Logging systems and soil erosion on clearcuts in mountain forests
1990
Sach, F. (Vyzkumny Ustav Lesniho Hospodarstvi a Myslivosti, Opocno (CSFR). Vyzkumna Stanice)
The management in mountain forests influences their soil conservation function. Besides the forest road network, a key role is played by logging systems. Following from the results of investigations on slopes 15 - 25 degrees in the Beskids and Krkonose Mts., tractor skid trails disturbed the soil surface on the greatest part of the cutover - 7.6 to 13.0 per cent, smaller disturbance of soil surface was caused by horse skid trails (6.6 per cent) and by high-lead yarding (1.0 to 1.7 per cent). This disturbance was related to the logging rill erosion: 62 to 195 m3 per ha, or 66 m3 per ha, or 11 m3 per ha, resp. Surface runoff depended on the extent and intensity of surface disturbance; the intensity of water erosion along skid trails after the end of skidding was related to the latter factors. The values of water erosion determined by the method of rain simulation on small runoff plots made in the same order 1.22 to 2.11, 0.04 and 0.007 to 0.09 m3 . year -1 in conversion per 1 ha cutover. The overgrowing of skid trails with grasses reduced only insignificantly the coefficient of surface runoff three years after cutting: on clearcut areas with tractor skidding from 6.4-11.3 per cent to 4.3-8.3 per cent of the yearly precipitation sum that has fallen onto the cutover surface, on the clearcut area with horse skidding from 2.2 to 1.4 per cent and on clearcut areas with high-lead yarding from 0.7-1.2 to 0.6 - 1.0 per cent. On the other hand, a decrease in water erosion was marked, from the above-mentioned values to 0.03-0.09, 0.01 and 0.01 m3 per ha/year in the same order. Water erosion on clearcut areas is reduced first of all by the use of suitable logging systems, and in specific cases by the restoration of the surface of skid trails.
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