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  • phosphorus  (73)
  • temperature  (56)
  • Springer  (129)
  • American Chemical Society
  • American Meteorological Society
  • 1995-1999  (129)
  • 1990-1994
  • 1955-1959
  • 1999  (129)
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  • Springer  (129)
  • American Chemical Society
  • American Meteorological Society
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  • 1995-1999  (129)
  • 1990-1994
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  • 1
    Electronic Resource
    Electronic Resource
    Langfristige Zunahme früher Bruten beim Teichrohrsänger (Acrocephalus scirpaceus) in einem südwestdeutschen Untersuchungsgebiet (1999)
    Springer
    Journal of ornithology 140 (1999), S. 81-86 
    Details
    ISSN: 1439-0361
    Keywords: Reed Warbler ; timing of breeding ; spring arrival ; global climate change ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung In einem Untersuchungsgebiet am westlichen Bodensee (Halbinsel Mettnau) zeichnet sich zwischen 1976 und 1997 eine deutliche Zunahme früh ausgeflogener Teichrohrsänger ab, was auf ein früheres Brüten schließen läßt. Weiterhin hat sich die Erstankunft des Teichrohrsängers am Bodensee in den letzten 16 Jahren (1982–1997) im Vergleich zum Zeitraum 1961 bis 1980 um genau eine Woche verfrüht (im Mittel vom 26.4. auf den 19.4.). Während sich zwischen der jährlichen Erstankunft des Teichrohrsängers am Bodensee und der Zahl früh ausgeflogener Jungvögel kein statistisch gesicherter Zusammenhang finden läßt, ist die Temperatur in der ersten Maihälfte ein guter (statistisch signifikanter) Indikator für die Zahl früh ausgeflogener Teichrohrsänger. Die vorliegende Untersuchung zeigt, daß sich offenbar auch Langstreckenzieher an die sich abzeichnende Klimaveränderung anzupassen beginnen.
    Notes: Summary Data from a standardized mist-netting programme (the so-called "MRI-Programm") were used to assess the timing of breeding in Reed Warblers (Acrocephalus scirpaceus) at Lake Constance (South Germany). The number of Reed Warblers fledged early in the season increased significantly between 1976 and 1997 (rs=0.614; p〈0.01). This is most probably due to a long-term increase in spring temperature as suggested by the high correlation between the number of early-fledged Reed Warblers and mean temperature in the first half of May (rs=0.416; p〈0.01). While in the period from 1961 to 1980 the mean date of spring arrival was on the 26th of April, it shifted towards the 19th April from 1981 to 1997. However, the number of early-fledged Reed Warblers and the date of spring arrival are not significantly correlated. The lack of a significant correlation may be due to a number of reasons, for instance early arriving birds do not belong to the local population or there could be an observational bias among years. Yet, the most likely explanation is that the timing of breeding in Reed Warblers is triggered by vegetation growth and food supply rather than by the timing of spring arrival. There is growing body of evidence from this and other studies that the recent climate change is responsible for the shift in both the timing of migration and breeding in birds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02462091
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of temperature and photoperiod on development and oviposition of the legume flower thrips, Megalurothrips sjostedti (1999)
    Springer
    Entomologia experimentalis et applicata 93 (1999), S. 149-155 
    Details
    ISSN: 1570-7458
    Keywords: Megalurothrips sjostedti ; temperature ; photoperiod ; development ; pre-oviposition ; oviposition ; diapause
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Megalurothrips sjostedti is an economic pest of cowpea in tropical Africa. There are no reports of the effect of temperature on the development of the pest and no diapause has been detected. The developmental rate and reproduction of M. sjostedti was studied under six constant temperatures (14, 17, 20, 23, 26 and 29 °C ) and a photoperiod of L12:D12 in the laboratory. Total developmental time ranged from 33.1 days at 14 °C to 19.2 days at 26 °C. At 29 °C, all larvae died during hatching. Egg, larval and pupal stages required 94.3, 97.1 and 105.3 deg-days (DD) above a threshold of 8.2, 9.1 and 10.4 °C, respectively, to complete development. Total developmental cycle was completed at 163.9 DD above a threshold of 12.6 °C. Adult longevity was lowest (11.1 days) at 29 °C and highest (28.7 days) at 14 °C. At constant temperatures, the highest pre-oviposition period was observed at 29 °C under a photoperiod of L16:D8. Egg production also ceased at this temperature/photoperiod combination. Total fecundity was highest at 26 °C under L10:D14. At cyclical temperatures, pre-oviposition period was longest (12.4 days) at 20/29 °C under L16:D8. Total fecundity was highest (168.4 eggs) at 14/26 °C under L10:D14, and lowest (8.2 eggs) at 20/29 °C under L16:D8. The significance of these findings in the management of M. sjostedti is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003896919284
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of temperature on bionomics of cotton aphid, Aphis gossypii, on cotton (1999)
    Springer
    Entomologia experimentalis et applicata 90 (1999), S. 25-35 
    Details
    ISSN: 1570-7458
    Keywords: Aphis gossypii ; development ; survival ; fecundity ; intrinsic rate of increase ; life table ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Life table parameters of Aphis gossypii Glover (Homoptera: Aphididae) on Gossypium hirsutum L. were determined at six temperatures (10, 15, 20, 25, 30, and 35 ± 0.5 °C) in the laboratory. Relationships of life table parameters with temperature were described with mathematical equations. Development was fastest at 30 °C, with a pre-larviposition period of 4.6 d. Survival to adult was greatest at 25 °C (81%). Fecundity was highest at 25 °C, with a total fecundity of 28.3 nymphs per female and a mean reproductive rate of 3.1 nymphs per female per day. Threshold temperatures for development in the first through fourth instar and the adult were 8.2, 8.0, 7.2, 6.2 and 7.9 °C, respectively. The durations of these stages, expressed as temperature sums above these thresholds, were 24.2, 23.7, 23.0, 25.5 and 168.8 degree-days (D°), respectively. A. gossypii achieved its maximum net reproductive number (24.4 nymphs per female) and greatest intrinsic rate of increase (0.386 d−1) at 25 °C. The high relative rate of population increase at 25 °C results in a daily population increase of 47% and a doubling time of only 1.8 d, illustrating the tremendous growth capacity of A. gossypii populations under favourable conditions. Compared to literature sources, our source of A. gossypii, fed on cotton, showed a comparatively great heat tolerance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003580413487
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  • 4
    Electronic Resource
    Electronic Resource
    The smaller fruit tortrix, Grapholita lobarzewskii: predicting the phenology of adult emergence (1999)
    Springer
    Entomologia experimentalis et applicata 93 (1999), S. 297-302 
    Details
    ISSN: 1570-7458
    Keywords: smaller fruit tortrix ; Grapholita lobarzewskii ; phenology ; post-diapause development ; temperature ; thermal threshold ; thermal constant ; forecasting ; modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The smaller fruit tortrix, Grapholita lobarzewskii Nowicki, has become a major pest in the recent past in apple orchards north of the Alps. Nevertheless little is known about the biology and the behaviour of this species. The effect of temperature on post-diapause development and survival was studied under controlled conditions in order to establish a basis for the forecasting of adult emergence. Survival was found to be highest at 17 °C and lowest at 11.8 °C. The sex ratio did not differ significantly from 1:1. Based on a linear relationship between temperature and developmental rates, thermal thresholds of 9.6 °C and 9.8 °C were determined for females and males respectively. The thermal constants, i.e., the mean developmental times in physiological time units, were found to be 342 day-degrees for females and 317 day-degrees for males, suggesting a slight protandry. Based on the mean and the variance of the developmental times, a simple temperature-driven phenology model was built using a time-varying distributed delay. The model was validated by visually comparing the predictions with independent observations on adult emergence, and by calculating the temporal deviations of the predictions. In 4 out of 5 years the mean error was less than 3 days. The model was therefore found to give reliable forecasts of the emergence of G. lobarzewskii and can be used to determine the optimal time for the exposure of pheromone traps, the application of pheromone dispensers for mating disruption, and for the timing of insecticide applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003905026249
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  • 5
    Electronic Resource
    Electronic Resource
    Ni–Zn–P alloy deposition from sulfate bath: inhibitory effect of zinc (1999)
    Springer
    Journal of applied electrochemistry 29 (1999), S. 1171-1176 
    Details
    ISSN: 1572-8838
    Keywords: alloys ; cyclic voltammetry ; electrodeposition ; electroless deposition ; nickel ; phosphorus ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Electroless Ni–Zn–P alloy deposition from a sulphate bath, containing sodium hypophosphite as reducer, was investigated. To increase the plating rate, the deposition parameters were optimized. The effect of process parameters (T, pH and [Zn2+]) on the plating rate and deposit composition was examined and it was found that the presence of zinc in the bath has an inhibitory effect on the alloy deposition. As a consequence, the percentage of zinc in the electroless Ni–Zn–P alloys never reaches high values. Using cyclic voltammetry the electrodeposition mechanism of Ni–Zn–P alloys was investigated. It was observed that the zinc deposition inhibits the nickel discharge and, as a consequence, its catalytic activity on hypophosphite oxidation. It was also found that increase in temperature or pH leads to the deposition of nickel rich alloys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003426904395
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  • 6
    Electronic Resource
    Electronic Resource
    Temperature Effects on Soil Mineralization of Polylactic Acid Plastic in Laboratory Respirometers (1999)
    Springer
    Journal of polymers and the environment 7 (1999), S. 101-108 
    Details
    ISSN: 1572-8900
    Keywords: Polylactic acid ; temperature ; respirometers ; soil degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A respirometric system was used to analyze the biodegradation of high molecular weight (120,000 to 200,000 g mol−1) polylactic acid (PLA) plastic films in soil under laboratory conditions. The respirometric system consisted of air-conditioning pretraps, a soil reactor, and a carbon dioxide (CO2) posttrap. A 200-g homogeneous soil mixture of all-purpose potting soil : manure soil : sand [1 : 1 : 1 (w/w)] and 1.5 g of PLA plastic films in 1 × 1-cm2 squares was added to each bottle. The respirometers were placed in a 28, 40, or 55°C water bath for 182 days. Treatments (three replicates) included native corn starch (positive control), polyethylene (Glad Cling Wrap; negative control), and three PLA films: Ca-I (Cargill Dow Polymers LLC, monolayer), GII (Cargill Dow Polymers LLC, Generation II), and Ch-I (Chronopol; monolayer). The degree of polymer mineralization was indicated by the cumulative CO2 liberated from each respirometer. The initial average mineralization rate and total percentage mineralized of the PLA plastic films at 28, 40, and 55°C was 24.3, 41.5, and 76.9 mg/day with a 27, 45, and 70% carbon loss, respectively. No decrease in soil pH was observed after 182 days of mineralization. Hence, increase in soil temperature drastically enhanced the biodegradation of PLA plastic films in soil under laboratory conditions (P 〈 0.0001).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021812418325
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  • 7
    Electronic Resource
    Electronic Resource
    Microstructural characterization and corrosion resistance of Ni–Zn–P alloys electrolessly deposited from a sulphate bath (1999)
    Springer
    Journal of applied electrochemistry 29 (1999), S. 637-645 
    Details
    ISSN: 1572-8838
    Keywords: alloys ; electroless ; microstructure ; morphology ; nickel ; phosphorus ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Electroless Ni–Zn–P alloy coatings were obtained on an iron substrate from a sulfate bath at various pH values. The effects of changes in bath pH on alloy composition, morphology, microstructure and corrosion resistance were studied. Scanning electron microscopy was performed to observe the morphological change of the deposits with bath pH. Coating crystallinity was investigated by grazing incidence asymmetric Bragg X-ray diffraction and transmission electron microscopy. A transition from an amorphous to polycrystalline structure was observed on increasing the bath alkalinity, and thus decreasing the phosphorus content of the alloys. A single crystalline phase corresponding to face-centred-cubic nickel was identified in the alloys obtained from a strong alkaline solution. An increase in zinc percentage up to 23% in the deposits does not change the f.c.c. nickel crystalline structure. Corrosion potential and polarization resistance measurements indicated that the corrosion resistance of electroless Ni–Zn–P alloys depends strongly on the microstructure and chemical composition. The deposits obtained at pH 9.0–9.5 and with 11.4–12.5% zinc and 11.8–11.2% phosphorous exhibited the best corrosion resistance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026441403282
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of Temperature and Relative Humidity on Polylactic Acid Plastic Degradation (1999)
    Springer
    Journal of polymers and the environment 7 (1999), S. 83-92 
    Details
    ISSN: 1572-8900
    Keywords: Polylactic acid ; temperature ; relative humidity ; degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Three high molecular weight (120,000 to 200,000 g mol−1) polylactic acid (PLA) plastic films from Chronopol (Ch-I) and Cargill Dow Polymers (GII and Ca-I) were analyzed for their degradation under various temperature and relative humidity (RH) conditions. Two sets of plastic films, each containing 11 samples, were randomly hung in a temperature/humidity-controlled chamber by means of plastic-coated paper clips. The tested conditions were 28, 40, and 55°C at 50 and 100% RH, respectively, and 55°C at 10% RH. The three tested PLA films started to lose their tensile properties when their weight-average molecular weight (M w) was in the range of 50,000 to 75,000 g mol−1. The average degradation rate of Ch-I, GII, and Ca-I was 28,931, 27,361, and 63,025 M w/week, respectively. Hence, GII had a faster degradation rate than Ch-I and Ca-I under all tested conditions. The degradation rate of PLA plastics was enhanced by the increase in temperature and relative humidity. This trend was observed in all three PLA plastics (Ca-I, GII, and Ch-I). Of the three tested films, Ch-I was the first to lose its mechanical properties, whereas Ca-I demonstrated the slowest loss, with mechanical properties under all tested conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021808317416
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  • 9
    Electronic Resource
    Electronic Resource
    Electrochemical synthesis of cupric oxide powder Part II: Process conditions (1999)
    Springer
    Journal of applied electrochemistry 29 (1999), S. 81-85 
    Details
    ISSN: 1572-8838
    Keywords: cupric oxide ; powder ; current density ; temperature ; sodium sulfate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Electrosynthesis of cupric oxide powder was carried out on a laboratory scale in an electrochemical cell under various experimental conditions. The electrolysis was appraised in terms of the particle size of the cupric oxide product and the anodic dissolution of the copper electrode. Using a previously determined pH value of 7.50, the other optimum electrolysis operating conditions established were a current density of 4000Am−2, temperature of 353K, and Na2SO4 concentration of 0.5m. The optimum values of current efficiency, cell voltage and specific energy consumption for the electrochemical synthesis of cupric oxide powder were determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003464914657
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  • 10
    Electronic Resource
    Electronic Resource
    Sulfate solubility algorithms for CaSO4–NaCl–H2O and Na2SO4–NaCl–H2O in chlor alkali brine at 25, 65, 75 and 85 ∘C (1999)
    Springer
    Journal of applied electrochemistry 29 (1999), S. 525-528 
    Details
    ISSN: 1572-8838
    Keywords: brine ; chlor-alkali cells ; solubility ; sulfate ions ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026405806916
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  • 11
    Electronic Resource
    Electronic Resource
    Effects of repeated manure and fertilizer phosphorus additions on soil phosphorus dynamics under a soybean-wheat rotation (1999)
    Springer
    Biology and fertility of soils 28 (1999), S. 150-155 
    Details
    ISSN: 1432-0789
    Keywords: Key words Phosphorus dynamics ; Olsen ; phosphorus ; Soil phosphorus fractions ; Manure ; Soybean-wheat rotation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Soil P availability and efficiency of applied P may be improved through an understanding of soil P dynamics in relation to management practices in a cropping system. Our objectives in this study were to evaluate changes in plant-available (Olsen) P and in different inorganic P (Pi) and organic P (P0) fractions in soil as related to repeated additions of manure and fertilizer P under a soybean-wheat rotation. A field experiment on a Typic Haplustert was conducted from 1992 to 1995 wherein the annual treatments included four rates of fertilizer P (0, 11, 22 and 44 kg ha–1 applied to both soybean and wheat) in the absence and presence of 16 t ha–1 of manure (applied to soybean only). With regular application of fertilizer P to each crop the level of Olsen P increased significantly and linearly through the years in both manured and unmanured plots. The mean P balance required to raise Olsen P by 1 mg kg–1 was 17.9 kg ha–1 of fertilizer P in unmanured plots and 5.6 kg ha–1 of manure plus fertilizer P in manured plots. The relative sizes of labile [NaHCO3-extractable Pi (NaHCO3-Pi) and NaHCO3-extractable P0 (NaHCO3-P0)], moderately labile [NaOH-extractable Pi (NaOH-Pi) and NaOH-extractable P0 (NaOH-P0)] and stable [HCl-extractable P (HCl-P) and H2SO4/H2O2-extractable P (resisual-P)] P pools were in a 1 : 2.9 : 7.6 ratio. Application of fertilizer P and manure significantly increased NaHCO3-Pi and -P0 and NaOH-Pi, and -P0 fractions and also total P. However, HCl-P and residual-P were not affected. The changes in NaHCO3-Pi, NaOH-Pi and NaOH-P0 fractions were significantly correlated with the apparent P balance and were thought to represent biologically dynamic soil P and act as major sources and sinks of plant-available P.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050477
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  • 12
    Electronic Resource
    Electronic Resource
    Stable isotope (δ13C and δ15N) signatures of sedimented organic matter as indicators of historic lake trophic state (1999)
    Springer
    Journal of paleolimnology 22 (1999), S. 205-221 
    Details
    ISSN: 1573-0417
    Keywords: carbon isotopes ; diatoms ; lake management ; nitrogen isotopes ; phosphorus ; radium-226 ; sediments ; trophic state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract We explored the use of carbon and nitrogen isotopes (δ13C and δ15N) in sedimented organic matter (OM) as proxy indicators of trophic state change in Florida lakes. Stable isotope data from four 210Pb-dated sediment cores were compared stratigraphically with established proxies for historical trophic state (diatom-inferred limnetic total phosphorus, sediment C/N ratio) and indicators of cultural disturbance (sediment total P and 226Ra activity). Diatom-based limnetic total P inferences indicate a transition from oligo-mesotrophy to meso-eutrophy in Clear Lake, and from eutrophy to hypereutrophy in Lakes Parker, Hollingsworth and Griffin. In cores from all four lakes, the carbon isotopic signature of accumulated OM generally tracks trophic state inferences and cultural impact assessments based on other variables. Oldest sediments in the records yield lower diatom-inferred total limnetic P concentrations and display relatively low δ13C values. In the Clear, Hollingsworth and Parker records, diatom-inferred nutrient concentrations increase after ca. AD 1900, and are associated stratigraphically with higher δ13C values in sediment OM. In the Lake Griffin core, both proxies display slight increases before ~1900, but highest values occur over the last ~100 years. As Lakes Clear, Hollingsworth and Parker became increasingly nutrient-enriched over the past century, the δ15N of sedimented organic matter decreased. This reflects, in part, the increasing relative contribution of nitrogen-fixing cyanobacteria to sedimented organic matter as primary productivity increased in these waterbodies. The Lake Griffin core displays a narrow range of both δ13C and δ15N values. Despite the complexity of carbon and nitrogen cycles in lakes, stratigraphic agreement between diatom-inferred changes in limnetic total P and the stable isotope signatures of sedimented OM suggests that δ13C and δ15N reflect shifts in historic lake trophic state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008078222806
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  • 13
    Electronic Resource
    Electronic Resource
    Calibration of diatoms along a nutrient gradient in Florida Everglades Water Conservation Area-2A, USA (1999)
    Springer
    Journal of paleolimnology 22 (1999), S. 413-437 
    Details
    ISSN: 1573-0417
    Keywords: diatoms ; Everglades ; phosphorus ; wetland ; calibration ; multivariate ; Florida
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The relationship between diatom taxa preserved in surface soils and environmental variables at 31 sites in Water Conservation Area 2A (WCA-2A) of the Florida Everglades was explored using multivariate analyses. Surface soils were collected along a phosphorus (P) gradient and analyzed for diatoms, total P, % nitrogen (N), %carbon (C), calcium (Ca), and biogenic silica (BSi). Phosphorus varied from 315-1781 μg g-1, and was not found to be correlated with the other geochemical variables. Canonical correspondence analysis (CCA) was used to examine which environmental variables correlated most closely with the distributions in diatom taxa. Canonical correspondence analysis with forward selection, constrained and partial CCA, and Monte Carlo permutation tests of significance show the most significant changes in diatom assemblages along the P gradient (p 〈 0.01), with additional species differences correlated with soil C, N, Ca, and BSi. Weighted-averaging (WA) regression and calibration models of diatom assemblages to P and BSi were developed. The diatom-based inference model for soil [P] had a high apparent r2 (0.86) with RMSEboot = 218 μg g-1. Indicator diatom species identified by assessing species WA optima and WA tolerance to [P], such as Nitzschia amphibia and N. palea for high [P] (~1300-1400 μ g-1) and Achnanthes minutissima var. scotica and Mastogloia smithii for low [P] (~400-600 μg g-1), may be useful as monitoring tools for eutrophication in WCA-2A as well as other areas of the Everglades. Diatom assemblages analyzed by cluster analysis were related to location within WCA-2A, and dominant taxa within clusters are discussed in relation to the geochemical variables measured as well as hydrology and pH. Diversity of diatom assemblages and a ‘Disturbance Index’ based on diatom data are discussed in relation to the historically P-limited Everglades ecosystem. Diatom assemblages should be very useful for reconstructions of [P] through time in the Florida Everglades, provided diatoms are well preserved in soil cores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008049224045
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  • 14
    Electronic Resource
    Electronic Resource
    Sedimentation patterns of diatoms in Lake Holzmaar, Germany - (on the transfer of climate signals to biogenic silica oxygen isotope proxies) (1999)
    Springer
    Journal of paleolimnology 21 (1999), S. 437-448 
    Details
    ISSN: 1573-0417
    Keywords: diatoms ; temperature ; sediment traps ; seasonal succession ; resuspension ; Lake Holzmaar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The seasonal sedimentation pattern of diatom valves in Lake Holzmaar was investigated during 1995 by deploying sediment traps at three different lake depths. According to the sedimentation pattern, the major reproduction zone of diatoms was restricted to the upper 6 m of the water body. The population growth started late in April and blooms of Cyclotella cf. comensis Grun., which dominates the plankton diatoms, and Fragilaria crotonensis Kitton were collected in traps during June and September, and July, respectively. During summer, the seasonal sedimentation pattern of each taxon, as collected in the upper traps, was reflected in the concentrations in the lowest trap. However, in May and from September onwards, the community composition in the lowest trap and augmented trapping rates suggest both sediment focusing and resuspension of bottom sediments. The temperature signals as recorded by δ18O values of diatom valves should, therefore, reflect integrated temperatures between 0 and 6 m depth. However, temperatures during summer and autumn are expected to be accentuated in the sedimentary record since the isotopic signal is weighted by both the number and the weight-mass of the valves. During summer, the transfer of these signals by the sedimenting diatoms retains the information pattern recorded, while in spring and autumn/winter additional influxes caused by resuspension may somewhat alter those temperature informations. The proxy signals finally stored in the sediments, may, therefore, not precisely represent the successive temperatures currently recorded during 1995 within mid-lake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008022532458
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  • 15
    Electronic Resource
    Electronic Resource
    Environment factors influence in vitro interspecific interactions between A. ochraceus and other maize spoilage fungi, growth and ochratoxin production (1999)
    Springer
    Mycopathologia 146 (1999), S. 43-47 
    Details
    ISSN: 1573-0832
    Keywords: interspecific interactions ; ochratoxin ; Aspergillus ochraceus ; spoilage fungi ; water relations ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The effect of water availability (water activity,aw; 0.995–0.90) and temperature (18–30 °) on in vitro interactions between an ochratoxin producing strain of Aspergillus ochraceus and six other spoilage fungi was assessed in dual culture experiments on a maize meal-based agar medium. Inprimary resource capture of nutrient substrate, A. ochraceus was dominant against many of the interacting species, being able to overgrow and replace A. candidus, and sometimes A. flavus and the Eurotium spp. regardless of aw or temperature. However, with freely available water (0.995 aw) A. alternata and A. niger were dominant, with mutual antagonism between A. ochraceus and A. flavus at 25–30 °C. In the driest conditions tested (0.90 aw) there was also mutual antagonism between A. ochraceus and the two Eurotium spp. Overall, under allconditions tested the Index of Dominance for A. ochraceus was much higher than for other competing species combined suggesting that A. ochraceus wasa good competitive colonist able to replace a numberof other species. However, the growth rate ofA. ochraceus was modified and decreased by the interaction with competitors. Interaction between A. ochraceus and species such as A. alternata (18°C/0.995) and Eurotium spp. (0.995–0.95 and 25–30 °C) resulted in a significant stimulation of ochratoxin production. Theresults are discussed in relation to the effect that environmental factors have on the possible competitiveness of A. ochraceus in the maizegrain ecosystem and the role of ochratoxin in nicheexclusion of competitors.
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    URL: http://dx.doi.org/10.1023/A:1007003316562
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  • 16
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    Controlling soil water content in fertiliser dissolution experiments (1999)
    Springer
    Nutrient cycling in agroecosystems 55 (1999), S. 7-14 
    Details
    ISSN: 1573-0867
    Keywords: fertiliser formulation ; nutrients ; phosphorus ; relative humidity ; soil moisture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phosphorus lost in runoff from agricultural land leads to the enrichment of surface waters and contributes to algal blooms. Fertilisers are one source of this P. To compare the water available P of different fertiliser formulations in the laboratory it is necessary to control environmental conditions, temperature, relative humidity and soil water content, prior to simulating rainfall. Two chambers were designed in which relative humidity and soil water content were controlled using salt solutions. An initial design comprising a sealed chamber with three layers of soil samples over a salt bath was found to be inferior to a single layer design. The changes in water content of soil samples were used to test the single layer chamber in a constant temperature environment (15 °C) using a saturated KCl solution (90% relative humidity). Based on the final soil water content of the samples, the spatial variation within the chamber was within tolerable limits. The single layer chamber was used for a simulation experiment comparing the water available P of two commercial fertilisers. Using a saturated resorcinol solution (95% relative humidity) soil samples were equilibrated at 15 °C for 21 days, fertiliser added, and the water available P measured up to 600 h after fertiliser application. The results indicate that the amount of water available P was related to the fertiliser compound and exponentially related to the time since fertiliser application. It was concluded that the single layer chamber is suitable for controlling relative humidity and soil water content in trials such as these where the water available P of fertilisers are being compared.
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    URL: http://dx.doi.org/10.1023/A:1009816716466
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  • 17
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    Transfers of phosphorus within three dairy farming systems receiving varying inputs in feeds and fertilizers (1999)
    Springer
    Nutrient cycling in agroecosystems 55 (1999), S. 63-75 
    Details
    ISSN: 1573-0867
    Keywords: dairy systems ; feeds ; fertilizers ; phosphorus ; P surplus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Inputs of phosphorus (P) above requirements for production on dairy farms lead to surplus P with increased risk of P transfer in land run-off to surface waters causing eutrophication. The impact of reducing surplus P inputs in purchased feeds and fertilizers on milk and forage production was investigated in a comparison of three dairy farm systems on chalkland soils in southern England over a 3-year period. In accordance with current commercial practice, no attempt was made to regulate P inputs in system 1, which accumulated an average annual surplus of 23 kg P ha-1. Progressive reductions in purchased feed and/or fertilizer inputs into systems 2 and 3 decreased surplus P to 17 and 3 kg ha-1, respectively, without apparently limiting either milk or herbage dry matter production. The estimated reduction in faecal P output from system 3 cows fed a low P diet compared to system 1 cows fed a high P diet was 26%. Milk P concentrations significantly (P 〈0.001) increased in systems 2 and 3 which included maize in the diet. Output of P in milk and meat products, as a proportion of the total dietary P inputs, increased from 28% in system 1 to 36% in system 3. Surplus P was greatest in continuous maize fields receiving both dairy manure and starter P fertilizer. Withholding P fertilizer in system 3 did not reduce P offtake in cut herbage on soils of moderate P fertility. Total annual losses of P in storm run-off and leaching were no greater than annual inputs of P from the atmosphere (0.5 kg ha-1). The results indicate there is scope to reduce surplus P on commercial dairy farms without sacrificing production targets at least in the short term. Purchased feeds are the largest of the P inputs on intensive dairy farms, yet these are rarely quantified on commercial holdings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009860915462
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  • 18
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    Applications of poultry litter and triple superphosphate fertilizer to a sandy soil: effects on soil phosphorus status and profile distribution (1999)
    Springer
    Nutrient cycling in agroecosystems 54 (1999), S. 233-242 
    Details
    ISSN: 1573-0867
    Keywords: leaching ; phosphorus ; poultry litter ; soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract To determine P loadings, added through poultry litter, sufficient to cause downward movement of P from the cultivated layer of a sandy soil, six rates of poultry litter were applied annually for four years to a site in central England. (total loading 0 – 1119 kg P ha-1). A single extra plot also received an extra 1000 kg ha-1 as triple superphosphate (TSP; total loading 2119 kg P ha-1) and three other treatments received 200 – 800 kg ha-1 P as TSP only. Annual soil sampling in 30-cm increments to 1.5-m depth provided information on P build-up in the topsoil and P movement to depth. There were strong linear trends between P balance (P applied – P removed in crops) and total P, Olsen bicarbonate extractable P and water-soluble P in the topsoil. Phosphorus from TSP and poultry litter fell on the same regression lines, suggesting that both would be equally effective as fertilizer sources. We calculated that 100 kg ha-1 surplus total P would increase the Olsen extractable P content by c. 6 mg kg-1 and the water-soluble P by c. 5 mg kg-1. Thus, relatively large amounts of P would need to be applied to raise soil P status. We found some evidence of P movement into the soil layers immediately below cultivation depth. However, neither soil sampling nor soil solution extracted through Teflon water samplers showed evidence of movement into the deep subsoil (1 m) despite large P loadings.
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    URL: http://dx.doi.org/10.1023/A:1009744706679
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  • 19
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    Inorganic phosphorus and manure effects on bahiagrass production on a Spodosol (1999)
    Springer
    Nutrient cycling in agroecosystems 54 (1999), S. 259-266 
    Details
    ISSN: 1573-0867
    Keywords: bahiagrass ; manure ; pasture fertilization ; phosphorus ; phosphorus cycling ; Spodosol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Bahiagrass (Paspalum notatum Flugge) pasture fertilization recommendations have traditionally been based upon clipping studies. Inclusion of P from manure, not originally considered when P recommendations were developed for pastures, may minimize the need for P fertilization without reducing bahiagrass production or P uptake. The objective of this research was to determine if manure contributes greatly to the P crop nutrient requirement. A 2-year field study utilized a factorial arrangement of 0 and 6.9 Mg air-dried manure ha-1 with 0, 17, 34, 51, and 68 kg inorganic P ha-1 from triple superphosphate to evaluate bahiagrass yield, root distribution, and P uptake response on a Myakka fine sand (sandy, siliceous, hyperthermic Aeric Alaquod). Because air-dried manure was used in the field study, a greenhouse study was employed to confirm that there were no differences in bahiagrass yield or P uptake from either air-dried or fresh cattle (Bos spp.) manure sources. There were no manure or manure by P interaction effects on yield or P uptake of bahiagrass indicating that manure source did not effect grass production in the greenhouse. In the field study, bahiagrass roots were distributed into the Bh horizon, and the Bh horizon had at least four times more Mehlich-1 extractable P than that of the Ap horizon. This horizon was most likely acting as a main source for P-uptake by the grass. This observation was further confirmed by no yield response to levels of inorganic P application in 1989. A linear-response-and-plateau (R2=0.196) relationship with a critical point of 15.4 kg P ha-1 was found in 1990. Bahiagrass yield and P uptake were not dependent on P fertilization, either from manure or inorganic P, due to the availability of P from the Bh horizon.
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    URL: http://dx.doi.org/10.1023/A:1009831011649
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  • 20
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    Diapause Induction and Termination in Eggs of the Fruit Tree Red Spider Mite Panonychus Ulmi in Northern Greece (1999)
    Springer
    Experimental and applied acarology 23 (1999), S. 669-679 
    Details
    ISSN: 1572-9702
    Keywords: Panonychus ulmi ; dipause eggs ; overwintering ; dipause termination ; temperature ; photoperiod
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In apple orchards in northern Greece, females of Panonychus ulmi Koch were found to lay diapause eggs from late August to the beginning of October. The course of diapause termination in the field was determined by transferring diapause eggs during winter and early spring from apple orchards with the varieties ‘Starkinson’ and ‘Firiki’ to short days (LD 8:16) (1992–1996), and long days (LD 16:8) (1994–1995), both at 20 °C. Percentages of diapause termination were very low to zero from October to the beginning of January, then progressively increased throughout January and February. Diapause termination in 50% of the eggs occurred in the first half of February in lowland mite populations irrespective of the year and location from which the eggs originated, and about one month earlier in a population originating from an altitude of 300 m. For each sampling date throughout the winter, the mean number of days required for 50% egg hatch at 20 °C (T50%) was similar under either a long (LD 16:8) or a short (LD 8:16) photoperiod. Diapause eggs collected in October 1995 from two orchards and maintained at 0, 5, 10 and 15 °C for various periods were subsequently transferred to 20 °C and LD 8:16, where TP50% was determined. It was shown that temperature, duration of maintenance at the different temperatures and the orchard from which the eggs originated had a significant effect on T50% and therefore on diapause development. Additionally, in our strains diapause intensity was much weaker than in strains from more northern latitudes and was terminated even without any cold exposure. The variation in diapause intensity in different strains of P. ulmi may have an adaptive significance for this widespread species.
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    URL: http://dx.doi.org/10.1023/A:1006232821653
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  • 21
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    Continuous measurements of stress and temperature during testing of a fibre shotcrete pressure plug (1999)
    Springer
    Geotechnical and geological engineering 17 (1999), S. 335-349 
    Details
    ISSN: 1573-1529
    Keywords: underground gas storage ; pressure barrier ; fibre shotcrete ; stress ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The paper describes an investigation of pressure barriers (plugs) for an underground gas storage facility which were to be constructed from fibre shotcrete. An extensive measurement program on a test plug was carried out to verify the suitability of fibre shotcrete for this purpose. The results of stress and temperature measurements carried out during the construction of the test plug and during cyclic loading of the plug to a water pressure up to 13 MPa are presented. The measurement program provided information on the stress and temperature development inside the plug body during hydration and hardening and also on the residual tensile stresses at the interface between the plug and the rock mass after the end of hydration. Another important output was information on the quality of the plug-rock mass interface, which was critical for a possible leakage. The results obtained during the cyclic loading of the plug revealed uneven stress distribution at the contact and in the adjacent rock mass. It also provided information on the rate of stress redistribution at the contact and inside the rock mass. The results were used to modify the technology of the shotcrete technique to be applied in the final plugs. The gas storage facility using the modified design has been in trial operation since the end of 1998.
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    URL: http://dx.doi.org/10.1023/A:1008929726458
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    Adsorption of Reactive Dye on Chitin (1999)
    Springer
    Environmental monitoring and assessment 59 (1999), S. 111-119 
    Details
    ISSN: 1573-2959
    Keywords: adsorbent concentration ; adsorbent size ; adsorption ; chitin ; pH ; reactive dye ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The adsorption of reactive dye on chitin has been investigated with a view to obtain the design data for batch processing of effluents for dye adsorption. The effect of several factors governing the dye adsorption such as the adsorbent concentration, adsorbent size, temperature and pH have been elicited. Desorption of the dye at different temperatures and pH have also been investigated.
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    URL: http://dx.doi.org/10.1023/A:1006072119624
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  • 23
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    Retention of nutrients in river basins (1999)
    Springer
    Aquatic ecology 33 (1999), S. 29-40 
    Details
    ISSN: 1573-5125
    Keywords: denitrification ; nature restoration ; nitrogen ; phosphorus ; riparian areas ; sedimentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Denmark, as in many other European countries, the diffuse losses of nitrogen (N) and phosphorus (P) from the rural landscape are the major causes of surface water eutrophication and groundwater pollution. The export of total N and total P from the Gjern river basin amounted to 18.2 kg ha−1 and 0.63 kg P ha−1 during June 1994 to May 1995. Diffuse losses of N and P from agricultural areas were the main nutrient source in the river basin contributing 76% and 51%, respectively, of the total export. Investigations of nutrient cycling in the Gjern river basin have revealed the importance of permanent nutrient sinks (denitrification and overbank sedimentation) and temporary nutrient storage in watercourses. Temporary retention of N and P in the watercourses thus amounted to 7.2–16.1 g N m−2 yr−1 and 3.7–8.3 g P m−2 yr−1 during low-flow periods. Deposition of P on temporarily flooded riparian areas amounted from 0.16 to 6.50 g P m−2 during single irrigation and overbank flood events, whereas denitrification of nitrate amounted on average to 7.96 kg N yr−1 per running metre watercourse in a minerotrophic fen and 1.53 kg N yr−1 per linear metre watercourse in a wet meadow. On average, annual retention of N and P in 18 Danish shallow lakes amounted to 32.5 g N m−2 yr−1 and 0.30 g P m−2 yr−1, respectively, during the period 1989–1995. The results indicate that permanent nutrient sinks and temporary nutrient storage in river systems represent an important component of river basin nutrient budgets. Model estimates of the natural retention potential of the Gjern river basin revealed an increase from 38.8 to 81.4 tonnes yr−1 and that P-retention increased from −0.80 to 0.90 tonnes yr−1 following restoration of the water courses, riparian areas and a shallow lake. Catchment management measures such as nature restoration at the river basin scale can thus help to combat diffuse nutrient pollution.
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    URL: http://dx.doi.org/10.1023/A:1009947907811
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    Variation in nutrient availability and plant species diversity across forb and graminoid zones of a Northern New England high salt marsh (1999)
    Springer
    Plant ecology 143 (1999), S. 219-228 
    Details
    ISSN: 1573-5052
    Keywords: mineralization ; nitrogen ; phosphorus ; salinity ; stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plant zonation patterns across New England salt marshes have been investigated for years, but how nutrient availability differs between zones has received little attention. We investigated how N availability, P availability, and plant N status varied across Juncus gerardii, Spartina patens, and mixed forb zones of a Northern New England high salt marsh. We also investigated relationships between several edaphic factors and community production and diversity across the high marsh. P availability, soil salinity, and soil moisture were higher in the mixed forb zone than in the two graminoid zones. NH+ 4-N availability was highest in the J. gerardii zone, but NO− 3-N availability and mid season net N mineralization rates did not vary among zones. Plant tissue N concentrations were highest in the mixed forb zone and lowest in the S. patens zone, reflecting plant physiologies more so than soil N availability. Community production was highest in the J. gerardii zone and was positively correlated with N availability and negatively correlated with soil moisture. Plant species diversity was highest in the mixed forb zone and was positively correlated with P availability and soil salinity. Thus, nutrient availability, plant N status, and plant species diversity varied across zones of this high marsh. Further investigation is needed to ascertain if soil nutrient availability influences or is a result of the production and diversity differences that exist between vegetation zones of New England high salt marshes.
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    URL: http://dx.doi.org/10.1023/A:1009887727465
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  • 25
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    Effect of meteorology and nutrient load on oxygen depletion in a Danish micro-tidal estuary (1999)
    Springer
    Aquatic ecology 33 (1999), S. 55-64 
    Details
    ISSN: 1573-5125
    Keywords: estuaries ; nitrogen ; oxygen depletion ; phosphorus ; regression model ; vertical mixing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In a detailed analysis of oxygen saturation in a shallow Danish estuary it was possible to separate the effect of meteorological forcings (i.e. wind and solar radiation) and nutrient loads on oxygen depletion in bottom water. Regression analysis showed that oxygen saturation tied to nitrogen load rather than to phosphorus load. During summer periods of stratification the oxygen saturation could be attributed to the time elapsed after the onset of stratification and the accumulated nitrogen loading 10 month prior to measurement. Using a 10-year meteorological database and an empirical model it was calculated that a 25% reduction in nitrogen loading would reduce the number of days with severe oxygen depletion (i.e. 〈15% of saturation) by more than 50%.
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    URL: http://dx.doi.org/10.1023/A:1009956210537
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  • 26
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    Interactions of light, temperature and inorganic nitrogen in controlling planktonic nitrogen utilisation in the Tagus estuary (1999)
    Springer
    Aquatic ecology 33 (1999), S. 251-261 
    Details
    ISSN: 1573-5125
    Keywords: irradiance ; nitrogen uptake ; phytoplankton ; Tagus estuary ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of light, temperature and ammonium on inorganic nitrogen uptake by phytoplankton was investigated from June 1994 through December 1995 at three sites in the Tagus estuary (Portugal), during high tide of neap tides. Ammonium concentrations higher than 10 μM reduced nitrate uptake down to 24% but never prevented it. Below this threshold concentration, nitrate uptake was neither inhibited nor changed. Uptake of both nitrate and ammonium as a function of light intensity exhibited a saturation response. Uptake reduction occurred in the near bottom phytoplankton populations, particularly for nitrate. The ammonium uptake system was less limited by light than the nitrate uptake system, indicating the importance of ammonium as a nitrogen source for the phytoplankton which is likely to experience high changes in light in the well-mixed water column of this estuarine environment. Ammonium uptake was exponentially related to temperature in the upper estuary whereas in the mid and lower estuary this relationship was linear. The effect of temperature on nitrate uptake was linear but far less marked than for ammonium uptake.
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    URL: http://dx.doi.org/10.1023/A:1009993300873
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  • 27
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    Effects of Potato-cyst Nematodes (Globodera pallida) and Soil pH on Root Growth, Nutrient Uptake and Crop Growth of Potato (1999)
    Springer
    European journal of plant pathology 105 (1999), S. 61-76 
    Details
    ISSN: 1573-8469
    Keywords: core sampling ; foliar nutrient concentrations ; minirhizotrons ; nitrogen ; phosphorus ; potassium ; Rhizolab
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Potato-cyst nematodes (Globodera pallida) cause severe yield losses in potato. Plants infected with potato-cyst nematodes generally have reduced concentrations of nitrogen, phosphorus and potassium in the foliage. This study investigated whether reduced growth of nematode-infected potato is caused by nutrient limitation. Experiments in the field and in containers showed that phosphorus concentration correlated best with total crop biomass at early stages of growth. The role of phosphorus in nematode damage was further investigated in the field and in the Wageningen Rhizolab. The experimental field was infested with potato-cyst nematodes and two levels of nematode density were established by fumigation with a nematicide. Prior applications of calcium carbonate resulted in pHKCl levels of 4.8 and 6.1. Two levels of phosphorus fertiliser were applied: either 0 or 225 kg P ha−1. In the Wageningen Rhizolab, soil of both pH levels from the field was used after treatment with 1 MRad gamma irradiation to kill the nematodes. Subsequently, half of the soil was inoculated with cysts to give a nematode density of 30 viable juveniles per gram of soil. In the field, nine weeks after planting, the total crop biomass ranged from 107 g m−2 for the treatment with nematodes at pHKCl 6.1 without phosphorus fertiliser to 289 g m−2 for the fumigated treatment at pHKCl 4.8 with phosphorus fertiliser. The differences in total biomass for the various treatments were explained by differences in foliar phosphorus concentration. Nematodes induced or aggravated P deficiency and reduced total biomass. This was not the only damage mechanism as at high, non-limiting levels of foliar phosphorus concentration, nematodes still reduced total biomass. In the Wageningen Rhizolab, directly after planting, the number of roots visible against minirhizotrons was reduced by nematodes. However, the increase of root number in the nematode treatment continued longer than in the control, until root number was higher than that of the control. The compensary root growth of the nematode treatment was restricted to the top 30 cm and nematodes reduced rooting depth. High soil pH reduced growth, mainly by reducing the availability of phosphate. Both nematodes and high soil pH reduced nutrient uptake per unit root length. Our results lead us to suggest an interaction between nematodes and soil pH, with nematode damage being higher at pHKCl 6.1 than at pHKCl 4.8.
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    URL: http://dx.doi.org/10.1023/A:1008641511688
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  • 28
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    Effects of Temperature on Growth and Efficiency of Yolk Utilisation in Eggs and Pre-feeding Larval Stages of Atlantic Salmon (1999)
    Springer
    Aquaculture international 7 (1999), S. 81-87 
    Details
    ISSN: 1573-143X
    Keywords: alevin ; Atlantic salmon (Salmo salar) ; development ; egg ; temperature ; thermal tolerance ; yolk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Three embryonic stages of Atlantic salmon (Salmo salar L.) were subjected to eight constant incubation temperatures (4, 7, 10, 12, 14, 16, 19 and 22 °C) exceeding the range usually experienced in natural conditions. A change in thermal tolerance during the embryonic and larval development was registered: pre-hatching stages showed an upper thermal limit at about 16 °C, while hatched larvae survived until 22 °C. Temperature significantly affects developmental rate, resulting in a faster development and, consequently, lower yolk weight percentage at higher temperatures. We found positive relationships between incubation temperature and body size (length and weight) in the less developed stages, in which some yolk remained, but size decreased at increasing temperatures when yolk was completely exhausted.
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  • 29
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    Growth and Chemical Composition of Spirulina Maxima and Spirulina Platensis Biomass at Different Temperatures (1999)
    Springer
    Aquaculture international 7 (1999), S. 261-275 
    Details
    ISSN: 1573-143X
    Keywords: cyanobacteria ; microalgae ; Spirulina ; Spirulina composition ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The influence of temperature on growth and biomass composition of two species of Spirulina, S. maxima and S. platensis used for food was studied. A 4L fermenter with temperature and agitation control was used to cultivate both species. Under continuous light, maximum cell production of 2.4 g l−1 was verified for both cultures studied at temperatures above 25 °C: S. maxima (30 °C and 35 °C) and S. platensis (25 °C and 30 °C). An accentuated lag phase was observed for all cultures at lower temperatures (15–20 °C), and a maximum biomass production of 1.5 g l−1 was achieved. It was also observed that an increase of temperature caused a marked decrease in protein content, while carbohydrate synthesis was stimulated. The concentration of γ-linolenic acid varied from 11–16% for S. maxima and from 12–14% for S. platensis, at the optimum growth temperatures. Greater culture volumes were also studied in order to compare the performance of glass and plastic containers. At optimum growth temperature, S. maxima produced the same cell growth and similar final biomass composition.
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    The globalization of N deposition: ecosystem consequences in tropical environments (1999)
    Springer
    Biogeochemistry 46 (1999), S. 67-83 
    Details
    ISSN: 1573-515X
    Keywords: acidification ; anthropogenic nitrogen ; cations ; nitrate leaching ; nitric oxide ; nitrous oxide ; nutrient limitation ; phosphorus ; productivity ; tropical ecosystems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Human activities have more than doubled the inputs of nitrogen (N) into terrestrial systems globally. The sources and distribution of anthropogenic N, including N fertilization and N fixed during fossil fuel combustion, are rapidly shifting from the temperate zone to a more global distribution. The consequences of anthropogenic N deposition for ecosystem processes and N losses have been studied primarily in N-limited ecosystems in the temperate zone; there is reason to expect that tropical ecosystems, where plant growth is most often limited by some other resource, will respond differently to increasing deposition. In this paper, we assess the likely direct and indirect effects of increasing anthropogenic N inputs on tropical ecosytem processes. We conclude that anthropogenic inputs of N into tropical forests are unlikely to increase productivity and may even decrease it due to indirect effects on acidity and the availability of phosphorus and cations. We also suggest that the direct effects of anthropogenic N deposition on N cycling processes will lead to increased fluxes at the soilwater and soil-air interfaces, with little or no lag in response time. Finally, we discuss the uncertainties inherent in this analysis, and outline future research that is needed to address those uncertainties.
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    URL: http://dx.doi.org/10.1007/BF01007574
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    Ecosystem constraints to symbiotic nitrogen fixers: A simple model and its implications (1999)
    Springer
    Biogeochemistry 46 (1999), S. 179-202 
    Details
    ISSN: 1573-515X
    Keywords: carbon dioxide ; grazing ; nitrogen fixation ; nitrogen limitation ; phosphorus ; shade
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The widespread occurrence ofN limitation to net primary production (NPP) and other ecosystem processes, despite the ubiquitous occurrence ofN-fixing symbioses, remains a significant puzzle in terrestrial ecology. We describe a simple simulation model for an ecosystem containing a generic nonfixer and a symbioticN fixer, based on: (1) a higher cost forN acquisition byN fixers than nonfixers; (2) growth of fixers and fixation ofN only when lowN availability limits the growth of nonfixers, and other resources are available; and (3) losses of fixedN from the system only when the quantity of availableN exceeds plant and microbial demands. Despite the disadvantages faced by theN fixer under these conditions,N fixation and loss adjustN availability close to the availability of other resources, and biomass and NPP in this simple model can be substantially but only transientlyN limited. We then modify the model by adding: (1) losses ofN in forms other than excess availableN (e.g., dissolved organicN, trace gases produced by nitrification); and (2) constraints to the growth and activity ofN fixers imposed by differential effects of shading,P limitation, and grazing. The combination of these processes is sufficient to describe an open system, with input from both precipitation andN fixation, that is nevertheless stronglyN-limited at equilibrium. This model is useful for exploring causes and consequences of constraints toN fixation, and hence ofN limitation, and we believe it will also be useful for evaluating howN fixation and limitation interact with elevatedCO 2 and other components of global enviromental change.
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    URL: http://dx.doi.org/10.1007/BF01007579
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    The impact of accelerating land-use change on the N-Cycle of tropical aquatic ecosystems: Current conditions and projected changes (1999)
    Springer
    Biogeochemistry 46 (1999), S. 109-148 
    Details
    ISSN: 1573-515X
    Keywords: estuaries ; lakes ; marine ; nitrogen ; phosphorus ; rivers ; streams ; temperate ; tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Published data and analyses from temperate and tropical aquatic systems are used to summarize knowledge about the potential impact of land-use alteration on the nitrogen biogeochemistry of tropical aquatic ecosystems, identify important patterns and recommend key needs for research. The tropical N-cycle is traced from pre-disturbance conditions through the phases of disturbance, highlighting major differences between tropical and temperate systems that might influence development strategies in the tropics. Analyses suggest that tropical freshwaters are more frequently N-limited than temperate zones, while tropical marine systems may show more frequent P limitation. These analyses indicate that disturbances to pristine tropical lands will lead to greatly increased primary production in freshwaters and large changes in tropical freshwater communities. Increased freshwater nutrient flux will also lead to an expansion of the high production, N- and light-limited zones around river deltas, a switch from P- to N-limitation in calcareous marine systems, with large changes in the community composition of fragile mangrove and reef systems. Key information gaps are highlighted, including data on mechanisms of nutrient transport and atmospheric deposition in the tropics, nutrient and material retention capacities of tropical impoundments, and N/P coupling and stoichiometric impacts of nutrient supplies on tropical aquatic communities. The current base of biogeochemical data suggests that alterations in the N-cycle will have greater impacts on tropical aquatic ecosystems than those already observed in the temperate zone.
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    URL: http://dx.doi.org/10.1023/A:1006156213761
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    Effects of Temperature on Infection in Capsicum sp. and Nicotiana benthamiana by Impatiens Necrotic Spot Tospovirus (1999)
    Springer
    European journal of plant pathology 105 (1999), S. 509-512 
    Details
    ISSN: 1573-8469
    Keywords: tospovirus ; resistance ; Capsicum sp. ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Infection by two isolates of impatiens necrotic spot tospovirus (INSV) under temperature regimes of 25/18°C (day/night) or 33°C (continuous) was studied in Capsicum annuum (systemically susceptible to tomato spotted wilt tospovirus, TSWV), C. chinense PI 152225 and PI 159236 (reacting hypersensitively to TSWV) and Nicotiana benthamiana (systemically susceptible to both tospoviruses). At 25/18°C infection was systemic in all hosts tested. At 33°C infection in N. benthamiana was systemic whereas in C. annuum and C. chinense it was restricted to the inoculated leaves. The result differed from that reported for TSWV, where high temperature made plants more susceptible, or caused no difference. Exchanging temperature regimes 6 h to 4 days after inoculation did not affect the final results one month later, with plants being only locally infected at 33°C continuous regime, or systemically infected at 25/18°C alternate regime. The two INSV isolates were biologically and serologically stable for 5 passages in N. benthamiana held continuously at 33°C.
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    URL: http://dx.doi.org/10.1023/A:1008742516820
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    The limits of phosphorus removal in wetlands (1999)
    Springer
    Wetlands ecology and management 7 (1999), S. 165-175 
    Details
    ISSN: 1572-9834
    Keywords: flow ; loading ; models ; phosphorus ; removal limits ; wetlands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phosphorus concentrations exported from wetlands are explored via data and a first order model. The graph of outlet concentration versus areal phosphorus loading is used to display these data and the model. For a given wetland, data and models show that P concentrations show an ‘S’ curve response to increasing P loadings. The lower plateau is the background concentration and the upper plateau is the inlet concentration. The position of the ascending limb between the two plateaus is positioned differently for different wetlands. Phosphorus (P) removal in wetlands is often typified by a stable decreasing gradient of P concentrations from inlet to outlet, and an accompanying stable decreasing gradient in P assimilation. Limits to removal are inherent in the physical, chemical and biological processes. A lower outlet concentration limit exists because of the P cycle in the un-impacted wetland. The loading at which the outlet concentration departs from background, the lower knee in the loading curve, varies from wetland to wetland. An upper outlet concentration limit is imposed by the source concentration for extremely high inflows. The first order mass balance equation interpolates between these limits. The model gives further insights about performance within an overall envelope. The water carrying capacity of the wetland precludes flows in excess of the hydraulic conveyance capacity, thus limiting the possible P loadings to the system. Conversely, extremely low hydraulic loadings cause the wetland to be dominated by atmospheric additions and losses. The central tendency of inter-system data in the North American Database is shown to be inadequate to draw generalized conclusions about ecosystem processes in an individual wetland. The proposed ‘one gram rule’ of Richardson, et al. (1997) is shown to be an over-simplification.
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    URL: http://dx.doi.org/10.1023/A:1008415401082
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    Transcript accumulation and utilization of alternate and non-consensus splice sites in rice granule-bound starch synthase are temperature-sensitive and controlled by a single-nucleotide polymorphism (1999)
    Springer
    Plant molecular biology 40 (1999), S. 719-727 
    Details
    ISSN: 1573-5028
    Keywords: amylose ; splicing ; starch synthase ; temperature ; waxy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Granule-bound starch synthase (GBSS), a product of the waxy gene in rice (Oryza sativa L.), is necessary for the synthesis of amylose in the endosperm. In an extended pedigree of 89 rice cultivars, we have previously shown that all cultivars with more than 18% amylose had the sequence AGGTATA at the leader intron 5′ splice site, while all cultivars with a lower proportion of amylose had the sequence AGTTATA. This single-nucleotide polymorphism reduces the efficiency of GBSS pre-mRNA processing. It also results in alternate splicing at multiple sites, some of which have non-consensus sequences. Here we demonstrate that this same G-to-T polymorphism is also associated with differential sensitivity to temperature during the period of grain development. Cultivars with the sequence AGTTATA have a substantial increase in accumulation of mature GBSS transcripts at 18 °C compared to 25 or 32 °C. The selection of leader intron 5′ splice sites is also affected by temperature in these cultivars. A 5′ splice site −93 upstream from that used in high-amylose varieties predominates at 18 °C. At higher temperatures there is increased utilization of a 5′ splice site at −1 and a non-consensus site at +1. Potential implications of differential 5′ splice site selection and associated differences in 3′ splice site selection on transcript stability and translational efficiency are discussed.
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    URL: http://dx.doi.org/10.1023/A:1006298608408
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    Effects of phosphorus nutrition on tiller emergence in wheat (1999)
    Springer
    Plant and soil 209 (1999), S. 283-295 
    Details
    ISSN: 1573-5036
    Keywords: leaf emergence ; phosphorus ; photosynthesis ; tillering ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phosphorus (P) deficiency limits the yield of wheat, particularly by reducing the number of ears per unit of area because of a poor tiller emergence. The objectives of this work were to (i) determine whether tiller emergence under low phosphorus availability is a function of the availability of assimilates for growth or a direct result of low P availability, (ii) attempt to establish a quantitative relation between an index of the availability of P in the plant and the effects of P deficiency on tiller emergence, and (iii) to provide a better understanding of the mechanisms involved in tiller emergence in field-grown wheat. Wheat (Triticum aestivum L., cv. INTA Oasis), was grown in the field under drip irrigation on a typic Argiudol, low in P (5.5 μg P g-1 soil Bray & Kurtz I) in Balcarce, Argentina. Treatments consisted of the combination of three levels of P fertilization 0, 60 and 200 kg P2O5 ha-1, and two levels of assimilate availability, a control (non-shaded) and 65% of reduction in incident irradiance from seedling emergence until the end of tillering (shaded). Phosphorus treatments significantly modified the pattern of growth and development of the plants. Shading reduced the growth and concentration of water-soluble carbohydrates in leaves and stems. Leaf photosynthetic rate at saturating irradiance was reduced by P deficiency, but was not affected by shading. At shoot P concentrations less than 4.2 g P kg-1 the heterogeneity in the plant population increased with respect to the number of plants bearing a certain tiller. At a shoot P concentration of 1.7 g P kg-1 tillering ceased completely. Phosphorus deficiency directly altered the normal pattern of tiller emergence by slowing the emergence of leaves on the main stem (i.e. increasing the phyllochron), and by reducing the maximum rate of tiller emergence for each tiller.
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    URL: http://dx.doi.org/10.1023/A:1004690404870
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    The effect of regeneration burns on the growth, nutrient acquisition and mycorrhizae of Eucalyptus regnans F. Muell. (mountain ash) seedlings (1999)
    Springer
    Plant and soil 210 (1999), S. 273-283 
    Details
    ISSN: 1573-5036
    Keywords: ectomycorrhizae ; Eucalyptus regnans ; forest burns ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This study was conducted to compare the effects on the growth of Eucalyptus regnans seedlings of unheated soil and soil heated to different extents (as indicated by soil colour–bright red or black) in burnt logging coupes, and to separate the effects of heating of the soil on direct nutrient availability and on morphotypes and effectiveness of ectomycorrhizae. Burnt soils were collected from three logging coupes burnt 2, 14 and 25 months previously and unbumt soil from adjacent regrowth forests. Compared to unburnt soil, the early seedling growth was stimulated in black burnt soil from all coupes (burnt 2, 14 and 25 months previously). Seedling growth was generally poor in red burnt soil, especially in soil collected 2 months after burning. However, the concentration of extractable P was extremely high in red burnt soil, especially in soil collected 2 months after burning. In black burnt soil, extractable P was increased in soil 2 months after burning, but not in the soils collected 14 or 25 months after burning. However, both total P content and concentration in seedlings were increased in all collections of black burnt soil. Frequency of ectomycorrhizae was high in seedlings grown in all black burnt soils, but the mycorrhizal mantles were poorly developed in seedlings in black burnt soil collected 2 months after burning. Seedlings were also ectomycorrhizal in red burnt soil, except in soil collected 2 months after burning. Fine root inocula from seedlings grown in black burnt soils collected 14 and 25 months after burning significantly stimulated both seedling growth and P uptake compared with the uninoculated control, whereas the fine root inocula from the seedlings grown in all the other soils did not. These results suggest that, in black burnt soil, both direct nutritional changes and changes in the ectomycorrhizae may contribute to seedling growth promotion after regeneration burns. The generally poor seedling growth in red burnt soils is likely to have been due to N deficiency as the seedlings in these soils were yellow-green and the tissue concentrations of N were significantly lower than in other treatments.
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    URL: http://dx.doi.org/10.1023/A:1004609912315
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    Floral initiation in field-grown forage peas is delayed to a greater extent by short photoperiods, than in other types of European varieties (1999)
    Springer
    Euphytica 109 (1999), S. 201-211 
    Details
    ISSN: 1573-5060
    Keywords: Pisum sativum L. ; frost resistance ; floral initiation ; photoperiod ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Frost is one of the main climatic stresses which has to be overcome by a winter pea crop. Some forage lines show a delayed floral initiation, which helps them to escape the main winter freezing periods, as a higher susceptibility to frost is observed after floral initiation commences. Frost tolerant forage peas have been used in all winter pea breeding programs in France and our main purpose was to evaluate to what extent those lines and the current winter varieties are variable for the date of floral initiation in field conditions. A field experiment was carried out during two years at the INRA experimental station of Mons (northern France). Different genotypes (9 in 1995–1996 and 12 in 1996–1997) were sown at approximately monthly intervals between September and June to provide a range of photothermal conditions. The date of floral initiation was determined by destructive sampling. We observed variability for the date of floral initiation among the different genotypes and sowing dates. Our data particularly highlighted the different reactions to photoperiod. Three varieties had no detectable reaction. Six varieties exhibited a quantitative response, with varied intensities. Lastly, the three forage varieties showed a qualitative, high response to photoperiod, which indicated the presence of the Hr allele, already described in Pisum.
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    URL: http://dx.doi.org/10.1023/A:1003727324475
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    Ammonium and nitrate uptake by Eucalyptus nitens: effects of pH and temperature (1999)
    Springer
    Plant and soil 214 (1999), S. 133-140 
    Details
    ISSN: 1573-5036
    Keywords: ammonium ; eucalyptus ; nitrate ; pH ; root uptake ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Ammonium and nitrate uptake by roots of Eucalyptus nitens was characterised with respect to pH and temperature. Uptake of ammonium and nitrate was measured as depletion from solutions by roots of intact 11 week old solution-cultured seedlings. Uptake rates of ammonium were consistently higher than those of nitrate in all experiments. Uptake rates for ammonium were 200% higher at pH 4 than at pH 6, but for nitrate were unchanged. Uptake rates of ammonium and nitrate were both reduced to a similar extent (70%) with a decrease in temperature from 20 °C to 10 °C. For ammonium uptake, there was rapid (〈24 hr) adaptation to a reduction in root temperature. The apparent preference shown here for ammonium over nitrate could be indicative of E. nitens growing in cold, acidic forest soils where ammonium is commonly more available than nitrate. These results suggest that N uptake rates of E. nitens may be maximised under a wide variety of conditions if N is supplied predominantly in the ammonium form.
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    URL: http://dx.doi.org/10.1023/A:1004740204876
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    Persistence of tree related patterns in soil nutrients following slash-and-burn disturbance in the tropics (1999)
    Springer
    Plant and soil 209 (1999), S. 137-157 
    Details
    ISSN: 1573-5036
    Keywords: fire ; nitrogen ; phosphorus ; soil nutrient heterogeneity ; tree effects ; tropical dry forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Individual trees are known to influence soil chemical properties, creating spatial patterns that vary with distance from the stem. The influence of trees on soil chemical properties is commonly viewed as the agronomic basis for low-input agroforestry and shifting cultivation practices, and as an important source of spatial heterogeneity in forest soils. Few studies, however, have examined the persistence of the effects of trees on soil after the pathways responsible for the effects are removed. Here, we present evidence from a Mexican dry forest indicating that stem-related patterns of soil nutrients do persist following slash-and-burn removal of trees and two years of cropping. Pre-disturbance concentrations of resin extractable phosphorus (P), bicarbonate extractable P, NaOH extractable P, total P, total nitrogen (N) and carbon (C), KCl extractable nitrate (NO3 -), and net N mineralization and nitrification rates were higher in stem than dripline soils under two canopy dominant species of large-stemmed trees with contrasting morphologies and phenologies (Caesalpinia eriostachys Benth. and Forchhammeria pallida Liebm.). These stem effects persisted through slash burning and a first growing season for labile inorganic and organic P, NaOH inorganic P, and plant-available P, and through a second growing season for labile organic P, NaOH organic P, and plant-available P. While stem effects for extractable NO3 -, net nitrification rates, total N and C disappeared after felling and slash burning, these stem effects returned after the first growing season. These results support the view that tree-influenced patterns of soil nutrients do persist after tree death, and that trees contribute to the long-term spatial heterogeneity of forest soils.
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    URL: http://dx.doi.org/10.1023/A:1004503023973
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    Nitrogen and phosphorus requirement of the microbiota in soils of the Bornhöved Lake district (1999)
    Springer
    Plant and soil 212 (1999), S. 173-181 
    Details
    ISSN: 1573-5036
    Keywords: nitrogen ; phosphatase activity ; phosphorus ; protease activity ; soil microbial biomass ; substrate-induced respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Estimating in situ N and P status of the soil microbiota is complicated because microbiological features reflect potentials rather than field conditions. Complementary microbiological assays were, therefore, combined to evaluate the N and P requirement of the microbiota in seven agricultural, grassland and forest topsoils of the Bornhöved Lake district as follows: (i) the sensitivity of the substrate-induced respiration (SIR) to supplemental addition of N and P was monitored during microbial growth and (ii) soil protease and phosphatase activities were analysed and related to soil mass and microbial biomass content. Nitrogen addition increased the maximal SIR rate in all except one soil indicating that the growth of organisms is restricted by this element when easily degradable C source is present. Supplemental N (and in some cases also P) retarded the respiratory response within the first 24 h which suggests microbial sensitivity and/or greater anabolic efficiency. With additional N the maximal SIR rate was most strongly enhanced in topsoils of the beech forest and the dystric alder forest. Thus, the microbial growth in these soils that were below litter horizons seems to be mostly restricted by N. Supplemental P positively affected respiratory response of soils under monoculture, wet grassland and dystric alder forest. In the dystric alder forest soil, high rates of alkaline and unbuffered phosphatase activity were observed when activity was related to either soil mass or microbial biomass content. The data of proteolytic and phospholytic enzymes are discussed with reference to nutrient deficiency and microbial strategy for N and P adsorption.
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    URL: http://dx.doi.org/10.1023/A:1004677427165
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    Root-induced modifications of the exchange of phosphate ion between soil solution and soil solid phase (1999)
    Springer
    Plant and soil 211 (1999), S. 103-110 
    Details
    ISSN: 1573-5036
    Keywords: bioavailability ; isotopic evaluation ; phosphate ion exchange ; phosphorus ; rhizosphere ; soil solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The uptake of phosphorus (P) by roots results in a depletion of phosphate ions (PO4) in the rhizosphere. The corresponding decrease in PO4 concentration in the soil solution (CP) gives rise to a replenishment of P from the solid phase which is time- and CP-dependent. This PO4 exchange which reflects the buffer power of the soil for PO4 also varies with the composition and the physico-chemical conditions of the soil. As root activity can modify these physico-chemical conditions in the rhizosphere, the question arises whether these modifications affect the ability of PO4 bound to the soil solid phase to exchange with PO4 in soil solution. The aim of the present work was to measure and compare the parameters which describe the amount of PO4 bound to soil solid phase that is capable to replenish solution P for both rhizosphere and bulk soils. The soil sample was a P-enriched, calcareous topsoil collected from a long-term fertiliser trial. Rhizosphere soil samples were obtained by growing dense mats of roots at the surface of 3 mm thick soil layer for one week. Three plant species were compared: oilseed rape (Brassica napus L., cv Goeland) pea (Pisum sativum L., cv. Solara) and maize ( Zea mays L., cv. Volga). The time- and CP-dependence of the PO4 exchange from soil to solution were described using an isotopic dilution method. The measured CP values were 0.165 mg P L−1 for bulk soil and 0.111, 0.101 and 0.081 mg P L−1 for rhizosphere soils of maize, pea and rape, respectively. The kinetics of the PO4 exchange between liquid and solid phases of soil were significantly different between rhizosphere and bulk soils. However, when changes in CP were accounted for, the parameters describing the PO4 exchange with time and CP between soil solution and soil solid phase were found to be very close for bulk and rhizosphere soils. For this calcareous and P-enriched soil, plant species differed in their ability to deplete PO4 in solution. The resulting changes in the ability of the soil solid phase to replenish solution PO4 were almost fully explained by the depletion of soil solution P.
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    URL: http://dx.doi.org/10.1023/A:1004485432261
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    Optimum production conditions for different high-quality marine algae (1999)
    Springer
    Hydrobiologia 403 (1999), S. 97-107 
    Details
    ISSN: 1573-5117
    Keywords: Algal growth rate ; salinity ; temperature ; pH ; Nannochloropsis ; Tetraselmis ; Isochrysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The possibility of improving the growth rate of different high-quality marine algae was studied. Optimum culture conditions relative to salinities, temperatures and pH levels were defined for three species of Nannochloropsis, Tetraselmis and Isochrysis. In Nannochloropsis, the optimum production ranges were as follows: 20–40‰, 19–21 °C, without using CO2. The optimum conditions for Tetraselmis were: 20–35‰, 19–21 °C, without using CO2. For Isochrysis, the optimum conditions were: 25–35‰, 24–26 °C, also without using CO2.
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    URL: http://dx.doi.org/10.1023/A:1003725626504
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    Qualitative and quantitative investigations of phytoplankton in Lake Ringsjön, Scania, Sweden (1999)
    Springer
    Hydrobiologia 404 (1999), S. 27-40 
    Details
    ISSN: 1573-5117
    Keywords: phytoplankton ; fish reduction ; phosphorus ; biomanipulation ; blue-green algae ; cyanobacteria ; Microcystis ; Anabaena ; Aphanizomenon ; Aulacoseira ; cryptomonads
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The algal record from Lake Ringsjön covers a period of more than 100 years. Towards the end of the 19th century, the lake had a well-functioning commercial fishery, when a brownish mess began to appear in the water, clogging-up the fishing nets and making fishing difficult. This was the first record of algal problems in the lake. Following complaints from the fishermen, the algal flora was investigated and the mess was stated to be a mass development of diatoms belonging to the genus Melosira ( Aulacoseira). Diatom maxima then appeared regularly in spring and autumn, whereas blue-green algae only occurred occasionally and in low abundances. Between 1900 and 1950, nutrient concentrations slowly increased in the lake. Algal blooms of Anabaena lemmermannii and Gloeotrichia echinulata began to appear in summer. Between 1960 and 1980, the lake developed into a hypertrophic status with extensive blooms of blue-green algae from May to October, including high biomasses of mainly Microcystis spp. This severe pollution started with increased usage of the lake, increased tourism and recreation, intensified farming with the introduction of artificial fertilization, and also the diversion of sewage water from a sewage treatment plant. In 1968, cattle death was reported and in 1981, algal toxicity was verified by mouse bioassay. After a period of extremely poor water quality, the lake began to show signs of improvement as a result of the nutrient and fish reduction programmes. The very heavy blooms of blue-green algae decreased and the duration of blooms became shorter. The Microcystis species were to a certain extent replaced by Anabaena and Aphanizomenon species, and biodiversity of algae increased. With respect to the algal community, the lake has improved considerably, but is still eutrophic and suffers summer blooms of toxic blue-green algae.
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    URL: http://dx.doi.org/10.1023/A:1003757504155
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    Synthesis of theoretical and empirical experiences from nutrient and cyprinid reductions in Lake Ringsjön (1999)
    Springer
    Hydrobiologia 404 (1999), S. 145-156 
    Details
    ISSN: 1573-5117
    Keywords: biomanipulation ; nutrient reduction ; zooplankton ; phytoplankton ; bottom-up ; top-down ; phosphorus ; submerged vegetation ; benthic macrofauna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The reduction in external phosphorus load to Lake Ringsjön during the 1980s, did not result in improved water transparency during the following ten-year period. Furthermore, a fish-kill in the Eastern Basin of the lake, in addition to a cyprinid reduction programme (biomanipulation; 1988–1992), in contrast to theory, did not lead to any increase in zooplankton biomass or size. This absence of response in the pelagic food chain may have been attributed to the increase in abundance of YOY (0+) fish, following the fish reduction programme. Despite the lack of effect on zooplankton, there was a decrease in phytoplankton biomass, a change in species composition and an increase in water transparency following biomanipulation. In 1989, one year after the fish-kill in Eastern Basin, the Secchi depth (summer mean) increased from 60 cm to 110 cm. In the following years, water transparency increased further, despite an increase in phosphorus loading. An unexpected effect of the biomanipulation was an increase in benthic invertebrate and staging waterfowl abundances, which occurred 2–4 years after fish reduction. Hence, the response in the benthic community following biomanipulation was considerably stronger than in the pelagic community. A likely explanation is that reduction in abundance of the benthic feeding fish species bream (Abramis brama), strongly affected the benthic invertebrate fauna. In this paper, we present what we believe happened in Lake Ringsjön, and which processes are likely to have been important at various stages of the restoration process.
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    URL: http://dx.doi.org/10.1023/A:1003788900521
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    Comparison of phosphorus release from littoral and profundal sediments in a shallow, eutrophic lake (1999)
    Springer
    Hydrobiologia 408-409 (1999), S. 175-183 
    Details
    ISSN: 1573-5117
    Keywords: internal loading ; iron ; oxic ; anoxic ; temperature ; macrophyte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The release of phosphorus (P) and iron (Fe) was studied in undisturbed sediment cores from littoral and profundal sediments of shallow, eutrophic Lake Arreskov (Denmark). The cores were incubated for 100 days in darkness under oxic and anoxic conditions at 12 and 19 °C and cumulative fluxes of P and Fe were determined. The littoral sediment showed higher P release than the profundal sediment under both oxic and anoxic conditions, however, the difference was only significant during the first 35 days under anoxic conditions. The release rates of P and Fe were significantly higher under anoxic than under oxic conditions. Sequential extractions of P-fractions in sediment from different depths (0–15 cm) were conducted before and after the experiment. Under anoxic conditions, iron-bound P was the most important fraction for the loss of P from both sediments. The decrease in the iron-bound P pool contributed 54% and 86 % of the loss of total particulate P (TPsed) from littoral and profundal sediments under anoxic conditions, respectively, whereas it under oxic conditions only constituted 25% of the TPsedlost from the littoral sediment. Organic P accounted for 31 and 55% of the TPsedlost from the littoral sediment under anoxic and oxic conditions, respectively, while organic P was unimportant (〈 1%) for the loss of TPsedfrom the profundal sediment under anoxic conditions. This indicates that littoral sediments may contribute significantly to the internal P loading, especially if low O2concentrations occur at the sediment–water interface.
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    Relationships between eutrophication variables: from nutrient loading to transparency (1999)
    Springer
    Hydrobiologia 408-409 (1999), S. 375-387 
    Details
    ISSN: 1573-5117
    Keywords: eutrophication ; multi-lake studies ; phosphorus ; nitrogen ; chlorophyll-a ; transparency ; zooplankton ; macrophytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Monitoring data obtained from 231 freshwater lakes and ponds in the Netherlands, covering the period 1980–1996, were used to analyse the relationships between (a) transparency and chlorophyll-a, and the effect of system characteristics on this relationship, (b) chlorophyll-aand nutrient concentrations, and the effect of biological variables and (c) nutrient concentrations and nutrient loading. (a) Chlorophyll-aimposes a maximum on water transparency, but deviations from this maximum can be large. Reducing chlorophyll-a, therefore, does not guarantee a sufficient improvement of transparency. Soil type and the average depth of a lake were shown to influence the relationship between chlorophyll-aand transparency. (b) The maximum ratios of both chlorophyll-a: total-P and chlorophyll-a: total-N were higher in systems dominated by filamentous cyanobacteria than in systems dominated by other algae, indicating the efficiency of the former group with respect to nutrients. In systems with an areal coverage with submersed macrophytes above 5%, concentrations of chlorophyll-aand nutrients were lower than in systems with lower coverages. The ratios between chlorophyll-aand nutrients were lower at coverages larger than 10%. This indicates both bottom-up and top-down control of algae by macrophytes. Grazing pressure by zooplankton was also found to lower the chlorophyll-a: nutrient ratios. (c) System specific linear relationships were found between the average concentrations of total-P and total-N in the incoming water and the summer mean concentration in the lake. This allows the assessment of admissible loads for individual lakes, with narrower confidence limits compared to traditional relationships based on combined data from many lakes. From the analysis, it is concluded that the chain of relationships from nutrient loading to transparency is complex, and depends on biological variables as well as system characteristics.
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    Relationships of some ecological factors with the associations of vegetation in British rivers (1999)
    Springer
    Hydrobiologia 415 (1999), S. 117-122 
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    ISSN: 1573-5117
    Keywords: vegetation ; floristic associations ; habitat ; enrichment ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During River Habitat Surveys on the physical structure of watercourses in Britain between 1995 and 98, detailed assessments of the floristic associations, physical habitat and water chemistry were made at 165 sites over a wide range of vegetation types. Botanical data from a total of 340 relevés from within these RHS were recorded. The vegetation was classified phyto-sociologically on the basis of the abundance of characteristic species, resulting in 45 aquatic, swamp and mire associations being identified together with nine other communities which could not be completely classified phyto-sociologically. The associations were assigned to 22 alliances, 13 orders and 11 classes excluding communities dominated by filamentous algae. Water enrichment (as soluble and total phosphorus) was the most significant factor for the differentiation of the communities but pH, conductivity and alkalinity were also important.
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    Biomass characterization of Azolla filiculoides grown in natural ecosystems and wastewater (1999)
    Springer
    Hydrobiologia 415 (1999), S. 323-327 
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    ISSN: 1573-5117
    Keywords: biofilter ; productivity ; phosphorus ; water quality ; Azolla
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The aquatic pteridophyte Azolla, a small-leaf floating plant, which lives in symbiosis with a nitrogen fixing cyanobacteria, Anabaena azollae, was widespread throughout water channels and hydrographic basins of Portugal. Azolla is also the aim of a study for its utilization as a biofilter for wastewater purification, namely for phosphorus removal (± 36%). The goal of this work is to compare the growth characteristics and biomass composition of this water fern in natural ecosystems with those obtained in some wastewaters. Plant growth rate (0.107± 0.037 d-1) and productivity (5.8 g dw m-2 d-1) suggest that Azolla can grow well in partially treated domestic wastewater, but not in diluted pig wastes. This fact, associated to its biomass composition, namely in phosphorus content (1.38 ±0.20%), increase the possibility of this plant being used to improve wastewater discharge quality. It may also be possible to use the biomass as a biofertiliser or as a feed supplement for aquatic and terrestrial animals due to its protein, crude fiber and mineral content.
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    URL: http://dx.doi.org/10.1023/A:1003824426183
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    The nutritional status and digestibility of Oreochromis niloticus L. diet in Lake Langeno, Ethiopia (1999)
    Springer
    Hydrobiologia 416 (1999), S. 97-106 
    Details
    ISSN: 1573-5117
    Keywords: Oreochromis niloticusL. ; Lake Langeno ; diet ; algal-detritus ; chemical nutrients ; assimilation efficiency ; condition factor ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The composition, nutrient content and digestibility of the diet of Oreochromis niloticus were studied based on stomach and rectal samples collected monthly between December, 1995, and December, 1996, from Lake Langeno. The diet of O. niloticus was composed of a mixture of algal-based detritus, macrophyte scraps, phytoplankton and silt. Inorganic silt, macrophytes and detritus were more dominant in the diet during the wet than in the dry season. Total organic matter (TOM) in the diet was generally low (413 mg g-1 d.w.) reflecting the high proportion of inorganic silt in all seasons. Carbohydrates, proteins and lipids were important nutrients and constituted on average about 139, 185 and 57 mg g-1 d.w., respectively. The levels of all these nutrients varied significantly (ANOVA, P〈0.0001) between months and declined during the wet season. Variation was observed in the ability of the fish to digest and absorb the different components of the food. Protein (41%) was better assimilated than total organic matter (32.7%), carbohydrate (31.7) or lipids (29.8%). The quality of the food expressed as P:E ratio (18.6-28.8 mg KJ-1) ranged from inadequate to adequate. The condition factor (CF) of the fish varied significantly between months in males (ANOVA, F=12.99, p〈0.0001) and females (ANOVA, F=14.46, p〈0.0001). It is concluded that the relatively poor condition factor (CF= 1.67) of O. niloticus in Lake Langeno, compared with other Rift Valley Lakes, follows from the low organic matter content and high proportion of inorganic silt in the diet.
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    Effects of genotype and environment on phenotypic variability in Limnocythere inopinata (Crustacea: Ostracoda) (1999)
    Springer
    Hydrobiologia 400 (1999), S. 85-114 
    Details
    ISSN: 1573-5117
    Keywords: morphology ; clone ; temperature ; salinity ; parthenogenesis ; sexual reproduction ; cluster genotype ; general purpose genotype ; clonal taxonomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Limnocythere inopinata (Baird) is a Holarctic species, widely distributed in non-marine waters, and mainly occurring in unisexual populations. It displays polymorphic traits which could be useful for taxonomical and (palaeo)ecological purposes, if the origin of these traits could be better understood. Three clones of L. inopinata were cultured in the laboratory under various temperature and salinity conditions (i.e. temperature 15, 20 and 25 °C, salinity expressed as electrical conductivity 400, 2000, 5000 and 8000 μS cm−1). Morphological traits for both the valves (shape and size) and soft parts (11 limb setae) were observed. Field populations from Chinese salt lakes and from Austrian lakes were also compared. The freshwater population from Mondsee and its derived clone M develop larger valves than those of the other two clones, clone N (from Neusiedlersee) and clone S (from Seewinkel, Oberer Stinkersee), which live exclusively in saline (alkaline) water. Parthenogenetic specimens from the freshwater lake Mondsee and sexually reproducing females from the Chinese salt lakes both have sub-rectangular valves with straight dorsal margin; the saline clones and populations have highly arched valves with rounded dorsal margin. No direct effects of temperature or salinity on valve ornamentation (reticulation, nodation) have been found. At least for nodation, a genetic factor seems apparent, as the saline clones N and S are never nodose, while the freshwater animals from Mondsee and the sexual animals from the Chinese salt lakes can be both with or without nodes. In the former case, number and position of nodes are variable. Both absolute and relative length of limb setae can be affected by environmental factors and by genotype, and this is the first time that this has been demonstrated in non-marine ostracods. Based on the present observations and experiments, it is concluded that L. inopinata is a variable, polymorphic species, consisting of a (semi-) continuous morphological cluster, in which both clonal genotypes and sexual haplotypes are nested. Therefore, Limnocythere sappaensis Staplin and L. binoda Huang are considered synonyms of L. inopinata; L. mongolica Daday is a possible synonym; L. sanctipatricii sensu Huang and L. dubiosa sensu Huang from Lake Qinghai are most likely erroneous identifications. Apparently recognisable clones with typical ecologies cannot be allocated a taxonomic rank, as this does not reflect a phylogenetic reality. Such links between recognisable morphologies and typical ecological ranges are useful for palaeoenvironmental reconstructions, but are applicable at a regional scale only.
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    Factors affecting food consumption and growth of walleye, Stizostedion vitreum, larvae in culture ponds (1999)
    Springer
    Hydrobiologia 400 (1999), S. 129-140 
    Details
    ISSN: 1573-5117
    Keywords: fish ; energetics ; temperature ; feeding ; prey abundance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract I examined food consumption and growth of walleye larvae in extensive culture ponds using direct methods and a bioenergetics model, and compared my results with laboratory feeding and growth studies. Walleye showed a diel pattern of increasing gut fullness during daylight hours. Larvae exhibited lower maximum food consumption rates in the ponds than predicted from previous short-term laboratory feeding studies. Direct estimates and bioenergetics model estimates of daily food consumption in the culture ponds were in poor agreement and the discrepancy varied with respect to walleye size. Food consumption rates in the ponds were related to walleye size (direct estimates) or water temperature (bioenergetics model estimates) but not zooplankton abundance. Growth exceeded 0.10 g g−1 d−1 for all but one sampling interval and the maximum growth rate in the culture pond fish was double the maximum growth rate determined in the laboratory. Growth was positively related to pond temperature and negatively related to walleye mass, but was not significantly related to zooplankton abundance. Gross conversion efficiency was negatively related to walleye mass, positively related to zooplankton abundance and not related to temperature. Food consumption and growth of walleye larvae in the field may be food-limited at much lower prey abundances than previous laboratory research has suggested.
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    URL: http://dx.doi.org/10.1023/A:1003755115000
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    Influence of Solar Ultraviolet Radiation on Early Life-history Stages of the Bluegill Sunfish, Lepomis macrochirus (1999)
    Springer
    Environmental biology of fishes 55 (1999), S. 307-319 
    Details
    ISSN: 1573-5133
    Keywords: embryo survival ; dissolved organic carbon ; DOC ; nest depth distribution ; development times ; temperature ; underwater UVR environments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined the effect of UVR on the success of early life history stages of Lepomis macrochirus in two lakes with contrasting underwater UVR environments. We tested the prediction that when exposed to similar amounts of UVR, bluegill embryos from lakes with high UVR environments have lower mortality than those from lakes with low UVR. We measured embryo survival in the two lakes by performing three experiments in which ambient UVR was manipulated. Embryos responded similarly to UVR exposure regardless of the lake of origin. However, UV-B in UVR transparent lakes is a potentially important factor in the success of early life history stages of the bluegill. A survey of the natural nesting depths in the two lakes revealed that the median depth at which bluegills construct their nests was greater in Lake Giles (high underwater UVR environment) than in Lake Lacawac (low underwater UVR environment).
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    A simulation model of organic matter and nutrient accumulation in mangrove wetland soils (1999)
    Springer
    Biogeochemistry 44 (1999), S. 93-118 
    Details
    ISSN: 1573-515X
    Keywords: Everglades National Park ; mangrove soils ; organic matter ; nitrogen ; phosphorus ; sedimentation ; simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The distribution and accumulation of organic matter, nitrogen (N) and phosphorus (P) in mangrove soils at four sites along the Shark River estuary of south Florida were investigated with empirical measures and a process-based model. The mangrove nutrient model (NUMAN) was developed from the SEMIDEC marsh organic matter model and parameterized with data from mangrove wetlands. The soil characteristics in the four mangrove sites varied greatly in both concentrations and profiles of soil carbon, N and P. Organic matter decreased from 82% in the upstream locations to 30% in the marine sites. Comparisons of simulated and observed results demonstrated that landscape gradients of soil characteristics along the estuary can be adequately modeled by accounting for plant production, litter decomposition and export, and allochthonous input of mineral sediments. Model sensitivity analyses suggest that root production has a more significant effect on soil composition than litter fall. Model simulations showed that the greatest change in organic matter, N, and P occurred from the soil surface to 5 cm depth. The rapid decomposition of labile organic matter was responsible for this decrease in organic matter. Simulated N mineralization rates decreased quickly with depth, which corresponded with the decrease of labile organic matter. The increase in organic matter content and decrease in soil bulk density from mangrove sites at downstream locations compared to those at upstream locations was controlled mainly by variation in allochthonous inputs of mineral matter at the mouth of the estuary, along with gradients in mangrove root production. Research on allochthonouns sediment input and in situ root production of mangroves is limited compared to their significance to understanding nutrient biogeochemistry of these wetlands. More accurate simulations of temporal patterns of nutrient characteristics with depth will depend on including the effects of disturbance such as hurricanes on sediment redistribution and biomass production.
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    URL: http://dx.doi.org/10.1007/BF00993000
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    Nutrient budgets and biogeochemistry in an experimental agricultural watershed in Southeastern China (1999)
    Springer
    Biogeochemistry 45 (1999), S. 1-19 
    Details
    ISSN: 1573-515X
    Keywords: Chaohu Lake ; chemical fertilizer ; cycling ; denitrification ; multipond system ; nitrogen ; nutrient budget ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract During a two-year field study, an annual nutrient budget and cycles were developed for a small agricultural watershed. The study emphasized the integrated unit of the watershed in understanding the biogeochemistry. It was found that the total nutrient input was 39.1× 104 kg nitrogen and 3.91×104 kg phosphorus in the year 1995, of which the greatest input of nutrients to the watershed was chemical fertilizer application, reaching 34.7×104 kg (676 kg/ha) nitrogen and 3.88×104 kg (76 kg/ha) phosphorus. The total nutrient output from the watershed was 13.55×104 kg nitrogen and 0.40×104 kg phosphorus, while the largest output of nitrogen was denitrification, accounting for 44.1% of N output; the largest output of phosphorus was sale of crops, accounting for 99.4% of P output. The results show that the nutrient input is larger than output, demonstrating that there is nutrient surplus within the watershed, a surplus which may become a potential source of nonpoint pollution to area waters. The research showed that both denitrification and volatilization of nitrogen are key ways of nitrogen loss from the watershed. This suggests that careful management of fertilizer application will be important for the sustainable development of agriculture. The research demonstrated that a multipond system within the watershed had high retention rate for both water and nutrients, benefiting the water, nutrient and sediment recycling in the terrestrial ecosystem and helping to reduce agricultural nonpoint pollution at its source. Therefore, this unique watershed system should be recommended due to its great potential relevance for sustainable agricultural development.
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    Nutrient losses in runoff from grassland and shrubland habitats in Southern New Mexico: I. rainfall simulation experiments (1999)
    Springer
    Biogeochemistry 45 (1999), S. 21-34 
    Details
    ISSN: 1573-515X
    Keywords: Chihuahuan desert ; desert ; desertification ; grassland ; nitrogen ; nutrient budgets ; phosphorus ; runoff
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Rainfall simulation experiments were performed in areas of semiarid grassland (Bouteloua eriopoda) and arid shrubland (Larrea tridentata) in the Chihuahuan desert of New Mexico. The objective was to compare the runoff of nitrogen (N) and phosphorus (P) from these habitats to assess whether losses of soil nutrients are associated with the invasion of grasslands by shrubs. Runoff losses from grass- and shrub-dominated plots were similar, and much less than from bare plots located in the shrubland. Weighted average concentrations of total dissolved N compounds in runoff were greatest in the grassland (1.72 mg/1) and lowest in bare plots in the shrubland (0.55 mg/1). More than half of the N transported in runoff was carried in dissolved organic compounds. In grassland and shrub plots, the total N loss was highly correlated to the total volume of discharge. We estimate that the total annual loss of N in runoff is 0.25 kg/ha/yr in grasslands and 0.43 kg/ha/yr in shrublands — consistent with the depletion of soil N during desertification of these habitats. Losses of P from both habitats were very small.
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    URL: http://dx.doi.org/10.1007/BF00992871
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    Pore water N and P concentration in a floodplain marsh of the Lower Paraná River* (1999)
    Springer
    Hydrobiologia 392 (1999), S. 65-71 
    Details
    ISSN: 1573-5117
    Keywords: nitrogen ; phosphorus ; pore water ; macrophyte ; floodplain ; Paraná River
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Inorganic nitrogen and soluble reactive phosphate (o-P) concentrations were measured in the water of a marsh and in its interstitial water at two sites, and in the river water of a floodplain marsh of the Lower Paraná River. These values were compared with the N and P concentration in sediments and macrophyte biomass in order to assess nutrient availability, fate and storage capacity. High variability was found in the interstitital water using a 1 cm resolution device. Nitrate was never detected in the pore water. Depth averaged NH4 + concentrations in the upper 30 cm layer often ranged from N = 1.5 to 1.8 mg l-1, but showed a pronounced minimum (0.5–0.7 mg l-1), close to (March 95), or relatively soon after (May 94) the end of the macrophyte growing season. Soluble phosphate showed a large variation between P = 0.1–1.1 mg l-1 without any discernible seasonal pattern. NH4 + depletion in the pore water concentration and low N/P ratios (3.7 by weight) within the macrophyte biomass at the end of the growing period suggest that available N limits plant growth. NH4 + and o-P concentrations were 35 and 7 times higher, respectively, in the pore water than in the overlying marsh, suggesting a permanent flux of nutrients from the sediments. o-P accumulate in the marsh leading to higher concentrations than in the incoming river. NH4 + did not accumulate in the marsh, and no significant differences were observed between the river and the marsh water, while the NO3 - contributed by the river water was depleted within the marsh, caused probably by coupled nitrification-denitrification at the sediment–water interface. Although an order of magnitude smaller, the pore water pool can supply enough nutrients to build up the macrophyte biomass pool, but only if a fast turnover is attained. The Paraná floodplain marsh retains a large amount of nutrients being stored mainly in the sediment compartment.
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    Poor water quality in Loch Leven (Scotland) in 1995 in spite of reduced phosphorus loadings since 1985: the influences of catchment management and inter-annual weather variation (1999)
    Springer
    Hydrobiologia 403 (1999), S. 135-151 
    Details
    ISSN: 1573-5117
    Keywords: lake ; phosphorus ; loading ; restoration ; Loch Leven ; Scotland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Eight tonnes of phosphorus in all forms (total phosphorus, TP) entered Loch Leven from its catchment in 1995, compared to 20 t in 1985. Diffuse run-off from the land, and waste from over-wintering geese contributed 59% of the total loading in 1995 cf. 42% in 1985. Point-sources of sewage, and waste-water from fish-rearing ponds, produced the rest. Inputs of phosphorus in soluble reactive form (SRP) totalled 5 t, i.e. 63% of the TP loading in 1995, as compared with 1985 values of 11.8 t and 59%. Point-sources of SRP contributed 54% of the total SRP input in 1995 cf. 69% in 1985. Loadings from three sewage treatment works (STW) totalled 3.1 t TP in 1995 as compared with 5.3 t in 1985; this included 2.6 t SRP (cf. 3.6 t). Daily per capita outputs of the upgraded Kinross North and Milnathort STWs were 0.68 g and 0.81 g TP, respectively, compared with pre-upgrade values of 1.77 g and 2.03 g. Nett reductions in TP and SRP loadings between 1985 and 1995, are 55% and 59% respectively. These values are attributable as much to the lower rainfall of 890 mm over the period of study in 1995, compared to 1250 mm in 1985, as to ‘managed’ elimination of P usage at a major industrial source, and upgrades of STWs. In spite of these cutbacks, a combination of the lower rainfall and an extraordinarily hot summer in 1995 negated the expected reduction in lake phosphorus and chlorophyll levels. The lowered specific areal loading of ca. 0.7 g P m−2 estimated for 1995 still considerably exceeds the ideal maximum for the loch. These statistics nevertheless ignore the significance of a reduction of ca. 7 t in P entering the system in bio-available form, a recently completed upgrade of a major STW and channelling of effluent from a small works out of the catchment.
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    Simulating the effects of biomanipulation on the food web of Lake Ringsjön (1999)
    Springer
    Hydrobiologia 404 (1999), S. 131-144 
    Details
    ISSN: 1573-5117
    Keywords: phosphorus ; model ; excretion ; grazing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A dynamic, process-oriented, deterministic and phosphorus-based model was developed to simulate the food web dynamics of Lake Ringsjön, in particular the long-term effects of biomanipulation in terms of reduction of omnivorous fish. The model contains 14 state variables, each with a differential equation describing sources and sinks of phosphorus. The state variables encompass piscivorous and omnivorous fish, zooplankton, phytoplankton, sediment and lake water. The model simulates densities of fish and phytoplankton adequately, both before and after biomanipulation, although the actual lake phytoplankton density varied more year-to-year compared to the model predictions. According to the model, a biomanipulation will cause an increase in zooplankton biomass. This prediction contradicts available field data from the lake which do not indicate any significant change in zooplankton biomass resulting from the performed biomanipulation. This discrepancy may partly be attributed to structural uncertainties in the model, related to the size structure of predators on zooplankton, i.e. the omnivorous fish community. The simulations suggest that phosphorus was routed along the pelagic food chain to a larger extent after omnivorous fish were removed, whereas the amount of phosphorus routed via the sediment and benthivorous fish decreased following fish removal. Accordingly, translocation of phosphorus from sediment to water by benthivorous fish is predicted to be substantially reduced by biomanipulation, resulting in an overall reduction in the release of new phosphorus to phytoplankton. Irrespective of simulated fishing effort (reduction of ≤0.5% d−1 for two years), the model predicts that P-release from the sediment and the external load will remain sufficiently high to force the system back to its previous state within a decade. Thus, recurrent biomanipulations and/or combined abatement strategies may be necessary to maintain low phytoplankton density. Known structural model uncertainties may however affect the robustness of such detailed predictions about the system resilience.
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    Internal phosphorus loading in Lake Ringsjön (1999)
    Springer
    Hydrobiologia 404 (1999), S. 19-26 
    Details
    ISSN: 1573-5117
    Keywords: sediment ; phosphorus ; eutrophication ; biomanipulation ; fish ; Sweden
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake Ringsjön did not respond with decreased algal production following a substantial reduction in external phosphorus loading. This is typical of many shallow lakes which for decades have received excessive amounts of nutrients. The inertia is due to large amounts of phosphorus (P) stored in sediments and biota, causing internal phosphorus loading. Much of this phosphorus is thought to be released from the organic-rich profundal sediments. In Lake Ringsjön, only one third of the total bottom area is covered by such sediments, the rest being dominated by sand and silt. In the profundal sediments bulk P content was not exceptionally high (approximately 2 mg P·g DW−1), while the pore water phosphate concentrations, especially in Sätofta Basin, were very high, indicating large potential for phosphorus release to the water. This is also indicated by the large proportion of Fe- and Al-bound P in the sediments of Sätofta Basin. Although there are no direct quantifications of phosphorus release from the sediments in Lake Ringsjön, measurements of phosphorus concentrations in the water mass as well as budget calculations for the three basins clearly show a high capacity for internal loading. Phosphorus concentrations generally increase during summer, when external additions are minimal. Until 1980, the annual external phosphorus addition to Lake Ringsjön greatly exceeded the output, showing that the lake was an efficient phosphorus trap. Since then, input and output have been balanced, but in recent years signs that the lake is once again retaining phosphorus on an annual basis are evident. There are marked differences between the three basins, with Western Basin generally retaining phosphorus, while the upstream Eastern Basin and Sätofta Basin during the 1980s often exported phosphorus. It is not possible to evaluate the effects of the fish biomanipulation on the internal loading of phosphorus from the sediment.
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    Simulating the effects of biomanipulation on the food web of Lake Ringsjön (1999)
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    Hydrobiologia 404 (1999), S. 131-144 
    Details
    ISSN: 1573-5117
    Keywords: phosphorus ; model ; excretion ; grazing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A dynamic, process-oriented, deterministic and phosphorus-based model was developed to simulate the food web dynamics of Lake Ringsjön, in particular the long-term effects of biomanipulation in terms of reduction of omnivorous fish. The model contains 14 state variables, each with a differential equation describing sources and sinks of phosphorus. The state variables encompass piscivorous and omnivorous fish, zooplankton, phytoplankton, sediment and lake water. The model simulates densities of fish and phytoplankton adequately, both before and after biomanipulation, although the actual lake phytoplankton density varied more year-to-year compared to the model predictions. According to the model, a biomanipulation will cause an increase in zooplankton biomass. This prediction contradicts available field data from the lake which do not indicate any significant change in zooplankton biomass resulting from the performed biomanipulation. This discrepancy may partly be attributed to structural uncertainties in the model, related to the size structure of predators on zooplankton, i.e. the omnivorous fish community. The simulations suggest that phosphorus was routed along the pelagic food chain to a larger extent after omnivorous fish were removed, whereas the amount of phosphorus routed via the sediment and benthivorous fish decreased following fish removal. Accordingly, translocation of phosphorus from sediment to water by benthivorous fish is predicted to be substantially reduced by biomanipulation, resulting in an overall reduction in the release of new phosphorus to phytoplankton. Irrespective of simulated fishing effort (reduction of ≤0.5% d−1 for two years), the model predicts that P-release from the sediment and the external load will remain sufficiently high to force the system back to its previous state within a decade. Thus, recurrent biomanipulations and/or combined abatement strategies may be necessary to maintain low phytoplankton density. Known structural model uncertainties may however affect the robustness of such detailed predictions about the system resilience.
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    Internal phosphorus loading in Lake Ringsjön (1999)
    Springer
    Hydrobiologia 404 (1999), S. 19-26 
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    ISSN: 1573-5117
    Keywords: sediment ; phosphorus ; eutrophication ; biomanipulation ; fish ; Sweden
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake Ringsjön did not respond with decreased algal production following a substantial reduction in external phosphorus loading. This is typical of many shallow lakes which for decades have received excessive amounts of nutrients. The inertia is due to large amounts of phosphorus (P) stored in sediments and biota, causing internal phosphorus loading. Much of this phosphorus is thought to be released from the organic-rich profundal sediments. In Lake Ringsjön, only one third of the total bottom area is covered by such sediments, the rest being dominated by sand and silt. In the profundal sediments bulk P content was not exceptionally high (approximately 2 mg P·g DW−1), while the pore water phosphate concentrations, especially in Sätofta Basin, were very high, indicating large potential for phosphorus release to the water. This is also indicated by the large proportion of Fe- and Al-bound P in the sediments of Sätofta Basin. Although there are no direct quantifications of phosphorus release from the sediments in Lake Ringsjön, measurements of phosphorus concentrations in the water mass as well as budget calculations for the three basins clearly show a high capacity for internal loading. Phosphorus concentrations generally increase during summer, when external additions are minimal. Until 1980, the annual external phosphorus addition to Lake Ringsjön greatly exceeded the output, showing that the lake was an efficient phosphorus trap. Since then, input and output have been balanced, but in recent years signs that the lake is once again retaining phosphorus on an annual basis are evident. There are marked differences between the three basins, with Western Basin generally retaining phosphorus, while the upstream Eastern Basin and Sätofta Basin during the 1980s often exported phosphorus. It is not possible to evaluate the effects of the fish biomanipulation on the internal loading of phosphorus from the sediment.
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    Qualitative and quantitative investigations of phytoplankton in Lake Ringsjön, Scania, Sweden (1999)
    Springer
    Hydrobiologia 404 (1999), S. 27-40 
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    ISSN: 1573-5117
    Keywords: phytoplankton ; fish reduction ; phosphorus ; biomanipulation ; blue-green algae ; cyanobacteria ; Microcystis ; Anabaena ; Aphanizomenon ; Aulacoseira ; cryptomonads
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The algal record from Lake Ringsjön covers a period of more than 100 years. Towards the end of the 19th century, the lake had a well-functioning commercial fishery, when a brownish mess began to appear in the water, clogging-up the fishing nets and making fishing difficult. This was the first record of algal problems in the lake. Following complaints from the fishermen, the algal flora was investigated and the mess was stated to be a mass development of diatoms belonging to the genus Melosira ( Aulacoseira). Diatom maxima then appeared regularly in spring and autumn, whereas blue-green algae only occurred occasionally and in low abundances. Between 1900 and 1950, nutrient concentrations slowly increased in the lake. Algal blooms of Anabaena lemmermannii and Gloeotrichia echinulata began to appear in summer. Between 1960 and 1980, the lake developed into a hypertrophic status with extensive blooms of blue-green algae from May to October, including high biomasses of mainly Microcystis spp. This severe pollution started with increased usage of the lake, increased tourism and recreation, intensified farming with the introduction of artificial fertilization, and also the diversion of sewage water from a sewage treatment plant. In 1968, cattle death was reported and in 1981, algal toxicity was verified by mouse bioassay. After a period of extremely poor water quality, the lake began to show signs of improvement as a result of the nutrient and fish reduction programmes. The very heavy blooms of blue-green algae decreased and the duration of blooms became shorter. The Microcystis species were to a certain extent replaced by Anabaena and Aphanizomenon species, and biodiversity of algae increased. With respect to the algal community, the lake has improved considerably, but is still eutrophic and suffers summer blooms of toxic blue-green algae.
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    Respiration and feeding of the surf clam Paphies donacina from New Zealand (1999)
    Springer
    Hydrobiologia 405 (1999), S. 179-188 
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    ISSN: 1573-5117
    Keywords: bivalve ; surf clam ; oxygen uptake ; clearance rate ; temperature ; body size
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Oxygen uptake and feeding (clearance) rates were measured for the tuatua Pahpies donacina from an exposed sand beach characterised by variable levels of productivity (4–12 μg l−1chlorophyll a) and an annual temperature range between 8 and 19 °C. The aims of the study were to assess the ability of the surf clam to regulate feeding activity and oxygen uptake over a range of food concentrations and temperature conditions. Tuatuas, shell length 27–95 mm, were exposed to temperatures of 10, 15 and 20 °C in summer and 5, 10 and 15 °C in winter. Aquatic oxygen uptake depended on both body weight and exposure temperature with body weight explaining the majority of the variation in the multiple-regression equation. Weight specific oxygen uptake was similar at the two upper temperatures and significantly reduced at the lower temperature. For a standard length tuatua the oxygen uptake was similar at 10 °C in both summer and winter. Clearance rates of P. donacina feeding on laboratory cultures of Isochrysis galbana were low compared with other bivalves. They increased logarithmically with cell concentration up to a maximal rate, then declined at higher cell levels. The clearance rate depended upon shell length and dry tissue weight and was higher for tuatua acclimated at 10 °C than at 15 °C. It was concluded that P. donacina shows seasonal adjustment in oxygen uptake and filtration rate to compensate for seasonal temperature variation in the habitat. The 10 °C temperature optima for the clearance rate is consistent with the southern distribution of this species allowing it to feed effectively during periods of high food availability.
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    Effects of genotype and environment on phenotypic variability in Limnocythere inopinata (Crustacea: Ostracoda) (1999)
    Springer
    Hydrobiologia 400 (1999), S. 85-114 
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    ISSN: 1573-5117
    Keywords: morphology ; clone ; temperature ; salinity ; parthenogenesis ; sexual reproduction ; cluster genotype ; general purpose genotype ; clonal taxonomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Limnocythere inopinata (Baird) is a Holarctic species, widely distributed in non-marine waters, and mainly occurring in unisexual populations. It displays polymorphic traits which could be useful for taxonomical and (palaeo)ecological purposes, if the origin of these traits could be better understood. Three clones of L. inopinata were cultured in the laboratory under various temperature and salinity conditions (i.e. temperature 15, 20 and 25 °C, salinity expressed as electrical conductivity 400, 2000, 5000 and 8000 μS cm−1). Morphological traits for both the valves (shape and size) and soft parts (11 limb setae) were observed. Field populations from Chinese salt lakes and from Austrian lakes were also compared. The freshwater population from Mondsee and its derived clone M develop larger valves than those of the other two clones, clone N (from Neusiedlersee) and clone S (from Seewinkel, Oberer Stinkersee), which live exclusively in saline (alkaline) water. Parthenogenetic specimens from the freshwater lake Mondsee and sexually reproducing females from the Chinese salt lakes both have sub-rectangular valves with straight dorsal margin; the saline clones and populations have highly arched valves with rounded dorsal margin. No direct effects of temperature or salinity on valve ornamentation (reticulation, nodation) have been found. At least for nodation, a genetic factor seems apparent, as the saline clones N and S are never nodose, while the freshwater animals from Mondsee and the sexual animals from the Chinese salt lakes can be both with or without nodes. In the former case, number and position of nodes are variable. Both absolute and relative length of limb setae can be affected by environmental factors and by genotype, and this is the first time that this has been demonstrated in non-marine ostracods. Based on the present observations and experiments, it is concluded that L. inopinata is a variable, polymorphic species, consisting of a (semi-) continuous morphological cluster, in which both clonal genotypes and sexual haplotypes are nested. Therefore, Limnocythere sappaensis Staplin and L. binoda Huang are considered synonyms of L. inopinata; L. mongolica Daday is a possible synonym; L. sanctipatricii sensu Huang and L. dubiosa sensu Huang from Lake Qinghai are most likely erroneous identifications. Apparently recognisable clones with typical ecologies cannot be allocated a taxonomic rank, as this does not reflect a phylogenetic reality. Such links between recognisable morphologies and typical ecological ranges are useful for palaeoenvironmental reconstructions, but are applicable at a regional scale only.
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    The N and P budget of the shallow, flushed lake Müggelsee: retention, external and internal load (1999)
    Springer
    Hydrobiologia 408-409 (1999), S. 159-166 
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    ISSN: 1573-5117
    Keywords: shallow lake ; nutrient loading ; retention ; nitrogen ; phosphorus ; release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The shallow (mean depth 4.9 m), polymictic and eutrophic lake Müggelsee was highly loaded with phosphorus (6 gP m-2a-1) and nitrogen (170 gN m-2a-1) by the river Spree up to the end of the 1980s. Annual load declined by 40–50% during the last years (1991–97). Phosphorus retention fluctuated strongly during the seasonal cycle between −200 and +100 kgP d-1and from year to year between −44% and + 26% of the P import. At the end of the eighties, the P retention capacity of the sediment was exceeded and Müggelsee became a source of phosphorus. The lake regained its ability to retain P in the sediments after external load reduction in the 1990s. However, the internal load of P reached the level of the external one. The release of P during summer was strongly related to the import of nitrate. On long-term average (1979–1997), less than 1% of the P input was retained in Müggelsee. About 24% of the nitrogen load were removed in the lake on annual mean. This rate decreased during the last years.
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    Surficial sediment composition as a record of environmental changes in the catchment of shallow Lake Petersdorf, Brandenburg, Germany (1999)
    Springer
    Hydrobiologia 408-409 (1999), S. 185-192 
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    ISSN: 1573-5117
    Keywords: shallow lake ; sediment ; dy ; phosphorus ; calcium ; metals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A chemical characterization of the surficial sediment (0–20 cm) of type `dy' (org-Cpart/TNpart〉10) of the anthropogenically polluted shallow Lake Petersdorf is presented. Eighty samples were analyzed for a set of parameters, i.e. dry weight, loss on ignition (LOI), total inorganic carbon (TIC), N, S, P, Ca, Si, As, Fe, Al, Mn, Zn, Cd, and Pb. LOI, TIC, N, S, Ca, P, and Zn tend to accumulate at a water depth 〉2 m (70.6% of the lake surface) in contrast to Mn and Fe which are more widely distributed, and Cd and Pb which are accumulated in the lake part close to a road. The enrichment factors of certain elements, e.g. Al (23.9%), Si (31.5%), P (12.2%), and Ca (68.7%) from 20 cm sediment depth up to the surface, are attributed to incisive changes in the immediate catchment. Erosion, fertilization, amelioration, and separation of the peatland north of the lake by a dam within the last 60 yrs resulted in the change of Lake Petersdorf from a dystrophic to a eutrophic stage. This enhanced the mineralization of its meso-humic (LOI/TNpart=20.6) sediment.
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    Identification of small-scale structure of plankton communities of the Black and Ionian Seas by their bioluminescence characteristics (1999)
    Springer
    Hydrobiologia 393 (1999), S. 163-167 
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    ISSN: 1573-5117
    Keywords: plankton patches ; bioluminescence ; temperature ; Ionian and Black Seas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Small-scale heterogeneity of bioluminescence intensity was studied in offshore regions of the Black and Ionian Seas in September/October, 1989. Bathyphotometric casts were deployed every 3 min over a period of several hours from a drifting vessel. Casts were accompanied by temperature profiles and zooplankton sampling. Taking into account the vessel drift, the sampling interval was equal to a spatial resolution from 15 to 25 m. Measurements were carried out during the day and night periods. From adaptive spectral analysis it was shown that the horizontal dimensions of the bioluminescent heterogeneities were between 75 and 1500 m in the Black Sea and 89–800 m in the Ionian Sea. The horizontal dimensions of the heterogeneities were 85–818 m and 85–500 m for zooplankton biomass and 80–1800 m and 85–600 m for the temperature field in the Black and Ionian Seas, respectively. Therefore, it is assumed that physical and dynamical factors dominate in the formation of small-scale spatial heterogeneity of the studied fields. Biological factors, such as diel vertical migrations, trophic interactions etc. will also contribute to the formation of patches at night.
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    URL: http://dx.doi.org/10.1023/A:1003548906125
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    Long-term phytoplankton changes in acid and limed lakes in SW Sweden (1999)
    Springer
    Hydrobiologia 394 (1999), S. 93-102 
    Details
    ISSN: 1573-5117
    Keywords: acidification ; phosphorus ; oligotrophication ; cyanophyceans ; desmids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytoplankton development in the acidified Lakes Östra Nedsjön and Ömmern, situated in SW Sweden, was followed during 1973–92. The former lake was first limed in 1971–73 which increased the pH value from ca 5.3 to 6, without affecting the plankton markedly. In Lake Ömmern, acidification lowered the pH value from ca 6 to 5.3 during 1976–1981, which caused oligotrophication and reduced number of species. In 1981/82 both lakes were limed, and during the following period treatments were regularly made, resulting in average pH levels of 7.2 and 6.9, respectively. The concentrations of humic compounds and phosphorus increased and the distribution of the major plankton groups was markedly changed. In both lakes the cyanophycean volume decreased, whereas diatoms became quantitatively important. Especially in relation to the acidic period 1979–81, there was increased species richness in both lakes. However, in contrast to the development in Lake Ömmern, the desmids were eliminated in Lake Ö.Nedsjön, where the pre-acidification phytoplankton was not restored.
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    A reservoir in management-induced transition between ecological states (1999)
    Springer
    Hydrobiologia 395-396 (1999), S. 325-333 
    Details
    ISSN: 1573-5117
    Keywords: reservoir ; phosphorus ; algal blooms ; water treatment ; ferric dosing ; macrophytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The impact of phosphorus control on the nutrient dynamics and biological activity of Foxcote Reservoir, a small impounded reservoir operated by Anglian Water are discussed. Phosphorus precipitation using iron salts was commenced in 1981 to improve the treatability of previously algal-laden water and continued until 1994 when the reservoir was closed as a water supply source. A marked decrease in algal biomass was observed after an initial delay, which coincided with an increase in the abundance of aquatic macrophytes. There were also marked shifts in the macrophyte community during the following 10 years, with an increase in Elodea and an initial increase then decline in Chara. The zooplankton community also changed with an increase in the larger bodied Daphma pulex. No overall change in the rate of denitrification was observed, although patterns of silica depletion showed changes in frequency. Trends in wildfowl counts over this period reflect changes in the ecology of the reservoir.
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    Legislative challenges for lake eutrophication control in Europe (1999)
    Springer
    Hydrobiologia 395-396 (1999), S. 389-401 
    Details
    ISSN: 1573-5117
    Keywords: legislation ; eutrophication ; phosphorus ; nitrogen ; wildlife conservation ; SSSI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract There is no single piece of legislation which comprehensively addresses the problem of eutrophication of freshwater lakes. An examination is made of the extent to which national and EU laws applicable in England and Wales may be used to reduce phosphorus inputs to eutrophicated lakes. This case study is then used to outline the shortcomings of existing legislation and the future challenges for lake eutrophication control. Applicable legislation may be divided into that relating to nature conservation, to water quality and to agricultural extensification. Nature conservation laws are applicable, in that lakes designated as Sites of Special Scientific Interest (SSSIs), are theoretically safeguarded from degradation. The main limitation of the SSSI system lies in the boundary definition process under which, as a rule, no other category of legally protected land may be designated. Thus, the use of surrounding buffer land to protect water quality at the catchment level is generally precluded. The introduction of consultation areas around SSSIs of international importance under the EU Directive on Habitats is unlikely to alleviate the problem, since the area involved remains minimal compared to the extent of the majority of catchments. Intensive agricultural practices are responsible for significant nutrient enrichment of rivers and lakes, so that legislation aimed at extensification is also relevant. Examples of agricultural extensification include the Environrnentally Sensitive Areas programme and various options available for Set-Aside land. However, the prime purpose of such initiatives is the alleviation of surplus and budgetary problems and, as such, they fall short of a fully integrated approach to the ecological management of farmland. Nutrient enrichment is, essentially, a water quality issue, but policy and legislation in this area are not yet sufficiently developed to address the problem comprehensively. The current regulatory process for water quality carries the potential to work comparatively well for point sources under the system of consents to discharge. This potential is limited, however, by the paucity of information available on ecologically acceptable concentrations of phosphorus in discharges. In addition, the consents system is not constructed to deal effectively with diffuse agricultural losses of phosphorus, since, unlike point sources, these tend to arise from the cumulative effect of many activities. The main legislative challenge for lake eutrophication control lies in the area of diffuse agricultural losses of phosphorus. In this respect, experience in the U.S.A. reveals that the use of comprehensive and catchment-wide ‘Best Management Practices’ is capable of producing significant water quality improvements, providing that some degree of mandatory compliance is incorporated.
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    Lake and catchment management in Denmark (1999)
    Springer
    Hydrobiologia 395-396 (1999), S. 419-432 
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    ISSN: 1573-5117
    Keywords: Integrated lake management ; biomanipulation ; lake recovery ; phosphorus ; nitrogen ; eutrophication ; restoration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The majority of Danish lakes are highly eutrophic due to high nutrient input from domestic sources and agricultural activities. Reduced nutrient retention, and more rapid removal, in catchments as a result of agricultural drainage of wetlands and lakes and channelisation or culverting of streams also play a role. Attempts have recently been made to reduce nutrient loading on lakes by intervening at the source level and by improving the retention capacity of catchment areas. The former measures include phosphorus stripping and nitrogen removal at sewage works, increased use of phosphate-free detergents, and regulations concerning animal fertiliser storage capacity, fertiliser application practices, fertilisation plans and green cover in winter. In order to improve nutrient retention capacity of catchments, wetlands and lakes have been re-established and channelised streams have been remeandered. In addition, cultivation-free buffer strips have been established alongside natural streams and there has been a switch to manual weed control. These measures have resulted in a 73% reduction of the mean total phosphorus concentration of point-source polluted streams since 1978; in contrast, there has been no significant change in the total nitrogen concentration. Despite the major reduction in stream phosphorus concentrations, lake water quality has often not improved. This may reflect a too high external or internal phosphorus loading or biological resistance. Various physico-chemical restoration measures have been used, including dredging and oxidation of the hypolimnion with nitrate and oxygen. Biological restoration measures have been employed in 17 Danish lakes. The methods include reducing the abundance of cyprinids, stocking with 0+ pike ( Esox lucius) to control 0+ cyprinids, and promoting macrophyte recolonization by protecting germinal submerged macrophyte beds against grazing waterfowl and transplanting out macrophyte shoots. In several lakes, marked and long-lasting improvements have been obtained. The findings to date indicate that fish manipulation has a long-term effect in shallow lakes, providing nutrient loading is reduced to a level so low as to ensure an equilibrium lake water phosphorus concentration of less than 0.05–0.1 mg phosphorus l−1. If nitrogen loading is very low, however, positive results may be obtained at higher phosphorus concentrations. Macrophyte refuges and transplantation seem to be the most successful as restoration measures in the same nutrient-phosphorus regime as fish manipulation.
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    Experimental effects of temperature and prey assemblage on growth and lipid accumulation by Mysis relicta loven (1999)
    Springer
    Hydrobiologia 412 (1999), S. 155-164 
    Details
    ISSN: 1573-5117
    Keywords: zooplankton ; ecology ; lakes ; Mysis relicta ; food webs ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The opossum shrimp (Mysis relicta) is a holarctic planktivore that undergoes diel vertical migration (DVM), ascending at night from deeper water or the lake bottom into the upper water column to feed. In deep lakes that thermally stratify, M. relicta spends most of the time on or near the lake bottom in cold water where food resources are low; but, M. relicta migrates daily into warmer layers to feed where food resources are more abundant. Hence, in deep lakes M. relicta traverses steep temperature and prey density gradients while migrating through the water column to forage. We conducted a laboratory growth experiment of factorial design that simulated the range of temperatures and densities of natural zooplankton forage encountered by M. relicta during DVM. Somatic growth, measured as change in total length and lipid-free biomass, was not significantly different among experimental treatments. Analysis of variance showed that M. relicta stored energy in the form of lipid instead of using the energy mainly to drive increased somatic growth, but only at the colder temperatures. Lipid storage was 24% (± 4.3 sd) in 4 °C-high forage treatment compared to 6% (± 1.1) at 14 °C-high forage treatment. Energy conversion efficiency (ECE) of M. relicta was highest (21.3% ± 5.8) at 4 °C and lowest (3.3% ± 0.9) at 14 °C, regardless of prey density. The experiment showed that Mysis relicta feeds at high food densities where ECE is low, but spends most of the time in colder water where ECE is high. These results support McLaren's metabolic efficiency hypothesis, which predicts that feeding in the more productive surface waters and then migrating to colder waters is reproductively advantageous. Moreover, owing to high metabolic efficiency in the coldest waters and rapid DVM, M. relicta is able to sequester much of the epilimnetic zooplankton production near or on the lake bottom, thereby forcing the lake food web toward a configuration dominated by mysids, benthic or deepwater fishes and small, agile zooplankton.
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    Impact of ecological factors on the regeneration of mangroves in the Ciénaga Grande de Santa Marta, Colombia (1999)
    Springer
    Hydrobiologia 413 (1999), S. 35-46 
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    ISSN: 1573-5117
    Keywords: mangrove ; regeneration ; reforestation ; salinity ; seedlings ; temperature ; water supply
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the Ciénaga Grande de Santa Marta, a brackish lagoon system on the Caribbean coast of Colombia, human-induced changes in the hydrological system caused hypersalinisation of the soils. As a result, 30 000 ha of originally 51 000 ha of the mangrove forests growing in the lagoon's flood plain died. Presently, efforts are being made to reestablish the original hydrological system. Reforestation of the bare areas is planned with the three dominating mangrove species Avicennia germinans, Laguncularia racemosa and Rhizophora mangle. The objective of the project presented here is to identify the regeneration patterns in the study area. Experiments under controlled conditions and measurements at bare and forested sites carried out from 1994 to 1996 showed that regeneration is possible. However, as the bare areas are large and presently very few or no propagules arrive naturally, regeneration will be slow. Therefore, reforestation is recommended to accelerate the process. In the forests, the seedling growth is mainly controlled by changes in salinity and the mortality by seasonal flooding, while in the bare areas, regeneration is aggravated by extremely high salinities, high soil temperatures and dessication of the top soil layers. The establishment of the small A. germinans and L. racemosa propagules is especially difficult, because they cannot establish themselves in flooded soils and in direct sunlight they dry out rapidly. The seedlings of both species are also very sensitive to changes in water level, wind, waves, temperatures exceeding 45 °C and dry soils. In A. germinans, phytophagous insects affect the chances for survival also. Therefore, mortality in both species is extremely high. R. mangle is much more resistant to most detrimental factors observed with the exception of high salinities. However, there is one favourable factor at the open sites. When sufficient water is present and salinities as well as temperatures are low enough, the high light availability increases growth rates and survival.
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    A theoretical analysis and field evaluation of a light and temperature model of production by Ecklonia cava (1999)
    Springer
    Hydrobiologia 398-399 (1999), S. 361-373 
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    ISSN: 1573-5117
    Keywords: production ; mathematical model ; Ecklonia cava ; light ; temperature ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The dependence of photosynthesis on light and temperature is modelled through analysis of transition probabilities of photosystems. In the model, two transition probabilities are functions of light, and one transition probability is a function of temperature. The estimated light-saturated photosynthesis of Ecklonia cava blades at 20 °C was 0.037 mg C cm−2 h−1. The value of the activation energy, the standard enthalpy and the standard entropy were estimated to be 56.5 kJ mol−1, 204 kJ mol−1 and 678 J mol−1 K−1, respectively. A production model (an integral photosynthesis model) for an E. cava stand was developed using the photosynthesis model. Production calculated by the model agreed well with observed data during the growing period of an E. cava stand at a field observation site on the west side of Miura Peninsula, Japan. Results of the analysis of the effects of irradiance and temperature on the production of the E. cava community by the model are: 1. Production decreased with irradiance decrease. The estimated compensation irradiance was 26.5 μmol photons m−2 s−1 when the biomass was 3 kg wet mass m−2 (blade:stipe ratio = 2 kg m−2:1 kg m−2) and the temperature was 20 °C. 2. The optimum temperature decreased when irradiance decreased and when biomass increased. The highest estimated value for the optimum temperature was 24.0 °C. The estimated optimum temperature was 18.2 °C when the biomass was 12 kg wet mass m−2 and the photon irradiance was 200 μmol photons m−2 s−1. 3. The amount of biomass that resulted in the maximum production was influenced by irradiance and temperature. At 400 μmol photons m−2 s−1 and 20 °C, the estimated value of the biomass (blade:stipe = 2:1) giving the maximum pr oduction was about 5.3 kg wet mass m−2. However, at 100 μmol photons m−2 s−1 and 24 °C, the estimated value was about 3.0 kg wet mass m−2. The estimated values of the maximum production under the two conditions were 1.05 and 0.30 g C m−2 h−1, respectively.
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    Effects of thermal regime on energy and nitrogen budgets of an early juvenile Arctic charr, Salvelinus alpinus, from Lake Inari (1999)
    Springer
    Environmental biology of fishes 54 (1999), S. 219-227 
    Details
    ISSN: 1573-5133
    Keywords: temperature ; energy partitioning ; nitrogen balance ; salmonid ; fish
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The feed intake, growth, oxygen consumption and ammonia excretion of juvenile Arctic charr were measured over period of four weeks at different temperatures which were either constant (11.0, 14.4, 17.7 °C) or fluctuated daily (14.3 ± 1 °C). Maximum feed intake was estimated to occur at 14.3 °C, while oxygen consumption and nitrogen excretion were highest at the highest temperature, and growth rate was estimated to be highest at 13.9 °C. Feed conversion efficiency was estimated to be highest at 13.2 °C, where over 62.7% of ingested energy was allocated to growth. Metabolic rate accounted for 16–30% of ingested energy and nitrogen excretion was under 3% of ingested energy. The nitrogen budget was under similar thermal influences to the energy budget. Thermal fluctuation increased metabolic rate, but not feed intake, leading to a reduction in feed conversion efficiency under fluctuating temperature conditions.
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    URL: http://dx.doi.org/10.1023/A:1007566806749
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    A simulation model of organic matter and nutrient accumulation in mangrove wetland soils (1999)
    Springer
    Biogeochemistry 44 (1999), S. 93-118 
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    ISSN: 1573-515X
    Keywords: Everglades National Park ; mangrove soils ; organic matter ; nitrogen ; phosphorus ; sedimentation ; simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The distribution and accumulation of organic matter, nitrogen (N) and phosphorus (P) in mangrove soils at four sites along the Shark River estuary of south Florida were investigated with empirical measures and a process-based model. The mangrove nutrient model (NUMAN) was developed from the SEMIDEC marsh organic matter model and parameterized with data from mangrove wetlands. The soil characteristics in the four mangrove sites varied greatly in both concentrations and profiles of soil carbon, N and P. Organic matter decreased from 82% in the upstream locations to 30% in the marine sites. Comparisons of simulated and observed results demonstrated that landscape gradients of soil characteristics along the estuary can be adequately modeled by accounting for plant production, litter decomposition and export, and allochthonous input of mineral sediments. Model sensitivity analyses suggest that root production has a more significant effect on soil composition than litter fall. Model simulations showed that the greatest change in organic matter, N, and P occurred from the soil surface to 5 cm depth. The rapid decomposition of labile organic matter was responsible for this decrease in organic matter. Simulated N mineralization rates decreased quickly with depth, which corresponded with the decrease of labile organic matter. The increase in organic matter content and decrease in soil bulk density from mangrove sites at downstream locations compared to those at upstream locations was controlled mainly by variation in allochthonous inputs of mineral matter at the mouth of the estuary, along with gradients in mangrove root production. Research on allochthonouns sediment input and in situ root production of mangroves is limited compared to their significance to understanding nutrient biogeochemistry of these wetlands. More accurate simulations of temporal patterns of nutrient characteristics with depth will depend on including the effects of disturbance such as hurricanes on sediment redistribution and biomass production.
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    Methane emissions from wet grasslands on peat soil in a nature preserve (1999)
    Springer
    Biogeochemistry 44 (1999), S. 205-220 
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    ISSN: 1573-515X
    Keywords: grassland ; ground water level ; methane ; peat ; temperature ; wetland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The area of wet grasslands on peat soil in the Netherlands is slowly increasing at the expense of drained, agriculturally used grasslands. This study aimed (i) to assess the contribution of wet grasslands on peat soil to methane (CH4) emissions, and (ii) to explain differences among sites and between years in order to improve our understanding of controlling factors. For these purposes, a field study was conducted in the period 1994–1996 in the nature preserve “Nieuwkoopse Plassen”, which is a former peat mining and agricultural area. Net CH4 emissions were measured weekly to monthly with vented closed flux chambers at three representative sites, and at ditches near these sites. Three-years average of CH4 emissions was 7.9 g CH4 m- 2 yr-1 for Drie Berken Zudde, 13.3 for Koole, and 20.4 for Brampjesgat. Ditches near the sites emitted 4.2–22.5 g CH4 m-2 yr-1. The time-course of CH4 emissions for all experimental sites and years was fit with a multiple linear regression model with ground water level and soil temperature as independent variables. Lowering or raising the ground water level by 5 cm could decrease or increase CH4 emissions by 30–50%. Therefore, ground water level management of these grasslands should be done with care.
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    Nutrient budgets and biogeochemistry in an experimental agricultural watershed in Southeastern China (1999)
    Springer
    Biogeochemistry 45 (1999), S. 1-19 
    Details
    ISSN: 1573-515X
    Keywords: Chaohu Lake ; chemical fertilizer ; cycling ; denitrification ; multipond system ; nitrogen ; nutrient budget ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract During a two-year field study, an annual nutrient budget and cycles were developed for a small agricultural watershed. The study emphasized the integrated unit of the watershed in understanding the biogeochemistry. It was found that the total nutrient input was 39.1 × 104 kg nitrogen and 3.91 × 104 kg phosphorus in the year 1995, of which the greatest input of nutrients to the watershed was chemical fertilizer application, reaching 34.7 × 104 kg (676 kg/ha) nitrogen and 3.88 × 104 kg (76 kg/ha) phosphorus. The total nutrient output from the watershed was 13.55 × 104 kg nitrogen and 0.40 × 104 kg phosphorus, while the largest output of nitrogen was denitrification, accounting for 44.1% of N output; the largest output of phosphorus was sale of crops, accounting for 99.4% of P output. The results show that the nutrient input is larger than output, demonstrating that there is nutrient surplus within the watershed, a surplus which may become a potential source of nonpoint pollution to area waters. The research showed that both denitrification and volatilization of nitrogen are key ways of nitrogen loss from the watershed. This suggests that careful management of fertilizer application will be important for the sustainable development of agriculture. The research demonstrated that a multipond system within the watershed had high retention rate for both water and nutrients, benefiting the water, nutrient and sediment recycling in the terrestrial ecosystem and helping to reduce agricultural nonpoint pollution at its source. Therefore, this unique watershed system should be recommended due to its great potential relevance for sustainable agricultural development.
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    URL: http://dx.doi.org/10.1023/A:1006073408623
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    The fate of NH4NO3 added toSphagnum magettanicum carpets at five European mire sites (1999)
    Springer
    Biogeochemistry 45 (1999), S. 73-93 
    Details
    ISSN: 1573-515X
    Keywords: atmospheric deposition ; moss ; bog ; nitrogen ; phosphorus ; water table
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Nitrogen additions as NH4NO3 corresponding to 0 (N0), 1 (N1), 3 (N3) and 10 (N10) g N m−2 yr−1 were made toSphagnum magellanicurn cores at two-week intervalsin situ at four sites across Europe, i.e. Lakkasuo (Finland). Männikjärve (Estonia), Moidach More (UK) and Côte de Braveix (France). The same treatments were applied in a glasshouse experiment in Neuchâtel (Switzerland) in which the water table depth was artificially maintained at 7, 17 and 37 cm below the moss surface. In the field, N assimilation in excess of values in wet deposition occurred in the absence of growth, but varied widely between sites, being absent in Lakkasuo (moss N∶P ratio 68) and greatest in Moidach More (N∶P 21). In the glasshouse, growth was reduced by lowering the water table without any apparent effect on N assimilation. Total N content of the moss in field sites increased as the mean depth of water table increased indicating growth limitation leading to increased N concentrations which could reduce the capacity for N retention. Greater contents of NH4 + in the underlying peat at 30 cm depth, both in response to NH4NO3 addition and in the unamended cores confirmed poor retention of inorganic N by the moss at Lakkasuo. Nitrate contents in the profiles at Lakkasuo, Moidach More, and Côte de Braveix were extremely low, even in the N10 treatment, but in Männikjärve, where the mean depth of water table was greatest and retention absent, appreciable amounts of NO3 − were detected in all cores. It is concluded that peatland drainage would reduce the capture of inorganic N in atmospheric deposition bySphagnum mosses.
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    URL: http://dx.doi.org/10.1007/BF00992874
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    The impact of accelerating land-use change on the N-Cycle of tropical aquatic ecosystems: Current conditions and projected changes (1999)
    Springer
    Biogeochemistry 46 (1999), S. 109-148 
    Details
    ISSN: 1573-515X
    Keywords: estuaries ; lakes ; marine ; nitrogen ; phosphorus ; rivers ; streams ; temperate ; tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Published data and analyses from temperate and tropical aquatic systems are used to summarize knowledge about the potential impact of land-use alteration on the nitrogen biogeochemistry of tropical aquatic ecosystems, identify important patterns and recommend key needs for research. The tropical N-cycle is traced from pre-disturbance conditions through the phases of disturbance, highlighting major differences between tropical and temperate systems that might influence development strategies in the tropics. Analyses suggest that tropical freshwaters are more frequently N-limited than temperate zones, while tropical marine systems may show more frequent P limitation. These analyses indicate that disturbances to pristine tropical lands will lead to greatly increased primary production in freshwaters and large changes in tropical freshwater communities. Increased freshwater nutrient flux will also lead to an expansion of the high production, N- and light-limited zones around river deltas, a switch from P- to N-limitation in calcareous marine systems, with large changes in the community composition of fragile mangrove and reef systems. Key information gaps are highlighted, including data on mechanisms of nutrient transport and atmospheric deposition in the tropics, nutrient and material retention capacities of tropical impoundments, and N/P coupling and stoichiometric impacts of nutrient supplies on tropical aquatic communities. The current base of biogeochemical data suggests that alterations in the N-cycle will have greater impacts on tropical aquatic ecosystems than those already observed in the temperate zone.
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    URL: http://dx.doi.org/10.1007/BF01007576
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    The globalization of N deposition: ecosystem consequences in tropical environments (1999)
    Springer
    Biogeochemistry 46 (1999), S. 67-83 
    Details
    ISSN: 1573-515X
    Keywords: acidification ; anthropogenic nitrogen ; cations ; nitrate leaching ; nitric oxide ; nitrous oxide ; nutrient limitation ; phosphorus ; productivity ; tropical ecosystems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Human activities have more than doubled the inputs of nitrogen (N) into terrestrial systems globally. The sources and distribution of anthropogenic N, including N fertilization and N fixed during fossil fuel combustion, are rapidly shifting from the temperate zone to a more global distribution. The consequences of anthropogenic N deposition for ecosystem processes and N losses have been studied primarily in N-limited ecosystems in the temperate zone; there is reason to expect that tropical ecosystems, where plant growth is most often limited by some other resource, will respond differently to increasing deposition. In this paper, we assess the likely direct and indirect effects of increasing anthropogenic N inputs on tropical ecosytem processes. We conclude that anthropogenic inputs of N into tropical forests are unlikely to increase productivity and may even decrease it due to indirect effects on acidity and the availability of phosphorus and cations. We also suggest that the direct effects of anthropogenic N deposition on N cycling processes will lead to increased fluxes at the soil-water and soil-air interfaces, with little or no lag in response time. Finally, we discuss the uncertainties inherent in this analysis, and outline future research that is needed to address those uncertainties.
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    URL: http://dx.doi.org/10.1023/A:1006152112852
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    Ecosystem constraints to symbiotic nitrogen fixers: a simple model and its implications (1999)
    Springer
    Biogeochemistry 46 (1999), S. 179-202 
    Details
    ISSN: 1573-515X
    Keywords: carbon dioxide ; grazing ; nitrogen fixation ; nitrogen limitation ; phosphorus ; shade
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The widespread occurrence of N limitation to net primary production (NPP) and other ecosystem processes, despite the ubiquitous occurrence of N-fixing symbioses, remains a significant puzzle in terrestrial ecology. We describe a simple simulation model for an ecosystem containing a generic nonfixer and a symbiotic N fixer, based on: (1) a higher cost for N acquisition by N fixers than nonfixers; (2) growth of fixers and fixation of N only when low N availability limits the growth of nonfixers, and other resources are available; and (3) losses of fixed N from the system only when the quantity of available N exceeds plant and microbial demands. Despite the disadvantages faced by the N fixer under these conditions, N fixation and loss adjust N availability close to the availability of other resources, and biomass and NPP in this simple model can be substantially but only transiently N limited. We then modify the model by adding: (1) losses of N in forms other than excess available N (e.g., dissolved organic N, trace gases produced by nitrification); and (2) constraints to the growth and activity of N fixers imposed by differential effects of shading, P limitation, and grazing. The combination of these processes is sufficient to describe an open system, with input from both precipitation and N fixation, that is nevertheless strongly N-limited at equilibrium. This model is useful for exploring causes and consequences of constraints to N fixation, and hence of N limitation, and we believe it will also be useful for evaluating how N fixation and limitation interact with elevated CO2 and other components of global enviromental change.
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    A comparison of fractionation methods for forms of phosphorus in soils (1999)
    Springer
    Biogeochemistry 47 (1999), S. 25-38 
    Details
    ISSN: 1573-515X
    Keywords: Hedley fractionation ; phosphorus ; Ruttenberg fractionation ; soil phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract We used l6 soils to compare the Hedley method for soil phosphorus fractionation to an alternative method recently developed by Ruttenberg to differentiate among P fractions in marine sediments. For forms of labile and Fe-bound P in soils, these methods were poorly correlated, with the Hedley fractionation showing a greater ability to discriminate among variations in plant-available P. For Ca-bound P, total organic P, and total P, the methods were well correlated (r2 = 0.93, 0.48, 0.74, respectively), although the sum of P measured in the Ruttenberg extractions is only 45% of the total P recovered by the Hedley fractionation. The Hedley fractionation seems superior when an index of plant-available phosphorus and a separation of organic and inorganic forms is needed, whereas the Ruttenberg method allows a separation of CaCO3-bound P from apatite-P, which is potentially useful in calcareous soils.
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    A comparison of fractionation methods for forms of phosphorus in soils (1999)
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    Biogeochemistry 47 (1999), S. 25-38 
    Details
    ISSN: 1573-515X
    Keywords: Hedley fractionation ; phosphorus ; Ruttenberg fractionation ; soil phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract We used 16 soils to compare the Hedley method for soil phosphorus fractionation to an alternative method recently developed by Ruttenberg to differentiate among P fractions in marine sediments. For forms of labile and Fe-bound P in soils, these methods were poorly correlated, with the Hedley fractionation showing a greater ability to discriminate among variations in plant-available P. For Ca-bound P, total organic P, and total P, the methods were well correlated (r2=0.93, 0.48, 0.74, respectively), although the sum of P measured in the Ruttenberg extractions is only 45% of the total P recovered by the Hedley fractionation. The Hedley fractionation seems superior when an index of plant-available phosphorus and a separation of organic and inorganic forms is needed, whereas the Ruttenberg method allows a separation of CaCO3-bound P from apatite-P, which is potentially useful in calcareous soils.
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    Effects of acclimation temperatures of 7 and 14 °C on the contractility of Atlantic salmon (Salmo salar) intestinal smooth muscle in vitro (1999)
    Springer
    Fish physiology and biochemistry 21 (1999), S. 277-284 
    Details
    ISSN: 1573-5168
    Keywords: temperature ; intestine ; nerve stimulation ; serotonin ; substance P ; acetylcholine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The contractility of intestinal smooth muscle of Atlantic salmon (Salmo salar) acclimatized to temperatures of 7 and 14 °C was compared over a prolonged period of time (9 months) in freshwater. Initial studies were carried out on intestine isolated from Atlantic salmon to estimate optimal conditions for contractility. Subsequent studies were carried out with the neurotransmitter/agonist 5-HT and TS, which activates neuronal elements in the intestine, in a Krebs-Henseleit solution containing HEPES buffer maintained at pH 7.85 and at the temperature of the experimental group (i.e., 7 or 14 °C). There was a significant interaction with time and temperature for the maximal response of 5-HT (p=0.005), effective concentration producing 50% of the maximal response (EC50) to 5-HT (p=0.026) and maximal response to TS (p=0.002), demonstrating that gastrointestinal contractility of Atlantic salmon is altered by both time (month) and temperature. No significant changes were found with the effective frequency producing 50% of the maximal response (EF50) to TS. The potency (EC50 of 5-HT) increase between 7 and 14 °C was statistically significant (p=0.026) but the small differences found with potency were most likely not physiologically significant. A time shift was recognized in the maximal responses to 5-HT, by applying a time variable to equations for the curves of the responses. This demonstrated that the curves are similar for both temperatures but alterations in the time of the maximal response changes was different. Thus, there is a delay in the time (month) changes of gastrointestinal contractility related to acclimation temperature and would be an area for future study.
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    Fatty acid composition of the ingested food only slightly affects physicochemical properties of liver total phospholipids and plasma membranes in cold-adapted freshwater fish (1999)
    Springer
    Fish physiology and biochemistry 20 (1999), S. 1-11 
    Details
    ISSN: 1573-5168
    Keywords: phospholipids ; plasma membranes ; fatty acids ; molecular species ; temperature ; membrane fluidity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The fatty acid content, fatty acid molecular species composition, and fluidity of phospholipid vesicles and plasma membranes of livers of fish feeding on phytoplankton (silver carp, Hypophthalmichtys molitrix), zooplankton, (big head carp, Hypophtalmitrix nobilis), higher plants, (grass carp, Ctenopharyngodon idella), and omnivorous fish, (common carp, Cyprinus carpio), adapted to reduced temperatures, was determined. Levels of long chain polyunsaturated fatty acids (PUFAs) were highest in silver and big head carp and lowest in common carp. Differences in long chain PUFAs were poorly reflected in fluidity, determined either by fluorescence anizotropy of 1,6-diphenyl 1,3,5-hexatriene or rotational correlation time of 16-doxyl- stearic acid, of phospholipid vesicles. Phospholipid vesicles of C. caripo and C. idella proved to be slightly more rigid than of H. molitrix and H. nobilis below ca. 15 °C. These differences were not seen with isolated plasma membranes assessed with 1,6-diphenyl 1,3,5-hexatriene. Using electron spin resonance spectroscopy plasma membranes from H. molitrix proved to be more fluid than those from C. carpio below ca. 15 °C. Phosphatidylethanolamines were abundant in 1-monounsaturated, 2-polyunsaturated (18:1/22:6, 18:1/20:4) species with H. molitrix and H. nobilis more rich in these species than C. carpio and C. idella. It is suggested that differences in fluidities of phospholipid vesicles below 15 °C is due to differences in levels of the above molecular species. In native membranes these differences may be masked by proteins and other membrane components. It is also suggested that it is not the fatty acid composition of the ingested food but the specific response of the fish to temperature that is the most important factor controlling the physicochemical properties of membranes during thermal adaptation.
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    Feed Intake and Growth of Juvenile Silver Trevally at the Southern Limit of Their Distribution (1999)
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    Aquaculture international 7 (1999), S. 357-360 
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    ISSN: 1573-143X
    Keywords: feed intake ; growth ; silver trevally (Pseudocaranx dentex) ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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    URL: http://dx.doi.org/10.1023/A:1009296531292
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    Fate of bacterial pathogens in cattle dung slurry subjected to anaerobic digestion (1999)
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    World journal of microbiology and biotechnology 15 (1999), S. 335-338 
    Details
    ISSN: 1573-0972
    Keywords: Anaerobic digestion ; biogas ; pathogens ; survival ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The survival of certain pathogenic bacteria was studied in anaerobic batch digesters at room temperature (18–25 °C) as well as at 35 °C under laboratory conditions. The survival of Escherichia coli and Salmonella typhi at room temperature was upto 20 days whereas at 35 °C it was only upto 10 days. Shigella dysenteriae was found to be the most sensitive organism which could survive upto 10 days at room temperature and upto 5 days at 35 °C. The longest survival was observed in case of Streptococcus faecalis which could survive upto 35 days at room temperature and 15 days at 35 °C. The survival time of Salmonella typhi increased when the solid contents of the digester were elevated from 9% to 15%.
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    Effect of source and nest size of N fertilizers and temperature on nitrification in a coarse textured, alkaline soil (1999)
    Springer
    Nutrient cycling in agroecosystems 54 (1999), S. 199-207 
    Details
    ISSN: 1573-0867
    Keywords: ammonium chloride ; ammonium sulphate ; nest placement ; nitrification ; temperature ; urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nitrification occurring in an alkaline sandy loam soil fertilized with urea, ammonium sulphate (AS) and ammonium chloride (AC) was studied in the laboratory at 20°C and 40°C for 30 days. Nitrogen fertilizers were applied as nest of sizes 0.2, 0.5, 1.0 and 2.0 g. Unfertilized control and soil mixed with 50 mg N kg-1 were also included as treatments. Nitrification in all the fertilizer treatments decreased markedly with increasing nest size. At 20°C, differences among the three N sources were not significant at 5 days after incubation but marked differences appeared thereafter. All the N was nitrified by 30 days in case of fertilizers mixed into the soil. In nest placement, nitrification ranged from 30.1 to 75.5%, 28.3 to 74.6% and 35.3 to 88.7% for urea, AC and AS, respectively. When equal amounts of fertilizers were placed in a nest, nitrification occurred at a slower rate with urea than with AC and AS. Rates of nitrification were significantly higher at 40°C than at 20°C. At 20 days, nitrification from different nest sizes ranged from 8.4 to 64.9% and from 24.9 to 87.0% at 20°C and 40°C, respectively. The difference in nitrification at two temperatures were more pronounced at higher nest sizes than at smaller nest sizes. While nitrification with the three N sources decreased linearly with increase in N concentration (nest size) in soil at 40°C, it showed a quadratic relationship at 20°C. At equal N concentration, the highest rate of nitrification occurred with urea and the lowest with AC. At the same rate of applied N (50–2000 mg kg-1), AC and AS increased electrical conductivity of soil by 1.3–9 times that of urea. Apparent mineral N recovery of applied N decreased with the increase in nest size.
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    Dependence of the entomopathogenic fungus, Beauveria bassiana, on high humidity for infection of Rhodnius prolixus (1999)
    Springer
    Mycopathologia 146 (1999), S. 33-41 
    Details
    ISSN: 1573-0832
    Keywords: entomopathogenic hyphomycete ; vector control ; Chagas disease ; Beauveria bassiana ; Rhodnius prolixus ; humidity ; temperature ; incubation time ; mortality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The impact of relative humidity (RH) on the infective potential of the isolate Bb INRA 297 of Beauveriabassiana (Bals.) Vuillemin (Deuteromycotina: Hyphomycetes) against first in star nymphs of Rhodnius prolixus Stål. (Hemiptera: Reduviidae) was determined. Fungus-treated insects were exposed to RHs ranged from 75 to 100% at 25 °C. Results clearly showed a threshold of humidity at ca. 96% for high and rapid mortality. After initial exposure to increasing periods of 97% (4, 8, 16, 24, 36 and 48 h) and subsequent transfer to constant lower RHs (43, 53,75 and 86%) at a constant 25 °C, an incubation of at least 48 h at 97% RH was necessary to kill all insects. On changing RHs of 97/75% and different regimes of temperature (15/28 °C,20/25 °C, 25/28 °C,and 25/35 °C), at least 72 h of initial exposure at 97% RH for the 15/28 °C regime, 48 h for the 20°/25°C and25/28 °C regimes and 36 h for25/35 °C were needed to kill all insects over a 6-day incubation time. Delayed exposure to favorable moisture condition (97% RH), significantly affected infection for up to a 3-day delay within the various temperature-humidity regimes tested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007019402490
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  • 92
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    Nutrient cycling and growth in forest ecosystems of south western Australia: Relevance to agricultural landscapes (1999)
    Springer
    Agroforestry systems 45 (1999), S. 215-244 
    Details
    ISSN: 1572-9680
    Keywords: biodiversity ; disturbance ; nitrogen ; phosphorus ; resilience ; resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nutrient and hydrologic cycles in harvested native forests in southern Australia are largely balanced. For example, we have little or no evidence of any decline in nutrient capital or availability in harvested forests. Short-term and small-scale reductions in evapotranspiration due to loss of leaf area after harvesting are adequately balanced at the landscape scale by large areas of regenerating or older-age forest. In contrast, agricultural systems on similar soils are a) dependent on large inputs of fertilisers to maintain growth and b) frequently subject to increasing salinity and waterlogging or other forms of degradation. The large-scale replacement of long-lived communities of perennial and often deep- rooting native species with annual crops or other communities of shallow-rooting species might be better managed within the framework of knowledge developed from studies of native plant communities. However, application of such a mimic concept to systems of low natural productivity is limited when agricultural systems require continued high productivity. Nonetheless, the mimic concept may help in developing sustainable management of agriculture on marginal lands, and contribute to the nutritional resilience of agroecosystems. Relevant characteristics for mimic agroecosystems in south western Australia include: high species diversity, diversity of rooting attributes, utilisation of different forms of nutrients (especially of N and P) in space and time, and the promotion of practices which increase soil organic matter content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006267604313
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  • 93
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    Comparing Quiet Sun and Coronal Hole Regions with CDS/SOHO (1999)
    Springer
    Space science reviews 87 (1999), S. 345-348 
    Details
    ISSN: 1572-9672
    Keywords: coronal hole ; quiet Sun ; density ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Spectra from the Coronal Diagnostic Spectrometer on board SOHO are used to compare density and temperature in coronal hole and quiet Sun regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005166417805
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  • 94
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    Effect of nitrogen and phosphorus addition on phenanthrene biodegradation in four soils (1999)
    Springer
    Biodegradation 10 (1999), S. 43-50 
    Details
    ISSN: 1572-9729
    Keywords: biodegradation ; nitrogen ; nutrients ; phenanthrene ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phenanthrene mineralization rates were found to vary widely among four soils; differences in soil nutrient levels was one hypothesis to explain this variation. To test this hypothesis, phenanthrene mineralization rates were measured in these soils with, and without, added nitrogen and phosphorus. Mineralization rates either remained unchanged or were depressed by the addition of nitrogen and phosphorus. Phenanthrene degradation rates remained unchanged in the soil which had the highest indigenous levels of nitrogen and phosphorus and which showed the largest increase in phosphorus levels after nutrients were added. The soils in which degradation rates were depressed had lower initial phosphorus concentrations and showed much smaller or no measurable increase in phosphorus levels after nutrients were added to the soils. To understand the response of phenanthrene degradation rates to added nitrogen and phosphorus, it may be necessary to consider the bioavailability of added nutrients and nutrient induced changes in microbial metabolism and ecology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008359606545
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  • 95
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    Technique for Measuring Thermophysical Properties of Refractory Metals at Supercritical Temperatures (1999)
    Springer
    International journal of thermophysics 20 (1999), S. 1257-1266 
    Details
    ISSN: 1572-9567
    Keywords: critical point ; exploding wire technique ; high-pressure cell ; numerical modeling ; specific heat ; tantalum ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A foil confined in a sapphire cell is heated by an electrical current pulse at rates from 1010 to 1011 K·s−1. Temporal evolutions of the temperature and pressure distributions in the foil is investigated by means of numerical modeling. It is demonstrated that such a technique allows reaching temperatures far above 10,000 K and pressures up to 50 kbar and provides a uniform temperature and pressure in the foil. The technique has been applied for investigation of liquid tantalum. Experimental results on temperature measurement are discussed. Data on specific heat of liquid tantalum at temperatures up to 11,000 K are reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022631626431
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  • 96
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    Does water and phosphorus uptake limit leaf growth of Rhizoctonia-infected wheat seedlings? (1999)
    Springer
    Plant and soil 209 (1999), S. 157-166 
    Details
    ISSN: 1573-5036
    Keywords: hydraulic conductivity ; leaf growth ; phosphorus ; Rhizoctonia ; water status ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Wheat seedlings infected with a pure inoculum of the root-rotting fungus Rhizoctonia solani were grown in pots designed to fit in pressure chambers, to allow the effects of the Rhizoctonia infection on leaf growth to be studied while maintaining the leaves at elevated water status. Wheat was grown to the third leaf stage in soil inoculated with three different levels of Rhizoctonia, and the pots were then pressurised for seven days to maintain the leaf xylem at the point of bleeding (ie. the leaves were at full turgor). The reduction in leaf expansion caused by Rhizoctonia was not overcome by pressurisation, indicating that a reduced supply of water to the leaves was not responsible for reduced leaf growth. The addition of phosphorus to pots marginally deficient in P did not increase the leaf growth of Rhizoctonia-infected plants, despite increased P uptake to the leaves. These results indicate that a reduced supply of water to the leaves and a supply of phosphorus that was bordering on deficient was not the cause of the growth reduction in seedlings with Rhizoctonia infection. The nature of this reduced growth remains uncertain but may involve growth regulators produced by the fungus, or by the plant as a result of the infection process. The mechanism of these growth reductions is of interest as it may provide a key to the development of plant resistance mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004374516088
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  • 97
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    Synthesis of theoretical and empirical experiences from nutrient and cyprinid reductions in Lake Ringsjön (1999)
    Springer
    Hydrobiologia 404 (1999), S. 145-156 
    Details
    ISSN: 1573-5117
    Keywords: biomanipulation ; nutrient reduction ; zooplankton ; phytoplankton ; bottom-up ; top-down ; phosphorus ; submerged vegetation ; benthic macrofauna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The reduction in external phosphorus load to Lake Ringsjön during the 1980s, did not result in improved water transparency during the following ten-year period. Furthermore, a fish-kill in the Eastern Basin of the lake, in addition to a cyprinid reduction programme (biomanipulation; 1988–1992), in contrast to theory, did not lead to any increase in zooplankton biomass or size. This absence of response in the pelagic food chain may have been attributed to the increase in abundance of YOY (0+) fish, following the fish reduction programme. Despite the lack of effect on zooplankton, there was a decrease in phytoplankton biomass, a change in species composition and an increase in water transparency following biomanipulation. In 1989, one year after the fish-kill in Eastern Basin, the Secchi depth (summer mean) increased from 60 cm to 110 cm. In the following years, water transparency increased further, despite an increase in phosphorus loading. An unexpected effect of the biomanipulation was an increase in benthic invertebrate and staging waterfowl abundances, which occurred 2–4 years after fish reduction. Hence, the response in the benthic community following biomanipulation was considerably stronger than in the pelagic community. A likely explanation is that reduction in abundance of the benthic feeding fish species bream (Abramis brama), strongly affected the benthic invertebrate fauna. In this paper, we present what we believe happened in Lake Ringsjön, and which processes are likely to have been important at various stages of the restoration process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003788900521
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  • 98
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    Factors affecting food consumption and growth of walleye, Stizostedion vitreum, larvae in culture ponds (1999)
    Springer
    Hydrobiologia 400 (1999), S. 129-140 
    Details
    ISSN: 1573-5117
    Keywords: fish ; energetics ; temperature ; feeding ; prey abundance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract I examined food consumption and growth of walleye larvae in extensive culture ponds using direct methods and a bioenergetics model, and compared my results with laboratory feeding and growth studies. Walleye showed a diel pattern of increasing gut fullness during daylight hours. Larvae exhibited lower maximum food consumption rates in the ponds than predicted from previous short-term laboratory feeding studies. Direct estimates and bioenergetics model estimates of daily food consumption in the culture ponds were in poor agreement and the discrepancy varied with respect to walleye size. Food consumption rates in the ponds were related to walleye size (direct estimates) or water temperature (bioenergetics model estimates) but not zooplankton abundance. Growth exceeded 0.10 g g−1 d−1 for all but one sampling interval and the maximum growth rate in the culture pond fish was double the maximum growth rate determined in the laboratory. Growth was positively related to pond temperature and negatively related to walleye mass, but was not significantly related to zooplankton abundance. Gross conversion efficiency was negatively related to walleye mass, positively related to zooplankton abundance and not related to temperature. Food consumption and growth of walleye larvae in the field may be food-limited at much lower prey abundances than previous laboratory research has suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003755115000
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  • 99
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    Retention of nutrients in river systems: dependence on specific runoff and hydraulic load (1999)
    Springer
    Hydrobiologia 410 (1999), S. 111-122 
    Details
    ISSN: 1573-5117
    Keywords: phosphorus ; nitrogen ; retention ; river systems ; specific runoff ; hydraulic load
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The total nutrient inputs (emissions) from point and diffuse sources into 100 different river basins in Europe are compared with the measured load (transport). The catchment areas range between 121 and 194 000 km2. Other characteristic parameters of the basins, including specific runoff, surface water area and the nutrient concentration show large differences. Independent of the different methods applied for estimating nutrient emissions, these are in general higher than the actual transport. The ratio of the transport to the emission was used to exclude the effects of basin size and to facilitate comparisons between river basins. A statistical model of the retention, including net sedimentation and denitrification, is derived for the description of the discrepancy between the measured transport and the estimated total emission of nutrients, which is assumed to reflect retention of nutrients in a river system. It was found that the load-weighted retention of phosphorus is controlled practically only by the specific runoff of the basin. The load- weighted retention of nitrogen is further dependent on the proportion of the basin area occupied by surface water, the basin size itself and the mean annual nitrogen concentration at a specific monitoring station. Application of the statistical model reduces the mean deviation between the calculated emissions and the values given by different authors from about 40% to 20%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003735225869
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  • 100
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    The fate of NH4NO3 added to Sphagnum magellanicum carpets at five European mire sites (1999)
    Springer
    Biogeochemistry 45 (1999), S. 73-93 
    Details
    ISSN: 1573-515X
    Keywords: atmospheric deposition ; moss ; bog ; nitrogen ; phosphorus ; water table
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Nitrogen additions as NH4NO3 corresponding to 0 (N0), 1 (N1), 3 (N3) and 10 (N10) g N m-2 yr-1 were made to Sphagnum magellanicum cores at two-week intervals in situ at four sites across Europe, i.e. Lakkasuo (Finland), Männikjärve (Estonia), Moidach More (UK) and Côte de Braveix (France). The same treatments were applied in a glasshouse experiment in Neuchâtel (Switzerland) in which the water table depth was artificially maintained at 7, 17 and 37 cm below the moss surface. In the field, N assimilation in excess of values in wet deposition occurred in the absence of growth, but varied widely between sites, being absent in Lakkasuo (moss N:P ratio 68) and greatest in Moidach More (N:P 21). In the glasshouse, growth was reduced by lowering the water table without any apparent effect on N assimilation. Total N content of the moss in field sites increased as the mean depth of water table increased indicating growth limitation leading to increased N concentrations which could reduce the capacity for N retention. Greater contents of NH4+ in the underlying peat at 30 cm depth, both in response to NH4NO3 addition and in the unamended cores confirmed poor retention of inorganic N by the moss at Lakkasuo. Nitrate contents in the profiles at Lakkasuo, Moidach More, and Côte de Braveix were extremely low, even in the N10 treatment, but in Männikjärve, where the mean depth of water table was greatest and retention absent, appreciable amounts of NO3- were detected in all cores. It is concluded that peatland drainage would reduce the capture of inorganic N in atmospheric deposition by Sphagnum mosses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006133828518
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