Multiscale analysis of vegetation surface fluxes: from seconds to years   总被引：2，自引：0，他引：2  

Gabriel Katul  Chun-Ta Lai  Karina Schfer  Brani Vidakovic  John Albertson  David Ellsworth  Ram Oren 《Advances in water resources》2001,24(9-10)

The variability in land surface heat (H), water vapor (LE), and CO₂ (or net ecosystem exchange, NEE) fluxes was investigated at scales ranging from fractions of seconds to years using eddy-covariance flux measurements above a pine forest. Because these fluxes significantly vary at all these time scales and because large gaps in the record are unavoidable in such experiments, standard Fourier expansion methods for computing the spectral and cospectral statistical properties were not possible. Instead, orthonormal wavelet transformations are proposed and used. The are ideal at resolving process variability with respect to both scale and time and are able to isolate and remove the effects of missing data (or gaps) from spectral and cospectral calculations. Using the spectra, we demonstrated unique aspects in three appropriate ranges of time scales: turbulent time scales (fractions of seconds to minutes), meteorological time scales (hour to weeks), and seasonal to interannual time scales corresponding to climate and vegetation dynamics. We have shown that: (1) existing turbulence theories describe the short time scales well, (2) coupled physiological and transport models (e.g. CANVEG) reproduce the wavelet spectral characteristics of all three land surface fluxes for meteorological time scales, and (3) seasonal dynamics in vegetation physiology and structure inject strong correlations between land surface fluxes and forcing variables at monthly to seasonal time scales. The broad implications of this study center on the possibility of developing low-dimensional models of land surface water, energy, and carbon exchange. If the bulk of the flux variability is dominated by a narrow band or bands of modes, and these modes “resonate” with key state and forcing variables, then low-dimensional models may relate these forcing and state variables to NEE and LE.  相似文献   

Progressive niedriggradige Metamorphose glaukonitführender Horizonte in den helvetischen Alpen der Ostschweiz     

Martin Frey  Johannes C. Hunziker  Peter Roggwiller  Conrad Schindler 《Contributions to Mineralogy and Petrology》1973,39(3):185-218

Glauconite-bearing formations of Cretaceous and Tertiary age in the Helvetic zone of the Glarus Alps have been investigated by microscopic, X-ray, wet chemical, electron microprobe, Mössbauer spectroscopic, and K-Ar dating methods. 3 different metamorphic zones with increasing grade can be distinguished (Fig. 3). Original, unmetamorphosed sediments containing glauconite-calcite-quartz±chlorite comprise zone I. The glauconite is very rich in potassium (8–9 wt.%) and the chlorite is Fe-rich. In zone II green stilpnomelane forms by the reaction: glauconite±chlorite + quartz = stilpnomelane + k-feldspar + H₂O + O₂. The green stilpnomelane contains as much as ten times the amount of K found in brown stilpnomelane, which is believed to be a weathering feature. In zone III biotite appears by the reaction: chlorite + k-feldspar = biotite + stilpnomelane + quartz + H₂O. Riebeckite is a possible additional phase in all three zones. Generally, zones I–III are arranged nearly parallel to the Alpine border with metamorphic grade increasing to the south. In the Glarnisch Massif, however, the transition from zone I to zone II is clearly controlled by the overburden of the nappe pile (Fig. 6). The beginning of zone II also seems to coincide with the middle of the anchizone, as defined by illite-crystallinity measurements in adjoining marly shales and slates; this corresponds approximately to the transition from the zeolite facies to the prehnitepumpellyite facies.K-Ar-ages on glauconites regularly decrease when approaching the zone I/II-transition. Field evidence and combined K-Ar age determinations on glauconites, stilpnomelanes and riebeckites point to a peak of the metamorphism during Lower to Middle Oligocene, shortly after the main orogenic phase in this part of the Helvetic Alps.

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Die Autoren danken Herrn Prof. E. Niggli für das fördernde Interesse an dieser Arbeit, die Überlassung der Probe EN 8999 sowie die kritische Durchsicht des Manuskriptes. Für wertvolle Diskussionen und Hinweise danken wir den Prof. E. Jäger, R. Herb und P. M. Orville sowie Dr. W. D. Brückner und Dr. N. Clauer. M.F. möchte Herrn E. Weber herzlich für die Einführung auf der Mikrosonde danken. Herrn Prof. Th. Hügi danken wir für die Benützung des geochemischen Labors, Herrn Prof. H. Schwander für einige Na-Bestimmungen auf der Basler Mikrosonde und Herrn Dr. F. Hofmann für die Bestimmung der C-Gehalte. Den Herren Theo Küpfer und J. Fuhrimann verdanken wir verschiedene Laborarbeiten. Diese Arbeit wurde durch die folgenden Stipendien des Schweizerischen Nationalfonds zur Förderung der wissenschaftlichen Forschung unterstützt: Nr. 5358.2 an M.F., Nr. 2.367.70 an J.H. sowie Nr. 2598 an P.R. Die Durchführung der Mikrosondenanalysen wurden zudem möglich dank eines Studienaufenthaltes von M. F. an der Yale Universität, New Haven, Connecticut, wofür dieser Autor der Forschungskommission der Universität Bern zu großem Dank verpflichtet ist.  相似文献   

New England granites: Trace element evidence regarding their origin and differentiation     

Grant Buma  Fred A. Frey  David R. Wones 《Contributions to Mineralogy and Petrology》1971,31(4):300-320

The abundances of Sc, rare earths, Zr, Hf, Ta and Th were determined in five New England granitic plutons. Similar data are reported for separated minerals from three of the units. The granites can be divided into the Massachusetts alkaline group (Cape Ann, Peabody, Quincy) and the Rhode Island subalkaline group (Narragansett Pier, Westerly).Analyses for three samples from each pluton indicate that the Westerly granite is heterogeneous in both major and trace elements. Th abundances vary considerably (factor of 2) in both Rhode Island granites. Zr and Hf are heterogeneously distributed in all the granites while the rare earths are more homogeneous (< ± 20% deviation from mean).Eu depletions in all the granites imply that feldspar was involved either as a cumulate during fractional crystallization or as a residual phase during anatexis. Because the Massachusetts granites are associated with syenites and show evidence for low water fugacity and denser rocks at depth, these granites probably developed from basic magmas as a result of extensive feldspar crystallization.Depletion of Tb, Dy, Yb, Lu, Zr, Hf and Ta in the Rhode Island granites suggest participation of zircon or garnet as residues of partial melting or as crystal cumulates. These granites crystallized under nearly water saturated conditions and are characterized by abundant pegmatites. The presence of a water rich phase may also have been important in the depletion of elements which form stable complexes in aqueous solutions.  相似文献   

Characterization of the halophilic archaeal community in saltern crystallizer ponds by means of polar lipid analysis   总被引：1，自引：0，他引：1  

Aharon Oren 《International Journal of Salt Lake Research》1994,3(1):15-29

Saltern crystallizer ponds are coloured red due to the presence of dense communities of red halophilic archaea (family Halobacteriaceae). Little quantitative information exists on the species distribution within the archaeal community in such ponds. As the different genera of the Halobacteriaceae differ in polar lipid content, and especially in the types of glycolipids, lipid analysis can be used to obtain information on the nature of the organisms present. Analysis of the polar lipids extracted from the biomass collected from the saltern crystallizer ponds in Eilat, Israel, showed one major glycolipid to be present, co-chromatographing with the sulfated diglycosyl diether lipid characteristic of the genusHaloferax. No indications were found for the presence of significant amounts of those glycolipids that would indicate the presence of large numbers of other archaea such asHalobacterium species (H. cutirubrum andH. salinarium, characterized by sulfated triglycosyl and tetraglycosyl diethers), orHaloarcula species (possessing a triglycosyl diether). Phosphatidyl glycerosulfate, a polar lipid absent inHaloferax species, was present in the lipid extract from the crystallizer ponds, suggesting that the dominant microorganism present may be related to strains which are presently classified in the genusHalobacterium but are awaiting a taxonomic reappraisal (H. sodomense, H. saccharovorum, andH. trapanicum). Organisms of the latter group are characterized by sulfated diglycosyl diethers, and the presence of phosphatidyl glycerosulfate. Attempts to isolate the dominant type of bacterium on agar plates yielded relatively low counts (1–2 orders of magnitude lower than the numbers observed microscopically) of bacteria, and most of the isolates had a polar lipid composition characteristic of theH. salinarium group or theH. sodomense-H. saccharovorum-H. trapanicum group.  相似文献   

Microtektites: a chemical comparison of bottle-green microtektites,normal microtektites and tektites     

F.A. Frey 《Earth and Planetary Science Letters》1977,35(1):43-48

Trace element abundances in Ivory Coast normal microtektites and Australasian bottle-green microtektites confirm that microtektites are genetically related to tektites in the associated strewn field. Although major and compatible trace element abundances imply that bottle-green microtektites are members of a fractional crystallization sequence, the similar rare earth element distributions in Australasian normal and bottle-green microtektites and tektites cannot be explained by a simple fractionation model. The similar REE abundances in tektites and microtektites of widely different major element composition also preclude simple models calling for sedimentary rock precursors.  相似文献   

Geochemical characteristics of central Chile (33 °–34 °S) granitoids     

Leopoldo López -Escobar  Frederick A. Frey  Jorge Oyarzún 《Contributions to Mineralogy and Petrology》1979,70(4):439-450

Seventeen granitoid samples from batholiths in central Chile (33 °–34 ° S) have been analyzed for trace element content. The samples range in age from Paleozoic to Tertiary, and in rock type from quartz diorite to granite. In general, compared to andesites from central-south Chile these rocks are more siliceous with lower abundances of compatible trace elements and higher abundances of incompatible trace elements. However, Upper Tertiary granodiorites have important geochemical similarities, such as highly fractionated rare-earth element (REE) distributions relative to chondrites, to some modern andesites in this region; e.g., Marmolejo. Similar highly fractionated REE distributions are also common in the cores of zoned intrusive sequences in the Sierra Nevada of the western U.S. Based on limited sampling of central Chile Cretaceous and Tertiary plutonics, there may be a west to east increase in light REE/heavy REE ratio and in Sr content. Compared to the Upper Tertiary granodiorites, the Paleozoic granodiorites have similar REE abundances but lower Sr, Sc, Cr, Co, and Ni contents.  相似文献   

Ultramafic inclusions from San Carlos,Arizona: Petrologic and geochemical data bearing on their petrogenesis   总被引：5，自引：0，他引：5  

Frederick A. Frey  Martin Prinz 《Earth and Planetary Science Letters》1978,38(1):129-176

Ultramafic inclusions from San Carlos, Arizona, are classified into two groups. Group I inclusions are dominated by magnesian (Mg/Mg + ΣFe= 0.86 – 0.91), olivine-rich peridotites containing Cr-rich clinopyroxene and spinel. The less abundant Group I pyroxenites (containing Mg- and Cr-rich pyroxenes) occur as discrete inclusions and as portions of composite inclusions where they have a sharp, planar interface with lherzolite. Group II inclusions are dominated by clinopyroxene-rich peridotites containing Al- and Ti-rich augite and commonly abundant, Al-rich spinel. Compared to Group I inclusions, they are more Fe-rich (Mg/Mg + ΣFe= 0.62 – 0.78) and more hetereogeneous in composition and modal proportions. Similar groups occur at many ultramafic inclusion localities.Our petrographic and geochemical results lead to the following conclusions. Olivine-rich Group I inclusions are not genetically related to the host basanite, and they are formed from two components. Component A is a partial melting residue; it comprises the major portion of these inclusions and determines the modal mineralogy and major and compatible trace element composition. Component B results from a small degree (<5%) of garnet peridotite melting (probably, within the low-velocity zone). This highly LIL-element-enriched melt has migrated upwards into the overlying component A where it crystallized primarily as clinopyroxene and amphibole, and thus, introduced LIL elements into the residual component A. Subsequent cooling and subsolidus recrystallization have removed textural evidence of this mixing. This model has also been proposed for olivine-rich Group I inclusions from Victoria, Australia. At Victoria and San Carlos some relatively clinopyroxene-rich Group I lherzolites are not contaminated by component B, and they represent the best estimates of upper mantle composition prior to melting. Group I orthopyroxenites may be fragments of tectonic layers formed in lherzolite, but they could also be early cumulates (now metamorphosed) from the melt in equilibrium with component A. Group I clinopyroxenites have geochemical features of clinopyroxene in equilibrium with a magma. Thus, they could also represent early cumulates (now metamorphosed) from a magma unrelated to the host basanite. Alternatively, their geochemical characteristics could result from more complex models such as residues from partial remelting of pyroxenite dikes and veins or intradike segregation processes such as filter pressing. All Group II inclusions studied appear to be cumulates derived from a SiO₂-undersaturated magma, possibly an early magma in the same volcanic episode which culminated with eruption of the host basanite. The poikilitic texture of amphibole-rich (kaersutite) inclusions is consistent with a cumulate origin. The bulk compositions of Group II inclusions are not equivalent to typical basaltic compositions.  相似文献   

The mineralogy,geochemistry and origin of Iherzolite inclusions in Victorian basanites   总被引：2，自引：0，他引：2  

Frederick A Frey  David H Green 《Geochimica et cosmochimica acta》1974,38(7):1023-1059

The mineralogy of Iherzolite inclusions in Victorian basanites indicates an upper mantle origin, but a range of temperatures from igneous to metamorphic (subsolidus) is indicated by the mineral compositions. Pyroxene textural features exhibit a slow cooling history consistent with isotopic evidence that these inclusions are accidental xenoliths. Clinopyroxene-rich inclusions (10–20 vol. % cpx) have higher abundances of Ca, Na, AI, Sc, V, Cr and heavy REE, lower Mg/Mg + Fe²⁺, lower Ni abundances, and more fayalitic olivines than clinopyroxene-poor inclusions (<5 vol. % cpx). A surprising result is that the refractory Mg-rich, clinopyroxenepoor inclusions contain the highest abundances of incompatible elements such as P, K, Ti, light REE, Th and U. We believe these inclusions are composed of two components (A and B). Component A determines the major element abundances and primary mineralogy of the inclusions. Based on Ni abundances component A is interpreted as a melting residue rather than a crystallization accumulate. Component B forms a small and varying portion of the inclusions, and it contributes P, K, Ti, light REE, Th and U. This component has the geochemical characteristics of a liquid formed in equilibrium with garnet.The following model is presented for the origin of Iherzolite inclusions. Residual Iherzolite (Component A) is left in the lithosphere after partial fusion, and it is later modified by a melt which has migrated to the top of the low velocity zone. Because this liquid (Component B) results from a small degree ( <6 per cent) of melting (probably limited by water abundance), and has equilibrated with garnet, it will be very enriched in P, K, Ti, light REE, Th and U. Subsequent cooling and recrystallization forms the present mineralogy. Finally, explosive volcanism, characteristic of silica-undersaturated magmas, incorporates mantle fragments (Iherzolite inclusions), and the increasing temperature and decreasing pressure during ascent causes incongruent melting of minor hydrous phases such as phlogopite and amphibole.  相似文献   

Gough Island: Evaluation of a fractional crystallization model   总被引：3，自引：0，他引：3  

Robert A. Zielinski  Fred A. Frey 《Contributions to Mineralogy and Petrology》1970,29(3):242-254

Gough Island is composed of an alkaline olivine basalt-trachyte series. A fractional crystallization model for the development of these rocks has been evaluated by correlating the geochemical trends of major and trace elements. Beginning with an alkali olivine basalt parent the major element abundances were used to determine the varying proportions of crystallizing minerals required to generate the various residual liquids. A least-squares computer model was used for this calculation. The modal proportions of cumulative minerals and trace element distribution coefficients were used to predict the trace element abundances in each rock type.Three significant trace element trends are observed in Gough Island rocks: (1) increasing rare earth (RE) abundance and relative light RE enrichment with increasing major element differentiation, (2) marked Eu, Sr, and Ba depletions in late stage trachytes, (3) Cr and M enrichment in picrite basalt.The trace element abundances predicted by the fractional crystallization model are in good agreement with these observed trends. A fractional crystallization process involving olivine, pyroxene, feldspar, and apatite accounts for all the significant major and trace element trends observed in Gough Island rocks.  相似文献   

Optical tomography of the aurora and EISCAT     

H. U. Frey  S. Frey  B. S. Lanchester  M. Kosch 《Annales Geophysicae》1998,16(10):1332-1342

Tomographic reconstruction of the three-dimensional auroral are emission is used to obtain vertical and horizontal distributions of the optical auroral emission. Under the given experimental conditions with a very limited angular range and a small number of observers, algebraic reconstruction methods generally yield better results than transform techniques. Different algebraic reconstruction methods are tested with an auroral are model and the best results are obtained with an iterative least-square method adapted from emission-computed tomography. The observation geometry used during a campaign in Norway in 1995 is tested with the are model and root-mean-square errors, to be expected under the given geometrical conditions, are calculated. Although optimum geometry was not used, root-mean-square errors of less than 2% for the images and of the order of 30% for the distribution could be obtained. The method is applied to images from real observations. The correspondence of original pictures and projections of the reconstructed volume is discussed, and emission profiles along magnetic field lines through the three-dimensionally reconstructed arc are calibrated into electron density profiles with additional EISCAT measurements. Including a background profile and the temporal changes of the electron density due to recombination, good agreement can be obtained between measured profiles and the time-sequence of calculated profiles. These profiles are used to estimate the conductivity distribution in the vicinity of the EISCAT site. While the radar can only probe the ionosphere along the radar beam, the three-dimensional tomography enables conductivity estimates in a large area around the radar site.Former address: MPE Garching  相似文献