This major grouping occupies 16.28 million ha, or 1.0% of the land area of Russia (Table 5.1). It is common in the Kamchatka peninsula (Figure 6.1).
Andosols are formed from materials rich in volcanic glass and commonly have a dark surface horizon. They show andic properties to a depth of 35 cm or more from the surface and have a mollic or umbric A horizon that possibly overlies a cambic B horizon, or an ochric A horizon and a cambic B horizon. They have no other diagnostic horizons and they lack gleyic properties within 50 cm of the surface, all characteristics diagnostic for Vertisols, and salic properties.
The soils are subdivided into zones according to the frequency and intensity of deposition of the ash. Intensely active zones have frequent deposition and the soil consists of thin layers of fresh ash with some organic material. Moderately active zones have somewhat developed profiles with a thick humus horizon and weathering features. Slightly active means that ash falls are rare, the minerals are well-weathered, and horizons are well-developed.
The term ochre and ochric, used in the description of these soils, has the spe-cific meaning of having an f(Bf) horizon or well-weathered properties with clay formation and abundant SiO2and R2O3.
The following FAO soil units are recognized with their corresponding soil groups in SMR.
• Andosols Haplic (ANh) – Volcanics ochre-banded – Volcanics dry-peaty
– Volcanics light-ochre (including podzolized) – Volcanics ochre (including podzolized) – Volcanics podzolized-ochre
• Andosols Vitric (ANz) – Volcanics banded-ash
• Andosols Gelic (ANi)
– Volcanics illuvial-humic tundra
Legend:
Dominant component Associated and included components Others
Water
(d) Leptosols
(e) Arenosols
(f) Andosols
Figure 6.1. Major soil groupings of Russia: (d) Leptosols, (e) Arenosols, and (f) Andosols.
6.6.1 Andosols Haplic (ANh)
This soil unit occupies 11.18 million ha, which corresponds to 0.7% of the land area, or 68.7% of the Andosols major soil grouping.
These soils have an ochric A horizon and a cambic B horizon, with a smeary consistency and a texture that is silt loam or finer on the weighted average for all horizons within 100 cm of the surface; they do not have gleyic properties within 100 cm of the surface or permafrost within 200 cm of the surface.
This soil unit correlates with Volcanics ochre-banded, Volcanics dry-peaty, Vol-canics light-ochre (including podzolized), VolVol-canics ochre (including podzolized), and Volcanics podzolized-ochre.
Volcanics ochre-banded soils have a composite poligenetic soil profile, con-sisting of between four and 10 simple subprofiles (120–180-cm-thick altogether) developed on volcanic ash. All of them have organic and illuvial-weathered hori-zons. The organic horizons become weaker downward while the illuvial-weathered features become stronger. The lowest horizons have an ochre color and properties of ochre horizons in the subsoil. These soils develop in volcanic ash deposits under forest vegetation on the Kamchatka peninsula.
Volcanics dry-peaty soils have composite poligenetic soil profiles, consisting of several young, undeveloped profiles. Peaty organic and brown illuvial-humus horizons exist in every profile. The most recent organic horizon is dry peaty (15–
25 cm). Such soils are acid and base-unsaturated. They occur under dwarf pine vegetation of the Kamchatka peninsula on moderately active volcanic ash deposited as volcanic sands and ashes falling from the air.
Volcanics light-ochre (including podzolized) soils have the profile O-AO-A2-Bf,h (Bh)-C. They are characterized by a buried humus horizon with amorphous SiO2and R2O3in transitional horizons. These soils are formed in the central Kam-chatka depression under grassy birch forests.
Volcanics ochre (including podzolized) soils differ from typical ochre Volcanic ones by the presence of a 3–6-cm-thick, loose A2 horizon, which is composed of a light grey-colored (in some places bleached), loamy sand or sandy loam, and formed under forest litter or a raw humus horizon. They are composed of organic debris and volcanic ash particles bleached from the surface down. These soils occur in a moderately active volcanic ash deposition zone under grassy stone-birch forests on the Kamchatka peninsula.
Volcanics podzolized-ochre soils have a soil profile close to that of illuvial-humus podzols. They have a very bright colored B horizon and a buried illuvial-humus horizon (or its fragments) with a very high humus and amorphous SiO2 and R2O3
content in the lower horizons. The soil profile is developed on aeolian volcanic material. Secondary minerals are represented by allophane and amorphous organo-mineral compounds.
These soils are formed in the slightly active, shallow volcanic ash deposition zone under grassy birch forests on the Kamchatka peninsula.
6.6.2 Andosols Vitric (ANz)
This soil unit occupies 2.73 million ha, which corresponds to 0.2% of the land area of the country, or 16.8% of the Andosols major soil grouping area. They are characterized by lacking a smeary consistency or by having a texture that is coarser than silt loam on the weighted average for all horizons within 100 cm of the surface, or both; they do not have gleyic properties within 100 cm of the surface or permafrost within 200 cm of the surface.
This soil unit correlates to Volcanic banded-ash soils.
Volcanics banded-ash soils have profiles that consist of many superimposed profiles (usually 10–15). Each original profile has a raw humus organic horizon and a layer of volcanic ash only slightly changed by pedogenesis or weathering.
The soil reaction is acid or slightly acid. Humus content, cation exchange capacity, and other properties depend very much on the properties of the individual layers.
These soils occur in an intensely volcanic ash deposition zone under coniferous and birch forests on the Kamchatka peninsula.
6.6.3 Andosols Gelic (ANi)
This soil unit occupies 1.73 million ha, which corresponds to 0.1% of the land area of the country, or 10.6% of the Andosols major soil grouping area. Permafrost exists within 200 cm of the surface; this corresponds to Volcanic illuvial-humus tundra soils.
Volcanics illuvial-humic tundra soils have a three-dimensional, anisotropic pro-file. They are formed in conditions of frost mound relief. No horizons are recog-nized other than recent peaty-mud and buried peaty horizons (usually two). The latter are folded and torn by cryogenic processes. These soils are acid and charac-terized by the high content of eluviated humus and amorphous sesquoxides. They are formed in areas of volcanic deposits in a moderately active volcanic ash depo-sition zone under tundra vegetation, on the Kamchatka peninsula.