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521.
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Stephanie Meredith Christopher Kaposy Victoria J. Miller Megan Allyse Subhashini Chandrasekharan Marsha Michie 《黑龙江环境通报》2016,36(8):714-719
The ‘Stakeholder Perspectives on Noninvasive Prenatal Genetic Screening’ Symposium was held in conjunction with the 2015 annual meeting of the International Society for Prenatal Diagnosis. During the day-long meeting, a panel of patient advocacy group (PAG) representatives discussed concerns and challenges raised by prenatal cell-free DNA (cfDNA) screening, which has resulted in larger demands upon PAGs from concerned patients receiving prenatal cfDNA screening results. Prominent concerns included confusion about the accuracy of cfDNA screening and a lack of patient education resources about genetic conditions included in cfDNA screens. Some of the challenges faced by PAGs included funding limitations, lack of consistently implemented standards of care and oversight, diverse perspectives among PAGs and questions about neutrality, and lack of access to training and genetic counselors. PAG representatives also put forward suggestions for addressing these challenges, including improving educational and PAG funding and increasing collaboration between PAGs and the medical community. © 2016 John Wiley & Sons, Ltd. 相似文献
523.
Reservoirs have altered the flow regime of most rivers on the globe. To simulate the natural flow regime, experimental floods are being implemented on regulated rivers throughout the world to improve their ecological integrity. As a large-scale disturbance, the long-term sequential use of floods provides an excellent empirical approach to examine ecosystem regime shifts in rivers. This study evaluated the long-term effects of floods (15 floods over eight years) on a regulated river. We hypothesized that sequential floods over time would cause a regime shift in the ecosystem. The floods resulted in little change in the physicochemistry of the river, although particulate organic carbon and particulate phosphorus were lower after the floods. The floods eliminated moss cover on bed sediments within the first year of flooding and maintained low periphyton biomass and benthic organic matter after the third year of flooding. Organic matter in transport was reduced after the third year of flooding, although peaks were still observed during rain events due to tributary inputs and side slopes. The floods reduced macroinvertebrate richness and biomass after the first year of floods, but density was not reduced until the third year. The individual mass of invertebrates decreased by about one-half after the floods. Specific taxa displayed either a loss in abundance, or an increase in abundance, or an increase followed by a loss after the third year. The first three flood years were periods of nonequilibrium with coefficients of variation in all measured parameters increasing two to five times from those before the floods. Coefficients of variation decreased after the third year, although they were still higher than before the floods. Analysis of concordance using Kendall's W confirmed the temporal changes observed in macroinvertebrate assemblage structure. An assessment of individual flood effects showed that later floods had approximately 30% less effect on macroinvertebrates than early floods of similar magnitude, suggesting that the new assemblage structure is more resilient to flood disturbance. We conclude that the floods caused an ecosystem regime shift that took three years to unfold. Additional long-term changes or shifts are expected as new taxa colonize the river from other sources. 相似文献
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Steven R. Abt Christopher I. Thornton Bryan A. Scholl Theodore R. Bender 《Journal of the American Water Resources Association》2013,49(4):923-937
Rock riprap is one of the most widely used erosion control methods for protecting embankments, levees, spillways, and instream structures subjected to overtopping flow conditions. At least 21 stone‐sizing relationships exist to determine the median stone size of a protective riprap layer based on the results of 96 overtopping, laboratory experiments. Test parameters include median stone size, slope, unit discharge, coefficient of uniformity, and riprap layer thickness. A regression analysis was performed relating the observed median stone size to the predicted median stone size to each of the 21 relationships, yielding a coefficient of determination (R2) and percent error for the full spectrum of data. Zonal (partial spectrum of rock sizes) and complexity analyses were also conducted for each relationship. It was resolved that the Khan and Ahmad, and Chang relationships best aligned with the composite dataset. The predictive expressions by Olivier, Hartung and Scheuerlein, Knauss, Maynord, Abt and Johnson, and Siebel yield a noteworthy second tier of stone‐sizing relationships for overtopping conditions. 相似文献
527.
Robert C. Rhew Christopher Chen Yit Arn Teh Dennis Baldocchi 《Atmospheric environment (Oxford, England : 1994)》2010,44(16):2054-2061
Temperate woodland ecosystems are believed to be both a source and sink for atmospheric methyl bromide and methyl chloride. To separate the gross production and consumption fluxes in this ecosystem, we applied a stable isotope tracer technique in field and laboratory-based experiments. Flux measurements were conducted in a California oak-savanna woodland ecosystem at several intervals throughout the day during the wet and dry seasons to observe the diurnal and seasonal variability of fluxes. While gross production was small and variable, gross consumption showed a clear difference between seasons, with much larger rates during the wet season and negligible rates during the dry season. Laboratory incubations confirmed that fluxes were strongly affected by soil moisture. Consumption rates of methyl bromide, however, are less than half of the previous estimates of temperate woodland soil uptake rates during the growing season. Nevertheless, woodlands cover a significant portion of the world's land surface area and may still be an important component of the soil sink for these methyl halides. 相似文献
528.
Christopher Hassall David J. Thompson Ian F. Harvey 《Environmental monitoring and assessment》2010,160(1-4):451-456
We present data on the distributional changes within an order of macroinvertebrates used in biological water quality monitoring. The British Odonata (dragonflies and damselflies) have been shown to be expanding their range northwards and this could potentially affect the use of water quality metrics. The results show that the families of Odonata that are used in monitoring are shifting their ranges poleward and that species richness is increasing through time at most UK latitudes. These past distributional shifts have had negligible effects on water quality indicators. However, variation in Odonata species richness (particularly in species-poor regions) has a significant effect on water quality metrics. We conclude with a brief review of current and predicted responses of aquatic macroinvertebrates to environmental warming and maintain that caution is warranted in the use of such dynamic biological indicators. 相似文献
529.
Christopher D. Hallam Brendan A. Wintle Heini Kujala Amy L. Whitehead Emily Nicholson 《Conservation biology》2020,34(6):1512-1524
Approaches to assess the impacts of landscape disturbance scenarios on species range from metrics based on patterns of occurrence or habitat to comprehensive models that explicitly include ecological processes. The choice of metrics and models affects how impacts are interpreted and conservation decisions. We explored the impacts of 3 realistic disturbance scenarios on 4 species with different ecological and taxonomic traits. We used progressively more complex models and metrics to evaluate relative impact and rank of scenarios on the species. Models ranged from species distribution models that relied on implicit assumptions about environmental factors and species presence to highly parameterized spatially explicit population models that explicitly included ecological processes and stochasticity. Metrics performed consistently in ranking different scenarios in order of severity primarily when variation in impact was driven by habitat amount. However, they differed in rank for cases where dispersal dynamics were critical in influencing metapopulation persistence. Impacts of scenarios on species with low dispersal ability were better characterized using models that explicitly captured these processes. Metapopulation capacity provided rank orders that most consistently correlated with those from highly parameterized and data-rich models and incorporated information about dispersal with little additional computational and data cost. Our results highlight the importance of explicitly considering species’ ecology, spatial configuration of habitat, and disturbance when choosing indicators of species persistence. We suggest using hybrid approaches that are a mixture of simple and complex models to improve multispecies assessments. 相似文献
530.
Krista M.S. Kemppinen Pamela M. Collins David G. Hole Christopher Wolf William J. Ripple Leah R. Gerber 《Conservation biology》2020,34(5):1221-1228
The loss of forest is a leading cause of species extinction, and reforestation is 1 of 2 established interventions for reversing this loss. However, the role of reforestation for biodiversity conservation remains debated, and lacking is an assessment of the potential contribution that reforestation could make to biodiversity conservation globally. We conducted a spatial analysis of overlap between 1,550 forest-obligate threatened species’ ranges and land that could be reforested after accounting for socioeconomic and ecological constraints. Reforestation on at least 43% (∼369 million ha) of reforestable area was predicted to potentially benefit threatened vertebrates. This is approximately 15% of the total area where threatened vertebrates occur. The greatest opportunities for conserving threatened vertebrate species are in the tropics, particularly Brazil and Indonesia. Although reforestation is not a substitute for forest conservation, and most of the area containing threatened vertebrates remains forested, our results highlight the need for global conservation strategies to recognize the potentially significant contribution that reforestation could make to biodiversity conservation. If implemented, reforestation of ∼369 million ha would also contribute substantially to climate-change mitigation, offering a way to achieve multiple sustainability commitments at once. Countries must now work to overcome key barriers (e.g., unclear revenue streams, high transaction costs) to investment in reforestation. 相似文献