Application of the forest-soil-water model (PnET-BGC/CHESS) to the Lysina catchment, Czech Republic

In this study a fully linked plant-soil-water model PnET-BGC/CHESS (Santore, R.C., 1996. PnET-BGC/CHESS model. Version P3NC115, Santore, R.C., 1999. Modeling forest soil response to chemical treatment at three sites in the Adirondack Mountains, New York) was evaluated and applied. Forest growth, hydrologic, and biogeochemical processes with emphasis on element cycling in forest and adjacent aquatic ecosystems were simulated for the Lysina catchment, Czech Republic. The PnET-BGC submodel expands calculations of forest productivity and water use of the earliest version of the PnET model to include decomposition processes and cycling of major nutrients and other elements. The CHESS submodel simulates abiotic soil chemical processes. The study catchment consists of Norway spruce (Picea abies) plantations on Spodosols located in a granitic highland of western Bohemia. Forest growth, hydrology and biogeochemistry of the catchment were simulated for the period 1550-2050. Simulated concentrations of SO₄/^2-, F^-, Ca²⁺, Mg²⁺, Na⁺, K⁺, Fe(T), Si, and monomeric A1 were similar to streamwater concentrations measured in 1990-1994. The model moderately overpredicted H⁺, C1^- and DOC, and highly overpredicted NO₃/^and especially NH₄/⁺. A scenario of reductions of S inputs by 67% of 1991-1994 values in 1995-2050 showed a decrease in base saturation of soil of 2.5% between 1995 and 2050. Inputs of S reduced by 90% of current values showed an increase in soil base saturation after 2030. Scenarios of improved deposition of S showed desorption of previously stored S to drainage water which delayed recovery from inputs of acidic deposition.