33 research outputs found
Discrete Multiscale Analysis: A Biatomic Lattice System
We discuss a discrete approach to the multiscale reductive perturbative
method and apply it to a biatomic chain with a nonlinear interaction between
the atoms. This system is important to describe the time evolution of localized
solitonic excitations. We require that also the reduced equation be discrete.
To do so coherently we need to discretize the time variable to be able to get
asymptotic discrete waves and carry out a discrete multiscale expansion around
them. Our resulting nonlinear equation will be a kind of discrete Nonlinear
Schr\"odinger equation. If we make its continuum limit, we obtain the standard
Nonlinear Schr\"odinger differential equation
Consequences of a large-scale fragmentation experiment for Neotropical bats : disentangling the relative importance of local and landscape-scale effects
Context
Habitat loss, fragmentation and degradation are widespread drivers of biodiversity decline. Understanding how habitat quality interacts with landscape context, and how they jointly affect species in human-modified landscapes, is of great importance for informing conservation and management.
Objectives
We used a whole-ecosystem manipulation experiment in the Brazilian Amazon to investigate the relative roles of local and landscape attributes in affecting bat assemblages at an interior-edge-matrix disturbance gradient.
Methods
We surveyed bats in 39 sites, comprising continuous forest (CF), fragments, forest edges and intervening secondary regrowth. For each site, we assessed vegetation structure (local-scale variable) and, for five focal scales, quantified habitat amount and four landscape configuration metrics.
Results
Smaller fragments, edges and regrowth sites had fewer species and higher levels of dominance than CF. Regardless of the landscape scale analysed, species richness and evenness were mostly related to the amount of forest cover. Vegetation structure and configurational metrics were important predictors of abundance, whereby the magnitude and direction of response to configurational metrics were scale-dependent. Responses were ensemble-specific with local-scale vegetation structure being more important for frugivorous than for gleaning animalivorous bats.
Conclusions
Our study indicates that scale-sensitive measures of landscape structure are needed for a more comprehensive understanding of the effects of fragmentation on tropical biota. Although forest fragments and regrowth habitats can be of conservation significance for tropical bats our results further emphasize that primary forest is of irreplaceable value, underlining that their conservation can only be achieved by the preservation of large expanses of pristine habitat
Island vs. countryside biogeography: an examination of how Amazonian birds respond to forest clearing and fragmentation
Avian diversity in fragmented Amazonian landscapes depends on a balance between extinction and colonization in cleared and disturbed areas. Regenerating forest facilitates bird dispersal within degraded Amazonian landscapes and may tip the balance in favor of persistence in habitat patches. Determining the response of Amazonian birds to fragmentation may be hindered because many species use adjacent second growth matrices thereby limiting the applicability of island biogeography to predict species loss; alternatively, a countryside biogeographic framework to evaluate the value of regenerating forest may be more appropriate. Here, we used point-count and capture data to compare Amazonian bird communities among continuous forest, 100 ha forest fragments with adjacent second growth, young and older second growth plots, and 100 ha forested islands bounded by water, to test the applicability of island biogeography on the mainland and to assess the ecological value of a regenerating matrix. Among foraging guilds, understory insectivores and flocking species were nearly absent on true islands. Fragments surrounded by young second growth were species rich, suggesting that a developing matrix may mitigate extinction associated with fragmentation. Our findings reinforce that true islands are often extinction-driven systems with distinct, depauperate communities. In contrast, succession of bird communities in second growth facilitates recolonization of forest fragments, permitting fragments as small as 100 ha to support bird communities similar to continuous forest
Island vs. countryside biogeography: an examination of how Amazonian birds respond to forest clearing and fragmentation
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Previous issue date: 2015Avian diversity in fragmented Amazonian landscapes depends on a balance between extinction and colonization in cleared and disturbed areas. Regenerating forest facilitates bird dispersal within degraded Amazonian landscapes and may tip the balance in favor of persistence in habitat patches. Determining the response of Amazonian birds to fragmentation may be hindered because many species use adjacent second growth matrices thereby limiting the applicability of island biogeography to predict species loss; alternatively, a countryside biogeographic framework to evaluate the value of regenerating forest may be more appropriate. Here, we used point-count and capture data to compare Amazonian bird communities among continuous forest, 100 ha forest fragments with adjacent second growth, young and older second growth plots, and 100 ha forested islands bounded by water, to test the applicability of island biogeography on the mainland and to assess the ecological value of a regenerating matrix. Among foraging guilds, understory insectivores and flocking species were nearly absent on true islands. Fragments surrounded by young second growth were species rich, suggesting that a developing matrix may mitigate extinction associated with fragmentation. Our findings reinforce that true islands are often extinction-driven systems with distinct, depauperate communities. In contrast, succession of bird communities in second growth facilitates recolonization of forest fragments, permitting fragments as small as 100 ha to support bird communities similar to continuous forest.
A new technique for grand canonical Monte Carlo simulation: Application in a hard‐disk system
Appendix A. Summary tables detailing number of individual birds censused and sensitivity test results where species richness, evenness and community similarity was estimated using equal effort across treatments and supplementary figures.
Summary tables detailing number of individual birds censused and sensitivity test results where species richness, evenness and community similarity was estimated using equal effort across treatments and supplementary figures
Confinement of discrete breathers in inhomogeneously profiled nonlinear chains
We investigate numerically the scattering of a moving discrete breather on a pair of junctions in a Fermi-Pasta-Ulam chain. These junctions delimit an extended region with different masses of the particles. We consider (i) a rectangular trap, (ii) a wedge shaped trap, and (iii) a smoothly varying convex or concave mass profile. All three cases lead to DB confinement, with the ease of trapping depending on the profile of the trap. We also study the collision and trapping of two DBs within the profile as a function of trap width, shape, and approach time at the two junctions. The latter controls whether one or both DBs are trapped
Aerobic degradation of polychlorinated biphenyls by Alcaligenes sp. JB1: metabolites and enzymes
Variantenuntersuchung zur geplanten A26 Stade-Hamburg Textband. Anlagenband
TIB: AC 9647+(Anl) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman