Bedrock Weathering and Stream Water Chemistry in Felsic and Ultramafic Forest Catchments

Two small forested catchments, each underlain by geochemically contrasting silicate rock types, were studied in the western Czech Republic. The felsic (granitic) Lysina catchment exhibited low resilience to anthropogenic acidic deposition and therefore low pH, Mg and high concentration of toxic species of Al in drainage water. Pluhův Bor, underlain by ultramafic rocks (especially serpentinite), exhibited very high resilience to acidic deposition and also peculiar drainage water chemistry due to the lithology (high pH, Mg, Ni and Cr). A significant depletion trend in Mg was observed from the unweathered to weathered rocks and to the topsoils at both sites. Enrichment profiles of K and Ca within the topsoil at Pluhův Bor indicated biocycling of these limiting nutrients.