Hydrophysical characteristics. The main elements of water balance consist of the
amount of rainfall during the cold period, autumn and spring moisture reserves, runoff
rate, coefficient of rainfall uptake, spring increase in moisture and rainfall losses.
Water is a main solvent in the soil. Water and various substances dissolved in it
constitute a liquid phase, from which plants absorb water and nutrients via their root
system. According to L. O. Karpachevsky, each of tree species has its own peculiarities
of transition to water solutions of mineral constituents.
For the day, there is a large amount of scientific information on the hydrological
role of tree plantations has been gathered, but its contrariety makes it impossible to
determine definitively the influence of tree vegetation on modern processes of soil
formation in tree root zone's area. I.I. Smolyaninov points out a decrease in moisture
amount that is hardly digestible by plants under forest plantations, which were
investigated in the upper (0-10 cm) layer of soil (data on research in Velyky Anadol).
For deeper layers, this is true only for species with a deep root system (oak); while
surface rooted ones do not change the amount of moisture that is difficult to digest, in
the soil lower than 50 cm.
S.V. Zonn, Ye.A. Kuzmina, while investigating the physical properties of
degraded black soils under forest plantations, showed an increase in maximum
hygroscopicity under the influence of forest plantations in the upper (30-40 cm) layer
of soil, as compared to arable soils. The authors did not reveal any dependence of
maximum hygroscopicity from the type of tree species [3]. In works of I. N. Vasilieva
it was indicated that the value of the maximum hygroscopicity reduces with the depth
of the soil profile.
The results of our studies of hydrophysical characteristics of deep typical black
soils under the cover of various plants suggest that they do not significantly change in
black soils under different cultures (tree and grass). The value of maximum
hygroscopicity gradually decreases with respect to black soils' profile. This indicator
depends on the quantity and quality of colloids in the soil.
Capillary and total moisture content grow under oak plantations by 5 and 8%
respectively. Field moisture content of upper horizons of forest black soils is higher by
2-5% than that of arable ones, which is connected with better structural state of forest
black soils. A certain role in moisture increase in the tree species' root zone is played
by the roots themselves. They prevent moisture movement to the depth by their
perennial duff-shaped root extensions, and thus contribute to the maintenance of
moisture in the maximum possible amounts in soil micro-aggregates of rhizosphere.
In such a way, all hydrophysical constants (maximum hygroscopicity, capillary
and total moisture content) in black soils under forest cultures have higher rates than
that in arable black soils.
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