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Ecological site F237XY216AK

Boreal Woodland Loamy Flood Plains

Last updated: 7/23/2020
Accessed: 04/22/2026

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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): 237X–Ahklun Mountains

The Ahklun Mountains Major Land Resource Area (MLRA 237) is in western Alaska (fig. 2). This MLRA covers approximately 14,555 square miles, and it includes the mountains, hills, and valleys of the Kilbuck Mountains in the north and the Ahklun Mountains in the south. Except for the Kilbuck Mountains and the highest ridges of the Ahklun Mountains, the MLRA was extensively glaciated during the Pleistocene (Kautz et al., 2004). Today, a few small glaciers persist in mountainous cirques (Gallant et al., 1995). The present-day landscape and landforms reflect this glacial history; glacial moraines and glacial drift cover much of the area (USDA-NRCS, 2006). The landscape of the MLRA is primarily defined by low, steep, rugged mountains cut by narrow-to-broad valleys. Flood plains and terraces of varying sizes are common at the lower elevations in the valley bottoms. Glacially carved valleys host many lakes. Togiak Lake is one of the largest lakes in the region. It is 13 miles long and about 9,500 acres in size. Major rivers include the Goodnews, Togiak, Kanektok, Osviak, Eek, and Arolik Rivers. Where the Goodnews and Togiak Rivers reach the coast, the nearly level to rolling deltas support numerous small lakes.

This MLRA has two distinct climatic zones: subarctic continental and maritime continental (fig. 3). The high-elevation areas are in the subarctic continental zone. The mean annual precipitation is more than 75 inches, and the mean annual air temperature is below about 27 degrees F (-3 degrees C) in extreme locations. The warmer, drier areas at the lower elevations are in the maritime continental zone. The mean annual precipitation is 20 to 50 inches, and the mean annual air temperature is about 30 to 32 degrees F (-0.2 to 1.2 degrees C) (PRISM). This climatic zone is influenced by both maritime and continental factors. The temperatures in summer are moderated by the open waters of the Bering Sea, and the temperatures in winter are more continental due to the presence of ice in the sea (Western Regional Climate Center, 2017). The seasonal ice reaches its southernmost extent off the coast of Alaska in Bristol Bay (Alaska Climate Research Center, 2017). The western coast of Alaska is also influenced by high winds from strong storms and airmasses in the Interior Region of Alaska (Hartmann, 2002).

The Ahklun Mountains MLRA is principally undeveloped wilderness. Federally managed lands include the Togiak and Alaska Maritime National Wildlife Refuges. The MLRA is sparsely populated, but it has several communities, including Togiak, Manokotak, Twin Hills, and Goodnews Bay. Togiak is the largest village. It has a population of approximately 855, most of which are Yup’ik Alaska Natives (U.S. Census Bureau, 2016). Major land uses include subsistence activities (fishing, hunting, and gathering) and wildlife recreation (USDA-NRCS, 2006; Kautz et al., 2004).

Ecological site concept

Ecological site F237XY216AK is on mid to high flood plains of the Izavieknik River valley. The climate, landform, and location create a unique ecological site along this river. The river valley is in the eastern part of the Ahklun Mountains area, and it is prone to the pressure of tree propagule from neighboring MLRA 236. Poplar trees, more common in areas of milder climates to the east, are now a keystone plant species in this river valley. The reference state supports one documented community phase.

The reference plant community is an open broadleaf forest (Viereck et al., 1992) of balsam poplar (Populus balsamifera) and an understory of shrubs, graminoids, and forbs. Understory plants include willow (Salix spp.), squashberry (Viburnum edule), bluejoint (Calamagrostis canadensis), field horsetail (Equisetum arvense), and a mix of less prevalent graminoids and forbs.

Associated sites

R237XY210AK	Western Alaska Maritime Scrubland Gravelly Flood Plains Ecological site F237XY216AK is differentiated from the associated ecological sites based on position on the landscape, landform, disturbance regime, and vegetative communities. Ecotonal plant communities that have characteristics of more than one ecological site are in areas where these sites abut.
R237XY211AK	Western Alaska Maritime Scrubland Loamy Flood Plains Ecological site F237XY216AK is differentiated from the associated ecological sites based on position on the landscape, landform, disturbance regime, and vegetative communities. Ecotonal plant communities that have characteristics of more than one ecological site are in areas where these sites abut.
R237XY222AK	Western Alaska Maritime Scrubland Loamy Hummocks Ecological site F237XY216AK is differentiated from the associated ecological sites based on position on the landscape, landform, disturbance regime, and vegetative communities. Ecotonal plant communities that have characteristics of more than one ecological site are in areas where these sites abut.

R237XY210AK

Western Alaska Maritime Scrubland Gravelly Flood Plains

Ecological site F237XY216AK is differentiated from the associated ecological sites based on position on the landscape, landform, disturbance regime, and vegetative communities. Ecotonal plant communities that have characteristics of more than one ecological site are in areas where these sites abut.

R237XY211AK

Western Alaska Maritime Scrubland Loamy Flood Plains

R237XY222AK

Western Alaska Maritime Scrubland Loamy Hummocks

Similar sites

F237XY239AK	Boreal Forest Loamy Slopes Four ecological sites are on major flood plains in the Ahklun Mountains area. Three of these sites are throughout the area. Site F237XY216AK, however, is restricted to the valley carved by the Izavieknik River (fig. 1). Location, flooding characteristics, and soil features create a unique vegetative community in this ecological site. Site F237XY239AK is a balsam poplar community, but it is associated with discharge slopes, such as fans or seeps, that behave differently than flood plains. The understory vegetation of site F237XY239AK is different from that of site F237XY216AK.

F237XY239AK

Boreal Forest Loamy Slopes

Four ecological sites are on major flood plains in the Ahklun Mountains area. Three of these sites are throughout the area. Site F237XY216AK, however, is restricted to the valley carved by the Izavieknik River (fig. 1). Location, flooding characteristics, and soil features create a unique vegetative community in this ecological site. Site F237XY239AK is a balsam poplar community, but it is associated with discharge slopes, such as fans or seeps, that behave differently than flood plains. The understory vegetation of site F237XY239AK is different from that of site F237XY216AK.

Figure 1. Mid to high flood plains along the Izavieknik River support open balsam poplar forests.

Table 2. Dominant plant species

Tree	(1) Populus balsamifera
Shrub	(1) Viburnum edule
Herbaceous	(1) Equisetum arvense (2) Athyrium filix-femina

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Physiographic features

Site characteristics specifically relate to the reference plant community phase. Each ecological site has a specific set of site characteristics and disturbance dynamics that results in a unique plant community composition, structure, and function. Site characteristics (climate, geology, topography, and soil characteristics) are dynamic across a landscape. Subtle changes in site characteristics can result in a different plant community phase or ecological site. Definitions of site characteristics are provided in the United States Department of Agriculture Handbook 296 (USDA-NRCS, 2006), Geomorphic Description System (Schoeneberger and Wysocki, 2012), Field Book for Describing and Sampling Soils (Schoeneberger et al., 2012), and Soil Survey Manual (Soil Science Division Staff, 2017).

Figure 1. The Ahklun Mountains area (MLRA 237) is in western Alaska.

Figure 2. High-elevation and low-elevation map units in the area, which illustrate the primary climatic influence.

Table 3. Representative physiographic features

Slope shape across	(1) Convex (2) Linear
Slope shape up-down	(1) Linear
Geomorphic position, flats	(1) Talf
Landforms	(1) River valley > Flood plain
Flooding frequency	Rare
Ponding frequency	None
Elevation	210 – 560 ft
Slope	0 – 3 %
Aspect	W, NW, N, NE, E, SE, S, SW

Climatic features

Climate of land resource region (LLR): Maritime continental (Western Regional Climate Center, 2017); short, warm summers and long, cold winters (USDA-NRCS, 2006)

Climate of major land resource area (MLRA): Maritime continental in the lowlands and subarctic continental at higher elevations. The mean annual precipitation is 20 to 30 inches in the lowlands, and it increases to more than 45 inches at the higher elevations. The mean annual air temperature along the coast is about 34 degrees F (1 degree C) (PRISM). Strong winds are common throughout the year.

Table 4 Representative climatic features

Frost-free period (characteristic range)	80-140 days
Freeze-free period (characteristic range)
Precipitation total (characteristic range)

Soil features

This ecological site is correlated to Typic Cryofluvents, rarely flooded. These soils are well drained. The saturated hydraulic conductivity of the soils is moderately low or moderately high to a depth of 20 inches and very high below that depth.

Table 5. Representative soil features

Drainage class	Well drained

Ecological dynamics

Overview

Site F237XY216AK is on mid and high flood plains in the Izavieknik River valley. The ideal sandy or gravelly soils preferred by poplar commonly are on flood plains and in river valleys (Viereck and Little, 2007). The Izavieknik River is near the eastern edge of MLRA 237, where it abuts MLRA 236 (Bristol Bay—Northern Alaska Peninsula Lowlands). This area was carved by glaciers during the Pleistocene, creating mountain valleys along an east/west trajectory. The valleys create the winding, interlocking border between the MLRAs (figs. 2 and 3). It is believed that these valley corridors allowed for the western movement of balsam poplar to MLRA 237 via windblown seed.

F237XY216AK supports a forest community along the Izavieknik River. It currently is unknown if other flood plains in this MLRA support the ideal climate, landform, and soils to support this ecological site. If the ideal conditions are elsewhere, increased propagule pressure generated by this ecological site likely will be a major factor in the spread of balsam poplar to new areas.

Disturbance Dynamics

Disturbances resulting in community phases or state transitions were not observed. The limited data collected for this ecological site did not include any from areas that had undergone a recent disturbance. Further data collection is needed to determine the presence of a post-disturbance community sere.

Flooding

Flooding is the primary disturbance on this ecological site. Flooding can create barren, moist areas ideal for colonization. Floods also bury organic layers, add nutrients to the soils, deposit seed banks, and decrease competition for light and space (Rood et al., 2007; Yarie et al., 1998). Typically, the intensity and frequency of flooding affects the distribution and abundance of vegetation in Alaska riverine systems (Wohl, 2007). The average frequency of flooding on this ecological site is rare (1 to 5 times in 100 years). No evidence indicates that this disturbance creates an early community phase on these flood plains.

Other Observations

Terraces that intersect these flood plains typically support a dense willow community. An ecotonal community of dense willow and medium and regenerating balsam poplar is in areas where these landforms abut.

Browsing by moose on willow has been documented in the reference plant community. Moose also likely browse the early sere, although it was not observed in situ. Browsing in the reference plant community typically is slight. No early browse sere is required for this ecological site.

No alternative states are associated with this ecological site.

State and transition model

Custom diagram

Standard diagram

Figure 3. State-and-transition model.

More interactive model formats are also available. View Interactive Models

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. Balsam poplar/squashberry/field horsetail-common ladyfern

State 1
Reference State

The reference state supports one community phase that is distinguished by developed structure and dominance of the vegetation and the ecological function and stability of the community (fig. 4). The reference community phase consists of an overstory of deciduous trees and an understory of shrubs, forbs, and graminoids.

This report provides baseline data for vegetation inventory. Future data collection is needed to provide further information about the existing plant community and the potential for disturbances to create early community phases. 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
Balsam poplar/squashberry/field horsetail-common ladyfern

Figure 4. Typical area of plant community 1.1.

Figure 5. Canopy cover and frequency of species in community 1.1.

The reference plant community is characterized as an open broadleaf forest (Viereck et al., 1992) that has an understory of shrubs, forbs, and graminoids (fig. 5). Medium forbs (4 to 24 inches in height), tall trees (more than 40 feet), tall forbs (more than 24 inches), and tall shrubs (more than 10 feet) are the main vegetative strata. The canopy is comprised of balsam poplar (fig. 6). Understory species commonly include squashberry, one or more species of willow, field horsetail, common ladyfern (Athyrium filix-femina), and bluejoint. The ground cover typically includes herbaceous and woody litter and ground mosses. Some areas are bare soil.

Additional community tables

Table 6. Community 1.1 plant community composition

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

Supporting information

Other references

Alaska Climate Research Center. 2017. Climatological data–Bristol Bay. http://oldclimate.gi.alaska.edu. Accessed September 19, 2017.

Gallant, A.l., E.F. Binnian, J.M. Omernik, and M.B. Shasby. 1995. Ecoregions of Alaska. U.S. Geological Survey Professional Paper 1567. Government Printing Office, Washington, D.C.

Hartmann, B. 2002. Climate regions of Alaska. The Alaska Climate Research Center. http://oldclimate.gi.alaska.edu/ClimTrends/30year/regions1.html. Modified August 28, 2002. Accessed September 19, 2017.

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.

PRISM Climate Group. 2014. PRISM climate data. Oregon State University. http://prism.oregonstate.edu. Accessed March 27, 2018.

Rood, S.B., L.A. Goater, J.M. Mahoney, C.M. Pearce, and D.G. Smith. 2007. Floods, fire, and ice: Disturbance ecology of riparian cottonwoods. Canadian Journal of Botany 85(11):1,019-1,032.

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. Ditzler, C., K. Scheffe, and H.C Monger, editors. U.S. Department of Agriculture Handbook 18. Government Printing Office, Washington, D.C.

U.S. Census Bureau. 2016. Vintage 2016 population estimates: Population estimates. https://www.census.gov. Accessed August 14, 2017.

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. https://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/home/?cid=nrcs142p2_053624. Accessed March 28, 2019.

Viereck, L.A., and E.L. Little, Jr. 2007. Alaska trees and shrubs. University of Alaska Press, Fairbanks, AK.

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.

Western Regional Climate Center. 2017. Climate of Alaska. http://wrcc.dri.edu. Accessed September 19, 2017.

Wohl, E.E. 2007. Review of effects of large floods in resistant-boundary channels. In Gravel-Bed Rivers VI: From Process Understanding to River Restoration, Volume 11. H. Habersack, H. Piégay, and M. Rinaldi, editors. Elsevier Science, Amsterdam. Pages 181-211.

Yarie, J., L. Viereck, K. Van Cleve, and P. Adams. 1998. Flooding and ecosystem dynamics along the Tanana River. BioScience 48(9):690-695.

Contributors

Sue Tester
Kendra Moseley
Michael Margo
Stephanie Schmit
Charlotte Crowder

Approval

Michael Margo, 7/23/2020

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	04/22/2026
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:

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