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GLOBAL SOIL PATTERNS

 

A. INTRODUCTION link: text note link: global soil moisture regions map link: global soil orders map link: climate map north america

B. OXISOLS link: text note link: global distribution of oxisols

  • Climate: hot & humid; tropical rainy (Af & Aw)

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

  • Location: equatorial Africa & South America

  • Very highly weathered

  • Horizons not very distinctive

  • Silica and nutrients leached from soil

  • Organic/nutrient poor; low CEC

  • 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

C. ULTISOLS link: text note link: global distribution of ultisols

  • Climate: hot to temperate & humid; tropical rainforest (Af) & humid subtropical (Cfa)

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

  • Location: equatorial Africa & South America, southeastern USA

  • Similar to oxisols, but not as highly weathered

  • 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

D. ALFISOLS link: text note link: global distribution of alfisols

  • Climate: hot to temperate & humid to subhumid; tropical wet & dry (Aw), 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

E. SPODOSOLS link: text note link: global distributino of spodosols

  • Climate: cool & humid; humid continental (Dfb, Dfc) although they can occur in other climates

  • Vegetation: needleleaf forest

  • Location: New England

  • Thick, acidic O horizon

  • 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

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

  • Climate: cold; humid subarctic (Dfc, Dfd, Dw)

  • Vegetation: low-growing plants

  • 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

G. MOLLISOLS link: text note link: global distribution of mollisols

  • Climate: temperate to cool & subhumid to steppe; Cfa, Dfa, Dfb, 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

H. ARIDISOLS link: text note link: global distribution of aridisols

  • Climate: dry; subtropical desert (BWh) and 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

I. ENTISOLS & INCEPTISOLS

  • Climate: varies

  • Vegetation: varies

  • Location: widespread

  • Little horizon development

    • insufficient time

    • highly resistant parent material

    • active environments

 photo: entisol profile

J. HISTOSOLS Picture (34x28, 1.2Kb) link: global distribution of histosols

  • Climate: varies; cool humid

  • Vegetation: water tolerant

  • Location: waterlogged environments such as bogs; most commonly in subarctic & arctic locations

  • Organic soils

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

 photo: histosol profile

K. VERTISOLS link: text note link: vertisol landscape

  • Climate: varies, but most well developed in climates with a seasonal moisture regime

  • Vegetation: varies

  • Location: places with expansive clays (clays that swell & shrink with wetting & drying)

  • Profile inversion due to mixing as cracks open & close

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

 photo: vertisol profile

L. ANDISOLS link: text note link: global distribution of andisols

  • Climate: varies

  • Vegetation: varies

  • Location: volcanic regions

  • Parent material: volcanic ash & pyroclasts

  • Rich in humus

 

  

M. SUMMARY

Soil orders associated with climates:

  • oxisols - Af, Aw

  • ultisols - Af, Aw, Cfa

  • alfisols - Aw, Cs, Cfa, Dfa, Dfb,

  • spodosols - Dfb, Dfc (& needleleaf forests)

  • gelisols - Dfc, Dfd, Dw (permafrost)

  • mollisols - Cfa, Dfa, Dfb, BSk

  • aridisols - BWh, BWk

Soil orders associated with special conditions:

  • spodosols - needleleaf forests

  • gelisols - permafrost

  • entisols & inceptisols - active environments; young soils

  • histosols - bogs

  • vertisols - expansive clay parent material

  • andisols - volcanic parent material

 

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© Karen A. Lemke: klemke@uwsp.edu
Last revised March 15, 2007