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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Blackwell Science Inc
    Restoration ecology 13 (2005), S. 0 
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Ozark glades are gaps in forested areas that are dominated by grasses and forbs growing in rocky, nutrient-poor soil. Historically, these open, patchy habitats were maintained by natural and anthropogenic fire cycles that prohibited tree encroachment. However, because of decades of fire suppression, glades have become overgrown by fire-intolerant species such as Eastern red cedar (Juniperus virginiana). Current restoration practices include cutting down invasive cedars and burning brush piles, which represent habitat for Northern fence lizards (Sceloporus undulatus). Because Sceloporus actively consumes herbivores, we hypothesized that the presence of these lizards in and around brush piles might result in a trophic cascade, whereby damage on native plants is reduced. Field surveys across six Missouri glades indicated that lizard activity was minimal beyond 1 m from habitat structures. This activity pattern reduced grasshopper abundance by 75% and plant damage by over 66% on Echinacea paradoxa and Rudbeckia missouriensis near structures with lizards. A field transplant experiment demonstrated similar reductions in grasshopper abundance and damage on two other glade endemic species, Aster oblongifolius and Schizachyrium scoparium. These results demonstrate that future glade restoration efforts might benefit from considering top-down effects of predators in facilitating native plant establishment.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Ecology, Evolution, and Systematics 28 (1997), S. 467-494 
    ISSN: 0066-4162
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Trophic structure, the partitioning of biomass among trophic levels, is a major characteristic of ecosystems. Most studies of the forces that shape trophic structure emphasize either "bottom-up" or "top-down" regulation of populations and communities. Recent work has shown that these two forces are not mutually exclusive alternatives, but efforts to model their interaction still often yield unrealistic predictions. We focus on the problems involved with modeling situations in which community composition, including both the number of trophic levels and the species composition within a trophic level, can change. We review the development of these ideas, emphasizing in particular how compositional change can alter theoretical expectations about the regulation of trophic structure. A comparison of studies on the effects of predators and resource productivity in limnetic ecosystems reveals an intriguing disparity between the results of manipulative experiments and those of correlational studies. We suggest that this contrast is a result of the difference in the temporal scales operating in the two types of studies. Ecosystem-level variables may appear to approach an equilibrium in short-term press experiments; however, processes such as invasion and extinction of species will not have time to play out in most such experiments. We found that the responses of ecosystems to short-term experimental treatments involve less change in species composition than is found in natural communities that have diverged in response to local conditions over longer periods. We argue that the results of short-term experiments support the predictions of models in which the species pool does not change, whereas correlational studies among systems support theories that incorporate compositional change.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 416 (2002), S. 427-430 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The diversity of life is heterogeneously distributed across the Earth. A primary cause for this pattern is the heterogeneity in the amount of energy, or primary productivity (the rate of carbon fixed through photosynthesis), available to the biota in a given location. But the ...
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 437 (2005), S. 880-883 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Predation can be intense, creating strong direct and indirect effects throughout food webs. In addition, ecologists increasingly recognize that fluxes of organisms across ecosystem boundaries can have major consequences for community dynamics. Species with complex life histories often shift ...
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-8477
    Keywords: coexistence ; food webs ; herbivory ; plant resistance ; plant tolerance ; priority effects ; trade-offs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract While evolutionary ecologists emphasize different ways in which plants can evolutionarily respond to herbivory, such as resistance or tolerance, community ecology has lagged in its understanding of how these different plant traits can influence interactions, abundance, composition, and diversity within more complex food webs. In this paper, we present a series of models comparing community level outcomes when plants either resist or tolerate herbivory. We show that resistance and tolerance can lead to very different outcomes. A particularly important result is that resistant species should often coexist locally with other, less resistant competitors, whereas tolerant species should not be able to coexist locally with less tolerant competitors, although priority effects allow them to coexist regionally. We also use these models to suggest some insights into the evolution of these traits within more complex communities. We emphasize how understanding the differential effects of plant tolerance and resistance in food webs provides greater appreciation of a variety of empirical patterns that heretofore have appeared enigmatic.
    Type of Medium: Electronic Resource
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