Soil Biogeochemistry in Arid Ecosystems

High biotic activity is characteristic for soils of Meadow Steppe ecosystems with relatively high precipitation. An enormous number of invertebrates promptly disintegrate and digest the plant residues and mix them with the mineral soil matter. The presence of the predominant part of plant biomass as the underground material facilitates greatly this process. 

These properties of soils in Steppe ecosystems are favorable to the formation of uppermost humus barrier, where the accumulation of almost all the chemical species occur. The concentration of chemical elements is slightly decreasing downward in soil profile, in parallel with decreasing soil humus content (Eigure 15). 

The significant part of trace elements in the soils of Steppe ecosystems are bound with highly dispersed mineral-organic particles, to a lesser degree, with only organic matter. We can see that the water soluble and exchangeable forms are less than 1 % of the total content. Specific forms of trace elements are bound with carbonate and gypsum in B and C horizons (Table 28). 

Role of humidity in soil formation in Steppe and Desert ecosystems The water deficiency in Arid ecosystems is the main restricting factor for biogeo-chemical processes. We know that many links of the biogeochemical food web are connected in Steppe soils with invertebrates. Their population varies very much in Steppe ecosystems depending on the moisture conditions (Table 29). Eor instance, the wet biomass of soil invertebrates in the Meadow Steppe and Forest Steppe ecosystems exceeds that for the Extra-Dry Rocky Desert ecosystems by 150-3(X) times. 

Soil Total content, ppm Fraction of total Co content bound with, %  

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