The study of density of soil's solid phase (specific gravity) indicates a certain
change in value of specific gravity in solid phase of soil under forest plantations and
arable land. All forest plantations contribute to a slight decrease of soil solid phase's
density in the upper part of black soil profile.
The value of total soils' porosity, calculated from the data of their specific gravity
and volumetric weight, shows, firstly, that with the profile depth in all the variants of
the experiment the porosity decreases, and secondly, and most importantly, forest
cultures, especially oak, contribute to growth of soil aeration in the upper horizon as
well as to increase of total porosity (55.2% – under the oak, 53.4%, 53.48% under the
grass and only 45.96% under the arable land). Consequently, the forest has a positive
effect upon the soil. Forest plantations give input to the formation of better aeration in
typical black soils in comparison to control plots (arable land). For a relatively short
period of growing in black soil (more than 30 years), forest plantations have made a
significant, but uneven influence (depending on the kind of forest forming species) on
its physical and hydrophysical properties. These changes occur with greater intensity
in root zone and are expressed in the decrease of soil's volumetric weight down to a
depth of 100-110 cm, which causes an increase in its porosity, air- and moisture
content.
Decrease of specific gravity of soil's solid phase is a reason for soil's structural
state improvement and increase of its water resistance.
Therefore, the value of volumetric weight and solid phase density in all soils
increases down the profile. The volumetric weight of black soils under forest
plantations is much lower (1.13 g/cm
3
) in comparison to arable land (1.4 g/cm
3
); the
upper horizons have the smallest density, which is created under the crowns of oak
plantations – 2.53 g/cm
3
, under herbs – 2.54 g/cm
3
, and maximum – in black soils of
arable land – 2.59 g/cm
3
.
Thus, for a relatively short period (more than 30 years) of growing in black soil
forest plantations have displayed a significant, but uneven influence (depending on the
kind of forest forming species) on its physical and hydrophysical properties.
Electrical conductivity of soil's water suspensions. Widespread use of generally
available physical and chemical methods, in particular conductometric, is gaining
popularity in soil sciences. These are based on the measurement of environments'
electrical conductivity that is associated chiefly with presence of free electrons and
charged particles (ions, colloids) in the soil.
Conductometry (from "conductivity" and Greek "metreo" – to measure) is a
complex of electrochemical methods of analysis based on measuring the electrical
conductivity of various mixtures and solutions. Advantages of conductometry are high
sensitivity, rather high accuracy (relative precision of measurements is 0,1-2,0%),
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