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  • 1
    Electronic Resource
    Electronic Resource
    Fractal dimension estimates of a fragmented landscape: sources of variability (1994)
    Springer
    Landscape ecology 9 (1994), S. 279-286 
    Details
    ISSN: 1572-9761
    Keywords: Semivariogram ; anisotropy ; grain size effect ; scale effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Although often seen as a scale-independent measure, we show that the fractal dimension of the forest cover of the Cazaville Region changes with spatial scale. Sources of variability in the estimation of fractal dimensions are multiple. First, the measured phenomenon does not always show the properties of a pure fractal for all scales, but rather exhibits local self-similarity within certain scale ranges. Moreover, some sampling components such as area of sampling unit, the use of a transect in the estimation of the variability of a plane, the location, and the orientation of a transect all affect, to different degrees, the estimation of the fractal dimension. This paper assesses the relative importance of these components in the estimation of the fractal dimension of the spatial distribution of woodlots in a fragmented landscape. Results show that different sources of variability should be considered when comparing fractal dimensions from different studies or regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00129239
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  • 2
    Electronic Resource
    Electronic Resource
    Statistical models for the estimation of net phosphorus sedimentation in lakes (1989)
    Springer
    Aquatic sciences 51 (1989), S. 192-210 
    Details
    ISSN: 1420-9055
    Keywords: Phosphorus ; mass-balance models ; sedimentation ; error propagation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The empirical adequacy of four phosphorus mass-balance models is evaluated with respect to how the prediction error variance of the corresponding net sedimentation parameters is propagated in the steadystate equations. Using the criterion of minimum propagation error variance (PEV), different groups of lakes can be distinguished for which different empirical equations are used to predict net phosphorus sedimentation. The classification reduced prediction error significantly and also reflected different patterns of sedimentation. Application of this criterion to time-series of individual lakes shows that it is possible to determine a priori whether net annual sedimentation will be better correlated to the annual loading or to the lake content. The correlations depended also on the load/lake content ratio, suggesting that net sedimentation is best viewed as the sum of the partial sedimentation of the load and of the partial sedimentation of the lake content. On average, 25% of the load and 18% of the lake content are sedimented annually. Viewing net phosphorus sedimentation as a function of both the load and the lake content can also explain and predict the well-known cross-sectional correlation between phosphorus retention and water residence time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877742
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  • 3
    Electronic Resource
    Electronic Resource
    Some misconceptions about the spurious correlation problem in the ecological literature (1989)
    Springer
    Oecologia 81 (1989), S. 285-288 
    Details
    ISSN: 1432-1939
    Keywords: Spurious correlation ; Ratios ; Relationships ; Statistical inference ; Self-thinning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary It is a common misconception that correlations between variables that share a common term are statistically invalid. Although the idea that such relationships are wholly or partially spurious was rejected decades ago by statisticians, ecologists continue mistakenly to exclude legitimate hypotheses on this basis. Besides directing attention to the statistical literature on the subject, we briefly reconsider the problem from 3 viewpoints: first, the confusion between spurious correlation and spurious inference, second, the problem of concept familiarity and definition, with particular reference to the self-thinning rule for plants, and third, a legitimate concern with measurement error of shared variable components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379817
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  • 4
    Electronic Resource
    Electronic Resource
    The relative importance of biological and chemical processes in the release of phosphorus from a highly organic sediment (1993)
    Springer
    Hydrobiologia 253 (1993), S. 141-150 
    Details
    ISSN: 1573-5117
    Keywords: sediment ; phosphorus ; release ; anaerobiosis ; bacteria ; pH ; dystrophic lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé Les bactéries peuvent jouer un rôle considérable dans le relargage anaérobiques du phosphore, soit en catalysant la réduction des hydroxydes de fer, soit comme source directe d'orthophosphates. On a étudié leur importance dans la libération de phosphore à partir des sédiments d'un lac du bouclier canadien, très riches en matière organique. Le relargage de phosphore et de fer a été mesuré en condition aérobique et anaérobique, avec ou sans stérilisation, et à différents pH. On a également mesuré l'évolution du nombre et de l'activité des bactéries dans les sédiments. Le relargage de P après stérilisation peut être expliqué par la lyse cellulaire. Comparativement à la stérilisation, les changements dans la concentration en oxygène ou l'acidification ont peu ou pas d'effet sur le relargage du P. Les mouvements du fer et du phosphore se produisent indépendament à partir de ces sédiments. La plus grande partie du fer total dissous semble lié aux acides humiques, ce qui n'est pas le cas du phosphore.
    Notes: Abstract Bacteria can play an important role in the process of anaerobic phosphorus release: they can act as a direct source of orthophosphates, or as a catalyst of iron hydroxyde reduction. We studied their influence on phosphorus release from highly organic sediments of a Canadian shield lake. Phosphorus and iron release were measured under aerobic and anaerobic conditions, with or without sterilization, and at different pH. We measured also the abundance and activity of bacteria in sediments. The increased P release after sterilization can be explained by cell lysis. Compared to sterilization, changing oxygen concentrations or acidification had little or no effect on P release. In these sediments, phosphorus and iron movements were independent. Most of the total dissolved iron seemed to be linked to humic acids, but not phosphorus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00050734
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    Paper (German National Licenses)
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