Relationship between Norway Spruce Status and Soil Water Base Cations/Aluminum Ratios in the Czech Republic

There is a concern that soil acidification by acidic deposition, along with the resulting depletion of the labile pool of nutrient cations (e.g. Ca, Mg) and enhanced leaching of Al from soil may contribute to forest dieback. The molar ratios of Ca/Al or (Ca+Mg+K)/Al in the soil solution have been widely used as a criterion for risk of tree damage due to acidification. Intensity and quality of the crown and branch structure transformation due to formation of secondary shoots in successive series is a very sensitive indicator of long-term tree damage, and the subsequent regenerative processes. Soil water chemistry and crown structure transformation of Norway spruce were observed at 16 forest plots within the Czech Republic with the following results: parameters, expressing degradation processes in the crown (defoliation of primary structure), regeneration processes (percentage of secondary shoots) or synthetic stages of crown structure transformation showed high correlation with soil water (Ca+Mg+K)/Al ratio in organic horizons. No relationships were found for mineral horizons. The correlations between soil water and crown status parameters were considerably stronger when using the (Ca+Mg+K)/Al ratio rather than the Ca/Al ratio.     

Effects of acid deposition on tree roots in Swedish forest stands

In nitrogen-loaded areas, many forest stands show a positive growth response to the increased nitrogen input. However, with extensive soil acidification and cation leakage, damage in forest stands is frequently observed, in particular in mature forest stands. The most important soil-mediated factors which cause a reduction in fine-root growth and mycorrhizal development are: (i) high nitrogen/cation ratios and (ii) aluminium (Al) toxicity, viz. elevated Al/cation ratios, leading to an increased sensitivity of the root systems to environmental stress. Extensive data on fine-root growth in response to experimental manipulation of plant nutrients in the forest soil are available from many large-scale field experiments in Sweden. It is concluded from the data that Al toxicity should be considered as a predisposing factor for forest decline on SW Swedish sites, reducing root function and inhibiting nutrient uptake. A chronically high nitrogen deposition is furthermore likely to produce longer-lasting damage symptoms on fine roots and their function. Aluminium-induced deficiencies of important cations in the forest trees may contribute to forest decline. In SW Swedish forest stands, potassium deficiency is likely to be another important predisposing factor.     

Effects of fertilization with MgSO4 and (NH4)2SO4 on soil solution chemistry,mycorrhiza and nutrient content of fine roots in a norway spruce stand

This paper focuses on the short-term reaction of fine root and mycorrhiza on changes in soil solution chemistry following application of MgSO₄ (Kieserite) and (NH₄)₂SO₄ (ammonium sulfate). The experiments were conducted within the ARINUS Experimental Watershed Area near Schluchsee in the Black Forest (SW Germany). Yellowing of the older needles as related to Mg deficiency was the typical symptom observed within this 45 yr old Norway spruce stand. On the N treated plot the relative mycorrhiza frequency declined and the percentage of nonmycorrhizal root tips increased, whereas in the Mg fertilized plot these parameters did not differ from the control. The observed changes cannot be caused by Al, because elevated concentrations of potentially toxic Al species and extremely low Ca/A1 molar ratios appeared in the soil solution of both treatments and did not result in reduced growth of long roots as reported from solution culture experiments. Moreover, the Al content of fine roots did not increase. Therefore, it is concluded that the thresholds for Al toxicity derived from solution culture experiments with nonmycorrhizal seedlings cannot be transferred to forest stands. A direct toxic effect of elevated NH₄ ⁺ concentrations on mycorrhiza is unlikely, but cannot be excluded. Enhanced root growth due to a higher uptake of NH₄ ⁺ from soil solution may provide a more plausible explanation for the observed increase in the percentage of nonmycorrhizal root tips after N application. Even though the N content of fine roots did not increase, the diminished K content gives some indirect indication for NH₄ ⁺ uptake by the roots. This is also consistent with reduced Mg content due to NH ₄ ⁺ /Mg²⁺ antagonism. On the MgSO₄ treated plot, Mg contents of the fine roots increased thus reflecting Mg uptake by the deficient stand.     

The influence of Mg fertilization on growth and mineral contents of fine roots in (Picea abies [Karst] L.) stands at different stages of decline in NE-Bavaria

The effect of various Mg-fertilizers (MgSO₄; calcined dolomite) on root growth and mineral composition of 40 yr old Norway spruce at different sites and stages of decline was studied. Two years after fertilization, density of living fine roots of Mg-deficient trees had significantly increased on fertilized compared to non-fertilized plots. Only fertilization of calcined dolomite appeared to induce new root formation in the upper mineral soil. No such changes were observed for healthy looking trees at a second experimental site, where base saturation of the bulk soil was also low but trees were sufficiently supplied with Mg. At the third experimental site where foliar analyses reflected a luxurious Ca and Mg but an insufficient K nutrition at high Mg and Ca saturation of the bulk soil, calcined dolomite caused an increase of root growth due to a reinforced antagonism between Ca and Mg competing with K uptake. In general, at the experimental sites the fine root necromass decreased when base saturation of the bulk soil increased. The elemental contents of fine roots from the minenal soil of all three sites under investigation indicated that fine root growth in the mineral soil is strongly related to the root Ca and Mg contents. Root Ca contents seemed to be mainly a function of the Ca availability in the soil. Since there was no close relationship between fine root growth and the Ca/Al molar ratio in living fine roots, Al toxicity may not completely account for the differences in root growth and nutrition on the experimental sites.     

Relationships between symptoms expressed by Norway spruce and foliar and soil elemental status

Surveys conducted from 1987 to 1990 of Norway spruce [Picea abies(L.) Karst.] within 12 plantations across 4 northeastern states revealed symptoms of crown discoloration and defoliation on a site-specific basis. Foliar N. K. and Ca concentrations of most of the sampled trees were above deficiency ranges, while foliar Mg concentrations of most of the symptomatic trees were below the deficiency range within the plantations. Soil pH, exchangeable Mg, K, Ca, and their corresponding percent saturations in soils were lower, while soil Al concentrations were higher for most of the symptomatic trees in comparison to the healthy trees. Foliar concentrations of Mg, Ca, K, P, Al, Mn, Pb, and Zn were positively correlated with concentrations of corresponding soil elements. Knowledge of nutrient deficiency ranges may help diagnose foliar symptoms, but their exclusive use may overly simplify relationships between foliar symptoms and foliar elements. Principal component regression analysis of the data provided assessment of interactions and balances among foliar elements, and among soil elements and their possible influences on crown symptoms. Crown symptoms were not only associated with concentrations of individual elements of foliage and soils, but also associated with interactions and balances between these elements. The influences of individual soil elements on discoloration and defoliation may depend upon other elements in soils. Soil Al may induce crown discoloration and defoliation by interfering with Mg, Ca, and K uptake in acidic soils.     

The influence of Mg fertilization on growth and mineral contents of fine roots in (Picea abies [karst] L.) stands at different stages of decline in NE-Bavaria

The effect of various Mg-fertilizers (MgSO₄; calcined dolomite) on root growth and mineral composition of 40 yr old Norway spruce at different sites and stages of decline was studied. Two years after fertilization, density of living fine roots of Mg-deficient trees had significantly increased on fertilized compared to non-fertilized plots. Only fertilization of calcined dolomite appeared to induce new root formation in the upper mineral soil. No such changes were observed for healthy looking trees at a second experimental site, where base saturation of the bulk soil was also low but trees were sufficiently supplied with Mg. At the third experimental site where foliar analyses reflected a luxurious Ca and Mg but an insufficient K nutrition at high Mg and Ca saturation of the bulk soil, calcined dolomite caused an increase of root growth due to a reinforced antagonism between Ca and Mg competing with K uptake. In general, at the experimental sites the fine root necromass decreased when base saturation of the bulk soil increased. The elemental contents of fine roots from the mineral soil of all three sites under investigation indicated that fine root growth in the mineral soil is strongly related to the root Ca and Mg contents. Root Ca contents seemed to be mainly a function of the Ca availability in the soil. Since there was no close relationship between fine root growth and the Ca/AI molar ratio in living fine roots, Al toxicity may not completely account for the differences in root growth and nutrition on the experimental sites.     

Are Indicators for Critical Load Exceedance Related to Forest Condition?

The aim of this study was to evaluate the suitability of the (Ca?+?Mg?+?K)/Al and the Ca/Al ratios in soil solution as chemical criteria for forest condition in critical load calculations for forest ecosystems. The tree species Norway spruce, Sitka spruce and beech were studied in an area with high deposition of sea salt and nitrogen in the south-western part of Jutland, Denmark. Throughfall and soil water were collected monthly and analysed for pH, NO₃-N, NH₄-N, K, Ca, Mg, DOC and Al_tot. Organic Al was estimated using DOC concentrations. Increment and defoliation were determined annually, and foliar element concentrations were determined every other year. The throughfall deposition was highest in the Sitka spruce stand (maximum of 40 kg N ha^?1yr^?1) and lowest in the beech stand (maximum of 11 kg N ha^?1yr^?1). The Sitka spruce stand leached on average 12 kg N ha^?1yr^?1 during the period 1988–1997 and leaching increased throughout the period. Only small amounts of N were leached from the Norway spruce stand whereas almost no N was leached from the beech stand. For all tree species, both (Ca?+?Mg?+?K)/Al and Ca/Al ratios decreased in soil solution at 90 cm depth between 1989 and 1999, which was mainly caused by a decrease in concentrations of base cations. The toxic inorganic Al species were by far the most abundant Al species at 90 cm depth. At the end of the measurement period, the (Ca?+?Mg?+?K)/Al ratio was approximately 1 for all species while the Ca/Al ratio was approximately 0.2. The lack of a trend in the increment rates, a decrease in defoliation as well as sufficient levels of Mg and Ca in foliage suggested an unchanged or even slightly improved health condition, despite the decreasing and very low (Ca?+?Mg?+?K)/Al and Ca/Al ratios. The suitability of these soil solution element ratios is questioned as the chemical criteria for soil acidification under field conditions in areas with elevated deposition rates of sea salts, in particular Mg.     

ALUMINIUM TOXICITY AND TOLERANCE IN THREE HEATHLAND SPECIES

Arnica montana and Cirsium dissectum are characteristic species of species-rich heathlands and adjacent grasslands, which declined during the last decades in the Netherlands. It has been shown in a recent field survey that the decline of A. montana and C. dissectum might be caused by soil acidification. Calluna vulgaris is not susceptible to soil acidification. It was hypothesized that increased aluminium concentrations in the soil as a result of acidifying atmospheric inputs caused the decline of A. montana and C. dissectum whereas C. vulgaris would not be sensitive to enhanced aluminium concentrations. We studied the effects of different Al:Ca-ratios and of Al concentrations on the development of A. montana, C. dissectum and C. vulgaris in nutrient solution experiments. All three species showed aluminium accumulation in the shoots related with increased aluminium concentrations in the nutrient solutions. This accumulation was correlated with a reduction in growth when plants were cultured at high Al concentrations (200–500 µmol l^-1), in both A. montana and C. dissectum. In addition, indications of Al toxicity were observed in these plant species, e.g. poor root development, yellowish leaves and reduced contents of Mg and P in the plants. C. vulgaris did not show reduced growth or poor plant development due to high Al concentrations. The negative effects of aluminium in A. montana and C. dissectum were partly counterbalanced when plants were grown on the same Al concentrations but with increased Ca concentrations, resulting in lower Al:Ca-ratios. No effects of enhanced calcium concentrations on C. vulgaris have been observed.     

Elemental patterns in roots and foliage of mature spruce across a gradient of soil aluminium

Tissue concentrations of Al in red and Norway spruce trees were compared across 5 sites in North America and Europe as part of an investigation of Al biogeochemistry in forested ecosystems (ALBIOS). Fine roots and foliage were sampled and analyzed for Al, Ca, Mg, and P, and the chemistry of soil and soil solutions was characterized at each plot by horizon. Sites exhibited a wide range in soil Al saturation and in concentrations of Al and sulfate in lysimeter solutions. Aluminium concentrations in roots were two orders of magnitude higher than those in foliage. Fine roots (<1.0 mm) from B horizons had the highest Al concentrations and appeared to be the best phytoindicators of plant-available Al. Aluminium concentrations in fine roots from B horizons were highly correlated with soil solution monomeric Al, and with Al in 0.01 M SrC₂. soil extracts. Stronger soil Al extractants were generally poor predictors of concentrations of Al in plant tissue. Sites with higher levels of plant-available Al supported spruce trees with correspondingly lower foliar levels of Ca and Mg. As such, these field sites provided circumstantial evidence that Al may be interfering with Ca and Mg uptake and transport. No evidence was found of Al interference with P uptake or transport at these sites.     

Assessment of the Exposure and Loads of Acidifying and Eutrophying Pollutants and Ozone,as well as their Harmful Influence on the Vitality of the Trees and the Speulder Forest Ecosystem as a Whole

Within the framework of the Dutch Priority Program on Acidification, 10 yr of research was conducted in a Douglas fir stand at Speulder forest. Research was conducted to establish the loads and levels of acidifying and eutrophying pollutants and ozone, to determine forest vitality characteristics and follow growth parameters and nutrient status in time and to determine the effects of reduction of loads and levels by manipulation experiments. Results indicate that during the last 20 yr critical levels for air pollutants have hardly been exceeded except for ozone, which slightly affected assimilation. Elevated nitrogen deposition has caused several adverse effects including (i) inhibited mycorrhizal development, leading to a decreased base cation and phosphorus uptake; (ii) elevated foliage/root (fine and coarse) ratios, making the forest more sensitive to drought and windthrow; (iii) elevated nitrogen and arginine concentrations in the foliage, associated with relative base cation and phosphorus deficiency, and (iv) elevated nitrate leaching polluting the groundwater. High inputs of acidity have caused elevated ratios of Al to base cations, affecting fine root (uptake) and depletion of the readily available Al pool, thus affecting the long-term sustainability. Despite these effects, forest vitality, in terms of defoliation/discoloration, is reasonable and forest growth even increased in response to nitrogen. The exceedances of critical loads for nitrogen and acidity, however, implies a (large) risk for the long-term sustainability of the Speulder forest.     

Effects of soil acidification on foliar leaching and retranslocation of metals in vascular plants

This paper reports on the seasonal patterns in leaf metal concentrations as influenced by artificial acidification and acidification due to acid precipitation at ambient levels in Southern Norway. The effects of change in soil nutrient availability can be concealed for a long time because of ability of plants to retranslocate mobile nutrients including Cu, Mg, K, and Zn. Exceptions are, e.g., Ca and Mn which are relatively immobile in the indigenous plant species studied. It appears from this work that long-term exposure to episodes of artificial rainfall of pH 3.2, or to acid precipitation at ambient pH levels, may alter the seasonal patterns in tissue metal concentrations of vascular plants. An enhanced retention of Mg and Zn in senescent leaves of deciduous species was observed. Foliar leaching of K on exposure to acid deposition may not be adequately compensated by root uptake.     

Crown Condition and Needle Chemistry of Norway Spruce in Relation to Critical Loads of Acidity in South-East Norway

This study shows that it is questionable if critical load modelling can contribute in the search for harmful effects of acid deposition on forest health at present. Critical loads forS and N deposition were calculated using the MAGIC and PROFILE models for more than 100 monitoring plots in Norway spruce forestin south-east Norway. The two models gave different results, likely due to differences in the models, including differences in the time spans applied. The PROFILE model gave considerably more plots with exceedance than the MAGIC model.At plots where the CL was exceeded, calcium/aluminium (Ca/Al) ratios in the soil solutions were low. However, very few of theseplots had possible harmful values of the Ca/Al-ratio. More than 50 yr seems in most cases to be needed to bring Ca/Al ratios below 1.0. Present deposition was better correlated with measured forest condition variables such as crown condition and needle chemistry,than with modelled exceedance according to any of the two methods. The deposition of S and N was weakly, negatively correlated to foliar concentrations of P and Ca, and positivelyto foliar N concentrations and crown density.     

Metal uptake in plants from a birch forest area near a copper smelter in Norway

Uptake of Ca, Mg, K, Mn, Fe, Al, Rb, Ph, Cu, Zn, and Cd in vascular plants from a birch forest area near a Cu smelter in northern Norway was investigated. The primary objective was to study metal uptake in plants growing in a strong local acidification gradient. Decreased levels of Mn, Mg, and Ca found in Betula pubescens, Vaccinum myrtillus, and Deschampsia flexuosa near the smelter corresponded to a decrease in base saturation of the soil. This suggests that appreciable soil acidification has taken place. The level of Rb in Vaccinum myrtillus and Sorbus aucuparia increased significantly towards the smelter, probably due to the higher soil acidity. Elevated levels of Cu, Zn, Ph, and Cd in surface soil were found with values up to 2500 mg kg^?1 Cu within 1 km from the smelter. These concentrations decreased significantly with distance, but metal contamination was detectable up to 27 km from the smelter along the prevailing wind direction. A corresponding decrease was detected for Cu in the four plant species analyzed. Elevated levels of Zn, Ph, Fe, and Al were found in some, but not all, species.     

Effects of acid deposition on Dutch forest ecosystems

Effects of elevated S and N deposition on the solution chemistry of Dutch forest soils are mainly manifested by increased concentrations of Al associated with increased concentrations of SO₄ and NO₄. Presumed critical Al/base cation ratios are often exceeded below 20 cm soil depth. There is also evidence that elevated N deposion during the last decades affected the forest nutrient status and caused large changes in forest vegetation. About half of the Dutch forests have absolute shortage of P and relative Mg deficiencies compared to foliar N contents. Evidence from field studies of a relationship between soil acidification and nutrient imbalances in the soil and the foliage on one hand and the vitality of forests on the other hand is, however, lacking.     

Acidic deposition and its effects on the forests of Nordic Europe

Air pollution effects on the forest of Nordic Europe are analyzed with respect to the situation before and after 1980. No adverse effects were reported up to 1980. Inventories of forest vitality in terms of needle loss or crown density as well as tree growth have been made in parts of Norway and the whole of Sweden. For Norway spruce, needle loss was found to increase with tree age and climatic stress with increasing latitude and altitude. However, decreased crown density was also reported for SW Sweden. Needle loss is a non-specific signal not reacting to air pollution alone. Direct effects of gases such as SO₂ are not likely to occur, but high episodic levels of O₃ have been measured at a level possibly leading to chronic injuries. Increasing soil acidity is reported from forests in SW Sweden and also from an alpine locality in southern Norway. A differentiation of biological and deposition-dependent acidification has been attempted. A soil acidification of up to 1 pH unit has occurred in both humus and mineral soil layers. An increased release of A1 and heavy metals combined with an increased loss of basic cations is now occurring. Soil acidification probably also results in less available amounts of phosphorus and is suggested to interact with N as limiting forest growth.     

Effects of fertilization with MgSO4 and (NH4)2SO4 on soil solution chemistry,mycorrhiza and nutrient content of fine roots in a Norway spruce stand

This paper focuses on the short-term reaction of fine root and mycorrhiza on changes in soil solution chemistry following application of MgSO₄ (Kieserite) and (NH₄)₂SO₄ (ammonium sulfate). The experiments were conducted within the ARINUS Experimental Watershed Area near Schluchsee in the Black Forest (SW Germany). Yellowing of the older needles as related to Mg deficiency was the typical symptom observed within this 45 yr old Norway spruce stand. On the N treated plot the relative mycorrhiza frequency declined and the percentage of nonmycorrhizal root tips increased, whereas in the Mg fertilized plot these parameters did not differ from the control. The observed changes cannot be caused by A1, because elevated concentrations of potentially toxic A1 species and extremely low Ca/A1 molar ratios appeared in the soil solution of both treatments and did not result in reduced growth of long roots as reported from solution culture experiments. Moreover, the A1 content of fine roots did not increase. Therefore, it is concluded that the thresholds for A1 toxicity derived from solution culture experiments with nonmycorrhizal seedlings cannot be transferred to forest stands. A direct toxic effect of elevated NH ₄ ⁺ concentrations on mycorrhiza is unlikely, but cannot be excluded. Enhanced root growth due to a higher uptake of NH ₄ ⁺ from soil solution may provide a more plausible explanation for the observed increase in the percentage of nonmycorrhizal root tips after N application. Even though the N content of fine roots did not increase, the diminished K content gives some indirect indication for NH ₄ ⁺ uptake by the roots. This is also consistent with reduced Mg content due to NH ₄ ⁺ /Mg²⁺ antagonism. On the MgSO₄ treated plot, Mg contents of the fine roots increased thus reflecting Mg uptake by the deficient stand.     

Soil Aluminum Effects on Growth and Nutrition of Cacao

In acid soils, Al toxicity and nutrient deficiencies are main constraints for low yield of cacao (Theobroma cacao L.). A controlled growth chamber experiment was conducted to evaluate the effect of three Al saturations (0.2, 19, and 26%) adjusted by addition of dolomitic lime on growth and nutrient uptake parameters of cacao. Overall, increasing soil Al saturation decreased shoot and root dry weight, stem height, root length, relative growth rate, and net assimilation rate. However, increasing soil Al saturation increased leaf area, specific leaf area (total leaf area/total leaf dry wt), and leaf area ratio (total leaf area/shoot+root wt). Increasing soil Al saturation decreased uptake of elements. Nutrient influx (IN) and transport (TR) decreased significantly for K, Ca and Mg, and showed an increasing trend for S and P as soil Al saturation increased. However, increasing soil Al saturation significantly increased nutrient use efficiency ratio (ER, mg of shoot weight produced per mg of element in shoot) of Ca, Mg and K and decreased ER for other elements. Reduction of soil acidity constraints with addition of lime and fertilizers appear to be key factors in improving cacao yields in infertile, acidic, tropical soils.     

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.     

Contribution of different proton sources to pedogenetic soil acidification in forested ecosystems in Japan

The contribution of different proton sources to pedogenetic soil acidification was evaluated for three Japanese forest soils, i.e. ando soil, podzolic soil and brown forest soil in relation to the respective soil forming processes. Soil acidification rate and net proton generation were quantified based on the theory of proton budget for the respective soil horizon compartments (mainly the O, A and B horizons) by measuring fluxes of solutes entering and leaving the soil horizon compartment and vegetation uptake. Protons were produced by the dissociation of organic acids and nitrification in the O horizon and then consumed by adsorption and decomposition of organic acids and nitrate uptake by vegetation in deeper soil horizons at all plots. Excess uptake of cation over anion by vegetation was highest among proton sources in the whole soil compartment at all plots. Pedogenetic soil acidification was considered to include cation leaching from surface soil horizons due to proton generation by the dissociation of organic acids and nitrification and subsequent cation excess accumulation in wood in the growth stage of forests. In ando soil, andosolization resulted from the low contribution of net proton generation by the dissociation of organic acids as well as a lower soil acidification rate and complete acid neutralization. Dissolved organic carbon (DOC) fluxes in ando soil were lower than those in podzolic soil and brown forest soil due to high adsorption capacity of amorphous materials. In podzolic soil, podzolization resulted from intensive acidification in the O horizon, which derived from net proton generation by the dissociation of organic acids and nitrification as well as cation excess uptake by vegetation due to concentrated fine root biomass in the O horizon, and subsequent high proton efflux to subsoil. The high fluxes of DOC and Al leached from surface soil horizons were considered to contribute to eluviation of Al from surface soil and illuviation in subsoil in podzolic soil. In brown forest soil, brunification resulted from a lower DOC flux from the O horizon due to high decomposition and adsorption by oxides, where podzolization was weakened by high acid neutralization. Thus, the three representative processes involved in the pedogenesis of Japanese forest soils were well characterized by quantification of the respective proton-generating and consuming processes in each soil horizon.     

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.