Les formes d'érosion actuelle dans la Sierra Madre occidentale (nord- ouest du Mexique) : vers une cartographie de l'érosion

Un secteur de 400 km2, situé au coeur de la Sierra Madre occidentale, sert de témoin à un inventaire des formes d'érosion des sols par ravinements et mouvements de terrain en terrassettes ainsi que des sapements latéraux de cours d'eau. Alors que les caractéristiques climatiques régionales ne témoignent pas d'une agressivité marquée, le facteur déclenchant semble être la surchage pastorale (troupeaux bovins) au détriment de la couverture herbacée ; ceci expliquerait la décroissance de la biomasse totale visible sur des documents satellitaires de 1972 et 1992 alors que les pinèdes se sont étendues durant cette période. L'accroissement probable des coefficients de ruissellement, lié à cette dégradation et au tassement du sol, paraît être la cause des phénomènes de ravinement et de sapement de berges qui affectent la région de manière encore peu brutale. (Résumé d'auteur

Understanding mountain soils : a contribution from mountain areas to the International Year of Soils 2015

In the highlands of southern Colombia and northern Ecuador, soils developed on volcanic ash deposits have specific properties: high water retention, high hydraulic conductivity and high carbon (C) contents. The main role of the soils is to regulate the water available for the dense population living in the valleys. Soil properties and land use depend on their altitudes. Any important modification of land-use change has a serious effect on soil properties and consequently the ecosystem properties such as water regulation and flood control. This can be a threat for a city that relies on the ecosystem for its water supply, as is the case in Ecuador's capital, Quito

Topology-Aware Surface Reconstruction for Point Clouds

We present an approach to inform the reconstruction of a surface from a point scan through topological priors. The reconstruction is based on basis functions which are optimized to provide a good fit to the point scan while satisfying predefined topological constraints. We optimize the parameters of a model to obtain likelihood function over the reconstruction domain. The topological constraints are captured by persistence diagrams which are incorporated in the optimization algorithm promote the correct topology. The result is a novel topology-aware technique which can: 1.) weed out topological noise from point scans, and 2.) capture certain nuanced properties of the underlying shape which could otherwise be lost while performing surface reconstruction. We showcase results reconstructing shapes with multiple potential topologies, compare to other classical surface construction techniques, and show the completion of real scan data

Wettability decay in an oil-contaminated waste-mineral mixture with dry-wet cycles

The dependency of soil particle wettability on soil water content implies that soils subjected to drying-wetting cycles become wettable with wetting and water repellent with drying. While this has been demonstrated widely, the results are contradictory when water repellent soils are subjected to a sequence of cycles. Added to this, past wettability measurements were seldom done in batches of samples collected from the field at natural or dry water contents, with little appreciation that slight particle size variations, different drying-wetting histories and fabric (as required by different wettability measurement methods) may alter the results. This note presents soil particle wettability—soil water content relations by means of an index test following staged drying and wetting paths over a period of 8 months for an untreated, oil-contaminated anthropogenic soil (a mixture of slag, coal particles, fly ash and mineral particles) from Barry Docks (UK), a site formally used for oil storage, which is to be remediated and redeveloped for housing. The results revealed a decrease in the water repellency and increasing mineralization and bacterial activity with the wetting and drying cycles.postprin