Palaeogeographic Development of the Rhine–Meuse Delta, The Netherlands. By H. J. A. Berendsen and E. Stouthamer. Koninklijke Van Gorcum, book 268 pp, CD, maps (3). ISBN 90 2323695 5 (pbk). Euro 34.     

Jon D. Trueman 《Sedimentology》2002,49(3):637-638

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Differential responses of zooplankton populations (Bosmina longirostris) to fish predation and nutrient-loading in an introduced and a natural sockeye salmon nursery lake on Kodiak Island, Alaska, USA   总被引：4，自引：0，他引：4  

Jon N. Sweetman  Bruce P. Finney 《Journal of Paleolimnology》2003,30(2):183-193

Stratigraphic changes in the remains of Bosmina longirostris from a lake with an introduced sockeye salmon population and a lake with a natural salmon run on Kodiak Island demonstrated markedly different responses to past fluctuations in salmon populations. In both lakes, there was a positive correlation between the density of Bosmina microfossils and the abundance of sockeye salmon. However, opposite size trends were observed in the two lakes. In Karluk Lake, which has a native sockeye salmon population, Bosmina mean carapace lengths were largest at high salmon densities, and mean mucro and antennule lengths were also large, suggesting strong predation pressure from cyclopoid copepods, and less intense pressure from juvenile sockeye salmon. As salmon-derived nutrients are important in driving primary productivity in this system, changes in zooplankton productivity track salmon escapement, but grazing pressure on Bosmina from juvenile salmon is less important than that from cyclopoid copepods. In Frazer Lake, a lake with an introduced salmon population, Bosmina morphologies were smallest during periods of high sockeye salmon in the lake, suggesting much stronger predation effects from sockeye salmon due to the suppression of Cyclops columbianus. Latent development of compensatory mechanisms and the delayed recovery of copepod populations to salmon introductions has resulted in zooplankton populations that are still recovering from shifts in fish populations that occurred decades earlier. The differential response of Bosmina populations between the natural and manipulated lakes suggests that care must be taken when attempting to extrapolate results from whole-lake manipulations and short-term experiments to natural systems.  相似文献   

The equilibrium form of a rotating earth with an elastic shell     

Jon E. Mound  Jerry X. Mitrovica  Alessandro M. Forte 《Geophysical Journal International》2003,152(1):237-241

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Inter-annual and seasonal variations of energy and water vapour fluxes above a Pinus sylvestris forest in the Siberian middle taiga   总被引：2，自引：0，他引：2  

Nadejda M. Tchebakova  Olaf Kolle  Daniil Zolotoukhine  Almut Arneth  Julie M. Styles  Natalia N. Vygodskaya  E.-Detlef Schulze  Olga Shibistova  Jon Lloyd 《Tellus. Series B, Chemical and physical meteorology》2002,54(5):537-551

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Late Pleistocene Glaciations in the Northwestern Sierra Nevada, California     

L. Allan James  Jon Harbor  Derek Fabel  Dennis Dahms  David Elmore 《Quaternary Research》2002,57(3):409

Pleistocene fluvial landforms and riparian ecosystems in central California responded to climate changes in the Sierra Nevada, yet the glacial history of the western Sierra remains largely unknown. Three glacial stages in the northwestern Sierra Nevada are documented by field mapping and cosmogenic radionuclide surface-exposure (CRSE) ages. Two CRSE ages of erratic boulders on an isolated till above Bear Valley provide a limiting minimum age of 76,400±3800 ¹⁰Be yr. Another boulder age provides a limiting minimum age of 48,800±3200 ¹⁰Be yr for a broad-crested moraine ridge within Bear Valley. Three CRSE ages producing an average age of 18,600±1180 yr were drawn from two boulders near a sharp-crested bouldery lateral moraine that represents an extensive Tioga glaciation in Bear Valley. Nine CRSE ages from striated bedrock along a steep valley transect average 14,100±1500 yr and suggest rapid late-glacial ice retreat from lower Fordyce Canyon with no subsequent extensive glaciations. These ages are generally consistent with glacial and pluvial records in east-central California and Nevada.  相似文献   

The physical environment of Kongsfjorden–Krossfjorden, an Arctic fjord system in Svalbard     

Harald Svendsen  Agnieszka Beszczynska-Møller  Jon Ove Hagen  Bernard Lefauconnier  Vigdis Tverberg  Sebastian Gerland  Jon Børre Ørbøk  Kai Bischof  Carlo Papucci  Marek Zajaczkowski  Roberto Azzolini  Oddbjørn Bruland  Christian Wiencke  Jan-Gunnar Winther  Winfried Dallmann 《Polar research》2002,21(1):133-166

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Modern methods in Structural Geology and Tectonics: a series of articles in honour of Martin Burkhard (1957-2006)     

Stefan M. Schmid  Neil Mancktelow  Jon Mosar  O. Adrian Pfiffner  Jean-Paul Schaer 《Swiss Journal of Geoscience》2008,101(2):245-249

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Which way do you lean? Using slope aspect variations to understand Critical Zone processes and feedbacks   总被引：1，自引：0，他引：1       下载免费PDF全文

Jon D. Pelletier  Greg A. Barron‐Gafford  Hugo Gutiérrez‐Jurado  Eve‐Lyn S. Hinckley  Erkan Istanbulluoglu  Luke A. McGuire  Guo‐Yue Niu  Michael J. Poulos  Craig Rasmussen  Paul Richardson  Tyson L. Swetnam  Greg E. Tucker 《地球表面变化过程与地形》2018,43(5):1133-1154

Soil‐mantled pole‐facing hillslopes on Earth tend to be steeper, wetter, and have more vegetation cover compared with adjacent equator‐facing hillslopes. These and other slope aspect controls are often the consequence of feedbacks among hydrologic, ecologic, pedogenic, and geomorphic processes triggered by spatial variations in mean annual insolation. In this paper we review the state of knowledge on slope aspect controls of Critical Zone (CZ) processes using the latitudinal and elevational dependence of topographic asymmetry as a motivating observation. At relatively low latitudes and elevations, pole‐facing hillslopes tend to be steeper. At higher latitudes and elevations this pattern reverses. We reproduce this pattern using an empirical model based on parsimonious functions of latitude, an aridity index, mean‐annual temperature, and slope gradient. Using this empirical model and the literature as guides, we present a conceptual model for the slope‐aspect‐driven CZ feedbacks that generate asymmetry in water‐limited and temperature‐limited end‐member cases. In this conceptual model the dominant factor driving slope aspect differences at relatively low latitudes and elevations is the difference in mean‐annual soil moisture. The dominant factor at higher latitudes and elevations is temperature limitation on vegetation growth. In water‐limited cases, we propose that higher mean‐annual soil moisture on pole‐facing hillslopes drives higher soil production rates, higher water storage potential, more vegetation cover, faster dust deposition, and lower erosional efficiency in a positive feedback. At higher latitudes and elevations, pole‐facing hillslopes tend to have less vegetation cover, greater erosional efficiency, and gentler slopes, thus reversing the pattern of asymmetry found at lower latitudes and elevations. Our conceptual model emphasizes the linkages among short‐ and long‐timescale processes and across CZ sub‐disciplines; it also points to opportunities to further understand how CZ processes interact. We also demonstrate the importance of paleoclimatic conditions and non‐climatic factors in influencing slope aspect variations. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Relationships between physical‐geochemical soil properties and erodibility of streambanks among different physiographic provinces of Tennessee,USA          下载免费PDF全文

Badal Mahalder  John S. Schwartz  Angelica M. Palomino  Jon Zirkle 《地球表面变化过程与地形》2018,43(2):401-416

Erosion of cohesive soils in fluvial environments is dependent on physical, geochemical and biological properties, which govern inter‐particle attraction forces and control detachment rates from stream beds and banks. Most erosion rate models are based on the excess shear stress equation where the soil erodibility coefficient (k_d) is multiplied by the difference between the boundary hydraulic shear stress (τ_b) and the soil critical shear stress (τ_c). Both k_d and τ_c are a function of soil properties and must be obtained through in situ field or laboratory testing. Many studies have generated predictive relationships for k_d and τ_c derived from various soil properties. These studies typically were conducted in watersheds within a single physiographic region with a common surficial geology and/or investigated a limited number of soil properties, particularly geochemical properties. With widely reported differences in relationships between τ_c and soil properties, this study investigated differences in predictive relationships for τ_c among different physiographic provinces in Tennessee, USA. Erodibility parameters were determined in the field using a mini‐jet test device. Among these provinces, statistically four unique clusters were identified from a dataset of 128 observations and these data clusters were used to develop predictive models for τ_c to identify dominant properties governing erosion. In these clusters, 16 significant physical and geochemical soil properties were identified for τ_c prediction. Among these soil properties, water content and passing #200 sieve (percentage soil less than 75 μm) were the dominant controlling parameters to predict τ_c in addition to clay percentage (< 2 μm), bulk density, and soil pore water chemistry. This study suggests that unique relationships exist for physiographic provinces that are likely due to soil physical‐geochemical processes associated with surficial geology that determine minerology of the cohesive soil. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Asymmetry of weathering‐limited hillslopes: the importance of diurnal covariation in solar insolation and temperature          下载免费PDF全文

Jon D. Pelletier  Tyson L. Swetnam 《地球表面变化过程与地形》2017,42(9):1408-1418

Hillslope asymmetry, i.e. variation in hillslope form as a function of slope aspect and/or mean solar insolation, has been documented in many climates and geologic contexts. Such patterns have the potential to help us better understand the hydrologic, ecologic, and geomorphologic processes and feedbacks operating on hillslopes. Here we document asymmetry in the fraction of hillslope relief accommodated by cliffs in weathering‐limited hillslopes of drainage basins incised into the East Kaibab Monocline (northern Arizona) and Raplee Ridge Monocline (southern Utah) of the southern Colorado Plateau. We document that south‐ and west‐facing hillslopes have a larger proportion of hillslope relief accommodated by cliffs compared with north‐ and east‐facing hillslopes. Cliff abundance correlates positively with mean solar insolation and, by inference, negatively with soil/rock moisture. Solar insolation control of hillslope asymmetry is an incomplete explanation, however, because it cannot account for the fact that the greatest asymmetry occurs between southwest‐ and northeast‐facing hillslopes rather than between south‐ and north‐facing hillslopes in the study sites. Modeling results suggest that southwest‐facing hillslopes are more cliff‐dominated than southeast‐facing hillslopes of the same mean solar insolation in part because potential evapotranspiration rates, which control the soil/rock moisture that drives weathering, are controlled by the product of solar insolation and a nonlinear function of surface temperature, together with the fact that southwest‐facing hillslopes receive peak solar insolation during warmer times of day compared with southeast‐facing hillslopes. The dependence of water availability on both solar insolation and surface temperature highlights the importance of the diurnal cycle in controlling water availability, and it provides a general explanation for the fact that vegetation cover tends to exhibit the greatest difference between northeast‐ and southwest‐facing hillslopes in the Northern Hemisphere and between southeast‐ and northwest‐facing hillslopes in the Southern Hemisphere. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献