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81.
Greater sage-grouse (Centrocercus urophasianus) are threatened by loss of sagebrush habitat and the spread of West Nile virus throughout much of their range in North America;
yet, future impacts of climate change on these potential stressors have not been addressed. Here, we aim to quantify the potential
impacts of climate change on the distribution of climatically suitable habitat for sagebrush and on transmission risk for
West Nile virus in the eastern portion of the species’ range. We used Maxent to model the current and future climatically
suitable habitat for two dominant sagebrush species in the study area, and we used a degree-day model to predict future West
Nile virus transmission risk under likely climate-change scenarios. Our models suggest that areas with the highest future
suitability for sagebrush habitat will be found in southwestern Wyoming and north-central Montana. The degree-day model suggests
that greater sage-grouse in western portions of the study area, which are generally higher in elevation than where West Nile
virus currently occurs, will see increasing risk of transmission in the future. We developed a spatially explicit map of suggested
management actions based on our predictions that will aid in conservation of the species into the coming decades. 相似文献
82.
Cassandra E. Cook Allison M. McCluskey Randolph M. Chambers 《Estuaries and Coasts》2018,41(4):966-973
The range expansion of exotic plant species, including the invasive reed Phragmites australis, causes widespread structural and functional changes to coastal ecosystems along the Atlantic and Gulf Coasts of North America. Native estuarine species, such as the diamondback terrapin (Malaclemys terrapin), are at risk of adverse effects from rapid habitat changes due to exotic invasions. Diamondback terrapins currently face population threats including by-catch mortality in crab pots, predation, and habitat loss, and populations may continue to suffer if deleterious plant invasions into preferred nesting habitats are left unchecked. We examined the extent to which Phragmites affects nesting of a breeding population of diamondback terrapins at Fisherman Island National Wildlife Refuge on the eastern shore of Virginia, where Phragmites has recently expanded into known areas of terrapin nesting. With data collected from the 2015 nesting season, we quantified the extent to which Phragmites shading could impact nest incubation temperature and determined how Phragmites density impacts the risk of rhizome invasion into nests. We conclude that Phragmites cover greater than 50% would decrease incubation temperatures of terrapin nests sufficiently to produce predominantly male hatchlings. Phragmites cover had no observed effect on root growth into simulated nests, but cover by other dune plant species explained observed trends in root growth. These results suggest that terrapins may be negatively impacted by Phragmites expansion into open nesting sites. Breeding site fidelity exhibited by terrapins and other estuarine species could limit the ability of their populations to adjust to rapid coastal expansion of invasive plant species. 相似文献
83.
84.
Marek J. KOZUBAL Forrest W. GASDIA Ronald F. DANTOWITZ Peter SCHEIRICH Alan W. HARRIS 《Meteoritics & planetary science》2011,46(4):534-542
Abstract– A calibrated lightcurve is presented of the near‐Earth asteroid 2008 TC3, obtained before it impacted Earth on October 7, 2008. The asteroid was observed in unfiltered images from the end of astronomical twilight until the object entered Earth’s shadow about 2 h later. The observations covered a wide range of phase angles from 14.79° to 2.93°, during which the asteroid ranged from 82,000 km to 29,000 km distance from the observer. A method is presented for obtaining photometrically filtered brightness values for the asteroid using unfiltered imaging techniques. Over 1,700 images of the asteroid produce a lightcurve with a peak‐to‐peak variation in V of 0.76 magnitude. Analysis of the lightcurve yields values for H = 30.86 ± 0.01 and G = 0.33 ± 0.03. Combined with other constraints on the kinetic energy and diameter of the asteroid, which suggest a low 1.8 g cm?3 density and albedo 0.05 ± 0.01, the value of H implies an asteroid of about 4.1 m in diameter, 28 m3 in volume, and 51,000 kg in mass. The determined value of G is out of range for normal, larger asteroids of albedo 0.05–0.15. 相似文献
85.
David Forrest 《The Cartographic journal》2013,50(3):213-214
In recent years, the concepts of usability, user experience, and user-centricity have gained in interest. Digital applications, developed in line with criteria related to these approaches, ask for a deeper understanding of users and their requirements. But, even though there is a wide range of methods available, the creation of user-centric applications with good usability and user experience still poses great challenges for developers. This is also true for web maps, i.e. web map applications, which today are ubiquitous on the Internet. They have evolved into an important information and communication tool and address users who do not possess any specific knowledge of Geoinformatics (GI) or Cartography. Despite the efforts made to meet the requirements and preferences of laymen, these users still often face problems when dealing with web map applications. This refers to aspects of design, content, and functionality. Here, participatory design, which is well-known in the field of Software and Web Engineering, might provide a suitable means. By engaging users directly and actively in the application development process, developers are able to gain a profound understanding of the users and their needs. However, there are several open questions regarding the use of participatory design for designing and implementing web map applications: What does the use of participatory design in web map development processes look like in detail? How and to what degree can users be involved in the development processes? Which added values exist? These questions are addressed by the project YouthMap 5020, whose main goal it was to create a prototype youth-centric web map for the Austrian city of Salzburg (zip code 5020). Applying the approach of participatory design, about 120 teenage pupils from several local schools were involved in all kinds of tasks related to the phases of generating the youth-centric Salzburg web city map. Experience and knowledge gained thereby allowed elaborating recommendations generally useful for generating youth-centric web map applications. 相似文献
86.
In‐channel sand mining by dredge removes large quantities of bed sediment and alters channel morphodynamic processes. While the reach‐scale impacts of dredging are well documented, the effects of the dredged borrow pit on the local flow and sediment transport are poorly understood. These local effects are important because they control the post‐dredge evolution of the borrow pit, setting the pit lifespan and affecting reach‐scale channel morphology. This study documents the observed morphological evolution of a large (1·46 million m3) borrow pit mined on a lateral sandbar in the lower Mississippi River using a time‐series of multibeam bathymetric surveys. During the 2·5 year time‐series, 53% of the initial pit volume infilled with sediment, decreasing pit depth by an average of 0·88 m yr?1. To explore the controls of the observed infilling, a morphodynamic model (Delft3D) was used to simulate flow and sediment transport within the affected river reach. The model indicated that infilling rates were primarily related to the riverine sediment supply and pit geometry. The pit depth and length influenced the predicted magnitude of the pit bed shear stress relative to its pre‐dredged value, i.e. the bed‐stress reduction ratio (R*), a metric that was correlated with the magnitude and spatial distribution of infilling. A one‐dimensional reduced‐complexity model was derived using predicted sediment supply and R* to simulate patterns of pit infilling. This simplified model of borrow‐pit evolution was able to closely approximate the amount and patterns of sediment deposition during the study period. Additional model experiments indicate that, for a borrow pit of a set volume, creating deep, longitudinally‐shorter borrow pits significantly increased infilling rates relative to elongated pits. Study results provide insight into the resilience of alluvial river channels after a disturbance and the sustainability of sand mining as a sediment source for coastal restoration. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
87.
Eutrophication has caused strong shifts from perennial seagrass to opportunistic macroalgae and phytoplankton in many coastal ecosystems worldwide, yet responses of the primary-producer assemblage can vary with regional environmental and nutrient-loading conditions. The wider consequences of this variable primary-producer response on the associated animal community are little known. We used large-scale field surveys across 12 study sites with low or high eutrophication levels in two geographic provinces in Atlantic Canada to examine region-specific responses of macrofauna associated with eelgrass beds. In both regions, abundances of all groups increased with eutrophication, but species richness of mobile fishes and invertebrates decreased. Generally, filter feeders, epibenthic detritivores and some herbivores increased, while more hypoxia sensitive species declined. Small fishes and invertebrate predators increased with eutrophication mirrored by decreases in their prey. Despite similar general trends, our results show distinct shifts in species composition in each geographic region associated with differences in food availability and predation refuge offered by phytoplankton and opportunistic epiphytic or benthic macroalgae as well as tolerance to an increasingly hostile physico-chemical environment. So far, the continued persistence of eelgrass beds at our “highly” eutrophied sites indicates intermediate eutrophication levels with short-term benefits for some species. However, the loss of sensitive species and decrease in species richness highlight that eutrophication has already changed seagrass ecosystems in Atlantic Canada. Our work suggests that mitigating these changes will require regional-scale management. 相似文献
88.
Allison J. Quiroga Zachary M. Thompson Kanthasamy K. Muraleetharan Gerald A. Miller Amy B. Cerato 《Acta Geotechnica》2017,12(5):1003-1020
The results of a series of laboratory tests on unimproved and cement-improved specimens of two clays are presented, and the ability of a bounding surface elastoplastic constitutive model to predict the observed behavior is investigated. The results of the oedometer, triaxial compression, extension, and cyclic shear tests demonstrated that the unimproved soil behavior is similar to that of soft clays. Cement-improved specimens exhibited peak/residual behavior and dilation, as well as higher strength and stiffness over unimproved samples in triaxial compression. Two methods of accounting for the artificial overconsolidation effect created by cement improvement are detailed. The apparent preconsolidation pressure method is considerably easier to use, but the fitted OCR method gave better results over varied levels of confining stresses. While the bounding surface model predicted the monotonic behavior of unimproved soil very well, the predictions made for cyclic behavior and for improved soils were only of limited success. 相似文献
89.
Jonathan H. Sharp Kohei Yoshiyama Alexander E. Parker Matthew C. Schwartz Susan E. Curless Allison Y. Beauregard Justin E. Ossolinski Allen R. Davis 《Estuaries and Coasts》2009,32(6):1023-1043
The Delaware River and Bay Estuary is one of the major urbanized estuaries of the world. The 100-km long tidal river portion
of the estuary suffered from major summer hypoxia in the past due to municipal and industrial inputs in the urban region;
the estuary has seen remarkable water quality improvements from recent municipal sewage treatment upgrades. However, the estuary
still has extremely high nutrient loading, which appears to not have much adverse impact. Since the biogeochemistry of the
estuary has been relatively similar for the past two decades, our multiple year research database is used in this review paper
to address broad spatial and seasonal patterns of conditions in the tidal river and 120 km long saline bay. Dissolved oxygen
concentrations show impact from allochthonous urban inputs and meteorological forcing as well as biological influences. Nutrient
concentrations, although high, do not stimulate excessive algal biomass due to light and multiple nutrient element limitations.
Since the bay does not have strong persistent summer stratification, there is little potential for bottom water hypoxia. Elevated
chlorophyll concentrations do not exert much influence on light attenuation since resuspended bottom inorganic sediments dominate
the turbidity. Dissolved inorganic carbon and dissolved and particulate organic carbon distributions show significant variability
from watershed inputs and lesser impact from urban inputs and biological processes. Ratios of dissolved and particulate carbon,
nitrogen, and phosphorus help to understand watershed and urban inputs as well as autochthonous biological influences. Owing
to the relatively simple geometry of the system and localized anthropogenic inputs as well as a broad spatial and seasonal
database, it is possible to develop these biogeochemical trends and correlations for the Delaware Estuary. We suggest that
this biogeochemical perspective allows a revised evaluation of estuarine eutrophication that should have generic value for
understanding other estuarine and coastal waters. 相似文献
90.
James C. Hower Jennifer M.K. O'Keefe Michael A. Watt Timothy J. Pratt Cortland F. Eble J.D. Stucker Allison R. Richardson Irena J. Kostova 《International Journal of Coal Geology》2009,80(2):135-143
Macrinite is a, generally, rare inertinite maceral, often incorporating remnants and fragments of other macerals, including vitrinite, liptinite, and other inertinite. The associated inertinites include multiple forms of funginite. Funginite is also commonly found in association with vitrinite of slightly elevated reflectance and with degraded varieties of vitrinite. Together with the highly degraded macrinite, the latter two associations are here inferred to be part of a continuum of fungal and microbial degradation of peat. In any case, the origin of some macrinite is potentially distinct from that of inertinite generated by fire. 相似文献