Podzolic Forest Soils Research Articles

Naming the untouchable \u2013 environmental sequences and niche partitioning as taxonomical evidence in fungi

ABSTRACTDue to their submerged and cryptic lifestyle, the vast majority of fungal species are difficult to observe and describe morphologically, and many remain known to science only from sequences detected in environmental samples. The lack of practices to delimit and name most fungal species is a staggering limitation to communication and interpretation of ecology and evolution in kingdom Fungi. Here, we use environmental sequence data as taxonomical evidence and combine phylogenetic and ecological data to generate and test species hypotheses in the class Archaeorhizomycetes (Taphrinomycotina, Ascomycota). Based on environmental amplicon sequencing from a well-studied Swedish pine forest podzol soil, we generate 68 distinct species hypotheses of Archaeorhizomycetes, of which two correspond to the only described species in the class. Nine of the species hypotheses represent 78% of the sequenced Archaeorhizomycetes community, and are supported by long read data that form the backbone for delimiting species hypothesis based on phylogenetic branch lengths.Soil fungal communities are shaped by environmental filtering and competitive exclusion so that closely related species are less likely to co-occur in a niche if adaptive traits are evolutionarily conserved. In soil profiles, distinct vertical horizons represent a testable niche dimension, and we found significantly differential distribution across samples for a well-supported pair of sister species hypotheses. Based on the combination of phylogenetic and ecological evidence, we identify two novel species for which we provide molecular diagnostics and propose names. While environmental sequences cannot be automatically translated to species, they can be used to generate phylogenetically distinct species hypotheses that can be further tested using sequences as ecological evidence. We conclude that in the case of abundantly and frequently observed species, environmental sequences can support species recognition in the absences of physical specimens, while rare taxa remain uncaptured at our sampling and sequencing intensity.

Модельная рекультивация <i>ex situ</i> и оценка ферментативной активности лесных подзолистых почв в условиях повышенного нефтяного загрязнения

Модельная рекультивация <i>ex situ</i> и оценка ферментативной активности лесных подзолистых почв в условиях повышенного нефтяного загрязнения

Post-pyrogenic changes in the properties of grey forest podzolic soils of ecogeosystems of pine forests under conditions of anthropogenicloading

This article presents the analysis of results of experimental data of postpyrogenic change of soils of ecological systems of pine forests.Ground fires transform the surface organogenic horizons of soils. The negative influence of low-intensity fires of different intensity on the change of humus stock, qualitative fractional composition of organogenic soil horizons and their chemical composition is shown.Post-pyrogenic transformations of physical and chemical soil characteristics are found, which are not simply their corresponding reaction to the pyrogenic effect, but a clear signal reflecting the state of the soil immediately after the fire, taking into account its strength and intensity, and after a certain period of time. There is a certain dependence of the degree of pyrogenicity on the duration of the effect of fire on the soil. The recent influence of a medium intensity fire on the soil is marked by a clear reaction of the complex of its properties.Physical and chemical properties of soils after fires deteriorate: humus burns, the content of nitrate nitrogen decreases.Forest fires sharply change the morphological state of the upper part of the soil profile. The nature of the surface horizons of soils changes, a new pyrogenic horizon is formed, which differs from natural analogues in terms of physical and chemical properties and the content of ash elements. Under the influence of fire there are changes in such properties as: pH, content of exchange cations, gross and moving forms of nitrogen, etc.The heavy metal concentration in surface horizons increases several times and exceeds the background values due to the mineralization of forest litter and herbaceous vegetation from the combustion and subsequent migration of chemical elements , which presents an environmental hazard.The change in the chemical composition of soils can create conditions for the impossibility of the existence of a root ecosystem, its death, and development, after a certain time, of another modified ecogeosystem.

Using short-lived nuclides of the U- and Th-series to probe the kinetics of colloid migration in forested soils

The recent chemical dynamics of a podzolic forest soil section (from the Strengbach watershed, France) was investigated using U- and Th-series nuclides. Analyses of ( 238U), ( 230Th), ( 226Ra), ( 232Th), ( 228Ra) and ( 228Th) activities in the soil particles, the seepage waters, and the mature leaves of the beech trees growing on this soil were performed by TIMS or gamma spectrometry. The simultaneous analysis of the different soil ( sl) compartments allows to demonstrate that a preferential Th leaching over Ra must be assumed to explain the ( 226Ra/ 230Th), ( 228Ra/ 232Th) and ( 228Th/ 228Ra) disequilibria recorded in the soil particles. The overall Ra- and Th- transfer schemes are entirely consistent with the prevailing acido-complexolysis weathering mechanism in podzols. Using a continuous open-system leaching model, the ( 226Ra/ 230Th) and ( 228Ra/ 232Th) disequilibria measured in the different soil layers enable dating of the contemporary processes occurring in this soil. In this way, we have determined that a preferential Th-leaching from the shallow Ah horizon, due to a strong complexation with organic colloids, began fairly recently (18 years ago at most). The continual increase in pH recorded in precipitations over the last 20 years is assumed to be the cause of this enhanced organic complexation. A lower soil horizon (50–60 cm) is also affected by preferential Th leaching, though lasting over several centuries at least, with a much smaller leaching rate. The migration of Th isotopes through this soil section might hence be used as a tracer for the organic colloids migration and the induced radioactive disequilibria demonstrate to be useful for assessing the colloidal migration kinetics in a forested soil. Ra and Th isotopic ratios also appear to be valuable tracers of some mineral-water–plant interactions occurring in soil. The ( 228Ra/ 226Ra) ratio enables discrimination of the Ra flux originating from leaf degradation from that originating from mineral weathering in shallow −10 cm seepage soil waters. It appears that, at least in some cases, the Ra-isotopic ratio measured in forest-soil seepage waters may not be representative of the Ra-isotopic ratio released from mineral weathering, indicating that the different origins of the dissolved 226Ra and 228Ra must be taken into account.

Lead isotope distribution in podzolic soil profiles on different types of bedrock in a formerly glaciated terrain (Oslo, Norway)

Abstract Lead has been exploited by man over thousands of years for a variety of metallurgical, medicinal, and industrial purposes. The cumulative output of Pb from mining is estimated to be 260 million metric tonnes and 85% of this has occurred over the last two centuries. Global annual production of Pb from mining was about 3 million tonnes at the turn of the millenium. Terrestrial ecosystems all over Norway have been contaminated moderately to strongly by Pb and other trace elements from atmospheric deposition. With the aim of developing a method for mapping the accumulated content of anthropogenic Pb and how deep in the soil profile the atmospherically deposited Pb has penetrated, the concentration of Pb and the 206Pb/207Pb ratio has been studied in podzolic forest soils at four locations with different lithology, i.e. age and type of bedrock, in the Oslo area. The concentrations of Pb in the soil profiles are 6.6–38.1 mg/kg (median 10.3). The 206Pb/207Pb ratio ranges between 1.168 and 1.314 (median 1.267) over the entire profile. In the upper 5 cm the range is 1.168–1.191, similar to ratios determined in recent atmospheric deposition. Applying three different methods, the amount of anthropogenically deposited Pb is estimated at 1–6 t/km2.

Dynamics of simple carbon compounds in two forest soils as revealed by soil solution concentrations and biodegradation kinetics

Simple compounds in soil such as organic acids, amino acids and monosaccharides are believed to be important in regulating many aspects of terrestrial ecosystem functioning (e.g. C cycling, nutrient acquisition). Understanding the fate and dynamics of these low molecular weight (MW) compounds is therefore essential for predicting ecosystem responses to disturbance. Our aim was to quantify the amounts of these compounds in two podzolic forest soil profiles (O, E, Bs and C horizons) and to quantify their contribution to total soil respiration. The total concentration of organic acids, amino acids and monosaccharides in soil solution comprised on average 15 ± 10% of the total dissolved organic C (DOC), with declining concentrations in the deeper soil layers. Dissolved organic N (DON) was the dominant form of N in soil solution and free amino acids contributed to 34% of this pool. The mineralization behaviour of glucose and galactose was described by parabolic (Michaelis–Menten) type kinetics with V max and K M values in the range of <1–250 μmol kg−1 h−1 and 15–1,100 μM, respectively. Assuming that (1) microbially mediated substrate turnover follows Michaelis–Menten kinetics, and (2) steady state soil solution concentrations, we calculated the rate of CO2 efflux attributable to the mineralisation of the three classes of low MW compounds. Our results indicated that in the O horizon, the turnover of these substrates could comprise ~100% of the basal, heterotrophic, soil respiration. In contrast, in the deeper mineral soil <20% of total soil respiration could be attributable to the mineralization of these compounds. Our compound-specific approach has identified the main substrates contributing to soil respiration in forest topsoils. However, our results also suggest that soil respiration in subsoils may be attributable to compounds other than organic acids, amino acids and monosaccharides.

Heavy Metal Concentrations in Soil Solution, Soil and Needles in a Norway Spruce Stand on an Acid Sulphate Forest Soil

The effects of soil processes, related to the oxidation of sulphide sediments, on heavy metal concentrations in the soil and soil solution were investigated in a Norway spruce stand on a fine-textured, acidic soil rich in sulphates located on the isostatic land-uplift western coast of Finland. The age of the soil is ca. 300–400 years, and the soil texture is silt and till. The chemical properties of the soil and soil solution clearly reflected the formation of acid sulphate (AS) soil. Compared to background reference values for podzolic coniferous forest soil, the pH of the soil solution in the mineral soil (20–40 cm depth) was very low, and the Al, Fe and S concentrations extremely high. The Zn and Ni concentrations in the soil solution were also strongly elevated, and similar to the concentrations reported close to anthropogenic heavy-metal emission sources. The concentrations of Cd and Cu were also frequently elevated. In contrast, the acidity and metal concentrations of the soil solution sampled in the organic layer were not elevated. Similarly, exchangeable Zn and Ni concentrations were also elevated in the mineral soil, but not in the organic layer. Because Norway spruce has a very superficial rooting system and the zone with exceptionally high metal concentrations did not extend up to the topmost soil layers, sulphide-oxidation derived soil acidification is not likely to pose a serious threat to forest ecosystems growing on this type of site. Despite the elevated concentrations of protons and many metals in the mineral soil and soil solution (20–40 cm), the nutrient status of the spruce stand was satisfactory and the general health of the stand has been reported to be relatively good.

Quantification of Hydroxamate Siderophores in Soil Solutions of Podzolic Soil Profiles in Sweden

Concentrations up to 2 and 12 nM of the hydroxamate siderophores ferrichrome and ferricrocin, respectively, were identified in soil solutions of podzolic forest soils at four sites in both northern and southern Sweden. No ferrichrysin was detected. As with the dissolved organic carbon and low molecular mass organic acids, the highest concentrations of the siderophores were found in the upper layers i.e. the mor layer, the eluvial and upper illuvial horizons. At the southern sites, the concentrations of ferrichrome and ferricrocin were both of similar magnitude and did not differ between the two sites. In contrast, soil solutions at the two northern sites contained more ferricrocin than ferrichrome; the ferricrocin concentrations were also higher at the northern sites than at the southern sites. Analyses were performed by high performance liquid chromatography with a porous graphitic carbon column on which ferrichrome, ferricrocin and ferrichrysin were separated. Detection by electrospray ionization mass spectrometry (ESI-MS) combined with on-line sample pre-concentration, by means of column-switching, enabled detection limits of 0.1-0.2 nM for ferrichrome, ferrichrysin and ferricrocin. The structural identities of the siderophores were further verified by MS/MS fragmentation. Fragmentation of ferrichrome, ferricrocin and ferrichrysin occurred mainly via peptide cleavage. The most intense fragments were typified by the loss of one of the three iron(III) chelating hydroxamate residues, i.e N(5)-acyl-N(5)-hydroxy ornithine.

Quantification of Pollutant Lead in Forest Soils

Fifteen podzolic forest soils in Norway covering sites with a wide range of atmospheric deposition rates were assayed for their contents of pollutant Pb. Samples from the Of, Oh, E, B, and C horizons were studied. Nitric acid soluble contents of Pb and the corresponding stable Pb isotope ratios were determined by sector field inductively coupled plasma–mass spectrometry (ICP–MS). On the basis of existing knowledge on 206Pb/207Pb ratios in atmospheric deposition over Norway across time, the percentage of the Pb supplied by air pollution was calculated for the various samples and soil horizons, assuming that the C horizon was undisturbed. More than 90% of O horizon Pb was from pollution, even at remote sites in the far north. Significant fractions of Pb were pollution‐derived also in the E and B horizons at most sites. In the south, more than half of the Pb derived from air pollution has now moved to the upper mineral horizons. Stable Pb isotope ratios are a very precise tool for revealing Pb pollution in terrestrial ecosystems. The present work suggests that similar studies should be done in other parts of the world to objectively assess the anthropogenic contribution to surface soil Pb.

Column Leaching using Dry Soil to Estimate Solid-Solution Partitioning Observed in Zero-Tension Lysimeters. 2. Trace Metals

The fundamental questions revolving around research into trace metals in soils are how much, and in what form, do metals exist in soil solutions. The mobile phase of soil solutions can be sampled by lysimeters, but cannot be consistently and accurately reproduced in laboratory extractions. We used a column leaching method developed specifically to produce solutions that were similar to those of lysimeters from northern forest podzolic soils. We hoped to yield reasonable estimates of the partitioning of Cd, Cu, Ni, Pb and Zn between the solid and solution phases observed in the field. The column leaching method produced solutions that were similar to lysimeter solutions in the concentrations of metals in solution. Partitioning coefficients (log Kd) calculated from average lysimeters solution concentrations ranged from 2.8 to 3.9 for Cd, 3.5 to 4.2 for Cu, 3.1 to 4.3 for Ni, 3.9 to 5.1 for Pb and 2.8 to 3.6 for Zn. Laboratory extractions produced very similar log Kd values ranging from 3.4 to 3.9 for Cd, 3.4 to 3.9 for Cu, 3.4 to 4.1 for Ni, 4.1 to 5.2 for Pb and 3.2 to 3.5 for Zn. According to a semi-mechanistic regression model based on observed lysimeter concentrations, the metal concentrations in solution were appropriate relative to known factors that influence metal partitioning in soils: pH and the concentrations of total metals and dissolved organic carbon. Partitioning coefficients based on laboratory extractions in the literature were on average an order of magnitude greater than those observed in lysimeters. When compared to the results of other laboratory extractions, the proposed extraction procedure appeared to be an effective method to estimate the chemistry of soil solutions in the field.

The wood-decaying fungus Hygrophoropsis aurantiaca increases P availability in acid forest humus soil, while N addition hampers this effect

We evaluated the influence of the brown rot fungus Hygrophoropsis aurantiaca on P solubility in the humus layer of a podzolic forest soil. This fungus is known to exude large amounts of oxalic acid that may stimulate weathering of minerals and increase dissolution of humus, which in turn may increase P availability in the soil surrounding the fungus. Humus was inoculated using small wooden pieces colonised by the fungus. The presence of the fungus resulted in elevated concentration of PO4− in the humus solution. In a second experiment birch seedlings grown in the same humus were able to utilise the PO4− mobilised by the fungus to increase their internal P content. The factor determining this increased P uptake and the increased available P might be oxalate produced by fungus. The acid may directly dissolve P or change organic forms of P making it more susceptible to reaction with phosphatases. This fungal effect on P solubility diminished when N was added to the soil in the form of a slow release N fertilizer (methyl urea), or when a soil with a higher soil N concentration was used. We found a strong correlation between NH4+ concentration and total organic carbon in the soil solution at high NH4+ concentrations, suggesting the dissolution of humus as a result of the high NH4+ content in the solution. This study demonstrates that the wood-decaying fungus H. aurantiaca influences nutrient turnover in forest soil, and thereby nutrient uptake by forest trees. An intensified harvest of forest products such as whole tree harvesting may decrease the active biomass of the wood decomposers and may thereby change the availability of P and the leaching of N.

The amount of secondary Al in two ploughed podzolic forest soils

In ploughing of coniferous forest soils the soil profile down to the illuvial B horizon is inverted on a soil surface. As a result, aluminium once immobilized in the B horizon during podzolization might start to remobilize. In order to test this hypothesis, selective extractions with dithionite-citrate (d), acid ammonium oxalate (o) and sodium pyrophosphate (p) were used to determine amounts of Al in a ploughed podzolic profile and compared with those of the corresponding undisturbed profile in two forest soils tilled 17 (site K1) and 31 (site K2) years ago. Amounts of oxalate and dithionite-citrate extractable Al in the exposed Bs horizons of the tilt and furrow were lower than in the corresponding undisturbed soil at site K1 suggesting that mobilization of Al had occurred. Since amorphous Al (Alo-Alp), in particular, had decreased released Al most probably originated from imogolite-type materials. Concurrently, the amount of total carbon in these exposed horizons had increased whereas soil pH(CaCl 2) decreased implying that mobilization of Al was most likely accelerated by ecosystem internal processes such as organic acids excreted by roots and released during decomposition. Increased amounts of amorphous Al deeper in the tilt suggest that released Al had most probably migrated downward until reprecipitated. Migration and subsequent retention to organic matter might also explain the high amounts of organically bound Al (Alp) in the double humus layer buried beneath the tilt. At site K2, the changes in amounts of Al in the tilt were not as obvious as those observed at site K1. The high amounts of organically bound Al in the double humus layer and amorphous Al in the Bs horizon beneath the tilt, however, support that some mobilization of Al has occurred at site K2.

Biodegradation of low molecular weight organic acids in coniferous forest podzolic soils

Organic acids have been hypothesised to play a central role in long-term soil pedogenic processes such as podzolisation and also in short-term rhizosphere processes such as nutrient mobilisation. Their spatial and temporal patterns in soil, however, are poorly understood. This study was designed to quantify the rate of microbial decomposition of three low molecular weight organic acids (citrate, oxalate and acetate) as a function of soil depth (O, A, E, B and C horizons) in three podzolic coniferous forest soils and to assess their contribution to total soil CO 2 fluxes. Soil solution extraction indicated that generally, most organic acids were present in the highest concentration in surface O horizons (10–100 μM) declining with soil depth. Correspondingly, the rate of organic acid mineralisation was also greatest in the surface organic horizons. In contrast, the mineral horizons possessed low rates of biodegradation which appeared not to be due to a lack of microbial activity but moreover due to strong sorption to the solid phase preventing microbial uptake. Concentration-dependent mineralisation experiments indicated that decomposition could be adequately described by a single Michaelis–Menten kinetics equation. The results showed that generally most horizon samples had the greatest mineralisation capacity for citrate or oxalate ( V max=<1–340 nmol g −1 h −1) in comparison to acetate. The V max values typically declined with soil depth. K M values ranged from 10 to 7000 μM, however, if adsorption was accounted for the K M values decreased (<1–5000 μM) especially in B horizons. Calculations of the contribution of organic acids to total soil respiration indicated that between <0.1 and 47% of total CO 2 production from an individual horizon could be accounted for by organic acid mineralisation alone. The findings are discussed in the context of soil forming and rhizosphere processes.

Controlling mechanisms of aluminium in soil solution – an evaluation of 180 podzolic forest soils

To monitor the level of soil acidification in the county of Värmland in the middle west of Sweden 180 podzolic forest soils were investigated. Soil solutions from four horizons were obtained by centrifugation and the soil was sampled for a determination of the exchangeable pool by extraction. The concentrations of inorganic Al and its fraction of the total Al in solution were greater in the south of the county (up to 50%). The factors influencing the total Al and free inorganic Al 3+ in the soil solutions were evaluated. Saturation indices (SI) for five different mineral phases were calculated but none implied equilibrium conditions. The relationships between pAl 3+ and pH (in the pH range 4–6.2) gave slopes of about 1, which indicated that ion exchange/complexation reactions may be important for determining the Al 3+ concentration in the B and C horizons. In the E horizon solutions complexation with soluble organic acids seemed to be the major factor which influenced the Al 3+ activity. The influence of organic matter on Al solubility was supported by partial least square (PLS) regressions.

Mobility and Methylation of Mercury in Forest Soils Development of an In-Situ Stable Isotope Tracer Technique and Initial Results

A method for investigating in-situmethylation and mobility of mercury has beendeveloped and applied to forest soil. The methodis based on additions of stable 199Hgisotopes to forest soil plots followed bysampling and analysis of isotope ratios of totalmercury and MeHg using ICP-MS. Initial resultsindicate that a fraction (30%) of the mercuryadded to the forest soils is immobilised over atime scale of 16 months. A small but significantfraction of the mercury is methylated during thesame time scale. Higher methylation rates werefound in wetland soil than in dry forest podzolsoil.

Fixation of radiocaesium in an acid brown forest soil

SummaryThe OAh and Ah horizons of acid brown and podzolic forest soils are reported to fix more radiocaesium than the mineral B horizons beneath them. We determined the respective influence of organic matter and clay minerals on the magnitude of Cs+ retention in a strongly acid brown forest soil in Belgium. The soil contained mica throughout the profile. Vermiculite was identified in the OAh and Ah horizons, and hydroxy interlayered vermiculite (HIV) in the Bw horizon. The OAh and Ah clay fraction retained much more Cs+ than the Bw horizon. The extraction of Al interlayers by Na‐citrate resulted in a marked increase in Cs+ fixation in the Bw clays as well as the collapse of the vermiculitic layers after K+ saturation. Organic matter had a strong but indirect effect on Cs+ fixation. In the Bw horizon, acid weathering of layer silicates releases free Al and produces HIV minerals in which Al polymers block the access of radiocaesium onto Cs+‐specific sites. In OAh and Ah horizons, free Al is complexed by organic acids. Consequently, the interlayer specific sites remain accessible for Cs+ fixation.

Apparent cation‐exchange equilibria in podzolic forest soils

SummaryThe Gaines–Thomas selectivity coefficient, K, was used to express the relation between the cations in solution and the cations in exchange sites in podzolic forest soils. Soil solution was obtained by centrifuging a fresh bulked soil sample. Exchangeable cations HX, AlX, CaX, MgX and KX and effective cation‐exchange capacity, CECe, were determined with 0.1 m BaCl2. Apparent values of K indicated a preference of Ca2+ over Mg2+ and over Al3+ in O, A and B horizons (log KAl–Ca &lt; 0 and log KMg–Ca &lt; 0), whereas log KK–Ca and log KH–Ca exceeded zero. The horizons were similar with respect to log KH–Ca, and the differences in log KMg–Ca were small. Log KK–Ca and log KAl–Ca increased in the horizons in the order O &lt; A &lt; B. Log KAl–Ca was not significantly correlated with the fraction AlX/CECe. Log KMg–Ca was positively correlated with the fractions HX/CECe and AlX/CECe, and negatively correlated with log (CaX/MgX). The selectivity coefficient of binary cation exchange seemed to be applicable to in situ soil solutions. However, the fraction of each cation on exchange sites should be based on the CECe rather than on the sum of the two cations. The latter, also, seemed to be acceptable in cases of exchangeable cations with a large relative content in soil, e.g. in Al3+–Ca2+ exchange in A and B horizons, and in H+–Ca2+ exchange in O and A horizons.

Techniques for preserving and determining aluminium fractions in soil solution from podzolic forest soils

The purpose of the study was 1) to determine techniques for minimising the effects of transportation and storage on the concentrations of different A1 fractions in soil solution samples, and 2) to determine a suitable method for analysing monomeric A1 concentrations in water samples from humus-rich podzolic soils. Aluminium fractionation was performed on a cation exchange column and the fractions were analysed by ICP/AES and FIA. A time lag of a few hours to two days between sampling and pretreatment appeared to have no effect on total A1 concentrations, even though the samples were not preserved with acid. Freezing the samples was not an appropriate storage technique because it resulted in a strong decrease in total A1 concentrations. Storage (+4°C) had a detrimental effect on the proportion of exchangeable monomeric A1, but this problem was overcome by fractionating the samples immediately on arrival at the laboratory. Adjustment of sample pH to <3.7 permitted storage of the fraction for at least 2 weeks before analysis by ICP/AES or FIA. Either of these two techniques can be used for determining exchangeable monomeric A1, but if the non-exchangeable reactive A1 fraction (i.e. organically complexed A1) is required then analysis by FIA is necessary.

Copper and nickel mobility in podzolic forest soils subjected to heavy metal and sulphur deposition in Western Finland

The distribution of copper and nickel down the soil profile has been investigated at 4 plots along a heavy metal and sulphur gradient extending for a distance of up to 8 km from a copper smelter in Western Finland. Emissions from the smelter have earlier been at a relatively high level, but were considerably reduced at the beginning of the 1990's prior to the start of the experiment. Soil samples were taken in 1991, and soil water quality has been monitored using zero-tension lysimeters (5, 20 and 40 cm depth) during the growing season in 1992–1994. The organic layer and mineral soil on the plot nearest to the smelter contains considerable amounts of Cu and Ni. The Cu/Ni ratio in the organic layer was much higher than that in the underlying mineral soil, indicating that Cu is more strongly adsorbed in the organic layer than Ni. Copper concentrations in percolation water showed a peak at 20 cm depth, while for Ni the concentrations at 40 cm were higher than those at 5 cm. The lower Cu and Ni concentrations at 5 cm depth could be signs of a gradual detoxification of the surface, i.e. the gradual leaching of the mobile Cu and Ni components down to greater depths.

Simulated effects of acid deposition on podzolic soils: Consequences of process and parameter aggregation

Solution cation concentrations and base cation leaching were simulated for a homogenous soil block and a soil showing five horizons of a podzolic forest soil. The dynamic model ACIDIC simulated water flow, nutrient uptake for tree growth, and cation exchange between H+, Al3+, Ca2+, Mg2+ and K+ in forest soil. In the multi-layer simulations exchangeable base cation concentrations changed most in the O horizon. The subsoil had a decisive effect on the pH of the runoff and base cation leaching from the soil. The one-layer model underestimated Ca and Mg leaching and overestimated H+ and Al concentrations in the runoff. In the eluvial and the top of illuvial horizon the solution Al / (Ca + Mg) ratio exceeded that in one-layer structure more than 10-fold. Cases with the horizon-specific cation exchange coefficient values and mean coefficient values for all layers showed only minor differences in Al / (Ca + Mg) ratio. The vertical variation in the soil chemical properties should be accounted for even if some details of processes and parameters were unavailable.