Volcanic dust veils and climate: How clear is the connection? — An editorial     

Stephen H. Schneider 《Climatic change》1983,5(2):111-113

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Editor’s Note     

Stephen H. Schneider 《Climatic change》2005,69(1):v

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A Distributed Geoprocessing Concept for Enhancing Terrain Analysis for Environmental Modeling     

Bernhardt Schneider  & Daria Martinoni 《Transactions in GIS》2001,5(2):165-178

Geographic Information Systems (GIS) are well suited to support environmental modeling for dealing with space. However, some of the limitations of current GIS are the lack of tools for comprehensive documentation of the models, the inadequate representation of fields, and the deficient methodology for comprehensive management of uncertainty. Using Digital Terrain Modeling and Analysis as an example, this paper proposes an enhanced approach to overcome these drawbacks. It suggests implementing sophisticated functionality for modeling and analysis of fields in special-purpose modules outside monolithic GIS. These modules include three components: (1) an extensive framework for metainformation that allows a sound assessment of the fitness-for-use of digital field representations for environmental modeling applications, (2) an explicit digital representation of the field phenomenon equipped with the appropriate tools for the derivation of data, and (3) the methods to assess the quality of derived data. A standardized interface enables communication between the module and other software components. The presented modular approach combines the functionality of common GIS with highly specialized modeling and analysis tools encapsulating expert knowledge about the represented phenomena.  相似文献   

Element budgets of pine stands on lignite and pyrite containing mine soils     

Martin Gast  Wolfgang Schaaf  Joerg Scherzer  Rudolf Wilden  Bernd U. Schneider  Reinhard F. Hüttl 《Journal of Geochemical Exploration》2001,73(2):196

To analyze the development of pine ecosystems on lignite and pyrite containing mine soils, four pine stands with ages of 3–35 years were investigated in a chronosequence approach. Bulk precipitation, throughfall and soil solution in depths of 20, 40, 70 and 100 cm were studied over a three-year period to determine element fluxes in these forest ecosystems on extreme acidic and saline soils.Element budgets are controlled by the processes induced by pyrite oxidation such as intensive weathering of primary minerals, precipitation and leaching of secondary phases.Despite low water fluxes, element outputs can reach extraordinary high values due to very high concentrations in the soil solution. Although element outputs decrease drastically with stand age, respectively, site age, they exceed those of comparable pine stands on non-mine sites. Nitrogen release from the lignite fraction represents a special characteristic of the examined substrates. Nitrogen losses beneath the rooted zone can be 34 kg N ha⁻¹ yr⁻¹ in 100 cm depth. Element input and output in the examined ecosystems are far from balance. Closed cycling of nutrients seems to be recognizable in the case of potassium.  相似文献   

Metabolism and organic carbon fluxes in the tidal freshwater Hudson River     

R. W. Howarth  R. Schneider  D. Swaney 《Estuaries and Coasts》1996,19(4):848-865

We summarize rates of metabolism and major sources and sinks of organic carbon in the 148-k long, tidally influenced, freshwater Hudson River. The river is strongly heterotrophic, with respiration exceeding gross primary production (GPP). The P:R ration averages 0.57 (defined as the ratio of GPP to total ecosystem respiration) if only the aquatic portion of the ecosystem is considered and 0.70 if the emergent marshes are also included. Gross primary production (GPP) by photoplankton averages approximately 300 g C m^?2 yr^?1 and is an order of magnitude greater than that by submersed macrophytes. However, the river is deep, well mixed, and turbid, and phytoplankton spend a majority of their time in the dark. As a result, respiration by living phytoplankton is extremely high and net primary production (NPP) by phytoplankton is estimated to be only some 6% of GPP. NPP by phytoplankton and submersed macrophytes are roughly equal (approximately 20 g C m^?2 yr^?1 each) when averaged over the river. Emergent marshes are quite productive, but probably less than 16 g C m^?2 yr^?1 enters the aquatic portion of the ecosystem from these marshes. Heterotrophic respiration and secondary production in the river are driven primarily by allochthonous inputs of organic matter from terrestrial sources. Rates of metabolism vary along the river, with depth being a critical controlling factor. The P:R ratio for the aquatic portion of the ecosystem varies from 1 in the mid-river to 0.2 in the deeper waters. NPP is actually negative in the downstream waters where average depths are greater since phytoplankton respiration exceeds GPP there; the positive rates of NPP occurring upriver support a downstream advection of phytoplankton to the deeper waters where this C is largely respired away by the algae themselves. This autotrophic respiration contributes significantly to oxygen depletion in the deeper waters of the Hudson. The tidally influenced freshwater Hudson largely fits the patterns predicted by the river continuum model for larger rivers. However, we suggest that the continuum model needs to more clearly distinguish between GPP and NPP and should include the importance of autotrophic respiration by phytoplankton that are advected along a river. The organic carbon budget for the tidally influenced freshwater Hudson is balanced to within a few percent. Respiration (54%) and downstream advection into the saline estuary (41%) are the major losses of organic carbon from the ecosystem. Allochthonous inputs from nonpoint sources on land (61%) and GPP by phytoplankton (28%) are the major sources to the system. Agricultural erosion is the major source of allochthonous inputs. Since agricultural land use increased dramatically in the last century, and has fallen in this century, the carbon cycle of the tidally influenced freshwater Hudson River has probably changed markedly over time. Before human disturbance, the Hudson was probably a less heterotrophic system and may even have been autotrophic, with gross primary production exceeding ecosystem respiration.  相似文献   

An estimate of late Pleistocene geomagnetic intensity variation from Sulu Sea sediments   总被引：2，自引：0，他引：2  

David A. Schneider 《Earth and Planetary Science Letters》1993,120(3-4):301-310

Sediments from Site 769 of the Ocean Drilling Program's Leg 124 provide a record of geomagnetic intensity variation over the past 110 ky. Using continous shipboard measurements exclusively, I estimate the variation in the geomagnetic field strength by employing low-field magnetic susceptibility as a normalization parameter for the measured remanence intensity. By calibrating the resultant relative paleointensity record against previously available Holocene age estimates of absolute paleointensity, I derive an estimate of virtual dipole moment since 110 ka. The record obtained from these Sulu Sea sediments is strikingly like that previously obtained from sediments of a similar age in the Mediterranean Basin with distinct intervals of low intensity near 15, 20, 40 and 65–70 ka. The Sulu sediments also indicate a low-intensity feature near 108 ka. Important differences in paleointensity estimates obtained from these different regions for the interval between 30 and 20 ka suggest that a relatively large non-dipolar component of the geomagnetic field might have been present at that time.  相似文献   

Die kristallographischen Konstanten Yon Löweit     

Walter Schneider  Prof. Dr. Josef Zemann 《Contributions to Mineralogy and Petrology》1959,6(4):201-202

Zusammenfassung Künstlich hergestellter Löweit kristallisiert trigonal in kleinen Rhomboedern. Die Gitterkonstanten für die hexagonale Zelle sind:a = 18,96 Å,c = 13,47 Å. Die systematischen Auslöschungen führen auf die Raumgruppe R 3 oder R 3. Der Zellinhalt wird diskutiert.  相似文献   

Data processing in biology and geology: CUTBILL,J.L. ed. (1971): Proceedings of a Symposium held at the Department of Geology,University of Cambridge,September 24–26,1969. XV, 346, pp. London: Academic Press. (Published for the systematics association). Cloth, £ 5.00.     

Achim Schneider 《Geoforum》1972,3(2):105-106

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‘The CO2 problem: Are there policy implications — Yet?’ An editorial     

Stephen H. Schneider 《Climatic change》1980,2(3):203-205

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Low-latitude control of interhemispheric sea-surface temperature contrast in the tropical Atlantic over the past 21 kyears: the possible role of SE trade winds     

J.-H. Kim  R. R. Schneider 《Climate Dynamics》2003,21(3-4):337-347

To stimulate a discussion on the role of tropical atmospheric circulation versus thermohaline circulation changes for tropical Atlantic sea-surface temperature (SST) variations, we present a record of the SST contrast (SST) between the tropical northwest and southeast Atlantic from the Last Glacial Maximum to the Late Holocene. The SST was calculated from two alkenone-derived SST records; one from the Caribbean Sea and the other from the Angola Basin. Changes in the cross-equatorial SST were then compared with an abundance record of Florisphaera profunda from the equatorial Atlantic, which is indicative of SE trade-wind induced variations in thermocline depth in the equatorial divergence zone. This comparison implies that the Last Glacial Maximum, the Younger Dryas, and the Mid to Late Holocene were periods of strong SE trade winds, which led to an intense upwelling-related cooling in the southeast Atlantic and concurrently enhanced advection of warm tropical South Atlantic waters into the western tropical Atlantic. Accordingly, a coupled ocean-atmospheric process has probably created a dipole-like SST distribution pattern in the tropical Atlantic during these three distinct climatic periods. In contrast, Heinrich Event 1, the Bølling-Allerød, and the Early Holocene were intervals of weakened SE trade winds, causing a warming in the southeast Atlantic. However, synchronous warming in both regions during Heinrich Event 1 can be partially attributed to a weakening of thermohaline overturning which caused a reduced northward heat transport from the low-latitude to the high-latitude North Atlantic.  相似文献