Soils of the - Agriculture and Agri-Food Canada

PORPOISE SOILS (PP)
Location and Extent : Porpoise soils occur only on the Sunshine Coast where they occupy small areas in th e
western part . About 280 ha of soil complexes dominated by Porpoise soils are classified ; the complexes are
mostly with Cannell, Eunice and Langdale soils .
Topography and Elevation : Topographically, Porpoise soils are moderately rolling to hilly or very steepl y
sloping with slopes varying from 10 to 50 percent . Usually they are either depressional or occupy lower slop e
positions, particularly when associated with Cannell or Eunice soils . Elevations range betwee n ' 100 and 200 m
above sea level .
Parent Material and Texture : The parent material of Porpoise soils is stony, moderately coarse to medium -
textured glacial till . Surface textures are either sandy loam or gravelly sandy loam, ; subsurface and subsoi l
textures are similar with some variation to gravelly loamy sand or loam . The subsoil, below about 1 m depth, i s
compact and usually contains discontinuous, moderately cemented patches and lenses .
Soil Moisture Characteristics : Porpoise soils are well to moderately well drained . They are moderatel y
pervious and have moderate to low water holding capacity and slow surface runoff . Temporary perche d
watertables develop above the compact subsoil during periods of heavy rain and telluric, lateral subsoi l
seepage is present during these times .
General Soil Description : Porpoise soils generally have up to 12 cm of variably decomposed organi c
forest litter on the soil surface . Under this is up to 5 cm of grayish, friable, strongly leached, sandy material . I n
turn, this is underlain by about 50 cm of friable, reddish-brown to dark reddish brown, sandy material which i s
very stony and sometimes contains scattered, moderately cemented patches, particularly in the lower part .
This zone then grades to about 50 cm of yellowish-brown to grayish-brown, friable to firm, sandy and ston y
material which sometimes contains reddish mottles in the lower part . Below about 1 m depth, compact ,
relatively unweathered soil parent material occurs which is brownish-gray, and contains scattered, moderatel y
cemented patches and few to common, reddish and yellowish mottles in the upper part . Soil reaction varies
from extremely or very strongly acid in the surface and subsurface to very strongly or strongly acid in the subsoil .
Soil classification is Orthic Humo-Ferric Podzol in most areas although a few Eluviated Dystric Brunisols als o
occur, particularly at the lower elevations .
Commonly Associated Soils : Cannell, Eunice and Langdale soils are generally closely associated wit h
Porpoise soils . Langdale soils are similar to Porpoise soils except they are sandier in texture and contai n-fewe r
stones . Cannell soils differ from Porpoise soils by being underlain by bedrock within 100 cm of the surface whil e
Eunice soils differ by consisting of 10 cm or more of organic material over bedrock .
Vegetation : Most areas of Porpoise soils have been logged and now support second-growth stands of mostl y
coast Douglas-fir with lesser amounts of western hemlock, western red cedar, red alder and vine maple .
Rooting is generally unrestricted to about 100 cm, then is somewhat impeded by the compact subsoil .
General Land Use Comments : (1) Steep slopes and stony conditions severely limit Porpoise soils fo r
agricultural uses . Pasture and forages can be produced in all except the most steep locations . (2) Urban uses o f
Porpoise soils is also limited by adverse slopes . Numerous installations of septic tank effluent disposal field s
may cause lateral effluent seepage along the surface of the compact subsoil . (3) Forest growth of species suc h
as Douglas-fir appears to be good . Potential annual wood production by this species is estimated at between 9
and 12 m 3/ha .
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