A comparison of predictive methods in modelling the distribution of periglacial landforms in Finnish Lapland     

Mathieu Marmion  Jan Hjort  Wilfried Thuiller  Miska Luoto 《地球表面变化过程与地形》2008,33(14):2241-2254

This study compares the predictive accuracy of eight state‐of‐the‐art modelling techniques for 12 landforms types in a cold environment. The methods used are Random Forest (RF), Artificial Neural Networks (ANN), Generalized Boosting Methods (GBM), Generalized Linear Models (GLM), Generalized Additive Models (GAM), Multivariate Adaptive Regression Splines (MARS), Classification Tree Analysis (CTA) and Mixture Discriminant Analysis (MDA). The spatial distributions of 12 periglacial landforms types were recorded in sub‐Arctic landscape of northern Finland in 2032 grid squares at a resolution of 25 ha. First, three topographic variables were implemented into the eight modelling techniques (simple model), and then six other variables were added (three soil and three vegetation variables; complex model) to reflect the environmental conditions of each grid square. The predictive accuracy was measured by two methods: the area under the curve (AUC) of a receiver operating characteristic (ROC) plot, and the Kappa index (κ), based on spatially independent model evaluation data. The mean AUC values of the simple models varied between 0·709 and 0·796, whereas the AUC values of the complex model ranged from 0·725 to 0·825. For both simple and complex models GAM, GLM, ANN and GBM provided the highest predictive performances based on both AUC and κ values. The results encourage further applications of the novel modelling methods in geomorphology. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Development of a Field Preconcentration/Elution Unit for Routine Determination of Dissolved Metal Concentrations by ICP-OES in Marine Waters: Application for Monitoring of the New Caledonia Lagoon     

Benjamin M. Moreton  Jean-Michel Fernandez  Mathieu B.D. Dolbecq 《Geostandards and Geoanalytical Research》2009,33(2):205-218

An iminodiacetate chelating resin was optimised for the rapid determination of Co, Cu, Fe, Mn and Ni in seawater. Using inexpensive, high-capacity, reusable cartridges allowed high flow rates of up to 25 ml min⁻¹. High preconcentration factors, of up to 500, were obtained in order to analyse samples using an ICP-OES. The requirement for a buffer was eliminated due to the high tolerance of the ICP-OES to interfering matrix elements, thereby further reducing the potential for contamination. Quantification limits in seawater were: Co = 6 ng l⁻¹, Cu = 8 ng l⁻¹, Fe = 6 ng l⁻¹, Mn = 5 ng l⁻¹ and Ni = 6 ng l⁻¹. The method was verified by the analysis of near shore seawater (CASS-4) and open ocean seawater (NASS-5) reference materials. In order to satisfy the high sampling demands using the iminodiacetate cartridges, a portable off-line preconcentration unit was developed for routine analysis. The multi-channel preconcentration unit, was capable of treating up to eight samples simultaneously with concentrating times as little as 30 minutes. The technique was also used to determine dissolved metals in fresh and interstitial waters. The technique has been successfully used in a number of environmental studies and impact assessments to evaluate the effects of mining on the New Caledonian lagoon.  相似文献   

Stepwise palaeoclimate change across the Eocene–Oligocene transition recorded in continental NW Europe by mineralogical assemblages and δ15Norg (Rennes Basin,France)          下载免费PDF全文

Romain Tramoy  Marie Salpin  Johann Schnyder  Alain Person  Mathieu Sebilo  Johan Yans  Véronique Vaury  Jérôme Fozzani  Hugues Bauer 《地学学报》2016,28(3):212-220

The Eocene–Oligocene transition (EOT, ~34 Ma) is the largest global cooling of the Cenozoic Era and led the Earth's climatic system to change from a greenhouse to an icehouse mode. Although it is well documented in marine settings, the few studies focusing on continental environments have demonstrated regional heterogeneities. The study core CDB1, located in the Rennes Basin (Western France), is a unique terrestrial (lacustrine–palustrine) record comprising well‐preserved and terrestrial‐derived organic‐rich sediments encompassing the EOT. Clay minerals and the first organic nitrogen isotope record (δ¹⁵N_org) of terrestrial origin for this period are used to reconstruct palaeoclimate changes across this key interval. As suggested in worldwide marine and a few continental records, a stepwise transition from warm/humid conditions in the Late Eocene to cooler/drier conditions in the Early Oligocene is confirmed in the area. In addition, an episode of drier conditions in the Late Eocene and humid/dry cycles in the Early Oligocene are suggested.  相似文献   

Thermal‐infrared remote sensing of surface water–groundwater exchanges in a restored anastomosing channel (Upper Rhine River,France)          下载免费PDF全文

David Eschbach  Guillaume Piasny  Laurent Schmitt  Laurent Pfister  Pierre Grussenmeyer  Mathieu Koehl  Grzegorz Skupinski  Abdelaziz Serradj 《水文研究》2017,31(5):1113-1124

Ecohydrological processes are a key element to consider in functional river restorations. In the framework of a LIFE+ European restoration program, we have investigated the potential for airborne thermal‐infrared remote sensing to map surface water–groundwater exchanges and to identify their driving factors. We focused our attention on anastomosing channels on an artificial island of the Upper Rhine River (Rohrschollen), where a new channel was excavated from the floodplain to reconnect an older channel in its upstream part. These hydraulic engineering works led to an increased inflow from the Rhine Canal. Here, we propose an original data treatment chain to (a) georeference the thermal‐infrared images in geographic information system based on visible images, (b) detect and correct data errors, and (c) identify and locate thermal anomalies attributed to groundwater inputs and hyporheic upwellings. Our results, which have been compared to morpho‐sedimentary data, show that groundwater upwelling in the new channel is controlled by riffle–pool sequences and bars. This channel is characterized by large bedload transport and morphodynamic activity, forming riffles and bars. In the old channel, where riffle–pool sequences no longer exist, due to impacts of engineering works and insufficient morphodynamic effects of the restoration, thermal anomalies appeared to be less pronounced. Groundwater inputs seem to be controlled by former gravel bars outcropping on the banks, as well as by local thinning of the low‐permeability clogging layer on the channel bed.  相似文献   

The impact of ENSO on Southern African rainfall in CMIP5 ocean atmosphere coupled climate models     

Bastien Dieppois  Mathieu Rouault  Mark New 《Climate Dynamics》2015,45(9-10):2425-2442

  相似文献   

A graph-based approach for the structural analysis of road and building layouts     

Mathieu Domingo  Christophe Claramunt 《地球空间信息科学学报》2019,22(1):59-72

A better understanding of the relationship between the structure and functions of urban and suburban spaces is one of the avenues of research still open for geographical information science. The research presented in this paper develops several graph-based metrics whose objective is to characterize some local and global structural properties that reflect the way the overall building layout can be cross-related to the one of the road layout. Such structural properties are modeled as an aggregation of parcels, buildings, and road networks. We introduce several computational measures (Ratio Minimum Distance, Minimum Ratio Minimum Distance, and Metric Compactness) that respectively evaluate the capability for a given road to be connected with the whole road network. These measures reveal emerging sub-network structures and point out differences between less-connective and more-connective parts of the network. Based on these local and global properties derived from the topological and graph-based representation, and on building density metrics, this paper proposes an analysis of road and building layouts at different levels of granularity. The metrics developed are applied to a case study in which the derived properties reveal coherent as well as incoherent neighborhoods that illustrate the potential of the approach and the way buildings and roads can be relatively connected in a given urban environment. Overall, and by integrating the parcels and buildings layouts, this approach complements other previous and related works that mainly retain the configurational structure of the urban network as well as morphological studies whose focus is generally limited to the analysis of the building layout.  相似文献   

Changes in large-scale controls of Atlantic tropical cyclone activity with the phases of the Atlantic multidecadal oscillation     

Louis-Philippe Caron  Mathieu Boudreault  Cindy L. Bruyère 《Climate Dynamics》2015,44(7-8):1801-1821

  相似文献   

The field and remote sensing analysis of the Kerguelen Archipelago structure,Indian Ocean     

Lucie Mathieu  Paul Byrne  Damien Guillaume  Benjamin van Wyk de Vries  Bertrand Moine 《Journal of Volcanology and Geothermal Research》2011,199(3-4):206-215

The Kerguelen Archipelago is part of an oceanic plateau with a complex history. Little work has been done on the tectonics of the onshore areas, even though the extensive outcrop renders the islands especially good for structural work. We present the results of three field campaigns and remote sensing analysis carried out in the main Kerguelen Island, around Val Travers valley and Mt Ross volcano (Central Plateau) and in the Rallier du Baty peninsula (SW part of the archipelago). We have mapped faults, fracture sets, and the location and geometry of intrusive bodies. We found that the plateau basalt lavas that make up most of the area are densely fractured, crossed by many veins, dykes and some small faults. This work provides a general framework for the structure of Kerguelen Archipelago that is dominated by 110°-striking faults and veins, dyke swarms and an alignment of recent central volcanoes, which have formed in N-S to NNW-SSE directed extensional stress field. The other structures are fractures, veins and dykes which strike 130–150°, 000° and 030–050°. They are likely related to transform faults of the Indian oceanic crust and to faults of the north Kerguelen Plateau (offshore basement of the archipelago). These buried structures were likely re-activated by a low magnitude stress field.  相似文献   

Mineralogy, geochemistry and petrogenesis of the recent magmatic formations from Mbengwi, a continental sector of the Cameroon Volcanic Line (CVL), Central Africa     

Beno?t Joseph Mbassa  Emmanuel Njonfang  Mathieu Benoit  Pierre Kamgang  Michel Grégoire  Stephanie Duchene  Pierre Brunet  Bekoa Ateba  Félix M. Tchoua 《Mineralogy and Petrology》2012,106(3-4):217-242

The Mbengwi recent magmatic formations consist of volcanics and syenites belonging to the same magmatic episode. Lavas form a bimodal basanite-rhyolite alkaline series with a gap between 50 and 62?wt.% SiO₂. Mafic lavas (basanite-hawaiite) are sodic while felsic rocks (trachyte-rhyolite-syenites) are sodi-potassic, slightly metaluminous to peralkaline. The geochemical and isotopic characteristics (0.7031?<?(⁸⁷Sr/⁸⁶Sr)_initial?<?0.7043; 1.03?<?ε_Ndi?<?5.17) of these rocks are similar to those of other rocks from the CVL. The main differentiation process is fractional crystallization with two trends of fractionation. Their Rb/Sr isochron age of 28.2?Ma, almost similar to 27.40?±?0.6?Ma?K/Ar age obtained in a trachyte from neighboring Bamenda Mountains system, precludes any local age migration of an hypothetic hotspot. Mafic lavas have OIB features displaying an isotopic signature similar to that of HIMU mantle source different from FOZO known as source of most parental magmas along the CVL.  相似文献   

Influence of species and rain event characteristics on stemflow volume in a temperate mixed oak–beech stand     

Frédéric André  Mathieu Jonard  Quentin Ponette 《水文研究》2008,22(22):4455-4466

This study aimed at analysing the effects of biological and meteorological factors on stemflow generation in a temperate mixed oak (Quercus petraea Liebl.) and beech (Fagus sylvatica L.) stand. A statistical model was developed to predict single‐event individual stemflow volume from trunk circumference and rainfall depth allowing mechanistic stemflow parameters to be deduced from the model, namely stemflow rates (SF_rate), storage of water on tree organs (S_t) and rainfall thresholds for stemflow (RF_min). SF_rate and S_t increased with increasing trunk circumference while RF_min was not significantly influenced by tree size. RF_min and, for a given tree size, S_t were higher for oak than for beech, and inversely for SF_rate. For each species, RF_min was higher for the leaved season than for the leafless period, while the opposite was found for SF_rate, and S_t was not significantly affected by the season. Increasing wind speed during rain increased SF_rate, lowered RF_min and did not influence S_t. In contrast, S_t and RF_min tended, respectively, to decrease and to increase with increasing values of the ratio between the cumulated potential evaporation during the dry period preceding the rain event and the volume of the preceding rainfall (Eva p_ADP/R_previous). Stemflow volume, which results from the combined effects of the previous parameters, was higher for beech than for oak and also higher during the leafless period than during the leaved period; these differences were large for the smallest events but decreased rapidly as rainfall depth increased. In addition, an enhancing and a depressing effect on stemflow volume were shown for the average wind speed during rain and for the ratio Eva p_ADP/R_previous, respectively. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献