Restauration écologique dans un système estuarien fortement anthropisé : applications au compartiment sol des écotones rivulaires et aux marais alluvionnaires de la Basse Vallée de Seine

Since the mid 19th century, Seine Estuary has been subject of heavy human interference to facilitate the deep draft navigation (channelization, embankments, and dredging) affecting the natural flooding regime of riparian ecosystems. The same time, floodplain has also been the subject of management in order to allow (1) agriculture land use and (2) the exploitation of alluvial materials (extraction aggregates). The present study aims (i) to determine whether the current state of anthropized riparian ecosystems of the lower Seine valley requires and authorizes the restoration of a functioning considered as acceptable for riparian ecosystems, and (ii) to monitor the functioning of reconstituted soil following the filling of gravel-pit using dredged sediments in the floodplains of the Seine Estuary.The first part of the thesis is devoted to diagnose the current state (morphology and functioning) of soils in riparian ecosystems and follow their potential capacity to remove nitrogen during experiments microcosms. The main results of morphology and functional measurements (in situ and ex situ) show that soils in riparian ecosystems cannot be grouped according to their degree of connectivity. Functional measurements showed that low connected sites remains favorable to the sink of carbon and nitrogen removal. Then, I assessed the effect of flood duration due to the daily water fluctuation versus river floods on N removal in riparian soils, a microbially-mediated soil process, through two experiments studies. The first of two studies showed that the daily water fluctuation has a significant effect on the improvement of purifying capacity of soils. The second study showed that disconnected soils have found their normal functions after a change of water regime. Also, it suggests that between 3- and 7-day long waterlogging is needed in the disconnected soils for it to exhibit a significant denitrification level.The second part of the thesis focused in the evaluation of success of the restoration experience following the filling of gravel-pit using dredged sediments. Overall, the results obtained in this part show that (1) the diachronic monitoring of soil characteristics is not efficient to assess if typical wetland soil characteristics are reached in reconstituted soils in a short duration of follow and (2) the functional approach (in situ and ex situ) relative to soil respiration, mineralization of C and N and denitrification appear to be a good tool for evaluating.Depuis le milieu du 19ème siècle, l’estuaire de la seine a fait l’objet de lourds aménagements pour autoriser la navigation de bateau à fort tirant d’eau jusqu’à Rouen (chenalisation, endiguements, dragage) impactant les écosystèmes rivulaires en les déconnectant souvent du fleuve. Dans le même temps, la plaine alluviale de l’estuaire de Seine a également fait l’objet d’aménagements pour permettre (1) l’utilisation agricole des sols (drainage) et (2) l’exploitation des matériaux alluvionnaires (extraction de granulats). L’étude présentée ici a pour objectifs (i) de déterminer si l'état actuel des écosystèmes rivulaires anthropisées de la basse vallée de Seine nécessite et autorise, la restauration d'un état et d’un fonctionnement considérés comme écologiquement acceptables pour un écotone rivulaire, et (ii) de suivre le fonctionnement d’un sol reconstitué suite au comblement d’une ballastière à l’aide de sédiments de dragages au sein de la plaine alluviale de l’estuaire de la Seine.La première partie de la thèse est consacrée à diagnostiquer l’état actuel (morphologie et fonctionnement) des sols des écosystèmes rivulaires et de suivre leurs potentialités en terme de capacités épuratrices vis-à-vis de l’N lors d’expérimentations en microcosmes. Les résultats sur la morphologie et le fonctionnement (in situ et ex situ) montrent que les sols des écosystèmes rivulaires ne peuvent pas être regroupés selon leurs degrés de connectivité. Les mesures fonctionnelles ont montré que les sites moins connectés au fleuve restent favorables à l’expression de la fonction de stockage de carbone et à la dénitrification. J’ai ensuite testé expérimentalement l'effet d’une durée d’inondation attribuable aux variations journalières de niveaux d’eau versus les crues du fleuve sur la fonction épuratrice vis-à-vis de l’azote des sols d'écosystèmes rivulaires par voie bactérienne, à travers deux études expérimentales. La première a mis en évidence que les inondations journalières de niveau d’eau a un effet significatif sur l’amélioration de pouvoir épurateur des sols. La seconde étude a montré que les sols actuellement déconnectés retrouvent leurs fonctions normales après une modification de régime hydrique. De plus elle suggère que le temps nécessaire pour qu’un sol déconnecté retrouve un niveau significatif de dénitrification est de 3 à 7 jours d’engorgement en eau.La seconde partie de la thèse s’est principalement intéressée à l’évaluation du succès d’une expérience de restauration suite au comblement d’une ballastière avec de sédiments de dragages. L’ensemble des résultats obtenus dans cette partie montrent que (1) l’approche pédologique et écologique employée n’a pas été suffisante pour évaluer le succès de la restauration sur une courte durée de suivi et que (2) l’approche fonctionnelle (in situ et ex situ) relative à la respiration du sol, à la minéralisation du C et de l’N et à la dénitrification semble être pertinente pour l’évaluation

VehRelay

This sample dataset can be used for the classification of vehicles for the relay selection in routing protocols. It uses six attributes of a vehicular node for classification.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Impact of soil matric potential on the fine-scale spatial distribution and activity of specific microbial degrader communities

International audienceThe impact of the soil matric potential on the relationship between the relative abundance of degraders and their activity and on the spatial distribution of both at fine scales was determined to understand the role of environmental conditions in the degradation of organic substrates. The mineralization of 13C-glucose and 13C-2,4-dichlorophenoxyacetic acid (2,4-D) was measured at different matric potentials ( 0.001, 0.01 and 0.316 MPa) in 6 9 6 9 6 mm3 cubes excised from soil cores. At the end of the incubation, total bacterial and 2,4-D degrader abundances were determined by quantifying the 16S rRNA and the tfdA genes, respectively. The mineralization of 2,4-D was more sensitive to changes in matric potential than was that of glucose. The amount and spatial structure of 2,4-D mineralization decreased with matric potential, whilst the spatial variability increased. On the other hand, the spatial variation of glucose mineralization was less affected by changes in matric potential. The relationship between the relative abundance of 2,4-D degraders and 2,4-D mineralization was significantly affected by matric potential: the relative abundance of tfdA needed to be higher to reach a given level of 2,4-D mineralization in dryer than in moister conditions. The data show how microbial interactions with their microhabitat can have an impact on soil processes at larger scales

Chemical changes during composting of plant residues reduce their mineralisation in soil and cancel the priming effect.

4 pagesInternational audienceApplying composts is useful for increasing soil carbon (C) stocks and improving agricultural productivity. In order to understand the effects of composts on soil organic matter (SOM) formation and mineralisation, 13C-labelled plant residues, previously composted or not, were incubated in an arable soil. The amount of 13C was quantified in the CO2 evolved, the dissolved organic carbon (DOC) and in the microbial biomass (MB). Composting decreased (from 29 to 9%) the proportion of the plant residue labile pool and increased the residence time of both labile and more stable pools from 21 to 34 days and 1.5–5.5 years, respectively. At the beginning of the incubation, the amounts of 13C in the DOC and MB were significantly higher when adding fresh residues than composted ones to the soil. A priming effect on SOM mineralisation (+21% over 3 years) was only observed for non-composted residues. These differences were attributed to changes in the chemical composition of plant materials during composting (less sugars and lipids, more lignins). In terms of C budget, the total loss of CO2 (including the composting process and the SOM priming by fresh residues) was comparable for both treatments after 600 days of incubation

Real-time PCR for quantification in soil of glycoside hydrolase family 6 cellulase genes

International audienceCellulose is the main structural component of the cell walls of higher plants, representing c. 35-50% of a plant's dry weight; after decomposition and transformation, and constituting a large part of soil organic matter. Telluric micro-organisms able to use cellulose as carbon and energy sources for growth are widely distributed in the environment, but the factors controlling the rate of cellulose degradation are not well understood. In this study, we have developed a quantitative real-time PCR (qPCR) primer set to quantify the glycoside hydrolase family 6 (GH6 family) cellulase genes in soil samples. The qPCR assays were linear over 8 orders of magnitude and sensitive down to 10 copies per assay. qPCR analysis of contrasted soil samples showed densities between 2.47 x 10(7) and 1.48 x 10(10) copies per gram of soil. Cloning and sequencing of the PCR products from environmental DNA confirmed both specific amplification (more than 96%) and the wide diversity targeted by the primer set, throughout nearly all the GH6 family, including sequences of bacteria and fungi

Use of dredged sediments and alkaline peat for soil creation in the floodplain of the Seine estuary (France)

International audienc

Use of dredged sediments and alkaline peat for soil creation in the floodplain of the Seine estuary (France)

International audienc

A comparison of permanent and fluctuating flooding on microbial properties in an ex-situ estuarine riparian system

International audienc

Investigating the impact of plant composting on soil organic matter and microbial community dynamics using stable isotopes and molecular analyses

Investigating the impact of plant composting on soil organic matter and microbial community dynamics using stable isotopes and molecular analyses. 15. International Conference (Network on Recycling of Agricultural Municipal and Industrial Residues in Agriculture), RAMIRAN 201