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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 90 (1992), S. 429-434 
    ISSN: 1432-1939
    Keywords: Competition ; Methods ; Size ; Substitutive experiment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The objective of this study was to examine the claim that traditional measures of competitive performance in substitutive experiments are biased towards larger plants. Results from a three-year diallele experiment of 6 marsh plant species were analyzed using both Relative Yields (a traditional analysis) and the Relative Efficiency Index (a recently proposed analysis presumed to be size-independent). In adddition, a mechanistic model of competition was used to explore the behavior of both methods of estimating competitive performance. Results from the three-year experiment showed that Relative Yields (RYs) were correlated with the initial sizes of plants for the first two years but not the third. By the third year, RYs were highly correlated with Relative Efficiency Index values (REIs) suggesting that the effects of initial size were eventually overcome. Model results showed that RYs are inherently biased in favor of larger plants during the early phases of competition while REIs are not. Further, model analysis confirmed that the size bias associated with RYs declines with increasing duration of the experiment. It is concluded that current generalizations about the relationship between plant size and competitive ability may be biased by the procedures used to analyze competition experiments.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 112 (1997), S. 403-411 
    ISSN: 1432-1939
    Keywords: Key words Competition ; Species richness ; Vines ; Nutrient enrichment ; Biomass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of competitive suppression by vines on the non-vine plant community have received little attention in temperate habitats. This study investigated the impact vines have on their herbaceous hosts in a wetland community at two soil fertility levels. Plots in an oligohaline marsh were treated in a 2 × 2 factorial design with vine removal and fertilization over two growing seasons. There was no significant interaction between removal and fertilization treatments on any of the measured variables. Vine removal initially caused an increase in light penetration through the canopy, but by the end of the study, plots with vines removed had less light due to a 25% increase in biomass by the plants released from competition with vines. For plots with vines removed, species richness was higher during a brief period in the spring of the second year, but by the end of the study, richness in removal plots decreased relative to controls. Fertilization caused a 40% increase in biomass overall, although only two species, Sagittaria lancifolia L. and Polygonum punctatum Ell., showed dramatic increases. Despite fertilization causing a 40% decrease in light penetration to the ground, no change in species richness was observed. Overall, these results show that vine cover in this wetland suppresses non-vine species and reduces community biomass. Removal of vines increased biomass of non-vine dominants but resulted in only an ephemeral change in species richness. Fertilization did not increase the effects of vines on the non-vine community.
    Type of Medium: Electronic Resource
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