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101.
Alessandra Musso Michael E. Ketterer Konrad Greinwald Clemens Geitner Markus Egli 《地球表面变化过程与地形》2020,45(12):2824-2839
High mountainous areas are geomorphologically active environments which are strongly shaped by redistribution of sediments and soils. With the projected climate warming in the twenty-first century and the continued retreat of glaciers, the area of newly exposed, highly erodible sediments and soils will increase. This presents a need to better understand and quantify erosion processes in young mountainous soils, as an increase in erodibility could threaten human infrastructure (i.e. hydroelectric power, tourist installations and settlements). While soil development is increasingly well understood and quantified, a coupling to soil erosion rates is still missing. The aim of this study was, therefore, to assess how soil erosion rates change with surface age. We investigated two moraine chronosequences in the Swiss Alps: one in the siliceous periglacial area of Steingletscher (Sustenpass), with soils ranging from 30 a to 10 ka, and the other in the calcareous periglacial area of Griessgletscher (Klausenpass) with surfaces ranging from age of 110 a to 13.5 ka. We quantified the erosion rates using the 239+240Pu fallout radionuclides and compared them to physical and chemical soil properties and the vegetation coverage. We found no significant differences between the two parent materials. At both chronosequences, the erosion rates were highest in the young soils (on average 5−10 t ha-1 a-1 soil loss). Erosion rates decreased markedly after 3−5 ka of soil development (on average 1−2.5 t ha-1 a-1 soil loss) to reach a more or less stable situation after 10−14 ka (on average 0.3–2 t ha-1 a-1). Climate change not only causes glacier retreat, but also increased sediment dynamics. Depending on the relief and vegetational development, it takes up to at least 10 ka to reach soil stability. The establishment of a closed vegetation cover with dense root networks seems to be the controlling factor in the reduction of soil erodibility. © 2020 John Wiley & Sons, Ltd. 相似文献
102.
GPCC's new land surface precipitation climatology based on quality-controlled in situ data and its role in quantifying the global water cycle 总被引:10,自引:3,他引:10
Udo Schneider Andreas Becker Peter Finger Anja Meyer-Christoffer Markus Ziese Bruno Rudolf 《Theoretical and Applied Climatology》2014,115(1-2):15-40
In 1989, the need for reliable gridded land surface precipitation data sets, in view of the large uncertainties in the assessment of the global energy and water cycle, has led to the establishment of the Global Precipitation Climatology Centre (GPCC) at Deutscher Wetterdienst on invitation of the WMO. The GPCC has calculated a precipitation climatology for the global land areas for the target period 1951–2000 by objective analysis of climatological normals of about 67,200 rain gauge stations from its data base. GPCC's new precipitation climatology is compared to several other station-based precipitation climatologies as well as to precipitation climatologies derived from the GPCP V2.2 data set and from ECMWF's model reanalyses ERA-40 and ERA-Interim. Finally, how GPCC's best estimate for terrestrial mean precipitation derived from the precipitation climatology of 786 mm per year (equivalent to a water transport of 117,000 km3) is fitting into the global water cycle context is discussed. 相似文献
103.
This ethnoarchaeological study at the Q'eqchi' Maya village of Las Pozas, Guatemala, aimed to refine the understanding of the relationship between soil chemical signatures and human activities for archaeological applications. The research involved phosphorus, exchangeable ion (calcium, potassium, magnesium, sodium), and trace element analysis of soils and earth floors extracted by Mehlich II, ammonium acetate, and DTPA chelate solutions, respectively. The results showed high levels of phosphorus, potassium, magnesium, and pH in food preparation areas, as well as high phosphorus concentrations and low pH in food consumption areas. The traffic areas exhibited low phosphorus and trace element contents, whereas refuse disposal areas were enriched. These results provide important information for the understanding of space use in ancient settlements. © 2002 Wiley Periodicals, Inc. 相似文献
104.
Thomas A. Anderson Erick A. Bestland Lesja Soloninka Ilka Wallis Edward W. Banks Markus Pichler 《Hydrogeology Journal》2017,25(8):2435-2451
High and variable levels of salinity were investigated in an intermittent stream in a high-rainfall area (~800 mm/year) of the Mt. Lofty Ranges of South Australia. The groundwater system was found to have a local, upslope saline lens, referred to here as a groundwater salinity ‘hotspot’. Environmental tracer analyses (δ18O, δ2H, 87/86Sr, and major elements) of water from the intermittent stream, a nearby permanent stream, shallow and deep groundwater, and soil-water/runoff demonstrate seasonal groundwater input of very saline composition into the intermittent stream. This input results in large salinity increases of the stream water because the winter wet-season stream flow decreases during spring in this Mediterranean climate. Furthermore, strontium and water isotope analyses demonstrate: (1) the upslope-saline-groundwater zone (hotspot) mixes with the dominant groundwater system, (2) the intermittent-stream water is a mixture of soil-water/runoff and the upslope saline groundwater, and (3) the upslope-saline-groundwater zone results from the flushing of unsaturated-zone salts from the thick clayey regolith and soil which overlie the metamorphosed shale bedrock. The preferred theory on the origin of the upslope-saline-groundwater hotspot is land clearing of native deep-rooted woodland, followed by flushing of accumulated salts from the unsaturated zone due to increased recharge. This cause of elevated groundwater and surface-water salinity, if correct, could be widespread in Mt. Lofty Ranges areas, as well as other climatically and geologically similar areas with comparable hydrogeologic conditions. 相似文献
105.
Markus Wallner Georg Houben Christoph Lohe Martin Quinger Thomas Himmelsbach 《Hydrogeology Journal》2017,25(8):2303-2321
The identification of potential recharge areas and estimation of recharge rates to the confined semi-fossil Ohangwena II Aquifer (KOH-2) is crucial for its future sustainable use. The KOH-2 is located within the endorheic transboundary Cuvelai-Etosha-Basin (CEB), shared by Angola and Namibia. The main objective was the development of a strategy to tackle the problem of data scarcity, which is a well-known problem in semi-arid regions. In a first step, conceptual geological cross sections were created to illustrate the possible geological setting of the system. Furthermore, groundwater travel times were estimated by simple hydraulic calculations. A two-dimensional numerical groundwater model was set up to analyze flow patterns and potential recharge zones. The model was optimized against local observations of hydraulic heads and groundwater age. The sensitivity of the model against different boundary conditions and internal structures was tested. Parameter uncertainty and recharge rates were estimated. Results indicate that groundwater recharge to the KOH-2 mainly occurs from the Angolan Highlands in the northeastern part of the CEB. The sensitivity of the groundwater model to different internal structures is relatively small in comparison to changing boundary conditions in the form of influent or effluent streams. Uncertainty analysis underlined previous results, indicating groundwater recharge originating from the Angolan Highlands. The estimated recharge rates are less than 1% of mean yearly precipitation, which are reasonable for semi-arid regions. 相似文献
106.
We have examined the influence of impact angle in collisions between small dust aggregates and larger dust targets through laboratory experiments. Targets consisted of μm-sized quartz dust and had a porosity of about 67%; the projectiles, between 1 and 5 mm in diameter, were slightly more compact (64% porosity). The collision velocity was centered at 20 m/s and impact angles range from 0° to 45°. At a given impact angle, the target gained mass for projectiles smaller than a threshold size, which decreases with increasing angle from about 3 mm to 1 mm. The fact that growth is possible up to the largest angles studied supports the idea of planetesimal formation by sweep-up of small dust aggregates. 相似文献
107.
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109.
Exploring large wood retention and deposition in contrasting river morphologies linking numerical modelling and field observations 下载免费PDF全文
Virginia Ruiz‐Villanueva Bartłomiej Wyżga Hanna Hajdukiewicz Markus Stoffel 《地球表面变化过程与地形》2016,41(4):446-459
Large wood tends to be deposited in specific geomorphic units within rivers. Nevertheless, predicting the spatial distribution of wood deposits once wood enters a river is still difficult because of the inherent complexity of its dynamics. In addition, the lack of long‐term observations or monitored sites has usually resulted in a rather incomplete understanding of the main factors controlling wood deposition under natural conditions. In this study, the deposition of large wood was investigated in the Czarny Dunajec River, Polish Carpathians, by linking numerical modelling and field observations so as to identify the main factors influencing wood retention in rivers. Results show that wood retention capacity is higher in unmanaged multi‐thread channels than in channelized, single‐thread reaches. We also identify preferential sites for wood deposition based on the probability of deposition under different flood scenarios, and observe different deposition patterns depending on the geomorphic configuration of the study reach. In addition, results indicate that wood is not always deposited in the geomorphic units with the highest roughness, except for low‐magnitude floods. We conclude that wood deposition is controlled by flood magnitude and the elevation of flooded surfaces in relation to the low‐flow water surface. In that sense, the elevation at which wood is deposited in rivers will differ between floods of different magnitude. Therefore, together with the morphology, flood magnitude represents the most significant control on wood deposition in mountain rivers wider than the height of riparian trees. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
110.
Patrik Krebs Markus Stocker Gianni Boris Pezzatti Marco Conedera 《International journal of geographical information science》2013,27(4):643-666
Terrain curvature is one of the most important parameters of land surface topography. Well-established methods used in its measurement compute an index of plan or profile curvature for every single cell of a digital elevation model (DEM). The interpretation of these outputs may be delicate, especially when selected locations have to be analyzed. Furthermore, they involve a high level of simplification, contrasting with the complex and multiscalar nature of the surface curvature itself. In this paper, we present a new method to assess vertical transverse and profile curvature combining real-scale visualization and the possibility to measure these two terrain derivatives over a large range of scales. To this purpose, we implemented a GIS tool that extracts longitudinal and transverse elevation profiles from a high-resolution DEM. The performance of our approach was compared with some of the most commonly used methods (ArcMap, Redlands, CA, USA; ArcSIE, Landserf) by analyzing the terrain curvature around charcoal production sites in southern Switzerland. The different methods produced comparable results. While conventional methods quickly summarize terrain curvature in the form of a matrix of values, they involve a loss of information. The advantage of the new method lies in the possibility to measure and visualize the shape and size of the curvature, and to obtain a realistic representation of the average curvature for different subsets of spatial points. Moreover, the new method makes it possible to control the conditions in which the index of curvature is calculated. 相似文献