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    GLOBAL SOIL PATTERNS

A. INTRODUCTION link: text note link: soils map north america Link: climate map North America

global soils map

 

B. HUMID CLIMATE SOILS: Oxisols, Ultisols, Alfisols

OXISOLS link: text note link: global distribution of oxisols

  • Climate: tropical rainforest (Af) [tropical wet and dry (Aw)]

  • Vegetation: tropical forest (broadleaf evergreen & tropical semi-deciduous)

  • Location: tropics and subtropics

  • Very highly weathered; clay rich; nutrient poor

  • Horizons not very distinctive

  • Rich in aluminum & iron; formation of laterite

Image credit:U.S. Department of Agriculture, Natural Resources Conservation Service, http://soils.usda.gov/technical/classification/orders/oxisols.html

 photo: oxisol profile

ULTISOLS link: text note link: global distribution of ultisols

  • Climate: humid subtropical (Cfa) [tropical rainforest (Af), tropical wet and dry (Aw)]

  • Vegetation: tropical & temperate forests (broadleaf evergreen & broadleaf deciduous)

  • Location: equatorial Africa & South America, southeastern USA

  • Similar to oxisols, but not as highly weathered or as nutrient poor

  • Nutrient poor; clay-rich; iron and aluminum rich

  • Horizons more distinctive than oxisols

Image credit:U.S. Department of Agriculture, Natural Resources Conservation Service, http://soils.usda.gov/technical/classification/orders/ultisols.html

 photo: ultisol profile

ALFISOLS link: text note link: global distribution of alfisols

  • Climate: tropical wet & dry (Aw), Mediterranean or dry summer subtropical (Cs), humid subtropical (Cfa), humid continental (Dfa, Dfb)

  • Vegetation: temperate forest (broadleaf deciduous)

  • Location: southern Great Lakes south to the Gulf of Mexico

  • Moderately leached; relatively fertile

  • Thin O horizon; A horizon more well-developed than in ultisols

  • Eluviation of clay from A & E horizons

  • Illuviation of clay in B horizon

photo credit: http://soils.usda.gov/technical/classification/orders/alfisols.html replace

photo: alfisol profile

C. COLD CLIMATE SOILS: Spodosols, Gelisols

SPODOSOLS link: text note link: global distributino of spodosols

  • Climate: cool humid continental (Dfb, Dfc)

  • Vegetation: needleleaf forest (acid forest soil)

  • Location: New England, northern Great Lakes

  • Thick, acidic O horizon; sandy

  • Thin A horizon

  • Sandy, ash-grey E horizon

  • Clay & iron rich, red B horizon

photo credit: http://soils.usda.gov/technical/classification/orders/spodosols.html

photo: spodosol profile

GELISOLS link: text note link: permafrost landscape link: global distribution of gelisols

  • Climate: tundra (ET) [cold humid continental (Dfc), subarctic (Dw)]

  • Vegetation: low-growing plants; tundra vegetation

  • Location: high latitudes

  • Permafrost

  • Dark A horizon due to presence of decaying plant litter

  • Cryoturbation: vertical mixing due to freeze-thaw

photo credit: http://soils.usda.gov/technical/classification/orders/gelisols.html

 photo: gelisol profile

D. DRY CLIMATE SOILS: Mollisols, Aridisols

MOLLISOLS link: text note link: global distribution of mollisols

  • Climate: subhumid humid subtropical (Cfa), subhumid humid continental (Dfa, Dfb), midlatitude steppe (BSk)

  • Vegetation: prairie grassland

  • Location: midlatitudes; central USA from Texas to Canada & on into Canada

  • Thick, organic rich A horizon

  • Not leached of nutrients

  • Formation of calcium carbonate in B horizon

photo credit: http://soils.usda.gov/technical/classification/orders/mollisols.html

photo: mollisol profile

ARIDISOLS link: text note link: global distribution of aridisols

  • Climate: subtropical desert (BWh), midlatitude desert (BWk)

  • Vegetation: desert vegetation

  • Location: subtropics, leeward side of mountains, continental interiors, dry west-coasts

  • Weak A horizon

  • Minimally weathered

  • Minimally leached

  • Accumulation of salts

photo credit: http://soils.usda.gov/technical/classification/orders/aridisols.html

 photo: aridisol profile

E. SOILS WITH POORLY DEVELOPED HORIZONS: Entisols, Inceptisols

  • Location: widespread

  • Little horizon development

    • insufficient time

    • highly resistant parent material

    • active environments

 photo: entisol profile

F. LOCALIZED SOILS: Histosols, Vertisols, Andisols

HISTOSOLS: bog soils
 Picture (34x28, 1.2Kb) link: global distribution of histosols

  • waterlogged environments such as bogs

  • cold humid continental (Dfc)

  • high percent organic matter

photo: histosol profile

photo credit: http://soils.usda.gov/technical/classification/orders/histosols.html

VERTISOLS: expansive soils
link: text note link: vertisol landscape

  • parent material: expansive clays

  • most well-developed in climates with a seasonal moisture regime

  • profile inversion due to mixing as cracks open & close

photo: vertisol profile

photo credit: http://soils.usda.gov/technical/classification/orders/vertisols.html

ANDISOLS: volcanic soils
link: text note link: global distribution of andisols

  • parent material: volcanic ash & pyroclasts

  • rich in humus

 

G. SUMMARY

Soil orders associated with climates:

  • oxisols - Af [Aw]

  • ultisols - Cfa [Af, Aw]

  • alfisols - Aw, Cs, Cfa, Dfa, Dfb,

  • spodosols - Dfb, Dfc (& needleleaf forests)

  • gelisols - ET [Dfc, Dw]

  • mollisols - Cfa, Dfa, Dfb, BSk

  • aridisols - BWh, BWk

Soil orders associated with special conditions:

  • spodosols - needleleaf forests

  • gelisols - permafrost

  • entisols & inceptisols - poor horizonation

  • histosols - bogs

  • vertisols - expansive clay parent material

  • andisols - volcanic parent material

 
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©Karen A. Lemke: klemke@uwsp.edu
Last revised November 2, 2009