Forest vegetation affecting the deposition of atmospheric elements to soils

Atmospheric inputs of elements/ions into the soil through bulk precipitation and throughfall (precipitation below tree canopies) were monitored monthly at two forested catchments (Lesni Potok and Liz) in central and southwestern Bohemia, respectively. The annual deposition fluxes (expressed in μg/mg m^?2 yr^?1) of Al, As, Ba, Be, Ca, Cd, Cl^?, F^?, Fe, K, Mg, Mn, N_tot, Na, Ni, Pb, Rb, SO ₄ ^2? , Sr and Zn between 1997 and 2005 were calculated from their concentrations in monthly collected samples of both precipitation types. The flux of H⁺ was calculated from the monthly pH values as well. The more pristine character of the Liz catchment was manifested in lower inputs of anions of strong inorganic acids (mostly of anthropogenic origin) and of H⁺ in spite of higher precipitation amounts at the site. The comparison of fluxes in bulk precipitation (BP) and throughfall (TH) has shown significantly higher values for Rb, K, Mg, Mn, F^?, Ca, SO ₄ ^2? , Sr, Ba and Cl^? in the latter flux. It is declared that high fluxes of these elements/ions in TH significantly affect the forest soil water chemistry and that the forest vegetation significantly contributes to the mobilization of several elements in soil and to their redistribution throughout the soil profile.     

Allometric constraints on Sr/Ca and Ba/Ca partitioning in terrestrial mammalian trophic chains

In biological systems, strontium (Sr) and barium (Ba) are two non-essential elements, in comparison to calcium (Ca) which is essential. The Sr/Ca and Ba/Ca ratios tend to decrease in biochemical pathways which include Ca as an essential element, and these processes are termed biopurification of Ca. The quantitative pathway of the biopurification of Ca in relation to Sr and Ba between two biological reservoirs (R _n and R_{n -1}) is measured with an observed ratio (OR) expressed by the (Sr/Ca) _Rn /(Sr/Ca) _Rn-1 and (Ba/Ca) _Rn /(Ba/Ca) _Rn-1 ratios. For a mammalian organism, during the whole biopurification of Ca starting with the diet to the ultimate reservoir of Ca which is the bone, the mean values for OR_Sr and OR_Ba are 0.25 and 0.2, respectively. In this study, published Sr/Ca and Ba/Ca ratios are used for three sets of soils, plants, and bones of herbivorous and carnivorous mammals, each comprising a trophic chain, to illustrate the biopurification of Ca at the level of trophic chains. Calculated OR_Sr and OR_Ba of herbivore bones in relation to plants and of bones of carnivores in relation to bones of herbivores give OR_Sr=0.30±0.08 and OR_Ba=0.16±0.08, thus suggesting that trophic chains reflect the Sr/Ca and Ba/Ca fluxes that are prevalent at the level of a mammalian organism. The slopes of the three regression equations of log(Sr/Ca) vs. log(Ba/Ca) are similar, indicating that the process of biopurification of Ca with respect to Sr and Ba is due to biological processes and is independent of the geological settings. Modifications of the logarithmic expression of the Sr/Ca and Ba/Ca relationship allow a new formula of the biopurification process to be deduced, leading to the general equation OR_Ba=OR_Sr^1.79±0.33,where the allometric coefficient is the mean of the slopes of the three regression equations. Some recent examples are used to illustrate this new analysis of predator-prey relations between mammals. This opens up new possibilities for the utilization of Ba/Ca and Sr/Ca in addition to stable isotope ratios (¹³C and ¹⁵N) for the determination of the relative contribution of different food sources to an animals diet.     

Differential uses of coral reef habitats by a poorly-known cryptic fish predator

This study used otolith microchemistry to evaluate whether the moray eel Gymnothorax chilospilus uses different habitats throughout its life (mainly juvenile and adult phases). Of the most informative trace elements within otoliths (the twelve isotopes ²³Na, ²⁵Mg, ⁴³Ca, ⁵⁵Mn, ⁵⁹Co, ⁶⁰Ni, ⁶³Cu, ⁶⁶Zn, ⁸⁶Sr, ¹¹¹Cd, ¹³⁸Ba and ²⁰⁸Pb) only three ratios of Ca (Na:Ca, Sr:Ca and Ba:Ca) were informative and therefore used in a multivariate regression-tree analysis. Using a multivariate partitioning, three main phases were described from profiles, including the larval life phase (leptocephali), the intermediate phase (longest section between the larval life phase and the terminal phase) and the terminal phase (final section i.e., the most recent months preceding the death of fish). According to concentrations of the three ratios to Ca, G. chilospilus can be separated into three groups during their larval life stage (very different in Sr and Na), four groups during the intermediate phase (few differences in Sr and Na) and three groups during the terminal phase (differences in Sr), illustrating that G. chilospilus inhabit different habitats during these three phases. Our results showed that the leptocephali encountered different oceanic water masses with fluctuating Sr:Ca ratios during the early larval phase. During the intermediate phase (main part of their life-span), they lived in lagoonal waters such as fringing reefs or reef flats of lagoonal islets, characterized by a lower Sr:Ca ratio. During the latter part of their life, approximately one third of G. chilospilus encountered more oceanic waters close to or at barrier reefs, suggesting possible movements of these fish along a coast-to-ocean gradient.     

Dy3+‐activated NaM4 (VO4)3 (M = Ca,Ba, Sr) phosphor for near‐UV solid‐state lighting

We report the photoluminescence characterization of Dy³⁺‐activated NaM₄(VO₄)₃ (M = Ca, Ba, Sr) phosphors prepared by a solid‐state method. The synthesis was confirmed by X‐ray diffraction (XRD) characterization and photoluminescence (PL) emission results showed sharp blue and yellow bands for NaM₄(VO₄)₃ (M = Ca, Ba, Sr):Dy³⁺ phosphors at the excitation wavelength of 323 nm, which is near‐UV excitation. Thus, these phosphors could be applicable for near‐UV excited solid‐state lighting devices. Copyright © 2011 John Wiley & Sons, Ltd.     

Test of soil extractants for their suitability in predicting Ca/Sr ratios in leaves and stems of sugar maple seedlings

Differential uptake and translocation of Ca and Sr in organisms have been reported, calling into question the use of Sr to track Ca cycling in the environment. We investigated the relationship between Ca/Sr ratios in soil extracts of various strengths (H₂O, NH₄Cl, and NH₄EDTA) and seedlings of sugar maple (Acer saccharum Marsh.) grown from natural regeneration on 37 sites. Our objectives were to determine if Ca/Sr ratios in soil extracts are correlated with those in sugar maple tissues, and what soil extractant best duplicate plant tissue Ca/Sr ratios. Leaves had higher Ca/Sr ratios than stems and the extractants did not produce equal Ca/Sr ratios: H₂O had the lowest Ca/Sr, and NH₄EDTA the highest. The relationships between soil extract Ca/Sr ratios and leaf and stem Ca/Sr ratios were significant and linear, but the slopes differed among extractants. The lowest slope (0.45) was observed for the water extract/leaves and the highest (2.15) for the NH₄EDTA extract/stem with discrimination factors ranging from 0.22 with NH₄EDTA to 1.59 for water. Leaf extracts were more strongly correlated with soil Ca/Sr than stem extracts (R ² of 0.57–0.7 vs. R ² of 0.45–0.6, respectively). These findings support the use of Ca/Sr ratios in plants to track their source of soil Ca, but they highlight the need to calibrate the relationships for the plant tissue and soil extractant used.     

Spatial and temporal variations in otolith chemistry and relationships with water chemistry: a useful tool to distinguish Atlantic salmon Salmo salar parr from different natal streams

Otolith elemental (Sr:Ca, Ba:Ca, Mn:Ca, Mg:Ca and Rb:Ca) and isotopic (⁸⁷Sr:⁸⁶Sr) profiles from several annual cohorts of juvenile Atlantic salmon Salmo salar were related to the physico‐chemical characteristics (chemical signatures, flow rate, temperature and conductivity) of their natal rivers over an annual hydrological cycle. Only Sr:Ca, Ba:Ca and ⁸⁷Sr:⁸⁶Sr in otoliths were determined by their respective ratios in the ambient water. Sr:Ca ratios in stream waters fluctuated strongly on a seasonal basis, but these fluctuations, mainly driven by water flow regimes, were not recorded in the otoliths. Otolith Sr:Ca ratios remained constant during freshwater residency at a given site and were exclusively related to water Sr:Ca ratios during low flow periods. While interannual differences in otolith elemental composition among rivers were observed, this variability was minor compared to geographic variability and did not limit classification of juveniles to their natal stream. Success in discriminating fish from different sites was greatest using Sr isotopes as it remained relatively constant across years at a given location.     

Trends in cation, nitrogen, sulfate and hydrogen ion concentrations in precipitation in the United States and Europe from 1978 to 2010: a new look at an old problem

Industrial emissions of SO₂ and NO_x, resulting in the formation and deposition of sulfuric and nitric acids, affect the health of both terrestrial and aquatic ecosystems. Since the mid-late 20th century, legislation to control acid rain precursors in both Europe and the US has led to significant declines in both SO₄–S and H⁺ in precipitation and streams. However, several authors noted that declines in streamwater SO₄–S did not result in stoichiometric reductions in stream H⁺, and suggested that observed reductions in base cation inputs in precipitation could lessen the effect of air pollution control on improving stream pH. We examined long-term precipitation chemistry (1978–2010) from nearly 30 sites in the US and Europe that are variably affected by acid deposition and that have a variety of industrial and land-use histories to (1) quantify trends in SO₄–S, H⁺, NH₄–N, Ca, and NO₃–N, (2) assess stoichiometry between H⁺ and SO₄–S before and after 1990, and (3) examine regional synchrony of trends. We expected that although the overall efforts of developed countries to reduce air pollution and acid rain by the mid-late 20th century would tend to synchronize precipitation chemistry among regions, geographically varied patterns of fossil fuel use and pollution control measures would produce important asynchronies among European countries and the United States. We also expected that control of particulate versus gaseous emission, along with trends in NH₃ emissions, would be the two most significant factors affecting the stoichiometry between SO₄–S and H⁺. Relationships among H⁺, SO₄–S, NH₄–N, and cations differed markedly between the US and Europe. Controlling for SO₄–S levels, H⁺ in precipitation was significantly lower in Europe than in the US, because (1) alkaline dust loading from the Sahara/Sahel was greater in Europe than the US, and (2) emission of NH₃, which neutralizes acidity upon conversion to NH₄ ⁺, is generally significantly higher in Europe than in the US. Trends in SO₄–S and H⁺ in precipitation were close to stoichometric in the US throughout the period of record, but not in Europe, especially eastern Europe. Ca in precipitation declined significantly before, but not after 1990 in most of the US, but Ca declined in eastern Europe even after 1990. SO₄–S in precipitation was only weakly related to fossil fuel consumption. The stoichiometry of SO₄–S and H⁺ may be explained in part by emission controls, which varied over time and among regions. Control of particulate emissions reduces alkaline particles that neutralize acid precursors as well as S-containing particulates, reducing SO₄–S and Ca more steeply than H⁺, consistent with trends in the northeastern US and Europe before 1990. In contrast, control of gaseous SO₂ emissions results in a stoichiometric relationship between SO₄–S and H⁺, consistent with trends in the US and many western European countries, especially after 1991. However, in many European countries, declining NH₃ emissions contributed to the lack of stoichiometry between SO₄–S and H⁺.Recent reductions in NO_x emissions have also contributed to declines in H⁺ in precipitation. Future changes in precipitation acidity are likely to depend on multiple factors including trends in NO_x and NH₃ emission controls, naturally occurring dust, and fossil fuel use, with significant implications for the health of both terrestrial and aquatic ecosystems.     

Asteriscus v. lapillus: comparing the chemistry of two otolith types and their ability to delineate riverine populations of common carp Cyprinus carpio

The chemical composition of common carp Cyprinus carpio asteriscus (vaterite) and lapillus (aragonite) otoliths from the same individual and reflecting the same growth period was measured to (1) determine whether there are differences in the uptake of trace metals (Mg:Ca, Mn:Ca, Sr:Ca and Ba:Ca ) and Sr isotope ratios (⁸⁷Sr:⁸⁶Sr) in co‐precipitating lapilli and asterisci and (2) compare the ability of multi‐element and isotopic signatures from lapilli, asterisci and both otolith types combined to discriminate C. carpio populations over a large spatial scale within a river basin. Depth profile analyses at the otolith edge using laser‐ablation inductively coupled plasma mass spectrometry showed that asterisci were enriched in Mg and Mn and depleted in Sr and Ba relative to lapilli, whilst ⁸⁷Sr:⁸⁶Sr values were nearly identical in both otolith types. Significant spatial differences among capture locations were found when all trace element and Sr isotope ratio data were aggregated into a multi‐element and isotopic signature, regardless of which otolith type was used or if they were used in combination. Discriminatory power was enhanced, however, when data for both otolith types were combined, suggesting that analysis of multiple otolith types may be useful for studies attempting to delineate C. carpio populations at finer spatial or temporal scales.     

Detoxification of SO2 in conifers differing in SO2-tolerance

Contents of organic sulfur, sulfate and the inorganic cations K⁺, Ca²⁺, Mg²⁺, Mn²⁺ and Na⁺ were compared in needles of three conifer species differing in tolerance to chronic SO₂ immissions. Sulfate and organic sulfur compounds were also measured in bark and wood. Field material was collected from Norway Spruce (Picea abies (L.) Karst.), Colorado Spruce (Picea pungens Engelm.) and Scots Pine (Pinus sylvestris L.) at sites where the SO₂ concentration in air was high, and at another site where it was low. In general, sulfate contents were higher but cation contents lower at the sites where SO₂ concentrations were high than where they were low. Up to 114mmol · (kg DW)^–1 sulfate was measured in fouryear-old needles of Norway Spruce from the Erzgebirge (annual mean of SO₂ in air 32 nl · 1^–1). Sulfate accumulation in this SO₂-sensitive conifer increased with SO₂ concentration in ambient air and with needle age, indicating that the main part of the sulfate resulted from the oxidative detoxification of SO₂. Loss of inorganic cations from ageing needles was reduced, or cation levels even increased, with increasing needle age, while sulfate accumulated. Apparently, cations served as counter-ions for sulfate, which is sequestered in the vacuoles. Individual trees differed in regard to the nature of cations which accumulated with sulfate. Calcium, potassium and magnesium were the dominating cations. Sodium levels were very low. Needles of the SO₂-tolerant conifers Colorado Spruce and Scots Pine growing next to Norway Spruce in the Erzgebirge did not accumulate, or accumulated less, sulfate with increasing needle age as compared to needles of Norway Spruce. However, somewhat more sulfate was found in the bark of the SO₂-tolerant species than in the bark of Norway Spruce. Scots Pine contained distinctly more sulfate in the wood than the other conifers. Since accumulation of organic sulfur compounds could not be observed with increasing needle age, or in bark and wood, reduction does not appear to play a major role in the detoxification of SO₂ by the investigated species. Physiological mechanisms permitting Colorado Spruce and Scots Pine to avoid the sulfate accumulation in the needles and the accompanying sequestration of cations that are observed in neighbouring Norway Spruce are discussed on the basis of the obtained data.Abbreviations S_org organic sulfur compounds Died June 10, 1991, aged 29, in a traffic accident. He initiated this work.This work was supported by the Sonderforschungsbereich 251 of the University of Würzburg and by the Projektgruppe Bayern zur Erforschung der Wirkung von Umweltschadstoffen (PBWU). The authors with to thank Prof. Dr. W Kaiser and Prof. Dr. W. Urbach (both Julius-von-Sachs-Institut, University of Würzburg, Germany) for HPLC-analysis and ICP-analysis.     

Interaction between calcium ions and surface charge as it relates to calcium currents

Summary Calcium ions affect the gating of Ca currents. Surface charge is involved but to what extent is unknown. We have examined this, using isolated nerve cell bodies ofHelix aspersa and the combined microelectrode-suction pipette method for voltage-clamp and internal perfusion. We found that Ba and Sr currents produced by substitution of these ions for extracellular Ca ions are activated at less positive potentials than Ca currents. Mg ions do not permeate the Ca channel and changes in [Mg]₀ produce shifts in the activation-potential curves that are comparable to the effects of changes in [Ba]₀ or [Sr]₀. Inactivation of Ba currents also occurs at less positive potentials. Perfusion intracellularly with EGTA reduced inactivation of Ca currents as a function of potential, but did not shift the inactivation-potential curve. Hence, Ca current-dependent inactivation which is blocked by intracellular EGTA probably does not involve a similar change of intracellular surface potential. The voltage shifts of activation and inactivation produced by extracellular divalent cations used singly or in mixtures can be described by the Gouy-Chapman theory for the diffuse double layer with binding (Gilbert & Ehrenstein, 1969; McLaughlin, Szabo & Eisenman, 1971). From the surface potential values and the Boltzman distribution, we have computed surface concentrations that predict the following experimental observations: 1) saturation of current-concentration relationships when surface potential is changing maximally; 2) the increase in peak current when Ca ions are replaced by Sr or Ba ions; and 3) the greater inhibitory effect of Mg onI _Ba thanI _Ca. Theory indicates that surface charge cannot be screened completely even at 1m [Mg]₀ and thus that Ca channel properties must be evaluated in the light of surface charge effects. For example, after correction for surface charge effects the relative permeabilities of Ca, Ba and Sr ions are equivalent. In the presence of Co ions, however, Ca ions are more permeable than Ba ions suggesting a channel binding site may be involved.     

The ionic requirements for the initiation of action potentials in insect muscle fibers

Electrical properties of locust leg muscle fibers were studied by means of intracellular electrodes. In most fibers, a depolarizing current pulse initiated a local response. A delayed decrease in membrane resistance appeared with more than about 10 mv depolarization. In some fibers a regenerative response also was found. Membrane constants were measured, applying the short cable model. The value of the space constant λ was 1.6 mm and the calculated value of R_m was about 1750 ohm cm². Action potentials could be elicited when the bathing fluid contained more than 2–5 mM Ba or Sr. Similar responses were seen with 2 mM Ca in the presence of tetraethylammonium (TEA). The overshoot of these action potentials increased with increasing [Ca⁺⁺]_o, [Sr⁺⁺]_o, or [Ba⁺⁺]_o, the increment for a 10-fold increase being about 29 mv for Ca and Sr and between 40 and 50 mv for Ba. These action potentials were inhibited by Mn ions but were not affected by tetrodotoxin or procaine. In solutions containing Ba or Sr, action potentials generated were suppressed by addition of Ca. The removal of Na ions did not change the configuration of the action potential. The results suggest that an increase in permeability to Ca, Ba, or Sr ions makes a major contribution to the initiation of action potentials in this tissue.     

Input-output budgets at Langtjern,a small acidified lake in southern Norway

Precipitation and streamwater volume and chemical composition have been measured since 1974 at Langtjern, a small, acid (pH 4.6–4.8) lake on granitic-gneissic bedrock in coniferous forest located ca. 100 km north of Oslo, Norway. The area receives acid precipitation (weighted average pH 4.28). The 7-year input-output budgets for major ions at two terrestrial subcatchments indicate that for Na, K, SO₄ and Cl outputs approximately equal inputs, for H⁺, NH₄ and NO₃ outputs are much less than inputs, and for Ca, Mg and Al outputs greatly exceed inputs. The sulfate budgets (which include estimated dry deposit) indicate that the terrestrial catchment retains about 20% of the incoming sulfate, perhaps due to absorption in the soil, plant uptake, reduction and storage in peaty areas or reduction and release of H₂S to the atmosphere. The budgets for Langtjern lake itself indicate that for most components output equals inputs to within 10%, i.e. these compounds simply pass through the lake. For H⁺, and possibly NH₄ and NO₃, inputs exceed outputs. Because gaseous phases are not measured the N budgets are uncertain. A mechanism that leads to ‘retention’ of both H⁺ and SO₄ is sulfate reduction and incorporation of sulfides in the lake sediments. Such has been documented in the experimentally-acidified Lake 223, Experimental Lakes Area, Ontario, Canada. Although there is no evidence suggesting the development of anoxic bottom waters at Langtjern, such reduction might occur at the water-sediment interface and in the sediments. The budgets for the pollutant components H⁺ and SO₄ at Langtjern differ substantially from those at the relatively unaffected Lake 239, in the Experimental Lakes Area.     

Untersuchungen zur Wechselwirkung von47Ca,85Sr,133Ba und226Ra mit Proteinen im Rinderserum

Zusammenfassung Mittels Hochdruckultrafiltration wurde im Rinderserum beiin vitro-Markierung mit⁴⁷Ca,⁸⁵Sr,¹³³Ba und²²⁶Ra die Wechselwirkung dieser Elemente mit Proteinen, studiert. Das Ergebnis der Experimente läßt folgende Schlüsse zu: Es besteht zwischen den genannten Erdalkalien und Serumproteinen ein dynamisches, chemisches Gleichgewicht, das unter Berücksichtigung des Aktivitätskoeffizienten durch das Massenwirkungsgesetz beschrieben werden kann. Die Temperatur hat im untersuchten Bereich im Gegensatz zumpH-Wert des Serums keinen großen Einfluß auf das Gleichgewicht; bei Zunahme despH-Wertes, erfolgt eine steigende Bindung der Erdalkalien an Proteine.

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Interaction of⁴⁷Ca,⁸⁵Sr,¹³³Ba and²²⁶Ra with serum proteins

Summary The interaction of Ca, Sr, Ba and Ra with serum proteins was studiedin vitro by means of high presure ultrafiltration of⁴⁷Ca,⁸⁵Sr,¹³³Ba and²²⁶Ra. From these experiments the following conclusions can be drawn: the dynamic equilibrium which exists between these alkaline earth elements and serum protein may be described by the law of mass action considering the activity coefficient. While in the region examined only a moderate influence of temperature on the equilibrium could be observed, the binding of these elements to serum proteins could be considerably increased by increasingpH.

     

A method for determining tissue sulfate

A method for the determination of the inorganic sulfate present in rat liver homogenates has been developed. In order to determine sulfate, a protein-free extract is required. The classical protein precipitation methods of preparing protein-free extracts gave 2.5–40% recovery of added ³⁵SO₄^2?. Separation of the protein by ultrafiltration gave only 29% recovery when 0.15 m KCl was the homogenizing medium. A homogenization medium containing 0.154 m NH₄OH and 20 g EDTA per liter gave 102 ± 11% recovery of added ³⁵SO₄^2? when the protein was separated by ultrafiltration.     

Synthesis, structure and thermochemical behavior of bis-(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)-(1,4,7,10,13,16-hexaoxa-cyclooctadecane)-strontium in comparison with its structural and thermochemical analogous

The trans-[M(18-crown-6)(C₅HO₂F₆)₂] (M = Ca, Sr, Ba, Pb) complexes have been synthesized and identified. The crystal structure of the Sr complex has been determined by X-ray diffraction. The basic structural unit is the mononuclear complex trans-[Sr(18-crown-6)(C₅HO₂F₆)₂]. The thermal properties of the complexes have been correlated to their structure. The melting and decomposition ranges of the Ca, Sr and Ba complexes and their sublimation temperatures at ∼10⁻² mm Hg have been determined. Experimental evidence is presented that the complexes are similar in volatility.     

Maroteaux-Lamy disease (mucopolysaccharidosis VI), subtype A: deficiency of a N-acetylgalactosamine-4-sulfatase

The non-reducing terminal moiety of ³⁵SO₄-dermatan sulfate accumulating in fibroblasts cultured from the skin of patients with one form of Maroteaux-Lamy disease was found to be N-acetylgalactosamine-4-sulfate. This end group accounted for about 3 % of the total radioactivity. Using both ³⁵SO₄- and ¹⁴C-N-acetylgalactosamine-labeled dermatan sulfates from the patients fibroblasts as substrates, it was found that homogenates of Maroteaux-Lamy fibroblasts, but not of normal, Hurler and Sandhoff fibroblasts fail to cleave inorganic sulfate from the non-reducing termini. We conclude, that deficiency of N-acetylgalactosamine-4-sulfatase is the biochemical basis for this form of Maroteaux-Lamy disease.     

X-ray Microanalysis of the Mineral Contents of Some Protozoa

With the aid of energy-dispersive X-ray microanalysis, several protozoa were tested for content of cations within inorganic minerals. The skeleton of acantharia consists mainly of Sr with small quantities of Ca and Ba. Two Loxodes species contain nothing but Ba, while in some Remanella species Sr with small quantities of Ba were present. In one Geleia species, Ca with small quantities of Sr was found; in two Trachelocerca species from Sylt (Germany), Ba is there in addition. Another Trachelocerca species from northern Italy lacked Ba, but did possess Mn. In Prorodon only Ca was found.     

Changes in Sr/Ca, Ba/Ca and 87Sr/86Sr ratios between trophic levels in two forest ecosystems in the northeastern U.S.A.

The variability and biologicalfractionation of Sr/Ca, Ba/Ca and ⁸⁷Sr/⁸⁶Srratios were studied in a soil–plant–invertebrate–bird food chain in two forested ecosystems withcontrasting calcium availability in the northeasternU.S.A. Chemical measurements were made of the soilexchange pool, leaves, caterpillars, snails, and boththe femurs and eggshells of breeding insectivorousmigratory songbirds. ⁸⁷Sr/⁸⁶Sr values weretransferred up the food chain from the soil exchangepool to leaves, caterpillars, snails and eggshellswithout modification. Adult birds were the oneexception; their ⁸⁷Sr/⁸⁶Sr values generallyreflected those of lower trophic levels at each site,but were lower and more variable, probably becausetheir strontium was derived in part from foods intropical winter habitats where lower⁸⁷Sr/⁸⁶Sr ratios are likely to predominate. Sr/Ca and Ba/Ca ratios decreased at each successive trophiclevel, supporting previous suggestions that Sr/Ca andBa/Ca ratios can be used to identify the trophic levelat which an organism is primarily feeding. The changesin Sr/Ca and Ba/Ca ratios we measured for vegetationand insects were comparable to similar measurementsmade previously (but based on single samples of eachorganism) in an alpine ecosystem. Changes in Sr/Ca andBa/Ca ratios between birds and their food have notpreviously been measured, but the values we obtainedwere similar to those for herbivorous and carnivorousmammals at similar trophic levels. Our results provideevidence that supports the use of Sr/Ca ratios in thedetermination of human paleodiets and suggests thatSr/Ca ratios may also provide a useful tool in studiesof modern food webs. Furthermore, our findings suggestthat ⁹⁰Sr from nuclear fallout will notbioaccumulate in forests and that changes in Sr/Caratios between trophic levels will need to beconsidered in some cases when using⁸⁷Sr/⁸⁶Sr as a tracer of calciumbiogeochemistry.     

Element localization in ultrathin cryosections of high-pressure frozen ectomycorrhizal spruce roots

We present, for the first time, elemental mapping of ultra-thin cryosections from high-pressure frozen ectomycorrhizal roots of Picea abies–Hebeloma crustuliniforme. The maps provide interpretable information on the relationship between elements and the structure of inhomogeneous objects. Cryoultramicrotomy together with energy dispersive X-ray microanalysis (EDX) offers the potential to study the subcellular localization of specific ions and ecologically important tracers (Cs and Sr) in ectomycorrhizal roots under conditions resembling the natural slate as closely as possible. Structural changes of the ectomycorrhizal roots, in particular the absence of a Hartig net at high NH₄⁺ levels in the nutrient solution, were accompanied by elemental modification of Ca in cortical cell walls, where markedly higher concentrations of Ca were found. Cs and Sr applied to the nutrient solution were localized in root and fungal cells of the Hartig net. Cs accumulated mainly in the vacuoles of the Hartig net hyphae and its distribution was very similar to the distribution of K. In contrast to Cs, Sr was found to occur mainly in electron-opaque and P-rich granules. From this study, (here is no indication that Ca is the only ion accompanying P in the P-rich granules. Several elements including Ca, K, Cl, S, Cs and Sr, with highest concentrations for S, can occur together with P in these granules. The occurrence of the P-rich electron-opaque deposits in fungal cells might be the first evidence of polyphosphate granules in the native state, since our specimen preparation technique did not include chemical fixation.     

Seasonal and spatial patterns of S,Ca, and N dynamics of a Northern Hardwood forest ecosystem

Seasonal dynamics of S, Ca and N were examined at the Huntington Forest, a northern hardwood ecosystem in the central Adirondacks of New York for a period of 34 months (1985–1988). Solute concentrations and fluxes in bulk precipitation, throughfall (TF) and leachates from the forest floor, E horizon and B horizon were quantified. Both above and below-ground elemental fluxes mediated by vegetation (e.g. uptake, litter inputs, and fine roots production) were also determined. The roles of abiotic and biotic processes were ascertained based on both changes in solute concentrations through the strata of the ecosystem as well as differences between dormant and growing seasons. Concentrations of SO₄ ²⁻, NO₃ ⁻, NH₄ ⁺ and Ca²⁺ were greater in TF than precipitation. Forest floor leachates had greater concentrations of SO₄ ²⁻, NO₃ ⁻ + NH₄ ⁺ and Ca²⁺ (9, 6 and 77 μeq L⁻¹, respectively) than TF. There were differences in concentrations of ions in leachates from the forest floor between the dormant and growing seasons presumably due to vegetation uptake and microbial immobilization. Concentrations and fluxes of NO₃ ⁻ and NH; were greatest in early spring followed by a rapid decline which coincided with a demand for N by vegetation in late spring. Vegetation uptake (44.7 kg N ha⁻¹ yr⁻¹ ) could account for the low leaching rates of N0₃ ⁻. Within the mineral soil, changes with soil depth and the absence of seasonal patterns suggest that cation exchange (Ca⁺) or anion sorption (SO₄ ²⁻) are primarily responsible for regulating solute concentrations. The increase in SO₄ ²⁻ concentration after leachates passed through the mineral soil may be attributed to desorption of sulfate that was adsorbed during an earlier period when SO₄ ²⁻ concentrations would have been greater due to elevated S inputs.