Soils of the - Agriculture and Agri-Food Canada

SEABIRD SOILS (SB)
Location and Extent : Seabird soils occur as small, scattered areas on the Fraser River floodplain, mainly i n
locations near the river. About 130 ha of pure map units and 140 ha of soil complexes dominated by Seabir d
soils are mapped . The complexes are mostly with Grevell and Page soils .
Topography and Elevation : Seabird soils are mostly gently undulating or undulating with some areas
varying to gently rolling . Slope gradients range between 1 and 8 percent . Elevations lie between 5 and 10 m
above sea level .
Parent Material and Texture : The parent material of Seabird soils consists of coarse and moderatel y
coarse textured, stone-free, laterally accreted Fraser River floodplain deposits which sometimes contain thin ,
silty lenses . Surface textures are mostly loamy sand or sand but sometimes range to sandy loam ; subsurfac e
and subsoil textures are similar but thin, silty bands or lenses are also sometimes present .
Soil Moisture Relationships : Seabird soils are imperfectly drained . They are mostly rapidly perviou s
although moderately pervious conditions occur where the silty subsoil lenses somewhat restrict permeability .
Water holding capacity is low and surface runoff is slow . Periodic watertables occur in the upper soil during th e
freshet season and are related to the water level in the Fraser River . Undykeû areas may suffer temporary
flooding during these periods . Transitory perched watertables develop above the silty subsoil lenses durin g
periods of heavy, prolonged rain .
General Soil Description : Seabird soils generally have a very dark grayish brown or dark grayish brown ,
very friable or loose, sandy, cultivated surface layer about 20 cm thick . In uncultivated areas, up to 5 cm of
variably decomposed, mainly deciduous organic material is present on the soil surface . The surface layer i s
underlain by dark grayish brown or brownish-gray, loose, sandy material at least 100 cm thick that contains fe w
to common, faint to distinct, usually reddish-brown to dark brown mottles in the lower part . Silty, olive-gray to
dark grayish brown lenses, less than 15 cm thick, are sometimes present in the sandy material and contai n
common to many, prominent, dark reddish brown to dark brown mottles . Soil reaction ranges from slightly aci d
or neutral in the upper soil to neutral in the subsoil (1 :1 H 2 O) . Soil classification is Gleyed Regosol .
Commonly Associated Soils : Grevell, Page, Dewdney and Matsqui soils are usually found in clos e
association with Seabird soils . Grevell soils are texturally similar to Seabird soils but usually occupy slightl y
higher landscape positions and are well drained . Dewdney and Matsqui soils differ from Seabird soils by havin g
silty surface and subsurface textures . Page soils usually lie topographically lower than Seabird soils, and are
poorly drained and silty in texture .
Vegetation : Cleared and cultivated areas of Seabird soils are used mainly for forage and pasture . Uncleare d
areas support a variable, mainly deciduous forest which includes black cottonwood, bigleaf maple and willow
as well as western red cedar, Douglas-fir and Sitka spruce . Rooting depth is generally unrestricted for most
vegetation .
General Land Use Comments : (1) The main agricultural limitation of Seabird soils is low soil moistur e
holding capacity which produces droughty conditions during the latter parts of the growing season . Irrigation i s
generally required to maintain good growth . The coarse textures also restrict nutrient holding ability . Fertilize r
additions (in smaller amounts) several times during the growing season as well as increasing the organic matte r
content of the plow layer will help improve this problem . (2) High water tables during the spring when the Frase r
River is high is the main restriction for urban and related development . During this season, basements and othe r
excavations are likely to contain water and septic tank effluent disposal systems are impaired . The probability o f
flooding (in undyked areas) is also a hazard . (3) Forest growth of deciduous species such as cottonwood is hig h
and this use may be best for those areas outside the dykes and on some of the islands in the river . Data from a
limited number of plots indicates the annual wood production by cottonwood to be between 12 and 15 m 3/ha .
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