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71.
Joshua.E. Cinner Carl. Folke Tim. Daw Christina.C. Hicks 《Global Environmental Change》2011,21(1):7-12
Environmental change often requires societies to adapt. In some instances, these adaptations can create feedbacks that amplify the change. Alternatively, other adaptations may dampen the change. We used semi-structured interviews with 240 fishers from nine Tanzanian coastal communities to explore responses to four hypothetical scenarios of increasingly severe declines in their average catch (10%, 20%, 30% and 50%). Overall, a higher proportion of fishers said they would respond to decline using amplifying adaptations (such as fishing harder) than dampening adaptations (such as reducing effort), particularly in the scenarios with lower levels of decline. We used a redundancy analysis to explore whether certain types of responses were related to the fishers’ socioeconomic characteristics. Fishers that would employ amplifying responses had greater economic wealth but lacked options. Fishers who would adopt dampening responses possessed characteristics associated with having livelihood options. Fishers who would adopt neither amplifying nor dampening responses were less likely to belong to community groups and sold the largest proportion of their catch. This study provides novel contributions by differentiating aspects of adaptive capacity that will amplify versus dampen environmental change and by highlighting what the resource users’ themselves say regarding responding to environmental change. Although direct policy application is limited by the study's hypothetical scenario nature, it provides a good beginning to incorporating resource users’ voices into such policy discussions. 相似文献
72.
Jenifer E. Dugan David M. Hubbard Henry M. Page Joshua P. Schimel 《Estuaries and Coasts》2011,34(4):839-850
We investigated the role of sandy beaches in nearshore nutrient cycling by quantifying macrophyte wrack inputs and examining
relationships between wrack accumulation and pore water nutrients during the summer dry season. Macrophyte inputs, primarily
giant kelp Macrocystis pyrifera, exceeded 2.3 kg m−1 day−1. Mean wrack biomass varied 100-fold among beaches (range = 0.41 to 46.43 kg m−1). Mean concentrations of dissolved inorganic nitrogen (DIN), primarily NOx−-N, and dissolved organic nitrogen (DON) in intertidal pore water varied significantly among beaches (ranges = 1 to 6,553 μM
and 7 to 2,006 μM, respectively). Intertidal DIN and DON concentrations were significantly correlated with wrack biomass.
Surf zone concentrations of DIN were also strongly correlated with wrack biomass and with intertidal DIN, suggesting export
of nutrients from re-mineralized wrack. Our results suggest beach ecosystems can process and re-mineralize substantial organic
inputs and accumulate dissolved nutrients, which are subsequently available to nearshore waters and primary producers. 相似文献
73.
Joshua D. Cocker 《Australian Journal of Earth Sciences》2013,60(1-2):139-158
Biotite igneous ages and well‐defined isochron ages of plutons from the composite Blue Tier Batholith and the Coles Bay area in northeastern Tasmania range from 395 to 370 Ma. The older limit of this range, for the George River granodiorite, is considerably older than any age previously recorded for NE Tasmania. The ages of the youngest plutons (Mt Paris and Anchor granites), which host cassiterite ores, record pervasive hydrothermal alteration events. The initial 87Sr/80Sr ratios of the granitoids range from 0.7061 to 0.7136 and suggest different protolith compositions, consistent with mineralogical and geochemical characteristics of each pluton. The S‐type garnetbiotite granites (Ansons Bay and Booby alia granites) have initial ratios greater than 0.7119, indicative of enriched, high Rb/Sr ratio, crustal source‐rocks of Proterozoic age (1700–800 Ma). The S‐type biotite granites (Poimena and Pearson granites) have relatively high initial 87Sr/86Sr ratios (0.7070, 0.7105) but overlap with those of the I‐type granodiorites (George River, Scamander Tier, Pyengana and Coles Bay granodiorites) which are in the range of 0.7061 to 0.7073. The initial ratios of the enriched altered plutons are poorly constrained, and on both hand‐specimen and thin‐section scales, reveal open‐system Sr isotopic patterns. Isochron ages for the arenite‐lutite and lutite sedimentary associations of the Mathinna Beds, which are intruded by the granitoids, reflect an approach to Sr isotopic equilibrium during regional metamorphism. The metamorphic age (401 ± 7 Ma) of the early Pragian arenite‐lutite association indicates a relatively small time interval between deposition, regional metamorphism and granitoid intrusion. The isotopic age for the lutite sedimentary association (423 ± 22 Ma) is tentatively correlated with a Benambran‐age burial metamorphic event that has not previously been recorded in Tasmania. 相似文献
74.
In order to better predict the geometry and spatial distribution of reservoir facies and permeability barriers, it is critical to understand stratigraphic geometries and architecture at all scales within a basin. Stratigraphic forward modelling (SFM) allows geologists to forward project the deposition and evolution of sedimentary facies within a stratigraphic framework with given prior boundary conditions. The method can approximate depositional processes while taking into consideration a range of factors that affect basin evolution and sedimentation. This paper presents an overview of recent developments in stratigraphic forward models that are currently available and have been successfully employed in simulating stratigraphic development, including geometric models, diffusion models, Fuzzy Logic models and hydraulic models. In addition, the paper discusses SFM used in the simulation of the behaviour of natural sedimentary systems and verification of the potential for hydrocarbon entrapment and accumulation in a basin using an example from the Ordos Basin, western China. 相似文献
75.
76.
Groundwater discharge along a channelized Coastal Plain stream 总被引:1,自引:1,他引:0
Danita M. LaSage Joshua L. Sexton Abhijit Mukherjee Alan E. Fryar Stephen F. Greb 《Journal of Hydrology》2008,360(1-4):252-264
In the Coastal Plain of the southeastern USA, streams have commonly been artificially channelized for flood control and agricultural drainage. However, groundwater discharge along such streams has received relatively little attention. Using a combination of stream- and spring-flow measurements, spring temperature measurements, temperature profiling along the stream-bed, and geologic mapping, we delineated zones of diffuse and focused discharge along Little Bayou Creek, a channelized, first-order perennial stream in western Kentucky. Seasonal variability in groundwater discharge mimics hydraulic-head fluctuations in a nearby monitoring well and spring-discharge fluctuations elsewhere in the region, and is likely to reflect seasonal variability in recharge. Diffuse discharge occurs where the stream is incised into the semi-confined regional gravel aquifer, which is comprised of the Mounds Gravel. Focused discharge occurs upstream where the channel appears to have intersected preferential pathways within the confining unit. Seasonal fluctuations in discharge from individual springs are repressed where piping results in bank collapse. Thereby, focused discharge can contribute to the morphological evolution of the stream channel. 相似文献
77.
A. Markowitz J. N. Reeves P. Serlemitsos T. Yaqoob H. Awaki A. Fabian L. Gallo R. E. Griffiths H. Kunieda G. Miniutti R. Mushotzky T. Okajima 《Astronomische Nachrichten》2006,327(10):1087-1090
We present preliminary results from a 150 ks Suzaku observation of the Seyfert 1 galaxy NGC 3516. Suzaku 's wide bandpass has enabled us to deconvolve the broadband emitting and absorbing components in this object, breaking model degeneracies inherent in previous, smaller‐bandpass spectra. The primary power‐law continuum is absorbed by an ionized absorber as well as a partial‐covering absorber; the column density of the ionized absorber has increased by a factor of ∼3 since XMM‐Newton observations in 2001. We detect a soft power‐law component which may be scattered emission. We confirm the presence of the broad Fe line, finding a eV equivalent width line that indicates emission extending down to a few Schwarzschild radii. Models which exclude either the broad line or the partial‐covering absorber are rejected. Suzaku 's high effective area and low background near 6 keV also allow us to resolve the narrow Fe K emission line; we find a FWHM velocity width near 4000 km s–1, commensurate with Broad Line Region velocities. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
78.
George J. Bendo Joshua E. Barnes 《Monthly notices of the Royal Astronomical Society》2000,316(2):315-325
We use Gauss–Hermite functions to study the line-of-sight velocity distributions in simulated merger remnants. Our sample contains 16 remnants; eight produced by mergers between disc galaxies of equal mass, and eight produced by mergers between disc galaxies with mass ratios of 3:1. The equal-mass mergers display a wide range of kinematic features, including counterrotation at large radii, orthogonally rotating cores and misaligned rotational axes. Most of the unequal-mass remnants exhibit fairly regular disc-like kinematics, although two have kinematics more typical of the equal-mass remnants. Our results may be compared with observations of early-type objects, including ellipticals with misaligned kinematic axes, counterrotating systems and S0 galaxies. 相似文献
79.
Bulk density effects on soil hydrologic and thermal characteristics: A numerical investigation
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Soil bulk density (ρb) is commonly treated as static in studies of land surface dynamics. Magnitudes of errors associated with this assumption are largely unknown. Our objectives were to (a) quantify ρb effects on soil hydrologic and thermal properties and (b) evaluate effects of ρb on surface energy balance and heat and water transfer. We evaluated 6 soil properties, volumetric heat capacity, thermal conductivity, soil thermal diffusivity, water retention characteristics, hydraulic conductivity, and vapour diffusivity, over a range of ρb, using a combination of 6 models. Thermal conductivity, water retention, hydraulic conductivity, and vapour diffusivity were most sensitive to ρb, each changing by fractions greater than the associated fractional changes in ρb. A 10% change in ρb led to 10–11% change in thermal conductivity, 6–11% change in saturated and residual water content, 49–54% change in saturated hydraulic conductivity, and 80% change in vapour diffusivity. Subsequently, 3 field seasons were simulated with a numerical model (HYDRUS‐1D) for a range of ρb values. When ρb increased 25% (from 1.2 to 1.5 Mg m?3), soil temperature variation decreased by 2.1 °C in shallow layers and increased by 1 °C in subsurface layers. Surface water content differed by 0.02 m3 m?3 for various ρb values during drying events but differences mostly disappeared in the subsurface. Matric potential varied by >100 m of water. Surface energy balance showed clear trends with ρb. Latent heat flux decreased 6%, sensible heat flux increased 9%, and magnitude of ground heat flux varied by 18% (with a 25% ρb increase). Transient ρb impacted surface conditions and fluxes, and clearly, it warrants consideration in field and modelling investigations. 相似文献
80.
The development of surface hydrological connectivity is a key determinant of flood magnitude in drylands. Thresholds in runoff response may be reached when isolated runoff-generating areas connect with each other to form continuous links to river channels, enabling these areas to contribute to flood hydrographs. Such threshold behaviour explains observed nonlinearities and scale dependencies of dryland rainfall–runoff relationships and complicates attempts at flood prediction. However, field methods for measuring the propensity of a surface to transmit water downslope are lacking, and conventional techniques of infiltration measurement are often inappropriate for use on non-agricultural drylands. Here, we argue for a reconceptualization of the dryland surface runoff process, suggesting that the downslope transfer of water should be considered alongside surface infiltration; that is, there is a need for the “aggregated” measurement of infiltration and overland flow hydraulics. Surface application of a set volume of water at a standardized rate generates runoff that travels downslope; the distance it travels downslope is determined by infiltration along the flow, integration of flow paths, and flow resistance. We demonstrate the potential of such a combined measurement system coupled with structure-from-motion photogrammetry to identify surface controls on runoff generation and transfer on dryland hillslopes, with vegetation, slope, surface stone cover, and surface roughness all having a significant effect. The measurement system has been used on slopes up to 37° compared with the flat surface typically required for infiltration methods. On average, the field workflow takes ~10–15 min, considerably quicker than rainfall simulation. A wider variety of surfaces can be sampled with relative ease, as the method is not restricted to stone and vegetation-free land. We argue that this aggregated measurement represents surface connectivity and dryland runoff response better than standard hydrological approaches and can be applied on a much greater variety of dryland surfaces. 相似文献