| Umbrisol | |
|---|---|
 a Umbrisol profile | |
| Used in | WRB |
| WRB code | UM |
| Profile | A(B)C |
| Parent material | Weatheredsilicic rock |
| Climate | Oceanic, other |
Insoil classification, anUmbrisol is a soil with a darktopsoil and in whichorganic matter has accumulated within the mineral surface soil—in most cases with lowbase saturation—to the extent that it significantly affects the behaviour and utilization of the soil. Umbrisols are the counterpart of comparable soils with a high base saturation (Chernozems,Kastanozems andPhaeozems).
Umbrisols develop inweathering material ofsiliceous rock.[citation needed] They are found in mostly cool humidclimates inmountainous regions with little or nomoisture deficit, including tropical and subtropical mountains.
Many Umbrisols are under a natural or near-naturalvegetation cover. Umbrisols occur above the actual tree line in theAndean,Himalayan andCentral Asian mountain ranges; they are at lower altitudes in northern and westernEurope where the formerforest vegetation has been largely cleared, carry a vegetation of shortgrasses of low nutritional value.Coniferous forest predominates inBrazil (and in theUnited States). Umbrisols in tropical mountain areas inSouth Asia andOceania are under montane evergreen forest. In the mountains of southernMexico, the vegetation varies from tropical semi-deciduous forest to much cooler montanecloud forest.
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The predominance of sloping land and wet and cool climate conditions restricts utilization of many Umbrisols to extensivegrazing. Management focuses on the introduction of improved grasses and correction of thesoil pH by liming. Many Umbrisols are susceptible toerosion. The planting ofperennial crops and bench or contour terracing offer possibilities for permanent agriculture on gentler slopes. Where conditions are suitable, cash crops may be grown, e.g.cereals and root crops in the US, Europe andSouth America, ortea andcinchona inIndonesia. Highlandcoffee on Umbrisols demands high management inputs to meet its stringent nutrient requirements. InNew Zealand, Umbrisols have been transformed into highly productive soils, used for intensivesheep anddairy farming, and production of cash crops.
Umbrisols occupy about 100,000,000 hectares (250,000,000 acres) throughout the world. In South America, Umbrisols are common in the Andean ranges ofColombia,Ecuador,Venezuela,Bolivia andPeru. They also occur in Brazil, inLesotho and inSouth Africa. Umbrisols in North America are confined largely to the northwestPacific seaboard. In Europe, Umbrisols occur along the northwestAtlantic seaboard, e.g. inIceland, on theBritish Isles and in northwestPortugal andSpain. In Asia, they are found in the mountain ranges east and west ofLake Baikal, and on fringes of the Himalayas, notably inIndia,Nepal,China andBurma. Umbrisols occur at lower altitudes in easternIndia, in Burma and inSumatra. InOceania, Umbrisols are found in the mountain ranges ofPapua New Guinea and southeastAustralia and in the eastern parts ofSouth Island, New Zealand.
"Umbrisol" is a Reference Soil Group of theWorld Reference Base for Soil Resources (WRB).[1]
Many of such soils are classified in theUSDA soil taxonomy asGreat Groups ofEntisols andInceptisols, and as "Very dark-humus soils" in theRussiansoil classification.
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