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ŠUMARSKI LIST 13/2005 str. 41     <-- 41 -->        PDF

P. Kantor: POSSIBILITIES OF MOUNTAIN FORESTS IN REDUCING HIGH WATERS AND FLOODS Šumarski list SUPLEMENT (2005), 31-39
2.
From the aspect of ecological stability and safety of
yield and production, one of evident priorities of forestry
is the transformation of spruce monocultures
to mixed stands. However, research results have
proved, that the increased proportion of broadleaves
cannot decrease the danger of high waters and
floods. Broadleaved species are able to retain and
draw less precipitation water than coniferous species
(particularly spruce) with respect to their leafless
state out of the growing season and smaller
biomass of assimilatory organs.
3.
Upland and mountain forests (unlike all non-forest
ecosystems) reduce very easily rainstorms up to 50
mm. Uninterrupted precipitation up to 100 mm manifests
itself in the total amount of runoff from the
forest but from the aspect of water-management effectiveness
is still acceptable. A threshold of 150 to
200 mm of uninterrupted precipitation can be considered
to be a critical limit for the effective reduction
of floods by the forest. Under conditions of this precipitation
total, forest soil is always completely saturated
by water including depressions both in the
soil surface and the parent rock stratum. Then, uncontrolled
and spontaneous runoff occurs through
the whole soil profile appearing often on the soil
surface irrespective of a species composition or the
method of management. In other words, also the forest
soil body shows, similarly as eg reservoirs, its
capacity possibilities which cannot be exceeded.