The French critical zone initiative, called OZCAR (Observatoires de la Zone Critique-Application et Recherche or Critical Zone Observatories-Application and Research) is a National Research Infrastructure (RI). OZCAR-RI is a network of instrumented sites, bringing together 21 pre-existing research observatories monitoring different compartments of the zone situated between "the rock and the sky," the Earth's skin or critical zone (CZ), over the long term. These observatories are regionally based and have specific initial scientific questions, monitoring strategies, databases, and modeling activities. The diversity of OZCAR-RI observatories and sites is well representative of the heterogeneity of the CZ and of the scientific communities studying it. Despite this diversity, all OZCAR-RI sites share a main overarching mandate, which is to monitor, understand, and predict ("earthcast") the fluxes of water and matter of the Earth's near surface and how they will change in response to the "new climatic regime." The vision for OZCAR strategic development aims at designing an open infrastructure, building a national CZ community able to share a systemic representation of the CZ , and educating a new generation of scientists more apt to tackle the wicked problem of the Anthropocene. OZCAR articulates around: (i) a set of common scientific questions and cross-cutting scientific activities using the wealth of OZCAR-RI observatories, (ii) an ambitious instrumental development program, and (iii) a better interaction between data and models to integrate the different time and spatial scales. Internationally, OZCAR-RI aims at strengthening the CZ community by providing a model of organization for pre-existing observatories and by offering CZ instrumented sites. OZCAR is one of two French mirrors of the European Strategy Forum on Research Infrastructure (eLTER-ESFRI) project.

Static winching tests were carried out in order to determine the mechanical resistance of Maritime pine to overturning. The tested stands were selected according to podzolic soil conditions: "wet Lande", characterised by a shallow ground water table and a hard pan horizon, and "dry Lande", with a deeper ground water table and a hard pan absent or broken up. As this soil horizon limits the vertical growth of tree roots, anchorage resistance was investigated with regards to the presence or absence of a hard pan underneath each tree. To determine if mechanical behaviour differed within a stand, trees from inside the stand and edge trees at the border exposed to prevailing winds were also tested. The critical turning moment (TM crit,total ) at the base of the stem was positively related to the variable (H × DBH 2 ) (H, total tree height; DBH, tree diameter). Linear regression analyses between TM crit,total and (H × DBH 2 ) showed that the presence of a hard pan had no significant effect on anchorage resistance in uprooted trees. Stem failure occurred for 82% of trees on dry Lande when (H × DBH 2 ) < 1 m 3 . Moreover, stem failure type on dry Lande indicated that trees were better anchored. On soil with a hard pan, edge trees were found to be 20% more resistant to overturning than inner trees. Edge trees differed from inner trees in that the soil-root plate was two times larger and also possessed a larger surface area on the windward side.

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The cave of Lascaux (Dordogne, France) is a reputable place known for its paintings and engravings. Since 1963, its conservation has been given a priority. Many and various sensors have been set into and around the cave to know underground flow conditions, climatic conditions and carbon dioxide fluctuation. For this gas, abnormal concentrations have been recorded in the lower part of the Lascaux cave. The gas is produced by biogenic activity but the source is still not understood. We have been studying the functional relationship between the concentration of CO2 and the atmospheric pressure, by means of the technique of entropy of curves, which leads to a more rigorous statistical analysis. Results show that external parameter such as rainfall could influence CO2 fluctuation and that a sandy‐clayey formation, located all around the cave, may be the major source of carbon dioxide.