Biomass formation, nutrient uptake and release in fern stands of Athyrium distentifolium on deforested areas affected by pollution: Comparison with grass stands

Impact of climatic factors and acid deposits resulted at higher altitude in the Beskydy Mts in worse growth parameters of the tall fern Athyrium distentifolium. Ferns had here shorter fronds, thinner petioles and lower frond biomass. Similarly, a lower length and biomass of Calamagrostis arundinacea shoots was also recorded in similar deforested sites in uppermost mountain zones. In contrast to grass stands of deforested areas, fern stands at a lower aboveground biomass production (194-350 g.m ) accumulated in it a large amount nitrogen (3.9-7.0 gN.m ). Thus a higher amount of nitrogen was required in these fern stands for the formation of the same amount of aboveground biomass than in compared grass stands. At the slower decomposition of fern litter (19-25 % dry mass of leaflets and 18-19% stalks per year) than at that of grass litter (35-54% leaves, 17-30% stalks), the release of Ca (54-55%) and Mg (86-87%) was faster and the amount of nitrogen immobilized in one year old fern litter reached up to 46 kgN per ha. A comparison of soil features indicates less favourable soil conditions in fern stands (lower pH values, Ca contents and Ca/Al ratios) than in grass stands. These data thus suggest that fern stand formation on deforested sites has not the same positive ameliorative effect on soil environment as that described for both Calamagrostis species. -2 -