Soils of the - Agriculture and Agri-Food Canada

WHONNOCK SOILS (WH)
Location and Extent : Whonnock soils are relatively common at the higher elevations in the mountains of th e
map area . There are about 1560 ha of pure map units and 8270 ha of soil complexes dominated by Whonnoc k
soils . Most complexes are with Sayres and Golden Ears soils .
Topography and Elevation : The topography of Whonnock soils is mostly strongly to very steeply slopin g
although moderately sloping or moderately rolling to hilly areas also occur . Most slope gradients are betwee n
10 and 40 percent . The soils usually occur in lower slope positions and other areas where seepage concen -
trates . Elevations range mainly between 700 and 950 m above sea level .
Parent Material and Texture : Whonnock soils have developed from moderately coarse textured glacial til l
deposits which are more than 1 m deep, over bedrock . There is usually between 25 to 50 cm of mainly well -
decomposed (humic) organic forest litter on the mineral soil surface . The mineral soil is sandy loam or gravell y
sandy loam with some variation to gravelly loamy sand or loam ; the subsoil is strongly cemented and stone s
and boulders are common .
Soil Moisture Characteristics : Whonnock soils are imperfectly drained . They are moderately pervious i n
the upper part but this decreases to slowly pervious in the cemented subsoil . They also have moderate to hig h
water holding capacity and slow to moderate surface runoff . Perched watertables develop above the cemente d
subsoil and telluric seepage flows along the surface of this zone during all but the dryest parts of the year .
General Soil Description : Whonnock soils usually have about 35 cm of organic forst litter on the soi l
surface, the upper 5 cm of which is relatively undecomposed . The remainder is well-decomposed, very dusk y
red to black, friable, and matted to amorphous . This is underlain by about 10 cm of reddish-gray to grayish -
black, friable, strongly leached, sandy material which, in turn, is underlain by a sandy zone about 30 cm thic k
that is dark reddish brown to dark brown, weakly to moderately subangular blocky, friable and contain s
between 10 and 25 percent organic matter. This zone then grades to about 40 cm of dark brown to reddish -
brown sandy material which is moderately structured, friable and contains common, reddish to grayish mottles .
Seepage is usually present in this zone . Abruptly underlying this is 30 to 50 cm of extremely firm, dense ,
massive to coarsely platy, very strongly cemented, olive-gray to brownish-gray, sandy or gravelly materia l
containing common to many, dark brown to yellowish-brown mottles . This cemented zone grades gradually to
very firm, massive, olive-gray to gray, unweathered glacial till below about 160 cm . Soil reaction is extremel y
acid throughout except in the lower subsoil where it increases to strongly acid . Soil classification is Duric Ferro -
Humic Podzol .
Commonly Associated Soils : Golden Ears and Sayres soils generally are closely associated wit h
Whonnock soils . Golden Ears soils usually occupy slightly higher landscape positions and do not have the larg e
amounts of seepage that Whonnock soils have . Consequently, they are moderately well to well drained rathe r
than imperfectly drained . Sayres soils occupy landscape positions similar to Golden Ears soils but differ fro m
both Whonnock and Golden Ears soils by having bedrock within 100 cm of the soil surface .
Vegetation : The natural tree species on Whonnock soils are mostly Pacific silver fir, mountain hemlock an d
yellow cedar although western hemlock and western red cedar are also present in the lower parts of the soils '
elevational range . Rooting is restricted to the upper 100 cm of soil by the dense, cemented subsoil . A
concentration of roots (root mat) is usually present immediately above the cemented zone .
General Land Use Comments : (1) Whonnock soils are generally unsuitable for agricultural uses due t o
steep topography, stoniness, and adverse climate . (2) Urban and related uses are also poorly suited becaus e
of excessive topography, and high snowfall conditions . Septic tank effluent disposal is severely impeded by th e
strongly cemented subsoil . (3) Forest growth is good . Limited plot data indicates growth of western hemloc k
and Pacific silver fir ranges from 9 to 12 m3/ha/yr at the soil's lower elevational limit to between 7 and 9 m 3/ha/y r
near its' upper limits . Whonnock soils tend to "brush-in" rapidly and should be reforested with desirable, suite d
species as soon after logging as possible . Subsoil seepage requires that adequate water control structure s
(culverts and ditches) are present on access roads .
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