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  • 1
    Electronic Resource
    Electronic Resource
    Germinable soil seed banks in a tropical savanna: seasonal dynamics and effects of fire. (2005)
    Oxford, UK : Blackwell Science Pty
    Austral ecology 30 (2005), S. 0 
    Details
    ISSN: 1442-9993
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract  The germinable soil seed bank of a tropical eucalypt savanna of north-eastern Australia was found to be dominated by grasses and forbs, with seed bank density ranging from 58 to 792 seeds per square metre, from a total of 53 species. Late dry season fires and the fire-related cues, heat shock and smoke, broke the seed dormancy of a range of tropical savanna species. Heat shock promoted the germination of the species groups natives, exotics, subshrubs, ephemeral and twining perennial forbs, and the common species Indigofera hirsuta, Pycnospora lutescens and Triumfetta rhomboidea. Exposure to smoke at ambient temperature promoted germination from the soil seed bank of the species groups combined natives, upright perennial forbs and grasses, as well as the common grasses Digitaria breviglumis and Heteropogon triticeus. The germinable soil seed bank varied seasonally, increasing from the mid wet season (February) and early dry season (May) to a maximum in the late dry season (October). The effect of recent fire history on soil seed bank dynamics was limited to the immediate release of some seed from dormancy; a reduction in seed densities of subshrubs and monocots, other than grasses, in recently burnt savanna; and enhanced seed density of the ephemeral I. hirsuta in the year following fire. The seed banks of most savanna species were replenished in the year following burning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1442-9993.2004.01426.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of fire regime on plant abundance in a tropical eucalypt savanna of north-eastern Australia (2003)
    Oxford, UK : Blackwell Science Pty
    Austral ecology 28 (2003), S. 0 
    Details
    ISSN: 1442-9993
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract  Changes in plant abundance within a eucalypt savanna of north-eastern Australia were studied using a manipulative fire experiment. Three fire regimes were compared between 1997 and 2001: (i) control, savanna burnt in the mid-dry season (July) 1997 only; (ii) early burnt, savanna burnt in the mid-dry season 1997 and early dry season (May) 1999; and (iii) late burnt, savanna burnt in the mid-dry season 1997 and late dry season (October) 1999. Five annual surveys of permanent plots detected stability in the abundance of most species, irrespective of fire regime. However, a significant increase in the abundance of several subshrubs, ephemeral and twining perennial forbs, and grasses occurred in the first year after fire, particularly after late dry season fires. The abundance of these species declined toward prefire levels in the second year after fire. The dominant grass Heteropogon triticeus significantly declined in abundance with fire intervals of 4 years. The density of trees (〉2 m tall) significantly increased in the absence of fire for 4 years, because of the growth of saplings; and the basal area of the dominant tree Corymbia clarksoniana significantly increased over the 5-year study, irrespective of fire regime. Conservation management of these savannas will need to balance the role of regular fires in maintaining the diversity of herbaceous species with the requirement of fire intervals of at least 4-years for allowing the growth of saplings 〉2 m in height. Whereas late dry season fires may cause some tree mortality, the use of occasional late fires may help maintain sustainable populations of many grasses and forbs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1442-9993.2003.01292.x
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  • 3
    Electronic Resource
    Electronic Resource
    Fire-related cues break seed dormancy of six legumes of tropical eucalypt savannas in north-eastern Australia (2003)
    Oxford, UK : Blackwell Science Pty
    Austral ecology 28 (2003), S. 0 
    Details
    ISSN: 1442-9993
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract This paper describes an assessment of the effect of exposure to fire-related cues (heat shock, smoke and nitrate) and the interactions between the cues on seed dormancy release of tropical savanna legumes in north-eastern Australia. Ten legume species were tested, comprising both native and exotic species. The ten species responded variously to the treatments. Brief exposure to temperatures between 80 and 100°C was found to break the seed dormancy of the native ephemeral herbs Chamaecrista mimosoides, Crotalaria calycina, Crotalaria montana, Indigofera hirsuta and Tephrosia juncea, as well as the exotic ephemeral herb Crotalaria lanceolata. Exposure to 80°C combined with treatment with a nitrate solution produced an additive effect on the germination of Chamaecrista mimosoides and Crotalaria lanceolata. However, the four species with the heaviest seeds, two exotic ephemeral herbs (Chamaecrista absus and Crotalaria pallida) and two native perennials (Galactia tenuiflora and Glycine tomentella) displayed no significant increase in germination with exposure to fire-related cues. Exposure to 120°C for 5 min produced seed mortality in all species tested. Two of the largest seeded species, Crotalaria pallida and Galactia tenuiflora, displayed the lowest tolerance to heat shock, with seed mortality after exposure to 100°C for 5 min. These data indicate that fire can promote the germination of some tropical savanna legumes. As a proportion of seeds of each species displayed no innate dormancy, some germination may occur in the absence of fire, especially of exotic species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1442-9993.2003.01307.x
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of season of burning and removal of herbaceous cover on seedling emergence in a eucalypt savanna of north-eastern Australia (2005)
    Melbourne, Australia : Blackwell Science Pty
    Austral ecology 30 (2005), S. 0 
    Details
    ISSN: 1442-9993
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract  Seedling emergence in a eucalypt savanna of north-eastern Australia was documented over a 12-month period, between May 1999 and May 2000. Seedling emergence for grasses, forbs and subshrubs was found to mainly occur in a brief pulse at the start of the wet season following fire or the removal of grass biomass. Only a minor number of tree and shrub seedlings were detected overall. Burning, or cutting away the grass layer in unburnt savanna, in both the early (i.e. May) and the late (i.e. October) dry seasons significantly increased seedling emergence over undisturbed savanna that had been unburnt for 3 years. Removing the grass layer in unburnt savanna, during either the early or the late dry season, triggered similar seedling densities to savanna burnt in the early dry season. Late dry season fires promoted the greatest seedling density. We attribute this to the higher intensity, late dry season fires releasing a greater proportion of seed from dormancy, coupled with the higher density of soil seed reserves present in the late dry season.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1442-9993.2005.01484.x
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  • 5
    Electronic Resource
    Electronic Resource
    Soil temperature and depth of legume germination during early and late dry season fires in a tropical eucalypt savanna of north-eastern Australia (2004)
    Oxford, UK : Blackwell Science Pty
    Austral ecology 29 (2004), S. 0 
    Details
    ISSN: 1442-9993
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract  Temperatures that significantly increase seed germination of some tropical legumes (i.e. 80–100°C) were documented in the topsoil during the passage of early (May) and late (October) dry season fires in a tropical eucalypt savanna of north-eastern Australia. Elevated temperatures penetrated at least 30 mm into the soil during the higher-intensity, late dry season fires, but were only detected at 10 mm during the early dry season fires. The depth from which germination of two native legume forbs Galactia tenuiflora and Indigofera hirsuta occurred was positively related to the temperature elevation in the topsoil and was greater after late compared with early dry season fires. A broader range in germination depth, resulting in higher seedling densities, was recorded for I hirsuta after late dry season fires. These results suggest that seedling emergence of native leguminous forbs is likely to occur at a greater density after late rather than early dry season fires in tropical eucalypt savannas of north-eastern Australia. Therefore, the season of burning, as a result of its relationship to fire intensity, can influence species composition through its effect on seed germination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1442-9993.2004.01343.x
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  • 6
    Electronic Resource
    Electronic Resource
    An improved, totally automated antibiotic bioassay machine (1969)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 11 (1969), S. 1011-1025 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A number of improvements have been made in a totally-automated antibiotic bioassay machine previously described. The new machine accepts unmeasured, untreated, opaque suspensions of fermentation beers three times faster (120 samples per hour) and supplies printed potencies sooner (in just over two hours). Whereas the original machine employed a self-cleaning filter and used disposable two milliliter beakers, this version involves a batch-dialysis scheme for effecting sample purification, and provides for automated cleaning of incubation chambers.In operation, a measured, portion of thoroughly-mixed fermentation beer is automatically diluted and transferred into one side of an incubation chamber, the two halves of which are separated by a dialysis membrane. The other half is filled with inoculated media. During the two hour incubation at 37°, dialyzable antibiotic limits growth of the inoculum in proportion to its concentration. After incubation, the turbidity of the inoculum is simultaneously read by an online computer and plotted on a strip chart recorded. The computer suplies printed potency values and sample identification on site, while the recording provides the operator with an analog record of turbidity. Fiber optics are employed in the turbidmetric readout, and an electric typewrite provides the printout.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260110522
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