SEASONAL CHEMISTRY OF PORE-WATER IN HUMMOCKS AND HOLLOWS IN A POOR-MIRE IN THE SOUTHERN ALPS (ITALY)

We compared the seasonal patterns of sodium, potassium, calcium, and m agnesium concentrations, pH, and electrical conductivity in pore water in a nutrient-poor mire of the southern Alps to precipitation chemist ry, water-table depth, and potential evapotranspiration, with the main objective to unravel differences between pore-water chemistry in humm ock and hollow habitats. Sodium concentrations in mire water were prim arily determined by precipitation inputs, with highest values in sprin g. Potassium concentrations were dependent on vegetation uptake, peaki ng before the growing season started, and showing lowest values in sum mer. Calcium and magnesium concentrations were highest in summer. Cati on-exchange processes, evaporation, and humification affected the peri odicity of bivalent cations. The pH decreased from spring to autumn, g radually in hollow water and more abruptely in hummock water. Electric al conductivity followed the bivalent cation concentration pattern bot h in hummocks and hollows.