C - Lublin

GEOCHEMICAL FUNCTION OF SOIL IN THE ECOSYSTEM
Kerzhentsev A.S., Alekseeva T.V., Alekseev A.O., Abramichev A.Yu.
Metabolism, the turnover of substance and energy between the vegetation
(phytocenosis) and soil (pedocenosis), is the major function of natural ecosystem
Metabolism of an ecosystem is the way of manifestation and maintenance of the
life by interaction of opposite processes of synthesis and decomposition of organic
matter. It consists of three subprocesses: anabolism, necrobolism and catabolism
(Fig. 1). Anabolism turns mineral elements into the biomass. Catabolism converts
dead biomass (necromass) into the mineral elements, which enter a new cycle of
metabolism. Between these strong and opposed directed processes there is a
smoothing their interaction processes of necrobolism, turning the biomass used up
in the life cycle into the necromass.
Natural ecosystem functions in stationary regime when the biomass synthesis
is balanced with its dying and mineralization. Unbalance of metabolism makes up
not more than 1% of the ecosystem mass. This allows us to consider climax
ecosystem as a closed one, where the mass of mineral matter, required for biomass
synthesis, equals the mass of mineral substance, released at mineralization of the
dead biomass (necromass) with an accuracy of 1%. This means that in complete
cycle of metabolism the ecosystem losses 1% of its mass and it is required
subsequent supplement of losses due to the weathering of mountain rocks and
atmospheric precipitations (liquid and solid). Migration of substances on relief and
soil profile (up and down) has not been taken into consideration.
The rate of anabolism, including photosynthesis and respiration, is much
higher than that one of catabolism, hence several periods of biomass synthesis
correspond to a period of complete mineralization of the necromass. The time of
complete mineralization of the mass of annual litter-fall is characteristic time (CT)
of this soil and ecosystem within which the matter mass renews completely. In
tropic soils CT does not exceed 3-5 years, in podzol soils it makes up 50-70 years,
and in chernozems it reaches 300-500 years. The influence of external factors on
specific soil should be considered taking into account its CT.
Long, comparable with CT, change of hydrothermal conditions in one (any)
direction from the averaged or artificial change of the components of ecosystems
mass: biomass, necromass, mineral mass, may disturb the dynamical equilibrium.
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