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  • 1
    Electronic Resource
    Electronic Resource
    Lifetimes of local and hyperspherical vibrational resonances of ABA molecules (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 2626-2638 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The complete spectrum of vibrationally excited ABA* molecular resonance lifetimes is evaluated using the simple Rosen–Thiele–Wilson model of coupled Morse oscillators. Two complementary methods are used: First, unimolecular dissociative resonance wave functions are propagated in time by the Fourier method, where the initial wave functions are obtained as an approximation by linear combinations of symmetry-adapted products of Morse functions. Second, bimolecular reaction S matrices are propagated along the hyperspherical radius of the system giving the diagonalized lifetime matrix, which is analyzed for resonance lifetimes and energies. The resulting uni- and bimolecular resonance energies agree within ±0.002 eV and the lifetimes within ±30%. Uni- and bimolecular assignments of gerade (+) and ungerade (−) ABA* symmetries agree perfectly. On the average, the unimolecular decay times decrease as the resonance energies increase from the ABA*→A+BA to about 3/4 of the A+B+A dissociation threshold; even more highly excited resonances tend to be slightly more stabilized. Superimposed on this overall nonmonotonous energy dependence is a strong, 1–2 orders of magnitude variation of lifetimes, indicating substantial mode selectivity for the decay of individual resonances, irrespective of the excitation energy. The mode selectivity is investigated for hyperspherical mode resonances with lobes extending across the potential valleys, in contrast with local mode resonances with frontier lobes pointing towards the valleys. On the average, hyperspherical mode resonances decay at a slower rate than local mode resonances. This conclusion agrees with our previous analysis of low energy ABA* resonances, and with Hose and Taylor's analysis of the Hénon–Heiles system. However, these correlations are also violated by several important exceptions: the ABA* system has many slowly, but also a few rapidly, decaying hyperspherical resonances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452754
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  • 2
    Electronic Resource
    Electronic Resource
    Altitudinal variation in stomatal conductance, nitrogen content and leaf anatomy in different plant life forms in New Zealand (1986)
    Springer
    Oecologia 69 (1986), S. 577-588 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This study is part of a series of investigations on the influence of altitude on structure and function of plant leaves. Unlike most other mountain areas, the Southern Alps of New Zealand provide localities where physiologically effective moisture stress occurs neither at high nor at low elevation, but the changes in temperature and radiation with elevation are similar or even steeper than in most other regions. In comparison with results from other mountains, where moisture may impair plant functioning at low elevation, this study allows an estimation of the relative role of water for the expression of various leaf features typically associated with alpine plants. Maximum leaf diffusive conductance (g), leaf nitrogen content (LN), stomatal density (n) and distribution, as well as area (A), thickness (d) and specific area (SLA) of leaves were studied. Three different plant life forms were investigated over their full altitudinal range (m): trees, represented by Nothofagus menziesii (1,200 m), ericaceous dwarf shrubs (1,700 m), and herbaceous plants of the genus Ranunculus (2,500 m). In all three life forms g, LN, and n increased, while SLA and A decreased with elevation. Recent investigations have found similar trends in other mountains from the temperate zone, but the changes are larger in New Zealand than elsewhere. Herbs show the greatest differences, followed by shrubs and then trees. It is concluded that g is dependent upon light climate rather than water supply, whereas SLA and related structural features appear to be controlled by the temperature regime, as they show similar altitudinal changes under different light and moisture gradients. The higher leaf nitrogen content found at high elevations in all three life forms, suggests that metabolic activity of mature leaves is not restricted by low nitrogen supply at high altitude. In general, the leaves of herbaceous plants show more pronounced structural and functional changes with altitude than the leaves of shrubs and trees.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00410366
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  • 3
    Electronic Resource
    Electronic Resource
    Seasonal control over allocation to reproduction in a tussock-forming and a rhizomatous species of Eriophorum in central Alaska (1989)
    Springer
    Oecologia 78 (1989), S. 27-34 
    Details
    ISSN: 1432-1939
    Keywords: Eriophorum vaginatum ; E. scheuchzeri ; Growth ; Flowering ; Phenology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The evergreen tussock-forming Eriophorum vaginatum revealed consistently earlier (c. 1 moth) phenology and greater biomass per tiller than the summergreen rhizomatous E. scheuchzeri in all four components measured (vegetative and reproductive shoots and stems) under the same climatic regime in central Alaska over one growing season. Greatest allocation to vegetative shoot growth occurred in mid-summer in both species. The tussock growth form of E. vaginatum raised shoot meristems 25–30 cm above the soil surface, where temperatures were warmer, permitting shoot growth to begin earlier in spring and continue longer in autumn than in E. scheuchzeri. Consequently, E. vaginatum was able to allocate reserves to reproductive tillers primarily in autumn and early spring, times when minimal reserves were required for vegetative growth. By contrast, the rhizomatous E. scheuchzeri had a more constrained growing season, and allocation to reproduction coincided with allocation to vegetative growth. For this reason, reserves were drawn down more fully in mid-summer in E. scheuchzeri than in E. vaginatum. The more conservative use of nutrient stores in E. vaginatum may relate to its great longevity, reduced allocation to reproduction (including low seedling recruitment), and relatively stable habitats. The mid-seasonal pulse of allocation to reproduction in E. scheuchzeri appears viable only in relatively fertile disturbed sites, where the soil nutrient supply is sufficient to support simultaneous allocation to vegetative growth and reproduction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377194
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  • 4
    Electronic Resource
    Electronic Resource
    Flowering behaviour of a New Zealand mountain grass (1965)
    Springer
    Naturwissenschaften 52 (1965), S. 167-167 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00609293
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  • 5
    Electronic Resource
    Electronic Resource
    Ecology of snow tussocks in the mountain grasslands of New Zealand (1969)
    Springer
    Plant ecology 18 (1969), S. 289-306 
    Details
    ISSN: 1573-5052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Die meisten Arten der Gattung chionochloa sind in Neuseeland endemisch, wo sie extentsiv in der niederalpinen Vegetation dominieren. Die rauhe Umgebung, die niedrigen Sommertemperaturen und besonders die anhaltenden heftigen Winde erlauben nur ein langsames Wachstum bei diesen langlebigen Pflanzen, vor allem in größeren Höhen. Diese Pflanzen zeigen, was die Blüte betrifft, einige ungewöhnliche Anpassungen. Periodische Brände begünstigen die häufigste Art (C.rigida); diese Toleranz wurde aber in der Abwesenheit von Beweidung entwickelt. Die erhebliche Verschlechterung der Alpinen Grasländer in den 120 Jahren seit der Ansiedlung der Europäer kann dem Einfluß der fremden Tiere (Haustieren sowie wilden Tiere) zugeschrieben werden; weitere Änderungen dürften vor allem von der Beweidungsintensität abhängig sein.
    Notes: Summary Most species of the genus Chionochloa are endemic in New Zealand where they dominate extensively in the low-alpine vegetation. The severe environment, low summer temperatures and persistent high winds in particular, allows only slow growth rates, especially at higher altitudes, in these long-lived plants. Flowering in several species is associated with some unusual but adaptive features, of which the combined temperature-daylength control of flowering and non-flowering years may be unique among grasses. Adaptive genetic variants of the most widespread species, C. rigida, exploit a wide altitudinal range. This species is favoured by periodic fires but its tolerance was evolved in the absence of grazing mammals. The serious deterioration of alpine grasslands in the 120 years since European settlement can be attributed largely to the alien domestic and feral animals, and future changes will probably reflect the intensity of their grazing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00332843
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  • 6
    Electronic Resource
    Electronic Resource
    Succession in a New Zealand alpine cushion community: a Markovian model (1987)
    Springer
    Plant ecology 71 (1987), S. 129-138 
    Details
    ISSN: 1573-5052
    Keywords: Alpine vegetation ; Cushion growth ; Permanent plot ; Vegetation change
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A permanent plot in a low-alpine cushion/tussock/shrub community was mapped at ca. decade intervals from 1953 to 1984. Transition probabilities between vegetation types were calculated, and a Markovian model was fitted. In spite of non-stationarity a Markov model was consistent with the observations, and produced reasonable predictions, especially for the major components of the vegetation. The model predictions were conservative in terms of future changes, in that future changes would be smaller than those observed, but such predictions could be supported by independent evidence, such as the nature of the non-stationarity, plant counts and seedling numbers. The general pattern was of a decrease in the cover of both Chionochloa rigida tussocks and mixed turf, and an increase in the cover of cushion bog species, especially Donatia novae-zelandiae. Shrubs, the suggested climax, showed no tendency to increase. Known climatic changes cannot explain the trend, which therefore seems to be a local retrogressive succession. There may be a cycle of alternating cushion and turf.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00039165
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