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581.
Although Late Pleistocene extinctions disproportionately affected larger mammalian species, numerous smaller species were also lost. To date, no satisfactory explanation has been presented to account for this pattern. Beginning with the assumption that human predation caused the extinctions, we offer and test the first such explanatory hypothesis, which is predicated on considering more realistic functional response forms (i.e., those that allow for predator interference or prey sharing). We then test the hypothesis via a one-predator, six-prey ecological model that maintains transparency, minimalism of design, and maximal constraint of parameters. Results indicate that altering assumptions about one cornerstone of ecological modeling (i.e., functional response) fails to produce qualitative differences in survival–extinction outcomes—even in conjunction with a wide range of capture efficiency permutations. This unexpected finding suggests that no reasonable form of predation alone is capable of producing the survival–extinction pattern observed. We conclude that the matter of causation and the conclusions of previous Late Pleistocene extinction models remain far less certain than many have assumed. 相似文献
582.
Jeffrey A. Bloczynski William T. Bogart Benjamin F. Hobbs Joseph F. Koonce 《Environmental management》2000,26(2):175-193
The model, a stochastic dynamic program, is used to optimize the timing and type of protective structure under a range of
management goals. A wetland can either be optimal for fish or optimal for mammals and waterfowl, but not both. Because credible
estimates of the economic values of wetland services do not exist, we treat those values as parameters in a multiobjective
analysis and show the decisions implied by alternative valuations. The model is applied to the case of Metzger Marsh, a Lake
Erie coastal wetland near Toledo, Ohio, where the decision was made in 1993 to construct an open dike. We find that the optimal
decision is robust with respect to varying assumptions about the formation of barrier beaches and the probability of climate
change, but that the decision is not robust to assumptions concerning the health of an unprotected Metzger Marsh. The most
important source of uncertainty is the biological health of an unprotected wetland. 相似文献
583.
584.
Transfer of a Pathogen from Fish to Amphibians 总被引:3,自引:0,他引:3
Abstract: Ecological studies of exotic species focus primarily on how invaders directly affect particular resident species. In contrast, little is known about the indirect effects of introduced species on native communities, including how pathogens may be spread by introduced species. We provide evidence suggesting that introduced fish may serve as a vector for a pathogenic oomycete, Saprolegnia ferax , that has been associated with embryonic mortality of amphibians in the Cascade Mountains of Oregon, U.S.A. In laboratory experiments, mortality induced by S. ferax was greater in western toad ( Bufo boreas ) embryos exposed directly to hatchery-reared rainbow trout ( Oncorhynchus mykiss ) experimentally infected with S. ferax and hatchery-reared trout not experimentally infected than in control embryos. Embryos also developed significant S. ferax infections when raised on soil that was exposed to trout experimentally infected with S. ferax . Furthermore, toad embryos exposed to S. ferax isolated from sites where Saprolegnia outbreaks are common experienced higher mortality than embryos exposed to S. ferax isolated from sites where Saprolegnia outbreaks have not occurred. Given the widespread practice of introducing hatchery-reared fishes, we suggest that fish used in stocking programs could be an important vector for diseases responsible for amphibian losses. 相似文献
585.
Sherma J 《Journal of environmental science and health. Part. B》2011,46(7):557-568
Techniques and applications of thin layer chromatography (planar chromatography) for the separation, detection, qualitative and quantitative determination, and preparative isolation of pesticides and their metabolites and other related compounds are reviewed for the period from November 1, 2008 to November 1, 2010. Analyses are described for a variety of samples types and pesticide classes. In addition to references on residue analysis, studies such as pesticide structure-retention relationships, identification and characterization of plant pesticides and synthesized pesticides, metabolism, degradation, mobility, identification of biomarkers for detection of herbicide effects in plants, and lipophilicity are covered. 相似文献
586.
Montgomery MT Coffin RB Boyd TJ Smith JP Walker SE Osburn CL 《Environmental pollution (Barking, Essex : 1987)》2011,159(12):3673-3680
The nitrogenous energetic constituent, 2,4,6-Trinitrotoluene (TNT), is widely reported to be resistant to bacterial mineralization (conversion to CO2); however, these studies primarily involve bacterial isolates from freshwater where bacterial production is typically limited by phosphorus. This study involved six surveys of coastal waters adjacent to three biome types: temperate broadleaf, northern coniferous, and tropical. Capacity to catabolize and mineralize TNT ring carbon to CO2 was a common feature of natural sediment assemblages from these coastal environments (ranging to 270+/−38 μg C kg−1 d−1). More importantly, these mineralization rates comprised a significant proportion of total heterotrophic production. The finding that most natural assemblages surveyed from these ecosystems can mineralize TNT ring carbon to CO2 is consistent with recent reports that assemblage components can incorporate TNT ring carbon into bacterial biomass. These data counter the widely held contention that TNT is recalcitrant to bacterial catabolism of the ring carbon in natural environments. 相似文献
587.
The fate of fullerene water suspension (FWS) in an aquatic system of Ceratophyllum sp., a rootless submerged plant, under non-sterile sediment-free conditions was investigated. Fast removal of FWS from water by the plants was observed and irreversible adsorption of C60 onto plants and increasing C60 mass on the plant surface with prolonged exposure durations were confirmed. An intact plant extraction procedure was developed and the majority (>80%) of C60 removed from water was extracted from the plants. C60 remained aggregated after being associated with the plants, which was verified by 13C NMR spectroscopy. Light micrographs showed association of FWS on and in the cuticle layers. 相似文献
588.
Fiona Armstrong Simmance Alison Budden Simmance Jeppe Kolding Kate Schreckenberg Emma Tompkins Guy Poppy Joseph Nagoli 《Ambio》2022,51(3):700
Small-scale inland capture fisheries provide an important source of nutritious food, employment and income to millions of people in developing countries, particularly in rural environments where limited alternatives exist. However, the sector is one of most under-valued fisheries sectors and is increasingly experiencing environmental change. This study adopts a Sustainable Livelihoods Approach and investigates how important a fluctuating inland fishery is to livelihoods, and how local perceptions on challenges corresponds to global evidence. Through an innovative participatory method; photovoice, the lived experiences and perceptions of fishers are depicted. The findings illuminate the valuable role of the sector to food and nutrition security and the complex nexus with vulnerability to climate change. The study responds to the call for more local level assessments of the impacts of climate change on inland fisheries in data-limited environments, and the value of the sector in underpinning the Sustainable Development Goals. Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-021-01583-1. 相似文献
589.
Transpiration and Root Development of Urban Trees in Structural Soil Stormwater Reservoirs 总被引:2,自引:0,他引:2
Julia Bartens Susan D. Day J. Roger Harris Theresa M. Wynn Joseph E. Dove 《Environmental management》2009,44(4):646-657
Stormwater management that relies on ecosystem processes, such as tree canopy interception and rhizosphere biology, can be
difficult to achieve in built environments because urban land is costly and urban soil inhospitable to vegetation. Yet such
systems offer a potentially valuable tool for achieving both sustainable urban forests and stormwater management. We evaluated
tree water uptake and root distribution in a novel stormwater mitigation facility that integrates trees directly into detention
reservoirs under pavement. The system relies on structural soils: highly porous engineered mixes designed to support tree
root growth and pavement. To evaluate tree performance under the peculiar conditions of such a stormwater detention reservoir (i.e., periodically
inundated), we grew green ash (Fraxinus pennsylvanica Marsh.) and swamp white oak (Quercus bicolor Willd.) in either CUSoil or a Carolina Stalite-based mix subjected to three simulated below-system infiltration rates for
two growing seasons. Infiltration rate affected both transpiration and rooting depth. In a factorial experiment with ash,
rooting depth always increased with infiltration rate for Stalite, but this relation was less consistent for CUSoil. Slow-drainage
rates reduced transpiration and restricted rooting depth for both species and soils, and trunk growth was restricted for oak,
which grew the most in moderate infiltration. Transpiration rates under slow infiltration were 55% (oak) and 70% (ash) of
the most rapidly transpiring treatment (moderate for oak and rapid for ash). We conclude this system is feasible and provides
another tool to address runoff that integrates the function of urban green spaces with other urban needs. 相似文献