Lithic Argiborolls. Rock outcrop occurs on about 5 percentof this landscape component. The dominant potential natural vegetation isDouglas-fir, Idaho fescue and subalpine fir series. This component represents75 percent of this unit.

Mountain ridge tops are formed in residuum. Slope gradients range from 10 to35 percent. Soils on this landform are shallow to deep and well drained.These soils are similar to those described above for the mountain slopeslandscape component. Rock outcrop occurs on about 20 percent of this landscapecomponent. The dominant potential natural vegetation is Douglas-fir and Idahofescue series. This component represents 20 percent of this unit.


Chapter 6

LTA61-M332B

MOUNTAIN SLOPES AND RIDGES: HIGHLY WEATHERED GRANITICS

Location: This unit is located in the Bitterroot and Sapphire Mountains ofwest-central Montana in the Bitterroot River Basin



Differentiating characteristics: This map unit occurs in a non-glaciated,dissected mountain slope setting, below the zone of strong frost shattering,which is typically composed of steep mountain slopes, ridge tops, and narrowvalley bottoms. Parent materials are colluvium and residuum underlain byhighly weathered granitic bedrock.

Accessory Characteristics: The primary soils are deep, coarse, sandy soilsthat have numerous rock fragments in the form of weathered gravels andcobbles. The vegetation is a mosaic of coniferous forest and nativegrasslands. Mean annual precipitation ranges from 41 to 102 centimeters (16 to40 inches). The elevation range is 1158 to 2073 meters (3800 to 6800 feet).The dominant slopes have gradients of 10 to 55 percent. This unit is highlydissected by streams, with the dominant stream pattern being dendritic.Wetlands are a minor component of this unit.

LTA Components: This landtype association consists of steep mountain slopes,and ridge tops.

Steep mountain slopes are formed in colluvium. Slope gradients range from 30to 55 percent. Soils on this landform are deep and excessively drained. Thesesoils are weakly developed and consist of gravelly sandy loam surface layersoverlying very gravelly or very cobbly loamy sand substrata. The dominantsoils are classified as Typic Ustochrepts and Dystric Cryochrepts. Rockoutcrop occurs on about 5 percent of this landscape component. The dominantpotential natural vegetation is Douglas-fir and subalpine fir series. Thiscomponent represents 80 percent of this unit.

Ridge tops formed in residuum and colluvium. Slope gradients range from 10 to35 percent. Soils on this landform are shallow to deep and excessivelydrained. These soils are weakly developed and consist of gravelly or verygravelly sandy loam surface layers overlying very gravelly or very cobbly loamysand substrata. The dominant soils are classified as Lithic Ustochrepts, TypicUstochrepts, Dystric Cryochrepts, and Typic Haploborolls. Rock outcrop occurson about 10 percent of this landscape component. The dominant potentialnatural vegetation is Douglas-fir and Idaho fescue series. This componentrepresents 15 percent of this unit.


LTA62-M332B

MOUNTAIN SLOPES AND RIDGES: WEAKLY WEATHERED GRANITICS

Location: This unit is located in the Bitterroot, Sapphire, and Anacondamountain ranges of western Montana and occurs in the Bitterroot, Blackfoot, andUpper Clark Fork River basins.

Acreage by Section

62-M332B 152,086


Differentiating characteristics: This map unit occurs in a non-glaciated steepmountain slope landscape setting, below the zone of strong frost shattering,and is typically composed of moderately dissected mountain slopes, ridge tops,and minor amounts of narrow valley bottoms. Parent materials are colluvium andresiduum underlain by weakly weathered granitic bedrock.

Accessory Characteristics: The primary soils are shallow to deep, moderatelycoarse-textured, and have numerous rock fragments throughout the profile. Thevegetation is a mosaic of coniferous forest, native grasslands, and at thelowest elevations of the unit, dry shrublands. Mean annual precipitationranges from 41 to 89 centimeters (16 to 35 inches). The elevation range is1220 to 2012 meters (4000 to 6600 feet). The dominant slopes have gradients of10 to 55 percent. This unit is moderately dissected by streams, with thedominant stream pattern being dendritic. Wetlands are a minor component ofthis unit.

LTA Components: This landtype association consists of mountain slopes, andridge tops.

Mountain slopes are formed in colluvium and residuum. Slope gradients rangefrom 35 to 55 percent. Soils on this landform are shallow to deep and welldrained. These soils are weakly developed except that on warm, southeast towest-facing slopes, soils are more developed. The weakly developed soilsconsist of gravelly sandy loam surface layers overlying very cobbly sandy loamsubstrata. The more developed soils have a gravelly sandy loam surface layerthat overlies very gravelly or very cobbly sandy clay loam or clay loamsubstrata. The dominant soils are classified as Typic and Lithic Ustochrepts,Dystric Cryochrepts, Typic Eutroboralfs, and Lithic Argiborolls. Rock outcropoccurs on about 5 percent of this landscape component. The dominant potentialnatural vegetation is Douglas-fir, Idaho fescue, bitterbrush, and subalpine firseries. This component represents 75 percent of this unit.

Mountain ridge tops are formed in residuum. Slope gradients range from 10 to35 percent. Soils on this landform are shallow to deep and well drained.These soils are similar to those described above for the mountain slopeslandscape component. Rock outcrop occurs on about 20 percent of this landscapecomponent. The dominant potential natural vegetation is Douglas-fir,bitterbrush, and Idaho fescue series. This component represents 20 percent ofthis unit.


Chapter 6

LTA63-M332B

MOUNTAIN SLOPES AND RIDGES: SCHISTS AND GNEISSESS

Location: This unit is located in the Bitterroot Mountain Range ofwest-central Montana in the Bitterroot and Clark Fork River Basins.



Differentiating characteristics: This map unit occurs in a non-glaciated steepmountain slope landscape setting which is typically composed of steep mountainslopes, ridge tops, and minor amounts of landslides and narrow valley bottoms.These are mostly below the zone of strong frost shattering, but because oflimited acres, areas of high elevation frost shattered ridges were included inthe mapping of this unit. Parent materials are colluvium underlain by schistand gneiss with high amounts of mica.

Accessory Characteristics: The primary soils are deep with sandy loam texturesand numerous rock fragments in the profile. The vegetation is a mosaic ofconiferous forest with minor amounts of dry, coniferous savannah. Mean annualprecipitation ranges from 64 to 178 centimeters (25 to 70 inches). Theelevation range is 1524 to 2439 meters (5000 to 8000 feet). The dominantslopes have gradients of 25 to 55 percent. This unit is moderately dissectedby streams, with the dominant stream pattern being dendritic. Wetlands are aminor component of this unit.

LTA Components: This landtype association consists of steep mountain slopes,and moderately steep ridge tops.

Steep mountain slopes are formed in colluvium derived from schist and gneiss.A thin layer of volcanic ash occurs at the surface on slopes with northerlyaspects. Slope gradients range from 40 to 55 percent. Soils on this landformare deep and well drained. On southerly aspects, these soils are weaklydeveloped and consist of gravelly sandy loam surface layers overlying verycobbly fine sandy loam substrata. On northerly aspects the surface layer issilt loam derived from volcanic ash that overlies very gravelly to ver y cobbly loam or silt loam substrata. The dominant soils are classified as DystricCryochrepts, Andic Cryochrepts, and Typic Ustochrepts. Rock outcrop occurs onabout 5 percent of this landscape component. The dominant potential naturalvegetation is subalpine fir and Douglas-fir series. This component represents80 percent of this unit.

Mountain ridge tops and associated spur ridges are formed in residuum andcolluvium derived from schist or gneiss. Slope gradients range from 25 to 40percent. Soils on this landform are shallow to moderately deep and welldrained. These soils are weakly developed and consist of gravelly sandy loamsurface layers that overlie very cobbly to very flaggy fine sandy loamsubstrata. The dominant soils are classified as Lithic Argiborolls and DystricCryochrepts. Rock outcrop occurs on about 10 percent of this landscapecomponent. The dominant potential natural vegetation is Douglas -fir andsubalpine fir series. This component represents 15 percent of this unit.


LTA64-M332BeLTA64-M332BkLTA64-M332De

MOUNTAIN SLOPES AND RIDGES: VOLCANICS

Location: This LTA is located in the Sapphire and Boulder Mountains on theBeaverhead-Deerlodge and Helena National Forests in the upper Clark Fork RiverBasin in southwest Montana. It also occurs along the Continental Divide in theAlice-Nevada Mountains.


64-M332Be 12,983 64-M332Bk 7,098 64-M332De 6,116

Map Unit Setting and General Characteristics:

Differentiating Characteristics: This LTA occurs in a landscape setting whichis typically composed of mountain slopes and ridges. Parent materials areresiduum and colluvium underlain by rhyolite and tuff. Some ridges have ashinfluenced soils.

Accessory Characteristics: The primary soils are shallow to moderately deep.The primary soils have medium textured to moderately coarse textured surfacesand moderately coarse to coarse textured subsurface layers. The vegetation isa mosaic of coniferous forest and mountain grasslands. Mean annualprecipitation ranges from 46 to 75 centimeters (18 to 30 inches). Theelevation range of this LTA is 1677 to 2195 meters (5500 to 7200 feet). Thedominant slopes have gradients of 10 to 60 percent. This LTA is poorly tomoderately dissected by streams. Ridges are mostly undissected. Wetlands are aminor component of this LTA.

Landscape Components: This map unit consists of mountain slopes and ridges.

Mountain slopes and ridges are formed in volcanic bedrock. Slope gradientsrange from 10 to 60 percent. Soils on these landforms are shallow tomoderately deep and weakly to moderately developed. Surface textures rangefrom very gravelly sandy loam on steeper slopes to loams on volcanic ashinfluenced ridges. Subsurface textures are often very cobbly coarse sandy loamor extremely cobbly loamy sand. These soils are classified as Typic, Dystric,Andic, and Lithic Cryochrepts, Typic and Lithic Cryoboralfs, and Argic andLithic Cryoborolls. Rock outcrop occurs on 5 to 15 percent of this landscapecomponent. The dominant potential natural vegetation is rough fescue,Douglas-fir and subalpine fir series. This component represents 100 percent ofthis LTA.

Compiled by: Dave Ruppert, Beaverhead-Deerlodge National Forest, and LarryLaing, Helena National Forest

LTA64-M332B

MOUNTAIN SLOPES AND RIDGES: VOLCANICS

Location: This unit is located in the Bitterroot and Sapphire Mountain Rangesof west-central Montana in the Bitterroot, Blackfoot, and Clark Fork RiverBasins.

Acreage by Section

64-M332B 103,689 (Section except for M332Be and M332Bk)


Differentiating characteristics: This map unit occurs in a non-glaciated steepmountain slope landscape setting, below the zone of strong frost shattering,which is typically composed of steep mountain slopes, moderately steep ridgetops, and minor amounts of narrow valley bottoms. Parent materials arecolluvium and residuum underlain by volcanic andesites and rhyolites.

Accessory Characteristics: The primary soils are shallow to deep with loamytextures and numerous rock fragments throughout the profile. The vegetationis a mosaic of coniferous forest and dry native grasslands. Mean annualprecipitation ranges from 51 to 102 centimeters (20 to 40 inches). Theelevation range is 1524 to 2012 meters (5000 to 6600 feet). The dominantslopes have gradients of 20 to 55 percent. This unit is moderately dissectedby streams, with the dominant stream pattern being dendritic. Wetlands are aminor component of this unit.

LTA Components: This landtype association consists of steep mountain slopes,and moderately steep ridge tops.

Steep mountain slopes are formed in colluvium derived from andesite orrhyolite. Slope gradients range from 30 to 55 percent. Soils on this landformare deep and well drained. These soils mostly are well developed and consistof gravelly loam or sandy loam surface layers overlying very gravelly or verycobbly sandy clay loam or clay loam substrata. Similar soils are less welldeveloped and generally have very cobbly sandy loam substrata. The dominantsoils are classified as Typic Cryoboralfs, Typic Eutroboralfs, TypicUstochrepts, and Lithic Argiborolls. Rock outcrop occurs on about 5 percent ofthis landscape component. The dominant potential natural vegetation issubalpine fir, Douglas-fir, and Idaho fescue series. This component represents70 percent of this unit.

Mountain ridge tops and associated spur ridges are formed in residuum andcolluvium derived from andesite or rhyolite. Slope gradients range from 20 to30 percent. Soils on this landform are mostly shallow to moderately deep andwell drained. These soils are well developed and consist of gravelly loamsurface layers overlying very gravelly or very cobbly sandy clay loam or clayloam substrata. The dominant soils are classified as Lithic Argiborolls, TypicCryoboralfs, and Typic Eutroboralfs. Rock outcrop occurs on about 20 percentof this landscape component. The dominant potential natural vegetation isIdaho fescue, Douglas-fir and subalpine fir series. This component represents20 percent of this unit.


LTA65-M332B

MOUNTAIN SLOPES AND RIDGES: SOFT SEDIMENTARY ROCKS

Location: This LTA is located in the Flint Range in the upper Clark Fork RiverBasin in southwest Montana.

Acreage by Section

65-M332B 30,430


Differentiating Characteristics: This LTA occurs in a mountain landscapesetting, which is typically composed of stream dissected mountain slopes.Parent materials are residuum underlain by soft sedimentary rocks.

Accessory Characteristics: The primary soils are shallow and moderately deepwith cobbly loamy textures. The vegetation is a mosaic of coniferous forestand mountain grasslands. Mean annual precipitation ranges from 41 to 76centimeters (16 to 30 inches). The elevation range of this LTA is 1372 to 1829meters (4500 to 6000 feet). The dominant slopes have gradients of 10 to 40percent. This LTA is moderately dissected by streams, with the dominant streampattern being parallel. Wetlands are a minor component of this LTA.

LTA Components: This landtype association consists of stream dissectedmountain slopes.

Stream dissected mountain slopes are formed in soft sedimentary rocks. Slopegradients range from 10 to 50 percent. Soils on these landforms are shallowand moderately deep, moderately developed, with cobbly loamy textures. Thesesoils are classified as Typic Cryochrepts and Cryoboralfs, and Typic and ArgicCryoborolls. Rock outcrop occurs on about 5 percent of this landscapecomponent. The dominant potential natural vegetation is Idaho fescue andDouglas-fir series. This component represents 100 percent of this LTA.


Chapter 6

LTA66-M332B

MOUNTAIN SLOPES AND RIDGES: CARBONATES


Acreage by Section

66-M332B 78,732


Differentiating Characteristics: This LTA occurs in a mountain landscapesetting, which is typically composed of stream dissected mountain slopes.Parent materials are residuum and colluvium underlain by limestone bedrock.

Accessory Characteristics: The primary soils are shallow and moderately deepwith cobbly loamy textures. The vegetation is a mosaic of coniferous forestand mountain grasslands. Mean annual precipitation ranges from 41 to 64centimeters (16 to 25 inches). The elevation range of this LTA is 1677 to 2439meters (5500 to 8000 feet). The dominant slopes have gradients of 10 to 50percent. This LTA is moderately dissected by streams, with the dominant streampattern being parallel. Wetlands are a minor component of this LTA.


Stream dissected mountain slopes are formed in limestone bedrock. Slopegradients range from 10 to 50 percent. Soils on these landforms are shallowand moderately deep, moderately developed, with cobbly loamy textures. Thesesoils are classified as Argic and Typic Cryoborolls, and Lithic and TypicCryochrepts and Cryoboralfs. Rock outcrop occurs on about 10 percent of thislandscape component. The dominant potential natural vegetation is roughfescue, Idaho fescue, Douglas-fir, and subalpine fir/grouse series. Thiscomponent represents 100 percent of this LTA.


Chapter 6

LTA67-M332B

MOUNTAIN SLOPES AND RIDGES: CALC-SILICATES

Location: This unit is located in the Lower Bitterroot, Garnet, Sapphire andSwan Mountains which is in the Upper Clark Fork River Basin of northwestMontana.

Acreage by Section

67-M332B 72,462


Differentiating Characteristics: This map unit occurs on mountain sideslopeand ridge landscape settings, which are composed of structural mountain lands.Parent materials are moderately weathered calc-silicate belt materials. Rockoutcrop is a common feature in this unit.

Accessory Characteristics: The primary soils are shallow to moderately deeploams and sandy loams. The vegetation is a mosaic of coniferous forest andparklands with small amounts of scree. Mean annual precipitation ranges from51 to 152 centimeters (20 to 60 inches). The elevation range of this unit is985 to 2031 meters (3200 to 6600 feet). The dominant slopes have gradients ofless than 60 percent. This unit is moderately to highly dissected by streams,with the dominant stream pattern being parallel. Talus and rock outcrops aremajor components of this map unit.

LTA Components: This landtype association consists of structural mountainslopes and ridges.

These landforms are developing on moderately steep mountain slopes and ridges.The slope gradients range from 35 to 60 percent. Soils on these landforms areshallow to moderately deep and are medium textured. The major soils areclassified as Andic Dystric Eutrochrepts, Andic Cryochrepts, TypicEutroboralfs, Typic Ustochrepts, and Calcixerollic Xerochrepts. Rock outcropsoccupy less than 15 to over 50 percent of the area. The dominant potentialnatural vegetation is Douglas-fir, western red cedar, grand fir and subalpinefir series.

Compiled by: Skip Barndt, Lolo National Forest.

LTA68-M332B

MOUNTAIN SLOPES AND RIDGES: SANDSTONES AND SHALES

Location: This LTA is located in the Flint Range on the Beaverhead-DeerlodgeNational Forest in southwest Montana in the upper Clark Fork River Basin.

Acreage by Section

68-M332B 84,764


Differentiating Characteristics: This LTA occurs in a mountain landscapesetting, which is typically composed of stream dissected mountain slopes.Parent materials are residuum underlain by sandstone and shale bedrock.

Accessory Characteristics: The primary soils are shallow and moderately deepwith cobbly loamy textures. The vegetation is a mosaic of coniferous forestand grasslands. Mean annual precipitation ranges from 41 to 76 centimeters (16to 30 inches). The elevation range of this LTA is 1524 to 2134 meters (5000 to7000 feet). The dominant slopes have gradients of 10 to 50 percent. This LTAis moderately dissected by streams, with the dominant stream pattern beingparallel. Wetlands are a minor component of this LTA.


Stream dissected mountain slopes are formed in sandstone and shale bedrock.Slope gradients range from 10 to 50 percent. Soils on these landforms areshallow and moderately deep, moderately developed, and have cobbly loamytextures. These soils are classified as Typic and Lithic Cryochrepts andCryoboralfs; and Argic and Lithic Cryoborolls. Rock outcrop occurs on about 10percent of this landscape component. The dominant potential natural vegetationis rough fescue, Douglas-fir and subalpine fir series. This componentrepresents 100 percent of this LTA.


Chapter 6

LTA70-M332B

FROST SHATTERED MOUNTAIN RIDGE TOPS: METASEDIMENTARY (BELT)

Location: This unit is located in the Bitterroot, Sapphire, and AnacondaMountain Ranges of western Montana and occurs in the Bitterroot and Upper ClarkFork River Basins.



Differentiating characteristics: This map unit occurs in a high elevationmountain ridge landscape setting which is typically composed of frost shatteredridge tops and mountain slopes. Parent materials are colluvium and residuumunderlain by Precambrian sedimentary Belt rocks.

Accessory Characteristics: The primary soils are deep with fine sandy loamtextures that have numerous rock fragments in the profile. The vegetation is afairly uniform cover of coniferous forest. Mean annual precipitation rangesfrom 89 to 152 centimeters (35 to 60 inches). The elevation range is 2012 to2500 meters (6600 to 8200 feet). The dominant slopes have gradients of 10 to50 percent. This unit is slightly dissected by streams, with the dominantstream pattern being parallel, but as mapped, areas of dendritic drainagepattern also occur in about 30 percent of the unit. Wetlands are a minorcomponent of this unit.

LTA Components: This landtype association consists of frost shattered mountainslopes, and ridge tops.

Frost shattered mountain slopes are formed in a thin layer of wind-depositedvolcanic ash that overlies colluvium derived from Belt rocks such as quartzite,argillite, and siltite. Slope gradients range from 35 to 50 percent. Soils onthis landform are deep and well drained. These soils are weakly developed andconsist of gravelly or cobbly loam or silt loam surface layers and very cobblyto extremely cobbly fine sandy loam substrata. The dominant soils areclassified as Andic Cryochrepts and Dystric Cryochrepts. Rock outcrop occurson about 10 percent of this landscape component. The dominant potentialnatural vegetation is subalpine fir and whitebark pine-subalpine fir series.This component represents 60 percent of this unit.

Frost shattered ridge tops are formed in residuum and colluvium from quartzite,argillite, and siltite that has a thin veneer of volcanic ash loess at thesurface. Slope gradients range from 10 to 30 percent. Soils on this landformare deep and well drained. These soils are poorly developed and consist ofcobbly to extremely cobbly loam or silt loam surface layers that overlieextremely cobbly fine sandy loam substrata. The dominant soils are classifiedas Andic Cryochrepts and Dystric Cryochrepts. Rock outcrop occurs on about 5percent of this landscape component. The dominant potential natural vegetationis subalpine fir and whitebark pine-subalpine fir series. This componentrepresents 30 percent of this unit.


LTA71-M332B

FROST SHATTERED MOUNTAIN RIDGE TOPS: HIGHLY WEATHERED GRANITICS

Location: This unit is located in the Bitterroot and Anaconda Mountain Rangesof western Montana in the Bitterroot River Basin.



Differentiating characteristics: This map unit occurs in a high elevationmountain ridge landscape setting which is typically composed of frost shatteredridge tops and mountain slopes. Parent materials are colluvium and residuumunderlain by highly weathered granitic rocks.

Accessory Characteristics: The primary soils are deep with loamy sandtextures that have numerous pea-sized and cobble-sized rock fragments in theprofile. The vegetation is a fairly uniform cover of coniferous forest. Meanannual precipitation ranges from 76 to 152 centimeters (30 to 60 inches). Theelevation range is 1951 to 2439 meters (6400 to 8000 feet). The dominantslopes have gradients of 10 to 40 percent. This unit is slightly dissected bystreams, with the dominant stream pattern being dendritic. Wetlands are aminor component of this unit. Small areas of glaciation are included in thismap unit.


Frost shattered mountain slopes are formed in a thin layer of wind-depositedvolcanic ash that overlies colluvium derived from highly weathered graniticrocks. Slope gradients range from 30 to 40 percent. Soils on this landformare deep and somewhat excessively drained. These soils are weakly developedand consist of gravelly loam or silt loam surface layers and very gravellyloamy-sand or coarse sandy loam substrata. The dominant soils are classifiedas Andic Cryochrepts and Dystric Cryochrepts. Similar soils withloamy-skeletal, mixed substrata occur in this component. Bedrock is highlyweathered granitics (grus). Rock outcrop occurs on less than 5 percent of thislandscape component. The dominant potential natural vegetation is subalpinefir, and whitebark pine-subalpine fir series. This component represents 70percent of this unit.

Frost shattered ridge tops are formed in residuum and colluvium derived fromhighly weathered granitic rocks that has a thin veneer of volcanic ash loess atthe surface. Slope gradients range from 10 to 30 percent. Soils on thislandform are deep and somewhat excessively drained. These soils are poorlydeveloped and consist of gravelly loam or silt loam surface layers that overlievery gravelly loamy sand or coarse sandy loam substrata. The dominant soilsare classified as Andic Cryochrepts and Dystric Cryochrepts. Areas of soilshaving loamy-skeletal, mixed substrata also occur in this component. Bedrockis highly weathered granitics. Rock outcrop occurs on less than 5 percent ofthis landscape component. The dominant potential natural vegetation issubalpine fir and whitebark pine-subalpine fir series. This componentrepresents 25 percent of this unit.


LTA72-M332B

FROST SHATTERED MOUNTAIN RIDGE TOPS: WEAKLY WEATHERED GRANITICS

Location: This unit is located in the Bitterroot, Sapphire, and AnacondaMountain Ranges of western Montana in the Bitterroot and Upper Clark Fork RiverBasins.

Acreage by Section

72-M332B 94,500


Differentiating characteristics: This map unit occurs in a high elevationmountain ridge landscape setting which is typically composed of frost shatteredridge tops and mountain slopes. Parent materials are colluvium and residuumunderlain by weakly weathered granitic rocks.

Accessory Characteristics: The primary soils are deep with sandy loam texturesthat have numerous rock fragments in the profile. The vegetation is a fairlyuniform cover of coniferous forest. Mean annual precipitation ranges from 76to 152 centimeters (30 to 60 inches). The elevation range is 1676 to 2500meters (5500 to 8200 feet). The dominant slopes have gradients of 10 to 50percent. This unit is slightly dissected by streams, with the dominant streampattern being dendritic. Wetlands are a minor component of this unit. Smallareas of glaciation are included in this map unit.


Frost shattered mountain slopes are formed in a thin layer of windd -depositedvolcanic ash that overlies colluvium derived from weakly weathered graniticrocks. Slope gradients range from 30 to 40 percent. Soils on this landformare deep and well drained. These soils are weakly developed and consist ofgravelly loam or silt loam surface layers and very gravelly or very cobblysandy loam substrata. The dominant soils are classified as Andic Cryochreptsand Dystric Cryochrepts. Rock outcrop occurs on less than 5 percent of thislandscape component. The dominant potential natural vegetation is subalpinefir, and whitebark pine-subalpine fir series. This component represents 70percent of this unit.

Frost shattered ridge tops are formed in residuum and colluvium derived fromweakly weathered granitic rocks that has a thin veneer of volcanic ash loess atthe surface. Slope gradients range from 10 to 30 percent. Soils on thislandform are deep and well drained. These soils are poorly developed andconsist of gravelly loam or silt loam surface layers that overlie very gravellyor very cobbly sandy loam substrata. The dominant soils are classified asAndic Cryochrepts and Dystric Cryochrepts. Rock outcrop occurs on less than 5percent of this landscape component. The dominant potential natural vegetationis subalpine fir, and whitebark pine-subalpine fir plant associations. Thiscomponent represents 25 percent of this unit.


LTA73-M332B

FROST SHATTERED MOUNTAIN RIDGE TOPS: VOLCANICS

Location: This unit is located in the Bitterroot Mountain Range of westernMontana in the Bitterroot River Basin.

Acreage by Section

73-M332B 15,228


Differentiating characteristics: This map unit occurs in a high elevationmountain ridge landscape setting which is typically composed of frost shatteredridge tops and mountain slopes. Parent materials are colluvium and residuumunderlain by weakly weathered volcanic rocks.

Accessory Characteristics: The primary soils are deep with sandy loam texturesthat have numerous rock fragments in the profile. The vegetation is a fairlyuniform cover of coniferous forest. Mean annual precipitation ranges from 102to 140 centimeters (40 to 55 inches). The elevation range is 1951 to 2439meters (6400 to 8000 feet). The dominant slopes have gradients of 10 to 40percent. This unit is slightly dissected by streams, with the dominant streampattern being parallel. Wetlands are a minor component of this unit.


Frost shattered mountain slopes are formed in a thin layer of wind-depositedvolcanic ash that overlies colluvium derived from weakly weathered volcanicrocks. Slope gradients range from 30 to 40 percent. Soils on this landformare deep and well drained. These soils are weakly developed and consist ofgravelly loam or silt loam surface layers and very gravelly or very cobblysandy loam substrata. The dominant soils are classified as Andic Cryochreptsand Dystric Cryochrepts. Rock outcrop occurs on less than 5 percent of thislandscape component. The dominant potential natural vegetation is subalpinefir, and whitebark pine-subalpine fir series. This component represents 60percent of this unit.

Frost shattered ridge tops are formed in residuum and colluvium derived fromweakly weathered volcanic rocks that has a thin veneer of volcanic ash loess atthe surface. Slope gradients range from 10 to 20 percent. Soils on thislandform are deep and well drained. These soils are poorly developed andconsist of gravelly to extremely cobbly loam or silt loam surface layers thatoverlie very gravelly or very cobbly sandy loam substrata. The dominant soilsare classified as Andic Cryochrepts and Dystric Cryochrepts. Rock outcropoccurs on less than 5 percent of this landscape component. The dominantpotential natural vegetation is subalpine fir, and whitebark pine-subalpine firseries. This component represents 35 percent of this unit.


LTA74-M332B

FROST SHATTERED MOUNTAIN RIDGE TOPS: SANDSTONES AND SHALES

Location: This LTA is located in the Flint Range of the Beaverhead-DeerlodgeNational Forest in the upper Clark Fork River Basin in southwest Montana.

Acreage by Section

74-M332B 6,428


Differentiating Characteristics: This LTA occurs in a mountain landscapesetting, which is typically composed of frost shattered ridges and slopes.Parent materials are residuum and colluvium underlain by sandstone shale, andother mixed sedimentary bedrock.

Accessory Characteristics: The primary soils are shallow and moderately deepwith cobbly loamy textures. The vegetation is a mosaic of coniferous forestand mountain grasslands. Mean annual precipitation ranges from 51 to 76centimeters (20 to 30 inches). The elevation range of this LTA is 2134 to 2591meters (7000 to 8500 feet). The dominant slopes have gradients of 20 to 60percent. This LTA is slightly dissected by streams, with no apparent dominantstream pattern. Wetlands are a minor component of this LTA.

LTA Components: This landtype association consists of frost shattered ridgesand slopes.

Frost shattered ridges and slopes are formed in sandstone, shale and othermixed sedimentary bedrock. Slope gradients range from 10 to 50 percent. Soilson these landforms are shallow and moderately deep, weakly developed, withcobbly loamy textures. These soils are classified as Lithic, Argic, and TypicCryoborolls, and Typic Cryochrepts and Cryorthents. Rock outcrop occurs onabout 5 percent of this landscape component and scree occupies an equal, andsometimes larger, area. The dominant potential natural vegetation is roughfescue and subalpine fir series. This component represents 100 percent of thisLTA.


Chapter 6

LTA75-M332B

FROST SHATTERED MOUNTAIN RIDGE TOPS: CALC-SILICATES

Location: This unit is located in the Sapphire Mountain Range of west-centralMontana in the Bitterroot Basin.

Acreage by Section

75-M332B 15,252


Differentiating characteristics: This map unit occurs in a high elevationmountain ridge landscape setting which is typically composed of frost shatteredridge tops and mountain slopes. Parent materials are colluvium and residuumunderlain by Precambrian calc-silicate (calcium-bearing) and quartzitic rocks.

Accessory Characteristics: The primary soils are deep with fine sandy loam toclay loam textures that have numerous rock fragments in the profile. Thevegetation is a fairly uniform cover of coniferous forest. Mean annualprecipitation ranges from 89 to 127 centimeters (35 to 50 inches). Theelevation range is 1829 to 2439 meters (6000 to 8000 feet). The dominantslopes have gradients of 20 to 50 percent. This unit is slightly dissected bystreams, with the dominant stream pattern being dendritic; but as mapped, areasof parallel drainage pattern also occur in about 20 percent of the unit.Wetlands are a minor component of this unit.


Frost shattered mountain slopes are formed in a thin layer of wind-depositedvolcanic ash that overlies colluvium derived from calc-silicate and quartziticrocks. Slope gradients range from 35 to 50 percent. Soils on this landformare deep and well drained. These soils are weakly developed and consist ofgravelly or cobbly loam or silt loam surface layers and very cobbly toextremely cobbly fine sandy loam to clay loam substrata. The dominant soilsare classified as Andic Cryochrepts, Dystric Cryochrepts, and TypicCryoboralfs. Rock outcrop and scree occurs on about 5 percent of thislandscape component. The dominant potential natural vegetation is subalpinefir and whitebark pine-subalpine fir series. This component represents 75percent of this unit.

Frost shattered ridge tops are formed in residuum and colluvium fromcalc-silicate and quartzitic rocks that has a thin veneer of volcanic ash loessat the surface. Slope gradients range from 20 to 30 percent. Soils on thislandform are deep and well drained. These soils are poorly developed andconsist of cobbly to extremely cobbly loam or silt loam surface layers thatoverlie very cobbly fine sandy loam to clay loam substrata. The dominant soilsare classified as Andic Cryochrepts, Dystric Cryochrepts, and TypicCryoboralfs. Rock outcrop and scree occurs on about 5 percent of thislandscape component. The dominant potential natural vegetation is subalpinefir and whitebark pine-subalpine fir series. This component represents 20percent of this unit.


LTA80-M332B

LOW RELIEF HILLS: METASEDIMENTARY (BELT)

Location: This unit is located in the Philipsburg valley in the vicinity of theBeaverhead National Forest in southwest Montana. It occurs in the Upper ClarkFork River basin in Subsection M33Be.

Acreage by Section

80-M332B 4,768

Map Unit Setting and General Characteristics

Differentiating characteristics: This map unit occurs in a low relief mountainsetting and is typically composed of rolling hills. Parent materials areweathered Belt residuum and colluvium.

Accessory Characteristics: The primary soils are deep and loamy. Thevegetation is a mosaic of coniferous forest. Mean annual precipitationranges from 46 to 64 centimeters (18 to 25 inches). The elevation range ofthis unit is 1677 to 2134 meters (5500 to 7000 feet). The dominant slopes havegradients of 10 to 30 percent. This unit is highly dissected by streams, withthe stream pattern being strongl dendritic.

Landscape Components: This map unit consists of low relief rolling hills.

Low relief rolling hills are formed in metasediments that consist of quartzitesand siltites. The slope gradients range from 10 to 30 percent. Soils on theselandforms are deep, moderately to highly weathered and medium textured. Themajor soils on the well drained sites are classified as Typic and LithicCryochrepts and Cryoboralfs. The dominant potential natural vegetation isrough fescue, Douglas-fir and subalpine fir. This component represents 100percent of this unit.

Compiled by: Dave Ruppert, Beaverhead-Deer Lodge National Forest

LTA81-M332B

LOW RELIEF HILLS: HIGHLY WEATHERED GRANITICS

Location: This unit is located in the Bitterroot and Sapphire Mountain Rangesof west-central Montana in the Bitterroot River Basin.

Acreage by Section

81-M332B 105,939


Differentiating characteristics: This map unit occurs in a moderately steep,highly dissected mountain slope landscape setting which is typically composedof dissected slopes, ridge tops, and noses of spur ridges. Parent materialsare colluvium and residuum underlain by highly weathered granitic bedrock.

Accessory Characteristics: The primary soils are shallow to deep with loamysand to sandy clay loam textures and have numerous rock fragments throughoutthe profile. The vegetation is a mosaic of dry shrublands, grasslands, andconiferous forest. Mean annual precipitation ranges from 41 to 127 centimeters(16 to 50 inches). The elevation range is 1280 to 2348 meters (4200 to 7700feet). The dominant slopes have gradients of 5 to 40 percent. This unit ishighly dissected by streams, with the dominant stream pattern being dendritic.Wetlands are a minor component of this unit.

LTA Components: This landtype association consists of dissected mountainslopes, and ridge tops.

Dissected mountain slopes are formed in colluvium derived from highly weatheredgranite. Slope gradients range from 30 to 40 percent. Soils on this landformare moderately deep to deep and somewhat excessively to well drained. Thesesoils are poorly developed to well developed and consist of gravelly sandy loamsurface layer that overlies very gravelly to very cobbly loamy sand or sandyclay loam substrata. The dominant soils are classified as Dystric Cryochrepts,sandy-skeletal, mixed; Typic Ustochrepts, Typic Eutroboralfs, and AndicCryochrepts. Rock outcrop occurs on about 5 percent of this landscapecomponent. The dominant potential natural vegetation is Idaho fescue,Douglas-fir and subalpine fir series. This component represents 60 percent ofthis unit.

Ridge tops and associated noses of spur ridges are formed in residuum andcolluvium derived from highly weathered granite. Slope gradients range from 5to 20 percent. Soils on this landform are shallow to moderately deep and welldrained. These soils are poorly developed to well developed and consist ofgravelly or very gravelly sandy loam or loam surface layers over very gravellyor very cobbly sandy loam or sandy clay loam substrata. The dominant soils areclassified as Lithic Argiborolls, Lithic Eutroboralfs, Typic Ustochrepts, andDystric Cryochrepts. Rock outcrop occurs on about 10 percent of this landscapecomponent. The dominant potential natural vegetation is bitterbrush, Idahofescue, Douglas-fir and subalpine fir. This component represents 35 percent ofthis unit.


LTA82-M332B

LOW RELIEF HILLS: VOLCANICS

Location: This unit is located in the Bitterroot Mountain Range ofwest-central Montana in the Bitterroot River Basin.

Acreage by Section

82-M332B 10,401


Differentiating characteristics: This map unit occurs in a moderately steep,highly dissected mountain slope landscape setting which is typically composedof dissected slopes, ridge tops, and noses of spur ridges. Parent materialsare colluvium and residuum underlain by weakly weathered volcanic bedrock.

Accessory Characteristics: The primary soils are shallow to deep with loam toclay textures; rock content is highly variable throughout the profile. Thevegetation is a mosaic of coniferous forest with scattered patches ofconiferous savannah. Mean annual precipitation ranges from 64 to 102centimeters (25 to 40 inches). The elevation range is 1463 to 1951 meters(4800 to 6400 feet). The dominant slopes have gradients of 10 to 40 percent.This unit is highly dissected by streams, with the dominant stream patternbeing dendritic. Wetlands are a minor component of this unit.

LTA Components: This landtype association consists of dissected mountainslopes, and ridge tops.

Dissected mountain slopes are formed in colluvium derived from weakly weatheredrhyolitic and andesitic volcanic rocks. Slope gradients range from 20 to 40percent. Soils on this landform are moderately deep to deep and well drained.These soils are mostly well developed and consist of gravelly loam surfacelayer that overlies very gravelly to very cobbly sandy clay loam to claysubstrata. The dominant soils are classified as Typic Eutroboralfs, TypicEutroboralfs, and Typic Ustochrepts. Rock outcrop occurs on less than 5percent of this landscape component. The dominant potential natural vegetationis Douglas-fir and subalpine fir series. This component represents 70 percentof this unit.

Ridge tops and associated noses of spur ridges are formed in residuum andcolluvium derived from weakly weathered rhyolitic and andesitic volcanicrocks. Slope gradients range from 10 to 30 percent. Soils on this landformare shallow to moderately deep and well drained. These soils are welldeveloped and consist of gravelly or very gravelly sandy loam or loam surfacelayers over very gravelly or very cobbly clay loam or sandy clay loamsubstrata. The dominant soils are classified as Lithic Argiborolls, LithicEutroboralfs, and Typic Ustochrepts. Rock outcrop occurs on less 5 percent ofthis landscape component. The dominant potential natural vegetation isDouglas-fir series. This component represents 25 percent of this unit.


Chapter 6

LTA83-M332B

LOW RELIEF HILLS: FINE TERTIARY SEDIMENTS

Location: This unit is located in the Bitterroot and Sapphire Mountain Rangesof western Montana. It occurs in the Bitterroot, Blackfoot, and Upper ClarkFork River Basins. On the Helena National Forest it occurs in the Avon Valleyand the Nevada Creek and Sturgeon Creek drainages.

Acreage by Section

83-M332B 295,900


Differentiating characteristics: This map unit occurs in a moderately steep,highly dissected Tertiary-age valley fill landscape setting which is typicallycomposed of dissected slopes, ridge tops, and planar terrace treads. Parentmaterial is old, weathered alluvium derived from mixed sources.

Accessory Characteristics: The primary soils are deep with loam to clay loamtextures; rock content is highly variable throughout the profile. Thevegetation is a mosaic of native grassland and coniferous forest. Mean annualprecipitation ranges from 30 to 76 centimeters (12 to 30 inches). Theelevation range is 1067 to 1829 meters (3500 to 6000 feet). The dominantslopes have gradients of 5 to 50 percent. This unit is highly dissected bystreams, with the dominant stream pattern being dendritic. Wetlands are aminor component of this unit.

LTA Components: This landtype association consists of dissected terrace scarpslopes, and ridge tops/terrace treads.

Dissected terrace slopes are formed in alluvium derived from granitic, Belt,and volcanic rocks. Slope gradients range from 25 to 50 percent. Soils onthis landform are deep and well drained. These soils are mostly well developedand consist of a cobbly loam surface layer that overlies very cobbly loam orclay loam substrata. The dominant soils are classified as Aridic and TypicArgiborolls, Typic Haploborolls, and Typic Eutroboralfs. Rock outcrop occurson less than 1 percent of this landscape component. The dominant potentialnatural vegetation is rough fescue, big sagebrush, Idaho fescue and Douglas-firseries. This component represents 50 percent of this unit.

Ridge tops and terrace treads are formed in alluvium derived from mixed sourcessuch as granitic, volcanic, and Belt rocks. Slope gradients range from 5 to 25percent. Soils on this landform are deep and well or moderately well drained.These soils are well developed and consist of cobbly or very cobbly loamsurface layers over very cobbly clay loam or loam substrata. The dominantsoils are classified as Aridic and Typic Argiborolls, Typic Eutroboralfs, andTypic Eutroboralfs. Rock outcrop occurs on less 1 percent of this landscapecomponent. The dominant potential natural vegetation is rough fescue, bigsagebrush, and Douglas-fir series. This component represents 45 percent ofthis unit.


LTA90-M332Bk

MASS WASTED SLOPES: MIXED GEOLOGY

Location: This LTA is scattered throughout the Alice-Nevada Mountains withinthe Clark Fork basin.


90-M332Bk 4,177


Differentiating Characteristics: This LTA occurs in a mountainous landscapesetting, which is typically composed of mountain slopes and ridges. Parentmaterials are old landslide deposits underlain by well weathered volcanic andmetasedimentary rock.

Accessory Characteristics: The primary soils are very deep and have clayeysubsoils. The vegetation is coniferous forest. Mean annual precipitationranges from 50 to 63 centimeters (20 to 25 inches). The elevation range ofthis LTA is 1373 to 2012 meters (4500 to 6600 feet). The dominant slopes havegradients of 10 to 40 percent. This LTA is moderately to highly dissected bystreams, with the dominant stream pattern being deranged. Wetlands are a majorcomponent of this LTA.

LTA Components: This landtype association consists of landslides.

Landslides are formed in landslide deposits associated with well weatheredvolcanic and metasedimentary bedrock. Slope gradients range from 10 to 40percent. Soils on these landforms are very deep and well developed. They havemoderately fine textured surface layers and strong subsoil clay accumulations.They typically have silty clay loam surface textures. Subsoils are silty clayloam and silty clay with 15 to more than 35 percent rock (mostly gravel andcobble). These soils are classified as Mollic Cryoboralfs. Inclusions ofTypic Cryaquolls are in bogs. At lower elevations Typic Eutroboralfs are moretypical. The dominant potential natural vegetation is subalpine fir andDouglas-fir.


LTA90-M332Bd


Location: This LTA is located in the Flint Range on the Beaverhead-DeerlodgeNational Forest in the upper Clark Fork River basin in southwest Montana.


90-M332Bd 17,222


Differentiating Characteristics: This LTA occurs in a mountain landscapesetting, which is typically composed of slumps and landflows. Parent materialsare slump and landflow deposits underlain by glacial moraine and Tertiarysedimentary rocks.

Accessory Characteristics: The primary soils are deep, with loamy and clayeytextures. The vegetation is a mosaic of mountain meadows and coniferousforest. Mean annual precipitation ranges from 41 to 76 centimeters (16 to 30inches). The elevation range of this LTA is 1677 to 2287 meters (5500 to 7500feet). The dominant slopes have gradients of 10 to 35 percent. This LTA ishighly dissected by streams, with the dominant stream pattern being paralleland deranged. Wetlands are a major component of this LTA.

LTA Components: This landtype association consists of a complex of slumps andlandflows.

Slumps and landlows are formed in glacial moraine and Tertiary sedimentaryrocks. Slope gradients range from 10 to 45 percent. Soils on these landformsare deep, moderately developed, with loamy and clayey textures. These soilsare classified as Typic Cryoboralfs and Typic and Oxyaquic Cryochrepts. Rockoutcrop occurs on less than 1 percent of this landscape component. Thedominant potential natural vegetation is Douglas-fir and subalpine fir serieswith inclusions of hairgrass, sedge, and willow. This component represents 100percent of this LTA.


Chapter 6

LTA90-M332B


Location: This unit is located in the Bitterroot Mountain Range ofwest-central Montana and occurs in the Bitterroot River Basin.

Acreage by Section

90-M332B 7,375 (rest of Section except M332Bk and M332Bd)


Differentiating characteristics: This map unit occurs in a steep mountainslope landscape setting, which is typically composed of moist to wet masswasting and colluvial mountain slopes. Parent materials are landslide depositsand colluvium underlain by micaceous schist bedrock.

Accessory Characteristics: The primary soils are deep, loamy soils with highcontent of schist rocks. The vegetation is a mosaic of moist to wet coniferousforest. Mean annual precipitation ranges from 64 to 140 centimeters (25 to 55inches). The elevation range is 1585 to 2317 meters (5200 to 7600 feet). Thedominant slopes have gradients of 25 to 50 percent. This unit is moderatelydissected by streams, with the dominant stream pattern being incipientdendritic. Wetlands and ponds are a major component of this unit.

LTA Components: This landtype association consists of steep mountain slopes,and landslides.

Steep mountain slopes are formed in colluvium derived from micaceous schist.Slope gradients range from 35 to 50 percent. Soils on this landform are deepand well or moderately well drained. These soils are poorly developed andconsist of loam or silt loam surface layers overlying sandy loam or fine sandyloam substrata. The dominant soils are classified as Andic Cryochrepts andDystric Cryochrepts. Rock outcrop occurs on less than 5 percent of thislandscape component. The dominant potential natural vegetation is subalpinefir series. This component represents 70 percent of this unit.

Landslides are formed in unconsolidated landslide debris. Slope gradientsrange from 25 to 40 percent. Soils on this landform are deep and very poorlyto somewhat poorly drained. These soils are poorly developed and consist ofgravelly loam or silt loam surface layers that overlie very cobbly fine sandyloam or sandy loam substrata. The dominant soils are classified as TypicCryaquepts, Andic Cryochrepts, and Dystric Cryochrepts. Rock outcrop occurs onabout 5 percent of this landscape component. About 20% of this component iscomprised of soils having seasonally high water tables within a foot of thesurface. The dominant potential natural vegetation is subalpine fir series.This component represents 20 percent of this unit.


LTA92-M332BLTA92-M332ELTA92-M332D

COLLUVIAL DEPOSITS: MIXED GEOLOGY

Location: This LTA is located throughout the Helena National Forest.

Acreage by Section

92-M332B 6,383 92-M332E 3,557 92-M332D 12,928

Map Unit Setting and General Characteristics:

Differentiating Characteristics: This LTA occurs in a mountainous landscapesetting, which is typically composed of mountain slopes and ridges. Parentmaterials are colluvial deposits, in basins and on toeslopes, typicallyinfluenced by metasedimentary and volcanic rocks.

Accessory Characteristics: The primary soils are very deep and have loamy orclayey subsoils. The vegetation is coniferous forest. Mean annualprecipitation ranges from 38 to 75 centimeters (15 to 30 inches). Theelevation range of this LTA is 1464 to 2135 meters (4800 to 7000 feet). Thedominant slopes have gradients of 10 to 50 percent. This LTA is highlydissected (but weakly incised) by streams, with the dominant stream patternbeing parallel or subparallel. Wetlands are a major inclusion in this LTA.

Landscape Components: This map unit consists of one component:

Colluvial deposits are derived from metasedimentary and volcanic rock. Someareas are also influenced by limestone colluvium. Slope gradients range from10 to 50 percent. Soils on these landforms are very deep and weakly to welldeveloped. They have moderately fine textured surface layers and high subsoilclay accumulations. They typically have very cobbly loam or cobbly silt loamsurface textures. Subsoils are very cobbly loam, clay loam or silty clayloam. These soils are classified as Typic Cryochrepts, Typic Cryoboralfs, andArgic Cryoborolls. Inclusions of Aquic Cryoborolls, Aquic Cryoboralfs andTypic Cryaquepts are associated with seeps and springs. The dominant potentialnatural vegetation series are subalpine fir, spruce, and Douglas-fir.


Landtype Associations of the Northern Region

chapter 6 lta descriptions section m332b bitterroot...

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