Field Handbook for the Soils of Western Canada Section 1 Soil

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Field Handbook for the Soils of Western Canada

Section 1

Soil Genesis and Geographical Distribution

April 2016

Dan Pennock University of Saskatchewan

Paul Sanborn University of Northern British Columbia

This is one section of a Field Guide for the Soils of Western Canada. This section is a condensed version of material from the special issue of the Canadian Journal of Soil Science on the Soil of Canada (Volume 91, PP. 671-916). The authors of each chapter are listed at the end of each section, and should be cited if material is directly quoted from this section. Full information on the Canadian System of Soil Classification can be found at: Soil Classification Working Group. 1998. The Canadian System of Soil Classification. 3rd Ed. Research Branch, Agriculture and Agri-Food Canada. Publication 1646. NRC Research Press, Ottawa, Ontario. The 3rd edition of the CSSC is available on-line at http://sis.agr.gc.ca/cansis/taxa/cssc3/index.html. The correct citation for this section is: Pennock, D.J. and Sanborn, P. 2015. Section 1: Soil Genesis and Geographical Distribution. From: D. Pennock, K. Watson, and P. Sanborn. Field Guide to the Soils of Western Canada. Canadian Society of Soil Science. 3

Table of Contents Section 1: Soil Genesis and Geographical Distribution ...... 1 1.0 introduction ...... 5 1.1 The Brunisolic Order ...... 8 1.1.1 Introduction: ...... 8 1.1.2 Dominant Genetic Processes and Diagnostic Horizons: ...... 8 1.1.3 Distribution of Great Groups ...... 8 Figure 1.1: Distribution of the great groups of the Brunisolic order in western Canada...... 9 1.1.4 Secondary Genetic Processes and the Subgroups of the Brunsiolic Order: ...... 10 1.1.5 Human Impact on Brunisolic Soil Classification ...... 10 1.2 The Chernozemic Order ...... 12 1.2.1 Introduction ...... 12 1.2.2 Dominant Genetic Processes and Diagnostic Horizons ...... 12 1.2.3 Distribution of Great Groups ...... 12 1.2.4 Secondary Genetic Processes and the Subgroups of the Chernozemic Order ...... 13 Figure 1.2: Distribution of the great groups of the Chernozemic order in western Canada. ... 14 1.2.5 Human Impact on Chernozemic Soils ...... 15 Figure 1.3: Schematic diagram of a typical catena in an agricultural landscape...... 16 Figure 1.4: Simplified evolutionary sequence of Chernozemic subgroups...... 17 (from Pennock et al. 2011)...... 17 1.3 The Cryosolic Order ...... 18 1.3.1 Introduction ...... 18 1.3.2 Dominant Genetic Processes and Diagnostic Horizons ...... 18 1.3.3 Distribution of Great Groups ...... 18 1.3.4 Secondary Genetic Processes and the Subgroups of the Cryosolic Order ...... 18 Figure 1.5: Diagram showing the location and extent of a pedon in an Orthic Turbic Cryosol; ...... 19 Figure 1.6: Distribution of the great groups of the Cryosolic order in western Canada...... 20 1.3.5 Human Impact on Cryosolic Soils ...... 21 1.4 The Gleysolic Order: ...... 22 1.4.1 Introduction ...... 22 1.4.2 Dominant Genetic Processes and Diagnostic Horizons ...... 22 Figure 1.7: Distribution of Gleysolic soils in western Canada...... 23 1.4.3 Distribution of Great Groups: ...... 24 1.4.4 Secondary Genetic Processes and the Subgroups of the Gleysolic Order ...... 24 1.4.5 Human Impact on Gleysolic Soils ...... 24 1.5 The Luvisolic Order ...... 26 1.5.1 Introduction ...... 26 1.5.2 Dominant Genetic Processes and Diagnostic Horizons ...... 26 1.5.3 Distribution of Great Groups ...... 26 Figure 1.8: Distribution of Gray Luvisols in western Canada. Gray Brown Luvisols do not occur in western Canada...... 27 1.5.4 Secondary Genetic Processes and the Subgroups of the Luvisolic Order ...... 28 1.5.5 Human Impact on Luvisolic Soils ...... 29 1.6 The Organic Order ...... 30 1.6.1 Introduction ...... 30 1.6.2 Dominant Genetic Processes and Diagnostic Horizons ...... 30 1.6.3 Distribution of Great Groups ...... 30 Figure 1.9: Distribution of Organic soils in western Canada...... 31 1.6.4 Secondary Genetic Processes and the Subgroups of the Organic Order ...... 32 4

1.6.5 Human Impact on Organic Soils ...... 32 1.7 The Podzolic Order ...... 33 1.7.1 Introduction ...... 33 1.7.3 Distribution of Great Groups ...... 33 Figure 1.10: Distribution of great groups of the Podzolic order in western Canada...... 34 1.7.4 Secondary Genetic Processes and the Subgroups of the Podzolic Order ...... 35 1.7.5 Human Impact on Podzolic Soils ...... 35 1.8 The Regosolic Order ...... 37 1.8.1 Introduction ...... 37 1.8.3 Distribution of Great Groups ...... 38 1.8.4 Secondary Genetic Processes and the Subgroups of the Regosolic Order: ...... 38 1.8.5 Human Impact on Regosolic Soils ...... 39 1.9 The Solonetzic Order ...... 41 1.9.1 Introduction: ...... 41 1.9.2 Dominant Genetic Processes and Diagnostic Horizons ...... 41 Figure 1.12: Distribution of great groups of the Solonetzic order in western Canada...... 42 Figure 1.13. Major genetic or pedogenic processes in the genesis of Solonetzic soils in Canada (modified after Pawluk 1982)...... 43 1.9.3 Distribution of Great Groups ...... 44 1.9.4 Secondary Genetic Processes and the Subgroups of the Solonetzic Order ...... 44 Table 1.1: Subgroups and associated criteria for soils of the Solonetzic order ...... 45 1.9.5 Human Impact on Solonetzic Soils ...... 45 1.10 The Vertisolic Order ...... 46 1.10.1 Introduction ...... 46 1.10.2 Dominant Genetic Processes and Diagnostic Horizons ...... 46 1.10.3 Distribution of Great Groups ...... 47 1.10.4 Secondary Genetic Processes and the Subgroups of the Vertisolic Order: ...... 47 Figure 1.14: Distribution of great groups of the Vertisolic order in western Canada...... 48 1.10.5 Human Impact on Vertisolic Soils ...... 49

probably associated not only with the 1.0 introduction obvious vegetation difference (grassland to forest) but also with the There is a pattern to the distribution absence of burrowing animals such as of soils and our goal in this section is gophers (and the bioturbation both to show the regional-scale associated with them) in the forest. In pattern of western Canadian soils and forested areas, the absence of Podzols briefly examine the factors that from the Prairie provinces (Figure control this pattern. 1.10) is probably due to the colder and drier climate that occurs in the The factors that control soil Prairies (in comparison to much of distribution have been well British Columbia). In this case the established since the early work of soil effect of the climate is probably less on scientists such as Hans Jenny and the the vegetation itself than on the soil Manitoban pedologist Joe Ellis in the microorganisms that produce the 1930s and 1940s. The distribution of decomposition products required for soils is controlled by seven soil- podsolization to occur. These climatic forming factors: climate, organisms, limits to decomposition in the Prairies parent material, topographical cause the less-developed Brunisols to position (or relief), time, groundwater, dominate (Figure 1.1). The role of and the modifying effects of human burrowing animals and activity. These factors combine to microorganisms illustrate why control the specific soil-forming organisms (and not just vegetation) processes that have affected a soil are included as a soil-forming factor. during its development; in turn the particular set of soil-forming factors Parent material is a major factor in result in specific horizons occurring in Canadian soils because our soils are the soil profile. These horizons are the quite young by global standards and basis for soil classification. The effects weathering has not fundamentally of the soil-forming factors are readily altered soil properties such as texture apparent in the maps of the and mineralogy, both of which are distribution of great groups of soils largely inherited from the parent that follow in this section. material. The great majority of western Canadian soils are formed on The effect of climate and organisms parent materials deposited during the are closely linked, and the regional- final stage of the great Pleistocene scale distribution of several great glaciations and the characteristics of groups closely corresponds to this. the glacial parent materials has pre- The transitions of the Chernozemic determined the genetic pathway taken great groups from the drier, warmer by some soils. Brown great group through to the transitional Dark Gray great groups at For example, In the grasslands of the the forest margin (Figure 1.2) are a Prairies the “normal” soils are classic example of this. In some cases Chernozemic and the distribution of the transition between Chernozems other soil groups is largely controlled and Luvisols can be very abrupt, and is by parent material. Vertisolic soils are 6

high clay soils with a significant capacity to shrink and swell with Topography and groundwater are changing soil moisture and are found often closely linked as controls on soil only on clayey glacio-lacustrine (or formation due to the simple fact that lake) deposits. Many examples of water moves downslope. Where water Solonetzic soils are also found on high concentrates in the landscape (on the clay parent materials but in this case soil surface or within the soil or the parent materials have significant sediments themselves) for a sufficient contents of exchangeable sodium length of time, a distinct set of soil (Na+) on the charged clay surfaces. processes associated with oxygen- Finally some areas of sandy glacio- depleted conditions occurs. In the fluvial or lacustrine sediments have forested areas of western Canada been destabilized by the wind, and areas of long-term water saturation these areas of dunes are home to give rise to Organic soils (or peats in Regosolic soils in the Prairies. common language). In grassland areas episodic droughts expose pond In forests throughout western Canada sediments and the organic materials the distribution of Luvisolic versus decompose, and distinctive Gleysolic Podzolic/Brunisolic soils has a broad- soils form in the wetlands. In some level parent material control. Luvisolic areas of the grasslands, groundwater soils typically form in poorly-sorted from deeper in the sediment interacts till laid down directly by the ice with the soil surface, and these sheets. The till has sufficient clay discharging groundwater areas often present to meet the requirements for bring high salt loads to the soil, Luvisol formation. Podzols and forming saline areas. Brunisols form on sandy deposits of glacio-fluvial or glacio-lacustrine Soils throughout western Canada have origin, which are typically very low in been significantly altered by human clay and which rapidly transmit water activity. By far the greatest through the soil. transformation has been in the former grasslands, where the great majority Soils such as the Chernozems or of the soils have been converted to Podzols take thousands of years to agricultural uses. Forest harvest has form. The great majority of western also lead to significant human impact. Canadian soils have formed in the The most common impact of human 10,000 to 17,000 years since the activity has been to accelerate erosion landsurface was exposed after retreat by water, wind and tillage. In eroding of the glacier but in some cases the areas these processes leads to time of formation has been much less. truncation of soil horizons and This is the case wherever instability of ultimately regression of the soil back the landsurface occurs – for example to the least-developed soils, the in sand dunes or in river valleys Regosols. Many cultivated landscapes where active erosion or sedimentation now have Regosolic soils on highly occurs. Soils associated with these eroded knolls. The eroded soil is often unstable surfaces are classified into deposited in lower-slope positions, the Regosolic order. 7 leading to difficult-to-classify buried understanding of the genesis of soils (or cumulic) soils. continues to evolve, and that revision of the CSSC to reflect our evolving The Canadian System of Soil knowledge is essential if soil genesis Classification (CSSC) is ill-equipped to and classification is to remain a deal with human disturbance as the discipline grounded in science. classes in the system were developed for native soils. Soils that have A note on maps: The maps through this undergone significant disruption section were developed by Darrel through, for example, resource Cerkowniak of Agriculture and Agri- extraction activities such as oilsand or Food Canada and we are very grateful pipeline development no longer have to Darrel for his work on this. They “natural” soil horizons. The same is are based on the 1:1,000,000 Soil true though the urban areas of Canada Landscapes of Canada map series, and – little if any of the ”natural” soil reflect a scale of generalization remains in urban areas. In 2011 a appropriate for this broad scale. For group of Canadian soil scientists all but two maps (Regosol and proposed the adoption of an 11th soil Gleysol) the soils indicated in the map order in Canada - the Anthroposolic occupy at least 40% of the map order – which would facilitate polygons shown. This means that up description of these human- to 60% of the pits you dig in that constructed soils. Unfortunately it has polygon could have other soils proven difficult to adequately test and associated with it – for example, the refine the proposed order and it typical Chernozemic catena shown in remains unofficial at the time this Figure 1.3 has two other orders handbook was finalized (late 2015). shown, and in some polygons Solonetzic soils also occur in these In the following parts of this section catenas. we have summarized the current state of knowledge about the formation of The Gleysolic and Regosolic maps western Canadian soils. Much more show polygons where at least 10% of material can be found in the special the polygon has these soils. Both of issue of the Canadian Journal of Soil these soils typically occur in Science on the Soils of Canada association with other soils and rarely (Volume 91, PP. 671-916). It is very dominate (i.e., occupy > 40%) of the important to note, however, that our polygons.

include soils with incipient to 1.1 The Brunisolic Order moderate soil formation. Transformation of parent material is 1.1.1 Introduction: evident from the formation of Brunisolic soils form under forests pedogenic structure, brownish or and have brownish-coloured B (Bm) reddish coloured B horizon and/or horizons. Brunisols are imperfectly to carbonate removal. They lack rapidly drained soils that have not appreciable quantities of illuvial clay developed features diagnostic of other or organically complexed Al and/or Fe orders, but which do features that compounds within clearly express significant pedological the solum and are permafrost-free development (unlike the Regosolic within the control section. order). Although principally a forested soil, Brunisols span the range of The distinguishing feature of climates, parental materials and Brunisolic soils is development of a physiographies of western Canada brownish-coloured Bm horizon under (Fig. 1.1). In some cases, Brunisols forest vegetation. This horizon form under non-forested conditions, generally has a rather strong chroma primarily permafrost-free tundra and and redder hue and often a structure alpine meadow environments, or may that is noticeably different from the exist as the result of cultivation in overlying A horizon or underlying C agricultural settings. horizon. There is very little if any

accumulation of clay, and relatively Although exceptions occur, the great minor accumulation of Fe and Al majority of Brunisolic soils are minerals in the B horizons of associated with sandy and gravelly Brunisolic soils. Brunisolic soils have a parent materials that are resistant to Bm horizon (or alternatively a Bfj or the expression of soil formation. These Btj horizon or both) at least 5 cm parent materials dominate on the thick, a diagnostic feature that Canadian Shield and on other igneous separates these soils from Regosols. and metamorphic rocks, and on glaciofluvial and sandy eolian deposits 1.1.3 Distribution of Great Groups through western Canada. As Brunisols are primarily forest soils, much of their taxonomy at the great group level can be related to humus 1.1.2 Dominant Genetic Processes and form. Where mor humus forms occur Diagnostic Horizons: (i.e., LFH horizons at the mineral soil No single pedogenic process operates surface), the soils are classified as in all Brunisols except perhaps Eutric (pH of ≥ 5.5 (all pH values in leaching; virtually all pedogenic 0.01 M CaCl )) or Dystric Brunisols processes are active to some extent 2 (pH < 5.5) depending on the pH of but none predominates. Brunisols 9

Figure 1.1: Distribution of the great groups of the Brunisolic order in western Canada.

the B horizon. Where conditions lead process of active melanization, to mull or moder humus forms (i.e., Sombric (pH < 5.5) and Melanic incorporation of the leaf organic Brunisols (pH of ≥ 5.5) result material into the mineral horizon as depending again on the pH of the B an Ah or Ahe horizon) through the horizon. As can be seen from Figure 10

1.1, however, these great groups are Luvisol formation. These sediments rare in western Canada, which is are often derived from calcareous dominated by Eutric and Dystric great parent rocks, and Eutric Brunisols groups. dominate in this region. Melanic Brunisols are rare in western Canada. Generally the acidic great groups (Dystric and Sombric) form on parent In regions of discontinuous materials derived from more acidic permafrost, Brunisols tend to be found igneous and metamorphic rocks such in association with Cryosolic soils, on as those of the Canadian Shield landscape positions not underlain by (Figure 1.1). The neutral and alkaline near-surface permafrost such as great groups (Melanic and Eutric) are rapidly drained materials and/or associated with parent materials south facing slopes. derived from sedimentary rocks, which have a higher initial base (e.g. 1.1.4 Secondary Genetic Processes and Ca2+, Mg2+, Na+, K+) content. the Subgroups of the Brunsiolic Order: The secondary genetic processes In humid environments and acidic common to all great groups are the parent materials where Podzolic soils formation of an Ae horizon at the dominate, Dystric Brunisols form on mineral soil surface (Eluviated parent materials that either lack the subgroup) and gleying (Gleyed and mineralogy or textural characteristics Gleyed Eluviated subgroups). The necessary to develop Podzolic B more acidic Dystric great group also horizons, or are young enough that has examples with a duric horizon insufficient time has elapsed to allow (Duric subgroups) but these are rare diagnostic Podzolic features to in western Canada. develop. Often Podzols and Dystric Brunisols occur in the same Gleyed: Gleyed subgroups of the geographic region and are difficult to Brunisolic order have faint or distinct distinguish in the field based on colour mottles within 50 cm of the surface, or alone. Sombric Brunisols are much distinct to prominent mottles at 50— less common but are found in 100 cm. The Gleyed identifier is also southern B.C. in Fraser delta and added to other Eluviated subgroup Vancouver Island. identifiers as well.

In boreal and mixedwood forest Eluviated: All great groups have environments, Brunisols tend to co- Eluviated subgroups where an Ae or exist with Luvisolic soils. Luvisols Aej horizon ≥ 2 cm thick occurs. occur where till and glaciolacustrine parent materials contain enough clay Duric: The duric horizon is a strongly to allow the formation of textural- cemented horizon that occurs in the contrast B horizons, and the Sombric and Dystric great groups. Brunisolic soils occur on sandy and gravelly glaciofluvial and eolian 1.1.5 Human Impact on Brunisolic Soil parent materials where there is Classification insufficient clay present to allow 11

Some Brunisols have been cultivated depending on pH of the uppermost 25 for use in agriculture. In these cases, cm of the B horizon. the plough layer may incorporate various native surface and subsurface For further information see: horizons into an organic matter-rich Ap horizon. If the Ap is at least 10 cm Smith, C. A. S., K. T. Webb, E. Kenney, thick and has a moist colour value <4 A. Anderson, and D. Kroetsch. 2011. and part of the Bm, Bfj or Btj horizon Brunisolic soils of Canada: Genesis, remains below the Ap, these soils are distribution, and classification. classified as Melanic or Sombric Canadian Journal of Soil Science 91:695-717.

cordilleran forests, graying caused by 1.2 The Chernozemic Order weathering and eluviation becomes evident in the surface layer, and an 1.2.1 Introduction Ahe horizon is found in this Chernozemic soils are formed by the transitional region. This horizon has a action and interaction of a host of characteristic salt-and-pepper biodynamic processes. They form in appearance when the soil is dry and grasslands and experience substantial the aggregates are crushed by hand. additions of organic matter through the root mass of the grasses. This The diagnostic horizon of the plant-derived organic material Chernozemic order is the undergoes microbial degradation and Chernozemic A horizon. The native a small proportion of it forms a Chernozemic A horizon has three biochemically complex suite of soil main pedological features: dark organic matter. The upper portion of colours caused by relatively high SOM the soil also undergoes very contents, well-developed granular substantial mixing (or turbation) by a structure, and high contents of range of burrowing animals and exchangeable bases (i.e., Ca2+, Mg2+ , smaller soil invertebrates, creating a K+ , and Na+ ) with Ca2+ dominating very porous and well aggregated the base content. The colour value surface soil layer (the Chernozemic Ah (i.e., the relative lightness or horizon). These soils are a major darkness) is the dominant criterion of terrestrial reservoir of soil organic the three components of the Munsell carbon. colour system for classification of the 1.2.2 Dominant Genetic Processes and great groups of the Chernozemic Diagnostic Horizons order. The addition of organic matter (OM) from grass and its subsequent The Chernozemic Ah and Ahe horizons transformation to soil organic matter are found at the surface of native (SOM) is central to Chernozemic soil (undisturbed) soils but because of genesis. These processes lead to the their inherently high fertility most darkening of the surface soil horizon Chernozemic landscapes have been through the formation of brown to converted to agricultural use. A black OM-mineral aggregates. In ploughed A horizon is denoted with an native soils these aggregates form a p suffix (Ap); these Ap horizons can well-developed granular structure. still meet the criteria for a The SOM is mixed in a relatively Chernozemic A horizon. homogenous layer (the Chernozemic A horizon) through the activity of a 1.2.3 Distribution of Great Groups range of burrowing animals such as ground squirrels, pocket gophers, and The great majority of Chernozemic badgers. soils are found in the Interior Plains in

the region colloquially known as the In the transitional region where the Canadian Prairies (Figure 1.2). This grassland grades to the boreal and region has mean annual temperatures 13 between 0.5 and 3.5oC and substantial 1.2.4 Secondary Genetic Processes and water deficits ranging between the Subgroups of the Chernozemic Order approximately 200 mm in the driest There are seven subgroups in the portions of the Brown soil zone to 80 Chernozemic order. Three of them to 90 mm in the transitional (Vertic, Solonetzic, and Gleysolic) grassland-forest Boreal Plains represent soils that have properties of Ecozone. Chernozemic soils are also both the Chernozemic order and found in the Montane Cordillera another order in the CSSC. Soils in Ecozone in valleys of the southern these three subgroups have horizons interior of B.C., and in the Peace River that resemble those of the other region of Alberta. Small areas of orders, but do not meet their strict Chernozemic soils also occur under taxonomic requirements. These localized grasslands on south-facing horizons are normally assigned a j slopes in the Boreal Cordillera suffix (e.g Bnjtj or Bgj), indicating a Ecozone in northwestern B.C. and juvenile form of the diagnostic horizon southern Yukon. of the other three orders.

The great groups of the Chernozemic Vertic subgroup: These soils have order show a clear geographical properties of both the Chernozemic zonation. The Brown great group and the Vertisolic order. They develop occupies the driest region of the in clay and heavy clay parent Prairies (in the SE corner of materials. They have slickenside B Alberta/SE corner of Saskatchewan) (Bss) and/or C (Css) horizons within 1 and the great groups grade through m of the surface and may have a weak the Dark Brown, Black, and Dark Gray vertic (Bvj or BCvj) horizon. great groups as the water deficit decreases west, north, and east of the Solonetzic: These soils have weakly driest region. The darkening colour of developed properties indicative of the A horizon reflects the increase in solonetzic soil processes in addition to SOM as the water deficit decreases. those of the Chernozemic order. Soils This geographical gradation is the of this subgroup have Bnj, Bnjtj, or basis of the soil zones, which are Btnj horizons. The final assignment of widely used in agricultural the proper suffix (i.e., Bnj or Bn) may applications. require a chemical test for the ratio of exchangeable calcium to exchangeable sodium. They are associated with high sodium parent materials, usually of glaciolacustrine origin.

Figure 1.2: Distribution of the great groups of the Chernozemic order in western Canada.

Gleyed: Gleyed subgroups of the more soluble than the carbonates Chernozemic order are very common occur, and a sa suffix is added (e.g. in landscapes that have wetlands. Bsagj, Csagj). No separate subgroup Both the Gleyed Chernozemic identifies these soils but they subgroups and soils of the Gleysolic identified as a saline phase (e.g. order have mottles resulting from Gleyed Rego Chernozem, saline alternating reduction-oxidation phase). conditions caused by periodic water saturation. The key distinction is the Rego, Calcareous, Orthic, and colour contrast of mottles: Gleyed Eluviated Subgroups: Chernozemic subgroups have faint or The other four subgroups of the distinct mottles within 50 cm of the Chernozemic order represent an surface, whereas soils of the Gleysolic idealized evolutionary sequence for Order have prominent mottles within these soils (Figure 1.4). The first three 50 cm. The Gleyed identifier is also represent different stages in the loss added to other subgroup identifiers of calcium carbonate from the profile, for Chernozemic soils (e.g. Gleyed and the Eluviated subgroup Rego, Gleyed Calcareous, Gleyed experiences weathering of the lower A Eluviated etc.) (to form an Ae or Aej) and limited enrichment of clay in the B (i.e., Btj). Gleyed Chernozemic subgroups are All of these subgroups are commonly common in a fringe around wetlands found together along hillslopes in in Prairie landscapes (Figure 1.3). The undulating, rolling, and hummocky center of the wetland typically has landscapes, often over relatively short Gleysolic soils. The Gleyed (50 to 100 m) distances. Rego Chernozemic soils often also contain subgroups are now very common on secondary salts that are deposited knolls in agricultural landscapes due when solute-rich water from the horizon truncation from erosion wetland moves laterally into the processes (see below). surrounding landscape due to impermeable underlying sediments. The water is lost through evaporation 1.2.5 Human Impact on Chernozemic and transpiration, and secondary salts Soils are deposited in the upper horizons of The great majority of Chernozemic the soil. soils have been converted to agricultural use, and the surface Where the pond water is relatively horizons have been modified through fresh, calcium carbonate is deposited tillage and erosion. Tillage mixes the in the A and/or B horizons (e.g. Ahca, upper 10 to 20 cm of the soil and Bcagj, Ccagj). Soils of the Gleyed Rego creates a relatively homogeneous Ap subgroups and Gleyed Calcareous horizon. In non-level landscapes, subgroup occur in these situations, tillage and water erosion removes and the phase designator surface soil from knolls and upper (carbonated) should be applied to portions of hillslopes, and deposits these soils as well. Where the pond this soil in footslopes and water is more saline, secondary salts depressional areas. Often B and C 16 horizon material becomes slope position leads to over- incorporated into the tillage layer in thickening of A horizons but typically eroded positions, leading to (for does not effect the classification. example) Apk or Apca horizons. This Wind erosion was very common in increases the areal extent of Rego level landscapes on these soils prior to subgroups and Regosolic soils in these the adoption of soil-conserving tillage eroded positions. Deposition of methods, and lead to the loss of A eroded A horizon sediment in lower horizons.

Figure 1.3: Schematic diagram of a typical catena in an agricultural landscape.

The figure shows the main hydrological process domains, water flow directions, depth to CaCO3, development of B horizon features and the distribution of orders and subgroups along a catenary sequence in hummocky till landscapes (from Pennock et al. 2011).

Figure 1.4: Simplified evolutionary sequence of Chernozemic subgroups.

(from Pennock et al. 2011).

For further information see:

Pennock, D., A. Bedard-Haughn and V. Viaud. 2011. Chernozemic soils of Canada: Genesis, distribution, and classification. Canadian Journal of Soil Science 91:719- 747.

created by cryogenic processes, with 1.3 The Cryosolic Order platy structures attributed to ice lens formation, and rounding of granular aggregates resulting from frost action. 1.3.1 Introduction Cryosolic soils are defined by the 1.3.3 Distribution of Great Groups influence of permafrost and are the The distribution of Cryosolic soils most extensive soil order, occupying broadly parallels permafrost zonation 35% of Canada’s soil area. Soils in this at the national scale, with Turbic order must have permafrost within 1 Cryosols being the most extensive m of the surface, or within 2 m if great group. Near the southern cryoturbated (i.e., horizons disrupted margin of the Discontinuous by mixing and/or displacement Permafrost Zone, Organic Cryosols are related to frozen conditions). predominant in the peatlands of the Hudson Bay Lowlands. In the more complex topography of the Cordillera, 1.3.2 Dominant Genetic Processes and Cryosols can occur near the southern Diagnostic Horizons limits of permafrost where suitable Although the Cryosolic order does not microclimatic conditions have allowed have a specific diagnostic horizon, a isolated patches of permafrost to characteristic suite of morphological develop, such as on northerly aspects features results from cryogenic or on exposed ridges with limited processes (e.g. segregated ice lens snow cover. formation and frost heave), both within the soil profile and as their 1.3.4 Secondary Genetic Processes and surface expression. The latter include the Subgroups of the Cryosolic Order a diversity of patterned ground types Similar subgroups are designated (e.g. ice wedge polygons, sorted within the Turbic and Static great circles, earth hummocks, net, stripes), groups. The degree of brunification which are mirrored by cyclic patterns (moderate degree of weathering and of horizonation at the pedon scale formation of brownish B horizons) is (Figure 1.5). Cryoturbated horizons, captured by Orthic and Brunisolic designated by the “y” suffix, exhibit subgroups which are separated based broken boundaries and provide on the presence of Bm horizons < 10 evidence for the mixing processes that cm or ≥ 10 cm thick, respectively. are an important pathway for organic These distinctions are combined with matter incorporation at depth within soil reaction criteria which separate and below the active layer. Dystric and Eutric subgroups at a pH Distinctive patterns of structure limit of 5.5. development within horizons are 19

Figure 1.5: Diagram showing the location and extent of a pedon in an Orthic Turbic Cryosol; Note the discontinuous Ah and Bmy horizons resulting from cryoturbation (From Tarnocai and Bockheim 2011) 20

Figure 1.6: Distribution of the great groups of the Cryosolic order in western Canada.

Regosolic subgroups are designated absent. The high moisture content where Bm horizons are completely prevailing in active layers results in 21 some degree of gleying in most Turbic ground ice contents. The seasonally and Static Cryosols, so only a degree of thawed (active) surface layer of gleying analogous to that of Gleysolic Cryosols will usually have a high soils is specifically recognized moisture content, giving it limited (Gleysolic subgroups). Clay bearing capacity and a tendency to translocation can be an accessory thixotropic behaviour (liquification process in finer-textured Cryosols, but when mechanically vibrated) when sufficient development of Bt horizons high in silt content. Subsidence, to designate Luvisolic subgroups is thermokarst formation, and mass recognized only for the Static Cryosol wasting can result from inadequate great group. design and construction practices during resource extraction and Organic matter accumulation as a infrastructure development. At the surface peaty layer (O or H horizons) national, and in fact global, scale, the 15- to-40 cm thick is designated by most dramatic human impacts on Histic subgroups in the Turbic and Cryosolic soils are resulting from the Static Crysols, but Cryosols with amplification of climate change at high thicker accumulations (> 40 cm) are latitudes. Potential northward shifts in placed in the Organic great group. the southern limits of permafrost Similar to distinctions made in the could enable thawing and oxidation of Organic order, which has subgroups the enormous reserves of organic based on degree of humification carbon currently sequestered in (Fibric, Mesic, Humic), proximity of Cryosolic soils, estimated at 39% of all underlying mineral material (Terric), organic carbon in Canadian soils. and presence of ice layers (Glacic). For further information see: Tarnocai, C. and Bockheim, J. G. 2011. 1.3.5 Human Impact on Cryosolic Soils Cryosolic soils of Canada: Genesis, Localized impacts of human activity distribution, and classification. Can. J. on Cryosolic soils can be severe, Soil. Sci. 91: 749_762. particularly where surface disturbances change the thermal balance of surficial materials with high 22

observable criteria noted in the field; 1.4 The Gleysolic Order: low chroma can also be described as ‘‘gley’’, ‘‘dull’’, ‘‘drab’’, ‘‘grey’’ or ‘‘blue- 1.4.1 Introduction grey’’ in colour. Mottles are spots or Soils developed under periodic or blotches within the soil that are of a prolonged saturated (or waterlogged) contrasting colour to the matrix as a conditions belong to the Gleysolic whole. Mottles tend to be reddish- to Order in the Canadian System of Soil yellowish-brown. For those horizons Classification. The oxygen-depleted with low chroma, prominent mottles, (or anoxic) conditions that occur due or both, the suffix ‘‘g’’ is used (for to saturation lead to distinctive example, Aeg, Btg, Cg, etc.) and is the morphological features such as dull diagnostic horizon for the Gleysolic matrix colours and mottles, which are order. generally termed gley features.

The oxidation-reduction (redox) Gleysolic soils are not unique to any processes associated with gleization, particular climate or parent material whereby iron (Fe), and to a lesser and, as such, are found throughout extent manganese (Mn), are western Canada, often in associations transformed and transferred, give rise or complexes with other orders to the characteristic morphological (Figure 1.X). They are commonly features of Gleysolic soils: dull- found in wetland environments, coloured (reduced) soil matrix and providing key ecosystem services such brightly coloured (oxidized) mottles. as wildlife habitat and filtration of In simplest terms, in saturated, pollutants in runoff. anaerobic soils, Fe3+ is used as an 1.4.2 Dominant Genetic Processes and alternate electron acceptor by Fe- Diagnostic Horizons reducing bacteria, and is reduced to 2+ 2+ Gleysolic soils are primarily classified Fe . Because Fe is more mobile, it based on their diagnostic colour can be removed from the profile, criteria, which are readily observable creating the dull-coloured matrix; in the field and reflect a reducing where the soil dries out, creating 3+ (anoxic) environment. For non-red oxidizing conditions, iron oxides (Fe soils (soils with red parent material ) re-precipitate, creating the brightly are very rare in western Canada), low coloured mottles. chroma of the ped faces or the soil matrix as a whole is one of the first 23

Figure 1.7: Distribution of Gleysolic soils in western Canada.

Slight variations in topography can determine the degree of gleying, with The anoxic conditions retard the those positions lowest in the decomposition of organic matter, and landscape being most prone to it is common to have an organic (O) reducing conditions. As a result, one layer on the surface of undisturbed might observe highly anaerobic Gleysolic soils. Fibric O Horizons conditions in the lowest position of between 15 and 60 cm thick and mesic the landscape with oxidizing or humic O horizons 15 to 40 cm thick conditions just a few meters away. are recognized as phases (e.g. Humic 24

Luvic Gleysol, peaty phase). If the O Fera subgroup: The Fera subgroup is horizons are thicker than these limits typically found in association with they are classified as Organic soils. soils of the Podzolic order, and include a horizon of accumulated hydrous iron 1.4.3 Distribution of Great Groups: oxide (Bgf or Btgf). There are three great groups within the Gleysolic order: Luvic Gleysol, Fragic subgroup: (Luvic Gleysols only). Humic Gleysol, and Gleysol. Gleysol is Fragic Luvic Gleysols have a fragipan the only great group with no (Btgx or Btg and Bxg), which is a additional (to gleying) major process. loamy subsurface horizon that seems Clay translocation is the secondary to be cemented when dry but is weak major process in the Luvic Gleysol to moderately brittle when moist. great group and is reflected by the presence of a horizon of clay Humic subgroup: (Luvic Gleysols only). accumulation (Btg) and often an These soils have the characteristics of eluvial horizon as well (Aeg). Organic the Luvic Gleysol great group as well matter decomposition is the as an Ah or Ap horizon that meets the secondary major process in the Humic criteria outlined for the Humic Gleysol Gleysol great group, leading to great group. In many cultivated development of a thick (≥ 10 cm) Ah landscapes the surface A horizon in horizon (or Ap ≥ 15 cm) with at least Gleysolic soils has been overthickened 2% organic carbon and dark colours by deposition of sediment (see below). similar to those associated with the Chernozemic order reflecting Rego subgroup: (Humic Gleysol and significant additions of humus. Gleysol great groups only) Gleysolic soils where the B horizon is less than 10 cm thick. 1.4.4 Secondary Genetic Processes and the Subgroups of the Gleysolic Order Vertic subgroup: The Vertic subgroups 1.4.5 Human Impact on Gleysolic Soils are used for profiles that have all of In some regions of the Prairies, the characteristics of a given great Gleysolic soils have been artificially group as well as a slickenside horizon drained by producers to increase the (Bgss or Cgss) for the Vertic subgroup. arable area in fields. Subsurface drainage may increase translocation Solonetzic subgroup: The Solonetzic of carbon and other nutrients, subgroups are used for profiles that movement of clay (i.e., lessivage), and have all of the characteristics of a induce changes in Fe and Mn given great group as well as a dynamics. Changes in redoximorphic solonetzic B horizon (Bng, Bntg) for features and increased structure were the Solonetzic subgroup. They are observed in gleyed soils of other associated with high sodium parent regions within 30 yr of drainage. The materials, usually of glaciolacustrine increase in structure was attributed to origin. increased faunal activity (earthworms, etc.) under increasingly aerobic conditions, increased 25 lessivage with greater vertical water eroded soil in lower-slope positions movement, and the effects of more results in an over-thickened A frequent wet-dry cycles on shrink- horizon. Normally the diagnostic swell clays. The most significant horizon with the g suffix must occur change in the type and intensity of within 50 cm of the surface, but if the soil-forming processes occurs within a Ah or Ap is thicker than 50 cm, the few meters of the drainage line, colour criteria apply to the mineral dramatically increasing the variability horizon immediately below the over- of soil properties over short distances. thickened horizon.

In cultivated hummocky prairie For further information see: landscapes, one of the most striking features associated with many Bedard-Haughn, A. 2011. Gleysolic Gleysolic profiles is the very thick Ap soils of Canada: Genesis, distribution, horizon, which is a consequence of and classification. Canadian Journal of tillage translocation in combination Soil Science 91:763-779. with water erosion. Deposition of

criteria for Bt horizons are normally 1.5 The Luvisolic Order classified as Luvisolic soils regardless of the genetic cause of the higher amount of clay in the Bt horizon. Soils 1.5.1 Introduction with the higher clay Bt horizons share Luvisolic soils are the predominant the same forest productivity and forest soils of much of western management regimes regardless of Canada, occurring under coniferous, the origin of the clay in the Bt horizon. mixedwood, and deciduous forests. Soils of this order are characterized by 1.5.3 Distribution of Great Groups an B horizon (Bt) in which silicate clay Of the two Luvisolic great groups, the has accumulated, underlying a light- Gray Luvisols account for almost all coloured eluvial horizon. occurrences of this order in western Canada. (Minor occurrences of Gray Brown Luvisols have a distribution in 1.5.2 Dominant Genetic Processes and southern coastal British Columbia Diagnostic Horizons which is too restricted to appear at the Formation of the required Bt horizon, map scale of Figure 1.8.) which must exhibit a higher amount of silicate clay relative to the overlying Parent material influences on Luvisol Ae horizon, occurs primarily through genesis are evident in the broad the physical process of lessivage: geographical distribution of these dispersion of colloids in the upper soils. The largest continuous area of solum, downward transport in the soil Luvisols extends from central solution, and deposition of films of Saskatchewan through northern oriented clay on ped surfaces in the B Alberta, to northeastern British horizon. Field designation of Bt Columbia and extreme southeastern horizons relies heavily on recognition Yukon. These soils form on glacial of these illuvial clay skins, but these parent materials (usually till) derived features can disrupted by freeze-thaw from calcareous, finer-grained processes, and may be difficult to sedimentary rocks, which have distinguish from films created by the sufficient clay to enable Bt horizons to stresses of shrink-swell activity. In form. Luvisolic soils are largely absent situ weathering and formation of clay from the Canadian Shield, except can further augment the clay content where glaciolacustrine sediments of some B horizons, and the presence provide clay-rich parent materials, of lithological discontinuities within notably in northern Manitoba. In the solum can further complicate the British Columbia, Luvisolic soils interpretation of vertical textural predominate in the plateau landscapes gradients in some pedons. of the central and southern interior where medium-textured till deposits From a practical perspective in the are the most common parent material. field, soils that meet the textural

Figure 1.8: Distribution of Gray Luvisols in western Canada. Gray Brown Luvisols do not occur in western Canada. Plains. A similar climatic gradient is Transitions from Luvisolic to mirrored by elevational belts of soil Chernozemic soils occur with distribution in the major valleys of the progressively reduced moisture southern and central British Columbia availability southward in the Interior 28 interior, with Luvisolic soils occurring eluvial horizon to form Bm and then at the higher elevations above the Bf horizons, respectively. These forest-grassland transition. bisequa soils are common in the British Columbia central interior, with Thick (> 1 m), clay-enriched B Podzolic Gray Luvisols generally horizons can occur in soils formed on occurring in moister climates at older Pleistocene glacial landforms in higher elevations than the Brunisolic the west-central Yukon Territory. Clay Gray Luvisols. Brunisolic Gray films on coarse fragments can be Luvisols are also common in the easily recognized, but Ae horizons are Interior Plains. usually absent, and the taxonomic status and genetic pathway of these In some cases these bisequa soils form distinctive soils remain uncertain. where a sandy mantle overlies a till layer, and the Bm/Bf horizons form in the sandy mantle. In these cases the till layer is denoted with a Roman 1.5.4 Secondary Genetic Processes and numeral II (to indicate that a different the Subgroups of the Luvisolic Order parent material occurs) but the soil is Fourteen subgroups occur in the Gray still classified within the Luvisolic Luvisol great group, of which seven order. reflect the operation of gleying, as indicated by mottling in response to Solonetzic Gray Luvisols have Btnj fluctuating redox conditions, e.g. horizons, which differ from most Gray Gleyed, Gleyed Podzolic, Gleyed Dark Luvisol Bt horizons in having harder Gray etc. Unlike soils of the Gleysolic consistence, more pronounced ped order, these subgroups have distinct coatings, and a lower exchangeable (rather than prominent) mottles Ca:Na ratio. They are relatively within 50 cm of the mineral surface, or uncommon. prominent mottles at depths of 50-

100 cm. Vertic Gray Luvisols have a slickenside

horizon (Btss or Ckss) within 1 m of Eight subgroups include the the mineral soil surface, and may have identifiers Brunisolic, Podzolic, a weak vertic horizon (Btvj). Again, Solonetzic, or Vertic and represent these are relatively uncommon. transitions to other orders.

Dark Gray Luvisols have dark- The Brunisolic and Podzolic coloured Ah (or Ahe) horizons at least subgroups of Gray Luvisols have the 5 cm thick, and form part of the upper Bt horizon within 50 cm of the continuum between Chernozemic and mineral surface, and are examples of Luvisolic soils that has resulted from bisequa soils (i.e. those that exhibit the complex history of the forest- horizons from two distinct genetic grassland transition in the Prairie pathways). Their inferred genesis provinces. involves initial mobilization of clay to form Bt horizons, followed by further transformation of a portion of the 29

1.5.5 Human Impact on Luvisolic Soils the Prairie provinces. Unlike for the Luvisols occur over a large proportion more productive Chernozemic soils to of the managed forest land base of the south, agricultural management of western Canada, and require careful these soils can be limited by adverse soil conservation practices to sustain physical conditions (crusting), greater their productivity. In particular, the acidity, and lower organic matter and medium- to fine textures of these soils nutrient concentrations in Ap (former make them vulnerable to compaction Ae) horizons. In the British Columbia and puddling by ground-based central interior, till deposits tend to harvesting equipment when moisture have higher coarse fragment contents content is high and under unfrozen than in the Prairie provinces, so conditions. Displacement of surface agricultural development of Luvisols soil by harvesting or site preparation has been largely restricted to areas can result in restricted rooting depths with glaciolacustrine parent materials. where firm, coarsely structured Bt horizons are close to the mineral soil For further information see: surface. Lavkulich, L. M. and Arocena, J. M. 2011. Luvisols of Canada: Genesis, Clearing and cultivation of Luvisolic distribution, and classification. Can. J. soils have occurred on the northern Soil Sci. 91: 781_806. frontier of agricultural development in

The formation of Organic soils 1.6 The Organic Order transforms lowland landscapes through the processes of paludification and terrestrialization. 1.6.1 Introduction The former is more spatially The Organic order accommodates important, and involves both vertical soils formed primarily of materials accretion of organic materials under containing more than 17% organic conditions of limited decomposition, carbon (30% organic matter), and and lateral expansion of Sphagnum- form either in wetlands experiencing dominated wetlands. prolonged saturation, or on well- to Terrestrialization involves infilling of imperfectly drained upland sites depressional water bodies with where detritus from forest vegetation organic and inorganic materials to the is the main source of organic matter. point where water table conditions Distinguishing Organic soils from favour peat accumulation. those of other orders depends on Unlike the mineral soil orders, the detailed criteria for organic material Organic soils do not have a designated thickness and composition, as well as diagnostic horizon, beyond the depth to permafrost, if present. required carbon concentration and 1.6.2 Dominant Genetic Processes and minimum thickness of organic materials. The extent of humification Diagnostic Horizons of O horizons, increasing in the order The extent of accumulation of organic of Of (fibric), Om (mesic), and Oh matter represents the balance (humic), is tied directly to the between additions from detrital designation of great groups of wetland inputs and losses due primarily to Organic soils: Fibrisols, Mesisols, and oxidation (decomposition). Humisols, respectively. Conditions which depress decomposition consist of seasonally or 1.6.3 Distribution of Great Groups perennially high water tables, limited Only three of the Organic great groups oxygen supply, and cool soil have any appreciable abundance in temperatures. In upland settings, a western Canada (Fibrisol, Mesisol, cool, moist climate can enhance Folisol) (Figure 1.9). Humisols are organic matter accumulation in the largely absent except as a minor absence of saturation, in part by component of Columbia. Mesisols and suppressing forest fires which can be Fibrisols dominate poorly drained a major mechanism of organic matter boreal lowlands across a broad swath loss. In wetlands, organic matter is of central Manitoba and mostly derived from senescent Saskatchewan, northern Alberta, Sphagnum moss and feathermosses, northeastern British Columbia, and while forest litter, including woody the upper Mackenzie River valley of materials, is the major organic matter the Northwest Territories, with the source at upland sites. less humified Fibrisols increasing in relative 31

Figure 1.9: Distribution of Organic soils in western Canada.

1.6.5 Human Impact on Organic Soils abundance northward. This Artificial drainage of lowland Organic concentration of Organic soils in the soils for agricultural production in prairie provinces is bounded by the western Caanda has been limited to a grasslands to the south, and the few areas near large population southern edge of the Canadian Shield centres, such as in the lower Fraser to the north. Mesisols and Fibrisols River valley of southwestern British also occur as inclusions within the Columbia. Controlling accelerated rolling glaciated plateau landscape of oxidation of drained Organic soils the British Columbia central interior. requires careful water management to Folisols are confined to the wetter maintain this effectively non- climates of coastal British Columbia, renewable soil resource. Organic soils particularly on the northern mainland, of forested wetlands in the boreal and western Vancouver Island and region have not been artificially Haida Gwaii. drained as an operational forest management practice, however, 1.6.4 Secondary Genetic Processes and harvesting of stands on poorly drained the Subgroups of the Organic Order mineral soils may sufficiently alter the For the wetland Organic soils, the water balance that wetland expansion three great groups each have the same can occur through paludification. assemblages of subgroup Folisols in coastal British Columbia designations, and these recognize tend to support lower productivity differing proportions of fibric, mesic, forest stands, and have seldom and humic materials, mineral received intensive management due to sediment inputs (cumulic), underlying poor growth responses and difficulties mineral substrate (terric), water in regeneration. Where Folisols layers (hydric), and biologically- directly overlie bedrock, soil derived freshwater sediments displacement during harvesting or site (limnic). Unlike in the other orders, preparation, and high-impact these subgroup designations don’t broadcast burning need to be avoided. correspond to distinctive secondary genetic processes so much as they For further information see: capture distinct phases of wetland Kroetsch, D. J., Geng, X., Chang, S. X. evolution as recorded by parent and Saurette, D. D. 2011. Organic material properties. In the case of order - Part 1. Wetland Organic soils. upland Organic soils (Folisols), the Can. J. Soil Sci. 91: 807_822. subgroups indicate the degree of humification of the organic materials Fox, C. A. and Tarnocai, C. 2011. (as indicated by the dominant horizon Organic soils of Canada: Part 2. Upland type: F – Hemic; H – Humic), abundant Organic soils. Can. J. Soil Sci. 91: woody materials (Lignic), and 823_842. presence of underlying wetland peat materials (Histic).

diagnostic horizon. As recently 1.7 The Podzolic Order summarized by Sanborn et al. (2011), podzolization involves: (a) 1.7.1 Introduction acidification and enhanced weathering The strongly differentiated profiles of of primary minerals immediately Podzolic soils typically display a light- below the forest floor/mineral soil coloured eluvial horizon overlying a boundary through the formation and darker illuvial B horizon enriched in downward leaching of organic acids, aluminum and iron oxides and/or (b) release of iron and aluminum organic matter. These soils usually through in situ weathering in the B occur on medium- to coarse sand horizon, and their re-precipitation as textured acidic parent materials rich hydrous oxides, (c) accumulation of in quartz. Diversity in Podzolic soil materials translocated into the B morphology, such as the distinctness horizon and immobilized by pH- of the eluvial horizon and the related precipitation, microbial colouration of the B horizon, reflects activity, and adsorption, and (d) death the intensity of chemical weathering and decay of root detritus in situ, and translocation processes, as well as which augments organic matter pools the extent of organic matter and metal-binding capacity. accumulation in the mineral horizons. 1.7.2 Dominant Genetic Processes and 1.7.3 Distribution of Great Groups Diagnostic Horizons Although Podzolic soils are the 2nd The podzolic B horizon has the most most extensive soil order in Canada, intricate chemical and morphological their distribution in the western criteria of any of the diagnostic provinces is highly concentrated, mineral horizons. Subject to occupying almost one-third of British minimum thickness (10 cm) and Columbia but being largely absent colour requirements. Three varieties elsewhere except in some alpine and of podzolic B horizon categories subalpine areas of the Rocky reflect differences in the nature of Mountains in western Alberta (Figure illuvial constituents: primarily organic 1.10). The absence of Podzolic soils matter accumulation with low iron from the western boreal forest and concentrations (Bh), and iron and adjacent portions of the Canadian aluminum accumulation with either Shield is in strong contrast to their intermediate (0.5-5.0%; Bf) or high (> distribution in eastern Canada, 5%; Bhf) organic carbon reflecting the drier and colder concentrations. climates in forested areas of Manitoba, Saskatchewan, and Alberta. The combination of chemical and biological transformations of primary Within British Columbia, climatic minerals, organic matter, and zonation controls the broad secondary phases involved in Podzol distribution patterns of Humo-Ferric formation is collectively termed the vs. Ferro-Humic Podzols, with the podzolization process. Theories of latter being largely restricted to the podzolization must account for the wetter climates of the mainland coast, range of properties exhibited by this western Vancouver Island, and Haida 34

Gwaii, where soil organic matter areas of Ferro- accumulation is enhanced. Minor

Figure 1.10: Distribution of great groups of the Podzolic order in western Canada.

Humic Podzols also occur on the Clay translocation can be a significant windward slopes of the southern accessory process in Podzolic soils Rocky and Columbia Mountains. with medium- and finer-textured Organic carbon concentrations can parent materials, and is designated by exceed 10% in Ferro-Humic Podzols Luvisolic subgroups if the Bt horizon in coastal British Columbia, resulting occurs below 50 cm depth. These in masking of eluvial horizons. bisequa soils are part of a continuum Between the Coast and Rocky with Podzolic subgroups of Luvisolic Mountains, extensive areas of Humo- soils, and have been reported by soil Ferric Podzols occur in northern half surveys at scattered locations in of the interior plateau, while drier coastal and interior British Columbia. climates farther south are In situ organic matter accumulation in accompanied by a much greater the form of Ah horizons is recognized predominance of Luvisolic soils. by Sombric subgroups, and can occur in surprisingly diverse settings, Humic Podzols are much more ranging from grassy oak savannas of restricted in their distribution, and are southern Vancouver Island to lush found as a component of soil herbaceous subalpine meadows. landscapes only in the wettest hypermaritime areas of the outer Although Podzolic soils are usually coast. well-drained, given the importance of downward translocation of materials in the podzolization process, Gleyed 1.7.4 Secondary Genetic Processes and subgroups are designated in both the the Subgroups of the Podzolic Order Ferro-Humic and Humo-Ferric great Cementation takes several forms in groups where gley features such as Podzolic soils, especially in coastal mottling and grayish matrix colours British Columbia, and is designated by are present. Gleyed subgroups are not four subgroups of which only Duric , recognized in the Humic Podzols Ortstein, and Placic subgroups occur because these soils occur in wet sites to any significant degree. These and some degree of gleying is features can be important modifiers of regarded as an inherent property. soil hydrological behaviour, as well as providing restrictions to rooting 1.7.5 Human Impact on Podzolic Soils depth. Duric horizons are strongly Podzolic soils in western Canada are cemented, and are found below the influenced by human activity podzolic B horizon, with colours primarily through forest management, resembling those of the parent and have largely been unaffected by material. Orstein comprise strongly agriculture except in a few minor cemented zones within Bh, Bhf, or Bf areas of southern coastal British horizons. Placic horizons are thin (≤5 Columbia. Some of the most highly mm), hard, impervious and dark productive forest sites in Canada reddish brown to black, and can occur occur on Podzolic soils, and these have singly or in multiples within and/or tended to receive the most intensive below the podzolic B horizon. management, for example, as with Douglas-fir (Pseudotsuga menziesii) 36 plantations in southwestern British British Columbia remain largely Columbia. Elsewhere, Podzolic forest unaffected by anthropogenic acid soils in less productive climatic deposition, and in fact exhibit regimes are characterized by a less pronounced regional deficiencies of intensive style of management, with sulphur. conservation of existing site productivity during harvesting and For more information see Sanborn, P., site preparation receiving relatively L. Lamontagne, and W. Hendershot. more attention than practices 2011. Podzolic soils of Canada: intended to enhance productivity or Genesis, distribution, and shorten rotations. Unlike in eastern classification. Can. J. Soil Sci. 91: Canada, Podzolic soils in interior 843_880.

1.8 The Regosolic Order The Precambrian rocks of the Canadian Shield are very resistant to 1.8.1 Introduction both pulverization by glacial erosion Soils of the Regosolic order are at and weathering by pedogenic boundary between unaltered parent processes. Sediments in this region materials and soil – the alteration of are often dominated by weathering- the parent material is sufficient to resistant sand and gravel, and bare support plant growth but insufficient rock is commonly exposed at the to cause the formation of diagnostic surface. In either situation the imprint horizons associated with other orders. of pedogenesis is faint or essentially Because the alteration of parent absent, and soils are often classified as material is so limited the nature and Regosolic or Rock (a non-soil). The properties of the parent material has a Field Guide to the Substrates of major influence on the properties of Ontario (Ontario Ministry of Natural the Regosols. Resources, 2011) has a more

comprehensive approach to the Regosols occur due to five major description of these materials than the conditions: recent exposure, which CSSC. limits the time for soil formation; weathering-resistant parent material, Climate-induced Regosols also occur where the imprint of pedogenesis is in Arctic landscapes where arid greatly limited; arid or cold climates, conditions inhibit the formation of where the action of pedogenic Cryosolic soils. processes is limited; erosion of A and

B horizons, especially in agricultural Finally, in many wetlands in western fields, and discharge of solute-rich Canada water moves from the pond to water at the fringe of wetlands. the fringe of soil surrounding the

wetland due relatively impermeable Recent exposure occurs on recently underlying sediments. Capillary and deposited parent sediments such as transpiration processes draw this river floodplains, drained ponds, water to the soil surface where it is lakes, and swamps, beaches and lost to the atmosphere, and the solutes shorelines, mass wasting/movement in the water precipitate out. Because on slopes, volcanic eruption, and the direction of water movement is continental sand dunes. The latter vertically towards the surface it is represent the largest areal extent in difficult for a B horizon to form. These Prairie Canada in features such as the soils may have a thick Great Sand Hills in Saskatchewan and Ahca/Ahsa/Ahcasa directly overlying the Spirit Sand Hills in Manitoba. a Cca/Ccak/Ccasa etc. horizon. These Regosols are also very common on discharge soils were not well convex knolls and ridges in understood at the time of the hummocky, undulating, and rolling development of the CSSC, and are a agricultural landscapes, where problem soil for classification. truncation of the soil due primarily to tillage erosion has occurred. 38

1.8.2 Dominant Genetic Processes and Diagnostic Horizons Soils of the Regosol great group are Regosolic soils have undergone little the most common in western Canada pedogenic alteration. Although many (Figure pedogenic processes (e. g. decarbonation, podzolization) may be active, they have not left diagnostic 1.8.4 Secondary Genetic Processes and features in the soil. The diagnostic the Subgroups of the Regosolic Order: feature of the Regosols is either the complete lack of a B horizon or, if a B Soils of both great groups are further horizon is present, it must be less 5 cm subdivided into four subgroups: thick. Cumulic subgroup: Cumulic Regosols The most common process occurring usually develop from parent materials is melanization, the darkening of the deposited during intermittent floods surface horizon associated with the commonly within alluvial plains. accumulation of partially decayed During periods between flooding organic material in the profile. This there is sufficient time for the can lead to the presence of an Ah melanization process to be established horizon in undisturbed soils. In to develop Ah horizons. Commonly, truncated agricultural soils we can they have multiple Ah layers in their also find an Apk or Apca horizon profile representing periods between directly overlying the C horizon; sedimentation events by intermittent incorporation of carbonate into the C flooding. horizon occurs mixing of the upper soil through tillage. Gleyed subgroup: Gleyed subgroups have a horizon with a gj suffix 1.8.3 Distribution of Great Groups (indicating faint to distinct mottles) Soils of the Regosolic Order occur in within 50 cm of the surface. Both one of two great groups: Regosol and Gleyed and Gleyed Cumulic subgroups Humic Regosol. Soils of the Regosol occur. great group either lack an Ah horizon or have Ah horizons less than 10 cm Orthic subgroup: The Orthic subgroups thick, whereas Humic Regosols meets the criteria of the Regosolic contain Ah horizons at least 10 cm in order but lacks any cumulic or gleyed thickness. These Ah horizons do not, features. however, meet the additional criteria required for the Chernozemic A horizon. 39

Figure 1.11: Distribution of Regosolic soils in western Canada

and the creation of Regosolic soils. 1.8.5 Human Impact on Regosolic Soils This is most common in agricultural Destabilization of the surface by landscapes where tillage erosion (and human activity can result in the to a lesser extent wind and water truncation of the surface soil horizon erosion) cause progressive 40

incorporation of the A and B horizons Ontario Ministry of Natural Resources. into the underlying C horizon. As well, 2011. Field Guide to the Substrates of destabilization of dune areas may Ontario. pp. 76 . cause loss of soil through wind erosion and Regosolic soils to occur. VandenBygaart, A. J. 2011. Regosolic soils of Canada: Genesis, distribution, For further information see: and classification. Canadian Journal of Soil Science 91:881-887.

drainage and that are adjacent to 1.9 The Solonetzic Order upland areas.

1.9.2 Dominant Genetic Processes and 1.9.1 Introduction: Diagnostic Horizons In Canada, Solonetzic or sodic soils are Solonetzic soils are thought to develop found only in the western provinces, via the stepwise pedogenic processes and are characterized by Bn or Bnt of salinization, solonization horizons with high exchangeable Na, (desalinization and alkalization), and prismatic or columnar structure with solodization (Figure 2). Salinization is dark coatings on peds, and hard to the process by which soluble salts very hard consistence when dry (Soil accumulate at or near the landscape Classification Working Group 1998). surface by evapotranspiration. To The unique physical initiate Solonetzic genesis in the and chemical properties of Solonetzic western Canadian landscapes, a soils often limits crop production and dominance of sodium salts must be cause problems with other land uses concentrated and maintained at the such as metal corrosion, cement soil surface or within the upper foundations and section of the soil by a shallow water road construction. The interaction of table or groundwater discharge . saline and sodic parent material, low relief, groundwater discharge of saline Soluble salts move upward to the soil groundwater and shallow water surface during soil salinization. Less tables, high evapotranspiration, and soluble evaporate minerals such as grasses and forbs over time has likely calcite and gypsum precipitate in the contributed to the genesis of subsoil, whereas more soluble Na-Mg- Solonetzic soils within areas generally SO4 evaporate minerals precipitate dominated by Chernozemic soils. on the soil surface as efflorescence or white salt crusts. The sequence of Solonetzic soils are found where there preferential mineral precipitation in is thin layer glacial material overlying saline soils results in the high shallow bedrock composed of saline concentrations of Na and SO4 salts in and alkaline marine shales. High salt the upper soil, and these salts are concentrations in glacial sediments required to initiate solonization. may be related to the shallow underlying marine bedrock and For solonization to proceed from groundwater discharge. Solonetzic salinization (Fig. 2), three conditions soils generally occur on topographic must be met: (1) gradual relief that is level to undulating, desalinization must occur to lower the especially on lowlands with restricted total concentration of soluble 42

Figure 1.12: Distribution of great groups of the Solonetzic order in western Canada. salts, which initiates alkalization or exchange complex of clay minerals; accumulation of Na ions on the (2) there must be a high concentration 43

of Na ions to initiate alkalization; and wetting and drying forming prismatic (3) there must be significant structure, and eluviation of soil expandable clay minerals to initiate material from the top corners of the clay dispersion. Desalinization is prisms results in the rounded tops or thought to have occurred in the columnar shape. Interior Plains because a change in climate (increased precipitation) and Sufficient dispersed clay eventually lower water tables resulted in eluviates from the A to the B horizon leaching of soluble salts or to form a dense and impermeable Bnt desalinization. The action of these horizon. Weathering of the upper soil processes results in the formation of a profile results in a mildly weathered Bn horizon, diagnostic of the Solonetz and acidic A horizon (Ae) overlying a Great Group. The unique columnar dense Na-dominated B horizon. This structure of the Solonetzic Bn horizon process is called solodization. likely develops from a combination of

Figure 1.13. Major genetic or pedogenic processes in the genesis of Solonetzic soils in Canada (modified after Pawluk 1982).

The eluvial Ae horizon has a coarse results in the formation of a texture, platy structure, and an ashy transitional AB or BA horizon. gray color that is indicative of strong weathering conditions and eluviation. Further weathering of the upper B 44

1.9.3 Distribution of Great Groups becomes less dominant moving The Solonetzic Order includes four upslope. great groups: Solonetz, Solodized Solonetz, Solod, and Vertic Solonetz. In the second sequence, Solods are All great groups have the diagnostic found in the lowest topographic Bn or Bnt horizon. The great groups position, while Solodized Solonetz, are separated based on the presence Solonetz and Chernozems are found at of and thickness of the Ae horizon, the progressively higher slope positions. breakdown of the upper part of the Bn This catenary sequence has been or Bnt horizon, and the occurrence of described for soils in Saskatchewan . vertic features. The Solonetz great Surface runoff occurs from the upper group does not have an Ae horizon to lower slope positions, and a deep that is continuous and ≥ 2 cm. The water table and groundwater recharge Solodized Solonetz great group has an at the lowest slope position allows Ae ≥ 2 cm thick, and an intact, leaching of soluble salts to occur in the columnar Bnt or Bn horizon. The Solod. Solod great group have an Ae ≥ 2 cm thick, a distinct AB or BA horizon 1.9.4 Secondary Genetic Processes and (from disintegration of top of Bnt), the Subgroups of the Solonetzic Order and a Solonetzic B horizon. The Vertic Solonetz great group has any features Colour subgroups: The most common of the previous three great groups, of the subgroups of the Solonetzic and the presence of a slickenside soils correspond to the soil zones that horizon whose upper boundary is are characteristic of the great groups within 1 m of the mineral soil surface. of the Chernozemic order, and the criteria for placement of the soils into The great groups of the Solonetzic subgroups are the same as for the order do not exhibit the type of Chernozemic order (table X). regional zonation seen in the

Chernozemic order. Indeed often two Gleyed subgroups: Both the Gleyed or even three great groups can be Solonetzic subgroups and soils of the found in a single hillslope catena. Two Gleysolic order have mottles resulting common Solonetzic catenas are found from alternating reduction-oxidation in the prairies. In the first sequence, conditions caused by periodic water Gleyed Solonetz or Solonetz occur in saturation. The key distinction is the the depressional areas of the colour contrast of mottles: Gleyed landscape, and soils then grade Solonetzic subgroups have faint or through Solodized Solonetz, Solods, distinct mottles within 50 cm of the and in some cases, Chernozems at surface (indicated by a gj horizon), higher elevations. The depressions are whereas soils of the Gleysolic Order typically areas with shallow water have prominent mottles within 50 cm tables and groundwater discharge that (a g horizon). The Gleyed identifier is bring soluble salts upward into the also added to other subgroup soil solum, and the groundwater effect identifiers for Solonetzic soils (e.g. 45

Gleyed Brown, Gleyed Dark Brown, Gleyed Dark Gray etc.)

Subgroup Solonetz Solodized Solod Vertic Criteria (Colours for A Solonetz Solonetz horizon and dry samples) Alkaline Present Alkaline A with pH ≥ 8.5 Brown Present Present Present Present Color value > 4.5, chroma > 1.5 or exposed Solonetzic B Dark Present Present Present Present Color value 3.5—4.5, Brown chroma > 1.5 or exposed Solonetzic B Black Present Present Present Present Color value < 3.5, chroma < 2 Dark Gray Present Present Color value 3.5—4.5, chroma <2 Gray Present Present Color value >4.5, chroma <2 Gleyed + Present Present Present Present Horizon with gj suffix + Colour colour criteria

Table 1.1: Subgroups and associated criteria for soils of the Solonetzic order

Saline soils: Saline soils in Canada are currently 1.9.5 Human Impact on Solonetzic Soils classified as a phase of other soil The sharp textural contrast between orders such as Chernozemic, the coarser A horizons and the fine- Gleysolic, Regosolic, or Solonetzic. To textured B horizon makes Solonetzic qualify as a saline phase (e.g., saline soils particularly vulnerable to soil Calcareous Dark Brown Chernozem), erosion, especially by wind. Large the soil horizon should have a ‘‘sa’’ areas of Solonetzic soils experienced suffix (e.g., Bmksa) in the A or B significant loss of A horizons due to horizon. The ‘‘sa’’ horizon has a wind erosion in the 1930s, and the secondary enrichment of soluble salts Solonetzic B is exposed at the soil more soluble than Ca and Mg surface. This is most common in soils carbonates (e.g., gypsum), the in the Brown soil zone, and to a lesser conductivity (EC) of the saturation degree those in the Dark Brown zone. extract must be ≥ 4 dS m-1 , and the EC For further information see: must exceed that of the C horizon by Miller, J.J. and J. A. Brierley. 2011. at least one-third. Solonetzic soils of Canada: Genesis, distribution, and classification. Canadian Journal of Soil Science 91:889-902. 46

of other orders (e.g. Vertic Dark 1.10 The Vertisolic Order Brown Chernozem).

1.10.1 Introduction 1.10.2 Dominant Genetic Processes and Vertisolic soils are the product of Diagnostic Horizons contraction and expansion of the soil Upon drying of a clayey soil mass mass and the resulting self-mulching (high in 2:1 smectitic clay minerals), (churning and mixing) of the soil surface cracks develop due to material. In Canada, these processes shrinkage. These surface cracks occur where the clay content of the become a zone of weakness within the parent material exceeds 60%, and the soil mass, and these cracks tend to fine earth (< 2 mm) fraction is repeatedly close and re-open with dominated by 2:1 smectitic (swelling) reoccurring wetting and drying cycles. clay minerals. When the cracks are open material from the surrounding soil surface falls Vertisols occur on level to gently into the cracks. The presence of this inclined and undulating landscapes of sloughed-in (infill) material provides glaciolacustrine or glaciomarine preferential areas or zones of origin. In conjunction with these weakness within the soil mass. Over essential parent material time, the original cracks grow in both characteristics, the climate where depth and width. The product of this Vertisolic soils occur must be dry cyclical drying and wetting is the enough to create fluctuations in soil formation of wedge-shaped features moisture content that cause defined within the soil profile. Since the wetting and drying cycles. These three content of the wedge generally essential components are required for consists of organic rich soil that is the formation of Vertisolic soils as darker-coloured and lighter-textured recognized within the Canadian soil material than the subsoil, these System of Soil Classification. features are easily recognizable.

Vertisolic soils are difficult to describe During the periods of re-saturation of because the B horizon is often not the clayey material internal pressures apparent; horizons are disrupted by increase as the clay expands, due to turbation, so boundaries can be tilted the hydration of the 2:1 silicate clay and in some cases almost vertical. minerals. Internal swelling pressures These turbated horizons are assigned are relieved by oblique and upward a v suffix in the CSSC. As well, movement of areas adjacent to the displacement of peds along each other infilled cracks. With increasing depth, creates polished ped surfaces at depth, the mass of soil increases and which are termed slickensides (ss therefore the resistance to swelling suffix). The presence of both the vertic commensurately increases. When horizon and slickensides is required swelling pressures exceed resistance, for placement into the Vertisolic or shear strength of the soil, failure order; soils that lack one of the occurs along internal planes of features are classified as intergrades weakness. Well-developed shear planes are referred to as slickensides 47

and typically occur at depths between and, hence, the surface horizons are 50 and 125 cm. When a block of soil very similar in color to the underlying moves due to shear failure, multiple horizons. The dry colour value of the shear planes may be associated with surface A horizon is greater than 3.5 the block. This internal movement can and the chroma is usually greater than occur in multiple directions, so 1.5. ultimately shear planes intersect producing slickensides. The resulting Humic Vertisols are associated with network of intersecting shear planes the moister areas of the Prairie or slickensides forms the boundaries ecozone. The surface A horizons of of internal wedge-shaped structures. native profiles contain more than 3% organic carbon (Soil Classification The diagnostic horizons of the Working Group 1998), reflecting the Vertisolic order result from these climatic characteristics of the Moist processes. The slickenside (ss) Mixed grassland and Lake Manitoba horizon has two or more slickensides, Plain ecoregions (Ecological often with unidirectional grooves Stratification parallel to the direction of soil Working Group 1995). As a general displacement cut into their shiny rule, Vertisolic soils of this great group surfaces. The vertic (v suffix) horizons occur within the Dark Brown and are characterized by irregular shaped, drier portions of the Black soil zones. randomly orientated, intrusions of The chroma and value of the A horizon displaced materials within the and is less than 3.5 and 1.5, respectively. wedge-shaped features extending from the surface resulting from the Vertisolic soils were not mapped in infilling of cracks over time. The British Columbia, but some soils combination of these features results developed on fine-textured parent in the apparent homogenization of the materials in the Okanagan Valley and soil materials and so the development interior plateau are either vertic of diagnostic horizons associated with intergrades of other orders or true other orders is impeded. Both the Vertisolic soils/ vertic and slickenside horizons must be present for classification into the 1.10.4 Secondary Genetic Processes and Vertisolic order. the Subgroups of the Vertisolic Order: Each Vertisolic soil great group 1.10.3 Distribution of Great Groups contains three subgroups: Orthic, Two great groups are recognized Gleyed and Gleysolic. Classification to within the Vertisolic order: the this level is based on the presence of Vertisol and Humic Vertisol. Soils of mottles (reflecting the duration of soil the Vertisol great group are associated saturation) within the upper 50 cm of with the arid portions of the Prairie the surface. The Orthic subgroups are ecozone, specifically the Mixed defined as having no mottles within Grassland ecoregion and the Brown 50 cm of the surface. Gleyed soil zone . The organic carbon content subgroups have faint and distinct of native surface horizons of the mottles within this depth, while Vertisol great group is less than 3% Gleysolic subgroups are poorly 48 drained, and prominent mottles occur within the upper 50 cm

Figure 1.14: Distribution of great groups of the Vertisolic order in western Canada.

of the surface. The Gleysolic subgroup the permanence of rigid structures. is an anomaly in the CSSC; normally Potential cracking of building soils with prominent mottles in the foundations, roads and sidewalks and upper 50 cm are classified into the subsidence of earthen structures are Gleysolic order. common issues that need to be addressed when constructing on 1.10.5 Human Impact on Vertisolic Soils Vertisolic soils. Vertisolic soils are excellent soils for agricultural production and have been For further information see: almost entirely converted to agricultural production. Although Brierley, J. A., H.B. Stonehouse, and these soils are inherently fertile, they A.R. Mermut. 2011. Vertisolic soils of are susceptible to compaction if too Canada: Genesis, distribution, and wet and are difficult to cultivate, and classification. Canadian Journal of Soil are susceptible to clodding when too Science 91:719-747. dry. As well, the high shrink-swell potential of clay-textured materials causes problems for construction and