DIGITALNA ARHIVA ŠUMARSKOG LISTA
prilagođeno pretraživanje po punom tekstu



ŠUMARSKI LIST 13/2005 str. 195     <-- 195 -->        PDF

B. Prpić. P. Jurjcvić. H. Jakovac: ASSHSSINC, THE VALUE ()! ANTI-EROSIVE ...
vents soil erosion and torrents, balances the distribution
in space, alleviates the high water waves, and supports
the purity of water and the number of sources.
Compared to other land ecological systems, forest very
economically treats water. The distribution of water in
a forest ecosystem depends on the tree species, the layers
of brush and undergrowth, the relief, geological
rock, the soil, and the quantity and distribution of the
surface water.


The distribution of water in the forest and its environment
is always more suitable than it is outside the
forest. In the periods of rain and slow melting, forest
retains water, infiltrates it and purifies, and one part of
it discharges through underground streams into the
sources and water streams. By retaining water, forest
reduces the possibilities of high water waves, preventing
the damaging floods and torrents (Figure 2).


In dry periods, forest continues to discharge water
into sources and streams from its reserves, contributing
to the balance of the water regimes in forest areas,
which indicates its very efficient role in creating favourable
hydrological conditions in the landscape.


J u r j e v i ć (1999) presented the enormous effect of
forest upon the hydrological conditions in the environment.
He concluded that the forests in the Sava basin in
Croatia retain annually by interception, spend through
transpiration, and store in the soil about 5.7 billion t
water.


Of all land ecosystems, forest most efficiently prevents
the aquatic and colic soil erosion. A well-tended
forest prevents erosion entirely (Otto, 1994).


Šumarski list SUPLEMENT (2005). 1X6-194


A very useful forest function is the purification of
water. According to Mitscherlich (1975) (from
Otto (1994), of the total water quantity that falls as
precipitation to forest, the quantity of the filtered water,
that purified and drinkable emerges from the forest,
ranges between 30 % and 40 % during vegetation, and
between 70 % and 80 % at the time of its resting. The
remaining water is spent in the process of transpiration,
interception and evaporation.


Considering the average annual value of the precipitation
in the forest areal of Croatia amounting to
1,200 mm, and the area of closed forests of 2 million
ha, about 13 billion t of drinkable water come out from
the forest and can theoretically be used for human needs.
The main part of this quantity certainly cannot be
used, but only several percentages of it present an immeasurable
money value, not to mention the benefits
drinkable water presents in man´s life quality.


In this special edition of "Šumarski list", a number
of authors (Kantor, Topic, Butorac, Ivančević,
Klimo, Kulhavy, and others) present the results
of their long-term research in the field of erosion,
hydrological and water-protection forest functions,
which will throw more light on the field of the generally
beneficial forest functions - the topic of this international
congress.


At the assembly of the German Forestry Society in
2005 titled "Water - one forest product", while reporting
his paper, Weber quoted Hornsmann : "Water is
the blood of the landscape, and forest is its heart".


THE EVALUATION OF THE ANTI-EROSIVE, HYDROLOGICAL
AND WATER-PROTECTIVE FOREST ROLE


There have been attempts of calculating the values
of the three stated generally beneficial forest functions
based on known figures, e.g. the reduction of the costs
for sanation of the damage caused by flood, or the building
costs of strong and high embankments for flood
protection. However, the hydrological forest functions
very efficiently prevent flooding, or alleviate its effects.
Calculated are also the impacts of soil erosion
upon the fertility of the soil that either erodes or contains
sediments of eroded soil particles. By using such
data in the calculation, wc get the amounts that do not
cover the damage caused by erosion, floods and torrents,
which particularly relates to the loss of lives in
the landscapes without forests. Significant are also
technical losses that are hard to predict (collapsed bridges
and buildings, destroyed roads and other infrastructure,
damaged cars, etc.).


The benefits of the non-commercial forest functions
contained in the ecological and social/eco-phys


iological capital present an immense value that can only
be imagined, though economically hardly evaluated
without making errors of underestimation. Such valuations
are frequently the instruments of the lobbies the
interest of which is the forest capital in terms of converting
forestland to other purposes, most frequently to
urban or infrastructure areas. The forest owner then
gets the timber, while the land is sold to the investor of
the lobby at very low prices.


To prevent the cheap sale of the ecological and biological
forest capital and to preserve its beneficial effects
on the environment, the Croatian forestry profession
has introduced and legalised the method of evaluating
the individual non-commercial forest functions
by a point system that determines their value. This greatly
reduced forest conversion to sensible needs, although
exaggerated concessions have been granted for
road building and agriculture in recent years.