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ŠUMARSKI LIST 13/2005 str. 253     <-- 253 -->        PDF

CONCLUSIONS Šumarski list SLiPLEMENT
(2005). 251-252
The following conclusion have been drawn on the forests in the prevention of water-induced soil erosion,
basis of the discussions and papers presented at the floods and torrents and spring water purification:
International Symposium dealing with the role of


CONCLUSIONS


1.
Research of fifty years on hydrological conditions
in two basins in the Beskidi Mountains (Czech
Republic) has shown that extreme precipitation
restricts natural retention capacities of forests. The
most urgent task in the process of forest regeneration
involves the establishment of the forest cover
and the preservation of forest soil with high infiltration
capacity.
Research did not reveal any statistically significant
differences in surface runoff between the regenerated
(final cut) and forested area (Vicha).


2.
Natural forests in Croatia, of which 95 % are state
forests (80 % of all forested areas), are very efficient
in preventing soil erosion, mitigating high
water waves and purifying and converting spring
water into drinking water. The application of silvicultural
tending and regeneration treatments in
both regular and selection forests should be aimed
at preserving the forest soil cover and the soil´s
capacity to absorb and purify water.
3.
Hydrological conditions in mountain forests of
Orlicke hory in the Czech Republic have been
investigated since 1977. According to research,
spruce and beech forests can efficiently mitigate
unfavourable impacts of continuous precipitation
of up to 100 mm. Precipitation above 150 mm
completely saturates the soil profile with water,
which leads to uncontrolled runoff (Kantor).
4.
The scrub of oriental hornbeam (Carpinus (mentalis
Mill.) in the sub-Mediterranean region in
Croatia efficiently curbs water-induced soil erosion.
Surface runoff of precipitation water in this
degraded forest is very low and erosion is completely
absent. Research was conducted in two
sample plots situated in the oriental hornbeam
scrub, of which one was cut down. The average
annual runoff coefficient in the cleared plot was
0.0192, whereas in the scrub-covered plot it was
0.0156. As seen from the above, the difference is
very small. Slightly bigger differences were manifested
by the maximal runoff coefficient.
The authors (Topic, Butorac) point out that the cut
area should be restored as quickly as possible in
order to prevent adverse hydrological impacts on
the soil. This experiment shows: a) that degraded
forms of autochthonous vegetation efficiently
restrict water-induced soil erosion, and b) that soil


purifies the water reaching the subterranean karst
area.


5.
Forests in Croatia are predominantly located in
areas whose relief and climatic characteristics indicate
medium to high degree of soil erodibility. To
assess the risk of erosion, a map of the Republic of
Croatia was used, which was constructed in the
CORINE programme. Moderate risk was found in
26.5 % and high risk in 44.8 % of the area (Husnjak
et ai).


6.
One of the most successful projects undertaken by
the forestry profession in the Mediterranean area
was the regulation of the former torrent in Senjska
Draga. The activities started in the 19™ century
and included afforestation of 22 cultures-enclosures
of black pine in a mosaic-like area of 320 ha,
and the construction of 62 different torrent facilities.
Today, Senjska Draga is a green area free of torrents
and erosion. Until very recently, the water supply
system of the town of Senj used drinking water
from 25 springs that have occurred successively
after afforestation (Ivančević).


7.
Forest ecosystems are efficient water purifiers.
Owing to the forest soil, to its special structure,
chemical composition and wealth of animate
world, the forest purifies precipitation water
mechanically, biologically and partially chemically.
Such water enters underground flows and
springs in the form of drinking water. Lowland and
floodplain forests have proven particularly effective
in retaining N and P from agricultural artificial
fertilizers. The quality of groundwater was much
better in a forest than in agricultural areas in the
Drahany Highlands in the Czech Republic (Klimo
and Kulhavy).
Lyzimetric research in identical lowland forest
ecosystems showed differences in water purification
in various areas of Croatia (Vrbek et al.).


8.
The general condition of watercourses was investigated
in montane areas of Papuk, Velebit and the
Plitvice Lakes National Park in Croatia. Investigation
included the physical-chemical condition of
water, as well as nutrient content, metals, organic
compounds, mineral oils and other indicators of
water quality. Almost all watercourses contained
water of high quality. There was no difference in