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Edward Ott - One of the best experts on this subject based on the ideXlab platform.
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impedance and power fluctuations in linear chains of coupled wave chaotic Cavities
Physical Review E, 2012Co-Authors: Gabriele Gradoni, T M Antonsen, Edward OttAbstract:The flow of electromagnetic wave energy through a chain of coupled Cavities is considered. The Cavities are assumed to be of sufficiently irregular shape that their eigenmodes are described by random matrix theory. The Cavities are coupled by electrically short single mode transmission lines. Approximate expressions for the power coupled into successive Cavities are derived, and the predictions are compared with Monte Carlo simulations. The analytic formulas separate into a product of factors. Consequently, the distribution of power in the last cavity of a very long chain approaches lognormal. For lossless Cavities, signatures of Anderson localization, similar to those of the conductances of quantum wires, are observed.
Seth Magle - One of the best experts on this subject based on the ideXlab platform.
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Tree cavity availability across forest, park, and residential habitats in a highly urban area
Urban Ecosystems, 2015Co-Authors: Jalene M. Lamontagne, R. Julia Kilgour, Elsa C. Anderson, Seth MagleAbstract:Tree Cavities are used by a wide variety of species for nesting, food storage, and cover. Most studies on cavity availability have been conducted in forests, and little is known about urban areas. With urbanization, species that excavate Cavities may be less abundant, natural tree-decay processes are managed, and tree densities are reduced, all of which may influence tree-cavity availability. We investigated three questions: 1) What is the prevalence of tree Cavities in different habitats in the Chicago area? 2) How do the characteristics of natural and woodpecker-excavated Cavities and cavity-trees differ across habitats? 3) How does the urban landscape influence the prevalence of tree Cavities? We tested the capacity for large urban parks and residential areas to provide tree Cavities at levels similar to forested areas. We surveyed 1,545 trees in these three habitats for excavated and natural (caused by decay) Cavities. Cavities were most available in forests, where the density of trees was highest. We found that a similar proportion of trees in forests and parks had excavated Cavities, but excavated Cavities were rare in residential areas. Trees containing Cavities were larger than control trees and had more decay, and excavated Cavities were in larger trees with more decay than natural cavity trees. Canopy cover was the main landscape variable influencing excavated cavity availability. Our results suggest that the prevalence of tree Cavities may not be a limiting factor for urban wildlife, however that is contingent on the levels of use of natural Cavities, which is currently unknown.
Kathy Martin - One of the best experts on this subject based on the ideXlab platform.
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Persistence of tree Cavities used by cavity‐nesting vertebrates declines in harvested forests
The Journal of Wildlife Management, 2013Co-Authors: Amanda B. Edworthy, Kathy MartinAbstract:An abundant supply of cavity-bearing trees is important for maintaining wildlife communities in harvested forests. During harvesting, suitable trees and Cavities are directly removed, and the longevity of Cavities in retained trees may be reduced by increased exposure to wind and other disturbance factors. We examined patterns of cavity survival in retained trembling aspen (Populus tremuloides) trees in harvested stands compared with those in unharvested mature stands by monitoring the persistence of individual Cavities. We followed 930 Cavities in 3 harvest treatments for up to 17 years in pre-cut and uncut forest, and up to 13 years post-harvest (reserve patches and dispersed retention), in temperate-mixed forests of interior British Columbia, Canada. Average annual cavity loss rates were 5.6% in pre-cut and uncut forest, 7.2% for Cavities in trees retained in reserves, and 8.1% for Cavities in retained trees dispersed throughout cuts. Correspondingly, median cavity longevity was 15 years for Cavities in pre-cut and uncut forest, 10 years for Cavities retained in reserves, and 9 years for those in dispersed retention. Risk of loss increased most for Cavities in living trees (factor of 2.17), but we found no detectable difference for Cavities in recently dead trees and trees with advanced decay. We suggest retention of a range of aspen size and decay classes to allow for future cavity-tree recruitment in harvested stands. Inclusion of wildlife reserves as part of an overall forest management plan will also help to mitigate the effects of windthrow and maintain long-lived cavity resources required by a large portion of forest wildlife. © 2013 The Wildlife Society
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linking fungi trees and hole using birds in a neotropical tree cavity network pathways of cavity production and implications for conservation
Forest Ecology and Management, 2012Co-Authors: Kristina L Cockle, Kathy Martin, Gerardo RobledoAbstract:Abstract In tropical forests and savannahs worldwide, hundreds of species of cavity-nesting vertebrates depend, for nesting and roosting, on the limited resource of tree Cavities. These Cavities are produced by avian excavators and decay processes in trees infected with heart-rot fungi. Conservation of cavity-nesting communities requires a solid understanding of how Cavities are produced and used; however, no studies have examined the interactions among cavity producers and consumers in tropical forest. Moreover, the role of heart-rot fungi in producing Cavities for nesting vertebrates has not been studied at the community level anywhere in the world. We studied a “nest web”, or interspecific hierarchical network of cavity producers and users, in the Atlantic forest, a tropical biodiversity hotspot of high conservation concern, in South America. We searched for active nests in tree Cavities from 2006 to 2010, and determined the species of trees, heart-rot fungi, and avian excavators that produced the Cavities and the species of non-excavating birds (secondary cavity-nesters) that used them. We identified two main pathways that produced the Cavities used by non-excavators. Thirty-three percent of passerine nests and 9% of non-passerine nests were in Cavities produced by avian excavators; the majority of nests (83% overall) were in Cavities produced directly by decay processes including mechanical damage, invertebrate damage, and fungal decay (non-excavated Cavities). Trees bearing Cavities produced by excavators were 2/3 the diameter of those bearing non-excavated Cavities, had eight times the odds of being dead, and 37 times the odds of being colonized with heart-rot fungi in the family Polyporaceae s.l. (vs. Hymenochaetaceae that were dominant in trees bearing non-excavated Cavities). In contrast to nest webs in North America, the Atlantic Forest nest web was characterized by high diversity and evenness of interactions, whereby non-excavating bird species did not depend on any one species of tree, fungus or avian excavator for cavity production. The community should thus be relatively robust to extinctions of cavity producing species. However, on-going destruction of large living trees with non-excavated Cavities is likely to disrupt the major pathway of cavity production, and may result in a shift toward greater dependence on excavated Cavities in smaller, dead trees, infected with Polyporaceae and occupied primarily by passerine birds. To conserve cavity-using communities in tropical forests, governments and certification agencies should implement policies that result in the retention of several large living trees per hectare.
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nest site reuse patterns for a cavity nesting bird community in interior british columbia
The Auk, 2002Co-Authors: Kathryn E H Aitken, Kathy Martin, Karen L WiebeAbstract:Abstract Most obligate cavity-nesting birds are considered to be nest-site limited, either by time or energy to excavate or to acquire suitable holes for nesting. We examined rates of nest-cavity reuse for a rich community of cavity-nesting birds in mixed forests in interior British Columbia. Using a sample of 402 cavity-reuse cases over five years, we measured cavity reuse for 20 cavity-nesting bird and mammal species (three guilds), and examined the relationship between nest-cavity reuse and features of Cavities, nest trees, and forest stands. Eight percent of used Cavities were destroyed between years. Reuse rates were 17% for the Cavities of weak excavators such as nuthatches and chickadees, 28% for formerly active woodpecker nests, and 48% for Cavities previously used by secondary cavity nesting birds, but there was considerable species variation within all guilds. Nest Cavities in aspen that were deep with large entrances had the highest reuse. At the forest stand level, Cavities in trees close to e...
Carlos A. Martín - One of the best experts on this subject based on the ideXlab platform.
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The role of woodpeckers (family: Picidae) as ecosystem engineers in urban parks: a case study in the city of Madrid (Spain)
Urban Ecosystems, 2021Co-Authors: Patricia Catalina-allueva, Carlos A. MartínAbstract:Many species of the family Picidae, such as the woodpeckers, excavate the tree-Cavities where they nest. Frequently the Cavities are used during a single breeding season and subsequently abandoned, which allows their use by non-excavator species for nesting or roosting. Here we analyze the role of woodpeckers as providers of nesting and refuge places in two urban parks in the city of Madrid. The environmental characteristics of the woodpecker nest-sites were also studied. Prior to the breeding season 75 trees bearing woodpecker-excavated Cavities and 142 control trees (i.e. without woodpecker Cavities) were located, georeferenced and characterized by a set of variables relative to the tree and its environment. During the breeding season the Cavities were monitored with an endoscopic camera to verify occupation and user identity. Additionally, 71 non-excavated tree-Cavities were monitored to measure their occupancy and make comparisons with those excavated by woodpeckers. Woodpeckers showed a strong preference for trees of the genus Populus : 54 of 75 (72%) woodpecker-Cavities were in poplars, which comprised only 7–10% of available trees. The excavated Cavities were found mainly in the trunk of the trees, north oriented and away from paths. The occupancy rate by bird species was higher, although not significantly, for excavated Cavities than for natural Cavities (36.0% and 23.9% respectively). The richness and composition of cavity-user species also differed between types of tree-Cavities. This work shows the importance of woodpeckers as providers of nesting and refuge places for other cavity-user birds and highlights their role as ecosystem engineers in urban parks. Finally, we consider that these results can guide biodiversity conservation efforts in urban planning.
S. Itou - One of the best experts on this subject based on the ideXlab platform.
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Diffraction of a stress wave by two circular cylindrical Cavities in an infinite elastic strip
Computers & Structures, 2003Co-Authors: S. ItouAbstract:Abstract Dynamic stresses around two circular cylindrical Cavities in an infinite elastic strip are considered during passage of a plane step stress wave. The center lines of the Cavities are situated on the mid-surface of the strip. The tensile stress wave impinges on the Cavities parallel to the plane boundaries. The Laplace transformation in time is used and the boundary conditions at the plane surfaces and those at the circular Cavities are satisfied with the aid of the Fourier transformation and the Schmidt method, respectively. The Laplace transformed stresses at the Cavities are inverted numerically in the physical space.