Biogeochemistry Of Forested Catchments In A Changing Environment PDF Download

Hydrobiogeochemical patterns were studied in two forested catchments in the Czech Republic, one underlain by leucogranite (Lysina), the other by serpentinite. The objective was to compare and contrast element pools and fluxes in the catchments with similar topography, vegetation, climate, and atmospheric deposition, but different lithology. High weathering rates at the serpentinite site resulted in magnesium as the dominant cation on the soil exchange complex and in drainage water. Other basic cations (calcium, potassium, sodium) showed relatively low concentrations and outflow in streamwater. The catchment exhibited high base saturation (BS) in mineral soil, and near neutral soil and stream pH, despite elevated inputs of acidic deposition. Slow growth of Norway spruce may be caused by potassium deficiency, magnesium oversupply and/or nickel toxicity. In contrast, the leucogranite site showed low concentrations of exchangeable basic cations on the soil exchange complex and in streamwater. Soil and drainage water were highly impacted by acidic deposition. Soil pH was acidic throughout the soil profile, and the BS of the mineral soil was low. Supplies of basic cations from atmospheric deposition and soil processes were smaller than inputs of sulfate on an equivalence basis, resulting in low pH and high concentrations of aluminum in drainage water. Needle yellowing in Norway spruce was possibly the result of magnesium deficiency. These catchments served as valuable end-members of ecosystem sensitivity to severe levels of acidic deposition. The second objective was to apply a plant-soil-water model PnET-BGC/CHESS at Lysina. Forest growth and hydrobiogeochemistry were simulated for the period 1550-2050. Simulated concentrations of sulfate, fluoride, calcium, magnesium, sodium, potassium, silica, iron, and aluminum were similar to streamwater concentrations measured in 1990-1994. The model moderately overpredicted hydrogen ion, chloride and dissolved organic carbon, and highly overpredicted nitrate and especially ammonium. A scenario of sulfur inputs reductions by 67% of 1991-1994 values in 1995-2050 predicted a further decrease in soil BS between 1995 and 2050. A simulation in which inputs of sulfur were reduced by 90% showed an increase in BS after 2030. Simulations showed that desorption of previously stored sulfur to drainage water would delay recovery from acidic deposition.