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181.
AbstractEffective policies to protect groundwater-dependent ecosystems require robust methods to determine the environmental flows and levels required to support species and processes. Frameworks to support groundwater management must incorporate the relationships between hydrology and species and ecological processes. These hydro-ecological relationships can be used to develop quantitative, measurable thresholds that are sensitive to changes in groundwater quantity. Here we provide a case study from a group of fens in central Oregon, USA, that are used for cattle watering, but also support numerous sensitive species. We developed quantitative relationships between the position of the water table and wetland indicator plant species and the process of peat development, to propose groundwater withdrawal thresholds. A maximum depth to water table of –0.9 to –34.8 cm for fen plants and –16.6 to –32.2 cm for peat accretion can be tolerated in these wetlands. Defining hydro-ecological relationships as thresholds can support management decisions.
Editor D. Koutsoyiannis; Guest editor M. AcremanCitation Aldous, A.R. and Bach, L.B., 2014. Hydro-ecology of groundwater-dependent ecosystems: applying basic science to groundwater management. Hydrological Sciences Journal, 59 (3–4), 530–544. 相似文献
182.
A Bayesian hierarchical spatio-temporal model for significant wave height in the North Atlantic 总被引:1,自引:1,他引:0
Erik Vanem Arne Bang Huseby Bent Natvig 《Stochastic Environmental Research and Risk Assessment (SERRA)》2012,26(5):609-632
Bad weather and rough seas continue to be a major cause for ship losses and is thus a significant contributor to the risk to maritime transportation. This stresses the importance of taking severe sea state conditions adequately into account in ship design and operation. Hence, there is a need for appropriate stochastic models describing the variability of sea states, taking into account long-term trends related to climate change. Various stochastic models of significant wave height are reported in the literature, but most are based on point measurements without considering spatial variations. As far as the authors are aware, no model of significant wave height to date exploits the flexible framework of Bayesian hierarchical space-time models. This framework allows modelling of complex dependence structures in space and time and incorporation of physical features and prior knowledge, yet at the same time remains intuitive and easily interpreted. This paper presents a Bayesian hierarchical space-time model for significant wave height. The model has been fitted by significant wave height data for an area in the North Atlantic ocean. The different components of the model will be outlined, and the results from applying the model to monthly and daily data will be discussed. Different model alternatives have been tried and long-term trends in the data have been identified for all model alternatives. Overall, these trends are in reasonable agreement and also agree fairly well with previous studies. Furthermore, a discussion of possible extensions to the model, e.g. incorporating regression terms with relevant meteorological data will be presented. 相似文献
183.
Nicola Allison Adrian A. Finch Matthew Newville 《Geochimica et cosmochimica acta》2005,69(15):3801-3811
Use of the coral Sr palaeothermometer assumes that the Sr in coral skeletons is substituted randomly for Ca in the aragonite structure. The presence of Sr in additional phases e.g., strontianite, or the non random distribution of Sr across metal sites in aragonite, would complicate the Sr/Ca-sea surface temperature relationship. We have used Sr K-edge microEXAFS (extended X-ray absorption fine structure) to determine the structural state of Sr across selected microvolumes of four coral skeletons (Porites lobata, Acropora palmata, Pavona clavus, and Montastrea annularis). We used a 5 × 3 μm beam to analyse specific areas of the coral skeletal architecture, i.e., centres of calcification, fasciculi, and dissepiments. All EXAFS analyses refine, within error, to an ideally substituted Sr in aragonite, and we found no evidence of strontianite or partly ordered structural states. Anisotropy in the first shell responses results from the fact that the analysed microvolumes are not necessarily averaged for the responses of all crystal orientations in the aragonite. Although secondary ion mass spectrometry confirmed that Sr/Ca composition can vary substantially between skeletal components, we find no evidence for any contrast in Sr structural state. Sr heterogeneity may result from kinetic effects, reflecting complex disequilibrium processes during crystal precipitation, or biological effects, resulting from variations in the composition of the calcifying fluid which are biologically mediated. 相似文献
184.
Local modification of rock chemistry by deformation 总被引:1,自引:0,他引:1
R. Kerrich W. S. Fyfe B. E. German I. Allison 《Contributions to Mineralogy and Petrology》1977,65(2):183-190
Metabasalts subjected to progressive deformation in large-scale shear zones at Yellowknife display corresponding changes in major element abundances. Deformation, under conditions of greenschist facies metamorphism, has involved grain size reduction from 1200 m to <20 m, depletion of SiO2 (5%) and Na2O, together with hydration, and a decrease in specific gravity from 2.97 to 2.80. Chemical redistribution by deformation has been accomplished through a decrease in grain diameter of quartz and albite by intercrystalline diffusive mass transport (pressure solution), with concomitant transfer of material into extension veins. The degree of chemical modification is related to the finite strain. Deformation has involved a redistribution of 7.1015g of SiO2 over a volume of about 50km3.The microstructure of an adamellite deformed in a shear zone at higher temperature, under conditions of amphibolite facies metamorphism is indicative of dominant dislocation creep. A low degree of tectonic grain refinement is present. Constant values of major element abundances and specific gravity determined across the shear zone at increasing states of strain imply isochemical and isovolumetric deformation. These results are taken to support the precept that crustal deformation is characterised by a low temperature deformation regime dominated by pressure solution, with local changes of rock chemistry and volume; and a high temperature regime in which strain is accommodated principally by dislocation creep, an isochemical and isovolumetric deformation mechanism. 相似文献
185.
Allison L. Dugdale Christopher J. L. Wilson Lawrence D. Leader Jamie A. Robinson L. Jonathon Dugdale 《Mineralium Deposita》2009,44(2):205-219
Historically, carbonate spots have been identified as an indicator of gold mineralization throughout central Victoria, Australia.
However, the exact timing relationships between the growth of carbonates, development of deformation fabrics, and the introduction
of gold has only been determined in more recent times through isolated studies on individual gold deposits. Detailed examination
of the evolution of hydrothermal alteration associated with the Magdala gold deposit at Stawell recognized the fact that there
were at least two generations of carbonate growth, an early rounded ankerite phase that predated gold mineralization and a
later euhedral siderite phase coincident with gold mineralization. This pattern of carbonate growth is repeated in the majority
of significant gold deposits, including Bendigo and Ballarat, throughout central Victoria. Timing relationships within the
carbonates suggest that a fluid was introduced along bedding planes and early deformation fabrics prior to the main upright
folding events that significantly modified the original sedimentary basin. It is suggested that the early rounded carbonates
may have formed as a result of anaerobic oxidation of methane, derived from the sediments and advected along normal growth
faults within the sedimentary basin, through interaction with downward diffusing seawater sulfate. Although the growth of
the early carbonates is not related to gold mineralization, the change in the speciation of the carbonate during the later
carbonate event is critical and can be tracked using a simple geochemical index that can be used not only in areas of outcrop
but also in conjunction with exploration undercover. 相似文献
186.
A study of Halodule wrightii in a shallow subtropical Texas lagoon was performed to obtain seasonal data on its physiological ecology. Leaf production
and biomass dynamics of H. wrightii were intensively monitored along with the underwater light environment at a 1.2-m depth study site over a 21-month period
from June 1995 to February 1997. The annual photosynthetically active radiation (PAR) flux of 6,764 mol m−2 year−1 was more than twice as high as 2,400 mol m−2 year−1, the minimum annual PAR required for maintenance of growth. As light intensity declined, blade chlorophyll a/b ratios increased suggesting that the plants were photo-adapting. Seasonal trends were evident in shoot growth and biomass.
Compared to other Halodule populations in Texas, H. wrightii in LLM displayed slow growth and low biomass, high leaf tissue N content, and low C/N ratio but high N/P ratio of 38 suggesting
that the plants were phosphorus-limited. 相似文献
187.
Ryan Mathur Spencer TitleyFernando Barra Susan BrantleyMarc Wilson Allison PhillipsFrancisco Munizaga Victor MaksaevJeff Vervoort Garret Hart 《Journal of Geochemical Exploration》2009
We examined the copper isotope ratio of primary high temperature Cu-sulfides, secondary low temperature Cu-sulfides (and Cu-oxides) as well as Fe-oxides in the leach cap, which represent the weathered remains of a spectrum of Cu mineralization, from nine porphyry copper deposits. Copper isotope ratios are reported as δ65Cu‰ = ((65Cu/63Cusample/65Cu/63CuNIST 976 standard) − 1) ? 103. Errors for all the analyses are ± 0.14‰ (determined by multiple analyses of the samples) and mass bias was corrected through standard-sample-standard bracketing. The overall isotopic variability measured in these samples range from − 16.96‰ to 9.98‰. 相似文献
188.
189.
Paul G. Matson Louise M. Stevenson Natalie A. Griffiths Christopher R. DeRolph R. Trent Jett Allison M. Fortner Michael W. Jones Nikki J. Jones Teresa J. Mathews 《水文研究》2021,35(9):e14340
Human activities can be powerful drivers of ecosystem change within catchments. While most long-term catchment studies have been conducted at pristine sites, such studies are less common from sites more impacted by human activity. The Oak Ridge National Laboratory's Biological Monitoring and Abatement Program (BMAP) was developed in the mid-1980s to (1) assess compliance with environmental regulations, (2) identify causes of adverse ecological impacts, (3) provide data for human and ecological risk assessments, and (4) evaluate the effectiveness of remedial actions taken to mitigate the impacts of contaminants in soils, groundwater, and surface water by documenting ecological recovery on the Oak Ridge Reservation (ORR), a federally owned 33 476-acre site in eastern Tennessee, managed by the US Department of Energy. The ORR is composed of multiple watersheds containing many small to mid-size streams. BMAP uses an integrated approach for determining stream health; its databases include long-term seasonal records of contaminant concentrations in water and biota, data from aquatic toxicity testing, and surveys of macroinvertebrate and fish assemblages from impacted and reference streams. These long-term data provide valuable records of degradation and recovery in catchment ecosystems. Our objective here is to describe our study system and data series in order to increase awareness of the availability of these long-term data to the catchment science community. 相似文献
190.
RCP4.5: a pathway for stabilization of radiative forcing by 2100 总被引:3,自引:2,他引:1
Allison M. Thomson Katherine V. Calvin Steven J. Smith G. Page Kyle April Volke Pralit Patel Sabrina Delgado-Arias Ben Bond-Lamberty Marshall A. Wise Leon E. Clarke James A. Edmonds 《Climatic change》2011,109(1-2):77-94
Representative Concentration Pathway (RCP) 4.5 is a scenario that stabilizes radiative forcing at 4.5?W?m?2 in the year 2100 without ever exceeding that value. Simulated with the Global Change Assessment Model (GCAM), RCP4.5 includes long-term, global emissions of greenhouse gases, short-lived species, and land-use-land-cover in a global economic framework. RCP4.5 was updated from earlier GCAM scenarios to incorporate historical emissions and land cover information common to the RCP process and follows a cost-minimizing pathway to reach the target radiative forcing. The imperative to limit emissions in order to reach this target drives changes in the energy system, including shifts to electricity, to lower emissions energy technologies and to the deployment of carbon capture and geologic storage technology. In addition, the RCP4.5 emissions price also applies to land use emissions; as a result, forest lands expand from their present day extent. The simulated future emissions and land use were downscaled from the regional simulation to a grid to facilitate transfer to climate models. While there are many alternative pathways to achieve a radiative forcing level of 4.5?W?m?2, the application of the RCP4.5 provides a common platform for climate models to explore the climate system response to stabilizing the anthropogenic components of radiative forcing. 相似文献