Pavel Krám

The biogeochemistry of basic cations in two forest catchments with contrasting lithology in the Czech Republic

The biogeochemistry of Ca, Mg, K, and Nawere investigated in two forested catchments in theCzech Republic, one underlain by leucogranite, theother by serpentinite. High weathering rates at theserpentinite site at Pluhův Bor resultedin Mg2+ as the dominant cation on the soilexchange complex and in drainage water. Other basiccations (Ca2+, K+, Na+) showedrelatively low concentrations and outflow instreamwater. The catchment exhibited high basesaturation in mineral soils (>70%), and nearneutral soil and stream pH, despite elevated inputsof acidic deposition. Slow growth of Norway spruceat Pluhův Bor may be caused by K deficiency, Mgoversupply and/or Ni toxicity. In contrast, thegranitic site at Lysina showed low concentrations ofbasic cations on the soil exchange complex and instreamwater. Soil and drainage water at Lysina werehighly impacted by acidic deposition. Soil pH wasextremely acidic (<4.5) throughout the soilprofile, and the base saturation of the mineral soilwas very low (<5%). Supplies of basic cationsfrom atmospheric deposition and soil processes wereless than inputs of SO2-4 on anequivalence basis, resulting in low pH and highconcentrations of total Al in drainage water. Needle yellowing in Norway spruce was possibly theresult of Mg deficiency at Lysina. Because of theirextremely different lithologies, these catchmentsserve as valuable end-members of ecosystemsensitivity to elevated levels of acidicdeposition.

Isotopic evidence for processes of sulfur retention/release in 13 forested catchments spanning a strong pollution gradient (Czech Republic, central Europe)

Sulfur isotope systematics were studied in 13 small catchments in the Czech Republic, similar in topography (V-shaped valley) and vegetation (Norway spruce). The sites differed in elevation, rainfall, bedrock, soil type and S pollution. Across the sites, δ 34 5 values decreased in the order: bulk deposition > runoff > spruce throughfall > C-horizon soil > A/B-horizon soil > 0-horizon soil > bedrock (means of 5.5, 4.8, 4.7, 4.6, 4.2, 3.1 and 1.5%o, respectively). Some of the sites had a net export of S, while others accumulated S. Sites exporting S were located in the polluted north where atmospheric S input started to decrease in 1987. Sites retaining S were located in the relatively unpolluted south. Sulfur isotope composition of runoff depended on whether the catchment accumulated or released S. Sites releasing S had runoff δ 34 S values lower than deposition. In contrast, sites retaining S had runoff δ 34 S values higher than deposition. Across the sites, the δ 34 5 values of runoff were not correlated with δ 34 S values of bedrock, indicating that the contribution of bedrock to S in runoff was negligible. The δ 34 S values of runoff were strongly positively correlated with the δ 34 S values of soil. Sulfur present in the C-horizon of soils was mainly derived from atmospheric deposition, not bedrock. Sulfur isotope mass balances were constructed for each catchment, making it possible to quantify the difference between δ 34 S values of the within-catchment source/sink of S and runoff S. Sulfur isotope mass balances indicated that the sink for the retained S at unpolluted sites and the source of the released S at polluted sites were isotopically fractionated by the same amount relative to runoff S. Inorganic and organic processes were considered as possible causes for this observation. Biological S cycling involves a variety of reactions, some of which fractionate S isotopes. In contrast, adsorption/desorption of inorganic sulfate in soil and weathering of S-containing minerals do not fractionate S isotopes. Therefore the within-catchment source/sink of S must be largely a result of biological S cycling. Organic S cycling played an important role over a wide range of atmospheric S inputs from 13 to 130 kg S ha -1 yr -1 .

Role of Organic Solutes in the Chemistry Of Acid‐Impacted Bog Waters of the Western Czech Republic

In many regions, naturally occurring organic acid anions can effectively buffer mineral acid inputs from atmospheric deposition, moderating their effect on surface water pH. We studied the effect of chronically high inputs of acid rain on the chemistry of three brown-water streams in the western Czech Republic. The dissolved organic acids in the streams were similar in character to those of other systems in Europe and North America. The site densities (the carboxyl group content per mass of C) were similar to values reported from Fenno-Scandia, and the relationship between the apparent pKa and pH conformed to those from two North American studies. Sulfate and organic acid anions (OA−) were the dominant anions in all three streams, yet despite high dissolved organic carbon and total organic acid concentrations, OA − comprised only 21–32% of total anion charge. This pattern was due to very high sulfate concentrations and, in two of the streams, a low degree of dissociation of the organic acids, probably the results of high long-term inputs of strong acids. Stream water pH was highly correlated to sulfate concentration, but uncorrelated with OA−, suggesting that free acidity is controlled by strong mineral acids rather than organic acids. Thus future reductions in strong acid inputs should result in increased pH and a return to organic control over acid-base chemistry.

Modelling soil nitrogen: The MAGIC model with nitrogen retention linked to carbon turnover using decomposer dynamics

We present a new formulation of the acidification model MAGIC that uses decomposer dynamics to link nitrogen (N) cycling to carbon (C) turnover in soils. The new model is evaluated by application to 15-30 years of water chemistry data at three coniferous-forested sites in the Czech Republic where deposition of sulphur (S) and N have decreased by >80% and 40%, respectively. Sulphate concentrations in waters have declined commensurately with S deposition, but nitrate concentrations have shown much larger decreases relative to N deposition. This behaviour is inconsistent with most conceptual models of N saturation, and with earlier versions of MAGIC which assume N retention to be a first-order function of N deposition and/or controlled by the soil C/N ratio. In comparison with earlier versions, the new formulation more correctly simulates observed short-term changes in nitrate leaching, as well as long-term retention of N in soils. The model suggests that, despite recent deposition reductions and recovery, progressive N saturation will lead to increased future nitrate leaching, ecosystem eutrophication and re-acidification.

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

Abstract 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 SO 4 2− , F − , Ca 2+ , Mg 2+ , Na + , K + , Fe T , Si, and monomeric Al were similar to streamwater concentrations measured in 1990–1994. The model moderately overpredicted H + , Cl − and DOC, and highly overpredicted NO 3 − and especially NH 4 + . 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.

Does Acidification Policy Follow Research in Northern Sweden? The Case of Natural Acidity During the 1990’s

The situation in northern Sweden did not figure prominently in the intense period of research during the 1980s that laid the basis for many acidification-related policies now in effect in Europe and Sweden. Northern Sweden has not only relatively low acid deposition levels and significant sources of natural acidity, but also intense episodes of pH decline during spring flood that are a major focus of liming activity. Controversy over that liming and natural acidity has led to scientific advances. These include discovery of a correlation between sulfur in snow and the anthropogenic contribution to the subsequent spring flood ANC decline, but also that natural organic acidity is responsible for most of the spring pH decline in the region. This paper compares the developments in liming policy with the scientific developments of relevance to the region during the last decade. Considerable discrepancies are noted which create opportunities for revising remediation policies to better reflect the state of knowledge in 2000.

Aluminium chemistry of the root zone of forest soil affected by acid deposition at the Lysina catchment, Czech Republic

Abstract The aluminium chemistry of soil solution in the root zone was evaluated for a spruce ( Picea abies ) forest ecosystem in the Lysina catchment underlain by base-poor granitic bedrock and impacted by acid deposition. The principal H + -buffering process in these soils is not the release of aluminium ions, although pH of soil solution is very low. The upper soil horizons are depleted of aluminium and as a consequence, the Ca/Al ratio of the soils solution is relatively high. The soil water is generally undersaturated with respect to gibbsite, aluminium-silicates and jurbanite.

BIOGEOCHEMISTRY OF ALUMINUM IN A FOREST CATCHMENT IN THE CZECH REPUBLIC IMPACTED BY ATMOSPHERIC INPUTS OF STRONG ACIDS

The Lysina catchment in the Czech Republic was studied to investigate the biogeochemical response of Al to high loadings of acidic deposition. The catchment supports Norway spruce plantations and is underlain by granite and podzolic soil. Atmospheric deposition to the site was characterized by high H+ and SO42− fluxes in throughfall. The volume-weighted average concentration of total Al (Alt) was 28 μmol L−1 in the O horizon soil solution. About 50% of Alt in the O horizon was in the form of potentially-toxic inorganic monomeric Al (Ali). In the E horizon, Alt increased to 71 μmol L−1, and Ali comprised 80% of Alt. The concentration of Alt (120 μmol L−1) and the fraction of Ali (85%) increased in the lower mineral soil due to increases in Ali and decreases in organic monomeric Al (Alo). Shallow ground water was less acidic and had lower Alt concentration (29 μmol L−1). The volume-weighted average concentration of Alt was extremely high in stream water (60 μmol L−1) with Ali accounting for about 60% of Alt. The major species of Ali in stream water were fluorocomplexes (Al-F) and aquo Al3+. Soil solutions in the root zone were undersaturated with respect to all Al-bearing mineral phases. However, stream water exhibited Ali concentrations close to solubility with jurbanite. Acidic waters and elevated Al concentrations reflected the limited supply of basic cations on the soil exchange complex and slow weathering, which was unable to neutralize atmospheric inputs of strong acids.

Three-component model of runoff generation, Lysina catchment, Czech Republic

The forested Lysina catchment is situated in an area very susceptible to acid deposition. The stream water is characterized by extremely high concentrations of total dissolved Al (volume weighted mean 66 Μmol L−1) and H+ (average pH=3.87). In a simple two-component model, the surface runoff component contributes only 6% of runoff in winter and 4% of runoff in summer. During flood episodes, the direct runoff contributes up to 20% of streamflow. There is a strong positive correlation between stream acidity and stream discharge. The observed exponential increase in streamwater acidity with discharge during high flow periods cannot be explained by the simple two-component model. A three-component model used for hydrograph separation is based on chemical and18O analysis of precipitation, soil water and runoff. It incorporates a soil water component along with groundwater and rainfall components in streamwater generation. Dissociated organic acids leached during the flow of water through the uppermost soil horizon help to balance an apparent anion deficit. The apparent anion deficit was found to increase exponentially with flow rate. Low variability in streamwaterδ18O corresponds to a high contribution of indirect components (i.e., soil and ground water) in the runoff. The soil water contribution to indirect runoff calculated from the apparent anion deficit of streamwater, varied from 0 at base flow up to 80% during floods. On average, 40% of the streamwater is derived from soil water (from 31 to 39% in winter and from 47 to 54% in summer).

Modelling long-term water yield effects of forest management in a Norway spruce forest

Abstract Intensive forest management is one of the main land cover changes over the last century in Central Europe, resulting in forest monoculture. It has been proposed that these monoculture stands impact hydrological processes, water yield, water quality and ecosystem services. At the Lysina Critical Zone Observatory, a forest catchment in the western Czech Republic, a distributed physics-based hydrologic model, Penn State Integrated Hydrologic Model (PIHM), was used to simulate long-term hydrological change under different forest management practices, and to evaluate the comparative scenarios of the hydrological consequences of changing land cover. Stand-age-adjusted LAI (leaf area index) curves were generated from an empirical relationship to represent changes in seasonal tree growth. By consideration of age-adjusted LAI, the spatially-distributed model was able to successfully simulate the integrated hydrological response from snowmelt, recharge, evapotranspiration, groundwater levels, soil moisture and streamflow, as well as spatial patterns of each state and flux. Simulation scenarios of forest management (historical management, unmanaged, clear cutting to cropland) were compared. One of the critical findings of the study indicates that selective (patch) forest cutting results in a modest increase in runoff (water yield) as compared to the simulated unmanaged (no cutting) scenario over a 29-year period at Lysina, suggesting the model is sensitive to selective cutting practices. A simulation scenario of cropland or complete forest cutting leads to extreme increases in annual water yield and peak flow. The model sensitivity to forest management practices examined here suggests the utility of models and scenario development to future management strategies for assessing sustainable water resources and ecosystem services. Editor D. Koutsoyiannis