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ŠUMARSKI LIST 9-10/1995 str. 21     <-- 21 -->        PDF

V. Topic: UTJECAJ ŠUMSKE VEGETACIJE NA SUZBIJANJE EROZIJE U IUIJIČNIM SLIVOVIMA
SUMMARY: The Mediterranean area of the Republic of Croatia covers


15.389 km2. It is a typical karst area, where the soil erosion and its most excessive
form — torrents — are a great problem. The greatest and the most difficult
torrent problem is on the areas with unpassable soils (werfench, marls
and flysch), which take great areas in the coastal part and in the flows of
rivers. These areas are very erosive, especially if they are badly managed and
without vegetation. Having thes reasons in mind, the Institute for the adriatic
cultures and karst melioration in Split founded in the year 1971 the experimental
plots Bp B2 and B; in the mouth of the torrent Suvava in Mud, on the
inclination 28,8% with the recipients and the corresponding plant cover, with
the cum to come to the original data about the important characteristics of the
waiter soil erosion by modern methods. The flow of Suvava takes the area of
1.823 ha, with the length of the main flow of 10,1 km and the entire length of
greater and smaller tributery streams — torrents of 20,8 km. Its form is protruded
and it extends itself between 460 and 961 m above the sea level (Fig. 1).
The climate of this area is submediterranean, with the average year rainfall
of 1.329 mm. In Mud there are 92 rainy days on an average, and from that
18 erosive ones. In the geological sense, the flow is very different. There are
formations of lower and middle trias, lias, iura and the quarter. On the trias
we mainly find minerologic soils, on the limestones of iura thin brown soils
and from the quarter there are smaller areas of terra rossa soils.


The greatest part of the flow area, in the vegetation sense, belongs to the
community of Oak downy, and Hornbeam oriental. The forest of almost whole
flow area was pushed back and its is found in different stadiums of degradations,
from underbrush to bare ground.


This paper deals with the erosion processes on bare soil and on the soils
under forest vegetation (Spanish broom, juniper). The research was done on
the experimental plot Bsfor the period of 1973 — 1981, the the period when
the plot was without vegetation (bare ground) and for the period of 1982 —
1993 when it was under vegetation.


The data of the surface flow off and soil loss are shown on the graph 1 and


2. The average year values of the surface flow off on the bare area are 11,6
mm (1.116,0 m\ha´), with the coefficient of flow away 0,076 and soil loss
191,571 g. m2 or 1,921. ha´, and on the area with the vegetative cover (Spartium
junceum and Juniper us oxycedrus) the surface flow off is 8,3 mm (83,0 m3.ha~
´) with the coefficient of flow away 0,0068 and the soil loss of only 0,309 g.m2
or 0,0031 t.hci1. The soil loss on the bare area 619,97 times larger than
under the vegetative cover.
Key words: the flow of the torrent Suvava, experimental plot B bare
ground, area with the vegetative cover, rainfall, the surface flow off, erosion,
soil loss, Spanish broom, juniper, mediterranean karst area.


Šumarski liši hr. 9—10. CMX(1995), 299-303