Southwest France Research Articles

Secular shoreline response to large-scale estuarine shoal migration and welding

The 14.5-km North-Médoc coast, southwest France, is a high-energy meso- to macro-tidal environment adjacent to the largest estuary in Europe. Over the last centuries, this coastline has locally suffered periods of severe erosion, threatening coastal infrastructures and requiring the progressive implementation of coastal structures and, more recently, localized beach nourishments. This contribution combines 84 years (1937–2021) of shoreline data from various sources, 118 years (1903–2021) of shallow water bathymetric surveys and historical photographs. Results show that, averaged in both time and space, the coast eroded by −0.6 m/yr over the last 84 years, but with a large alongshore and temporal variability. Erosion is locally peaking at −5.2 m/yr, while accretion is restricted to a remote 2.5-km and locally peaks at 5.4 m/yr. A salient characteristic of shoreline evolution is the alternation of rapid erosion (< −5 m/yr) and dramatic accretion (> 20 m/yr) periods over relatively short intervals (≈ 10 years) and across limited alongshore distances (e.g. couple of kilometers). We show that shoreline change is mainly driven by offshore shoal dynamics originating from the estuary mouth further migrating in both the cross-shore and longshore direction. Two major events occurring at different times and locations, leading to volumetric changes of the order of millions to tens of millions cubic meters are analysed. The first attachment, completed around the 1920s, supplied nearly 5-million m3 of sediment, widening and rising the beach by hundreds of meters and meters, respectively. This shoreline bulge subsequently diffused and migrated downdrift, resulting in a quasi-steady erosion rate of approximately −3.3 m/yr. The second shoal attachment, which started around the 1950s, first stopped the chronic erosion observed in the northern sectors, and subsequently drove dramatic (> 500 m) shoreline accretion in the 1970s. Current yearly small-scale beach nourishments only temporally buffer erosion, while a mega-nourishment with similar scales as the first shoal attachment could provide a more sustainable solution. We anticipate that this study, together with future modelling work will help the coastal managers and decision makers to optimize their coastal management strategy.

Genetic architecture of the response of Arabidopsis thaliana to a native plant-growth-promoting bacterial strain.

By improving plant nutrition and alleviating abiotic and biotic stresses, plant growth-promoting bacteria (PGPB) can help to develop eco-friendly and sustainable agricultural practices. Besides climatic conditions, soil conditions, and microbe-microbe interactions, the host genotype influences the effectiveness of PGPB. Yet, most GWAS conducted to characterize the genetic architecture of response to PGPB are based on non-native interactions between a host plant and PGPB strains isolated from the belowground compartment of other plants. In this study, a GWAS was set up under in vitro conditions to describe the genetic architecture of the response of Arabidopsis thaliana to the PGPB Pseudomonas siliginis, by inoculating seeds of 162 natural accessions from the southwest of France with one strain isolated from the leaf compartment in the same geographical region. Strong genetic variation of plant growth response to this native PGPB was observed at a regional scale, with the strain having a positive effect on the vegetative growth of small plants and a negative effect on the vegetative growth of large plants. The polygenic genetic architecture underlying this negative trade-off showed suggestive signatures of local adaptation. The main eco-evolutionary relevant candidate genes are involved in seed and root development.

Data-model comparisons of isotopic and hydrological variabilities of the karstic vadose zone above Villars Cave, SW-France based on 20 years' monitoring record

Because of the great heterogeneity of the limestone fissures, conduits, and reservoirs in karst areas, the understanding of the infiltration in caves and karst terrains is complicated. For example, the time delays observed between rainfall and the various flows into caves, such as shaft flow and seepage flow, exhibit significant variability. To better understand the infiltration above a typical shallow cave, Villars Cave, South-west France, we used both a very long monitoring (>20 years) isotopic data set of rainfall and dripping rates at two different cave gallery levels (14 m and 36 m below the surface, respectively) and a conceptual model (KarstFor) that mix water flows and isotopes. In order to determine the most appropriate reservoir and flow settings, we used one time-lapse electrical resistivity tomography (ERT) image made above the cave, which were incorporated into the KarstFor model. The modeled variations in storage water and infiltration flows are in a good agreement with the observed dripping discharge rates, indicating seasonal variability and various time delays between water excess ((Rainfall-Evapotranspiration) > 0) and drip rates in the different cave levels. The fact that the model strikingly simulates the small, but constant, isotopic difference of drip water δ18O (δ18Od) values between the upper and the lower galleries of Villars Cave, not only reinforces reliability in the model itself but also reveals the impact of multiple infiltration routes and karst reservoir dynamics on the δ18Od. On an inter-annual scale, the observed δ18Od values follow the variations of the water excess and of the cave temperature, which, in the period analyzed, show a marked trend, possibly induced by the climate variability patterns above the cave. Overall, these results are not only important to better understand the infiltration in karstic zones, but also to better interpret speleothem isotopic records widely used in paleo-climate studies.

Environmental controls on lifeguard-estimated surf-zone hazards, beach crowds, and resulting life risk at a high-energy sandy beach in southwest France

Environmental controls on lifeguard-estimated surf-zone hazards, beach crowds, and resulting life risk at a high-energy sandy beach in southwest France

Health status, healthcare use and child MMR vaccination coverage in Travellers according to their environmental and living conditions in Nouvelle-Aquitaine, France, 2019-2022.

The poor health status of underserved populations is compounded by low vaccination uptake, leading to a greater risk of epidemics. On October 2017, a measles outbreak started in the southwest of France among under-vaccinated social groups, including Travellers. We aimed to describe the health status, healthcare use and child measles-mumps-rubella (MMR) vaccination coverage in Travellers according to their environmental and living conditions. A cross-sectional study with a three-stage random sample design was conducted between October 2019 and March 2022 in the Nouvelle-Aquitaine region in France. Trained social workers administered face-to-face questionnaires to collect data on adults and children. Anthropometric measurements, vaccination records and data using an environmental exposure questionnaire were also collected. The participation rate was high (73.6%), with 1030 adults and 337 children included. Concerning the adults, 36.6% had obesity, 14.4% reported diabetes, 24.7% hypertension and 14.4% major depression. The prevalence of major depression was significantly higher in adults living in precarious and unauthorized housing than in those with adequate housing (19.8 vs. 14.7%, P = 0.03). With regard to children, 45.3% had full (i.e. 2-dose) MMR vaccination coverage at 24 months and 17.9% had obesity. Finally, 74.5% of the households experienced housing insecurity, and 22.2% did not have a supply of drinking water. Traveller children and adults faced deleterious environmental and living conditions potentially affecting their health, healthcare use and vaccination coverage. These results demonstrate the need for urgent interventions for underserved populations which take into account their specific needs.

Calibration of DART 3D model with UAV and Sentinel-2 for studying the radiative budget of conventional and agro-ecological maize fields

Quantifying the radiative budget (RB) of maize, the world's predominant cereal, is crucial to managing its growth in a context of global warming. Its microclimate including temperature, water, and energy flux depend on crop management practices. This paper compares the influence of agroecological practices (AE) and conventional agriculture (CA) on the RB of maize using three-dimensional (3D) radiative transfer modelling and remote sensing (RS) observations. We studied two neighbour maize fields in south-west France, respectively with AE and CA practices. Time series of photosynthetically active radiation absorbed (APAR) by plants (APARplant) and soil (APARsoil) were simulated with the DART radiative transfer model. First, realistic 3D models of the CA and AE fields were created and validated with a new method based on DART and Sentinel 2 and UAV reflectance and vegetation indices acquired in July 2019. At that date, around midday, APARplant was larger by 21.5 W/m2 in the AE field and APARsoil was larger by 20.1 W/m2 in the CA field. We explained these differences by differences in geometric and optical parameters (OP) between the two fields. OPsoil causes ≈45% of the differences in APARplant and APARsoil. The shape of plant causes ≈14% of the difference in APARplant and ≈17% in APARsoil. OPplant causes ≈14% of the difference in APARplant and ≈1% in APARsoil. Field geometry (row orientation, inter-row and plant distance) causes ≈7% of the difference in APARplant and 2% in APARsoil. It stresses the great role of OPsoil associated to AE practices. Because it integrates the non-linear effects of all above parameters, the LAI (Leaf Area Index) accounts for ≈40% difference in APARplant and APARsoil. The sensitivity of APAR to LAI is twice as low in the AE field than in the CA field. We showed that APAR differences between the AE and CA fields can be even greater with other maize row orientations. We also highlighted the role of the field model on simulated APAR by comparing the use of APAR simulated by a 3D field model and its corresponding 1D turbid field: 1D turbid models resulted in a 16% increase in APARplant and in similar APARsoil, compared to the 3D CA and AE models.

Impact of land-use change on karst spring response by integration of surface processes in karst hydrology: The ISPEEKH model

Karst groundwater represents a source of freshwater for a quarter of the world's population. Modeling the hydrological behavior of karst aquifers while accounting for the spatial variability of the recharge processes and the land-use change impacts on water availability remains a challenge for karst water resources management. Therefore, this study proposes a new semi-distributed hydrological model named Integration of Surface ProcEssEs in Karst Hydrology (ISPEEKH) for simulating the surface-underground water flows in karst-dominated catchments. ISPEEKH couples the restructured version of the Soil and Water Assessment Tool (SWAT+) with a non-linear three-reservoir groundwater model that represents the epikarst and matrix-conduit flow components in a karst aquifer. ISPEEKH was applied to the Baget karst catchment (13.25 km2) in the Pyrénées mountains of southwest France, characterized by a conduit-dominated spring flow and low surface runoff. The model simulated the catchment daily discharge satisfactorily, with NSE = 0.67 and R2 = 0.68 for the 2008–2013 calibration period, and NSE = 0.65 and R2 = 0.69 for the 2014–2018 validation period. The catchment evapotranspiration and discharge amounted to 33 % and 67 % of the average annual precipitation, respectively, and nearly 80 % of the discharge was attributed to spring flow. The matrix-to-conduit flow accounted for 4–7 % of the monthly spring flow during the high-flow period (December to June), and up to 22 % during the low-flow period (July to October). ISPEEKH was then used to assess the hydrological response of the Baget catchment to land-use change scenarios of afforestation and deforestation for wood production and pasture development. Afforestation of the full catchment area did not alter the catchment hydrology significantly. Deforestation for wood production reduced annual evapotranspiration by 12–18 % and increased annual recharge by 7–8 %, resulting in annual discharge rising by 6–9 %. These changes in the water balance components were most noticeable during the low-flow season and would augment freshwater availability. Conversely, deforestation for pasture development raised annual evapotranspiration by 13–17 % while reducing annual recharge by around 7 % and discharge by 5–7 %. These changes in the hydrological components were most remarkable during the high-flow season and affected discharge below 2.5 m3.s−1.

Reconstruction of annual and seasonal variations in water temperature in the Haute-Dronne River of southwest France based on δ18O records of freshwater pearl mussel shells (M. margaritifera), and its palaeoenvironmental implications

The aragonitic shells of freshwater pearl mussels (Margaritifera margaritifera) contain annual growth increments, whose composition reflect the geochemistry of the river water and bivalve metabolism. The wide geographic distribution and the long lifespan of M. margaritifera coupled with a previously established relationship between the δ18O values of their shells and river temperature means this taxon is a potentially important environmental archive; such freshwater proxies are currently limited in both space and time. In this paper, we investigate the relationship between δ18O values and both in situ and modeled river temperature (2007–2015) for a population of M. margaritifera living in the Haute-Dronne River (southwest France). Our δ18O data permit the reconstruction of seasonal temperature variations in the river. Sclerochronology reveals that shells also record seasonal patterns and produce winter growth increments, contrary to other investigations carried out on the same mussel species from northern Europe where low winter temperatures (below 5 °C) interrupt shell growth. The presented calibration for M. margaritifera and host river temperature offers the potential for reconstructing palaeoenvironmental conditions based on fossil specimens of the same species. Such reconstructions may improve our understanding of past continental climate and help calibrate regional palaeoclimate models.

Contrasting the evolution of radiation fog over a heterogeneous region in southwest France during the SOFOG3D campaign

AbstractObservations made during the recent SOuth‐west FOGs 3D experiment (SOFOG3D) have been used to investigate the formation and evolution of radiation fog over heterogeneous forest plantations. The focus was on comparing measurements made at a relatively open site on arable land with those made in an approximately 700‐m diameter field surrounded by tree plantations, with both sites hosting an instrumented 50‐m mast. These data showed that at the more sheltered site radiation fog tended to form earlier than at the more open site. This coincided with more rapid decreases and lower minima in both near‐surface temperatures and vertical turbulence from the late afternoon. It is proposed here that the surrounding forest creates a sheltering effect, which can cause a reduction in vertical turbulence and therefore the mixing of cool near‐surface air with warmer air aloft. The near‐surface region is therefore able to cool rapidly, enabling fog to form more readily. Data from additional sites with varying surroundings supported the findings that the more sheltered sites tended to exhibit lower near‐surface nocturnal temperatures. However, the onset of fog formation observed at these additional sites suggested that there could be a limit to how sheltered a site may be before fog formation is inhibited rather than enabled by the surroundings.

Examining the role of minor experiments in French and Catalan eco-communities: Between critique and post-capitalist world-building

This article explores the role of experiments in eco-communities in Southwest France and Catalonia and focuses in particular on the production of post-capitalist natures in experiments with plants. Drawing on Deleuze &amp; Guattari, it first orders experimental practices (around irrigation) in terms of a spectrum from 'minor' to 'major', emphasizing in particular the generativity of 'minor experimentation' that is often exploratory, tentative, and ambiguous. It secondly argues that it is crucial to consider how experimental practices relate to other non-experimental practices on-site, highlighting the relationship between minor experiments evolving into 'majoritized' or stabilized interventions, that may be subject to processes of 'scaling up.' Thirdly, it emphasizes the importance of approaching minor experiments through a careful attention to 'difference' that emerges, rather than directly critiquing such experiments. By contrast, the outgrowth of such experiments merits critical examination, according to more clearly defined, external yardsticks, by which political ecological scholarship can critically adjudicate the value of such experiments. The article does so by examining the ways in which experiments may be 'captured' by capitalist logics, hoping to positively contribute to a political ecology of experiments that fruitfully combines critique with more positive and hopeful experimentation.

Epistaxis associated with Angiostrongylus vasorum infection in a dog

AbstractA 9‐month‐old, female, entire border collie was presented as an emergency for unilateral epistaxis, rapidly evolving to bilateral, and lethargy of sudden onset. A moderate broncho‐interstitial pattern was present on thoracic radiographs, particularly in the caudo‐dorsal lung lobes. Haematology and coagulation parameters (prothrombin time, partial thromboplastin time, fibrinogen) were within normal range. Multiple larvae (L1) of Angiostrongylus vasorum were identified both on flotation (Ovassay technique) and sedimentation (McKenna technique). The dog was treated with fenbendazole (50 mg/kg) for 15 days. On re‐examination, 4 days after completion of treatment, faecal analysis was negative and thoracic radiographs were improved. This case reports epistaxis as the main clinical finding in a young dog infested with A. vasorum, in the southwest of France, where this parasite is endemic. If bleeding diatheses are increasingly reported in angiostrongylosis, epistaxis is an unusual presentation, especially as the sole clinical sign of bleeding, in a dog with normal coagulation parameters.

Hydro-Geochemical Characteristics of the Shallow Alluvial Aquifer and Its Potential Artificial Recharge to Sustain the Low Flow of the Garonne River

The complex and interconnected water challenges linked to global climate change and natural and anthropogenic water resources pressure have become major challenges in the 21st century. The Garonne River and its accompanying alluvial aquifers are considered the most important source for agricultural activities in the Garonne Valley, Nouvelle-Aquitaine Region, southwest France. The water is used for irrigation in summer and to reduce frost damage in spring. The alluvial shallow aquifer is recharged by rainfall, lateral inflow from the hillside, and seepage from the riverbed during the flood periods. The aquifer maintains the flow of the river during dry periods. Moreover, the potential recharge of this aquifer is particularly sensitive to annual climatic fluctuations and consequently affects surrounding ecosystems and related socio-economic activities. The increasing impacts of climate change have increased the concern about the availability of these resources. Various adaptation strategies have been considered to mitigate and adapt to the new situation in southwest France. The artificial recharge of the alluvial aquifer is one such regional adaptation strategy to adapt to climate change. The study has two main objectives: to assess the natural and anthropogenic influence on the groundwater chemistry, and to model water infiltration, and understand the aquifer response and, consequently, the effects on river baseflow. The TAG (Technopole Agen-Garonne) project aims to increase the economic wealth of the region while respecting the region’s agricultural traditions. Runoff water from the TAG zone is collected in retention basins and is a potential source to recharge the shallow alluvial aquifer. Sampling campaigns were carried out during the summer of 2019 to collect groundwater samples from several observation wells. Groundwater levels were measured in 132 wells/boreholes to determine the groundwater level fluctuations and create piezometric maps. Piper, spatial distribution, and ionic ratio plots were used to determine the dominant hydrochemical processes and to delineate the hydrochemical facies in the study area. The groundwater chemistry is controlled by silicate weathering and anthropogenic influence. Groundwater quality appears to be affected by the river water in the wells located in the low plain area. The measurements showed that the groundwater levels in the wells located near the river increase more than 2 m after a flood event. The artificial recharge has increased the groundwater level by more than 1 m close to the infiltration basin after a rainstorm. Similarly, a three-dimensional (3D) groundwater model shows a similar magnitude aquifer response to the induced infiltration. The modeling-obtained result shows that the infiltrated water would take about 4 months to reach the Garonne River, which is an appropriate time to maintain the river’s low-flow and thermal buffering capacity, and thus the functioning of its ecosystems during dry periods.

Environment and Plant Use at La Tourasse (South-West France) at the Late Glacial–Holocene Transition

Abstract The aim of this study is to present new data on vegetation dynamics and plant collecting practices during the Late Glacial and the Early Holocene in southwestern France. La Tourasse cave is located in the Pyrenean piedmont plain, where the Azilian cultural complex was initially defined. The last excavations of the site took place in the 1980s and 1990s and the recovered materials are currently being studied or revisited from a multidisciplinary perspective. We present here the results of the charcoal analysis performed on La Tourasse’s Azilian (ca. 13000–11500 cal. BP) and Mesolithic (ca. 10500–9000 cal. BP) levels, complemented by the study of a small seed assemblage. Our results document the shift from an open landscape towards a forested environment, with the gradual passage from open vegetation dominated by shrubs of the Rose family (Prunus spp.) to the mixed oak forest, which speaks in favor of the biochronological coherence of this sequence. However, marked differences in taxonomic richness and state of the wood from one level to another, unrelated to the prevailing environmental conditions, suggest variable behavior of humans toward wood that could be the result of differing mobility strategies, hearth functionalities, or taxonomic preferences.

Improving Grain Size Analysis to Characterize Sedimentary Processes in a Low-Energy River: A Case Study of the Charente River (Southwest France)

The recognition and quantification of fluvial transport and depositional processes has widely been studied. However, few works have focused on the interpretation and quantification of sedimentary processes in low-energy fluvial environments. This paper features and compares the results of five methods of grain size data processing (statistic moments, textural analysis, multivariate statistics combining Principal Component Analysis and hierarchical cluster analysis, and CM image and end-member modeling analysis) and discusses their efficiencies in characterizing low-energy alluvial plain deposits. These environments are characterized by fine grain size, high-homogeneity deposits at the macroscopic scale, and low grain size variability, hence presenting a difficulty in identifying and splitting an apparently homogeneous sedimentary record into sedimentary sequences. These statistical methods are applied on a ~9 m long core extracted from the fluvial island of la Baine located in the downstream section of the Charente River (Chaniers, Charente-Maritime, France). In the light of these results, elementary statistical parameters (statistical moments, modes, and sorting index) have limited interest in the sedimentary description and interpretation of fine fluvial deposits. Textural analyses are more informative but highly dependent on the classification scheme. Only the multivariate statistics approach and end-member modeling analysis present interesting results and allow the robust identification of sub-units. However, multivariate statistics results are dependent on the choice of input variables and do not support non-zero values, while the second method, the most recent and complex one, needs further developments to clearly connect end-member classes to sedimentary processes.

Biodiversity and pollination benefits trade off against profit in an intensive farming system.

Agricultural expansion and intensification have boosted global food production but have come at the cost of environmental degradation and biodiversity loss. Biodiversity-friendly farming that boosts ecosystem services, such as pollination and natural pest control, is widely being advocated to maintain and improve agricultural productivity while safeguarding biodiversity. A vast body of evidence showing the agronomic benefits of enhanced ecosystem service delivery represent important incentives to adopt practices enhancing biodiversity. However, the costs of biodiversity-friendly management are rarely taken into account and may represent a major barrier impeding uptake by farmers. Whether and how biodiversity conservation, ecosystem service delivery, and farm profit can go hand in hand is unknown. Here, we quantify the ecological, agronomic, and net economic benefits of biodiversity-friendly farming in an intensive grassland-sunflower system in Southwest France. We found that reducing land-use intensity on agricultural grasslands drastically enhances flower availability and wild bee diversity, including rare species. Biodiversity-friendly management on grasslands furthermore resulted in an up to 17% higher revenue on neighboring sunflower fields through positive effects on pollination service delivery. However, the opportunity costs of reduced grassland forage yields consistently exceeded the economic benefits of enhanced sunflower pollination. Our results highlight that profitability is often a key constraint hampering adoption of biodiversity-based farming and uptake critically depends on society's willingness to pay for associated delivery of public goods such as biodiversity.

Investigation of the possible valorization of dredged sediments in compressed earth blocks

The construction sector is currently facing an environmental challenge and construction materials with low CO₂ emissions are needed. In view of this ecological transition, earth constructions are an interesting solution given their low environmental impact and their hygrothermal properties. On the other hand, the ports must be regularly maintained by dredging operations in order to provide the necessary water depth for navigation. This induces huge amounts of sediments that should be valorized as they cannot be discharged in the sea with the evolution of dredging practices laws. This study investigates the potential use of “Arcachon Bay” dredged sediments in South West France in Compressed Earth Blocks (CEB). Several sediment samples were collected from eight different locations along the bay to take into consideration their variability. The characterization of the sediments has been conducted in a cross way by laboratory and field tests to provide a feedback on the limitations and the complementarity of the two approaches and improve the current practices. The correlation between geotechnical and field tests has been also analysed. The field tests allow the characterization of sediments through sensory and cohesion tests such as appearance, smell, plasticity, clay content, cigar, pellet, shine, hand washing and adhesion. The conducted laboratory tests were wet sieving granulometry, sedimentation, Atterberg limits, Organic Matter (OM) content and Methylene Blue Value (MBV). The GTR classification has been also determined and the results showed that most of the sediments are silty clay of class A2 or A3. Based on those data, the compliance of these sediments with the CEB manufacturing recommendations is analysed. Several mix optimization techniques have been proposed to improve the mechanical properties such as adapting the granulometry by adding sand or opting for a chemical stabilization. In addition, a machine learning model based on a dataset collected from the literature has been developed to predict the compressive strength of CEB and optimize the mix and fabrication conditions.

Avian influenza overview April - June 2023.

Between 29 April and 23 June 2023, highly pathogenic avian influenza (HPAI) A(H5N1) virus (clade 2.3.4.4b) outbreaks were reported in domestic (98) and wild (634) birds across 25 countries in Europe. A cluster of outbreaks in mulard ducks for foie gras production was concentrated in Southwest France, whereas the overall A(H5N1) situation in poultry in Europe and worldwide has eased. In wild birds, black-headed gulls and several new seabird species, mostly gulls and terns (e.g. sandwich terns), were heavily affected, with increased mortality being observed in both adults and juveniles after hatching. Compared to the same period last year, dead seabirds have been increasingly found inland and not only along European coastlines. As regards mammals, A(H5N1) virus was identified in 24 domestic cats and one caracal in Poland between 10 and 30 June 2023. Affected animals showed neurological and respiratory signs, sometimes mortality, and were widely scattered across nine voivodeships in the country. All cases are genetically closely related and identified viruses cluster with viruses detected in poultry (since October 2022, but now only sporadic) and wild birds (December 2022-January 2023) in the past. Uncertainties still exist around their possible source of infection, with no feline-to-feline or feline-to-human transmission reported so far. Since 10 May 2023 and as of 4 July 2023, two A(H5N1) clade 2.3.4.4b virus detections in humans were reported from the United Kingdom, and two A(H9N2) and one A(H5N6) human infections in China. In addition, one person infected with A(H3N8) in China has died. The risk of infection with currently circulating avian H5 influenza viruses of clade 2.3.4.4b in Europe remains low for the general population in the EU/EEA, low to moderate for occupationally or otherwise exposed people to infected birds or mammals (wild or domesticated).

Spatiotemporal Behavior of an Extremely Small Seismic Swarm in Pyrenean Foreland, France

ABSTRACT During the large-N MAUPASACQ passive seismic experiment in the foreland of the western Pyrenees (southwest France), an unusual swarm-type seismic sequence was serendipitously recorded in a normally quiet area. Thanks to the density of the deployment and the proximity of all events, it was possible to relocate the hypocenters with a very good relative accuracy through template matching, cross-correlation phase picks, and double-difference algorithm. The four-month seismic activity consists of more than 600 events with local magnitudes ranging between −1.4 and 2.1, clustered in an extremely small volume, and rooted at 4 km depth. The sequence can be divided in two phases of similar durations and event occurrence rates, but of different magnitude–frequency distributions. The presence of an asperity is suggested by the relative abundance of stronger events during the second phase. Fine mapping suggests a small but clear geographic offset of a few tens of meters between the events of the two phases and a very slow migration suggesting a process involving fluids. Changes in the correlation matrices and waveforms of late arrivals at a specific station are also observed, arguing either (and again) for migration of the hypocenters or for changes in the propagation medium between the two phases. The geographical coincidence with the repeated observation of hydrogen leaks on the surface, almost above the swarm, suggests a connection through channels that could carry fluids.

Identification and Trend Analysis of Multistorey Timber Buildings in the SUDOE Region

The construction sector has one of the most polluting economic activities. In this context, several policies are being launched by the European Union to promote the transition to a sustainable economy, and timber construction is a safe way to contribute to it. Due to the recent development of multistorey timber buildings, the architectural and structural typologies have not been widely studied yet and with not many studies from Southern Europe. In this context, the main objective of this research is to identify and analyse the trends in the use of wood as a structural material in multistorey timber buildings (≥4 floors) in the SUDOE region, i.e., Spain, Portugal, and Southwest France. The methodology involved identifying 28 timber buildings in the SUDOE region and 101 worldwide, most of them in Europe, and sending online information request forms to different actors involved in their design and construction, collecting plans and BIM models, and performing technical study visits to the identified reference buildings. The collected information was included in open-access technical datasheets, and different indicators in terms of building uses, structural system, wood species, and wood volume, among others, were defined. The results showed that there is a tendency to construct taller timber buildings in the SUDOE region with a predominant use of local softwood species, with ratios of wood volume per built area varying between 0.3 and 0.4 m3/m2. The mass timber typology using cross-laminated timber (CLT) is mainly used for residential buildings, while post and beam are used for educational and offices buildings. In addition, a potential embodied CO2 equivalent depending on the building typology and use was also analysed.

Climate of a cave laboratory representative for rock art caves in the Vézère area (south-west France)

Leye Cave (Dordogne, France) is a laboratory cave in the Vézère area, a region that contains some of the most famous rock art caves in the world such as Lascaux, Font-de-Gaume and Combarelles, and is listed as Human World Heritage by UNESCO. Leye Cave was selected because it is representative of painted caves, with respect to parameters such as its geological stage, the presence of water and carbon dioxide, the geological state of its walls, and the size of the cave. These wall states are studied to better understand the conditions of conservation of rock art caves without damaging them. The choice of an equivalent medium, i.e., a non-painted cave, was made to be able to conduct experiments or take measurements that would not have been possible in a rock art cave. The climatic conditions (temperature, hygrometry, etc.) monitored since 2011 are central to our understanding of the genesis and evolution of wall states. Leye Cave is sub-horizontal then descendant, forming a cold air trap. The phenomenon of condensation is thought to be important in the genesis of these wall states. Our article presents a model which describes the competition that exists between the conduction of the rock heating the air and the convection cooling the rock, in the area named the “Throne Chamber”, located in the deepest parts of the cave.