Search

While forests' contributions to people are intimately linked to their soil biodiversity, little is known about how forest soil biodiversity is structured and influenced by forest characteristics. Living and dead trees influence the quantity and the diversity of resources (e.g. litter content) and habitats (e.g. microclimate) available for soil organisms. In this study, we explored the effects of forest characteristics and their relative importance to regional climate and local soil conditions in explaining forest soil biodiversity. We characterised forest quantity (abundance of living and dead trees, and dominant tree leaves C/N), and diversity characteristics (tree sizes, deadwood and tree species diversities). We assessed the response of the diversity of 34 soil trophic groups to climate, soil properties and forest characteristics using environmental DNA metabarcoding data along 16 elevational gradients in the French Alps. Overall, we showed that climate and soil characteristics explained most of the diversity of soil trophic groups. For the diversity of some groups, however, forest characteristics were important drivers (e.g. ectomycorrhizal fungi). In general, forest diversity characteristics had a positive effect on the diversity of soil trophic groups, in agreement with the resource-heterogeneity hypothesis. We also found that the effects of forest characteristics can percolate to high trophic level groups or to groups that do not have a direct link with living or dead trees (e.g. fungivore mites). Forest characteristics can have complex indirect effects that branch out throughout the whole soil food web. Even if mountain forests span large climatic gradients, forest structure and composition can be additional key drivers of soil biodiversity. Thus forest management, by driving forest structure and composition, can have important effects on soil biodiversity in managed forests. • Climate & soil characteristics explain most of soil trophic groups diversity of mountain forests. • However, forest characteristics can be important drivers for some soil trophic groups. • Diversity of alive and dead trees positively impacts soil trophic groups. • Trees effects can percolate to high trophic level or to groups that do not interact directly with them. • Forest management by influencing alive and dead trees can impact soil biodiversity. [ABSTRACT FROM AUTHOR]

In the current context of anthropogenic global warming, one of the purposes of dendrogeomorphic analyses is to provide long and continuous chronologies of mass movements, so as to detect potential trends or shift related to increasing temperatures. However, on documented slopes, the comparison between historical archives and tree-ring records suggests that dendrogeomorphic reconstructions systematically underestimate the natural activity of the process under investigation. In the specific case of snow avalanches, underestimation generally amounts to 50% and the main causes generally given for this difference are related to the magnitude of past events. In this study, we hypothesize that the morphometric characteristics of avalanche paths and their forest cover could have significant impacts on the length and reliability of tree-ring reconstructions. In order to test this hypothesis, we selected four adjacent, albeit differently structured, avalanche paths from the Queyras massif (French Alps), with the aim to compare their potential for a continuous reconstruction of past avalanche activity. On the most active avalanche paths characterized by high-altitude release areas (covered only by shrubby vegetation), tree-ring reconstructions do not exceed one century in length, with recurrence intervals of high magnitude events >25 years. By contrast, on forested couloirs where lower slopes and forest coverage up to the release areas limits the intensity of events, the frequency of reconstructed snow avalanches is 2.5 times higher, the reconstructions span longer periods and the convergence rate with historical archives attest to the reliability of the dendrogeomorphic approach. These results suggest that a careful selection of couloirs is essential and that priority should be given to forested sites as (i) they allow for exhaustive and (ii) reliable reconstructions over (iii) long periods of time. Unlabelled Image • Dendrogeomorphic reconstructions underestimate snow avalanche activity • Underestimation is related with the characteristics of the avalanche paths • Comparison of four contiguous paths with different morphometric characteristics and forest cover • On forested paths, reconstructions cover a longer time span and the convergence rate with historical archives attests their reliability • A careful selection of the couloirs is crucial to provide long and continuous chronologies of mass movements [ABSTRACT FROM AUTHOR]

As direct observations of rockfalls are rare and difficult to obtain over long timescales, stem injuries and their dating with dendrogeomorphic techniques have been applied frequently in the past to reconstruct process activity. However, the analysis of tree-ring samples requires considerable temporal efforts, which can be detrimental in applied research and expert opinions. To compensate for this shortcoming, several studies have lately explored the potential of the counting of visible scars as an alternative method to dendrogeomorphology as it requires much less time and human efforts to reconstruct spatial patterns of rockfall activity. Yet, to date, both approaches have not been compared at the same site. In this paper, based on the extensive analysis of 278 conifer and broadleaved trees (from which 1097 tree-ring cores were extracted) from a mixed forest plot of the Vercors Massif (French Alps), we demonstrate that both methods provide similar spatial patterns of rockfall activity with a strong increase of recurrence intervals down the talus slope and a clear lateral zonation of activity. Despite this apparent convergence between both approaches, our study also evidences that rockfall frequencies strongly differ with tree species and diameter: the visual inspection of conifer stems and the analysis of tree-ring signals in large-diameter broadleaved trees typically lead to an overestimation of recurrence intervals. Based on these findings, we recommend giving priority to the scar-counting approach on small diameter (<15 cm) broadleaved stems and to restrict tree-ring analysis to old conifers that are more susceptible – through the identification of tangential rows of traumatic resin ducts – to provide reliable estimations of long recurrence intervals (as generally observed in the lower portions of the slope). These guidelines should help to improve the reliability of recurrence interval maps of rockfall process activity in forests further, but also to improve cost-benefit ratios of future studies. • Comparison of the counting scar and dendrogeomorphic approaches to reconstruct rockfall in a mixed forest stand • Both approaches provide comparable spatial patterns with an increase of recurrence intervals down the talus slope • Rockfall frequency differs quite substantially with tree species and diameter. • Tree-ring signals in large-diameter broadleaved trees typically lead to an overestimation of recurrence intervals • Our study provides key guidelines to improve the reliability of rockfall hazard zoning [ABSTRACT FROM AUTHOR]

High mountain lakes are a network of sentinels, sensitive to any events occurring within their waterbodies, their surrounding catchment and their airshed. In this paper, we investigate how catchments impact the taxonomic and functional composition of phytoplankton communities in high mountain lakes, and how this impact varies according to the atmospheric nutrient deposition regime. For two years, we sampled the post snow-melt and the late summer phytoplankton, with a set of biotic and abiotic parameters, in six French alpine lakes with differing catchments (size and vegetation cover) and contrasting nitrogen (N) and phosphorus (P) deposition regimes. Whatever the nutrient deposition regime, we found that the lakes with the smallest rocky catchments showed the lowest functional richness of phytoplankton communities. The lakes with larger vegetated catchments were characterized by the coexistence of phytoplankton taxa with more diverse strategies in the acquisition and utilization of nutrient resources. The nutrient deposition regime appeared to interact with catchment characteristics in determining which functional groups ultimately developed in lakes. Photoautotroph taxa dominated the phytoplankton assemblages under high NP deposition regime while mixotroph taxa were even more favored in lakes with large vegetated catchments under low NP deposition regime. Phytoplankton functional changes were likely related to the leaching of terrestrial organic matter from catchments evidenced by analyses of carbon (δ13C) and nitrogen (δ15N) stable isotope ratios in seston and zooplankton. Plankton δ15N values indicated greater water–soil interaction in lakes with larger vegetated catchments, while δ13C values indicated the effective mineralization of the organic matter in lakes. The role played by catchments should be considered when seeking to determine the vulnerability of high altitude lakes to future changes, as catchments' own properties will vary under changes related to climate and airborne contaminants. Unlabelled Image • Altitude lakes are sentinels of global changes. • Phytoplankton composition is impacted by atmospheric and terrestrial nutrient supply. • Phytoplankton functional richness increases in lakes with large catchments. • Mixotroph abundance varies according to catchment features and nutrient deposition. [ABSTRACT FROM AUTHOR]

Max-stable processes are the extension of the univariate extreme value theory to the spatial case. Contrary to the univariate case, there is no unique parametric form for the limiting distribution in the spatial case, and several max-stable processes can be found in the literature. Selecting the best of them for the data under study is still an open question. This paper proposes a procedure for discriminating max-stable processes by focusing on their spatial dependence structure. Specifically, it combines a leave-two-out cross-validation scheme and a large panel of adapted criteria. We compare five of the most commonly used max-stable processes, using as a case study a large data set of winter maxima of3-day precipitation amounts in the French Alps (90 stations from 1958 to 2012). All the introduced criteria show that the extremal-t, geometric Gaussian and Brown–Resnick processes are equally able to represent the structure of dependence of the data, regardless of the number of stations or years. Although these results have to be confirmed by replicating the study in other contexts, they may be valid for a wide range of environmental applications. [ABSTRACT FROM AUTHOR]

Multiple ecosystem services (ES) can respond similarly to social and ecological factors to form bundles. Identifying key social-ecological variables and understanding how they co-vary to produce these consistent sets of ES may ultimately allow the prediction and modelling of ES bundles, and thus, help us understand critical synergies and trade-offs across landscapes. Such an understanding is essential for informing better management of multi-functional landscapes and minimising costly trade-offs. However, the relative importance of different social and biophysical drivers of ES bundles in different types of social-ecological systems remains unclear. As such, a bottom-up understanding of the determinants of ES bundles is a critical research gap in ES and sustainability science. Here, we evaluate the current methods used in ES bundle science and synthesize these into four steps that capture the plurality of methods used to examine predictors of ES bundles. We then apply these four steps to a cross-study comparison (North and South French Alps) of relationships between social-ecological variables and ES bundles, as it is widely advocated that cross-study comparisons are necessary for achieving a general understanding of predictors of ES associations. We use the results of this case study to assess the strengths and limitations of current approaches for understanding distributions of ES bundles. We conclude that inconsistency of spatial scale remains the primary barrier for understanding and predicting ES bundles. We suggest a hypothesis-driven approach is required to predict relationships between ES, and we outline the research required for such an understanding to emerge. [ABSTRACT FROM AUTHOR]

The use of dynamic computational methods has become indispensable for the assessment of rockfall hazards and the quantification of uncertainties. Although a substantial number of models with various degrees of complexity has become available over the past few years, models have only rarely been parameterized against observations, especially because long-term records of rockfalls have proven to be scarce and typically incomplete. On forested slopes, tree-ring analyses may help to fill this gap, as they have been shown to provide annually resolved data on past rockfall activity over long periods. In this paper, a total of 1495 rockfall scars recorded on the stem surface of 1004 trees have been studied at a site in the Vercors massif (French Alps) to calibrate the 3D process based simulation model RockyFor3D. Uncertainties related to the choice of parameters accounting for energy dissipation and surface roughness have been investigated in detail. Because of the lack of reliable data, these parameters typically are estimated based on expert judgments, despite the fact that they have significant impacts on runout distances and bounce height. We demonstrate that slight variations in roughness can indeed strongly affect the performance of runout modeling and that the decreasing downward gradient, observed in field data, is properly reproduced only if reduced roughness (< 10 cm) enables blocks to reach the distal parts of the study plot. With respect to the height of impacts, our results also reveal that differences between simulations and observations can indeed be minimized if softer soil types are preferred during simulation, as they typically limit bouncing. We conclude that field-based dendrogeomorphic approaches represent an objective tool to improve rockfall simulations and to enhance our understanding of parameterization, which is of key importance for process dynamics and thus hazard zoning. [ABSTRACT FROM AUTHOR]

We investigate changes in shortening, displacement and fold geometry to understand the detailed along-strike structural variation within fold-thrust belts, and infer thrust growth and linkage mechanisms. Field observations from the Vercors in SE France are used to characterise deformation style in the region. Parallel cross sections are constructed, analysed and used to create shortening and thrust displacement profiles from the northern to southern Vercors. Sections show changes in structural style and shortening accommodation from thrust-dominated in the north to fold-dominated in the south. The total shortening distance in the Vercors does not change significantly along strike (3400–4650 m), however displacements along individual thrust zones do vary significantly and displacement profiles show a range in displacement gradients (16–107 m/km). Despite relatively simple shortening patterns in the Vercors, sections show a more complex 3D internal structure of the fold-thrust belt. Thrust displacements and geometries suggest both large-scale thrust zones and small-scale thrusts are soft linked, transferring displacement along strike through transfer zones. Short, soft-linked thrust segments indicate an intermediate stage of thrust growth and linkage, well documented for normal fault systems, which form prior to the formation of thrust branches and hard-linked displacement transfer. [ABSTRACT FROM AUTHOR]

Dendrochronological studies are carried out on rural buildings in the French Alps for twenty years. In this contribution, we examine an extensive dataset of larch timbers (n = 1294) that were dendrochronologicaly dated at 139 buildings. This material yielded felling dates spanning the 11th century to the 20th century and contributed to improve our knowledge of human occupation and exploitation of mountain forests during the second millennium CE. From the 11th to the 14th century, rural populations increasingly exploited older forests. The crises of the 14th century led to a significant decrease in construction and by extension in tree cutting. The beginning of the 15th century marks a resumption of construction and felling which is continuous until the beginning of the 20th century. There is a relationship between the age of harvested trees, the number of dates and population fluctuations, which corroborates findings at the European scale. Regional trade probably influenced the stem diameters used in constructions in the immediate vicinity of the forests. Logging regulations can be perceived through variations in the age of harvested trees. The 14th century gap in felling dates would also mark a transition period in the exploitation of mountain forests and by extension a transformation of the economy. [ABSTRACT FROM AUTHOR]

Cosmic-ray exposure (CRE) dating of moraines allow glacier fluctuations and past climate change reconstructions. In the French Alps, there is a lack of moraine dating for the Late Glacial/Holocene transition period. Here we present a chronology of glacier advances in the Upper Romanche valley (French Alps – Massif des Ecrins) based on 10 Be CRE dating. CRE ages of moraines of 13.0 ± 1.1 ka and 12.4 ± 1.5 ka provide evidence for two stages of glacial advance or standstill at the end of the Late Glacial. The CRE dating of a rock avalanche deposit at 12.2 ± 1.5 ka is attributed to post-glacial debuttressing and reveals rapid deglaciation at the end of the Late Glacial. A CRE age of 7.1 ± 0.7 ka of a second mass-wasting, whose triggering factor is unidentified so far, indicates that up to an altitude of 2300 m a.s.l., the valley was ice-free as of ∼7 kyr at the latest. The re-evaluation of 21 moraine 10 Be CRE ages from nine glacial valleys across the Alps shows multiple glacial advances occurring at the Late Glacial/Holocene transition. These results lead to a re-evaluation of the importance of cooling events during the Allerød and the Younger Dryas in the Alps. [ABSTRACT FROM AUTHOR]

Geoheritage is a concept derived from the geosciences, initially referring to the preservation of geoscientific objects. This concept is now used in local or regional development, especially for promoting a territory via the supply of geotouristic services for example. In this way, geoheritage covers the domains of geography, social sciences and strategy planning. In these types of project, geoheritage is considered as a natural resource, which implies a good knowledge of the location and characteristics of the resources concerned. For this purpose, we require an inventory. In this paper, we explore a methodology to draw up a geoinventory adapted to the territorial project of Vercors as well as an analytical approach mixing multivariate statistics and expert knowledge to produce an objective and suitable territorial diagnosis. The statistical approach is PCA-based whereas the heuristic approach combines a blind-test with two non-expert teams and a heuristic classification by two experts. This heuristic approach was based only on visualization of radar chart. Despite the inherent subjectivity of such a methodology, this statistical-expert cross approach provides a consensual classification of the 79 listed geosites and a deeper understanding of the major components making up the inventory. This classification forms the basis of a territorial analysis which proposes the creation of 5 thematic spaces (glacio-tectonic, peleogeomorphology, hydrogeology, morpho-tectonic and stratigraphy) across the whole massif as new territories for the development of geoeducation and geotourism. Finally, the territorial strategy considers the Vercors massif as an important dynamic outdoor museum dedicated to environmental education based on a major contribution arising from the analysis of geoheritage. [ABSTRACT FROM AUTHOR]

The understanding and implementation of snow management in detailed snowpack models is a major step towards a more realistic assessment of the evolution of snow conditions in ski resorts concerning past, present and future climate conditions. Here we describe in a detailed manner the integration of snow management processes (grooming, snowmaking) into the snowpack model Crocus. The effect of the tiller is explicitly taken into account and its effects on snow properties (density, snow microstructure) are simulated in addition to the compaction induced by the weight of the grooming machine. The production of snow in Crocus is carried out with respect to specific rules and current meteorological conditions. Model configurations and results are described in detail through sensitivity tests of the model of all parameters related to snow management processes. In-situ observations were carried out in four resorts in the French Alps during the 2014–2015 winter season considering for each resort natural, groomed only and groomed plus snowmaking conditions. The model provides realistic simulations of the snowpack properties with respect to these observations. The main uncertainty pertains to the efficiency of the snowmaking process. The observed ratio between the mass of machine-made snow on ski slopes and the water mass used for production was found to be lower than was expected from the literature, in every resort. Nevertheless, the model now referred to as “Crocus-Resort” has been proven to provide realistic simulations of snow conditions on ski slopes and may be used for further investigations. [ABSTRACT FROM AUTHOR]

Long-term records of rockfalls have proven to be scarce and typically incomplete, especially in increasingly urbanized areas where inventories are largely absent and the risk associated with rockfall events rises proportionally with urbanization. On forested slopes, tree-ring analyses may help to fill this gap, as they have been demonstrated to provide annually-resolved data on past rockfall activity over long periods. Yet, the reconstruction of rockfall chronologies has been hampered in the past by the paucity of studies that include broadleaved tree species, which are, in fact, quite common in various rockfall-prone environments. In this study, we test the sensitivity of two common, yet unstudied, broadleaved species — Quercus pubescens Willd. ( Qp ) and Acer opalus Mill. ( Ao ) — to record rockfall impacts. The approach is based on a systematic mapping of trees and the counting of visible scars on the stem surface of both species. Data are presented from a site in the Vercors massif (French Alps) where rocks are frequently detached from Valanginian limestone and marl cliffs. We compare recurrence interval maps obtained from both species and from two different sets of tree structures (i.e., single trees vs. coppice stands) based on Cohen's k coefficient and the mean absolute error. A total of 1230 scars were observed on the stem surface of 847 A. opalus and Q. pubescens trees. Both methods yield comparable results on the spatial distribution of relative rockfall activity with similar downslope decreasing recurrence intervals. Yet recurrence intervals vary significantly according to tree species and tree structure. The recurrence interval observed on the stem surface of Q. pubescens exceeds that of A. opalus by > 20 years in the lower part of the studied plot. Similarly, the recurrence interval map derived from A. opalus coppice stands, dominant at the stand scale, does not exhibit a clear spatial pattern. Differences between species may be explained by the bark thickness of Q. pubescens , which has been demonstrated to grow at twice the rate of A. opalus , thus constituting a mechanical barrier that is able to buffer low energy rockfalls and thus can avoid damage to the underlying tissues. The reasons for differences between tree structures are related to the clustered coppice-specific spatial stem distribution in clumps that could result on one hand in bigger gaps between clumps, which in turn decreases the probability of tree impacts for traveling blocks. On the other hand, data also indicate that several scars on the bark of coppice stands may stem from the same impact and thus may lead to an overestimation of rockfall activity. [ABSTRACT FROM AUTHOR]

Our objective is to study the dependence structure of extreme snowfall in the French Alps. Snowfall amount measurements (3 days accumulation period) from 90 monitoring stations providing data spanning from 1958 to 2013 were projected at the same altitude level (1800 m). Annual maxima of projected snowfall were modeled with Generalized Extreme Value (GEV) distributions and transformed in unit Fréchet in order to focus on the dependence structure only. The final goal is to evaluate the spatio-temporal evolution of this dependence structure and to compare the ability of different max-stable models to capture it. In addition to the most classical max-stable models (Smith and Schlather), max-stable processes made available more recently (extremal-t, Geometric Gaussian and Brown-Resnick) were also considered, taking into account spatial anisotropy. These latter models are found to be the most suitable in our case according to CLIC. Further cross-validation on joint exceedance probabilities does not clearly discriminate these max-stable models. Results show that measurement stations in the Northern and Central Alps are strongly dependent whereas stations from the extreme Southern Alps, influenced by Mediterranean effects, are more isolated. Furthermore, extremal dependence appears controlled by the orientation of mountains and valleys. Finally, using an estimation window moving in time, we highlight a recent decrease in extremal dependence at large distances. [ABSTRACT FROM AUTHOR]

In alpine pasture, interspecies transmission has recently been incriminated in the epidemiology of pestivirus infection. The aim of this study was to investigate pestivirus infections in wild and domestic ruminants sharing pastures in the French Southern Alps. Animal sera were screened for pestivirus antibodies against the pestivirus NS3 protein by a commercial blocking enzyme linked immunosorbent assay (ELISA). All 38 domestic herds tested were positive for pestivirus-specific antibodies. Individual sero-prevalence reached 76.5% (95% confidence interval [95% CI]: [74.2–78.8%]) of the 1383 sheep tested. For wild ruminants, 38.7% (95% CI: [33.8–43.9%]) of the 369 chamois tested, 28.7% (95% CI: [17.4–38.1%]) of the 72 roe deer, and 22.2% (95% CI: [6.5–37.9%]) of the 27 mouflons were seropositive. Virus screening was carried out on spleen samples from hunted wild animals ( n = 160) and from 15 domestic ruminants (clinically suspected to be persistently infected animals), by a conventional reverse transcription-polymerase chain reaction (RT-PCR). Three pestivirus strains were isolated from the sheep samples positive by RT-PCR. The viruses were classified in the BDV-3, BDV-Tunisian and BDV-6 genotypes. For the first time, one strain (RUPI-05 strain) was isolated from an alpine chamois and clustered in the BDV-6 genotype, showing in the 5′-UTR region 92% of identity with the ovine isolate from the same area. Thus, an active circulation of pestiviruses was demonstrated in both wild and domestic ungulates from the French Southern Alps. The results suggest that interspecies transmission between sheep and chamois probably occur. [ABSTRACT FROM AUTHOR]

Snow on the ground is a critical resource for winter tourism in mountain regions and in particular ski tourism. Ski resorts are significantly vulnerable to the variability of meteorological conditions already at present and threatened by climate change in the longer term. Here we introduce an approach where detailed snowpack simulation results were crossed with a resort-level geographical and socio-economic database containing information from about 142 ski resorts spanning the entire French Alps domain. This allows us to take into account explicitly the geographical, topographical (altitude, slope and aspect) and spatial organization (distribution of ski-lifts and slopes) features of the ski resorts considered. A natural snow resort viability index was built using all the above information and simulated natural snow conditions from 2000 to 2012. Results were compared to economically relevant information (skier day values) highlighting a complex relationship between ski resort operation and natural snow conditions. The method introduced in this study holds great potential for physically-based and socio-economically-relevant analyses of the functioning of winter tourism economy and projections into the future under climate change conditions. This requires, however, that further improvements are carried out, in particular the explicit integration of snow management practices (e.g. snowmaking and grooming) into the modeling suite. [ABSTRACT FROM AUTHOR]

This study presents an application of a multiple point geostatistics (MPS) to map landforms. MPS uses information at multiple cell locations including morphometric attributes at a target mapping cell, i.e. digital elevation model (DEM) derivatives, and non-morphometric attributes, i.e. landforms at the neighboring cells, to determine the landform. The technique requires a training data set, consisting of a field map of landforms and a DEM. Mapping landforms proceeds in two main steps. First, the number of cells per landform class, associated with a set of observed attributes discretized into classes (e.g. slope class), is retrieved from the training image and stored in a frequency tree, which is a hierarchical database. Second, the algorithm visits the non-mapped cells and assigns to these a realization of a landform class, based on the probability function of landforms conditioned to the observed attributes as retrieved from the frequency tree. The approach was tested using a data set for the Buëch catchment in the French Alps. We used four morphometric attributes extracted from a 37.5-m resolution DEM as well as two non-morphometric attributes observed in the neighborhood. The training data set was taken from multiple locations, covering 10% of the total area. The mapping was performed in a stochastic framework, in which 35 map realizations were generated and used to derive the probabilistic map of landforms. Based on this configuration, the technique yielded a map with 51.2% of correct cells, evaluated against the field map of landforms. The mapping accuracy is relatively high at high elevations, compared to the mid-slope and low-lying areas. Debris slope was mapped with the highest accuracy, while MPS shows a low capability in mapping hogback and glacis. The mapping accuracy is highest for training areas with a size of 7.5-10% of the total area. Reducing the size of the training images resulted in a decreased mapping quality, as the frequency database only represents local characteristics of landforms that are not representative for the remaining area. MPS outperforms a rule-based technique that only uses the morphometric attributes at the target mapping cell in the classification (i.e. one-point statistics technique), by 15% of cell accuracy. [ABSTRACT FROM AUTHOR]

The most recent and complete French glacier inventory was previously the Vivian database, dating from the end of the 1960s but incorporated in the World Glacier Inventory database at the end of the 1990s. Because of the important changes in glacier extent over recent decades an update of the inventory of glaciers of the French Alps was made in a digital vector format (with the associated database) for several dates covering the last 40 years. Such a multitemporal glacier inventory matches a key demand of the Global Terrestrial Network for Glaciers and the Global Land Ice Measurements from Space initiative (GLIMS). Topographical maps, aerial photographs and satellite images were used to map the extent of glaciers using both manual and automatic methods; and the database was generated considering the design of the GLIMS database. Glaciers in the French Alps covered 369 km² in 1967/71, 340 km² in 1985/86, 300 km² in 2003, and 275 km² in 2006/09. This represents a decrease in surface area of about 25% over the entire study period. Acceleration in glacier shrinkage during the study period was revealed, probably linked to the increase in average air temperature in the 20th century, which has been particularly pronounced since the 1970s. The behaviour of glaciers of the French Alps is in agreement with that of glaciers observed by other studies across the European Alps. We also report the distribution of the morpho-topographic variables (aspect, elevation, etc.) of glaciers of the French Alps for the period 2006/09, and analyse changes of these variables in the last four decades. [ABSTRACT FROM AUTHOR]

Inherited and syn-compressional salt-controlled structures in orogens are difficult to distinguish from compressional features because classical salt features (halokinetic growth strata, salt welds) can be misinterpreted as shortening-related structures (syn-kinematic growth strata, tectonic unconformities). In the Sivas basin in Turkey, syn-kinematic salt diapirism entirely shaped the architecture of the foreland and allowed the development of primary and secondary minibasins. One of the most impressive, the Tuzlagözü minibasin, formed by sinking into a salt feeder while being upturned due to compression. This minibasin has been nicknamed the "Turkish Vélodrome" because of its similarity with the well-known Vélodrome structure in the French Alps which shows growth strata and successive unconformities, commonly interpreted as foreland growth syncline features. Based on structural field descriptions and geometric analogies with the Tuzlagözü minibasin, we revisit the Vélodrome as a salt-related minibasin. We argue that the Vélodrome developed as a secondary minibasin above an Oligocene aerial salt glacier: sheet of Upper Triassic evaporites extruded during Alpine orogeny. This new interpretation enables to propose a revised evolution of the sub-Alpine fold-and-thrust belt. In line with other recent works, this study emphasises once again the important role of salt tectonics in the evolution of the sub-Alpine fold-and-thrust belt. [ABSTRACT FROM AUTHOR]

Abstract: Recent dating performed on large landslides in the Alps has revealed that the initiation of instability did not immediately follow deglaciation but occurred several thousand years after ice down-wastage in the valleys. This result indicates that debuttressing is not the immediate cause of landslide initiation. The period of slope destabilization appears to coincide with the wetter and warmer Holocene Climatic Optimum, indicating a climatic cause of landslide triggering, although the role of seismic activity cannot be ruled out. A phenomenon which may partly explain the delay between valley deglaciation and gravitational instability is the temporal persistence of thick permafrost layers developed in the Alps since the Last Glacial Maximum (LGM). This hypothesis was tested through 2D thermal numerical modeling of the large Séchilienne landslide (Romanche valley, French Alps) using plausible input parameter values. Simulation results suggest that permafrost vanished in the Séchilienne slope at 10 to 11ka, 3000 to 4000years following the total ice down-wastage of the Romanche valley at 14.3ka. Permafrost persistence could have contributed to the failure delay by temporally strengthening the slope. Numerical simulations also show that the permafrost depth expansion approximately fits the thickness of ground affected by gravitational destabilization, as deduced from geophysical investigations. These results further suggest that permafrost development, associated with an ice segregation mechanism, damaged the rock slope and influenced the resulting landslide geometry. [Copyright &y& Elsevier]

Abstract: The dynamics of depositional environments and the spatial deformation of drainage networks in foreland basins reflect the tectonic and erosional dynamics associated with the development of mountain belts. The spatial and temporal organization of the Eocene–Oligocene (40–25Ma) sedimentation in the external part of the South Alpine Foreland Basin of France was reconstructed using an integrated cartographic, sedimentological and petrographic analysis of the Tertiary sedimentary successions. The depositional geometries and variations in facies and thickness of the Palaeogene Nummulitic succession, as well as the observed flow directions in various continental and marine sediments, suggest that the Barrême, Blieux and Taulanne synclines were present as palaeovalleys since the Eocene. The sedimentological analysis of the Nummulitic succession allows the identification of three depositional sequences separated by transgressive surfaces that are recognized in the Barrême, Blieux and Taulanne synclines. Correlation of these sequences between the three synclines suggests that these palaeovalleys were connected by a local valley network that recorded the same sea-level fluctuations during the marine Nummulitic sedimentation. The palaeovalley network was structurally controlled by the east–west axes of the Blieux and Taulanne synclines and the north–south axis of the Barrême syncline formed during the “Pyrenean–Provençal” (Late Cretaceous–Middle Eocene) shortening and the first stage of the Alpine history (Middle Eocene) respectively. Later on, the westward “Alpine” compression (since the Early Oligocene) induced local depocenter migration and reversal in flow direction. However, compared to the modern river pattern, the palaeovalley orientation highlights a geometrical stability since their formation (about 40Ma), suggesting a long-term stability of the early structures in the foreland basin. This constancy can be explained by the location of the study area in a piggy-back basin transported at the top of the Provençal thrust sheet that facilitated the preservation of the overall axis orientation of the palaeovalleys. [Copyright &y& Elsevier]

Abstract: In snow-rich areas, snow avalanches endanger settlements and cause heavy damage to infrastructure or transportation routes. In wooded avalanche paths, dendrogeomorphology has been used extensively to reconstruct snow avalanche histories or to complement existing archival records. Several authors noted (i) that avalanche chronologies reconstructed from tree rings would depend on the number of trees sampled, and on (ii) the minimum number of tree-ring responses; and (iii) that they would always represent minimum frequencies. These restrictions gave rise to the question of how much of the real avalanche activity can be captured in tree-ring records. We therefore performed a dendrogeomorphic analysis based on 175 Larix decidua Mill. and 34 Picea abies (L.) Karst. trees from an extensively and accurately documented (1905–2010) avalanche path located in the Arve valley (French Alps) to obtain optimal thresholds for sample size and index values (i.e. percentage of responses in relation to the number of trees alive for a given year). Results clearly demonstrate that a sample size of ~100 trees is needed to obtain the best match between reconstruction (tree rings) and documentation (archives) while minimizing the inclusion of noise in the dendrogeomorphic record. Validation of the reconstruction (1771–2010) with historical archives shows that 13 undocumented events could be added to the archival record and that 43% of all documented events were deciphered with dendrogeomorphic techniques. The reconstruction of the spatial extent and reach of past snow avalanches matches with historical archives as far as the longitudinal extent of the largest avalanches is concerned. Yet, tree-ring records tend to underestimate runout elevations for a majority of minor events. Large discrepancies are also reported between the lateral limits derived with dendrogeomorphic techniques and the data reported in historical reports and hazard maps, with tree-ring data suggesting larger lateral spread of avalanche snow. [Copyright &y& Elsevier]

Abstract: In this paper, we make an inventory of geomorphic remnants of past glaciations, especially glacial stages that occurred just after the Last Glacial Maximum (LGM). More than 35 terrestrial cosmogenic radionuclide (TCR) ages were obtained, providing new chronological benchmarks for defining the transition between the LGM and the Holocene, thus answering some remaining questions in the southern French Alps (upper Durance catchment). TCR ages fit very well with the scenario defined in other parts of the European Alps: two main generations of post-LGM moraines were identified, highlighting a synchronicity of glacial responses during the Younger Dryas and the Preboreal. Indeed, the first generation we identified corresponds to the Younger Dryas period, while the second generation was shaped during the Preboreal period. They suggest that a relatively thick glacier tongue (300m thick) occupied the upper catchment until the end of the Lateglacial period. The glacier tongue disappeared at the very beginning of the Holocene, before a short glacial re-advance during the Preboreal period. This scenario is linked to a very low equilibrium line altitude (ELA) during the Younger Dryas and the Preboreal: located respectively 340 and 150m below the Little Ice Age (LIA) ELA. Collectively, the results highlight a significant west–east gradient in ELA, probably in relation to westerly and northwesterly winds. Finally, the deglaciation pattern in this area is similar to that of the western and northern Alps, and appears significantly different from the patterns found in the inner and eastern Alps (such as the Ubaye and Maritime Alps patterns). [Copyright &y& Elsevier]

Abstract: This study of the Ballandaz landslide (Savoie, French Alps) was carried out as part of the ANR/PGCU-SIGMA research project. Its aim was to characterize the slope by different methods of geophysical imagery, and then use this characterization to provide a combined interpretation of the morpho-structures in order to simulate the geomechanical behavior of the sliding mass. First, electromagnetic mapping was used to identify the variations of the surface lithology and moisture from which one can more precisely locate the active zone of the slope. Then, electrical and seismic 2D imagery methods were used along several transverse and longitudinal profiles in order to produce electrical resistivity and seismic-velocity depth sections showing up the slope''s structures. The H/V method was also tested locally to determine the depth to basement so as to complement the profiles: it reveals potential seismic site effects from the deeper structures. Helped by drilling and inclinometer surveys, the geophysical interpretations have revealed the various units structuring the landslide: (i) the active, very heterogeneous shallow level overlying (ii) a more rigid, less porous, and probably stable shallow bedrock, (iii) boulders, and (iv) the sound geological basement of quartzite and gypsiferous facies. The study has shown the usefulness of combining such different sounding techniques for studying complex environments like landslides; it has also revealed the limitations of each method when used for studying very heterogeneous environments. [Copyright &y& Elsevier]

Abstract: Surface snow samples were collected weekly from the 31st of December 2008 to the 21st of June 2009 from Lake Bramant in the French Alps. Total mercury (THg), total dissolved mercury (THgD), methylmercury (MeHg) and particle distributions in surface snow were analyzed. Results showed that THg concentrations, MeHg concentrations and particle load increased with snow surface temperature, which is an indicator of rising temperatures as the season progresses. Significant correlations between MeHg and snow surface temperature and MeHg and total particles greater than 10μm were observed. This suggests that the MeHg found in the snow originates from atmospheric deposition processes rather than in situ snowpack sources. This study suggests that an important post-winter atmospheric deposition of MeHg and THg occurs on summital zones of the French Alps and it is likely that this contamination originates from the surrounding valleys. [Copyright &y& Elsevier]

Abstract: Total mercury (THg) and methylmercury (MeHg) concentrations were measured in the muscle of Arctic charr (Salvelinus alpinus) and in the water column of 4 lakes that are located in the French Alps. Watershed characteristics were determined (6 coverage classes) for each lake in order to evaluate the influence of watershed composition on mercury and methylmercury concentrations in fish muscle and in the water column. THg and MeHg concentrations in surface water were relatively low and similar among lakes and watershed characteristics play a major role in determining water column Hg and MeHg levels. THg muscle concentrations for fish with either a standardized length of 220mm, a standardized age of 5years or for individualuals did not exceed the 0.5mgkg−1 fish consumption advisory limit established for Hg by the World Health Organization (WHO, 1990). These relatively low THg concentrations can be explained by watershed characteristics, which lead to short Hg residence time in the water column, and also by the short trophic chain that is characteristic of mountain lakes. Growth rate did not seem to influence THg concentrations in fish muscles of these lakes and we observed no relationship between fish Hg concentrations and altitude. This study shows that in the French Alps, high altitude lakes have relatively low THg and MeHg concentrations in both the water column and in Arctic charr populations. Therefore, Hg does not appear to present a danger for local populations and the fishermen of these lakes. [Copyright &y& Elsevier]

Abstract: In December 2008, an intense avalanche cycle occurred in the eastern part of the southern French Alps. Southerly atmospheric fluxes that progressively evolved into an easterly return caused important snowfalls with return periods up to 10years. Cold temperatures and drifting snow had important aggravating effects. The return period for the number of avalanches was above 50years in two massifs and some of the avalanche had very long runouts that exceeded historical limits recorded in the French avalanche atlas. Using this case study, this paper illustrates and discusses how avalanche reports, snow and weather data and results from numerical modelling of the snow cover can be combined to analyse abnormal temporal clusters of snow avalanches. For instance, it is shown how statistical techniques developed in other fields can be used to test the significance of different explanatory factors, extract spatio-temporal patterns, compare them with previous cycles and quantify the magnitude/frequency relationship at different scales. [ABSTRACT FROM AUTHOR]

Abstract: Snow avalanches are a major threat in many parts of the Alps, where they periodically damage infrastructure, disrupt transportation corridors or even cause loss of life. Nonetheless, the spatial behavior of past avalanche activity and the analysis of areas affected during particular events remain often imprecise. It was therefore the purpose of this study to reconstruct spatio-temporal patterns of past avalanche activity on a forested avalanche talus in the French Alps (Pierres Jean Jeanne talus, Massif de l''Oisans, France). A total of 232 European larches (Larix decidua Mill.) with clear signs of snow wasting events was analyzed and growth disturbances (GD) related to avalanche activity was assessed, such as tangential rows of traumatic resin ducts, the onset of compression wood or abrupt growth suppression and release. In total, 901 GD were identified in the tree-ring samples, indicating that 20 high-magnitude avalanches occurred between AD 1919 and 1994. The mean return period of snow avalanches was ~4years with a ~26% probability that an avalanche occurs in any particular year. Interpolated maps allowed for explicit spatial estimates of return periods throughout the talus, showing a rapid increase of return frequency from 2.5 to 50years with increasing distance from the talus apex. The distribution of avalanche years seems to be quite homogeneous in time with a gap between 1951 and 1959 and since 1994. Snowfall from a nearby meteorological station (Saint-Christophe en Oisans; 10km from the study site) indicated that the five most recent high-magnitude events on record occurred due to above-average snowfall anomalies in December and January associated with abnormally low air temperatures. Findings suggest that a strong snow metamorphism under high temperature gradients in January could explain the occurrence of high-magnitude snow avalanches. [Copyright &y& Elsevier]

Abstract: A fertilisation experiment was started in the French Alps on an acid grassland at 2000m in 1989 where lime as calcium carbonate (“liming”) and Thomas Slag enriched by potassium chloride (“fertilisation”) were added in a random block design until 1992. Since then, no further amendments were applied. Fifteen years after the last application, we revisited the experiment and observed that soil pH was still significantly higher on limed plots, while nitrogen (N) concentrations were lower. On fertilised plots, soil carbon (C) and N concentrations were lower compared to unfertilised plots. However, litter quality (C and N concentrations, near infrared spectroscopy [NIRS] data) was similar for both treatments. Vegetation composition, but not species richness, nor Shannon–Wiener or evenness differed between limed and unlimed plots, and fertilised and unfertilised plots. Liming explained about 18% and fertilisation about 6% of the variability of the vegetation composition. These changes in the vegetation composition are probably due to lower abundances of former dominant grass species and to an increase in generalist grasses. However, these changes did not influence the total above-ground productivity, which was similar for all treatments. Tissue N and C concentrations and NIRS data indicated a changed chemical composition of the biomass which persisted during time. We conclude that the 3 years of fertilisation and liming did substantially influence the vegetation composition at our site and lead to an increase in the agricultural value of the grassland. These changes are long-lasting as they changed key features of the functioning in the soil of grasslands ecosystems. From an ecological point of view, specialised vegetation was replaced by generalist species leading to a trivialisation of the vegetation. [Copyright &y& Elsevier]

Abstract: This paper presents a new method for the standardisation of tree-ring series, which attempts to remove the age effect from the low-frequency variations in the series. standardisation techniques based on the biological growth trend (RCS) only remove the trend linked to the age of the tree. However, in some trees, the trend is substantially different from the regional curve, and when the site fertility is not taken into account, the standardisation process may induce significant biases in the RCS standardised curve. An artificial neural network is used here to estimate an adaptive regional growth curve (ARGC) model. For each population or group of populations, the predictors are, in addition to the age (used by RCS) of each ring, the initial and the maximum growth rates (measured by the ring increments) of each tree. We have compared this method to the RCS method, using 20 Pinus cembra sites covering the Southern French Alps. The results show that the ARGC standardisation performs better for growth trend analysis and, by inference, for climate reconstruction. [Copyright &y& Elsevier]

Rock glaciers, usually preserved in periglacial environments of cold-climate high-relief regions, are useful (palaeo)climate indicators. In the European Alps, numerous studies have focused on describing these geomorphological features. However, very few have attempted directly dating them. This lack of measurement is particularly evident in the French Alps. To fill this gap, we performed Cosmic Ray Exposure (CRE) dating through beryllium-10 (10Be) on 10 granitic rock samples collected from two relict rock glaciers, hereafter referred as RG1 and RG2, located at col du Lautaret in the French Alps. This first CRE dating of rock glaciers in the French Alps yielded mean ages of 11.8 ± 0.5 kyrs and 11.6 ± 0.6 kyrs for RG1 and RG2, respectively. While RG2 is clearly a talus-derived rock glacier, the origin of RG1 is less clear. It could potentially be talus-derived, glacier-derived or of mixed origin. The 10Be ages indicate that both rock glaciers became inactive during the transition between the Younger Dryas and the onset of the Holocene, consistently with other studies in the Northern Hemisphere. Considering surface velocity measurements carried out since the 1980s on neighbouring rock glaciers, we hypothesise that the rock glaciers were formed either during the Younger Dryas or slightly earlier, between the Heinrich Stadial 1 and the Younger Dryas. During this period, we estimated temperatures ~3.6 °C lower than the 1980s and precipitation up to 30% lower than at present. • We performed the first direct 10Be dating of two rock glaciers in the French Alps. • Both glaciers were probably formed between Heinrich Stadial 1 and the Younger Dryas. • We suspect they became inactive at about 11 kyrs. • This pattern is consistent with other rare observations from the Alps and Pyrenees. • Rock glacier formation may be associated to temperatures ~3.6 °C lower than in the 1980s. [ABSTRACT FROM AUTHOR]

Abstract: The Upper Durance catchment is an area prone to rock-slope failures. Such failures reflect the combination of high relief, litho-structural controls and paraglacial stress release. The aim of this study is to determine the role of deglacial unloading and resulting paraglacial stress release in conditioning or triggering slope failure. Former dimensions of the Durance glacier are reconstructed, then combined with Digital Elevation Model data in a raster Geographic Information System to quantify the spatial pattern of stresses associated with glacial loading at the Last Glacial Maximum. Preliminary calculations suggest that major rock falls and rock avalanches are associated with areas subject to the highest decompression stresses. Focus on two case studies allows the consequences of paraglacial stress release on slope instability to be evaluated. Description of slope failure runout deposits allows reconstruction of the nature of slope failure. Surface exposure dates based on concentration of cosmogenic 10Be allows the timing of both deglaciation and that of post-glacial rock-slope failures to be established. It is shown that rock-slope failures are concentrated on lower valley-side slopes within the area occupied by ice at the Last Glacial Maximum, and that their locations coincide with zones of inferred high glacial loading stress, consistent with interpretation of both bedrock disruption and large-scale rock-slope failures as paraglacial phenomena induced by stress release following deglaciation. Timing of initial rock avalanche runout deposition at one site is consistent with this conclusion, though later instability episodes at the same site may have occurred independent of the influence of paraglacial stress release. [Copyright &y& Elsevier]

Abstract: Statistical assessment of landslide susceptibility has become a major topic of research in the last decade. Most progress has been accomplished on producing susceptibility maps at meso-scales (1:50,000–1:25,000). At 1:10,000 scale, which is the scale of production of most regulatory landslide hazard and risk maps in Europe, few tests on the performance of these methods have been performed. This paper presents a procedure to identify the best variables for landslide susceptibility assessment through a bivariate technique (weights of evidence, WOE) and discusses the best way to minimize conditional independence (CI) between the predictive variables. Indeed, violating CI can severely bias the simulated maps by over- or under-estimating landslide probabilities. The proposed strategy includes four steps: (i) identification of the best response variable (RV) to represent landslide events, (ii) identification of the best combination of predictive variables (PVs) and neo-predictive variables (nPVs) to increase the performance of the statistical model, (iii) evaluation of the performance of the simulations by appropriate tests, and (iv) evaluation of the statistical model by expert judgment. The study site is the north-facing hillslope of the Barcelonnette Basin (France), affected by several types of landslides and characterized by a complex morphology. Results indicate that bivariate methods are powerful to assess landslide susceptibility at 1:10,000 scale. However, the method is limited from a geomorphological viewpoint when RVs and PVs are complex or poorly informative. It is demonstrated that expert knowledge has still to be introduced in statistical models to produce reliable landslide susceptibility maps. [Copyright &y& Elsevier]

Abstract: The evolution of high-altitude glaciers and human activities in the Grandes Rousses massif is documented by high-resolution seismic reflection profiling and multiproxy analysis of short sediment cores in proglacial Lake Blanc Huez. These lacustrine data are compared with historical chronicles, geomorphological features and glaciological studies in this region of the western Alps and they allow the documentation of recent environmental changes. The specific geometry of high-amplitude reflections in the uppermost seismic unit, the lithology of short cores and the available limnological data in the lake suggest that clastic particles eroded by the glaciers and transported in suspension by glacial melt waters in early summer essentially develop homopycnal flood events in the lake. A conceptual model linking fluctuations of glacier equilibrium line altitudes in the catchment area with sedimentary facies retrieved in the lake basin is proposed. This approach allows reconstructing continuous glacier fluctuations since AD1820–1850 and suggests several phases of glacier fluctuations during the Little Ice Age (LIA). These reconstructions are based on changes in lacustrine sediment laminations, density, magnetic susceptibility, reflectance spectra, organic matter and Arsenic content. The age-depth model of short sediment cores is provided by 210Pb, 137Cs and 241Am radionuclide dating. This chronology is further supported by identifying in lacustrine sediments the impact of (i) the nearby M 5.3 Corrençon earthquake in AD 1962, (ii) the development of the ski resort at high-altitude close to the lake and (iii) the last advance of glaciers during the LIA in AD1820–1850 and the following phase of glacier retreat observed in the alpine region at the end of the LIA in AD 1880. Frequent sandy layers enriched in organic matter and associated with fluctuations in the Arsenic concentrations may result from hydraulic remobilisation of Middle Age mine tailings at the lake shore by snow melt or heavy rain fall events during the LIA. [Copyright &y& Elsevier]

Abstract: The characterization of statistical relationships between snow avalanche occurrence and climate can be useful for avalanche prediction. We investigated the relationship between avalanche occurrences between 1978 and 2003 and meteorological parameters for 576 avalanche events from 12 avalanche tracks in the Valloire valley in the French Alps. Probabilities of avalanche occurrence based on logistic regression analyses were calculated at a daily and yearly time scale, by differentiating high- and low-frequency avalanche tracks. For high-frequency avalanche tracks, the daily probability of avalanche depends on the precipitation (water equivalent, i.e. WE) the day before a given avalanche event, along with the mean air temperature the day of the event. For low-frequency avalanche tracks, on the other hand, it depends on precipitation (WE) the day preceding a given event, only. We also tested the relationship between various meteorological parameters and the type of avalanche. The occurrence of dry snow avalanches is related to total precipitation (WE) on the day of and the day before a given event, whereas that of wet snow avalanches depends on precipitation (WE) the day of a given event, and maximum air temperature during the event. Our results show that for high-frequency avalanche tracks, annual probabilities of high avalanche activity depend on the occurrences of successive days (≥3 days) with high precipitation in winter and above-average air temperature (mean±1 S.D.). For low-frequency avalanche tracks, probabilities of high avalanche activity depend on the occurrences of successive days (≥3 days) with high precipitation in winter. The sensitivity of these models was tested through bootstrap analyses. We also discuss the role of meteorological parameters highlighted in these models. [Copyright &y& Elsevier]

Over a period of 17 years. 84 bacterial isolates identified as Mannheimia haemolytica or M glucosida and 52 isolates identified as Pasteurella trehalosi were detected in the lungs of domestic and wild ruminants in the French Alps. The isolates were serotyped according to their surface capsular antigens, and those sharing common antigens were further characterized by pulsed field gel electrophoresis. The results showed that the bacterial isolates included in the study clustered according to the host species from which they were isolated. These findings indicate that the transmission of serotypes of M. haemolytica, M. glucosida or P. trehalosi from an animal host in which they are common to another species sharing the same geographical space may be a rare epidemiological event. [ABSTRACT FROM AUTHOR]

Abstract: Recently, Global Positioning System (GPS) surveying techniques have been increasingly employed to monitor landslide movement. Here we present an application of GPS to monitor the La Valette landslide, located in the Ubaye Valley in the southern French Alps. This complex landslide is composed by an upper rotational part, a central part with generally translational movement and a lower part, which occasionally transforms into mud flows during intense rainfall events. Displacement rates average a few centimeters per month, with velocity peaks of some centimeters per day during periods of strong activity. GPS data presented in this study were acquired with two single-frequency GPS receivers Magellan connected to multipath-resistant antennas. The data were processed with the Magellan software MSTAR. Nine points have been set in the studied area, seven of them in the moving area, one in a stable area near the landslide and one on the facing slope, which is used as reference point. For each observation, one GPS receiver is placed on the reference point for the whole day and the second one is placed on each monitored point for 1-h sessions. The distance between the base and monitored point ranges from 480 to 1660 m. Eight survey campaigns were made between October 2000 and October 2002, to follow the evolution of the surface displacements. The maximum cumulative 3-D displacement observed in the area was about 21 m during the period in the center part of the landslide, corresponding to an average rate of movement of about 3 cm/day. The accuracy achieved during the GPS measurements has been evaluated to be about 2.4 cm in E–W direction, about 11 cm in N–S direction and about 7.4 cm in elevation in the worst case. The GPS results have been compared with traditional surveying techniques (EDM) carried out on the same site by RTM Service (Restauration des Terrains en Montagne). The velocities obtained by the two methods are similar. The advantage of the GPS technique is the collection of data for the three spatial coordinates (x, y, z) of each point, which allow to calculate the 3-D displacement vector. These measurements have been combined with SAR interferometric data in order to analyse the temporal evolution of the different landslide sectors. [Copyright &y& Elsevier]

Abstract: This study is an attempt to evaluate the relationships between the vegetation and the modern pollen rain as a contribution to palaeoecological research. Pollen analysis of surface moss polsters and floristic records has been undertaken for 51 sampling points distributed all over the study area (Champsaur valley, Hautes-Alpes, France), within different vegetation and land-use types and along a west–east altitudinal transect, ranging from 870 to 2200 m a.s.l. The pollen and vegetation data were analysed independently using numerical methods (clustering and correspondence analysis) to investigate how vegetation is reflected in pollen assemblages. There was a good agreement between classifications and ordinations of the two data-sets and a pollen-analytical separation of different types of human activities was found despite the major gradients related to altitude and soil moisture. Both the AP/NAP ratio and the major pollen type percentage ranges given for each vegetation type were however very wide because of the typical fine-scale mosaic of the landscape in this region. Detailed comparisons of the two data-sets showed consistent differences between vegetation and pollen assemblages. Misclassifications of some modern pollen spectra were mainly attributed to differential pollen representation between species, but also to the effect of various land-use practices on flowering and pollination of herbaceous plant taxa. Moreover these differences, as well as discrepancies with earlier published data from lowlands of southern France and other parts of western Europe, are promoted by complex pollen dispersal which characterizes mountain environments. Although an overlap of characteristics thus exists between pollen assemblages, we were able to recognize specific features and indicator pollen taxa have been identified for each natural, semi-natural and human-induced vegetation type. [Copyright &y& Elsevier]

The sedimentology of a rock-avalanche involving ca. 7·103 m3, that happened on February 1995 at Claix, the French Alps, is analysed here. The talus shows a proximal depression due to the impact of the debris, then a grooved area with few, mainly sandy silt deposits and a downslope accumulation of coarse debris that reaches up to 3 m in thickness. The material underwent mass movement as demonstrated by the steep distal front, the strong fabric strength and the thrust planes. The greatest part of the deposits consists of a clast-supported to partially openwork debris with angular clasts over a sheared matrix-supported basal layer. The largest blocks, often more than 1 m in length, are concentrated at the surface and the front. The overall sedimentological characteristics are similar to those of the small dry grain flows that occur usually on rockfall talus, except for the abundance of fine-grained particles that results from intense cataclasis during flow. It is suggested that the deposits of such medium-scale rock-avalanches, probably not uncommon in seismic regions, may have been confused in previous studies with other slope mechanisms such as debris flow and rockfall. [Copyright &y& Elsevier]

Snow samples have been collected in the French Alps in 1998, 1999 and 2000 in order to measure both total Hg (HgT) and reactive Hg (HgR). Concentrations of HgT were between 13 and 130 pg g−1 and HgR concentrations were below the detection limit (∼0.8 pg g−1). Hg speciation in snow was evaluated on the basis of ionic complexation equilibrium with chloride, hydroxide, oxalate. The pH of the snow was found to be an important parameter for Hg speciation. For pH values near 3, HgC2O4 is predominant in snow samples except for snow strongly influenced by anthropogenic sources (in which case HgCl2 predominates). When pH>4, Hg(OH)2 and HgOHCl are predominant. These latter pH values are observed for precipitation not influenced by anthropogenic sources but more by soil erosion, e.g. Saharan dusts. The knowledge of Hgr speciation in snow is a key question for understanding the mechanisms of transformation of these complexes in snow after precipitation. [Copyright &y& Elsevier]

In the current context of climate change, high Alpine rock slopes and surface deposits are affected by a series of geomorphological processes whose evolution is partly conditioned by permafrost warming and thawing. This degradation directly impacts infrastructure in high mountain areas (e.g. , huts or ropeway transport systems). In this study, we aim to assess the level of risk of destabilization for infrastructure built on permafrost in the French Alps and to discuss the adaptation and mitigation strategies developed by stakeholders. The analysis combines an inventory of the high mountain infrastructure with several data layers - including two recently developed regional maps of permafrost - analysed within a Geographic Information System. We update a destabilization risk index previously developed to identify and rank infrastructure at risk with a hazard characterisation and a vulnerability diagnosis, based on newly available data. The most at-risk infrastructure according to this new risk index are compared with the strategies implemented by the stakeholders to adapt the foundation, reinforce the ground, reduce heat transfer in depth, or monitor the evolution of the ground. Most of the strategies used on the most at-risk cases are reactive to repair the infrastructure after a destabilization. • Inventory of infrastructure potentially built on permafrost in the French Alps. • Evaluation and ranking of the most at-risk infrastructures built on permafrost. • Adaption and mitigation strategies already used to prevent or to cope the destabilization. [ABSTRACT FROM AUTHOR]

Determining avalanche activity corresponding to given snow and meteorological conditions is an old problem of high practical relevance. To address it, numerous statistical forecasting models have been developed, but intercomparisons of their efficiency on very large datasets are seldom. In this work, an approach combining random forests with class-balancing is presented and systematically compared with competing methods currently described in the avalanche literature. On more than 50 years of daily avalanche observations, in the 23 massifs of the French Alps, the competing classifiers are evaluated on their ability to distinguish three classes of avalanche activity: non-avalanche days, days with moderate activity, and days with high activity. Moreover, the variables of higher importance in the random forest classifiers are shown to be coherent with current avalanche literature and a clustering based on these variable importance separates massifs which are known to have different avalanche activities. Our approach opens perspectives to support operational avalanche forecasting. • New approach combining random forests with class-balancing for avalanche prediction. • Systematic comparison with most existing approaches. • Probative results for the 23 massifs of the French Alps using more than 50 years of daily data. • Physical coherence of the main selected variables. • Perspectives to support operational avalanche forecasting. [ABSTRACT FROM AUTHOR]

• Sampling strategy impacts dendrogeomorphic reconstructions of rockfalls. • Guidelines to optimally capture the meteorological drivers in reconstructions. • Trees close to the cliff should be sampled preferentially. • Trees should be sampled in the most active portion of the slope. • Summer rainfall is the main driver of rockfalls at our site. To overcome the lack of historical archives at active rockfall environments, dendrogeomorphic techniques have been used extensively on forested slopes since the early 2000s and several approaches developed to extract rockfall signals from tree-ring records. Given the unpredictable nature of rockfall, these reconstructions are, in principle, of great help when it comes to relate fluctuations in rockfall activity to meteorological variables. Yet, so far, dendrogeomorphic time series were only rarely compared with meteorological records. Here, we ascribe this shortfall to the absence of clear guidelines on how to optimize the sampling strategy. In order to test this hypothesis, we capitalize on the extensive dataset of rockfall impacts recorded in trees growing in a mixed forest plot within the French Alps. We designed six different scenarios retrospectively and compared rockfall reconstructions with meteorological records. Our results demonstrate that reconstructions that include trees located in the most active segments of the plot (i.e. close to the cliff and over periods lacking multidecadal trends in the reconstruction) capture summer precipitation as the main driver of rockfall activity more clearly. This result is in line with monitoring studies from calcareous cliffs in the Alps located outside periglacial environments thus confirming the robustness of our approach. [ABSTRACT FROM AUTHOR]

Equisetites spatulatus Zeiller, 1895 is only found in Late Carboniferous deposits in France. The uninervous leaves with spatulate shaped tip forming a sheath are the only characters used to define this species. We consider the isolated incomplete, leaf sheath with rarely preserved spatulate shaped tips on which the diagnosis is based, a too poor argument to maintain E. spatulatus as a valid species. New samples and two syntypes were examined and allowed to provide a new description and illustrations. Nevertheless, at the present time, the peculiar leaves cannot be attributed with great certainty to any other Equisetophyta nor to other group. Damages due to taphonomy may explain the different forms of leaves on the specimens. The validity of other Carboniferous Equisetites can also be discussed on the base of the same assumptions. [ABSTRACT FROM AUTHOR]

Investigation of Holocene extents of mountain glaciers along with the related naturally-driven climate conditions helps improve our understanding of glacier sensitivity to ongoing climate change. Here, we present the first Holocene glacial chronology in the Mont-Blanc massif (Argentière glacier) in the French Alps, based on 25 in situ -produced cosmogenic 10Be dates of moraines and glacial bedrocks. The obtained ages from mapped sequences of moraines at three locations reveal that the glacier retreated from its Lateglacial extent and oscillated several times between ∼11.7 ka and ∼10.4 ka, i.e. during the Younger Dryas/Early Holocene (YD/EH) transition, before substantially retreating at ∼10.4 ka. Climate conditions corresponding to the past extents of Argentière glacier during the YD/EH transition (∼11 ka) and the Little Ice Age (LIA) were modelled with two different approaches: by determining summer temperature differences from reconstructed ELA-rises and by using a Positive Degree Day (PDD) mass-balance model. The ELA-rise reconstructions yield a possible range of temperatures for the YD/EH transition that were lower by between 3.0 and 4.8 °C compared to the year 2008, depending on the choice of the ELA sensitivity to temperature. The results from the PDD model indicate temperatures lower by ∼3.6–5.5 °C during the YD/EH transition than during the 1979–2002 period. For the LIA, our findings highlight the role of local precipitation changes, superimposed on the dominant temperature signal, in the detailed evolution of the glacier. Overall, this study highlights the challenge that remains in accurately inferring paleoclimate conditions from past glacier extents. • Argentière glacier oscillated 5 times between 11.7 ka and 10.5 ka. • Modeled Early Holocene temperature range is 3.6–5.5 °C below modern values. • Local precipitation changes explain detailed Little Ice Age glacier fluctuations. [ABSTRACT FROM AUTHOR]