Soils of the - Agriculture and Agri-Food Canada

ISAR SOILS (IS)
Location and Extent : Isar soils are scattered throughout the map area and usually occur near where rapidl y
flowing mountain streams issue into larger valleys . About 1140 ha of pure map units and 1240 ha of soi l
complexes dominated by Isar soils are mapped . The complexes are mainly with Chehalis, Elk, Harrison an d
Shalish soils .
Topography and Elevation : Isar soils vary from gently to steeply sloping with slope gradients between 5
and 30 percent . The steeper slopes usually occur near the fan apexes . Elevations range between 10 and 100 m
above sea level .
Parent Material and Texture : Coarse-textured, moderately to very stony alluvial fan deposits form th e
parent material of Isar soils . Surface textures vary from loamy sand to gravelly loamy sand while subsurface an d
subsoil textures range from gravelly sand to gravel . Stoniness varies from moderately stony on the fan aprons t o
excessively stony near the fan apexes-usually 50 percent or more of the soil volume consists of stones ,
cobbles and boulders .
Soil Moisture Characteristics : Isar soils are rapidly to well drained . They are rapidly pervious and have lo w
water holding capacity and slow surface runoff . They have variable amounts of telluric seepage at depth an d
some areas are susceptible to flooding during heavy rains by overflow from adjacent streams .
General Soil Description : Isar soils have 5 to 10 cm of mixed, deciduous and coniferous forest litter on th e
soil surface, the lower half of which is usually black and well-decomposed . Underlying this may be less than 1 0
cm of grayish-brown, very friable, sandy material slightly enriched with organic matter. The usual underlay,
however, is 1 m or more of loose, variably coloured, gravel or gravelly sand containing numerous stones ,
cobbles and boulders . Soil reactions are very strongly to extremely acid throughout . Soil classification is Orthic
Regosol.
Commonly Associated Soils : Harrison, Shalish, Elk and Chehalis soils usually occur closely associate d
with Isar soils . Harrison and Shalish soils differ from Isar soils by having podzolic soil development and th e
upper soil layers are reddish to brownish in colour . Additionally, Shalish soils are strongly cemented in th e
subsurface and subsoil . Elk soils differ by being poorly drained and having dark coloured surfaces enriched
with organic matter. Chehalis soils differ by having weak soil development intermediate between Isar an d
Harrison soils .
Vegetation : Some areas are roughly cleared and used for pasture . Uncleared areas support a variable forest ,
including coast Douglas-fir, red alder, willow, vine and bigleaf maple, dogwood, western hemlock, western re d
cedar, salmonberry, salal and huckleberry . Other than restrictions imposed by the coarse, stony textures ,
rooting depth is unimpaired .
General Land Use Comments : (1) Isar soils are mostly poorly suited for agricultural use due to lo w
moisture holding capacities and high stone contents . Some areas can be improved by stone-picking an d
irrigation for pasture and hay production . Speciality crops such as Christmas trees may also be suited . (2 )
Urban and similar uses are moderately to poorly suited for Isar soils . Basements and other excavations may b e
difficult to construct due to high stone content . Septic tank effluent disposal is efficient although incomplet e
filtration by the coarse textures may lead to ground water contamination . Potential flooding may also severel y
limit some areas . Isar soils are potential aggregate sources although screening to remove the numerous stone s
will probably be required . (3) Forest growth is moderately good . Limited plot data indicates that potential woo d
production by coast Douglas-fir and western hemlock is usually between 9 and 12 m 3/ha/yr.
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