engleski

Influence of forest fire on water erosion of soil in the Mediterranean area of Croatia

: Because of its climatic and vegetation characteristies the Mediterranean karst area of Republic Croatia is mostly endangered by fire. The soil erosion on the burned forest areas is extensive. In a very short time after the fire the soil layer which the vegetation was creating for centuries, disappears. The protection of soil from erosion on this area has great economical and social significance. To denote the quantity of erosion and surface rainfall flow off on burned areas and the impact of vegetation on the parameters a stationary forest experiment was set near Split (SE of Croatia). On two experimental plots of 100 m2 (20 x 5 m) during the year 2002-2003 the quantity and intensity of rainfall, surface flow off of rainfall and erosion of soil was observed. The first experimental plot was set on the burned area of Aleppo pine, which was burned in August 2001. The GPS coordinates: N 43° 31´, E 16° 32´. The plot lies on the eroded rendsine on marl, on the inclination 20°, at 212 m altitude. The second experimental plot was set in the preserved area of Aleppo pine of complete stand, GPS coordinates N 43° 33´, E 16° 30´, on the inclination of 26° and 227 m altitude. The plot is on brown soil on marl covered by thick layer of leaves. The results show that, in the burnet area of Aleppo pine, during the period observed out of 84 rain days 29 were erodibile. The surface flow off and soil erosion were induced by rainfall from 5.9 mm/m2 to 68.6 mm/m2. The year value of erosion was 19.94 t/ha, the surface flow off of rainfall 36.83 mm/m2, and the coefficient of surface flow off was from 0.0026 to 0.2697. In the preserved area of Aleppo pine out of 84 rainy days, 17 were erodibile. The surface flow off of rainfall, and soil erosion were caused by rainfall of 14.1 mm/m2 to 68.6 mm/m2. The annual value erosion was 0, 044 t/ha, the surface flow off of rainfall 6.43 mm/m2, and the coefficient of surface flow off was from 0.0030 to 0.0556. The Aleppo pine stand in the mouth of the torrent Rupotine has an important and extremely positive part in the protection of soil from erosion. It protects by its crowns the destroying influence of raindrops, the important part of rainfall is re-tained by the crowns (30%), the rest being dropped on the soft forest soil, which takes and infil-trates them. The surface flow off of rainfall under this cover is small, and the soil loss is quite under the tolerated yearly loss, so there is no danger of erosion, or it is very small. The erosion danger is very strong on the burned areas of Aleppo pine, on erodibile soils, such as the degraded rendsine on the marl, what was evident on experimental plot Kučine. It is obvious that the values of surface flow off and soil loss on the plot Kučine were great in this year of research, the second after the fire, when they were caused by little quantity of rainfall, under 10 mm. The reason is the vegetation cover. On the erodibile soil left without forest vegetation, the soil has no protection from the rainfall so the surface flow off and soil loss are obviously very large.

karst; erosion; experimental plot; preserved stand of Aleppo pine; burned stand of Aleppo pine; rainfall; surface flow off; soil loss

nije evidentirano