Non-destructive estimation of potato leaf chlorophyll from canopy hyperspectral reflectance using the inverted PROSAIL model     

Elizabeth J. Botha  Brigitte Leblon  Bernie Zebarth  James Watmough   《International Journal of Applied Earth Observation and Geoinformation》2007,9(4):360-374

Optimizing nitrogen (N) fertilization in crop production by in-season measurements of crop N status may improve fertilizer N use efficiency. Hyperspectral measurements may be used to assess crop N status by estimating leaf chlorophyll content. This study evaluated the ability of the PROSAIL canopy-level reflectance model to predict leaf chlorophyll content. Trials were conducted with two potato cultivars under different N fertility rates (0–300 kg N ha⁻¹). Canopy reflectance, leaf area index (LAI) and leaf chlorophyll and N contents were measured. The PROSAIL model was able to predict leaf chlorophyll content with reasonable accuracy later in the growing season. The low estimation accuracy earlier in the growing season could be due to model sensitivity to non-homogenous canopy architecture and soil background interference before full canopy closure. Canopy chlorophyll content (leaf chlorophyll content × LAI) was predicted less accurately than leaf chlrophyll content due to the low estimation accuracy of LAI for values higher than 4.5.  相似文献   

Evolution of metamorphic volatiles during exhumation of microdiamond-bearing granulites in the Western Gneiss Region, Norway   总被引：1，自引：0，他引：1  

Rune B. Larsen  Elizabeth A. Eide  Ernst A. J. Burke 《Contributions to Mineralogy and Petrology》1998,133(1-2):106-121

Fluid inclusions in garnet, kyanite and quartz from microdiamond-bearing granulites in the Western Gneiss Region, Norway, document a conspicuous fluid evolution as the rocks were exhumed following Caledonian high- and ultrahigh-pressure (HP–UHP) metamorphism. The most important of the various fluid mixtures and daughter minerals in these rocks are: (N₂ + CO₂ + magnesian calcite), (N₂ + CO₂ + CH₄ + graphite + magnesian calcite), (N₂ + CH₄), (N₂ + CH₄ + H₂O), (CO₂) and (H₂O + NaCl + CaCl₂ + nahcolite). Rutile also occurs in the N₂ + CO₂ inclusions as a product of titanium diffusion from the garnet host into the fluid inclusions. Volatiles composed of N₂ + CO₂ + magnesian calcite characterise the ambient metamorphic environment between HP–UHP (peak) and early retrograde metamorphism. During progressive decompression, the mole fraction of N₂ increased in the fluid mixtures; as amphibolite-facies conditions were reached, CH₄ and later, H₂O, appeared in the fluids, concomitant with the disappearance of CO₂ and magnesian calcite. Graphite is ubiquitous in the host lithologies and fluid inclusions. Thermodynamic modelling of the metamorphic volatiles in a graphite-buffered C-O-H system demonstrates that the observed metamorphic volatile evolution was attainable only if the f _O2 increased from c. −3.5 (±0.3) to −0.8 (±0.3) log units relative to the FMQ oxygen buffer. External introduction of oxidising aqueous solutions along a system of interconnected ductile shear zones adequately explains the dramatic increase in the f _O2. The oxidising fluids introduced during exhumation were likely derived from dehydration of oceanic crust and continental sediments previously subducted during an extended period of continental collision in conjunction with the Caledonian orogeny. Received: 15 December 1997 / Accepted: 25 May 1998  相似文献   

Proximity and complexity in the emergence of high technology industry: The oxbridge comparison     

Elizabeth Garnsey  Helen Lawton Smith 《Geoforum》1998,29(4):433-450

This paper examines similarities and differences in the emergence of high-tech enterprise and the growth of associated industry in Cambridgeshire and Oxfordshire since the 1960s. These cases are viewed as instances of a generic phenomenon: the emergence and growth of the science-based ‘innovative milieu’. A conceptual scheme drawn from complexity studies is used to introduce explanatory coherence into the apparently scattered and disconnected factors relevant to the genesis of high-tech milieux.  相似文献   

Aragonite dissolution on the Bermuda pedestal: Its depth and geochemical significance     

Robert A. Berner  Elizabeth K. Berner  Robin S. Keir 《Earth and Planetary Science Letters》1976,30(2):169-178

The depth distribution of pteropod and planktonic foram tests, and fine-grained (<62 μm) aragonite, high-Mg calcite (12 mode mol.% MgCO₃), and low-Mg calcite has been determined for surface sediments of an area of the eastern slope of the Bermuda pedestal. Over the range 1800–3000 m, fine-grained aragonite and fine-grained high-Mg calcite gradually disappear relative to fine-grained low-Mg calcite, and pteropods gradually disappear relative to planktonic forams. This is interpreted as preferential dissolution of aragonite (and high-Mg calcite) relative to low-Mg calcite over this depth range. Coarse aragonitic debris derived from shallow-water organisms living on the Bermuda platform does not show consistent disappearance over the same depth zone. Chemical analyses of bottom water samples taken at the same time as some of the sediment samples indicate that the degree of saturation with respect to aragonite Ω_A over the zone of aragonite disappearance ranges from 0.55 to 0.85; i.e. major dissolution occurs only at Ω_A values distinctly less than one. These results lend credence to the hypothesis that CaCO₃ dissolution in the oceans, both as aragonite and as calcite, takes place mainly as a response to complex chemical kinetic phenomena and not as a result of the simple attainment of undersaturation (thermodynamic hypothesis) or the resuspension of bottom sediment (hydrodynamic hypothesis).  相似文献   

Assessment of δ13C and C/N ratios in bulk organic matter as palaeosalinity indicators in Holocene and Lateglacial isolation basin sediments,northwest Scotland     

Elizabeth A. V. Mackie  Jeremy M. Lloyd  Melanie J. Leng  Michael J. Bentley  Carol Arrowsmith 《第四纪科学杂志》2007,22(6):579-591

Carbon isotopes (δ¹³C) and C/N ratios from bulk organic matter have recently been used as alternative proxies for relative sea‐level (RSL) reconstruction where there are problems associated with conventional biological indictors. A previous study on a single isolation basin (Upper Loch nan Eala) in northwest Scotland has shown a clear relationship between δ¹³C, C/N ratios and palaeosalinity from Younger Dryas and Holocene aged sediments. In this paper we present results of δ¹³C and C/N ratio analyses from other isolation basins in northwest Scotland over the Holocene and the Lateglacial period in order to validate this technique. The results from the Holocene sequences support the earlier findings that this technique can be used to identify RSL change from isolation basins over the Holocene in this region. The relationship between δ¹³C, C/N ratios and RSL change is not apparent in sediments of Lateglacial age. Other environmental variables such as atmospheric CO₂ concentration, poor vegetation development and temperature influence δ¹³C values during this period. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Volcanic ash clouds affecting Northern Europe: the long view     

Graeme T. Swindles  Ivan P. Savov  Charles B. Connor  Jonathan Carrivick  Elizabeth Watson  Ian T. Lawson 《Geology Today》2013,29(6):214-217

The volcanic ash or ‘tephra’ cloud resulting from the relatively small (volume and VEI) eruption of the Icelandic volcano Eyjafjallajökull in 2010 caused major air travel disruption, at substantial global economic cost. On several occasions in the past few centuries, Icelandic eruptions have created ash and/or sulphur dioxide clouds which were detected over Europe (e.g. Hekla in 1947, Askja in 1875, and Laki in 1783). However, these historical observations do not represent a complete record of events serious enough to disrupt aviation in Europe. The only feasible evidence for this is within the geological tephra record. Ash layers are preserved in bogs and lakes where tephra deposited from the atmosphere is incorporated in the peat/mud. In this article we: 1, introduce the analysis of the Northern European sedimentary tephra record; 2, discuss our findings and modelling results; 3, highlight how these were misinterpreted by the popular media; and 4, use this experience to outline several existing problems with current tephra studies and suggest agendas for future research.  相似文献   

Abundance,distribution, and feeding patterns of juvenile coho salmon (Oncorhynchus kisutch) in the Juan de Fuca Eddy     

Suzan S. Pool  Richard D. Brodeur  N. Lynn Goodman  Elizabeth A. Daly 《Estuarine, Coastal and Shelf Science》2008

The Juan de Fuca Eddy is a seasonal, counter-clockwise gyre off the mouth of the Strait of Juan de Fuca between Washington, USA and British Columbia, Canada that may provide favorable feeding habitat for juvenile coho salmon (Oncorhynchus kisutch) during their early marine existence. In late September 2002, physical and biological sampling was conducted along two transects of the eddy region. Surface rope trawling was conducted to capture juvenile salmon and other nekton, along with bongo and neuston net tows to examine potential mesozooplanktonic salmon prey. Presence of the Juan de Fuca Eddy was confirmed with vertical water profiles. In addition, nutrient and chlorophyll a concentrations collected from 3-m depth were within the range observed in previous studies within the eddy region. In the mesozooplankton community, euphausiids, chaetognaths, and decapod megalopae were common. In the diet of juvenile coho salmon, euphausiids and decapod megalopae were dominant by percent number, and larval and juvenile fish were dominant by percent weight. Feeding intensity (percent body weight) based on stomach contents was variable, but not significantly different among stations. To compare the Juan de Fuca Eddy region with an upwelling area, we sampled along a transect off La Push (LP), Washington, USA which is south of the eddy. The eddy region was found to be less productive than the LP transect. Nutrients were lower, chlorophyll a concentrations were higher, and zooplankton abundance was generally higher along the LP transect than in the eddy region. In addition, more juvenile coho salmon were captured from the LP transect than the eddy region. Prey items in stomachs of salmon from the LP transect were heterogeneous compared to those from the eddy region. Feeding intensity along the LP transect was slightly lower and more variable than in the eddy region, and differences in feeding intensity among LP stations were significant. In addition, feeding intensities among stations nested within regions were significantly different.  相似文献   

Vulnerability assessment for loss of access to drinking water due to extreme weather events   总被引：1，自引：0，他引：1  

Jeanne Luh  Elizabeth C. Christenson  Aizhan Toregozhina  David A. Holcomb  Tucker Witsil  Laura R. Hamrick  Edema Ojomo  Jamie Bartram 《Climatic change》2015,133(4):665-679

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A rare reflection effect eclipsing sdB+dM binary: 2M 1533+3759     

Bi-Qing For  Elizabeth M. Green  Gilles Fontaine  Scott Shaw 《Astrophysics and Space Science》2010,328(1-2):87-90

In this paper, we report a rare reflection effect eclipsing sdB+dM binary, 2M?1533+3759. It is the seventh eclipsing sdB+dM binary that has been discovered to date. This system has an orbital period of 0.16177042 day and a velocity semi-amplitude of 71.1 km?s^?1. Using a grid of zero-metallicity NLTE model atmospheres, we derived T _eff=29250 K, log?g=5.58 and [He/H]=?2.37 from spectra taken near the reflection effection minimum. Lightcurve modeling resulted in a system mass ratio of 0.301 and an orbital inclination angle of 86.6°. The derived primary mass for 2M?1533+3759, 0.376±0.055 M _⊙, is significantly lower than the canonical mass (0.48 M _⊙) found for most previously investigated sdB stars. This implies an initial progenitor mass >1.8 M _⊙, at least a main sequence A star and perhaps even one massive enough to undergo non-degenerate helium ignition.  相似文献   

Detecting infiltration and impacts of introduced water using strontium isotopes   总被引：3，自引：0，他引：3  

Brinck EL  Frost CD 《Ground water》2007,45(5):554-568

Water introduced to surface drainages, such as agricultural and roadway runoff, mine drainage, or coalbed natural gas (CBNG)-produced water, potentially can be of environmental concern. In order to mitigate potential environmental effects, it may be important to be able to trace water discharged to the surface as it infiltrates and interacts with near-surface aquifers. We have chosen to study water withdrawn during CBNG production for isotope tracing in the hyporheic zone because it poses a variety of economic, environmental, and policy issues in the Rocky Mountain states. Ground water quality must be protected as CBNG water is added to semiarid ecosystems. Strontium (Sr) isotopes are effective fingerprints of the aquifer from which water originates. In this study, CBNG water was found to have a higher (87)Sr/(86)Sr ratio than the local alluvial aquifer water. This measurable difference allows the strontium isotope ratio and concentration to be used as tracers of CBNG water following its discharge to the surface. The dissolution and mobilization of salts from soil are an important contributor to ground water quality degradation. In the Powder River basin of Wyoming, the soils are calcium carbonate-buffered systems. The chemical similarity of strontium to calcium allows it to substitute into calcium minerals and enabled us to use strontium isotopes to identify calcium salts mobilized from the soil. Strontium isotopes are an effective monitor of the source of ions and the volume and direction of introduced water flow in the hyporheic zone.  相似文献