Natural Resources
Conservation Service

Ecological site R236XY106AK

Subarctic Dwarf Scrub Dry Loamy Slopes

Last updated: 2/13/2024
Accessed: 04/29/2024

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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): 236X–Bristol Bay-Northern Alaska Peninsula Lowlands

The Bristol Bay-Northern Alaska Peninsula Lowland Major Land Resource Area (MLRA 236) is located in Western Alaska. This MLRA covers approximately 19,500 square miles and is defined by an expanse of nearly level to rolling lowlands, uplands and low to moderate hills bordered by long, mountain footslopes. Major rivers include the Egegik, Mulchatna, Naknek, Nushagak, and Wood River. MLRA 236 is in the zone of discontinuous permafrost. It is primarily in areas with finer textured soils on terraces, rolling uplands and footslopes. This MLRA was glaciated during the early to middle Pleistocene. Moraine and glaciofluvial deposits cover around sixty percent of the MLRA. Alluvium and coastal deposits make up a large portion of the remaining area (Kautz et al., 2012; USDA, 2006).

Climate patterns across this MLRA shift as one moves away from the coast. A maritime climate is prominent along the coast, while continental weather, commonly associated with Interior Alaska, is more influential inland. Across the MLRA, summers are general short and warm while winters are long and cold. Mean annual precipitation is 13 to 50 inches, with increased precipitation at higher elevations and areas away from the coast. Mean annual temperatures is between 30 and 36 degrees F (USDA, 2006).

The Bristol Bay-Northern Alaska Peninsula MLRA is principally undeveloped wilderness. Federally managed land includes parts of the Katmai and Aniakchak National Parks, and the Alaska Peninsula, Becharof, Togiak and Alaska Maritime National Wildlife Refuges. The MLRA is sparsely populated. Principal communities include Dillingham, Naknek, and King Salmon. Commercial fishing in Bristol Bay and the Bering Sea comprises a major part of economic activity in the MLRA. Other land uses include subsistence activities (fishing, hunting, and gathering) and sport hunting and fishing (USDA, 2006).

Ecological site concept

This ecological site is on hill shoulders and lower mountain slopes. Site elevation is typically between 450 and 1,850 feet above sea level. Slopes vary widely, from nearly level to steep.. Wind exposure, slope stability, soil acidity, low soil development/productivity, and andic properties favor the reference community of ericaceous shrubs. There is no determined disturbance regime, though fire may occur under rare, drier conditions.

The reference state supports one community. The reference plant community is characterized as a closed ericaceous scrubland (Viereck et al., 1992). It is composed of a dense mix of low and dwarf shrubs with sporadic graminoids and forbs throughout.

Associated sites

F236XY139AK	Boreal Woodland Loamy Rises F236XY139AK describes boreal forests on slopes. It abuts this site on some hill slopes.
R236XY151AK	Subarctic Open Willow Loamy Plain Swales R236XY151AK describes swales on hills and plains. It is a relatively smaller landform feature that can be surrounded by R236XY106AK on the landscape.
R236XY105AK	Subarctic Scrub Mosaic Gravelly Hillslopes R236Xy105AK describes alder hillslopes. It can be found on the same landscape as this site. Differences in site biotic and abiotic factors differentiate the vegetation between these sites.

F236XY139AK

Boreal Woodland Loamy Rises

F236XY139AK describes boreal forests on slopes. It abuts this site on some hill slopes.

R236XY151AK

Subarctic Open Willow Loamy Plain Swales

R236XY151AK describes swales on hills and plains. It is a relatively smaller landform feature that can be surrounded by R236XY106AK on the landscape.

R236XY105AK

Subarctic Scrub Mosaic Gravelly Hillslopes

R236Xy105AK describes alder hillslopes. It can be found on the same landscape as this site. Differences in site biotic and abiotic factors differentiate the vegetation between these sites.

Similar sites

R236XY132AK	Subarctic Dwarf Scrub Dry Loamy Slopes Both sites support similar shrub and graminoid species in the reference plant community. R236XY132AK is described at higher elevations on mountains where it is subject to grazing pressure and wind exposure. These disturbance pressures are not associated with this site. Soil pH, parent material, and soil hydrology help differentiate these sites.

R236XY132AK

Subarctic Dwarf Scrub Dry Loamy Slopes

Both sites support similar shrub and graminoid species in the reference plant community. R236XY132AK is described at higher elevations on mountains where it is subject to grazing pressure and wind exposure. These disturbance pressures are not associated with this site. Soil pH, parent material, and soil hydrology help differentiate these sites.

Table 1. Dominant plant species

Tree	Not specified
Shrub	(1) Empetrum nigrum (2) Betula nana
Herbaceous	(1) Carex bigelowii (2) Calamagrostis canadensis

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Physiographic features

This site is on slopes of hillslope shoulders and lower mountainflanks. Elevation ranges from 450 to 1,820 feet above sea level. Slopes are nearly level to steep (3 – 39 percent). This site is found at all aspects. Flooding and ponding do not affect this site.

Table 2. Representative physiographic features

Hillslope profile	(1) Shoulder
Geomorphic position, mountains	(1) Lower third of mountainflank
Geomorphic position, hills	(1) Crest
Landforms	(1) Mountains > Mountain slope (2) Hills > Hill (3) Plains > Hill
Runoff class	Medium to high
Flooding frequency	None
Ponding frequency	None
Elevation	450 – 1,820 ft
Slope	3 – 39%
Water table depth	60 in
Aspect	W, NW, N, NE, E, SE, S, SW

Table 3. Representative physiographic features (actual ranges)

Runoff class	Low to high
Flooding frequency	None
Ponding frequency	None
Elevation	290 – 1,970 ft
Slope	3 – 40%
Water table depth	60 in

Climatic features

The climate of this site reflects that of the MLRA, which is described as maritime polar (EPA, 2013). Temperatures are moderated by the nearby Bristol Bay and norther Pacific bodies of water. Annual precipitation ranges from 21 – 34 inches with approximately 40 percent occurring during the June-September growing season (PRISM, 2018).

Table 4. Representative climatic features

Frost-free period (characteristic range)	75-100 days
Freeze-free period (characteristic range)	65-90 days
Precipitation total (characteristic range)	21-34 in
Frost-free period (actual range)	75-100 days
Freeze-free period (actual range)	65-90 days
Precipitation total (actual range)	15-41 in
Frost-free period (average)	90 days
Freeze-free period (average)	75 days
Precipitation total (average)	29 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

Soil features

These Humicryods are extremely to moderately acidic and support a minimally developed ochric epipedon, a leached albic horizon, and contain andic soil properties (Soil Survey Staff, 2013). Soils are very deep and well drained. They support a cryic temperature regime and an udic moisture regime. Parent material is loess over till or volcanic ash over drift.

Soil characteristics affecting vegetation include low soil pH, low soil productivity, and andic soil properties. Strongly to extremely acidic soils restrict vegetation. Soil productivity is low in the ochric epipedon, which also restricts vegetation types and species. Andic soil properties generally have a high water holding capacity, but low available phosphorus for plants (Soil Survey Staff, 2013). In total, these conditions favor the ericaceous shrubs found int eh reference state.

Correlated soil components in MLRA 236: Nishlik, D36-Western maritime low scrub loamy glaciated slopes

Table 5. Representative soil features

Parent material	(1) Till
Surface texture	(1) Highly organic silt loam
Drainage class	Well drained
Permeability class	Moderate
Soil depth	60 in
Surface fragment cover <=3"	Not specified
Surface fragment cover >3"	Not specified
Available water capacity (0-10in)	2 – 2.8 in
Soil reaction (1:1 water) (0-10in)	3.7 – 6.4
Subsurface fragment volume <=3" (Depth not specified)	30%
Subsurface fragment volume >3" (Depth not specified)	3%

Table 6. Representative soil features (actual values)

Drainage class	Well drained
Permeability class	Moderate
Soil depth	60 in
Surface fragment cover <=3"	Not specified
Surface fragment cover >3"	Not specified
Available water capacity (0-10in)	1.3 – 2.8 in
Soil reaction (1:1 water) (0-10in)	3.7 – 6.4
Subsurface fragment volume <=3" (Depth not specified)	30%
Subsurface fragment volume >3" (Depth not specified)	3%

Ecological dynamics

This site is on stable hillslope shoulders and lower mountain flanks. It occurs at a wide range of elevations (450 to 1,800 feet above sea level) and slope gradients (nearly level to steep). Exposure on these landforms favors low and dwarf shrubs. Low soil pH and low soil productivity restrict plant life. Moderately to strongly acidic soil selects for plants that thrive in these conditions, particularly the ericaceous shrubs that comprise most of the vegetative cover of this site. Poor soil conditions also shape the plant community. The top six inches of soil support a minimally developed ochric epipedon and andic soil properties between six and eleven inches restricts available phosphorus (Soil Survey Staff, 2013). Soil is well drained but andic soil properties increase the available water capacity on this site, so vegetation is typically not hydrologically restricted.

This site is stable and there is no evidence of a unique post-disturbance community. It may be susceptible to fire under rare, drier conditions. Shrubs and willows may be browsed by moose or caribou. This does not appear to affect the ecological processes of the site.

The information in this Ecological Dynamics section, including the state-and-transition model (STM), was developed based on current field data, professional experience, and a review of the scientific literature. As a result, all possible scenarios or plant species may not be included. Key indicator plant species, disturbances, and ecological processes are described to inform land management decisions.

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

State 1 submodel, plant communities

1.1. Black crowberry-dwarf birch

State 1
Reference State

The reference state supports one community phase, which is distinguished by the developed structure and dominance of the vegetation and by its ecological function and stability. The reference community phase is dense scrubland. No known disturbance regime is associated with this site. This report provides baseline inventory data for the vegetation in this ecological site. Future data collection is needed to provide further information about existing plant communities and the disturbance regimes that result in transitions from one community to another. Common and scientific names are from the USDA PLANTS database. Community phases are characterized by the Alaska Vegetation Classification System (Viereck et al., 1992).

Community 1.1
Black crowberry-dwarf birch

Figure 7. Typical area of community 1.1.

Figure 8. Frequency and canopy cover of plants in community 1.1.

The reference plant community is closed low scrubland (Viereck et al., 1992). It consists of black crowberry (Empetrum nigrum),dwarf birch (Betula nana), marsh Labrador tea (Ledum palustre ssp. decumbens), and bog blueberry (Vaccinium uliginosum). Other species may include spirea (Spiraea stevenii), lingonberry (Vaccinium vitis-idaea), tealeaf willow (Salix pulchra), bluejoint (Calamagrostis canadensis), and sedges (Carex spp.). Black spruce (Picea mariana) may encroach this site where it abuts neighboring boreal MLRA boundaries. Various mosses and lichens are in the ground cover. Other ground cover includes herbaceous and woody litter.

Dominant plant species

black crowberry (Empetrum nigrum), shrub
dwarf birch (Betula nana), shrub
marsh Labrador tea (Ledum palustre ssp. decumbens), shrub
bog blueberry (Vaccinium uliginosum), shrub
lingonberry (Vaccinium vitis-idaea), shrub
tealeaf willow (Salix pulchra), shrub
beauverd spirea (Spiraea stevenii), shrub
bluejoint (Calamagrostis canadensis), grass

Additional community tables

Supporting information

Inventory data references

Modal points for Community 1.1
08SS07801
08AO24204
08LL05807
09SS02201

References

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

Bisbee, Kari E., Stith T. Gower, John M. Norman, and Erik V. Nordheim. 2001. Environmental controls on ground cover species composition and productivity in a boreal black spruce forest. In Oecologia. Volume 129: 261–270.

Bonan, Gordon B., and Herman H. Shugart. 1989. Environmental factors and ecological processes in boreal forests. Annual Review of Ecology and Systematics. Volume 20, pages 1–28.

Imbeau, Louis, Jean-Pierre L. Savard, and Rejean Gagnon. 1999. Comparing bird assemblages in successional black spruce stands originating from fire and logging. Canadian Journal of Zoology. Volume 77: 1,850–1,860.

Kautz, D.R., P. Taber, and S. Nield, editors. 2004. Land resource regions and major land resource areas of Alaska. U.S. Department of Agriculture, Natural Resources Conservation Service, Palmer, AK. Revised 2012.

Roberge, M.R. 1976. Respiration rates for determining the effects of urea on the soil-surface organic horizon of a black spruce stand. Canadian Journal of Microbiology. Volume 22: 1,328–1,335.

Schoeneberger, P.J., and D.A. Wysocki. 2012. Geomorphic description system. Version 4.2. U.S. Department of Agriculture, Natural Resources Conservation Service, National Soil Survey Center, Lincoln, NE.

Schoeneberger, P.J., D.A. Wysocki, E.C. Benham, and Soil Survey Staff. 2012. Field book for describing and sampling soils. Version 3.0. U.S. Department of Agriculture, Natural Resources Conservation Service, National Soil Survey Center, Lincoln, NE.

Soil Science Division Staff. 2017. Soil survey manual. C. Ditzler, K. Scheffe, and H.C. Monger, editors. U.S. Department of Agriculture Handbook 18. Government Printing Office, Washington, D.C.

U.S. Department of Agriculture, Natural Resources Conservation Service. 2006. Land resource regions and major land resource areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296.

Viereck, L.A., C.T. Dyrness, A.R. Batten, and K.J. Wezlick. 1992. The Alaska vegetation classification. U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station General Technical Report PNW-GTR-286. Portland, OR.

Contributors

Phil Barber
Michael Margo
Sue Tester
Kendra Moseley
Steph Schmit
Steff Shoemaker
Jamin Johanson

Approval

Kirt Walstad, 2/13/2024

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	02/14/2024
Approved by	Kirt Walstad
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:

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Natural ResourcesConservation Service

Ecological site R236XY106AK

Subarctic Dwarf Scrub Dry Loamy Slopes

Last updated: 2/13/2024 Accessed: 04/29/2024

General information

MLRA notes

Ecological site concept

Associated sites

Similar sites

Table 1. Dominant plant species

Ecosystem states

State 1 submodel, plant communities

Natural Resources
Conservation Service

Last updated: 2/13/2024
Accessed: 04/29/2024