Long-term soil acidification leads to lower pH values and to a concomitant decrease in base saturation (BS). The relationship between pH and base saturation (BS) in acidified forest soils can be disturbed by processes such as nutrient cycling by vegetation, temporary saturation by ground water that comes into contact with calcareous material, or by upward diffusion of base cations from deeper horizons. This paper examines the relationship between pH and BS in Swiss forest soils developed from calcareous and noncalcareous parent material and identifies some of the factors that can affect the BS in the decalcified parts of soils derived from calcareous parent material. The decalcified zone in the latter soils has a higher BS on average compared to soils from noncalcareous parent material, but their pH values are identical. In the pH range 4.0-4.5, the difference in BS may vary by a factor of three. The mean BS in the decalcified zone tends to decrease with increasing depth of the calcareous layer. The water regime also affects the BS in soils on calcareous parent material. In soils temporarily saturated by groundwater (gleysols), the BS in the decalcified zone is always high (85%-100%) because of the continuous contact between the soil water and the calcareous parent material. In addition, the inhibited drainage impedes the depletion of base cations in these soils. In contrast, soils that are temporarily saturated by rainwater are depleted in base cations due to the alternating wetting-and-drying regime and the associated leaching of dissolved ions. In such soils, the depletion of base cations is strongly related to the extent of hydromorphy. Stagnogleyic soils, with the longest period of water saturation, have the highest depletion levels. We conclude that in such soils, the diffusion of base cations from deeper zones is strongly compensated by leaching from the very acidic soil horizons. The pH-base saturation anomaly has consequences for some of the methods used to calculate the critical loads of acidity for forest soils in Switzerland, with many soils being less sensitive than previously reported.

Soil chemical parameters related to soil acidity were determined for 1450 soil samples taken from individual mineral soil horizons in 257 forest soils in Switzerland, 196 developed from car-bonate-containing and 61 from carbonate-free parent material. The distribution of pH values and exchangeable base cations in corresponding pH ranges were related to the capacity and rate of buffer reactions in the soil. Based on this, five acidity classes for individual soil samples were defined.To describe and classify the status of soil acidity and base saturation (BS) of an entire soil body, the pH and the BS of the total fine earth in the soil were calculated from the pH and BS, respectively, of the individual soil horizons and the estimated volumetric content of fine earth.The status of soil acidification of soil profiles was assessed primarily using the total amount of exchangeable acidic cations in percent of the CEC of the fine earth in the entire soil profile. As a second factor, the gradient between the acidity class of the most acidic soil horizon and the estimated acidity class at the beginning of soil formation was used. The application of these classification schemes to our collection of soil profiles revealed the great influence played by the type of parent material. The acidification status of most soils on carbonate-containing parent material was classified as very weak to weak, whereas soils on carbonate-free parent material were found to be strongly to very strongly acidified.In terms of parent rock material, microclimate, and natural vegetation, the results of this study and the proposed classification schemes can be considered appropriate for large parts of Europe.

In the context of pollution-control strategies to minimize the detrimental effects of soil acidification, there is a need to know how and to what extent soils respond to acidifying substances. The purposes of this study were to assess the sensitivity of soil to acidification, in particular to a decrease in pH and in base saturation (BS), and the risk of Al toxicity for vulnerable plants using chemical indicators. These indicators were derived from soil data (pH, exchangeable cations, amount of fine earth) measured in the mineral horizons of 257 soil profiles throughout Switzerland. Based on the analysis of the distribution of pH and BS values in the soil collective, we assessed the sensitivity of soils to a decrease in pH and in BS. Soils that were considered sensitive to a decrease in pH had pH values between 4.8 and 7.0. The degree of sensitivity was estimated with the proportion of fine earth in the critical pH range to a depth of 100 cm. Soils that were considered sensitive to a decrease in BS had pH values between 3.6 and 5.5 and a BS between 10% and 95%. Since the effective cation-exchange capacity (CECeff) of the fine earth might dampen the decrease in BS when acidity is added, the disposition for a decrease in BS was related to the relative amount of fine earth in the sensitive BS and to the mean CECeff of this fine-earth fraction. The risk of Al toxicity for vulnerable plants was estimated using the ratio of base cations to Al at the cation-exchange sites (BC : Al-exd. A BC : Al-exc of 0.2 was taken as a threshold value below which the risk for sensitive plants increases. The degree of risk was based on the proportion of fine earth in the critical BC : Al range (<= 0.2) in the soil profile. These indicators taking into account the various aspects of soil acidification are derived from usually available data and represent therefore a cost-effective tool to assess the sensitivity of soils to an input of acidity.

In this study we compared indicators of Cd bioavailability (water extracts, Lakanen extracts, free ions) and ecotoxicity in forest soils with contrasting physico-chemical characteristics. Soil samples were treated with CdCl(2) solutions (0, 0.1, 1, 10 and 100 mM) and incubated for 30 days. Microbial activity indexes (acid phosphatase, beta-glucosidase, basal respiration) and changes in bacterial community structure using terminal restriction fragment length polymorphism (T-RFLP) fingerprinting were investigated. The Cd concentrations measured ranged from 1% to 37% of the total additions in water extracts, to higher levels in Lakanen extracts. Effects of Cd were observed at bioavailable concentrations exceeding United Nations/European Economic Commission UN/ECE guidelines for total Cd in the soil solution. Basal respiration was the most affected index, while enzymatic activities showed variable responses to the Cd treatments. We also noticed that soils with pH higher than 6.7 and clay content higher than 50% showed inhibition of basal respiration but no marked shift in bacterial community structure. Soils with lower pH (pH <5.8) with less clay content (<50%) showed in addition strong changes in the bacterial community structure. Our results provide evidence for the importance of relating the effects of Cd on the soil communities to soil properties and to bioavailability.

Abstract We investigated the occurrence and effective mobility of heavy metals (HM) in a representative collective of Swiss forest soils. The total HM contents of pedogenetic horizons were analysed, and the enrichment or depletion of a given HM relative to the original lithogenic content was assessed. The latter was calculated using the contents of Zr as an immobile reference. Chromium, Ni, Cu and Zn were mainly lithogenic, with a wide range of contents reflecting the diverse geology of Switzerland, while anthropogenic input of Pb was detected in most topsoils. Pedogenetic processes exerted a strong influence on the translocation or leaching of the HM. In acidic soils Ni, Cu and Pb were more mobile than Cr and Zn. We relate this behaviour to the strong affinity of the former HM to dissolved or colloidal organic matter. On the other hand, nutrient cycling by the vegetation probably led to an apparent reduction of Zn downward mobility. In many soils, guide levels as specified by Swiss legislation, or threshold values for effects on micro-organisms, were exceeded, indicating a potential risk for long-term soil fertility. As a consequence of translocation, guide levels for Cr, Ni and Cu were exceeded more often in subsoils than in topsoils.

Fur eine Ubersicht uber die Schwermetallbelastung der Schweizer Waldboden bestimmten wir an 95 ausgewahlten Waldstandorten in Zusammenarbeit mit der EMPA in verschiedenen Bodentiefen die Gehalte von Chrom, Nickel, Kupfer, Zink und Blei. Die Resultate zeigen, dass Richtwerte der schweizerischen Verordnung uber Belastungen des Bodens und kritische Gehalte fur Wirkungen auf Mikroorganismen haufig uberschritten werden. Das Risiko einer Grundwasserbelastung ist regional unterschiedlich.

Soils in Switzerland are protected by the environmental protection law. The ultimate purpose of the ordinance relating to impacts on the soil (OIS), dating from July 1998, is the long-term preservation of soil fertility.Soil contamination by hazardous inorganic substances is assessed according to a three-tier system, defined by guide, test and remediation values. All trace elements listed in the OIS are components of natural bedrock, occurring in any soil. The guide values refer strongly to the soil fertility,as defined in the ordinance. However,in contrast to the soil fertility, which is related to the site and soil conditions, the guide values are valid for all sites and soil uses. This makes it difficult to justify the measures to be taken (i.e. preventive emission control) once the guide values have been exceeded. Such measures make sense only if we can distinguish between the natural and the anthropogenic origins of the contaminants. Alternatively,the soil protection could be based on the test or remediation values mentioned above. Presently,however,the database in the OIS is too limited for such a change. This implies further research in the fields of soil chemistry and effect-oriented biology.

In the framework of the second Swiss forest soil inventory, 137Cs-activity from 172 sites was measured systematically for the first time in the topmost soil layer (0–5 cm) and represented on a map. The spatial distribution of 137Cs contamination was similar to the pattern observed in 1986 from dose equivalent measurements following the Chernobyl nuclear power plant accident. Forest soils from regions with high precipitation in 1986 showed a higher 137Cs activity than regions with low precipitation. At sites with high caesium activities it was possible to discriminate between 137Cs originating from global fallout of the fifties and sixties and 137Cs from the Chernobyl accident. The results indicate that radiocaesium persists in the top soil layers and is recycled in forest ecosystems.

Most of the inorganic materials designated as pollutants in soil are trace elements that occur naturally in all soils in a wide range of concentrations. They are considered harmful only where their concentrations exceed certain threshold values. In most cases there is no method that specifically characterizes these elements according to their origin. An assessment of inorganic pollution, based on total element concentrations of top-soil samples only, is therefore almost impossible. More promising results can be obtained using radio isotope techniques or from chemical analysis of entire soil profiles. The latter approach is demonstrated in a case study with lead, extracted with nitric acid and NH4-acetate-EDTA from soil samples collected by horizons in 100 profiles from Switzerland. The total (extracted by nitric acid) and the extractable (extracted by NH4-acetate-EDTA) amounts of lead varied significantly among the different parent materials.

The effect of high nonexchangeable aluminum on availability of nitrogen (N) and phosphorus (P) was studied in a Cryptopodzolic soil (Cademario) derived from mica schist in southern Switzerland. The research involved a greenhouse pot experiment comparing growth of barley on soil samples of three soil layers (10- to 25-, 40- to 60- and 70- to 90 cm) of the Cademario profile, representing a range of Al and organic matter properties, with the 10- to 40 cm layer of a profile of an acidic brown earth (Haplumbrept), derived from cherty limestone. The experiment, which included four nutrient treatments [check, N0 (PKS), P0 (NKS) and full (NPKS)], lime and no lime treatments and four replicates, was supplemented by soil chemical analysis. Results showed that liming alone produced greater yield responses in the Cademario soil than N or P added singly or together. On unlimed soils, barley yield for check, N0, and P0 treatments showed a positive linear relation with exchangeable Ca of soils and a negative linear relation with organically-complexed Al. Failure of liming to influence Pav, especially when combined with P fertilization, suggests that P was quickly absorbed on highly active surfaces formed from initially exchangeable Al.

Mineralization of soil organic matter and of added 14 C labelled substrates were studied on samples from two acidic forest soils, “Cademario”-sample from the Bh-horizon of a cryptopodzolic soil rich in humus and nonexchangeable Al and “Sagno”-sample from the A-horizon of a Haplumbrept with moderate humus- and Al-content. The respiration rates for the two soils were not different when related to the content of organic matter. When treated with Na 2 CO 3 , the CO 2 production rate in the Sagno soil increased about three fold whereas no significant difference was observed for Cademario samples. This is attributed to the more pronounced dissolution of organic matter due to the pH increase in the Sagno soil. N-mineralization was different in the two soils. During a 28 day incubation period, 0.11% and 0.34% of the total organic N was released in the Cademario and Sagno samples, respectively. Na 2 CO 3 treatment stimulated N-mineralization in both soils but the mineral N-form was primarily nitrate in the Sagno sample and ammonium in the aluminum-rich sample from Cademario. Glucose, succinate and salicylate added to the soils were mineralized in this order. However, CO 2 evolution was much slower in the case of salicylate, especially in the untreated soils, a fact which is attributed to the Al-complexing power of this substrate.

The effect of high nonexchangeable aluminum of a Cryptopodzolic soil derived from mica schist on decomposition and nutrient release from chestnut ( Castanea sativa ) leaf litter was studied in southern Switzerland using the litter bag technique. Variables studied were time (18 months), exposure (NW versus SE), and profile position of litter (L, O f and A h horizons). A site with a Haplumbrept (Al-poor) derived from cherty limestone provided a parent material contrast. Litter decay was chiefly controlled by microclimatic of sites rather than parent material. Litter decay differed between NW- and SE-exposed sites for L and O f horizons. After 18 months, initial dry matter remaining in L, O f and A h positions was 58, 34 and 18%, respectively. All factors equal, the mobility series for nutrient release was K>Mg>Ca>P>N, but site and litter position affected element release. Only K and Mg were lost more rapidly than dry matter. Because dry matter and nutrient loss were similar for Al-rich and Al-poor sites, we conclude that Al content of soils had no influence on decomposition.

The role of aluminium on humus accumulation in acid forest soils The impact of soil-borne aluminum on humus accumulation was investigated in a forest soil of the chestnut zone (Castanea sativa) in southern Switzerland (Ticino). Soil samples of two soils formed on bedrocks which differ mainly in their aluminum content were extracted with HNO 3 , NH 4 Ac.-EDTA, NH 4 Cl, KCl, and NH 4 F-HCl and analyzed for the most abundant elements. On gneiss which contains up to about 10% of total aluminum the common soil type in this area is a Cryptopodzol. This soil is similar to the nonallophanic Udands. It is rich in wellhumified organic matter and shows dark-colored A h -, A(E)- and B h -horizons. The soil samples of these horizons are extremely rich in nonexchangeable aluminum which is, however, extractable with NH 4 Ac.-EDTA. It is assumed that this Al is intimately bound to the organic matter. The soil samples of these horizons contain large amounts of HNO 3 -extractable phosphorus. Up to 90% of this P appears in the organic fraction. The content of NH 4 F-HCl-extractable P is only 0.7 to 3.4 mg/kg. It is concluded that due to excessive Al in the organic matter the humus mineralization is inhibited compared to the Haplumbrepts of the region.

Die Frequenz eines He-Ne-Lasers wird durch Vergleich mit einer Zeeman-aufgespaltenen Ne-Absorptionslinie nachgeregelt. Die Empfindlichkeit des Vergleichs wird durch optische Verstärkung erhöht. Als Ergebnis der theoretischen und experimentellen Untersuchungen kann die Laserfrequenz mit einem Fehler von weniger als 60 kHz bezüglich der Mittenfrequenz des Ne-Absorptionsprofils eingestellt werden. Die daraus resultierende relative Frequenzstabilität von Δ v/v =1.3×10 −10 ist durch das systembedingte Rauschen begrenzt und kann durch geeignete Massnahmen weiter erhöht werden.

Zusammenfassung Die Frequenz eines He-Ne-Lasers wird durch Vergleich mit einer Zeeman-aufgespaltenen Ne-Absorptionslinie nachgeregelt. Die Empfindlichkeit des Vergleichs wird durch optische Verstärkung erhöht. Als Ergebnis der theoretischen und experimentellen Untersuchungen kann die Laserfrequenz mit einem Fehler von weniger als 60 kHz bezüglich der Mittenfrequenz des Ne-Absorptionsprofils eingestellt werden. Die daraus resultierende relative Frequenzstabilität von ?v/v=1.3×10-10 ist durch das systembedingte Rauschen begrenzt und kann durch geeignete Massnahmen weiter erhöht werden.