The Role of Living Organisms in Soil Formation

Soil_profileSoil is closely connected to ecosystem development. In fact, the natural composition of soils is a result of interaction of the mineral substrate with the soil biota: microscopic and macroscopic animals, plants and their physiological activities. Other basic factors, such as the local climate and topography, as well as past developments over long periods of time set the scene. More recent factors, such as technical recultivation measures have a major impact on the restoration and functioning of soils.

Soils are in the basis of development of vegetation and thus water and nutrient cycling by plants. Overall, terrestrial ecosystems would be impossible without soil. In return, plants give back to the soil organic matter, structures and energy. Vegetation is in fact the main driver for the formation of soil horizon “A”.

Soil_profile

Dead organic matter from the plants in the form of litter and root exudate (including acids, sugars, polysaccharides and ectoenzymes) and dead roots are processed by living organisms in the soils. And this is to a large extent the most important process in the complex formation of soils.

Not surprisingly, it has been shown that the presence or absence of certain groups of soil organisms may alter soil formation in one direction or the other. For example, earthworms may substantially improve soil condition in newly formed soils, such as in post mining sites. In the same time, earthworms can also cause severe negative impacts by bringing invasive exotic species to the ecosystem.

fig2

Detail of soil profile in developing post mining soils arrows show structures created by soil macro-arthropods (above) and earthworms (below)

 Beside plants, a wide array of soil organisms of various sizes, from tiny bacteria to “giants” as big as the earthworm take part in soil formation.  Some, such as the mycorhisal fungi, live in close association with plant roots while others live freely in the soil.  These organisms contribute to soil formation in different ways: The fungal hyphae connect the soil particles into larger soil aggregates. Animals process the plant residues and mix it into the soil, literally creating the soil profile.

Soil is the most conservative part of the ecosystem. In post-mining sites we can see how soil is formed by action of plant roots and soil biota. This process can be enhanced or suppressed by different recultivation measures. More about soil recultivation – in our next posts.

This article was written by guest blogger Prof. Jan Frouz – director of the Environmental Centre of the Charles University in Prague and editor of the book Soil Biota and Ecosystem Development in Post Mining Sites (CRC Press 2013).

3 thoughts on “The Role of Living Organisms in Soil Formation

  1. Pingback: In the beginning was Soil « eco-restore.net

  2. Pingback: Springtail jumps, video | Dear Kitty. Some blog

  3. Pingback: Soil restoration techniques at post mining sites « eco-restore.net

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