Modelling mean annual sediment yield using a distributed approach   总被引：3，自引：0，他引：3  

Anton J. J. Van Rompaey  Gert Verstraeten  Kristof Van Oost  Gerard Govers  Jean Poesen 《地球表面变化过程与地形》2001,26(11):1221-1236

In this paper a spatially distributed model for the calculation of sediment delivery to river channels is presented (SEDEM: SEdiment DElivery Model). The model consists of two components: (1) the calculation of a spatial pattern of mean annual soil erosion rates in the catchment using a RUSLE (Revised Soil Erosion Equation) approach; and (2) the routing of the eroded sediment to the river channel network taking into account the transport capacity of each spatial unit. If the amount of routed sediment exceeds the local transport capacity, sediment deposition occurs. An existing dataset on sediment yield for 24 catchments in central Belgium was used to calibrate the transport capacity parameters of the model. A validation of the model results shows that the sediment yield for small and medium sized catchments (10–5000 ha) can be predicted with an average accuracy of 41 per cent. The predicted sediment yield values with SEDEM are significantly more accurate than the predictions using a lumped regression model. Moreover a spatially distributed approach allows simulation of the effect of different land use scenarios and soil conservation techniques. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Transmission electron microscope study of experimentally deformed K-Feldspar single crystals     

M. P. Kovacs  M. Gandais 《Physics and Chemistry of Minerals》1980,6(1):61-76

Single crystals of sanidine which were experimentally deformed so as to introduce the (010)[100] slip system were examined by transmission electron microscopy (tem). Dislocation glide is mainly manifested in the samples deformed at 700° C, with a strain rate \(\dot \varepsilon = 1 - 2 \times 10^{ - 6} s^{ - 1} \) . In addition to the expected slip system another more important one, (12 \(\bar 1\) )[101], was found. The dislocations lying in (010) present a glissile dissociation. These observations have been discussed in term of the feldspar structure. Models for glissile dissociation in (010) are proposed: [100]=1/2[100]+1/2[100] or 1/2[101]+1/2[10 \(\bar 1\) ] and [101]=1/2[101]+1/2[101].  相似文献   

Delineating salt-affected soils in the ganges plain by digital analysis of landsat data   总被引：1，自引：0，他引：1  

A. N. Singh  S. J. Kristof  M. F. Baumgardner 《Journal of the Indian Society of Remote Sensing》1979,7(1):35-39

A study has been conducted to determine the feasibility of delineating salt-affected soils using computer-aided analysis of Landsat-1 data in an area of the Ganges Plain. The multispectral scanner data have been obtained on 2nd December 1972 Landsat pass. Both supervised and unsupervised classification techniques are used. Four spectral classes of salt-affected soils have been separated. The results indicate that Landsat data can be successfully used for differentiating salt-affected soils.  相似文献   

Seafloor spreading in the Weddell Sea from magnetic and gravity data     

L. C. Kovacs  P. Morris  J. Brozena  A. Tikku   《Tectonophysics》2002,347(1-3)

A re-compilation of magnetic data in the Weddell Sea is presented and compared with the gravity field recently derived from retracked satellite altimetry. The previously informally named ‘Anomaly-T,’ an east–west trending linear positive magnetic and gravity anomaly lying at about 69°S, forms the southern boundary of the well-known Weddell Sea gravity herringbone. North of Anomaly-T, three major E–W linear magnetic lows are shown, and identified with anomalies c12r, c21–29(r) and c33r. On the basis of these, and following work by recent investigators, isochrons c13, c18, c20, c21, c30, c33 and c34 are identified and extended into the western Weddell Sea. Similarly, a linear magnetic low lying along the spine of the herringbone is shown and provisionally dated at 93–96 Ma. Anomaly-T is tentatively dated to be M5n, in agreement with recent tectonic models.Although current tectonic models are generally in good agreement to the north of T, to the south interpretations differ. Some plate tectonic models have only proposed essentially north–south spreading in the region, whilst others have suggested that a period of predominantly east–west motion (relative to present Antarctic geographic coordinates) occurred during the mid-Mesozoic spreading between East and West Gondwana. We identify an area immediately to the south of T which appears to be the southerly extent of N–S spreading in the herringbone. Following recent work, the extreme southerly extent of the N–S directed spreading of the herringbone is provisionally dated M9r/M10. In the oldest Weddell Sea, immediately to the north and east of the Antarctic shelf, we see subtle features in both the magnetic and gravity data that are consistent with predominantly N–S spreading in the Weddell Sea during the earliest opening of East and West Gondwana. In between, however, in a small region extending approximately from about 50 km south of T to about 70°S and from approximately 40° to 53°W, the magnetic and gravity data appear to suggest well-correlated linear marine magnetic anomalies (possible isochrons) perpendicular to T, bounded and offset by less well-defined steps and linear lows in the gravity (possible fracture zones). These magnetic and gravity data southwest of T suggest that the crust here may record an E–W spreading episode between the two-plate system of East and West Gondwana prior to the initiation of the three-plate spreading system of South America, Africa and Antarctica. The E–W spreading record to the east of about 35°W would then appear to have been cut off at about M10 time during the establishment of N–S three-plate spreading along the South American–Antarctic Ridge and then subducted under the Scotia Ridge.  相似文献   

Role of eicosenoic and docosenoic fatty acids in fresh water and marine lipids     

R.G. Ackman  J-L. Sebedio  M.I.P. Kovacs 《Marine Chemistry》1980,9(3):157-164

The isomeric compositions of the eicosenoic and docosenoic fatty acids of four freshwater fish oils (from sheepshead Aplodinotus grunniens, tullibee Coregonus artedii, maria Lota lota and alewife Alosa pseudoharengus, respectively) were examined by open-tubular gas—liquid chromatography. The 22:1ω11 isomer, usually the dominant isomer in marine-fish oils, was unimportant relative to 22:1ω9. The unsaponifiables lacked fatty alcohols and pristane and were mostly cholesterol. The probability that the 22:1ω1 in marine fish oils is strictly of an exogenous origin (primarily originating as the fatty alcohol in copepod wax esters) is reviewed and it is proposed that docosenoic acids have no obligatory role in the lipid biochemistry of either marine or freshwater fish.  相似文献   

Characterizing rainfall‐runoff signatures from micro‐catchments with contrasting land cover characteristics in southern Amazonia          下载免费PDF全文

Alphonce C. Guzha  Rodolfo L. B. Nobrega  Kristof Kovacs  Jessica Rebola‐Lichtenberg  Ricardo S. S. Amorim  Gerhard Gerold 《水文研究》2015,29(4):508-521

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Comment on Watanabe et al. (2009)     

Ruth H. Carmichael  Carolyn J. Kovacs 《Marine pollution bulletin》2010,60(2):314-680

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The compatibility of erosion data at different temporal scales     

Iris Peeters  Kristof Van Oost  Gerard Govers  Gert Verstraeten  Tom Rommens  Jean Poesen 《Earth and Planetary Science Letters》2008,265(1-2):138-152

Soil erosion processes have been studied intensively throughout the last decades and rates have been measured at the plot scale as well as at larger scales. However, the relevance of this knowledge for the modelling of long-term landscape evolution remains a topic of considerable debate. Some authors state that measurements of current rates are irrelevant to landscape evolution over a longer time span, as they are inconsistent with some fundamental characteristics of landscapes, such as the fact that the long-term sediment delivery ratio needs to be equal to 1 and that extrapolation of current rates would imply that all soils in Europe should have disappeared by now (e.g. Parsons, A.J., Wainwright, J., Brazier, R.E., Powell, D.M., 2006. Is sediment delivery a fallacy? Earth Surface Processes and Landforms 31, 1325–1328). In this study, we investigate if and to what extent estimates of long-term erosion rates are consistent with information obtained over much shorter time spans for the Loam Belt of Belgium.In a first step, observed short-term and long-term patterns in the Belgian loess area are compared statistically by classifying the study area into landscape element classes and comparing average erosion values per class. This analysis shows that the erosion intensities on the two temporal scales are of the same order of magnitude for each landscape element class. Next, the spatially distributed model WaTEM LT (Water and Tillage Erosion Model Long Term) is calibrated based on the available short-term data by optimising average erosion values for the same landscape element classes. Finally, the calibrated model is used to simulate long-term landform evolution, and is validated using long-term data based on soil profile truncation. We found that the model allows simulating landscape evolution on a millennial time scale using information derived from short-term erosion and deposition data. However, it is important that land use is taken into account for the calibration in order to obtain realistic patterns on a longer time scale. Our analysis shows that, at least for the study area considered, data obtained on erosion and deposition rates over various temporal scales have the same orders of magnitude, thereby demonstrating that measurements of current rates of processes can be highly relevant for interpreting long-term landscape evolution.  相似文献   

Evaluating the impact of soil redistribution on the in situ mineralization of soil organic carbon     

Hendrik Van Hemelryck  Gerard Govers  Kristof Van Oost  Roel Merckx 《地球表面变化过程与地形》2011,36(4):427-438

Soil erosion, transport and deposition by water drastically affect the distribution of soil organic carbon (SOC) within a landscape. Moreover, soil redistribution may have a large impact on the exchange of carbon (C) between the pedosphere and the atmosphere. One of the large information gaps within this research domain, concerns the fate of SOC after erosion by water. According to different (mainly laboratory) studies, soil redistribution leads to aggregate breakdown, thereby exposing the contained SOC to mineralization. Our study aims to quantify the extent to which such increased mineralization occurs in a real field situation. Carbon dioxide (CO₂)‐efflux was measured in the field after an important erosion event for a continuous period of 112 days. The specific situation on the field ensured that almost none of eroded SOC was exported from the field. Measurements of CO₂‐efflux were done in areas with sediment deposition, as well as in comparable areas without sedimentation. Comparison of these measurements allowed the net effect of soil deposition on CO₂‐efflux to be assessed. Field data were complemented by measurements on incubated, undisturbed soil core samples, in order to disentangle the contribution of environmental factors (moisture, temperature) from any erosional effect on CO₂‐efflux. Results of these measurements on the field showed that CO₂‐efflux was regulated by a complex interplay of different factors (mostly soil porosity, soil moisture and soil temperature). In combination with the incubation measurements, it could be concluded that the processes of erosion and transport indeed led to an increased mineralization of SOC, as a result of aggregate breakdown and exposure of previously encapsulated SOC. This effect was, however, much smaller than observed in previous laboratory studies. Moreover, it was only important in the first weeks, immediately after the erosion event. The calculated net erosional effect on CO₂‐efflux represented a mere 1·6% of total SOC, originally present in the soil. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Matching INSPIRE Quality of Service Requirements with Hybrid Clouds     

Bastian Baranski  Theodor Foerster  Bastian Schäffer  Kristof Lange 《Transactions in GIS》2011,15(Z1):125-142

A lot of effort has been invested in Spatial Data Infrastructures (SDIs) during the last decade regarding interoperable standards for services and data. But still the scalability and performance of SDI services is reported to be crucial especially if they are accessed concurrently by a high number of users. Furthermore, laws and provisions such as the INSPIRE directive specify challenging requirements regarding the performance, availability and scalability of SDI services. This article presents a Hybrid Cloud architecture for matching INSPIRE‐related Quality of Service (QoS) requirements, without investing in rarely used hardware in advance, by occupying external third‐party resources on a pay‐as‐you‐go basis. The presented Hybrid Cloud is a composition of a local IT‐infrastructure (Private Cloud) and the computational resources of third‐party vendors (Public Cloud). The local infrastructure is laid out to handle the average main load of a service and in lasting peak times additional resources of external providers are allocated and integrated on demand into the local infrastructure to provide sufficient service quality automatically. A proof‐of‐concept implementation of the proposed Hybrid Cloud approach is evaluated and benchmarked with respect to INSPIRE‐related QoS requirements.  相似文献