Natural Resources
Conservation Service
Ecological site F236XY201AK
Boreal Open Forest Wet Loamy Warm Mountain Slopes
Last updated: 2/13/2024
Accessed: 08/30/2026
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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): 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).Classification relationships
Alaska Vegetation Classification:
Closed needleleaf forest (I.A.1 – level III) / Closed black spruce-white-spruce forest (I.A.1.l – level IV)
(Viereck et al., 1992)
Circumboreal Vegetation Map – Alaska-Yukon Region:
Southern Alaska Spruce-Birch-Herb Forests
(Jorgensen and Meidinger, 2015)
BioPhysical Settings: 7616011 – Western North American Boreal Treeline White Spruce Woodland - Boreal
(LANDFIRE biophysical settings, 2009)Ecological site concept
This boreal ecological site is on warm glaciated mountain backslopes and footslopes. Site elevation is between 400 and 1,500 feet above sea level. Slopes are strongly sloped (5 – 15 percent). This site is found at warmer aspects from the southeast to northwest. Soil hydrology and temperature and a fire regime shape the vegetation on this landform. Soils are poorly drained with a water table in May and June, which shapes the vegetation on this site. Soil temperatures are warmer here than on other slopes at similar elevations due to a predominantly southerly aspect and increased subsurface gravels. These conditions create a unique forested site.
The reference state supports three communities. The reference plant community is characterized as a closed black spruce-white spruce forest (Viereck et al., 1992). It is composed of a mix of black spruce and white spruce in the overstory with an open understory of tall, medium, and low shrubs. Post-fire communities are atypically absent an overstory and are comprised of fast-growing herbaceous species, extant shrubs (in particular willow and alder), and colonizing tree samplings.Associated sites
F236XY115AK Boreal Forest Loamy Moist Slopes
F236XY115AK describes a mixed open forest on rounded mountain backslopes. It is associated with well drained soils, which is the primary driver of vegetation that separates it from F236XY201AK. F236XY201AK supports a mix of white and black spruce on poorly drained soils that are too warm to support permafrost.
R236XY107AK Western Alaska Maritime Scrub Gravelly Drainages
R236XY107AK describes swales on mountain backslopes and footslopes. It co-occurs with F236XY201AK on these landforms. R236Xy107AK is differentiated by the lack of trees and increased cover by hydrophilic shrubs such as willow.
F236XY202AK Boreal Forest Frozen Loamy Slopes
F236XY202AK describes black spruce woodlands on permafrost soils. These two ecological sites co-occur on mountain slopes and may blend together based on local conditions.
R236XY104AK Alpine Dwarf Scrub Gravelly Slopes
R236XY104AK is in the alpine and subalpine, upslope of R236XY104AK. Soil factors and temperature prevent a forest from developing on these landforms.
Similar sites
F236XY202AK Boreal Forest Frozen Loamy Slopes
Closed mixed spruce stands can appear similar to open and closed forests of just black or white spruce (Viereck et al., 1992). Both of these ecological sites are associated with poorly drained soils on mountain backslopes and footslopes. F236XY201AK is restricted to warmer soils, due to southerly aspects and greater than 50% subsurface rock fragments. It also does not support permafrost, which is present in the soils associated with F236XY202AK. Soil and site differences result in different forests in the reference plant community.
Table 1. Dominant plant species
Tree (1) Picea glauca
(2) Picea marianaShrub (1) Alnus
(2) SalixHerbaceous (1) Equisetum
