Natural Resources
Conservation Service

Ecological site R224XY742AK

Subalpine Scrub Moist Slopes
Ecological Site Group

Last updated: 6/13/2025
Accessed: 09/23/2026

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General information

Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.

MLRA notes

Major Land Resource Area (MLRA): 224X–Cook Inlet Lowlands

Major Land Resource Area (MLRA) 224X consists of lowlands and lower mountain slopes of the Susitna and Matanuska Valleys, western Kenai Peninsula, and west side of Cook Inlet. It makes up about 10,965 square miles (28,400 square kilometers). The terrain is a broad expanse of braided flood plains, high gradient rivers, rolling plains, terraces and hills bordered by the surrounding mountains. This MLRA contains a large percentage of Alaska's total population and includes the most extensive road systems in the state. Major rivers include the Susitna, Yentna, Little Susitna, Matanuska, Kenai, and Deep Creek that all drain into Cook Inlet. Large lakes include Tustumena and Skilak.

Climate is highly variable ranging from temperate maritime to continental subarctic. Winter arctic weather systems are common in the northern portion of the MLRA. The average annual precipitation ranges from 15 to 60 inches (380 to 1,525 millimeters). The average annual snowfall is about 60 to 120 inches (150 to 305 centimeters). The average annual temperature is about 27 to 36 degrees F (-3 to 2 degrees C). The freeze-free period averages 65 to 160 days, decreasing with elevation.

Vegetation ranges from spruce/birch forests in the lowlands to subalpine scrubland at high elevations. Saltwater meadows along the coast and wetlands and extensive marsh occur throughout the lowlands across the valley. In most years precipitation is adequate for crops, with limited irrigation. Major rivers are affected by high sediment-laden glacial meltwater and ice dam damage and flooding is a risk during spring thaw. Water is hard or very hard, with high potential levels of iron, but is otherwise of excellent quality. Alpine vegetation is associated with the adjacent Cook Inlet Mountains MLRA (223X).

The dominant soil orders in this MLRA are Spodosols, Histosols, Entisols, and Inceptisols. Water, riverwash, beaches, and other miscellaneous (non-soil) areas are 15 percent of this MLRA. Glacial and volcanic ash wind-blown deposits influence much of area, while fluvial deposits are common in riparian areas.

The MLRA is visited by a great number of migrating birds and supports large populations of waterfowl. Most of the rivers and streams are important spawning grounds for salmon (Chinook, coho, and red salmon). Peonies, hay, potatoes, and hardy vegetables are important agriculture with a few dairy and beef cattle farms present. Commercial logging and subsistence firewood gathering are locally important, as is subsistence gathering. Other major industries in the area include commercial fishing, fish processing, and oil and gas extraction. Tourism and wildland recreation are becoming increasingly important.

The major resource concerns are water erosion and water quality. Aquifers are highly susceptible to contamination from runoff. The intrusion of seawater can be a problem along Cook Inlet. Rapid development and off-road recreation are creating significant damage to the wildlands.

LRU notes

This MLRA is a transitional zone between temperate maritime and continental subarctic climatic zones to the south and areas of arctic winter weather patterns to the north. With this transition, there are major variations in climatic influences and vegetative responses. With further soil survey and vegetative surveys, this MLRA will be evaluated for potential Land Resource Unit (LRU) development.

Ecological site concept

• This subalpine ecological site occurs on swales and mountain slopes.
• Soils formed in loess and/or volcanic ash over gravelly till, glacial drift and/or outwash.
• Soils range from deep to very deep, with depth controlled by bedrock.
• Soils do not flood or pond. These somewhat poorly drained soils have a shallow to moderately deep water table for extended portions of the growing season.
• Reference state vegetation is characterized as closed low scrub - low willow. This site has no known disturbance regimes and has one plant community within the reference state.

Associated sites

R223XY706AK	Alpine scrub wet depressions and drainageways Occurs in adjacent high-elevation drainages.
R224XY741AK	Subalpine Herbaceous Wet Slopes Ecological Site Group Occurs on adjacent subalpine slopes with wetter soils that support herbaceous meadows.
R224XY743AK	Subalpine Scrub Dry Slopes Ecological Site Group Occurs on adjacent subalpine slopes with drier soils that support a mosaic of Sitka alder scrubland and herbaceous meadows.

R223XY706AK

Alpine scrub wet depressions and drainageways

Occurs in adjacent high-elevation drainages.

R224XY741AK

Subalpine Herbaceous Wet Slopes Ecological Site Group

Occurs on adjacent subalpine slopes with wetter soils that support herbaceous meadows.

R224XY743AK

Subalpine Scrub Dry Slopes Ecological Site Group

Occurs on adjacent subalpine slopes with drier soils that support a mosaic of Sitka alder scrubland and herbaceous meadows.

Similar sites

R224XY743AK	Subalpine Scrub Dry Slopes Ecological Site Group Both 742 and 743 support shrubby plant communities. Ecological site group 743 supports tall scrub communities dominated by Sitka alder.

R224XY743AK

Subalpine Scrub Dry Slopes Ecological Site Group

Both 742 and 743 support shrubby plant communities. Ecological site group 743 supports tall scrub communities dominated by Sitka alder.

Table 1. Dominant plant species

Tree	Not specified
Shrub	(1) Salix barclayi (2) Salix pulchra
Herbaceous	(1) Calamagrostis canadensis (2) Gymnocarpium dryopteris

Download full description

Physiographic features

- Occurs on mountain slopes and swales on mountain slopes. Earth hummocks are occasional periglacial features, which are cored with silty mineral soil and are typically 4 to 20 inches in height and 8 to 125 inches in diameter (<a class="narrative-citation-link" href="https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_051068.pdf" target="_blank">Schoeneberger and Wysocki 2017</a>).
- Elevation typically ranges from 1,500 to 2,500 feet but can go to lower elevations on colder north facing slopes and to higher elevations on warmer south facing slopes.
- Flooding and ponding do not occur.
- A shallow to moderately deep water table occurs for extended portions of the growing season (16 to 32 inches).
- Slopes are moderately steep and occur on all aspects.
- Associated with low to very high amounts of runoff to adjacent, downslope ecological sites.

Table 2. Representative physiographic features

Hillslope profile	(1) Summit (2) Shoulder (3) Backslope
Landforms	(1) Mountains > Swale (2) Mountains > Mountain slope > Earth hummock
Runoff class	Low to very high
Flooding frequency	None
Ponding frequency	None
Elevation	1500 – 2500 ft
Slope	15 – 30 %
Water table depth	16 – 32 in
Aspect	W, NW, N, NE, E, SE, S, SW

Table 3. Representative physiographic features (actual ranges)

Runoff class	Not specified
Flooding frequency	Not specified
Ponding frequency	Not specified
Elevation	900 – 2500 ft
Slope	0 %
Water table depth	0 in

Climatic features

Climate is highly variable, generally ranging from temperate maritime to continental subarctic. Most weather systems originate in the North Pacific and the Gulf of Alaska. In winter, particularly in the northern part of the area, arctic weather systems are more common. In the Matanuska Valley, seasonal winds pick up fine-earth material from unvegetated flood plains and create extensive dust clouds that can reach an altitude of 5,000 feet (1,525 meters) or more. The average annual precipitation ranges from 15 to 60 inches (380 to 1,525 millimeters). It generally is higher on the southern Kenai Peninsula, in the northern Susitna Valley, and at the higher elevations along the mountains. The average annual snowfall is about 60 to 120 inches (150 to 305 centimeters). The average annual temperature is about 27 to 36 degrees F (-3 to 2 degrees C). The freeze-free period averages 65 to 160 days, decreasing in length with elevation. (USDA-NRCS 2022).

For detailed information visit the Natural Resources Conservation Service National Water and Climate Center at http://www.wcc.nrcs.usda.gov/. Point Mackenzie, Anchorage INTL AP, Talkeetna AP, Homer AP, and Kenai Muni AP are the representative climate stations. The following graphs and charts are a collective sample representing the averaged normals and 30-year annual rainfall data for the selected weather stations from 1981 to 2010.

Table 4 Representative climatic features

Frost-free period (characteristic range)	80-120 days
Freeze-free period (characteristic range)	120-140 days
Precipitation total (characteristic range)	20-30 in
Frost-free period (actual range)	80-120 days
Freeze-free period (actual range)	110-140 days
Precipitation total (actual range)	20-30 in
Frost-free period (average)	100 days
Freeze-free period (average)	130 days
Precipitation total (average)	20 in

Characteristic range

Actual range

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Figure 1. Monthly precipitation range

Characteristic range

Actual range

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Figure 2. Monthly minimum temperature range

Characteristic range

Actual range

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Figure 3. Monthly maximum temperature range

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Figure 4. Monthly average minimum and maximum temperature

Figure 5. Annual precipitation pattern

Figure 6 Annual average temperature pattern

Climate stations used

(1) TALKEETNA AP [USW00026528], Talkeetna, AK
(2) POINT MACKENZIE [USC00507444], Wasilla, AK
(3) ANCHORAGE INTL AP [USW00026451], Anchorage, AK
(4) KENAI MUNI AP [USW00026523], Kenai, AK
(5) HOMER AP [USW00025507], Homer, AK

Soil features

- Soils formed in loess and/or volcanic ash over gravelly till, glacial drift, and/or outwash.
- Rock fragments cover up to five percent of the soil surface.
- These mineral soils are capped with up to three inches of organic material. The surface mineral horizon texture is mucky silt loam or cobbly silt loam.
- Subsurface rock fragments range between 4 and 40 percent or more of the soil profile by volume.
- Soils are deep to very deep, which is controlled by bedrock. Strongly contrasting textural stratification is a restriction that occurs at very shallow to moderate depths (9 to 22 inches).
- Soils are acidic with the pH of the soil profile ranging from very strongly acidic to slightly acidic.
- Soils are considered somewhat poorly drained with very slow to moderately rapid permeability.

This Subalpine Scrub Moist Slopes Ecological Site Group is correlated to three soil components. These soils are classified as Inceptisols and Spodosols. The great group for Inceptisols is Eutrocryepts.

Table 5. Representative soil features

Parent material	(1) Volcanic ash (2) Loess (3) Till (4) Outwash (5) Drift
Surface texture	(1) Mucky silt loam (2) Cobbly silt loam
Drainage class	Somewhat poorly drained
Permeability class	Very slow to moderately rapid
Depth to restrictive layer	9 – 22 in
Soil depth	59 – 72 in
Surface fragment cover <=3"	0 – 9 %
Surface fragment cover >3"	0 – 5 %
Available water capacity (0-40in)	1.1 – 6.1 in
Calcium carbonate equivalent (10-40in)	Not specified
Clay content (0-20in)	5 %
Electrical conductivity (10-40in)	0 – 2 mmhos/cm
Sodium adsorption ratio (10-40in)	Not specified
Soil reaction (1:1 water) (10-40in)	4.5 – 6.5
Subsurface fragment volume <=3" (0-60in)	1 – 31 %
Subsurface fragment volume >3" (0-60in)	4 – 11 %

Table 6. Representative soil features (actual values)

Drainage class	Not specified
Permeability class	Not specified
Depth to restrictive layer	0 in
Soil depth	0 in
Surface fragment cover <=3"	0 %
Surface fragment cover >3"	0 %
Available water capacity (0-40in)	0 in
Calcium carbonate equivalent (10-40in)	0 %
Clay content (0-20in)	0 %
Electrical conductivity (10-40in)	0 mmhos/cm
Sodium adsorption ratio (10-40in)	0
Soil reaction (1:1 water) (10-40in)	0
Subsurface fragment volume <=3" (0-60in)	0 %
Subsurface fragment volume >3" (0-60in)	4 – 22 %

Ecological dynamics

Located in the subalpine life zone, ecological site R224XY743AK is exposed to a variety of harsh conditions including high winds, persistent snowpack, and extremely cold temperatures. Persistent snowpack and cold temperatures reduce the growing season in the subalpine, when compared to lower elevations. These harsh climate conditions result in dominance of scrub and herbaceous communities and limit tree growth and reproduction.

State and transition model

More interactive model formats are also available. View Interactive Models
Click on state and transition labels to scroll to the respective text

Ecosystem states

1. Reference

State 1 submodel, plant communities

1.1. willow/western oakfern/bluejoint

State 1
Reference

The reference plant community is characterized as closed low scrub - low willow (Viereck et al. 1992). This site has no known associated disturbance regimes and has one plant community within the reference state.

The vegetation modeled for this site has limited data and is considered provisional.

Dominant plant species

willow (Salix), shrub
bluejoint (Calamagrostis canadensis), grass
western oakfern (Gymnocarpium dryopteris), other herbaceous

Community 1.1
willow/western oakfern/bluejoint

Vegetation consists of dense low willow scrub. Associated herbaceous cover varies from sparse to moderately abundant. Common plant species include bluejoint reedgrass, Altai’s fescue, northern geranium, false hellebore, Canadian burnet, and oak fern.

Dominant plant species

Barclay's willow (Salix barclayi), shrub
tealeaf willow (Salix pulchra), shrub
Richardson's willow (Salix richardsonii), shrub
netleaf willow (Salix reticulata), shrub
feltleaf willow (Salix alaxensis), shrub
beauverd spirea (Spiraea stevenii), shrub
bluejoint (Calamagrostis canadensis), grass
Altai fescue (Festuca altaica), grass
sedge (Carex), grass
woolly geranium (Geranium erianthum), other herbaceous
green false hellebore (Veratrum viride), other herbaceous
Canadian burnet (Sanguisorba canadensis), other herbaceous
western oakfern (Gymnocarpium dryopteris), other herbaceous
common ladyfern (Athyrium filix-femina), other herbaceous
field horsetail (Equisetum arvense), other herbaceous
yellow thimbleweed (Anemone richardsonii), other herbaceous
dwarf marsh violet (Viola epipsila), other herbaceous
Aleutian violet (Viola langsdorffii), other herbaceous
western cordilleran bunchberry (Cornus unalaschkensis), other herbaceous
arctic raspberry (Rubus arcticus), other herbaceous

Table 7. Ground cover

Tree foliar cover	0%
Shrub/vine/liana foliar cover	0-80%
Grass/grasslike foliar cover	0-40%
Forb foliar cover	0-40%
Non-vascular plants	0-80%
Biological crusts	0%
Litter	0-70%
Surface fragments >0.25" and <=3"	0%
Surface fragments >3"	0-10%
Bedrock	0%
Water	0%
Bare ground	0%

Table 8. Canopy structure (% cover)

Height Above Ground (ft)	Tree	Shrub/Vine	Grass/ Grasslike	Forb
<0.5	–	–	–	–
>0.5 <= 1	–	–	–	2-40%
>1 <= 2	–	–	1-40%	–
>2 <= 4.5	–	–	–	–
>4.5 <= 13	–	20-80%	–	–
>13 <= 40	–	–	–	–
>40 <= 80	–	–	–	–
>80 <= 120	–	–	–	–
>120	–	–	–	–

Figure 7. Plant community growth curve (percent production by month). AK0022 , Southern. 60-200 days.

Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
J	F	M	A	M	J	J	A	S	O	N	D
0	0	0	0	10	30	45	10	5	0	0	0

Additional community tables

Table 9. Community 1.1 plant community composition

Group	Common name	Symbol	Scientific name	Annual production ()	Foliar cover (%)

Table 10. Community 1.1 forest understory composition

Common name	Symbol	Scientific name	Nativity	Height (ft)	Canopy cover (%)
Grass/grass-like (Graminoids)
bluejoint	CACA4	Calamagrostis canadensis	Native	–	1–40
Altai fescue	FEAL	Festuca altaica	Native	–	1–25
Fern/fern ally
western oakfern	GYDR	Gymnocarpium dryopteris	Native	–	2–40
Shrub/Subshrub
Barclay's willow	SABA3	Salix barclayi	Native	–	20–65
feltleaf willow	SAAL	Salix alaxensis	Native	–	5–40

Interpretations

Animal community

not available

Hydrological functions

not available

Recreational uses

not available

Wood products

not available

Other products

not available

Other information

not available

Supporting information

Inventory data references

The vegetation modeled for this site has limited data and is considered provisional. The associated model was largely developed from NRCS staff with working knowledge of the area and literature review. The narratives, tables, state-and-transition model, and dominant species are largely based on project concepts from the following soil surveys: Denali National Park Area, Alaska (Clark and Duffy 2006) and Matanuska-Susitna Valley Area, Alaska.

References

Clark, M.H. and M.S. Duffy1980. Soil Survey of Denali National Park Area, Alaska.. USDA NRCS.
Schoeneberger, P.J. and D.A. Wysocki. 2017. Geomorphic Description
System, Version 5.0..
Smith, R.D., A.P. Ammann, C.C. Bartoldus, and M.M. Brinson. 1995. An approach for assessing wetland functions using hydrogeomorphic classification, reference wetlands, and functional indices.
Viereck, L.A., C. T. Dyrness, A. R. Batten, and K. J. Wenzlick. 1992. The Alaska vegetation classification. U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station General Technical Report PNW-GTR-286..

Other references

Bailey, R.G. 1995. Ecoregions of North America. U.S. Department of Agriculture, Forest Service, Washington, DC, map scale 1: 15,000,000. Available at https://www.fs.fed.us/rm/ecoregions/products/map-ecoregions-north-america/.

Boggs, K.W., S.C. Klein, J.E. Grunblatt, G.P. Streveler, and B. Koltun. 2008. Landcover Classes and Plant Associations of Glacier Bay National Park and Preserve. Natural Resource Technical Report NPR/GLBA/NRTR-2008/093. National Park Service, Fort Collins, CO. 254 pps.

Boggs, K., S.C. Klein, J. Grunblatt, T. Boucher, B. Koltun, M. Sturdy, and G.P. Streveler. 2010. Alpine and subalpine vegetation chronosequences following deglaciation in coastal Alaska. Arctic, Antarctic, and Alpine Research 42: 385-395.

Boggs, K., L. Flagstad, T. Boucher, T. Kuo, M. Aisu, J. Tande, and J. Michaelson. 2016. Vegetation Map and Classification: Southern Alaska and Aleutian Islands. Alaska Natural Heritage Program, Alaska Center for Conservation Science, University of Alaska Anchorage. 90 pps.

Carsten, R. 2007. Chapter 5.2 Terrestrial habitats of Southeast Alaska. In: Schoen, J.W. and E. Dovichin (eds). The Coastal Forests and Mountains Ecoregion of Southeastern Alaska and the Tongass National Forest: A Conservation Assessment and Resource Synthesis. Audubon Alaska and The Nature Conservancy, Anchorage, AK.

Gallant, A.L., E.F. Binnian, J.M. Omernick, and M.B. Shasby. 2010. Level III Ecoregions of Alaska. Corvallis, OR, U.S. EPA, National Health and Environmental Effects Research Laboratory, map scale 1: 5,000,000. Available at http://www.epa.gov/eco-research//ecoregion-download-files-state-region-10. (Accessed 11 September 2018).

Kauffman, D.S., N.E. young, J.P. Briner, and W.F. Manley. 2011. Alaska Palaeo-Glacier Atlas (Version 2), pps. 427-445. In: Ehlers, J., P.L. Gibbard, and P.D. Hughes (eds.). Developments in Quaternary Science, Volume 15. Amsterdam, The Netherlands.

LANDFIRE. 2024. Biophysical Setting 16160 Western North American Boreal Riparian Stinger Forest and Shrubland. In: LANDFIRE National Vegetation Dynamics Models. USDA Forest Service and US Department of Interior. Washington, DC.

LANDFIRE. 2024. Biophysical Setting 16150 Western North American Boreal Lowland Large River Floodplain Forest and Shrubland. In: LANDFIRE National Vegetation Dynamics Models. USDA Forest Service and US Department of Interior. Washington, DC.

LANDFIRE. 2024. Biophysical Setting 16142 Western North American Boreal Montane Floodplain Forest and Shrubland - Boreal Transition. In: LANDFIRE National Vegetation Dynamics Models. USDA Forest Service and US Department of Interior. Washington, DC.

LANDFIRE. 2024. Biophysical Setting 16760 Alaskan Pacific Maritime Alpine Floodplain. In: LANDFIRE National Vegetation Dynamics Models. USDA Forest Service and US Department of Interior. Washington, DC.

LANDFIRE. 2024. Biophysical Setting 16550 Alaskan Pacific Maritime Floodplain Forest and Shrubland. In: LANDFIRE National Vegetation Dynamics Models. USDA Forest Service and US Department of Interior. Washington, DC.

NatureServe. 2018. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1 NatureServe, Arlington, VA. Available at http://explorer.natureserve.org. (Accessed 10 September 2018).

Peel, M.C., B.L. Finlayson, and T.A. McMahon. 2007. Updated world map of the Köppen-Geiger climate classification. Hydrology and Earth System Sciences 11: 1633-1644.

United States Department of Agriculture – Natural Resources Conservation Service (USDA-NRCS). 2006. Land Resource Regions and Major Land Resource Areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296. 682 pps.

Wahrhaftig, C. 1965. Physiographic Divisions of Alaska. Geological Survey Professional paper 482. U.S. Department of the Interior, Geological Survey, U.S. Government Printing Office, Washington, DC. 52 pps.

United States Department of Agriculture Staff. Hydrogeomorphic Wetland Classification System: An Overview and Modification to Better Meet the Needs of the Natural Resources Conservation Service. 2008

Contributors

Marji Patz
Blaine Spellman

Approval

Blaine Spellman, 6/13/2025

Acknowledgments

The original site concepts for the Loamy slopes was created and published by Karin Sonnen, the State Grazing/Rangeland Management Specialist for Alaska in May of 2010.

Rangeland health reference sheet

Interpreting Indicators of Rangeland Health is a qualitative assessment protocol used to determine ecosystem condition based on benchmark characteristics described in the Reference Sheet. A suite of 17 (or more) indicators are typically considered in an assessment. The ecological site(s) representative of an assessment location must be known prior to applying the protocol and must be verified based on soils and climate. Current plant community cannot be used to identify the ecological site.

Author(s)/participant(s)
Contact for lead author
Date	09/23/2026
Approved by
Approval date
Composition (Indicators 10 and 12) based on	Annual Production

Indicators

Number and extent of rills:
Presence of water flow patterns:
Number and height of erosional pedestals or terracettes:
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Number of gullies and erosion associated with gullies:
Extent of wind scoured, blowouts and/or depositional areas:
Amount of litter movement (describe size and distance expected to travel):
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
Functional/Structural Groups (list in order of descending dominance by above-ground annual-production or live foliar cover using symbols: >>, >, = to indicate much greater than, greater than, and equal to):

Dominant:

Sub-dominant:

Other:

Additional:
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Average percent litter cover (%) and depth ( in):
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
Potential invasive (including noxious) species (native and non-native). List species which BOTH characterize degraded states and have the potential to become a dominant or co-dominant species on the ecological site if their future establishment and growth is not actively controlled by management interventions. Species that become dominant for only one to several years (e.g., short-term response to drought or wildfire) are not invasive plants. Note that unlike other indicators, we are describing what is NOT expected in the reference state for the ecological site:
Perennial plant reproductive capability:

Download reference sheet

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Ecological site R224XY742AK

Subalpine Scrub Moist Slopes Ecological Site Group

Last updated: 6/13/2025 Accessed: 09/23/2026

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General information

MLRA notes

LRU notes

Ecological site concept

Associated sites

Similar sites

Table 1. Dominant plant species

Natural Resources
Conservation Service

Subalpine Scrub Moist Slopes
Ecological Site Group

Last updated: 6/13/2025
Accessed: 09/23/2026