The top 30 cm of a square metre of soil (300 dm^3 or 300 litres) contains an average of approx. 265 g of soil organisms. Depending on the soil type and type of development, the composition of soil organism species and their respective individual densities can vary greatly.

In well-developed, humus-rich soil, it can look like the diagram below.

As the thin skin around our earth, soils play a decisive role in the carbon cycle: Soils are the largest terrestrial carbon store and at the same time one of the most important natural_{sources of CO2} for the atmosphere. Soils are therefore also a decisive factor in climate change. They influence and are influenced:

It is assumed that rising temperatures will accelerate the conversion processes by soil organisms in the soil, among others, which would mean a positive feedback between global warming and CO₂ release.

However, water and nutrient availability are also decisive influencing factors that make the system complex and difficult to predict.

Sources:

Gisi, U., Schenker, R., Stadelmann, F. X., Sticher, H. (1997): Soil Ecology. 2nd edition. Stuttgart; New York: Thieme. Page 64 & 72

Jedicke E. (1989): Soil - formation, ecology, protection. Ravensburg, Maier. S. 68

Schrumpf, M., Trumbore, S. (2021): Our most important carbon store: How soil as the thin skin of the earth influences global material cycles and the climate. Max Planck Society for the Advancement of Science, URL: www.jstor.org/stable/resrep32954 Accessed: 03-05-2023