Natural regeneration potential of the degraded Krkonose forests

Self-regulating mechanisms and natural regeneration capacities still exist in the Krkonose National Park, although the magnitude of these varies with altitude. A study of changes after forest decline and clear-cut with respect to the e stablishment of pioneer toes, changes in the herb layer, changes in humus p rofile characteristics and soil base status was conducted in the Krkonose M ountains National Park in order to evaluate potentials for natural regenera tion in forests affected by severe atmospheric deposition. Pioneer trees establish in both the upper and the lower supramontane zones. Even lowland species such as Fagus sylvatica appear to rejuvenate at high altitude, although in low numbers. Cover values of Betula pendula increase during clear-cut development, partly because they are avoided by deer; thos e of Sorbus aucuparia remain low due to browsing. In the upper supramontane zone changes in the herb layer are not significan t: Calamagrostis villosa is dominant in (already declined) forests and rema ins so in clear-cut areas. In the lower supramontane zone Vaccinium myrtill us has its optimum in forests, while Deschampsia flexuosa strongly increase s in clear-cut areas. Pioneer herbs establish after clearcut. During clear-cut development, LF horizons decrease, due to a shift in input from low-decomposable spruce needles to easily decomposable grass (and lat er pioneer) litter. H horizons increase because of continuing decomposition and organic matter transfer from F to H horizons. At higher altitude, thes e processes occur at a lower rate. Pioneer trees have ameliorating effects on the soil via an increase in base elements and pH compared to spruce forests. There are only few indications that pioneer trees are severely hampered by dense grass carpets, which may occur in particular microhabitats escaping a ttention in the larger plot descriptions. High grass covers instead seem to have stimulating effects on seedling establishment via the improvement of the humus profile, which continues after pioneer trees grow up. Copyright ( C) 2000 John Wiley & Sons, Ltd.