Alaska birch

Alaska birch (Ea) - Betula neoalaskana

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Geographic range and ecological amplitudes

Description

Alaska birch is usually a tall shrub, less often, a medium-sized (<20m) deciduous broad-leaved tree, at maturity with a narrow, oval crown, slender, often curved stem, and creamy white or slightly pinkish bark.

Geographic range 

Geographic element:
Western North American/Cordilleran and northern Central

Distribution in Western North America:
north and central in the Cordilleran region

Ecological amplitudes 

Climatic amplitude:

subarctic - (subalpine boreal) - montane boreal

Orographic amplitude:

montane - (subalpine)

Occurrence in biogeoclimatic zones:
(lower SWB), BWBS

Edaphic amplitude

Alaska birch

Range of soil moisture regimes:
(fresh) - moist - very moist - wet

Range of soil nutrient regimes:
very poor - poor - medium; oxylophyte

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Tolerances and damaging agents

Root system characteristics

Alaska birch, a wetland species, is shallow-rooted without a taproot. Roots are associated with ecto- and endo-mycorrhizae.

Tolerances

Tolerance to Tolerance class Comments
low light M may regenerate in open canopy stands
frost H grows in permafrost soils
heat L extreme heat is not a concern in boreal climates
water deficit L absent on water-deficient sites
water surplus H Tolerates wet sites and sites with a strongly fluctuating water table well
nutrient (mainly N) deficiency H Very frequent in acid, very poor soils

Associated tree species and successional role

Alaska birch grows scattered with other species in ombotrophic, poorly drained sites and wetlands, especially with black spruce. It is present in early seral, mid-seral, and even in late seral stages (on wet sites) of secondary succession. As a moderately shade-tolerant tree, Alaska birch maintains its presence as a variable component of open-canopy edaphic climax communities in ombotrophic wetlands.

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Silvical characteristics

Characteristic Interpretive class Comments
reproduction capacity H early and frequent seed producer
seed dissemination capacity H dispersed by wind
potential for natural regeneration in low light L practically nil; developed mainly in canopy gaps
potential for natural regeneration in the open H providing the presence of exposed mineral soil
response of advance regeneration to release na advance regeneration does not develop in the absence of adequate light and seedbeds
self-pruning capacity in dense stands na dense stands are very infrequent
crown spatial requirements M increases with increasing stand density
light conditions beneath closed-canopy, mature stands na closed-canopy stands are very infrequent
potential productivity na non-crop species
longevity L rarely >150 years

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Genetics and notes

Notes

There are another three shrub birch species that occur frequently in interior British Columbia: shrub birch (Betula glandulosa Michx.), water birch (Betula occidentalis Hook.), and swamp birch (Betula pumila L.). All occur predominantly in boreal climates — shrub birch is an oxylophyte and diagnostic species for the SWB zone; water birch is a calciphyte represented mainly in subalpine boreal wetlands; and swamp birch is a component of montane boreal wetlands.

Alaska birch is not considered a timber crop species, however, it is a useful component of wetland subarctic and boreal ecosystems.