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  • Stable isotopes
  • Springer  (14)
  • Elsevier  (2)
  • American Chemical Society
  • American Institute of Physics (AIP)
  • 2020-2022  (2)
  • 1990-1994  (14)
  • 1970-1974
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Publisher
  • Springer  (14)
  • Elsevier  (2)
  • American Chemical Society
  • American Institute of Physics (AIP)
  • GFZ Data Services  (1)
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  • 1
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    Geochemical investigations of the geothermal systems from the Island of Sicily (southern Italy) (2021)
    Elsevier
    Details
    Publication Date: 2021-06-15
    Description: Sicily hosts many natural manifestations that include thermal waters, gas discharges and mud volcanoes. Due to the significant geodynamic and geological differences, the fluid discharges along a NE-WS–oriented transect that run from the Peloritani Mts. to the Sciacca Plain shows a large variability in water and gas chemical and isotopic compositions. The studied waters are characterized by Ca-HCO3, Ca(Mg)-SO4, Ca-Cl and Na-Cl compositions produced by distinct geochemical processes such as water-rock-gas interactions, mixing between deep and shallow aquifers and seawater and direct and reverse ion exchanges. The gas chemistry is dominated by CO2 to the east and CO2-N2 to the west of the study area, whereas the central part shows mud volcanoes discharging CH4-rich gases. Water isotopes suggest that the thermal waters are fed by a meteoric recharge, although isotopic exchange processes between thermal fluids and host rocks at temperature 〉150°C are recognized. Accordingly, liquid geothermometry suggests equilibrium temperatures up to 220°C. The carbon in CO2 and helium isotopes of the emissions from the westernmost sector of Sicily indicate that these two gases consists of up to 40 % of a mantle component, the latter decreasing to the east down to 10% where CO2 of thermometamorphic origin dominates. Accordingly, conceptual models of the fluid circulation for the western, central and eastern sectors are proposed. The regional geothermal reservoir, hosted in carbonates in the western sector and locally outcropping, is of low to medium temperature. Higher temperature conditions (up to 200-220°C) are suggested by geothermometry and probably related to deeper levels of the system. Sicily can be regarded as a potentially suitable area for future investigations to evaluate specific activities aimed at exploiting the geothermal resource.
    Description: Published
    Description: 102120
    Description: 9T. Geochimica dei fluidi applicata allo studio e al monitoraggio di aree sismiche
    Description: JCR Journal
    Keywords: Fluid geochemistry ; Stable isotopes ; Geothermal exploration ; Dissolved gases ; Tectonics ; 03. Hydrosphere
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 2
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    On the complexity of anthropogenic and geological sources of carbon dioxide: Onsite differentiation using isotope surveying (2021)
    Elsevier
    Details
    Publication Date: 2021-05-18
    Description: Anthropogenic emissions of greenhouse gases (GHGs) co-occur with emissions of these gases from volcanic and urban environments. Therefore, it remains a challenge for the scientific community to identify the contamination sources and quantify the specific contributions. Stable isotopes have many applications in different fields under geosciences, including volcanology, environmental surveying, and climatology. Isotopic surveys allow identification of photosynthetic fractionation in tree forests and gas sources in urban zones, and tracking of volcanic degassing. Thus, the stable isotopic composition of the local GHGs allows the evaluation of the environmental impacts and assists in mitigating the emissions. The present study aimed to distinguish the tropospheric sources of CO2 in the different ecosystems based on the stable isotopic composition of CO2. The study relies on field experiments performed in both volcanic and urban zones of the Mediterranean region. Experiments to identify the CO2 origins in the field were designed and conducted in the laboratory. The CO2 in the air in Palermo, the soil CO2 released at Vulcano (Aeolian Islands, Italy), and the CO2 emitted at Cava dei Selci (Rome, Italy) were selected for conducting case studies. Isotope surveying of the CO2-containing air in Palermo revealed that the CO2 content was correlated to human activity. Mobile-based measurements of carbon isotope were conducted to distinguish the different sources of CO2 at the district scale. In particular, the isotopic surveying process distinguished landfill-related CO2 emissions from the fossil fuel burning ones. The underlying geological reservoir was identified as the main source of air CO2 at Cava dei Selci. Finally, partitioning of soil CO2 enabled estimation of the geological CO2 estimation in the Vulcano Porto settled zones. The results of the present study revealed that detailed investigations on stable isotopes assist in tracking the CO2 sources and the fate of gas emissions. The fine-tuned experimental solutions assisted in broadening the research perspectives. In addition, deeper insights into the carbon cycle were obtained.
    Description: Published
    Description: 118446
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Description: JCR Journal
    Keywords: Stable isotopes ; Carbon dioxide ; Greenhouse gas emissions ; Volcanic gases ; Mediterranean region ; 01.01. Atmosphere ; 04.08. Volcanology ; 05.08. Risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 3
    Electronic Resource
    Electronic Resource
    Nitrogen nutrition and isotope differences among life forms at the northern treeline of Alaska (1994)
    Springer
    Oecologia 100 (1994), S. 406-412 
    Details
    ISSN: 1432-1939
    Keywords: Boreal forest ; Nitrogen, phosphorus, and cation nutrition ; Stable isotopes ; Picea glauca Calamagrostis Vaccinium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Natural abundances of nitrogen isotopes, δ15N, indicate that, in the same habitat, Alaskan Picea glauca and P. mariana use a different soil nitrogen compartment from the evergreen shrub Vaccinium vitis-idaea or the deciduous grass Calamagrostis canadensis. The very low δ15N values (-7.7 ‰) suggest that (1) Picea mainly uses inorganic nitrogen (probably mainly ammonium) or organic N in fresh litter, (2) Vaccinium (-4.3 ‰) with its ericoid mycorrhizae uses more stable organic matter, and (3) Calamagrostis (+0.9 ‰) exploits deeper soil horizons with higher δ15N values of soil N. We conclude that species limited by the same nutrient may coexist by drawing on different pools of soil N in a nutrient-deficient environment. The differences among life-forms decrease with increasing N availability. The different levels of δ15N are associated with different nitrogen concentrations in leaves, Picea having a lower N concentration (0.62 mmol g−1) than Vaccinium (0.98 mmol g−1) or Calamagrostis (1.33 mmol g−1). An extended vector analysis by Timmer and Armstrong (1987) suggests that N is the most limiting element for Picea in this habitat, causing needle yellowing at N concentrations below 0.5 mmol g−1 or N contents below 2 mmol needle−1. Increasing N supply had an exponential effect on twig and needle growth. Phosphorus, potassium and magnesium are at marginal supply, but no interaction between ammonium supply and needle Mg concentration could be detected. Calcium is in adequate supply on both calcareous and acidic soils. The results are compared with European conditions of excessive N supply from anthropogenic N depositions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317862
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  • 4
    Electronic Resource
    Electronic Resource
    Natural abundance of 15N in soils along forest-to-pasture chronosequences in the western Brazilian Amazon Basin (1994)
    Springer
    Oecologia 99 (1994), S. 112-117 
    Details
    ISSN: 1432-1939
    Keywords: Stable isotopes ; Nitrogen ; Fixation Forest ; Rondônia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined the natural abundance of 15N in soil profiles along two chronosequences in the western Brazilian Amazon Basin state of Rondônia, to investigate possible mechanisms for changes to soil nitrogen sources and transformations that occur as a result of land use. One chronosequence consisted of forest and 3-, 5- and 20-year-old pasture, the other of forest and 8- and 20-year-old pasture. The δ15N values of surface soil and soil to 1 m depth in the native forest ranged from 9.8 to 13.6‰ and were higher than reported for temperate forest soils. Fractionation associated with nitrification and denitrification and selective losses of 15N-depleted nitrate, could potentially result in a strong enrichment of nitrogen in soil organic matter over the time scale of soil development in highly weathered tropical soils. Pasture surface soils were 1–3‰, depleted in 15N compared with forest soils. Lower δ15N values in 20-year-old pastures is consistent with greater cumulative inputs of 15N-depleted atmospheric-derived nitrogen, fixed by free-living bacteria associated with planted pasture grasses in older pastures, or differential plant utilization of soil inorganic N pools with different δ15N values. The pattern of δ15N values following conversion of forest to agricultural use differs from the pattern in the temperate zone, where pasture or cultivated soils are typically more enriched in 15N than the forest soils from which they were derived.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317090
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  • 5
    Electronic Resource
    Electronic Resource
    Water and nitrogen dynamics in an arid woodland (1994)
    Springer
    Oecologia 99 (1994), S. 233-242 
    Details
    ISSN: 1432-1939
    Keywords: Cryptobiotic crust ; Desert ecology ; Nitrogen cycle ; Stable isotopes ; Water source
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Arid environments are characterized by spatial and temporal variation in water and nitrogen availability. differences in δ15N and δD of four co-occurring species reveal contrasting patterns of plant resource acquisition in response to this variation. Mineralization potential and nitrogen concentration of surface soils associated with plant canopies were greater than inter-canopy locations, and values decreased with increasing depth in both locations. Mineralization potential and nitrogen concentration were both negatively correlated with soil δ15N. The spatial variation in soil δ15N caused corresponding changes in plant δ15N such that plant δ15N values were negatively correlated with nitrogen concentration of surface soils. Plants occurring on soils with relatively high nitrogen concentrations had lower δ15N, and higher leaf nitrogen concentrations, than plants occurring on soils with relatively low nitrogen concentrations. Two general temporal patterns of water and nitrogen use were apparent. Three species (Juniperus, Pinus andArtemisia) relied on the episodic availability of water and nitrogen at the soil surface. δ15N values did not vary through the year, while xylem pressure potentials and stem-water δD values fluctuated with changes in soil moisture at the soil surface. In contrast,Chrysothamnus switched to a more stable water and nitrogen source during drought. δ15N values ofChrysothamnus increased throughout the year, while xylem pressure potentials and stem-water δD values remained constant. The contrasting patterns of resource acquisition have important implications for community stability following disturbance. Disturbance can cause a decrease in nitrogen concentration at the soil surface, and so plants that rely on surface water and nitrogen may be more susceptible than those that switch to more stable water and nitrogen sources at depth during drougnt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00627735
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  • 6
    Electronic Resource
    Electronic Resource
    Stable isotope study of carbonate-cemented rocks from the Pobitite Kamani area, north-eastern Bulgaria (1993)
    Springer
    International journal of earth sciences 82 (1993), S. 663-666 
    Details
    ISSN: 1437-3262
    Keywords: Stable isotopes ; Carbonate cements ; Pobitite Kamani, Bulgaria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The Precipitation of carbonate cements in the Pobitite Kamani area (Lower Eocene) began during early diagenesis of sediments. There is evidence, however, that calcite is still forming today. The negative δ13C values to −29.2‰ suggest that the carbonate formed during degradation of 12C-enriched organic matter (perhaps partly from oxidation of methane). The δ18O values of −0.9 to −1.6‰ reflect the marine origin of the early diagenetic carbonate cements. Most of the carbonates, however, formed during late diagenesis (at approximately 1300 m burial depth) and/or recently (after uplift) from percolating groundwaters. These carbonates have an isotopic composition characteristic of carbonates which precipitated from meteoric waters under normal sedimentary temperatures in isotopic equilibrium with 12C-enriched soil carbon dioxide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00191493
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  • 7
    Electronic Resource
    Electronic Resource
    Seasonal changes in the diets of migrant and non-migrant nectarivorous bats as revealed by carbon stable isotope analysis (1993)
    Springer
    Oecologia 94 (1993), S. 72-75 
    Details
    ISSN: 1432-1939
    Keywords: Nectarivory ; Stable isotopes ; Bats ; Migration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three species of nectar-feeding bats migrate from tropical and subtropical Mexico into the Sonoran and Chihuahuan deserts during the spring and summer months. We examined geographic and seasonal changes in the diet of one migrant species, Leptonycteris curasoae, using carbon stable isotope techniques to determine the relative importance of C3 and CAM (Cactaceae, Agavaceae) plants in its diet. We also examined the diet of a non-migratory nectar-feeding bat, Glossophaga soricina, from southern Mexico using the same techniques. We found that L. curasoae feeds extensively or exclusively on CAM plants during migration and in the northern part of its range and feeds mostly on C3 plants in southern Mexico. This bat is a year-round resident on Baja California where it is a CAM specialist. The non-migrant G. soricina feeds mostly on C3 plants year-round. Phenological data suggest that certain species of columnar cacti and at least one group of paniculate Agaves on the Mexican mainland provide a spatio-temporally predictable nectar corridor along which nectarivorous bats may migrate in the spring and fall, respectively. Different flowering schedules of Agaves in Baja California appear to promote year-round dietary specialization and perhaps non-migratory behavior in nectar-feeding bats living there.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317304
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  • 8
    Electronic Resource
    Electronic Resource
    Plant responses to past concentrations of CO2 (1993)
    Springer
    Plant ecology 104-105 (1993), S. 145-155 
    Details
    ISSN: 1573-5052
    Keywords: Altitude ; Plant growth ; Populations ; Stomata ; Stable isotopes ; Water use efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The influence of recent historical changes in atmospheric CO2 have been investigated by two methods: 1, the responses of leaf development and physiology as indicated by leaves stored in herbaria and 2, by investigating the differential growth responses of populations originating from naturally different CO2 concentrations. Herbarium leaves indicate that stomatal density and leaf nitrogen have decreased over the last 150 to 200 years, while water use efficiency, estimated from leaf δ13C and historical measurements of climate, has increased. Natural populations ofBoehmeria cylindrica were found growing at sites, in Florida, with CO2 mole fractions varying naturally from 350 µmol mol-1 to 505 µmol mol-1. Plants were grown in the controlled environment, using seeds originating from populations occurring in the different CO2 mole fractions. Plants from the different ambient CO2 mole fractions showed different rates of growth and different non-linear responses of the shoot to root ratio in response to changes in the CO2 mole fraction from 350 to 675 µmol mol-1. The proposal that plants originating from high altitude will whow greater stimulations of growth with an increase in CO2, than plants from low altitude, was rejected in experiments which simulated the atmospheric pressure at altitudes of 0 and 2000m, at CO2 mole fractions of 350 and 700 µmol mol-1 and on populations ofPlantago major originating from altitudes of 0 and 3335 m.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00048150
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  • 9
    Electronic Resource
    Electronic Resource
    Capillary GC-MS — Stable isotope dilution analysis of methylmalonic acid in plasma: A candidate reference method for the diagnosis and the follow-up of methylmalonic acidaemias (1993)
    Springer
    Chromatographia 36 (1993), S. 212-214 
    Details
    ISSN: 1612-1112
    Keywords: Capillary GC-MS ; Methylmalonic acid ; Metabolic diseases ; GC-MS ; Stable isotopes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Because methylmalonic acid (MMA) accumulates in the body fluids of patients suffering from inherited metabolic disorders involving its pathway, the quantitation of this metabolite is not only fundamental to diagnosis but is also important in the follow-up of affected patients under treatment. We describe the method set up and used in our laboratory for the measurement of MMA in body fluids and propose its application to plasma as the reference method for the biochemical diagnosis and follow-up of methylmalonic acidaemias.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263866
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  • 10
    Electronic Resource
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    Quantitative measurement of 4-hydroxy-3-methoxymandelic and homovanillic acids in plasma using capillary gas chromatography-mass spectrometry and stable isotope dilution: Preliminary data (1993)
    Springer
    Chromatographia 36 (1993), S. 179-182 
    Details
    ISSN: 1612-1112
    Keywords: Capillary GC-MS ; 4-Hydroxy-3-methoxymandelic acid ; Homovanillic acid ; Stable isotopes ; Neuroblastoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This report presents a method for the quantitative measurement of 4-hydroxy-3-methoxymandelic acid and homovanillic acid in plasma using gas chromatography, mass fragmentography, and stable isotope dilution. The method is suitable for fast diagnosis of neuroblastoma and for the follow-up of the affected patients: these preliminary results show good discrimination between controls and affected patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263858
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  • 11
    Electronic Resource
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    Energy sources for aquatic animals in the Orinoco River floodplain: evidence from stable isotopes (1992)
    Springer
    Oecologia 89 (1992), S. 324-330 
    Details
    ISSN: 1432-1939
    Keywords: Orinoco River ; Floodplain ; Stable isotopes ; Food webs ; Algae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Stable carbon and nitrogen isotope ratios in autotrophs, aquatic invertebrates and fishes from the Orinoco River floodplain of Venezuela reveal that microalgae, including both phytoplankton and epiphytic (attached) forms, are predominant energy sources for many aquatic animals, even though aquatic vascular plants are much more abundant. Floating mats of the grass Paspalum repens and the water hyacinth Eichhornia spp. harbor particularly high densities of aquatic animals, but isotopic evidence indicates that few species are dependent on organic carbon originating from these plants. The stable isotopic evidence for the trophic importance of algae contradicts traditional interpretations of food webs in freshwater wetlands, which are generally thought to be based largely on detritus originating from vascular plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317409
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  • 12
    Electronic Resource
    Electronic Resource
    Foliar δ13C within a temperate deciduous forest: spatial, temporal, and species sources of variation (1992)
    Springer
    Oecologia 90 (1992), S. 1-7 
    Details
    ISSN: 1432-1939
    Keywords: Stable isotopes ; Deciduous forests ; 13C/12C ratios ; Topographic variation ; Water use efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Foliar 13C-abundance (δ13C) was analyzed in the dominant trees of a temperate deciduous forest in east Tennessee (Walker Branch Watershed) to investigate the variation in foliar δ13C as a function of time (within-year and between years), space (canopy height, watershed topography and habitat) and species (deciduous and coniferous taxa). Various hypotheses were tested by analyzing (i) samples collected from the field during the growing season and (ii) foliar tissues maintained in an archived collection. The δ13C-value for leaves from the tops of trees was 2 to 3%. more positive than for leaves sampled at lower heights in the canopy. Quercus prinus leaves sampled just prior to autumn leaf fall had significantly more negative δ13C-values than those sampled during midsummer. On the more xeric ridges, needles of Pinus spp. had more positive δ13C-values than leaves from deciduous species. Foliar δ13C-values differed significantly as a function of topography. Deciduous leaves from xeric sites (ridges and slopes) had more positive δ13C-values than those from mesic (riparian and cove) environments. On the more xeric sites, foliar δ13C was significantly more positive in 1988 (a dry year) relative to that in 1989 (a year with above-normal precipitation). In contrast, leaf δ13C in trees from mesic valley bottoms did not differ significantly among years with disparate precipitation. Patterns in foliar δ13C indicated a higher ratio of net CO2 assimilation to transpiration (A/E) for trees in more xeric versus mesic habitats, and for trees in xeric habitats during years of drought versus years of normal precipitation. However, A/E (units of mmol CO2 fixed/mol H2O transpired) calculated on the basis of δ13C-values for leaves from the more xeric sites was higher in a wet year (6.6±1.2) versus a dry year (3.4±0.4). This difference was attributed to higher transpiration (and therefore lower A/E) in the year with lower relative humidity and higher average daily temperature. The calculated A/E values for the forest in 1988–89, based on δ13C, were within ±55% of estimates made over a 17 day period at this site in 1984 using micrometeorological methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317801
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  • 13
    Electronic Resource
    Electronic Resource
    Seasonal carbon isotope discrimination in a grassland community (1991)
    Springer
    Oecologia 85 (1991), S. 314-320 
    Details
    ISSN: 1432-1939
    Keywords: Carbon isotope discrimination ; Carbon isotope ratio ; Stable isotopes ; Grassland ; Community ecology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Grassland communities of arid western North America are often characterized by a seasonal increase in ambient temperature and evaporative demand and a corresponding decline in soil moisture availability. As the environment changes, particular species could respond differently, which should be reflected in a number of physiological processes. Carbon isotope discrimination varies during photosynthetic activity as a function of both stomatal aperture and the biochemistry of the fixation process, and provides an integrated measure of plant response to seasonal changes in the environment. We measured the seasonal course of carbon isotope discrimination in 42 grassland species to evaluate changes in gas exchange processes in response to these varying environmental factors. The seasonal courses were then used to identify community-wide patterns associated with life form, with phenology and with differences between grasses and forbs. Significant differences were detected in the following comparisons: (1) Carbon isotope discrimination decreased throughout the growing season; (2) perennial species discriminated less than annual species; (3) grasses discriminated less than forbs; and (4) early flowering species discriminated more than the later flowering ones. These comparisons suggested that (1) species active only during the initial, less stressful months of the growing season used water less efficiently, and (2) that physiological responses increasing the ratio of carbon fixed to water lost were common in these grassland species, and were correlated with the increase in evaporative demand and the decrease in soil moisture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00320605
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  • 14
    Electronic Resource
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    Carbon and nitrogen isotope ratios in different compartments of a healthy and a declining Picea abies forest in the Fichtelgebirge, NE Bavaria (1991)
    Springer
    Oecologia 87 (1991), S. 198-207 
    Details
    ISSN: 1432-1939
    Keywords: δ13C ; δ15N ; Nitrogen assimilation ; Forest decline ; Picea abies ; Stable isotopes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Natural carbon and nitrogen isotope ratios were measured in different compartments (needles and twigs of different ages and crown positions, litter, understorey vegetation, roots and soils of different horizons) on 5 plots of a healthy and on 8 plots of a declining Norway spruce (Picea abies (L.) Karst.) forest in the Fichtelgebirge (NE Bavaria, Germany), which has recently been described in detail (Oren et al. 1988a; Schulze et al. 1989). The δ13C values of needles did not differ between sites or change consistently with needle age, but did decrease from the sun-to the shade-crown. This result confirms earlier conclusions from gas exchange measurements that gaseous air pollutants did no long-lasting damage in an area where such damage was expected. Twigs (δ13C between-25.3 and-27.8‰) were significantly less depleted in 13C than needles (δ13C between-27.3 and-29.1‰), and δ13C in twigs increased consistently with age. The δ15N values of needles ranged between-2.5 and-4.1‰ and varied according to stand and age. In young needles δ15N decreased with needle age, but remained constant or increased in needles that were 2 or 3 years old. Needles from the healthy site were more depleted in 15N than those from the declining site. The difference between sites was greater in old needles than in young ones. This differentiation presumably reflects an earlier onset of nitrogen reallocation in needles of the declining stand. δ15N values in twigs were more negative than in needles (-3.5 to-5.2‰) and showed age- and stand-dependent trends that were similar to the needles. δ15N values of roots and soil samples increased at both stands with soil depth from-3.5 in the organic layer to +4‰ in the mineral soil. The δ15N values of roots from the mineral soil were different from those of twigs and needles. Roots from the shallower organic layer had values similar to twigs and needles. Thus, the bulk of the assimilated nitrogen was presumably taken up by the roots from the organic layer. The problem of separation of ammonium or nitrate use by roots from different soil horizons is discussed.
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    URL: http://dx.doi.org/10.1007/BF00325257
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  • 15
    Electronic Resource
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    Water relations of coastal plant communities near the ocean/freshwater boundary (1991)
    Springer
    Oecologia 88 (1991), S. 305-310 
    Details
    ISSN: 1432-1939
    Keywords: Water potential ; Mangrove ; Hardwood hammock ; Salinity ; Stable isotopes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Salinity and isotope ratios were determined in water from several wells in the Florida Keys, and tidal inlets. Both D/H and 18O/16O ratios of water from wells and tidal inlets were highly correlated to their salinity. Water from standing pools was enriched in deuterium and oxygen-18 relative to their salinity because of evaporation processes. 18O/16O and D/H ratios of stem water from plants of several different communities at Sugar Loaf Key, ranging from hardwood hammocks to mangroves, were highly correlated to their predawn water potential. The correlation was consistent with the presence of high salinity in waters with high 18O and D content. Most individuals from each community were either utilizing water with isotopic characteristics typical of freshwater or of ocean water, while only a few individuals had stem water with isotopic ratios intermediate to these two water sources.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317571
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  • 16
    Electronic Resource
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    Stable isotopic determinations of trophic relationships of great auks (1991)
    Springer
    Oecologia 87 (1991), S. 528-531 
    Details
    ISSN: 1432-1939
    Keywords: Great auk ; Palaeoecology ; Pinguinus impennis ; Stable isotopes ; Trophic relationships
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Stable isotopic ratios of animal tissues are related to those of their foods and can be used in palaeoecological reconstructions, including those of extinct animals. Nitrogen isotopic analyses of marine organisms from coastal Newfoundland and Georges Bank were used to construct a model predicting collagen δ15N values for seabirds feeding at various trophic levels (TL). This model was tested by measuring bone collagen δ15N values of extant alcids from the northwest Atlantic and high Arctic. Isotopic analysis of bone collagen of the extinct great auk (Pinguinus impennis), the last flightless seabird in the northern hemisphere, indicate that this species occupied a trophic continuum from TL3 (crustacean diets) to TL5 (diets of piscivorous fish). We suggest that (a) great auk chicks and juveniles occupied lower trophic levels and probably consumed euphausiids, and (b) great auks fed offspring via regurgitation, as do dovekies (Alle alle), the only extant fully planktivorous alcid in the Atlantic, and unrelated penguins of the southern hemisphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00320416
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