Syrosem

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The term Syrosem comes from Russian and means raw earth . It is a soil type from the class of terrestrial raw soils , which is on solid rock at the beginning of soil development . Sometimes the term rubble floor is also used . In soil science it is abbreviated as OO.

Origin and Distribution

The Syrosem has a very thin mineral horizon with a maximum of 2 cm , which rests directly on the massive subsurface. The type of substrate material can vary immensely. There are two ways to reach the syrosemic stage :

On the one hand, the settlement of lichens and mosses is often the initial phase of soil formation on rock. Together with blown leaves, an organic layer is created, which is called rock humus soil or skeletal humus soil . Due to dust and the weathering of the subsurface, the mineral content in the layer increases over time, while the organic content decreases. As soon as the mineral content is above 70 % by weight , the layer is referred to as the mineral soil horizon and the soil type Syrosem is achieved. Syrosems of this type of origin have very high humus contents of up to 30% by weight.

On the other hand, mineral dusts can also be deposited immediately on solid substrates, so that a mineral soil horizon is present from the start. In this case the syrosemes have a rather low humus content.

Classic locations for Syroseme are freshly formed, rocky to massive zones in the initial stage of soil formation, such as mudslides or melted glacier zones . This type of soil occurs naturally only in mountains and very cold regions. Today, the soil type can be found almost all over the world, as it also forms on man-made sites such as rail beds , dumps , industrial wasteland or little-used traffic routes . However, as the soil formation progresses, the mineral horizon quickly becomes thicker than 2 cm, so that syrosemes are only a short transition stage. Permanent occurrences can only be found in erosion-prone mountain areas.

Soil socialization

Because of the way they were formed, syrosemes are often closely associated with skeletal and rock humus soils. The stage is quickly completed on all sites that are not susceptible to erosion and soil types with thicker layers emerge, the so-called Ah / C soils . In contrast to the Syrosem, in which the starting material does not play a role, a distinction must be made in the subsequent stages according to substrate. On limestone (> 75% lime ) this is the rendzina , on marly rocks (2–75% lime) the pararendzina and on lime-free rocks such as sandstone or mudstone (<2% lime) the rankers .

Sometimes there is a socialization with the Lockersyrosem , which represents an initial stage on loose materials such as sand .

Leveling

According to the German soil systematics, the Syrosem has the leveling Ai / mC.

  • Ai: On the surface there is a topsoil horizon (A) in the initial stage (i = initial) of soil formation. It is mostly gaps, very shallow with a maximum thickness of 2 cm and lies directly on the rock. The primary quality of the Ai is its smallness . Therefore, the chemical and physical properties of the material, which can be very different, are not taken into account.
  • mC: The massive (m) starting material (C) lies below the topsoil horizon. The chemical and physical properties of the material can be diverse, since a differentiation according to substrate is not yet made in the syrosemic stage.

In the international soil classification World Reference Base for Soil Resources (WRB), syrosemes are classified as lithic leptosols . Among the Leptosolen but also includes the Lockersyroseme and parts of the rock humus soils , skeletal humus , ranker, Rendzinas and Pararendzinas.

Usage and properties

The chemical and physical properties of the topsoil can be diverse and are still very similar to the original material. Syrosemes on limestone have a very high pH value , while those on sandstone have hardly any nutrients . Because of the shallow depth, these properties take a back seat, which is why they are not taken into account when addressing them as Syrosem.

The very thin soil (maximum 2 cm) can hardly store water, so that it is extremely dry. It also offers hardly any space for rooting. Therefore an agricultural use is impossible. By and large, only pioneer and mountain plants are able to grow there. In the mountains there is sometimes a very extensive forestry use with extreme shallow roots such as Swiss stone pine or spruce .

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