Canadian system of soil classification
Before 1955, Canadian soil testing was based on systems of classification which were similar to methods being used in the United States.
[2] This system was designed to differentiate soils created by pedogenic processes in cool climatic environments.
From general to specific, the major categories in this system are: Orders, Great Groups, Subgroups, Families, and Series.
Differences in soils are the result of the interaction of many factors: climate, organisms, parent material, relief and time.
A vertical section of a pedon displays the more-or-less horizontal layers (horizons) developed by the action of soil-forming processes.
At its most general level, the Canadian System recognizes ten different Soil Orders.
Decisions are made based on the properties of the horizons, such as thickness, Munsell colour, pH, or evidence of other soil-forming processes (eg, eluviation).
Melting of ice and frozen materials, resulting from disturbance of the surface vegetation (boreal forest or tundra), may cause slumping of the soil and disruption of roads, pipelines and buildings.
Static Cryosols lack marked evidence of cryoturbation; they are associated with sandy or gravelly materials.
Most organic soils develop by the accumulation of plant materials from species that grow well in areas usually saturated with water.
Some organic soils are composed largely of plant materials deposited in lakes; others, mainly of forest leaf litter on rocky slopes in areas of high rainfall.
Fibrisols, common in Canada, consist predominantly of relatively undecomposed organic material with clearly visible plant fragments; resistant fibres account for over 40% by volume.
These acid soils have a B horizon containing accumulations of amorphous materials composed of humified organic matter associated with aluminum and iron.
They develop most commonly in sandy materials in areas of cold, humid climate under forest or shrub vegetation.
Water moving downward through the relatively porous material leaches out basic elements (e.g., calcium), and acidic conditions develop.
They occur mainly in wet sites under humid climates and are much less common than other Podzolic soils.
They occur commonly in shallow depressions and level areas of subhumid and humid climate in association with other classes of soil on slopes and hills.
If flooding occurs when the soil temperature is above approximately 5 °C, microbial activity results in depletion of oxygen within a few days.
Depletion of ferric oxide removes the brownish colour common to many soils, leaving them grey.
As the soil dries and oxygen re-enters, the reduced iron may be oxidized locally to bright yellow-brown spots (mottles).
Thus, Gleysolic soils are usually identified by their poor drainage and drab grey colour, sometimes accompanied by brown mottles.
Properties of the B horizons are associated with sodium ions that cause the clay to disperse readily and swell on wetting, thus closing the large pores and preventing water flow.
Covering more than 4% of Canada's land area, they are the major class of soils in the southern Interior Plains, where grass is the dominant native vegetation.
Luvisolic soils occur typically in forested areas of subhumid to humid climate where the parent materials contain appreciable clay.
The major area of Gray Brown Luvisols is found in the southern part of the Great Lakes-St Lawrence Lowlands.
Vast areas of Gray Luvisols in the Boreal Forest Zone of the Interior Plains have thick, light grey eluvial horizons underlying the forest litter and thick Bt horizons with clay coating the surface of aggregates.
The soil family designation is much more specific; e.g., Orthic Gray Luvisol, clayey, mixed (mineralogy), cold, subhumid.
Series have a vast array of properties (e.g., horizon thickness and colour, gravel content, structure) that fall within a narrow range.
