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Key message: This article presents ring width chronologies derived from samples extracted from historical timber buildings in the French central Pyrenees. Two chronologies for fir (Abies alba Mill.) were dated for two periods: 1446–1655 and 1679–1952 AD. These chronologies are suitable for dendroarchaeological and paleoenvironmental studies, or for reconstructing past climates. Dataset access is at https://doi.org/10.48579/PRO/KH6HPC and associated metadata at https://metadata-afs.nancy.inra.fr/geonetwork/srv/fre/catalog.search#/metadata/edba546e-3769-4f06-959b-f0d8db7fbcdb. [ABSTRACT FROM AUTHOR]

Key message This article presents ring width chronologies derived from samples extracted from historical timber buildings in the French central Pyrenees. Two chronologies for fir (Abies alba Mill.) were dated for two periods: 1446–1655 and 1679–1952 AD. These chronologies are suitable for dendroarchaeological and paleoenvironmental studies, or for reconstructing past climates. Dataset access is at https://doi.org/10.48579/PRO/KH6HPC and associated metadata at https://metadata-afs.nancy.inra.fr/geonetwork/srv/fre/catalog.search#/metadata/edba546e-3769-4f06-959b-f0d8db7fbcdb .

Context: Treeline-ecotone spatial patterns and their dynamics reflect underlying processes. Changes in ecotone pattern may reflect changes in natural drivers or land-use practices. However, characterizing these dynamics presents a major challenge, limiting our ability to map, understand and predict changes in the upper limits of mountain forests. Objective: This paper proposes a new method using multiple pattern dimensions to describe treeline-ecotone spatial pattern shifts. This standardized protocol should be able to (i) distinguish different types of treeline-ecotone patterns within a large study area, (ii) characterize temporal pattern shifts in spatial pattern between two or more dates. Method: We mapped alpine treeline ecotones (ATE) at 648 sites in the eastern French Pyrenees using aerial images from ~ 1955 and ~ 2015, identifying forest and non-forest areas at the hillslope scale. Extracted patch metrics were summarized using a Principle Component Analysis (PCA) and spatial pattern change was quantified from the shift in the PCA space and compared to elevational shifts. Results: Three clusters of patterns were distinguished: diffuse, discrete and island-forming ATEs. Between 1955 and 2015, about half of the sites changed from one pattern cluster to another. Shifts into discrete ATEs were associated with smaller and negative elevational shifts, while shifts into diffuse ATEs coincided with the highest positive elevational shifts. Conclusion: The proposed method allows a standardized and repeatable quantification of vegetation pattern change in alpine treeline ecotones based on historical aerial imagery. Seeing the importance of treeline-ecotone shifts for alpine biodiversity, we encourage the use of this protocol to better understand treeline dynamics at treelines globally. [ABSTRACT FROM AUTHOR]

Abstract In a conservation and sustainable management perspective, we identify the ecological, climatic, and demographic factors responsible for the genetic diversity patterns of the European silver fir (Abies alba Mill.) at its southwestern range margin (Pyrenees Mountains, France, Europe). We sampled 45 populations throughout the French Pyrenees and eight neighboring reference populations in the Massif Central, Alps, and Corsica. We genotyped 1,620 individuals at three chloroplast and ten nuclear microsatellite loci. We analyzed within‐ and among‐population genetic diversity using phylogeographic reconstructions, tests of isolation‐by‐distance, Bayesian population structure inference, modeling of demographic scenarios, and regression analyses of genetic variables with current and past environmental variables. Genetic diversity decreased from east to west suggesting isolation‐by‐distance from the Alps to the Pyrenees and from the Eastern to the Western Pyrenees. We identified two Pyrenean lineages that diverged from a third Alpine–Corsica–Massif Central lineage 0.8 to 1.1 M years ago and subsequently formed a secondary contact zone in the Central Pyrenees. Population sizes underwent contrasted changes, with a contraction in the west and an expansion in the east. Glacial climate affected the genetic composition of the populations, with the western genetic cluster only observed in locations corresponding to the coldest past climate and highest elevations. The eastern cluster was observed over a larger range of temperatures and elevations. All demographic events shaping the current spatial structure of genetic diversity took place during the Mid‐Pleistocene Transition, long before the onset of the Holocene. The Western Pyrenees lineage may require additional conservation efforts, whereas the eastern lineage is well protected in in situ gene conservation units. Due to past climate oscillations and the likely emergence of independent refugia, east–west oriented mountain ranges may be important reservoir of genetic diversity in a context of past and ongoing climate change in Europe.

In a conservation and sustainable management perspective, we identify the ecological, climatic, and demographic factors responsible for the genetic diversity patterns of the European silver fir (Abies alba Mill.) at its southwestern range margin (Pyrenees Mountains, France, Europe). We sampled 45 populations throughout the French Pyrenees and eight neighboring reference populations in the Massif Central, Alps, and Corsica. We genotyped 1,620 individuals at three chloroplast and ten nuclear microsatellite loci. We analyzed within‐ and among‐population genetic diversity using phylogeographic reconstructions, tests of isolation‐by‐distance, Bayesian population structure inference, modeling of demographic scenarios, and regression analyses of genetic variables with current and past environmental variables. Genetic diversity decreased from east to west suggesting isolation‐by‐distance from the Alps to the Pyrenees and from the Eastern to the Western Pyrenees. We identified two Pyrenean lineages that diverged from a third Alpine–Corsica–Massif Central lineage 0.8 to 1.1 M years ago and subsequently formed a secondary contact zone in the Central Pyrenees. Population sizes underwent contrasted changes, with a contraction in the west and an expansion in the east. Glacial climate affected the genetic composition of the populations, with the western genetic cluster only observed in locations corresponding to the coldest past climate and highest elevations. The eastern cluster was observed over a larger range of temperatures and elevations. All demographic events shaping the current spatial structure of genetic diversity took place during the Mid‐Pleistocene Transition, long before the onset of the Holocene. The Western Pyrenees lineage may require additional conservation efforts, whereas the eastern lineage is well protected in in situ gene conservation units. Due to past climate oscillations and the likely emergence of independent refugia, east–west oriented mountain ranges may be important reservoir of genetic diversity in a context of past and ongoing climate change in Europe. [ABSTRACT FROM AUTHOR]

The bearded vulture (Gypaetus barbatus) is listed as vulnerable in Europe on the International Union for Conservation of Nature Red List because of population declines over multiple generations. Vulture population declines have been attributed to shooting, use of toxicants, and changes in land use, which have resulted in habitat degradation and increased anthropogenic disturbances. Concomitantly, conservation authorities have restricted practices deemed harmful to the species and have established protection buffers around occupied vulture breeding sites to mitigate the impacts of anthropogenic disturbances on breeding success. Comor et al. (2019) compared bearded vulture breeding success over 6 years within and outside areas with restricted activities in the western French Pyrenees and assessed distances between vultures and hunting parties. They concluded that hunting was not a threat to species conservation and may even benefit vultures by providing alternative food resource. We dispute the conclusions of Comor et al. (2019) and present concerns about the data used, the study design, and the inferences taken from some of the data presented. Herein we provide arguments and rationale to support our opinion. [ABSTRACT FROM AUTHOR]

To date, the large-scale distribution of the endangered Pyrenean desman, Galemys pyrenaicus, has been related to various abiotic factors (e.g. riverbed and riverbank characteristics, hydrology, topography, climate). However, none could fully explain the recent observed range contraction of the species, suggesting the influence of other drivers. In this study, the potential effect of some unexplored variables on the Pyrenean desman presence was investigated at the local scale (i.e. stream reaches) in the French Pyrenees. They described not only the riverbed, riverbanks, water chemistry, topography and pedology but also the presence of potential interacting species. Generalised linear models were implemented to select the best drivers of the Pyrenean desman presence. Our results stressed the relevance of considering human impacts at the riverbed scale, river narrowing and water chemistry to explain the local distribution of the Pyrenean desman. The presence of two potential competitors, the Eurasian water shrew Neomys fodiens and the dipper Cinclus cinclus, was also highly correlated to the species presence in stream reaches. This suggests that all three species may use the same resources within streams, which could be a potential source of competitive interactions. This study not only highlights the importance of maintaining the riverbed integrity for the Pyrenean desman but also stresses the need to assess the extent to which biotic interactions may affect its distribution in order to understand its current decline. [ABSTRACT FROM AUTHOR]

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ABSTRACT Aim Small (< 1 km2) alpine glaciers are likely to disappear in this century, resulting in decreased regional habitat heterogeneity in associated streams. Both heterogeneity within and spatial isolation among glacier-influenced streams can enhance beta diversity of stream-dwelling organisms. We measured beta at both community and population-genetic levels within and among streams currently influenced by small Pyrenean glaciers. We aimed to evaluate whether patterns are analogous between the two levels, to apply various approaches for characterizing beta, and to infer the outcome of future glacier loss on regional biodiversity. Location Four glacier-fed basins in the Parc National des Pyrénées, France. Methods We classified each of 18 stream reaches across the basins into either high-, mid- or low-'glaciality' (glacial influence) groups according to four physicochemical characteristics. At each reach, we collected macroinvertebrate communities and evaluated mitochondrial DNA haplotypes for 11-13 individuals of Baetis alpinus Pictet. Using taxa/haplotypes as basic units, we evaluated community and population-genetic beta diversity simultaneously. We measured beta diversity in three major ways: as multivariate (Sørensen's dissimilarity, Jost D) and 'classical' (gamma/alpha) variation to compare among glaciality groups, and as turnover along the glaciality gradient within each basin. Results For most approaches at both organizational levels, beta was greatest among high-glaciality reaches, absolute values of variation of beta in high-glaciality streams were strikingly similar between levels, and the steepest turnover within basins occurred between high- and mid-glaciality reaches. Therefore, high-glaciality reaches contained assemblages and populations that were unique both within that stream type (among basins) and compared with other stream types within basins. Main conclusions Parallel beta diversity patterns at population-genetic and community levels suggested that environmental drivers influence these levels analogously. Extreme conditions (e.g. low temperature, high instability, isolation) in high-glaciality streams probably enhance beta at both levels. Stream beta diversity is likely to decrease substantially with continued glacial reduction in this system. [ABSTRACT FROM AUTHOR]

The genus Kobayasiella includes species difficult or even impossible to identify in LM. Only EM allows observation of the ultrastructural features helping in diagnostic species circumscription. Recent surveys of the epilithic diatoms in the running waters of Reunion Island led to the discovery of a new species, K. bebourensis. This species differs from all previously described ones by the uniseriate striae composed of areolae occluded by a cribrum. Besides, two other species, the so rarely recorded K. jaagii (F. Meister) Lange-Bert. and K. micropunctata (H. Germ.) Lange-Bert., were collected in two alpine lakes of the French Pyrenees. K. jaagii lacks an umbilicus in the raphe, which is considered one of the most important diagnostic criterions of the genus. However, this species shows a combination of characteristics including it within the genus Kobayasiella. K. micropunctata is a typical representative of the genus Kobayasiella matching all the ultrastructural features of the genus. K. bebourensis and K. micropunctata have a cingulum composed of at least three connecting bands. [ABSTRACT FROM AUTHOR]

The genus Kobayasiella includes species difficult or even impossible to identify in LM. Only EM allows observation of the ultrastructural features helping in diagnostic species circumscription. Recent surveys of the epilithic diatoms in the running waters of Reunion Island led to the discovery of a new species, K. bebourensis. This species differs from all previously described ones by the uniseriate striae composed of areolae occluded by a cribrum. Besides, two other species, the so rarely recorded K. jaagii (F. Meister) Lange-Bert. and K. micropunctata (H. Germ.) Lange-Bert., were collected in two alpine lakes of the French Pyrenees. K. jaagii lacks an umbilicus in the raphe, which is considered one of the most important diagnostic criterions of the genus. However, this species shows a combination of characteristics including it within the genus Kobayasiella. K. micropunctata is a typical representative of the genus Kobayasiella matching all the ultrastructural features of the genus. K. bebourensis and K. micropunctata have a cingulum composed of at least three connecting bands. [ABSTRACT FROM AUTHOR]

Expected consequences of global warming include habitat reduction in many cool climate species. Rock ptarmigan is a Holarctic grouse that inhabits arctic and alpine tundra. In Europe, the Pyrenean ptarmigan inhabits the southern edge of the species' range and since the last glacial maximum its habitat has been severely fragmented and is restricted to high-alpine zones or ‘sky islands’. A recent study of rock ptarmigan population genetic in Europe found that the Pyrenean ptarmigan had very low genetic diversity compared with that found in the Alps and Scandinavia. Habitat fragmentation and reduced genetic diversity raises concerns about the viability of ptarmigan populations in the Pyrenees. However, information on population structuring and gene flow across the Pyrenees, which is essential for designing a sound management plan, is absent. In this study, we use seven microsatellites and mitochondrial control region sequences to investigate genetic variation and differentiation among five localities across the Pyrenees. Our analyses reveal the presence of genetic differentiation among all five localities and a significant isolation-by-distance effect that is likely the result of short dispersal distances and high natal and breeding philopatry of Pyrenean ptarmigan coupled with severe habitat fragmentation. Furthermore, analysis of molecular variance, principal component analysis and Bayesian analysis of genetic structuring identified the greatest amount of differentiation between the eastern and main parts of the Pyrenean chain separated by the Sègre Valley. Our data also show that the Canigou massif may host an isolated population and requires special conservation attention. We propose a management plan which includes the translocation of birds. If a sky island structure affects genetic divergence in rock ptarmigan, it may also affect the genetic structure of other sky island species having low dispersal abilities. [ABSTRACT FROM AUTHOR]

The article provides information on a study that demonstrated the complexity of multi-scale thermal variability in an alpine environment. It examines the extent of thermal heterogenecity in an alpine river system with minimal human modification and reports on a detailed, high-resolution study of water column temperature at 29 sites from the Taillon-Gabiétous river basin, French Pyrénées. It also characterizes stream temperature dynamics at nested spatial scales and determines the key hydrometeorological and basin characteristics influencing stream temperature.

Climate change poses a considerable threat to the biodiversity of high latitude and altitude ecosystems, with alpine regions across the world already showing responses to warming. However, despite probable hydrological change as alpine glaciers and snowpacks shrink, links between alpine stream biota and reduced meltwater input are virtually unknown. Using data from the French Pyrénées, we demonstrate that taxonomic richness and total abundance of stream macroinvertebrates increase significantly as meltwater (snow melt and glacier melt) contributions to river flow decrease. Macroinvertebrate species showed a gradation of optimum meltwater conditions at which they persist. For example: Habroleptoides berthelemyi (Ephemeroptera), Perla grandis (Plecoptera) and Rhithrogena spp. (Ephemeroptera) increased in abundance when meltwater contributions to streamflow decrease, whereas in contrast, Rhyacophila angelieri (Trichoptera) and Diamesa latitarsis spp. (Diptera) decreased in abundance. Changes in alpine stream macroinvertebrate community composition as meltwater contributions decline were associated with lower suspended sediment concentration, and higher water temperature, electrical conductivity and pH. Our results suggest α diversity (at a site) of streams presently fed by meltwaters will increase with future meltwater reductions. However, β diversity (between-sites) will be reduced as snow melt and glacier melt decrease because the habitat heterogeneity associated with spatiotemporal variability of water source contributions will become lower as meltwater contributions decline. Extinction of some endemic alpine aquatic species (such as the Pyrenean caddis fly R. angelieri) is predicted with reduced meltwater inputs, leading to decreases in γ diversity (region). Our identification of significant links between meltwater production and stream macroinvertebrate biodiversity has wider implications for the conservation of alpine river ecosystems under scenarios of climate change induced glacier and snowpack loss. [ABSTRACT FROM AUTHOR]

1. Spatial and temporal variability of relative snow-melt, glacier-melt and groundwater contributions to streams play important roles in shaping alpine freshwater ecosystems. Although meltwater (particularly glacier-fed) streams have received much attention in recent years, the influence of groundwater on alpine freshwater ecosystems remains poorly understood. 2. This study tested the hypotheses that increased groundwater contributions to meltwater-dominated alpine streams would yield increases in water temperature, channel stability, electrical conductivity and particulate organic matter (POM) and decreases in suspended sediment concentration (SSC). These more favourable habitat conditions were hypothesised to result in increased macroinvertebrate abundance and diversity. 3. Groundwater contributions, physicochemical habitat variables and benthic macroinvertebrates were sampled throughout the 2002 and 2003 summer-melt seasons in three streams in the French Pyrénées. 4. Increased groundwater contributions were significantly correlated with higher discharge, water temperature, electrical conductivity, POM and channel stability, but lower SSC. 5. Macroinvertebrate total abundance, taxonomic richness, number of Ephemeroptera, Plecoptera and Trichoptera genera, and per cent Plecoptera all increased significantly with greater groundwater contributions to streamflow. However, beta diversity and Trichoptera relative abundance decreased. 6. Abundance of most macroinvertebrate taxa was highest under groundwater-dominated conditions but a gradient of optimum groundwater preferences was evident across all taxa. Some taxa were found only where groundwater contributions were low (i.e. in predominantly meltwater-fed streams). 7. This study provides evidence that water source, physicochemical habitat and stream biota are strongly linked. Therefore, an interdisciplinary approach is necessary for future studies aiming to develop conservation strategies or predict the response of alpine river ecosystems to global climate change. [ABSTRACT FROM AUTHOR]

Abstract: Few detailed studies of thermal dynamics exist for alpine river systems despite their high climatic sensitivity. This paper examines water column temperatures (15min resolution) for snowmelt/glacier-fed streams and groundwater tributaries in the French Pyrénées. Streambed temperatures were monitored at: (1) the Taillon Glacier stream, (2) the Tourettes groundwater-fed tributary, and (3) the Taillon glacier stream downstream of the confluence with (2). Stream temperatures were analysed with reference to hydrological (snowline altitude, glacial ice exposure and river discharge) and climatological (air temperature, incident short-wave radiation and precipitation) data to infer key processes driving thermal variability. Mean water column temperature increased by 7°C in 2002, and 8.6°C in 2003, over a distance of 1km from the Taillon Glacier snout. Groundwater springs punctuated longitudinal glacial stream thermal patterns by decreasing (karstic) and increasing (hillslope) temperatures. Bed temperatures at all depths were coldest (warmest) and most (least) variable for the Taillon (Tourettes) stream. Stream temperatures varied at sub-seasonal time-scales. In particular, extreme precipitation events decreased temperatures in the Taillon Glacier stream by up to 10°C in the water column and 0.05m depth, 7.5°C at 0.20m depth and 5°C at 0.40m depth. Key drivers of thermal variability were: (1) dynamic water source contributions (i.e. snowmelt, ice-melt and groundwater), (2) proximity to source, and (3) prevailing hydroclimatological conditions. The variability of water column and streambed temperatures indicates alpine river basins to be highly thermally heterogeneous. [Copyright &y& Elsevier]

Macroinvertebrate communities in alpine streams have rarely been examined over more than two consecutive years or at sub-monthly temporal resolution during the summer melt season, in relation to a range of stream physicochemical habitat measurements. This paper addresses these research gaps by investigating the inter- (late melt season, 1996–2003) and intra-annual (bi-weekly; June–September, 2002–2003) community compositional stability and persistence of three alpine streams fed from different water sources (snow, glaciers and groundwater) in the Taillon–Gabiétous catchment, French Pyrénées. Inter-annual community stability and persistence decreased from 1996 to 2003; however, groundwater stream communities changed less than those in the main glacial stream. Intra-annual community stability varied spatially and temporally, particularly in relation to water quality variables (water temperature and suspended sediment concentration); water quantity (stream discharge) was less important perhaps due to taxa possessing adaptations to flow variability. The 15 most abundant taxa were consistently more stable and persistent than the entire stream community suggesting a common pool of taxa in these streams. Overall, the results support the view that streams originating from different alpine water sources are characterised by distinct benthic macroinvertebrate assemblages, and demonstrate the value of sampling at nested temporal scales (inter-annual to bi-weekly) for understanding how these stream ecosystems function. [ABSTRACT FROM AUTHOR]

1. This paper presents a framework for the analysis of glacial stream ecosystems based upon the hierarchy of physical processes that operate over timescales varying from diel to millennial. Linked conceptual models propose interrelationships between climate, hydrology and fluvial geomorphology in alpine catchments. 2. These conceptual models are illustrated using data from the Taillon/Gabiétous catchment, French Pyrénées. Secondary sources provide information concerning the long-term sequence of climatic and geomorphological controls on contemporary catchment processes. Detailed hydrogeomorphological field data collected over three consecutive summer melt seasons (1995–97) permit identification of marked changes in shorter-term (diel, seasonal and inter-annual) physical processes. 3. Clear differences in the response of water quality and quantity variables were observed between years as climatic conditions varied. In two of the three study years, a precipitation-driven regime was imposed upon the typical ablation-driven river discharge pattern in alpine streams. Clear changes in water quality and quantity were evident with increasing distance from the glacier: (i) discharge increased although specific discharge decreased markedly, (ii) the mean and variability in water temperature increased, and (iii) base concentrations of suspended solids decreased. 4. The physical processes incorporated in the conceptual models presented in this paper have ecological implications because they underpin a nested suite of disturbance regimes operating over timescales from diel to millennial. [ABSTRACT FROM AUTHOR]

Detailed palynological studies in two adjoining French Pyrenean valleys, complemented by the study of archives, demonstrate that under similar climatic conditions, the forest history of each valley from the Bronze Age to present time was essentially determined by socio-economical constraints, possibly modified by natural characteristics such as topography. The studies show why the expansion of Fagus (beech) at c. 4000 B.P. was asynchronous on the northern slope of the Pyrenees and emphasize the effects of the human impact on the recent lowering of the tree-line. [ABSTRACT FROM AUTHOR]

This paper advances an objective method of diurnal hydrograph classification as an aid to exploring changes in the hydrological functioning of glacierized catchments over the ablation season. The temporal sequencing of different hydrograph classes allows identification of seasonal evolution in hydrograph form and also assists delimitation of hydrologically-meaningful time periods of similar diurnal discharge response. The effectiveness of this approach is illustrated by applying it to two contrasting summer discharge records for a small cirque basin. By comparing the results with patterns of surface energy receipt and glacier ablation, the seasonally transient relative influences of: (i) surface meltwater production and (ii) meltwater routing and storage conditions within the intervening glacier drainage system in determining runoff are elucidated. The method successfully characterizes distinct seasonal-scale changes in the diurnal outflow hydrograph during the ablation-dominated 1995 melt season but is also able to reveal underlying trends and short-term fluctuations in the precipitation-dominated, poorly ablation-regulated 1996 melt season. The limitations and benefits of this hydrograph classification technique are evaluated. [ABSTRACT FROM AUTHOR]

The genus Kobayasiella includes species difficult or even impossible to identify in LM. Only EM allows observation of the ultrastructural features helping in diagnostic species circumscription. Recent surveys of the epilithic diatoms in the running waters of Reunion Island led to the discovery of a new species, K. bebourensis. This species differs from all previously described ones by the uniseriate striae composed of areolae occluded by a cribrum. Besides, two other species, the so rarely recorded K. jaagii (F. Meister) Lange-Bert. and K. micropunctata (H. Germ.) Lange-Bert., were collected in two alpine lakes of the French Pyrenees. K. jaagii lacks an umbilicus in the raphe, which is considered one of the most important diagnostic criterions of the genus. However, this species shows a combination of characteristics including it within the genus Kobayasiella. K. micropunctata is a typical representative of the genus Kobayasiella matching all the ultrastructural features of the genus. K. bebourensis and K. micropunctata have a cingulum composed of at least three connecting bands., (© 2012 Phycological Society of America.)