The information system of the French Peatland Observation Service: Service National d'Observation Tourbières – A valuable tool to assess the impact of global changes on the hydrology and biogeochemistry of temperate peatlands through long term monitoring     

Sébastien Gogo  Jean-Baptiste Paroissien  Fatima Laggoun-Défarge  Jean-Marc Antoine  Léonard Bernard-Jannin  Guillaume Bertrand  Philippe Binet  Stéphane Binet  Guillaume Bouger  Yohann Brossard  Thierry Camboulive  Jean-Pierre Caudal  Stéphane Chevrier  Geneviève Chiapiuso  Benoît D'Angelo  Pilar Durantez  Chris Flechard  André-Jean Francez  Didier Galop  Laure Gandois  Daniel Gilbert  Christophe Guimbaud  Louis Hinault  Adrien Jacotot  Franck Le Moing  Emilie Lerigoleur  Gaël Le Roux  Fabien Leroy  Alexandre Lhosmot  Qian Li  Elodie Machado Da Silva  Jean-Sébastien Moquet  Juanita Mora-Gomez  Laurent Perdereau  Thomas Rosset  Marie-Laure Toussaint 《水文研究》2021,35(6):e14244

Mitigating and adapting to global changes requires a better understanding of the response of the Biosphere to these environmental variations. Human disturbances and their effects act in the long term (decades to centuries) and consequently, a similar time frame is needed to fully understand the hydrological and biogeochemical functioning of a natural system. To this end, the ‘Centre National de la Recherche Scientifique’ (CNRS) promotes and certifies long-term monitoring tools called national observation services or ‘Service National d'Observation’ (SNO) in a large range of hydrological and biogeochemical systems (e.g., cryosphere, catchments, aquifers). The SNO investigating peatlands, the SNO ‘Tourbières’, was certified in 2011 ( https://www.sno-tourbieres.cnrs.fr/ ). Peatlands are mostly found in the high latitudes of the northern hemisphere and French peatlands are located in the southern part of this area. Thus, they are located in environmental conditions that will occur in northern peatlands in coming decades or centuries and can be considered as sentinels. The SNO Tourbières is composed of four peatlands: La Guette (lowland central France), Landemarais (lowland oceanic western France), Frasne (upland continental eastern France) and Bernadouze (upland southern France). Thirty target variables are monitored to study the hydrological and biogeochemical functioning of the sites. They are grouped into four datasets: hydrology, fluvial export of organic matter, greenhouse gas fluxes and meteorology/soil physics. The data from all sites follow a common processing chain from the sensors to the public repository. The raw data are stored on an FTP server. After operator or automatic processing, data are stored in a database, from which a web application extracts the data to make them available ( https://data-snot.cnrs.fr/data-access/ ). Each year at least, an archive of each dataset is stored in Zenodo, with a digital object identifier (DOI) attribution ( https://zenodo.org/communities/sno_tourbieres_data/ ).  相似文献   

High‐resolution quantification of earthworm calcite granules from western European loess sequences reveals stadial–interstadial climatic variability during the Last Glacial     

Charlotte Prud'homme  Olivier Moine  Jerome Mathieu  Segolene Saulnier‐Copard  Pierre Antoine 《Boreas: An International Journal of Quaternary Research》2019,48(1):257-268

High concentrations of calcite fossil granules produced by earthworms (ECG) have been identified in most of the stratigraphical units along the loess‐palaeosol reference sequence of Nussloch (Germany). They are particularly abundant in interstadial brown soils and in tundra gley horizons, the latter reflecting short‐term phases of aggradation then degradation of permafrost. These granules are characterized by a radial crystalline structure produced in the earthworms by specific bio‐mineralization processes. In our study, we used this biological indicator combined with ¹⁴C and OSL dating, and sedimentological parameters to characterize millennial‐time scale climatic variations recorded in loess sequences. The approach is based on high‐resolution counts of ECG throughout a 17‐m‐thick loess sequence (332 samples). Strong increases in granule and mollusc concentrations suggest warmer climate conditions during palaeosol formation phases, associated with increasing biodiversity, biological activity and vegetation cover. Decreased granule concentrations occur within primary loess deposits, indicating a strong correlation with palaeoenvironmental conditions and demonstrating the reliability of ECG concentration variations as a new palaeoenvironmental proxy. Finally, this pattern is also recorded in loess sequences located about 600 km westward in northern France demonstrating the large‐scale validity of this new palaeoclimatic proxy.  相似文献   

Effects of the geometry of two‐dimensional fractures on their hydraulic aperture and on the validity of the local cubic law          下载免费PDF全文

Ahmad Hajjar  Luc Scholtès  Constantin Oltéan  Michel Antoine Buès 《水文研究》2018,32(16):2510-2525

Flow through rough fractures is investigated numerically in order to assess the validity of the local cubic law for different fracture geometries. Two‐dimensional channels with sinusoidal walls having different geometrical properties defined by the aperture, the amplitude, and the wavelength of the walls' corrugations, the corrugations asymmetry, and the phase shift between the two walls are considered to represent different fracture geometries. First, it is analytically shown that the hydraulic aperture clearly deviates from the mean aperture when the walls' roughness, the phase shift, and/or the asymmetry between the fracture walls are relatively high. The continuity and the Navier–Stokes equations are then solved by means of the finite element method and the numerical solutions compared to the theoretical predictions of the local cubic law. Reynolds numbers ranging from 0.066 to 66.66 are investigated so as to focus more particularly on the effect of flow inertial effects on the validity of the local cubic law. For low Reynolds number, typically less than 15, the local cubic law properly describes the fracture flow, especially when the fracture walls have small corrugation amplitudes. For Reynolds numbers higher than 15, the local cubic law is valid under the conditions that the fracture presents a low aspect ratio, small corrugation amplitudes, and a moderate phase lag between its walls.  相似文献   

Morphological signatures of deglaciation and postglacial sedimentary processes in a deep fjord-lake (Grand Lake,Labrador)     

Annie-Pier Trottier  Patrick Lajeunesse  Antoine Gagnon-Poiré  Pierre Francus 《地球表面变化过程与地形》2020,45(4):928-947

High-resolution multibeam bathymetric data and acoustic sub-bottom profiles were recently collected in Grand Lake (Labrador), one of the deepest lake basins in eastern North America, to reconstruct: (1) the retreat of the Laurentide Ice Sheet (LIS) west of Lake Melville and (2) the history of sedimentation since deglaciation in this 54 km-long, 3 km-wide fjord-lake. Our results provide a morphostratigraphical framework that brings new insights to the style and pattern of retreat of the LIS in the region, as well as deglacial and postglacial sedimentary dynamics. Terrestrial glacial lineations observed on a digital elevation model (DEM) provide evidence of a previously undocumented ice stream in the Grand Lake area. This newly mapped ice stream suggests that the calving bay formed in Lake Melville triggered a reorganization of the regional drainage pattern of the LIS. The sedimentary infill of Grand Lake consists of a sequence of deglacial to postglacial sediments that contain deposits related to a series of mass movements. The 8.2 cal ka BP cold event is recorded in Grand Lake by a series of closely spaced moraines deposited at the outlet of the fjord-lake to form a morainic complex similar to the Cockburn morainic complex on Baffin Island. During deglaciation, a dense dendritic network of proglacial gullies incised into the steep sidewalls of the lake. Since deglaciation, paraglacial and postglacial sedimentation has led to the deposition of large prograding deltas at the fjord head, where density currents remain active today and have formed a series of sediment waves on the frontal slopes and a prodeltaic environment. © 2019 John Wiley & Sons, Ltd.  相似文献   

Corrective pattern-matching simulation with controlled local-mean histogram   总被引：1，自引：1，他引：0  

Corentin Faucher  Antoine Saucier  Denis Marcotte 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(8):2027-2050

This paper presents a new stochastic simulation method that improves on our unilateral patchwork simulation method (Faucher et al., Stoch Environ Res Risk Assess, 27:253–273, 2012) by eliminating anisotropy biases. As in our unilateral method, images are built by assembling patterns together while controlling the local-mean histogram. The patterns, which are square image-pieces, are picked in a reference image. The reference image is used as a data bank holding the statistical informations about the random field to simulate. In contrast with the unilateral method, the path followed by our new simulation is random and guided by local errors. The new method, called corrective pattern-matching simulation, proceeds iteratively by making local corrections to the simulated image. For several types of images, it is shown that our simulations respect conditioning data and reproduce faithfully the reference image visual appearance. It is shown that the control of the local-mean histogram allows to control one-point statistics and multi-point statistics.  相似文献   

Ontogenetic Habitat Shifts of the Atlantic Tomcod (<Emphasis Type="Italic">Microgadus tomcod</Emphasis>) Across an Estuarine Transition Zone     

Marc Antoine Couillard  Gilbert Cabana  Jean François Dery  Gaétan Daigle  Julian John Dodson 《Estuaries and Coasts》2011,34(6):1234-1245

Tomcod (Microgadus tomcod) in the St. Lawrence estuarine transition zone (ETZ) undergo an ontogenetic habitat shift. Older age classes, characterised by a male-dominated sex ratio, disperse downstream over the summer months to occupy the colder more saline waters of the estuary. Significant differences in length and mass along the salinity gradient were observed in September with upstream fish of any given age class generally exhibiting greater growth. These differences were not seen in early summer. Benthic amphipod δ ³⁴S signatures were strongly correlated with salinity and served to demonstrate that tomcod δ ³⁴S signatures were not in isotopic equilibrium in the more saline waters of the ETZ. Seasonal distributional patterns, growth dynamics and isotopic disequilibrium all indicate that the observed habitat shift may occur on an annual basis, following winter aggregation in warmer, less saline waters. Tomcod located in the downstream parts of the ETZ, predominantly males, were significantly more sexually developed than upstream tomcod for a given age. On the other hand, greater growth early in life is insured by occupying warmer, upstream waters during the summer months.  相似文献   

Soil Organic Carbon mapping of partially vegetated agricultural fields with imaging spectroscopy     

Harm Bartholomeus  Lammert Kooistra  Antoine Stevens  Martin van Leeuwen  Bas van Wesemael  Eyal Ben-Dor  Bernard Tychon 《International Journal of Applied Earth Observation and Geoinformation》2011

Soil Organic Carbon (SOC) is one of the key soil properties, but the large spatial variation makes continuous mapping a complex task. Imaging spectroscopy has proven to be an useful technique for mapping of soil properties, but the applicability decreases rapidly when fields are partially covered with vegetation. In this paper we show that with only a few percent fractional maize cover the accuracy of a Partial Least Square Regression (PLSR) based SOC prediction model drops dramatically. However, this problem can be solved with the use of spectral unmixing techniques. First, the fractional maize cover is determined with linear spectral unmixing, taking the illumination and observation angles into account. In a next step the influence of maize is filtered out from the spectral signal by a new procedure termed Residual Spectral Unmixing (RSU). The residual soil spectra resulting from this procedure are used for mapping of SOC using PLSR, which could be done with accuracies comparable to studies performed on bare soil surfaces (Root Mean Standard Error of Calibration = 1.34 g/kg and Root Mean Standard Error of Prediction = 1.65 g/kg). With the presented RSU approach it is possible to filter out the influence of maize from the mixed spectra, and the residual soil spectra contain enough information for mapping of the SOC distribution within agricultural fields. This can improve the applicability of airborne imaging spectroscopy for soil studies in temperate climates, since the use of the RSU approach can extend the flight-window which is often constrained by the presence of vegetation.  相似文献   

Correction to: New insights into the rainfall variability in the tropical Andes on seasonal and interannual time scales     

Segura  Hans  Junquas  Clementine  Espinoza  Jhan Carlo  Vuille  Mathias  Jauregui  Yakelyn R.  Rabatel  Antoine  Condom  Thomas  Lebel  Thierry 《Climate Dynamics》2021,56(1-2):679-680

Climate Dynamics - The original version of the article contained errors in Fig.  相似文献   

Identifying saline wetlands in an arid desert climate using Landsat remote sensing imagery. Application on Ouargla Basin,southeastern Algeria     

Fethi Medjani  Belkacem Aissani  Sofiane Labar  Mohamed Djidel  Danielle Ducrot  Antoine Masse  C. Mei-Ling Hamilton 《Arabian Journal of Geosciences》2017,10(7):176

Supervised and unsupervised satellite image classifications have progressed greatly in recent years. However, discrimination difficulties still remain among classes that directly affecting data extraction and surface mapping accuracy. The Ouargla region in southeastern Algeria is intersected by wadis, where direct communication between the shallow groundwater table and these dry, overlying ephemeral stream beds exists. Underflowing groundwater exfiltrates into low-lying aeolian blowouts or endorheic basins forming oases, chotts, and sebkhas, commonly known as saline wetlands. These wetlands are becoming increasingly vulnerable to anthropogenic stress, resulting in significant water degradation. Wetland microclimates are very important to arid regions, as they promote oasis ecosystem sustainability and preservation. High water salinity in these ecosystems, however, directly affects flourishing habitat and undermines successful desert oasis development. The objective of this work is to choose the best classification method to identify saline wetlands by comparison between the different results of land use mapping within the Ouargla basin. Landsat ETM+ (2000) satellite imagery, using visual analysis with colored compositions, has identified various forms of saline wetlands in the Ouargla region desert environment in southeast Algeria. The results show that supervised classification is validated in the identification of Saharan saline wetlands, and that support vector machine (SVM) algorithm presents the best overall accuracy.  相似文献   

Intra-interstadial environmental changes in Last Glacial loess revealed by molluscan assemblages from the Upper Palaeolithic site of Amiens-Renancourt 1 (Somme,France)     

Olivier Moine  Pierre Antoine  Sylvie Coutard  Gilles Guérin  Christine Hatté  Clément Paris  Ségolène Saulnier-Copard 《第四纪科学杂志》2021,36(8):1322-1340

The Amiens-Renancourt 1 site recently yielded one of the most important Upper Palaeolithic human occupations of northern France by the number of flint artefacts and especially by the presence of Venus figurines. All the material comes from a single archaeological layer located in a tundra gley bracketed by loess units. A multi-proxy study combining a detailed stratigraphy, luminescence and radiocarbon datings and high-resolution (5 cm per sample) grain size and molluscan analyses was therefore carried out to reconstruct and date the associated environmental changes and to determine the exact context of the human occupation. The chronological frame thus established supports the correlations of the archaeology-bearing tundra gley and of an underlying arctic brown soil with Greenland interstadials GI-4 and GI-3. Composition changes in the molluscan population enabled the identification of transitional and optimum phases and sub-phases within these two pedogenetic horizons. A conceptual correlation model linking molluscan phases with millennial-scale variations of Greenland ice-core and Sieben Hengste speleothem climate records is proposed. The Human occupation appears contemporaneous to the end of the stadial–interstadial transition of GI-3. Synchronous in Amiens-Renancourt 1 and Nussloch, subsequent micro-gleys may also result from a regional/global forcing. Such a level of detail is unprecedented in a loess sequence.  相似文献