World’s Soil Resources

UMBRISOLS (Umbric Great Group in Aquept Suborder, Humic Subgroups in all Suborders of Inceptisols)
Umbrisols are mostly mountainous soils of cool humid climates covered by meadows or sparse forests.
They are characterized by a dark, humus-rich and acid topsoil horizon with a low base saturation. A rather
weak crumb structure is characteristic for the topsoil horizon (Figure A 21).
Umbrisols are formed under dense forb-grass natural vegetation (subalpine meadows) or under deciduous
forests with a prominent lower canopy, sometimes with shrubs. This produces a large volume of plant residues,
which in part may not be strongly decomposed, and elements of a moder humus form may be identified (Zech
et al., 2014). Rather steep slopes and stony parent material provide sufficient drainage in spite of abundant
precipitation and high air moisture; the soil is always moist, but stagnic or gleyic properties are absent. Typical
examples of landscapes with Umbrisols are (sub-)tropical montane cloud forests in Mexico, Bolivia and Chile
(Roman et al., 2010), although Umbrisols also occur at higher altitudes in sub-boreal continental mountain
ranges. Igneous and metamorphic rocks are almost always the parent material for Umbrisols. Worldwide,
Umbrisols occupy approximately 10 million km 2 (Zech et al., 2014).
The geographical location of Umbrisols poses serious limitations for agricultural activities. Chemical
fertility is not low owing to high humus content but is restricted by soil acidity. Liming and mineral fertilizers
are required. Another limiting factor is the risk of erosion because of the predominance of steeper slopes in
areas of Umbrisols. Most Umbrisols are left under natural forests or forestation activity as hard rock or stony
eluvium are not serious obstacles for tree roots. Grazing is less common. Only in New Zealand have high inputs
made it possible to practice intensive dairy farming on these soils (FAO, 2014).
Status of the World’s Soil Resources | Main Report Annex | Soil groups, characteristics,
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distribution and ecosystem services