Effects of Habitat Fragmentation on Effective Dispersal of Florida Scrub‐Jays

Abstract: Studies comparing dispersal in fragmented versus unfragmented landscapes show that habitat fragmentation alters the dispersal behavior of many species. We used two complementary approaches to explore Florida Scrub‐Jay (Aphelocoma c?rulescens) dispersal in relation to landscape fragmentation. First, we compared dispersal distances of color‐marked individuals in intensively monitored continuous and fragmented landscapes. Second, we estimated effective dispersal relative to the degree of fragmentation (as inferred from two landscape indexes: proportion of study site covered with Florida Scrub‐Jay habitat and mean distance to nearest habitat patch within each study site) by comparing genetic isolation‐by‐distance regressions among 13 study sites having a range of landscape structures. Among color‐banded individuals, dispersal distances were greater in fragmented versus continuous landscapes, a result consistent with other studies. Nevertheless, genetic analyses revealed that effective dispersal decreases as the proportion of habitat in the landscape decreases. These results suggest that although individual Florida Scrub‐Jays may disperse farther as fragmentation increases, those that do so are less successful as breeders than those that disperse short distances. Our study highlights the importance of combining observational data with genetic inferences when evaluating the complex biological and life‐history implications of dispersal.     

THE CONTINUING DEBATE OVER THE EXHAUSTION OF NONFUEL MINERAL RESOURCES

The author examines the various views of mineral scarcity, distinguishing between the physical view and the economic view of exhaustion, with the aim of clarifying where the debate stands now and why.     

Evaluating the Effects of Anthropogenic Stressors on Source‐Sink Dynamics in Pond‐Breeding Amphibians

Although interwetland dispersal is thought to play an important role in regional persistence of pond‐breeding amphibians, few researchers have modeled amphibian metapopulation or source‐sink dynamics. Results of recent modeling studies suggest anthropogenic stressors, such as pollution, can negatively affect density and population viability of amphibians breeding in isolated wetlands. Presumably population declines also result in reduced dispersal to surrounding (often uncontaminated) habitats, potentially affecting dynamics of nearby populations. We used our data on the effects of mercury (Hg) on the American toad ( Bufo americanus) as a case study in modeling the effects of anthropogenic stressors on landscape‐scale amphibian dynamics. We created a structured metapopulation model to investigate regional dynamics of American toads and to evaluate the degree to which detrimental effects of Hg contamination on individual populations can disrupt interpopulation dynamics. Dispersal from typical American toad populations supported nearby populations that would otherwise have been extirpated over long time scales. Through support of such sink populations, dispersal between wetland‐associated subpopulations substantially increased overall productivity of wetland networks, but this effect declined with increasing interwetland distance and decreasing wetland size. Contamination with Hg substantially reduced productivity of wetland‐associated subpopulations and impaired the ability of populations to support nearby sinks within relevant spatial scales. Our results add to the understanding of regional dynamics of pond‐breeding amphibians, the wide‐reaching negative effects of environmental contaminants, and the potential for restoration or remediation of degraded habitats. Evaluación de los Efectos de Estresantes Antropogénicos sobre la Dinámica Fuente‐Vertedero en Anfibios que se Reproducen en Charcas     

COMBUSTION OF LOW QUALITY COALS IN FLUIDIZED BED STEAM GENERATORS

A new combustion technology has been developed in the last decade that permits the burning of low quality coal, lignite and other fuels, while maintaining stack emissions within reasonable limits. Low quality fuels can be burned directly in fluidized beds, taking advantage of low furnace temperatures and chemical activity within the bed to limit SO₂ and NO_x emissions, thereby eliminating the need for stack gas scrubbing equipment. The excellent heat transfer characteristics of the fluidized beds also result in a reduction of total heat transfer surface requirements, thus reducing the size and cost of steam generators. Tests on beds operating at pressures of one to ten atmospheres, at temperatures as high as 900°C, and with gas velocities in the vicinity of 1.30 to 4 m/s, have proven the concept. Early history of this technology is traced, and the progress that has been made in the development of fluidized bed combustion boilers, as well as work currently underway in the United States and overseas are reviewed. Details of selected fluidized bed boiler installations are presented, test results are discussed and the potential application of fluidized bed boilers in industrial plants using peat, anthracite refuse, lignite and lignite refuse is examined. Dans la demière décennie, une nouvelle technique de combustion a vu le jour, permettant de brûler du charbon de qualité inférieure, de la lignite et d'autres combustibles tout en maintenant les émanations de cheminée dans des normes raisonnables. Des combustibles de qualité inférieure peuvent être brûlés directement dans des lits liquéfiés tout en profitant des basses températures de fourneaux et des réactions chimiques dans le lit afín de limiter les émissions de bioxide de soufre (SO₂) et d'oxide nitreux (NO_x), rendant ainsi inutile tout matériel de nettoyage des émanations de cheminée. Les excellentes possibilités en matiêre de transmission de chaleur que présentent les lits liquéfiés permettent également de réduire la surface totale nécessaire au transfert de chaleur, diminuant ainsi la dimension et le coût des générateurs à vapeur. Des essais concluants ont été effectués dans des lits fonctionnant à des pressions de une à dix atmosphères, à des temperatures aussi élevées que 900°C et avec des vitesses d'émanations avoisinant 1.33 á 4 m/s. L'article fait l'historique de cette technique et considère les progrès réalisés dans la construction des chaudières utilisant le procédé de combustion des chaudières des lits liquéfiés ainsi que les travaux actuellement en cours aux Etats-Unis. L'article fournit des details sur les installations utilisant des chaudières pour lits liquéfiés, analyse les résultats des essais et examine les possibilités d'emploi de ces chaudières dans l'industrie alimentée par la tourbe, les déchets d'anthracite, la lignite et ses résidus. En la última década seha desarrollado una nueva tecnología de combustión que permite quemar carbones de bajo grado, lignitos y otros combustibles, manteniendo al mismo tiempo las emisiones de las chimeneas en niveles razonables. Carbones de bajo grado pueden ser quemados directamente en lechos fluizados aprovechando la ventaja de la baja temperature de la cámara de combustión y de la reacciones químicas en el lecho para limitar las emisiones de SO₂ y NO_x, limitando en consecuencia ia necesidad de equipo de limpieza de los gases de chimenea. Las excelentes caracter ísticas de transferencia de calor de los lechos fluizados reducen también las necesidades de superficie de transferencia de calor, lo que resulta en la disminución de costo y tamaño del sistema de generación de vapor. Este concepto queda demostrado por pruebas realized as a presiones de uno a diez atmósferas y temperatures de hasta 900°C, y velocidades de gas en la vecindad de 1.33 a 4 m/s. En este artículo se presenta el desarrollo temprano de esta tecnología, el progreso alcanzado en el desarrollo de calderos utilizando dicha tecnología y los trabajos que se están llevando a cabo en los Estados Unidos en este campo. Se discuten también detalles de instalación de calderos usando la tecnología de lechos fluidizados, las pruebas realizadas así como el potencial de su aplicación en plantas industriales que usan turba, deshechos de antracita, lignito y deshechos de lignito.     

Toxicity and Repellency of Hot Pepper Extracts to Spider Mite,Tetranychus urticae Koch

Increasing concern about persistence and environmental impact of synthetic pesticide residues require development of biodegradable and environmentally safe alternatives. The potential of using fruit extracts of hot pepper as alternatives to synthetic acaricides for controlling the two-spotted spider mite, Tetranychus urticae Koch, is explored in this study. Twenty-four Capsicum accessions (Solanaceae) were screened for their toxicity and repellency to the spider mites. Crude extracts from fruits of C. chinense, C. frutescens, C. baccatum, C. annuum, and C. pubescens were prepared in methanol and tested for their acaricidal properties. Spider mite mortality was greatest (45%) when fruit extract of accession Grif-9169 (C. annuum) was used. Results from diving board bioassays indicated that mites avoided filter paper strips treated with hot pepper extracts from accessions PI-596057 (C. baccatum), PI-195299 (C. annuum), and Grif- 9270 (C. annuum). This investigation suggests that methanolic extracts of these three accessions may have a great potential for repelling spider mites and should be field-tested on a large-scale to assess their value in managing populations of spider mites, which could reduce reliance on synthetic acaricides. An attempt was made to correlate repellency with chemical constituents of fruit extracts of the most repellent accessions to identify chemical sources of repellency. Capsaicin and dihydrocapsaicin, the pungent components of pepper fruit, were not correlated with toxicity or repellency, indicating that these are not likely related to the toxicity or repellency of the pepper fruit extracts. Other, unidentified chemicals are likely responsible for toxicity and repellency to the two-spotted spider mite     

Is the Intensity of Copper Use Still Declining in the USA?

This article examines several deficiencies in the standard procedure for calculating the intensity of metal use. It then investigates the possibility that the long-term decline in the intensity of copper use in the USA, which has persisted for more than four decades, has in recent years come to an end, even though the standard measures of intensity of use indicate a continuation of the downward trend, albeit at a slower rate. If true, the implications are significant for the copper industry worldwide, because the USA is the largest national market for copper. In addition, consumption trends in many other countries in some respects follow those in the USA. The results do provide some support for the hypothesis that intensity of copper use in the USA is no longer falling. They also indicate that the standard procedure significantly underestimates USA copper consumption and in turn intensity of use.