Chapter 5 Weathering and Soil
Up until the 1950s, the classification of soils in Canada was based on the system used in the United States. However, it was long recognized that the U.S .system did not apply well to many parts of Canada because of climate and environmental differences. The Canadian System of Soil Classification was first outlined in 1955 and has been refined and modified numerous times since then.
There are 10 orders of soil recognized in Canada. Each one is divided into groups, and then families, and then series, but we will only look at the orders, some of which are summarized in Table 5.2. The distribution of these types of soils (and a few others) in Canada is shown in Figure 5.5.1.
|Forest soils||Podsol||Well-developed A and B horizons||Coniferous forests throughout Canada|
|Luvisol||Clay rich B horizon||Northern prairies and central B.C., mostly on sedimentary rocks|
|Brunisol||Poorly developed or immature soil, that does not have the well-defined horizons of podsol or luvisol||Boreal-forest soils in the discontinuous permafrost areas of central and western Canada, and also in southern B.C.|
|Grassland soils||Chernozem||High levels of organic matter and an A horizon at least 10 centimetres thick||Southern prairies (and parts of B.C.’s southern interior), in areas that experience water deficits during the summer|
|Solonetzic||A clay-rich B horizon, commonly with a salt-bearing C horizon||Southern prairies, in areas that experience water deficits during the summer|
|Other important soils||Organic||Dominated by organic matter; mineral horizons are typically absent||Wetland areas, especially along the western edge of Hudson Bay, and in the area between the prairies and the boreal forest|
|Cryosol||Poorly developed soil, mostly C horizon||Permafrost areas of northern Canada|
There is an excellent website on Canadian soils, with videos describing the origins and characteristics of the soils, at: Soil Classification: Soil Orders of Canada.
As we’ve discussed, the processes of soil formation are dominated by the downward transportation of clays and certain elements dissolved in water, and the nature of those processes depends in large part on the climate. In Canada’s predominantly cool and humid climate (which applies to most places other than the far north), is the norm. This involves downward transportation of hydrogen, iron, and aluminum (and other elements) from the upper part of the soil profile, and accumulation of clay, iron, and aluminum in the B horizon. Most of the , , and of Canada form through various types of podsolization.
In the grasslands of the dry southern parts of the prairie provinces and in some of the drier parts of southern B.C., dark brown organic-rich chernozem soils are dominant. In some parts of these areas, weak calcification takes place with leaching of calcium from the upper layers and accumulation of calcium in the B layer. Development of caliche layers is rare in Canada.
Organic soils form in areas with poor drainage (i.e., swamps) and a rich supply of organic matter. These soils have very little mineral matter.
In the permafrost regions of the north, where glacial retreat was most recent, the time available for soil formation has been short and the rate of soil formation is very slow. The soils are called cryosols (cryo means “ice cold”). Permafrost areas are also characterized by the churning of the soil by freeze-thaw processes, and as a result, development of soil horizons is very limited.
Examine Figure 5.5.1, which shows the distribution of soils in Canada. Briefly describe the distributions of the five soils types listed. For each one, explain its distribution based on what you know about the conditions under which the soil forms and the variations in climate and vegetation related to it.
See Appendix 3 for Exercise 5.4 answers.
Figure 5.5.1 image description: Soil order map of Canada. Chernozem is found in the southern parts of the prairies provinces (Alberta, Saskachewan, and Manitoba). Luvisol is found in the BC interior, most of central and northern Alberta, and a strip through central Saskatchewan and Manitoba. Podsol is common on the eastern and western coastal areas, as well as northern BC, and much of Quebec and the maritime provinces. Brunisol is common in the southern parts of the territories, northern Sakachewan and Manitoba, as well as parts of Ontario and Quebec. Organic soil is scattered all over the country, but most concentrated in northern Ontario and the lowlands around Hudson Bay. Cryosol is predominant in the far north. [Return to Figure 5.5.1]
- Figure 5.5.1: Image © Department of Soil Science, University of Saskatchewan. All rights reserved. Used with permission.
the process of the formation of podsol
a soil with well-developed horizons formed in temperate forested regions
a cold climate forest soil formed in which clay has been removed from the A horizon and relocated into the B horizon
a relatively immature forest soil, lacking in well-defined horizons