Soils of the - Agriculture and Agri-Food Canada

DENNETT SOILS
Location and Extent : Dennett soils are common at the higher elevations of the Coast Mountains . Althoug h
only about 15 ha of pure map units are classified, numerous soil complexes dominated by Dennett soils tota l
7060 ha. The complexes are mostly with Sayres, Lions, Palisade, Hollyburn and Whonnock soils and Roc k
Outcrop and Talus land types .
Topography and Elevation : Dennett soils are strongly rolling to very hilly with slope gradients ranging fro m
20 to over 70 percent . They occur mostly above 700 m elevation and usually occupy the tops and upper slope s
of ridges and knobs in the mountainous landscape .
Parent Material and Texture : Dennett soils have developed from organic forest litter, at least 10 cm an d
usually between 15 and 30 cm thick, over bedrock . The deposits are mainly well-decomposed (humic) material .
A thin layer of mineral soil, up to 10 cm thick, is sometimes present immediately above the bedrock .
Soil Moisture Characteristics : Dennett soils are well to moderately well drained . They are rapidly perviou s
and have a low surface runoff although substantial lateral seepage along the top of the subsurface bedrock i s
usual, especially where the bedrock is massive . Water holding capacity of the organic material is very high .
General Soil Description : Dennett soils generally consist of about 1 to 4 cm of raw to partially-decomposed
needles, twigs and leaves underlain by about 20 cm of dark reddish brown, well-decomposed, humi c
material that is matted to amorphous and contains variable amounts of mycelia . Underlying this is bedrock ,
usually granitic . A thin (less than 10 cm) layer of grayish, leached sandy material sometimes occurs betwee n
the organic material and the top of the hard bedrock . Soil reaction of the organic material is extremely acid . Soi l
Classification is Typic Folisol .
Commonly Associated Soils : Sayres, Palisade and Hollyburn soils and Rock Outcrop and Talus lan d
types usually occur in close association with Dennett soils, either in soil complexes or in adjacent ma p
polygons . Sayres and Hollyburn soils differ from Dennett soils by consisting of 10 to 100 cm of mineral soil ove r
bedrock while Palisade soils have developed from colluvium deeper than 1 m . The Rock Outcrop land type
consists of exposed rock at the land surface while the Talus land type is composed of actively accumulatin g
stones, boulders and gravel on and at the base of steep, rock faces .
Vegetation : The vegetation on Dennett soils is generally coniferous, consisting mainly of Pacific silver fir ,
western and/or mountain hemlock and yellow cedar, often in an open stand . There is usually also a relativel y
dense ericaceous shrub layer and soil surface moss cover. Rooting is limited to the depth of the underlyin g
bedrock and a layer of concentrated roots is often present on top of the rock .
General Land Use Comments : (1) Dennett soils are unsuitable for agricultural or urban uses because of
very steep slopes and shallow depths to bedrock . (2) Forest production is poor to moderate (usually betwee n
about 2 .8 and 5 .5 cubic metres of wood/ha/yr) and is limited by adverse, high elevation climatic conditions an d
shallowness to bedrock. During forest harvesting, extreme care must be taken to ensure the shallow organi c
capping is not removed or destroyed .
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