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961.
Differential acidity tolerance of tropical legumes grown for green manure in acid sulfate soils 总被引:1,自引:0,他引:1
The growth of four tropical legumes (Cajanus cajan, Sesbania aculeata, S. rostrata, and S. speciosa) used as green manures in the tropics was studied in a glasshouse experiment. Two acid sulfate soils (Typic Sulfaquept, Bang Pakong Series; and Sulfic Tropaquept, Rangsit Series) were adjusted to four pH levels: 3.8 or 4.0 (original soil pH), 4.5, 5.5, and 6.5 (amended with lime). Dry weight was determined 49 days after sowing. Concentrations of N, P, K, Ca, Mg, Fe, Mn, and Al were also determined in aerial plant parts at harvest.The legumes responded differently to soil acidity and liming, but not to soil type. Cajanus cajan had the highest biomass production, followed by S. aculeata, S. rostrata and S. speciosa, in this order. The N concentration closely paralleled biomass production, suggesting that the growth of symbiotic rhizobia and nodulation were perhaps more susceptible to soil acidity than were the host plants. Liming to pH 5.5–6.0 was recommended for the legumes' growth based on the quadratic relationships between dry-matter yield and soil pH. In the unlimed soils, the Ca concentration in C. cajan and S. aculeata (0.32%) was twice as high as that in the two low-yielding legumes (0.15%). Furthermore, plant Ca increased exponentially (or quadratically in case of S. speciosa) as lime additions increased. It was estimated that for adequate growth, the Ca requirement in the shoot dry matter was approximately: C. cajan 1.2% Ca, S. aculeata 0.8%, S. rostrata 0.6%, and S. speciosa 0.4%. In contrast with Ca, the concentration of Fe, and to a lesser extent Mn, was significantly lower in C. cajan and S. aculeata than in S. rostrata and S. speciosa. The ratio of Ca to Al in plant tops was used to characterize plant tolerance to soil acidity, and to quantify the critical Al concentration in the plants. It appears that 90% maximum growth was attained only when Ca/Al was 150 for C. cajan and S. speciosa, 200 for S. rostrata, and 300 for S. aculeata. Cajanus cajan tolerated up to 80 mg Al kg-1 in the shoot dry matter, whereas significant growth reduction occurred in the Sesbania species at levels > 30 mg Al kg-1. 相似文献
962.
Jens Erik Lyngby Sverre M. Mortensen 《Journal of Aquatic Ecosystem Stress and Recovery (Formerly Journal of Aquatic Ecosystem Health)》1994,3(1):27-34
Discs of the macroalga,Ulva lactuca L., were transplanted around an ocean outfall and at a reference site in Køge Bay, Denmark, to assess the influence of the outfall on the nutrient availability. At 2-wk intervals, samples were collected and analyzed for growth, nitrogen, and phosphorus content.The tissue concentrations of nitrogen and phosphorus decreased with distance to the outfall, showing that the tissue concentrations are suitable for monitoring nutrient availability in coastal areas and provide a time-integrated measure of the nutrient availability. The lowest tissue concentrations of nitrogen were recorded at the reference station, where the internal concentrations generally were below the critical concentration level, showing that nitrogen limited the growth. At the station located close to the outfall, the flux of nitrogen was sufficient to maintain the maximum growth rate. The tissue concentrations of phosphorus were only below the critical concentration level on one occasion, and the result showed a net uptake throughout the study period.It was concluded that in the Køge Bay, nitrogen was the main limiting factor for macroalgae growth during the summer. The applicability of tissue concentrations for assessment of nutrient availability is discussed and it is considered that the method, when evaluated against established critical concentrations, provides a valuable tool for assessing ecosystem health with regard to eutrophication. 相似文献
963.
Millward HR Bellhouse BJ Nicholson AM Beeton S Jenkins N Knowles CJ 《Biotechnology and bioengineering》1994,43(9):899-906
The experimental study has assessed a novel membrane bioreactor for mammalian cell culture. In the absence of a gas phase, the key features of cell damage associated with laminar and turbulent flow have been identified. The bioreactor employs a dimpled membrane in order to enhance transverse mixing in a narrow channel, but a fall in viable cell density has been observed at Reynolds numbers above Re = 83. In the laminar flow regime wall shear is the critical mechanism and an accurate calculation of shear rate in a complex channel has been achieved using the Reynolds analogy. Flow generating a wall shear rate in excess of 3000 s(-1) has been shown to cause damage. Power dissipation measurements have been used to distinguish between laminar and turbulent flow and also to predict Kolmogorov eddy lengths. An additional turbulent bulk stress damage mechanism at higher Reynolds numbers (Re > 250) results in a very rapid fall in viable cell density. 相似文献
964.
Mary Ellen Druyan Dean Bass Richard Puchyr Karen Urek David Quig Emmett Harmon William Marquardt 《Biological trace element research》1998,62(3):183-197
Expected values, reference ranges, or reference limits are necessary to enable clinicians to apply analytical chemical data
in the delivery of health care. Determination of references ranges is not straightforward in terms of either selecting a reference
population or performing statistical analysis. In light of logistical, scientific, and economic obstacles, it is understandable
that clinical laboratories often combine approaches in developing health associated reference values. A laboratory may choose
to:
Effects of external contamination and anecdotal information from clinicians may be considered.
The clinical utility of hair analysis is well accepted for some elements. For others, it remains in the realm of clinical
investigation. This article elucidates an approach for establishment of reference ranges for elements in human scalp hair.
Observed levels of analytes from hair specimens from both our laboratory’s total patient population and from a physician-defined
healthy American population have been evaluated. Examination of levels of elements often associated with toxicity serves to
exemplify the process of determining reference ranges in hair. In addition the approach serves as a model for setting reference
ranges for analytes in a variety of matrices. 相似文献
1. | Validate either reference ranges of other laboratories or published data from clinical research or both, through comparison of patients test data. |
2. | Base the laboratory’s reference values on statistical analysis of results from specimens assayed by the clinical reference laboratory itself. |
3. | Adopt standards or recommendations of regulatory agencies and governmental bodies. |
4. | Initiate population studies to validate transferred reference ranges or to determine them anew. |
965.
Predicting the Effects of Atmospheric Nitrogen Deposition in Conifer Stands: Evidence from the NITREX Ecosystem-Scale Experiments 总被引:21,自引:2,他引:19
B. A. Emmett D. Boxman M. Bredemeier P. Gundersen O. J. Kjønaas F. Moldan P. Schleppi A. Tietema R. F. Wright 《Ecosystems》1998,1(4):352-360
The NITREX project, which encompasses seven ecosystem-scale experiments in coniferous forests at the plot or catchment level
in northwestern Europe, investigates the effect of atmospheric nitrogen (N) deposition in coniferous forests. The common factor
in all of the experiments is the experimentally controlled change in N input over a period of 4–5 years. Results indicate
that the status and dynamics of the forest floor are key components in determining the response of forests to altered N inputs.
An empirical relationship between the carbon–nitrogen (C/N) ratio of the forest floor and retention of incoming N provides
a simply measured tool through which the likely timing and consequences of changes in atmospheric N deposition for fresh waters
may be predicted. In the terrestrial ecosystem, a 50% increase in tree growth is observed following the experimental reduction
of N and sulfur inputs in a highly N-saturated site, illustrating the damaging effects of acidifying pollutants to tree health
in some locations. Few biotic responses to the experimental treatments were observed in other NITREX sites, but the rapid
response of water quality to changes in N deposition, and the link to acidification in sensitive areas, highlight the need
for N-emission controls, irrespective of the long-term effects on tree health. The observed changes in ecosystem function
in response to the experimental treatments have been considered within the framework of the current critical-load approach
and thus contribute to the formulation of environmental policy. 相似文献
966.
一个有相互干扰的食植系统的研究 总被引:1,自引:0,他引:1
本文运用常微分方程定性理论讨论了一个放牧有相互干扰的食植系统,获得了该系统极限环存在唯一性及全局渐近稳定性的充分条件. 相似文献
967.
J. M. Elliott 《Journal of fish biology》1989,35(SA):91-98
An example of density-dependent regulation is provided by a long-term investigation (1966-present) of a population of migratory trout (estuarine and sea trout), Salmo trutta L., in a Lake District stream. Evidence for the concept of a critical period for the survival of young fish is briefly reviewed and found to be rather equivocal. The concept is, however, relevant to the trout population. Loss rates were high before but low after a critical survival time ( tc days after fry emergence) that varied between year-classes (range 33-70 days) and was inversely density-dependent on egg density. Survivor density and loss rates were strongly density-dependent on egg density before t c , but proportionate survival with stable loss-rates occurred after t c . Some trout established feeding territories soon after emergence and the number of fish without territories decreased from a high initial value to a negligible value at t c . Fish size at tc was not constant but increased as t c increased. The range of t c for the different year-classes was similar to that for survival times of unfed fry in the laboratory. A new stock-recruitment model, incorporating t c , has been developed for the trout population and shown to be related to the model (Ricker curve) used in the long-term study. The critical time can also be regarded as the critical age for survival in young trout; this concept may be relevant to other fish species. 相似文献
968.
969.
Ocean warming has a greater effect than acidification on the early life history development and swimming performance of a large circumglobal pelagic fish
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Sue‐Ann Watson Bridie J. M. Allan David E. McQueen Simon Nicol Darren M. Parsons Stephen M. J. Pether Stephen Pope Alvin N. Setiawan Neville Smith Carly Wilson Philip L. Munday 《Global Change Biology》2018,24(9):4368-4385
Ocean warming and acidification are serious threats to marine life; however, their individual and combined effects on large pelagic and predatory fishes are poorly understood. We determined the effects of projected future temperature and carbon dioxide (CO2) levels on survival, growth, morphological development and swimming performance on the early life stages of a large circumglobal pelagic fish, the yellowtail kingfish Seriola lalandi. Eggs, larvae and juveniles were reared in cross‐factored treatments of temperature (21 and 25°C) and pCO2 (500 and 985 μatm) from fertilisation to 25 days post hatching (dph). Temperature had the greatest effect on survival, growth and development. Survivorship was lower, but growth and morphological development were faster at 25°C, with surviving fish larger and more developed at 1, 11 and 21 dph. Elevated pCO2 affected size at 1 dph, but not at 11 or 21 dph, and did not affect survival or morphological development. Elevated temperature and pCO2 had opposing effects on swimming performance at 21 dph. Critical swimming speed (Ucrit) was increased by elevated temperature but reduced by elevated pCO2. Additionally, elevated temperature increased the proportion of individuals that responded to a startle stimulus, reduced latency to respond and increased maximum escape speed, potentially due to the more advanced developmental stage of juveniles at 25°C. By contrast, elevated pCO2 reduced the distance moved and average speed in response to a startle stimulus. Our results show that higher temperature is likely to be the primary driver of global change impacts on kingfish early life history; however, elevated pCO2 could affect critical aspects of swimming performance in this pelagic species. Our findings will help parameterise and structure fisheries population dynamics models and improve projections of impacts to large pelagic fishes under climate change scenarios to better inform adaptation and mitigation responses. 相似文献
970.