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Ecological site R239XY020AK

Arctic Scrub Gravelly Flood Plains

Last updated: 2/18/2025
Accessed: 03/31/2025

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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): 239X–Northern Bering Sea Islands

The Northern Bering Sea Islands (MLRA 239X) occurs in Western Alaska and includes Saint Lawrence (1,792 square miles), Nunivak (1,632 square miles), and Saint Matthew (137 square miles) Islands and several smaller adjacent islands all of which are surrounded by the Bering Sea. This MLRA makes up 3,705 square miles. The terrain primarily consists of nearly level to rolling plains and highlands with mostly gentle slopes. Coastal lowlands dotted with numerous small- and medium-size lakes make up a significant part of St. Lawrence Island. Steep, low-relief volcanic cones, vents, and lava flows are common throughout Nunivak Island and less common on St. Lawrence and St. Matthew Islands. Narrow, discontinuous sea cliffs, sand dunes, and sand sheets are along many stretches of the coast. Elevation ranges from sea level along the coast to 2,207 feet at the summit of Atuk Mountain, on St. Lawrence Island. The area is mostly undeveloped wild land that is sparsely populated. Residents use this remote area primarily for subsistence hunting, fishing, and gathering. Reindeer and/or muskox herding provides meat and other products to residents on Nunivak Island and St. Lawrence Islands. The largest communities on the islands are Diomede, Gambell, Mekoryuk, and Savoonga.

Geology and Soils

Across the islands, most of the landscape is mantled with late Tertiary and Quaternary alluvial, marine, and eolian surficial deposits. While a small portion of the northwest coast of St. Lawrence Island was glaciated (Patton et al. 2011), the vast majority of the MLRA was unglaciated during the Pleistocene Epoch. St. Lawrence Island is the most geologically complex of the islands in this area. The St. Lawrence Island coastal plain is dotted with numerous small- and medium-size lakes with a mosaic primarily composed of surficial deposits and volcanic and sedimentary rock, including coal beds and limestone. The highlands on this island are primarily composed of Cretaceous granitic bedrock except for Atuk Mountain which is composed of young volcanic bedrock from the Quaternary to late Tertiary. Nunivak and St. Matthew Islands are made up almost exclusively of early and late Tertiary and Quaternary volcanic rocks.

These islands are in the zone of discontinuous permafrost. Frozen soils are common across the vast extents of rolling plains and gentle sloping highlands. In these areas, the layer of permafrost is generally thin or moderately thick and occurs primarily in fine textured deposits. Permafrost generally does not occur on flood plains, in coarse textured sediments on the slopes of volcanic cones and other highlands, along the coast, or near lakes and other bodies of water. Common periglacial features include solifluction lobes, frost boils, and palsen (Swanson et al. 1986, USDA 2022).

The majority of soils are acidic, and the dominant soil order is Gelisols. Except for some non-acidic uplands on St. Lawrence Island, the vast majority of soil substrate across the MLRA is acidic (pH less than 5.5) (CAVM Team 2023). The Gelisols are shallow or moderately deep to permafrost (10 to 40 inches) and are typically very poorly to poorly drained. Common Gelisol suborders are Histels, Orthels, and Turbels. The Histels have thick accumulations of surface organic material and primarily occur in very wet coastal plain depressions and low-gradient drainageways. The Orthels and Turbels have comparably thinner surface organic material and primarily occur on the coastal lowlands and other areas with gentle slopes. The MLRA also has small areas of Andisols, Entisols, Inceptisols, and Mollisols. Andisols and Inceptisols primarily occur on volcanic cones and other slopes with coarse textured, acidic soils. Mollisols occur on areas with limestone on St. Lawrence Island (USDA 2022). Entisols primarily occur on flood plains and estuaries. Miscellaneous (non-soil) areas make up about 10 percent of the area and are primarily water, lava flows, rubble composed of volcanic rock, and beach sediments.

Climate

The presence of sea ice in the Bering Sea strongly influences the climate across the islands in this area. Sea ice in the Bering Sea historically forms in early December, increases in thickness until late April, and breaks apart in June (Zuesler 1941). When sea ice is absent, the Bering Sea and North Pacific Ocean moderate diurnal and monthly temperatures resulting in a maritime climate. As sea ice forms around the islands, temperatures decrease significantly with the area shifting to a continental climate.

Vegetation

Tidal flats and estuaries support sedge dominant communities, while drier beach dune communities support American dunegrass and seacoast angelica communities (Swanson et al. 1986). The coastal lowlands and nearly level to rolling plains have a mosaic of sedge and moss dominant wetlands and various tundra. The tundra often has dwarf shrubs like crowberry; tussock forming and non-tussock forming sedges; and a variety of forbs, lichen, and mosses. Very wet drainages and the shores of lakes support wet sedge meadows. Drier soils on flood plains commonly support low to tall willow scrub with dense grasses and forbs in the understory. Shallow soils with coarse textured rocks common on volcanic cones, mountain slopes, and ridges commonly support alpine dwarf scrub dominated by ericaceous shrubs, Dryas, and dwarf willows. These communities commonly have a considerable amount of lichen and bare ground. Bedrock exposures and barrens with lichens and scattered shrubs and herbs in pockets of fine earth dominate the highest elevations, ridges, and other windblown sites.

Introduced ungulates

Introduced herds of reindeer and muskox provide a rich history of land use across the Northern Bering Sea Islands MLRA. Of the many islands in this MLRA, Nunivak was the only island historically grazed by ungulates. Inhabited by caribou until the late 1800’s, the caribou on Nunivak Island were extirpated with the introduction of rifles (Griffin 2001).
Reindeer were introduced to St. Lawrence Island as early as 1901 (Jackson 1902), Nunivak Island in 1920, and St. Matthew Island in 1944 (Swanson and Barker 1991). Muskox were introduced to Nunivak Island in 1930 (ADFG 2024). Nunivak Island currently has managed herds of reindeer and muskox, St. Lawrence Island currently has managed herds of reindeer, and St. Matthew Island currently has no herds of reindeer. Some small islands in this MLRA are believed to have no history of natural or introduced ungulate herds (e.g. Pinnace Islands, Hall Island, and Punuk Islands).

LRU notes

There are two distinct bioclimates in this MLRA resulting in slight differences in vegetation. St. Lawrence Island is more than 200 miles North of Nunivak and St. Matthew Islands. As a result, St. Lawrence Island is significantly colder. Mean annual air temperatures on Nunivak and St. Matthew Islands typically range from 30 to 34 degrees Fahrenheit and are between 24 to 28 degrees Fahrenheit on St. Lawrence Islands (PRISM 2018). More southerly islands in this area fall into the Circumpolar Arctic Vegetation Mapping (CAVM) subzone E and more northerly islands fall into CAVM subzone D (CAVM 2022). Moist and dry tundra common to the near level to rolling plains across the islands are thought to support plant communities with similar species but have different plant community structures. Subzone E supports low shrub communities and subzone D erect dwarf shrub communities (CAVM 2022). At this time, these differences in community structure are recognized but unique ecological sites for each CAVM bioclimate subzone were not developed.

This area supports two life zones defined by the physiological limits of plant communities along an elevational gradient: arctic and alpine. In this MLRA, the arctic life zone occurs below 500 feet elevation on average (Swanson et al. 1986) and is the elevational band where lowland vegetation dominates. For this MLRA, certain vascular plant species are common in the lowlands and much less common in the alpine (i.e. Salix pulchra, Salix fuscescens, Betula nana, Ledum palustre ssp. decumbens, and Calamagrostis canadensis). Above the arctic band of elevation, alpine vegetation dominates. For this MLRA, certain vascular plant and lichen species are common in the alpine and much less common in the lowlands (i.e. Dryas octopetala ssp. octopetala, Diapensia lapponica var. obovata, Anthoxanthum monticola ssp. alpinum, Oxytropis nigrescens, Alectoria ochroleuca, and Flavocetraria nivalis). The lowlands also have much higher potential for lichen biomass yields compared to the alpine (Swanson et al. 1986). The transition between arctic and alpine vegetation can occur within a range of elevations, and is highly dependent on latitude, slope, aspect, and shading from adjacent mountains.

Classification relationships

Landfire BPS – 7217150 - Alaska Arctic Floodplain (Landfire 2009)
Open/Closed Tall Scrub Willow (Viereck et. al 1992)
Tall Shrub (Floodplain) (Swanson et al. 1986)
Grass (Riparian) (Swanson et al. 1986)

Ecological site concept

This arctic ecological site occurs on the flood plains of stream and rivers with gravelly soils that lack permafrost. Flooding occurs frequently (greater than 50 times in 100 years) for brief durations of time (between 2 and 7 days). Soils are somewhat poorly drained. The typical soil profile has no organic matter and is a very thick layer of sandy and gravelly alluvium.

The presence of introduced ungulate herds on Nunivak, St Lawrence, and St. Matthews Islands, in some places for over a century, plays an integral role in shaping vegetation across this MLRA. Islands in this MLRA without a history of introduced reindeer and muskox herds are associated with reference state vegetation, while islands with introduced herds are associated with grazing state vegetation.

This ecological site has multiple plant communities related to flooding and continuous grazing. Areas proximal to the active channel flood more frequently for longer duration of time compared to more distal areas. Proximal areas have gravelly surfaces and are sparsely vegetated by low growing willow, grasses, and forbs. Distal areas support two communities being a bluejoint meadow and an open to closed tall willow scrub community. These two communities often coexist as a mosaic. At times, continuous grazing by muskox results in the removal of much of the of willow biomass in these communities.

Associated sites

R239XY034AK	Arctic Scrub Loamy Frozen Drainageways Occurs on low-order streams and drainageways with open and closed low willow scrub (Swanson et al. 1986; Viereck et al. 1992). These are the headwaters of the larger streams and flood plains associated with site 20.
R239XY053AK	Arctic Sedge Loamy Tidal Marsh Occurs in tidal marshes such as tidal flats and estuaries with sedge dominant communities. Ecological site 020 and 053 meet near the coastline.

R239XY034AK

Arctic Scrub Loamy Frozen Drainageways

Occurs on low-order streams and drainageways with open and closed low willow scrub (Swanson et al. 1986; Viereck et al. 1992). These are the headwaters of the larger streams and flood plains associated with site 20.

R239XY053AK

Arctic Sedge Loamy Tidal Marsh

Occurs in tidal marshes such as tidal flats and estuaries with sedge dominant communities. Ecological site 020 and 053 meet near the coastline.

Similar sites

R239XY034AK	Arctic Scrub Loamy Frozen Drainageways Occurs on low-order streams and drainageways with wet and frozen soils. Ecological site 034 has less productive vegetation and more facultative wet and obligate wetland plants.

R239XY034AK

Arctic Scrub Loamy Frozen Drainageways

Occurs on low-order streams and drainageways with wet and frozen soils. Ecological site 034 has less productive vegetation and more facultative wet and obligate wetland plants.

Table 1. Dominant plant species

Tree	Not specified
Shrub	(1) Salix alaxensis (2) Salix pulchra
Herbaceous	(1) Calamagrostis canadensis (2) Equisetum arvense

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Physiographic features

This ecological site occurs on flood plains of rivers and streams. Elevation typically occurs between 20 and 500 feet. These flood plains have negligible slopes and occur on all aspects. Flooding occurs frequently for brief durations of time. During high-water and flooding, the water table is commonly at the soil surface. After the high-water recedes, the water table drops to moderately deep or greater depths.

Table 2. Representative physiographic features

Landforms	(1) Plains > Flood plain
Runoff class	Negligible to very low
Flooding duration	Brief (2 to 7 days)
Flooding frequency	Frequent
Ponding frequency	None
Elevation	20 – 500 ft
Slope	1%
Water table depth	16 – 24 in
Aspect	W, NW, N, NE, E, SE, S, SW

Table 3. Representative physiographic features (actual ranges)

Runoff class	Not specified
Flooding duration	Not specified
Flooding frequency	Not specified
Ponding frequency	Not specified
Elevation	20 – 1,650 ft
Slope	Not specified
Water table depth	Not specified

Climatic features

Sea ice strongly influences the climate of the islands in MLRA 239X. For the Northern Bering Sea Islands, sea ice starts forming in December and often persists through early June. In the absence of sea ice, the Bering Sea and North Pacific Ocean moderate diurnal and monthly temperatures resulting in a maritime climate. Summer temperatures (June through August) are relatively stable with mean maximum monthly temperatures ranging between 50 to 55 degrees Fahrenheit. As sea ice forms around the islands, temperatures decrease significantly with the area shifting to a continental climate. The coldest months (January through March) have mean monthly minimum temperatures ranging from 4 to 6 degrees Fahrenheit. The extent, thickness, and duration of the Bering Sea ice appears to be in flux resulting in southerly storms that can bring significantly warmer winter monthly temperatures (Stabeno et al. 2018, Gramling 2019).

The Northern Bering Sea Islands have summers that are short and cool and winters that are long and cold. Strong winds are common throughout the year. Mean annual air temperatures typically range from 26 to 32 degrees Fahrenheit with Saint Lawrence Island (mean annual air temperatures between 24 to 28 degrees Fahrenheit) being significantly colder compared to Nunivak and Saint Michael Islands (mean annual air temperatures between 30 to 34 degrees Fahrenheit) (PRISM 2018). The warmest months are June, July, and August. During these summer months, the typical freeze free period for the area ranges from 94 to 111 days. The coldest months are January, February, and March.

This area is semi-arid with mean annual precipitation typically ranging between 14 and 17 inches. The warmest months have overcast skies with frequent fog and precipitation while the coldest months have clear skies. The two wettest months are August and September where the islands typically receive a quarter of the annual precipitation. The rest of the months receive similar amounts of precipitation. Saint Michael Island receives greater mean annual precipitation (between 17 and 21 inches) compared to Nunivak and Saint Lawrence Islands (between 13 to 17 inches) (PRISM 2018). The average annual snowfall ranges from about 50 to 80 inches (USDA 2022) with the highest snowfall occurring during the months spanning November through March (USDA 1986).

Table 4. Representative climatic features

Frost-free period (characteristic range)	51-75 days
Freeze-free period (characteristic range)	94-111 days
Precipitation total (characteristic range)	14-17 in
Frost-free period (actual range)	50-85 days
Freeze-free period (actual range)	93-117 days
Precipitation total (actual range)	13-18 in
Frost-free period (average)	64 days
Freeze-free period (average)	103 days
Precipitation total (average)	15 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) NOME MUNI AP [USW00026617], Nome, AK
(2) WALES [USW00026618], Wales, AK
(3) BETHEL AP [USW00026615], Bethel, AK

Influencing water features

This site is classified as a Riverine wetland under the Hydrogeomorphic (HGM) classification system (Smith et al. 1995; USDA-NRCS 2008). In the associated flood plains, overbank flow from the channel and subsurface hydraulic connections between the stream and adjacent wetlands are the main sources of water (Smith et al. 1995).

Depth to the water table may decrease following summer storm events or spring snowmelt and increase during extended dry periods.

Wetland description

n/a

Soil features

Soils formed in sandy and gravelly alluvium and do not have permafrost. Rock fragments on the soil surface are common and often range between one and nine percent cover. These are mineral soils without an organic cap. The surface mineral horizon is a sandy loam that typically has minimal rock fragments. This surface mineral horizon is thin and commonly ranges in thickness between one and two inches. Below this horizon is a thick layer of gravelly sands with rock fragments ranging between 45 and 65 percent, by volume, of the soil profile. Soils are very deep, with restrictions occurring at a very shallow depth a result of the abrupt textural change in the soil profile. The pH of the soil typically ranges from moderately acidic to slightly alkaline. The soils are wet during high water and flood events; and are considered somewhat poorly drained.

Table 5. Representative soil features

Parent material	(1) Alluvium
Surface texture	(1) Sandy loam
Family particle size	(1) Sandy-skeletal
Drainage class	Somewhat poorly drained
Permeability class	Rapid
Depth to restrictive layer	1 – 2 in
Soil depth	60 in
Surface fragment cover <=3"	1 – 7%
Surface fragment cover >3"	2%
Available water capacity (0-40in)	0.5 – 0.6 in
Calcium carbonate equivalent (10-40in)	Not specified
Clay content (0-20in)	2 – 5%
Electrical conductivity (10-40in)	Not specified
Sodium adsorption ratio (10-40in)	Not specified
Soil reaction (1:1 water) (10-40in)	5.8 – 7.6
Subsurface fragment volume <=3" (0-60in)	35 – 45%
Subsurface fragment volume >3" (0-60in)	10 – 20%

Table 6. Representative soil features (actual values)

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

Ecological dynamics

The Northern Bering Sea Islands MLRA (MLRA 239X) occurs in the arctic where the harsh climate limits the composition and structure of plant communities. This area has cool and short summers and long and cold winters. Limited warmth during the short summer months, inhibits trees from occurring, and the expansive tundra is composed of a mosaic of low growing shrubs, sedges, moss, and lichen. The cold temperatures limit the vertical and horizontal structure of shrubs and other functional groups of the tundra (CAVM 2022). For instance, shrubs do not typically exceed 80 cm in height across these islands (Swanson et al. 1986; CAVM 2022). The exception is micro-climates where snow can accumulate, which protects vegetation from harsh winds and insulates soils. These micro-climates allow for shrubs to grow much taller and occur on landforms such as flood plains.

Ungulate History and Use

In this MLRA, the lack of predators paired with quality forage can lead to dramatic population growth of reindeer which in turn can lead to significant die-offs. Eighty-one reindeer were introduced to Nunivak Island in 1920. Due to a lack of predators and an abundance of high-quality forage, the reindeer population climbed to peaks of greater than 30 thousand in 1944 and 23 thousand in 1965 (Swanson and Barker 1991). After each peak in population, the reindeer herds experienced dramatic population die offs that resulted in less than 5 thousand animals (Swanson and Barker 1991). These die offs are largely attributed to lichen range depletion. Lichen forage makes up 47 percent of the March diet for reindeer herds on Nunivak Island (Swanson et al. 1986) so the depletion of lichen range can directly lead to stress and mortality of reindeer populations.

The presence of introduced ungulate herds on Nunivak, St Lawrence, and St. Matthews Islands, in some places for over a century, plays an integral role in shaping vegetation across this MLRA. Some small islands in this MLRA are believed to have no history of natural or introduced ungulate herds (e.g. Pinnace Islands, Hall Island, and Punuk Islands). On islands with introduced herds, grazing by reindeer and/or muskox has impacted the potential natural vegetation. For instance, continuous grazing of slow growing fruticose lichen can lead to changes in lichen species composition (Swanson and Barker 1991) and can lead to increases in shrub and bryophyte cover (Kautz et al. 1992). Because of the mixed history in grazing in this MLRA, the STM for this ecological site has two states. Islands in this MLRA without a history of ungulate herds are associated with reference state vegetation, while islands with introduced ungulate herds are associated with grazing state vegetation.

While often limited in area, ungulate browse can have profound impacts to the structure and composition of vegetation associated with this ecological site. Stands of open and closed tall willow are common on associated flood plains. On isolated sections of certain flood plain, muskox herds were shown to eat the majority of willow biomass resulting in a unique plant community. Tall stands of willow were reduced to herbaceous mats with scattered prostrate willow (plant community 2.4). If continuous grazing of these stands were suppressed, the quick growing willow community should recover. While this flood plain vegetation provides high quality forage for reindeer during the spring and summer months (Swanson et al. 1986), reindeer use is limited in scope and does not result in alternate communities.

Flooding

Field work indicates that differences in flood regime and landform position result in three different plant communities. Bare gravels are common directly adjacent to the active flood plain channel. Colonizing these bare gravels is a pioneering plant community largely composed of sparse shrubs, grasses, and forbs (community 2.3). This plant community has the most frequent and longest duration flood events for this ecological site. Occurring on comparatively distal positions with less frequent and shorter duration flooding are a grass dominant community (community 2.2) and tall scrub willow community (community 2.1). These two plant communities commonly coexist as a mosaic. Community 2.2 occurs in areas with slower flowing flood water that tend to accumulate fine sediments (e.g. areas adjacent to depressions or in braided channels). Community 2.1 occurs in areas with faster flowing flood water that tends to accumulate coarser sediments (e.g. point bars and natural levees).

State and transition model

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Click on state and transition labels to scroll to the respective text

Ecosystem states

1. Reference State

2. Grazing State

T1	-	Human introduction of reindeer and/or muskox to islands.
R1	-	Long periods of time after extirpation of human introduced ungulates.

State 1 submodel, plant communities

1.1. tealeaf willow - feltleaf willow / bluejoint

State 2 submodel, plant communities

2.1. feltleaf willow - tealeaf willow / bluejoint / field horsetail - Canadian burnet

2.2. bluejoint

2.3. feltleaf willow / bluejoint / field horsetail - common yarrow

2.4. feltleaf willow - tealeaf willow / bluejoint

2.1a	-	graminoid colonization and dominance paired with significant willow mortality
2.1b	-	more frequent and longer duration flooding
2.1c	-	continuous grazing by muskox
2.2a	-	willow colonization and dominance
2.3a	-	less frequent and shorter duration flooding
2.4a	-	time without continuous grazing by muskox

State 1
Reference State

The historic and current use of introduced ungulates in this MLRA may have altered the potential natural vegetation on these islands. Islands in this MLRA without a history of introduced grazing have reference state vegetation, while islands with introduced herds of reindeer and/or muskox (Nunivak, St. Lawrence, and St. Matthews Islands) have grazing state vegetation. Currently no data has been collected in areas of this MLRA in reference condition. Future targeted data collection efforts can address whether range in excellent condition within the grazing state is similar to reference state vegetation and these results could dramatically alter this provisional state and transition model.

Dominant plant species

feltleaf willow (Salix alaxensis), shrub
tealeaf willow (Salix pulchra), shrub
bluejoint (Calamagrostis canadensis), grass
Canadian burnet (Sanguisorba canadensis), other herbaceous
tall Jacob's-ladder (Polemonium acutiflorum), other herbaceous

Community 1.1
tealeaf willow - feltleaf willow / bluejoint

Community 1.1 is the potential natural vegetation for this state. It is characterized as open to closed tall scrub (Viereck et al. 1992) with tealeaf willow and feltleaf willow the dominant shrubs. Common and abundant understory species include bluejoint.

Dominant plant species

feltleaf willow (Salix alaxensis), shrub
tealeaf willow (Salix pulchra), shrub
bluejoint (Calamagrostis canadensis), grass

State 2
Grazing State

Figure 7. A flood plain with tall scrub willow vegetation on Nunivak Island.

Four plant communities occur within the grazing state and the vegetation differs in large part due to flood regime and grazing. The data for this state is based on a mixture of recent field work conducted on Nunivak Island (2022-2023) and historical range surveys conducted on Nunivak Island (Swanson et al. 1986, Kautz et al. 1992). Future work will be required to determine if the vegetation on Nunivak Island represent the vegetation across the grazed islands of this MLRA.

Dominant plant species

feltleaf willow (Salix alaxensis), shrub
tealeaf willow (Salix pulchra), shrub
bluejoint (Calamagrostis canadensis), grass
field horsetail (Equisetum arvense), other herbaceous

Community 2.1
feltleaf willow - tealeaf willow / bluejoint / field horsetail - Canadian burnet

Figure 8. Tall scrub willow vegetation is common along the floodplain of this area.

Figure 9. A floodplain on Nunivak Island.

Plant community 2.1 is characterized as open to closed tall scrub (Viereck et al. 1992) with the dominant overstory vegetation being feltleaf willow. The scrub layer does not typically exceed 5 feet in height. Other common species include tealeaf willow, bluejoint, field horsetail, and Canadian burnet. The soil surface is primarily covered with herbaceous litter. The vegetative strata that characterize this community are medium shrubs (between 3 and 10 feet), medium graminoids (between 4 and 24 inches) and medium forbs (between 4 and 24 inches).

Forest understory. Live lichen and moss annual production cannot be measured accurately due to a lack of information on growth rates and/or slow annual growth rates. Lichen and moss biomass data below refers to total biomass, while vascular plants biomass refers to annual production.

Dominant plant species

feltleaf willow (Salix alaxensis), shrub
tealeaf willow (Salix pulchra), shrub
bluejoint (Calamagrostis canadensis), grass
field horsetail (Equisetum arvense), other herbaceous
Canadian burnet (Sanguisorba canadensis), other herbaceous

Figure 10. Annual production by plant type (representative values) or group (midpoint values)

Table 7. Ground cover

Tree foliar cover	0%
Shrub/vine/liana foliar cover	75-95%
Grass/grasslike foliar cover	10-25%
Forb foliar cover	25-50%
Non-vascular plants	0%
Biological crusts	0%
Litter	25-50%
Surface fragments >0.25" and <=3"	0%
Surface fragments >3"	0%
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	–	–	–	–
>1 <= 2	–	–	5-15%	10-25%
>2 <= 4.5	–	70-90%	5-10%	10-25%
>4.5 <= 13	–	5-25%	–	–
>13 <= 40	–	–	–	–
>40 <= 80	–	–	–	–
>80 <= 120	–	–	–	–
>120	–	–	–	–

Community 2.2
bluejoint

Figure 11. A bluejoint dominant community on a flood plain of Nunivak Island.

Figure 12. The foreground is a tall scrub willow community and the background a grass dominant community. These communities are often a mosaic on the flood plains of this MLRA.

Community 2.2 is characterized as bluejoint meadow (Viereck et al. 1992) with the dominant plant being bluejoint. Other common species include common woodrush, field horsetail, purple marshlocks, Canadian burnet, and ledge stonecrop. The soil surface is primarily covered with herbaceous litter. The vegetative strata that characterize this community are medium graminoids (between 4 and 24 inches).

Dominant plant species

bluejoint (Calamagrostis canadensis), grass
common woodrush (Luzula multiflora), grass
field horsetail (Equisetum arvense), other herbaceous
purple marshlocks (Comarum palustre), other herbaceous
Canadian burnet (Sanguisorba canadensis), other herbaceous
ledge stonecrop (Rhodiola integrifolia), other herbaceous

Figure 13. Annual production by plant type (representative values) or group (midpoint values)

Table 9. Ground cover

Tree foliar cover	0%
Shrub/vine/liana foliar cover	0-5%
Grass/grasslike foliar cover	50-75%
Forb foliar cover	5-15%
Non-vascular plants	0%
Biological crusts	0%
Litter	75-95%
Surface fragments >0.25" and <=3"	0%
Surface fragments >3"	0%
Bedrock	0%
Water	0-5%
Bare ground	0%

Table 10. Canopy structure (% cover)

Height Above Ground (ft)	Tree	Shrub/Vine	Grass/ Grasslike	Forb
<0.5	–	–	–	–
>0.5 <= 1	–	–	–	–
>1 <= 2	–	–	–	5-15%
>2 <= 4.5	–	0-5%	50-75%	1-5%
>4.5 <= 13	–	0-5%	–	–
>13 <= 40	–	–	–	–
>40 <= 80	–	–	–	–
>80 <= 120	–	–	–	–
>120	–	–	–	–

Community 2.3
feltleaf willow / bluejoint / field horsetail - common yarrow

Community 2.3 is a pioneering plant community on flood plains, sparsely vegetated, and is commonly characterized as open low scrub (Viereck et al. 1992). Within the grazing state for this site, this community has the most severe flood regime. This community is often highly diverse. Commonly observed species include feltleaf willow, bluejoint, field horsetail, common yarrow, yellow marsh marigold, dwarf fireweed, Tilesius' wormwood, and nootka lupine.

Dominant plant species

feltleaf willow (Salix alaxensis), shrub
bluejoint (Calamagrostis canadensis), grass
field horsetail (Equisetum arvense), other herbaceous
common yarrow (Achillea millefolium), other herbaceous
dwarf fireweed (Chamerion latifolium), other herbaceous
Tilesius' wormwood (Artemisia tilesii), other herbaceous
Nootka lupine (Lupinus nootkatensis), other herbaceous
yellow marsh marigold (Caltha palustris), other herbaceous

Community 2.4
feltleaf willow - tealeaf willow / bluejoint

Figure 14. Continuous grazing of flood plain willow community by muskox on Nunivak Island.

Willow cover, height, and biomass are reduced due to continuous grazing by muskox. The community has prostrate willow throughout and is characterized as open low scrub (Viereck et al. 1992). Common species include feltleaf willow, tealeaf willow, bluejoint, and arctic sweet coltsfoot.