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Green roofs have the ability to mitigate stormwater runoff and to reintegrate wild-life and biodiversity in urban areas. However, they constitute complex ecosystems that still encompass grey areas. For instance, there has been only few research conducted on the accuracy of sensors such as capacitive EC-5 or thermic PlantCare, given the specific composition of green roofs substrates. In addition, green roofs often present spatial heterogeneity such as differences in substrate depths or partially shaded areas. This heterogeneity is expected to impact SWC and consequently plants development. Hence, the objectives of this thesis was to test both types of sensors in green roof substrate and to monitor - with abiotic parameters and vegetation coverage - two plots on an extensive green roofs with two different depth and shadowed areas. Firstly, PlantCare appeared as the most suitable sensor for green roofs application, given EC-5 dysfunctions due to poor contact between the sensors and the substrate. Secondly, the difference in depth has an influence in SWC, since the deepest plots presented a higher SWC during the entire experiment. As a consequence, a disparity in vegetation coverage was noticed, as the deepest plot presented more than 20 % of plant coverage while its neighbour had only 5 %. Finally, the shadowed area presented a higher coverage of plants than the rest of the plot. However, the behaviour of SWC was more complicated to seize at this scale due to the presence of plants and the small volume of influence of Plantcare.
Green roofs --- Soil water content --- Spatial heterogeneity --- Sensors --- Soil moisture --- Extensive --- Depths --- Sciences du vivant > Sciences de l'environnement & écologie
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From carbon dating to hydrology, isotopic approaches have a wide range of applications, such as the study of climate change or nutrients cycling in soils. Water stable isotopic analysis is also a promising tool to better understand water dynamics in soil since it can be used to trace root water uptake at different depths. This MSc thesis had two objectives: one technical and one scientific. The first technical objective was a proof of concept in the field of a novel soil water vapour extraction method. This method had already been tested and calibrated in laboratory by Rothfuss et al. which considers isotopic thermodynamic equilibrium between soil liquid water and soil water vapour and the unique requirement of a temperature correction. The second scientific objective was the determination of the vertical root water uptake profile of winter barley crops from isotopic information. This has been done via a multi-sources mixing model (SIAR) that confronts stable isotopic compositions of soil water across depth, with stable isotopic compositions of crop xylem sap water. From a technical aspect, the gas-permeable tubing method is working properly in the field. It provides enough water quantities to be analysed off-line with a laser spectrometer. This study however outlines fractionation errors during the sampling. This work provides insight into RWU patterns of winter barley for its last stage development. Furthermore, this study underlines the importance of input data when using multi-sources mixing model. The sources isotopic signatures have to be discriminative so that the model can differentiate them. Extra parameters such as the root length density and soil water content are essential to provide thorough results.
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Microwave remote sensing --- Ocean temperature --- Soil moisture --- Remote sensing --- Moisture of soils --- Soil water --- Groundwater --- Soil physics --- Soil infiltration rate --- Soils, Irrigated --- Ocean --- Sea temperature --- Seawater --- Water temperature --- Temperature
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