13. Icelandic soils

Abstract

Most Icelandic soils form in volcanic parent materials. The majority of the soils are classified as Andosols or Vitrisols according to an Icelandic soil classification scheme. Drainage and eolian deposition play a major role in soil formation in Iceland in addition to periodic tephra deposition. Wetlands cover about 23,000 km 2 , but organic Histosols only about 1,300 km 2 . This limited extent of Histosols results from rapid eolian and tephra deposition that reduces the organic content of the soils. The Andosols are dominated by allophane and ferrihydrite clays and Al/Fe-humus complexes, which give the soils typical Andosol properties such as low bulk density, high water retention and hydraulic conductivity and P-retention. The various types of Andosols comprise about 48% of Icelandic soils. The Vitrisols are soils of the deserts. Some of the Vitrisols have considerable allophane contents and much of the Vitrisols are classified as Andisols according to Soil Taxonomy. They cover >30% of Icelandic soil surfaces. Cryoturbation is intense in Iceland because of frequent freeze-thaw cycles, mild winters, a large amount of available water and the nature of the soils. Soil erosion is intense in Iceland and has caused large-scale environmental change over the past 1–2 k yrs. Determination of eolian deposition between tephra layers of known age has been used extensively to theorize about environmental change during the Holocene. Soil properties, such as organic content and clay minerals, of current and past soil surfaces, can be used to draw conclusions about past environments in Iceland.