Conglomerate megaboulder rockfall, southern shore of the Haha! Mud flow caused by the thawing of the superficial part of the cliff, Manicouagan Peninsula, winter photograph: Pascal Bernatchez. The deposits lay on the ice foot photograph: Pascal Bernatchez.
Océans, mers et littoraux. Une géographie de l'Arctique et de l'Antarctique - Persée
The polyhedrons of clay eventually fall along the foot of the cliff photograph: Pascal Bernatchez. Small ponds formed by geese, Manicouagan River estuary, fall photograph: Pascal Bernatchez. Abstract Abstract A review of coastal erosion dynamics in the St. For example, OECD tests should be performed in artificially spiked and homogenised soils. When these tests are applied in real contaminated soil samples, and even in the field, the validity of the results may be questioned: Soil contamination in real soils is not homogeneous, and earthworms will probably avoid the zones with the highest contaminant concentration, providing potentially confusing results on soil toxicity.
Earthworm burrow systems have been recently characterized using 3D-microimaging, in particular using X-ray computed tomography CT 4,5 Figure 1. This technique allows a 3-dimensional reconstruction of earthworm movement in soil and its monitoring with time. Therefore, the use of this technique will help us to determine any modification that may occur in the behavioural patterns of earthworms when they are introduced in an ecotoxic environment.
The aim of the proposed internship will be to study the behaviour of different earthworm species in mesocosm configurations containing soil samples with different properties and contaminated in different configurations homogeneous contamination, contaminated in linear gradients 6 or soil with a discrete contamination spot. In parallel, the burrow system of earthworms will be monitored with time using CT imaging, in order to discern earthworm behaviour in the contaminated scenarios considered. On the other hand, other basic toxicity features, such as reproducibility and survival will be assessed for each scenario, following OECD guidelines.
These experiences will be a base for the discussion of the validity of standardized bioassays to be used in the field or in actual contaminated soil samples. In close collaboration with Dr. Julia Clause and Dr. A definite objective of the internship will be the writing of a publication in English on which the intern will be a co-author.
For further information or to apply contact maria. More information here. Comment varient-t-ils au cours du temps?
Géographie du littoral de Côte d'Ivoire
Good knowledge in uni- and multivariate statistics with R program. English writing capacities. Student with a strong interest in data analysis. General context of the study: The assessment of the soil quality and its impact on ecosystem services and goods is a scientific and societal issue that has been widely debated in the literature over the last twenty years.
Several indicators of soil quality have been developed Obriot et al.
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This is an important shortcoming because estimators of soil quality based on a compartmentalization of physical, chemical and biological properties, without taking into consideration their interactions, are prone to underestimate the importance of synergies and trade-offs. To address this knowledge gap, Kibblewhite et al. Based on this framework, a CIRAD-IRD team developed a set of 9 indicators to assess three key soil functions: carbon transformation, nutrient cycling and soil structure evolution. This approach provides integrative information that can be closely linked to soil ecosystem services.
Why leaves change colours in the fall
The Biofunctool set has been applied in five experimental sites in Thailand in order to assess the impact of rubber tree plantation land use and induced land use change on soil functioning. In each experimental site, a range of 4 to 6 treatments were studied with the Biofunctool set. The study sites have also been described in terms of soil physical, chemical properties and soil biodiversity. This dataset allows us to test the impact of land use change on soil biodiversity and its consequences for ecosystem function in agricultural systems, which remains an opened question in an agricultural context.
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Objective: The objective of the internship is to acquire a mechanistic understanding of the impact of land use change on soil biodiversity and soil functioning using data from five rubber tree plantation experiments. Methodology proposed: Assemble and curate the different datasets e.
Aggregate the Biofunctool variables to create a soil functioning variable easily linkable to soil ecosystem services. Test alternative hypotheses on the relationship between soil biodiversity, physico-chemical properties and and functioning using mixed effects models and structural equation modeling 1 ex: Poeydebat et al.
Expected output: Acquire a mechanistic understanding of therelationships between land use management, soil biodiversity and soil functioning in rubber tree plantations. Prepare a master thesis report with the structure of a scientific paper. Bailly bailly agroparistech. Des connaissances en Agronomie seront un atout. Pour plus d'informations et pour les figure veuillez consulter le document ci-joint. Philippe Baveye; Dr. The study of the migration and behaviour of non-aqueous phase liquids NAPLs as fuels are in porous media is still in its infancy, and faces difficulties related to the non-uniform transport of this phase, principally due to the interaction of NAPLs with soil constituents i.
NAPL migration may be hindered due to sorption and entrapment in pores, forming "pools" above less porous soil layers, slowing down its downwards migration, and becoming an almost permanent contamination source. Therefore, the study of the soil processes that affect the migration pattern of a fuel plume is very much needed at this point, will have a significant impact on the research about fuel spill migration, and will provide a firm basis to develop forecast models. The innovation of the proposed work relies on the use of X-ray computed tomography CT to obtain 3-dimensional images of the NAPL within soil pores Figure 1, see the attached document at the end of this offer and to monitor with time its movement under different soil-NAPL scenarios.
The research project in which the internship will be integrated aims to study the influence of soil properties on the behaviour, dynamics and spatial distribution of NAPL spills. The data obtained will be used in dynamic 3D-models to predict the migration and behaviour of NAPL spills in soil environments, taking into account the properties of the soil-fuel scenarios tested.
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The results of these experiments are expected to have a significant impact on the understanding of the migration of fuel spills, according to the properties of the soil. Contacts: philippe.
As winter approaches, the yellow turns to orange. Another hardwood tree, the yellow birch, found in the higher elevations of the Smoky Mountains along the Tennessee—North Carolina border, also turns yellow in autumn. Some maple trees, including the sugar maple, Florida maple and black maple named for the color of its bark, not its leaves , take on a yellow hue for the fall season.
enter site The Norway maple is native to eastern and central Europe and southwest Asia, but can be found throughout the northeastern United States. While the fall foliage in North America and East Asia mostly consists of blazing red and fiery orange hues, the autumn leaves in Europe are mostly yellow in color. The above shot captures a maple leaf in the middle of its color transition from a summery green to an autumn yellow.
Some varieties of maples retain their dark green coloring throughout autumn, until the leaves dry up and fall off the trees.
The Fireglow maple tree, for example, has scarlet leaves during the summer that turn a deep, purplish green in the fall. Unfortunately, blue doesn't seem to be part of autumn's color palette. This event is usually triggered by the declining day length and falling temperatures of autumn. Leaf abscission the technical term for the dropping of leaves begins with the degradation of chlorophyll. As the green fades, yellow and orange pigments known as carotenoids are revealed in the leaves of many species. In other plants, pigments called anthocyanins accumulate in the leaves at this time, giving them shades of red and purple.
The scissor cells are stained red and mark the boundary between the branch left and the leaf stalk. And within a few days or weeks, every leaf on these deciduous trees develops a thin bumpy line of cells that push the leaf, bit by bit, away from the stem.
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