Soil biomantle

The biomantle is thus the upper zone of soil that is predominantly a product of organic activity and the area where bioturbation is a dominant process.

While the general term bioturbation refers mainly to these three mixing processes, unless otherwise specified it is commonly used as a synonym to faunalturbation (animal burrowings).

), horizon notations are: M-SL-W, where M is the mineral soil (extended topsoil), SL is stonelayer, and W is the underlying weathered or saprolite zone.

The "critical zone", a recent conceptual framework, encompasses the Earth's outer layer in which most surface and near-surface life sustaining processes operate.

In most subtropical and tropical areas where deep and large volume bioturbators dwell, and in some midlatitudes like South Africa,[16][17][18] such thick, two-layered biomantles (those with stonelayers) above structured saprolite are very common.

This criterion denotes small, often pelletized microbiofabric and mesobiofabric produced by invertebrates (ants, worms, termites), usually observed under hand lens or higher magnification (soil thin sections).

are invariably larger than burrow diameters of most key bioturbators at such sites (small rodents, ants, termites, worms), they settle downward and form a stonelayer, and thus become part of a two-layered biomantle.

[23][24] Smaller artifacts (flakes, debitage) often are homogenized throughout the upper biomantle, and commonly observed in recent bioturbational spoil heaps, like those produced by pocket gophers, moles, and mole-rats.

[25][26] Beginning with Darwin, the earthworm has been recognized as a key bioturbator of soil biomantles and human artifacts on many continents and islands.

[34][35][36] The biomantle is an organic-rich near-surface layer in which bioturbation is a dominant process, with all other biological and more traditional soil processes normally being subsidiary (e.g., organic matter productions, eluviations-illuviations, weathering-biochemical transformations, wind and water erosions-depositions, freeze-thaw, dilations-contractions, shrink-swell, gravity movements, geochemical-capillary surface-wickings and precipitations, etc.).

[14][42][43][44] Wilkinson and Humphreys offer evidence that "bioturbation appears to be the most active pedogenic process operating in many soils.

Biomixing refers to the kind of soil bioturbations typically caused by surface-, shallow-, and intermediate-burrowing vertebrates, such as rodents (pocket gophers, tuco-tucos, mole-rats), insectivores (moles), mustelids (badgers), canids (wolves, coyotes, foxes), marsupials (marsupial moles, wombats), aardvarks, armadillos, pigs, and other similar organisms.

Biotransfers refers to transfers of soil by animals, vertebrates or invertebrates, either to the surface, within the biomantle, or from lower levels.

Termites, for example, may burrow downward many meters into weathered and unweathered parent material to collect moist soil for constructing their surface mounds (termitaria).