Subalpine Basin Research Articles

Assessment of Individual-Level Exposure to Airborne Particulate Matter during Periods of Atmospheric Thermal Inversion.

Air pollution exposure is harmful to human health and reducing it at the level of an individual requires measurements and assessments that capture the spatiotemporal variability of different microenvironments and the influence of specific activities. In this paper, activity-specific and general indoor and outdoor exposure during and after a period of high concentrations of particulate matter (PM), e.g., an atmospheric thermal inversion (ATI) in the Ljubljana subalpine basin, Slovenia, was assessed. To this end, personal particulate matter monitors (PPM) were used, worn by participants of the H2020 ICARUS sampling campaigns in spring 2019 who also recorded their hourly activities. ATI period(s) were determined based on data collected from two meteorological stations managed by the Slovenian Environmental Agency (SEA). Results showed that indoor and outdoor exposure to PM was significantly higher during the ATI period, and that the difference between mean indoor and outdoor exposure to PM was much higher during the ATI period (23.0 µg/m3) than after (6.5 µg/m3). Indoor activities generally were associated with smaller differences, with cooking and cleaning even having higher values in the post-ATI period. On the other hand, all outdoor activities had higher PM values during the ATI than after, with larger differences, mostly >30.0 µg/m3. Overall, this work demonstrated that an individual-level approach can provide better spatiotemporal resolution and evaluate the relative importance of specific high-exposure events, and in this way provide an ancillary tool for exposure assessments.

USE OF THE SSIB4/TRIFFID MODEL COUPLED WITH TOPMODEL TO INVESTIGATE THE EFFECTS OF VEGETATION AND CLIMATE ON EVAPOTRANSPIRATION AND RUNOFF IN A SUBALPINE BASIN OF SOUTHWESTERN CHINA

It is important to understand the response of vegetation dynamics and surface water budget to the changing climate. To investigate the effects of vegetation and climate change on evapotranspiration and runoff on a basin scale, the SSiB4T/TRIFFID (SSiB4/TRIFFID coupled with TOPMODEL) is used to perform long-term dynamic simulations of vegetation succession and the water balance under different climate scenarios for a subalpine basin. The results of all experiments show that fraction of vegetation changes from a dominance of C3 grasses to tundra shrubs and then gradually approaches equilibrium with a dominance of forests. Change to evapotranspiration is very sensitive to temperature changes but is not sensitive to precipitation changes when the temperature remains unchanged. Runoff is very sensitive to changes in both temperature and precipitation. In the increase of temperature, evapotranspiration of forests increases the most among the three vegetation types. From the control run to the [T+5, (1+40%)P] run (A temperature increase of 5 °C, an increase in precipitation of 40%), the role of forests in increasing runoff changes to a reduction in runoff.

The middle-late Aalenian event: A precursor of the Mesozoic Marine Revolution

The Aalenian was a time marked by profound environmental and carbon cycle changes. Still, the scarcity of detailed studies hinders a better understanding of the triggering mechanisms and the larger-scale context of Lower to Middle Jurassic environmental perturbations. This study provides an unprecedented high-resolution biostratigraphically well-constrained carbon isotope record (δ13Corg and δ13Ccarb) for the upper Toarcian–lower Bajocian interval of two expanded limestone-marl alternation successions in France (French Subalpine Basin) and Chile (Andean Basin). The comparison with available records from the Tethyan and Boreal domains highlights that medium-term carbon isotope fluctuations are reproducible across different palaeoceanographic settings from both hemispheres, providing for the first time compelling evidence for recurrent perturbations of the global carbon cycle during the Aalenian. Combined with a review of geological events, climate modes, abundance and diversity of major fossil groups, and trophic conditions inferred from the calcareous nannofossil record, our study fills the gap in our understanding of global environmental changes in a so-far poorly documented Middle Jurassic stage, intercalated between the early Toarcian Oceanic Anoxic Event and the early Bajocian carbonate crisis. Importantly, this compilation indicates that the Aalenian was a pivotal time interval of environmental perturbations, likely triggering the Mesozoic Marine Revolution.

Testing the effects of incorporating TOPMODEL into the SSiB4/TRIFFID model and simulation of the response of vegetation dynamics and surface water cycle to climate changes in a subalpine basin of southwestern China

AbstractTo investigate the response of vegetation dynamics and surface water budget to climate change on a basin scale, the biophysical/dynamic vegetation model SSiB4/TRIFFID was coupled with TOPMODEL (hereinafter referred to as SSiB4T/TRIFFID). The effects of the integration on hydrological simulations were examined and long‐term dynamic simulations of vegetation succession and the water–carbon balance were performed under different climate scenarios for a subalpine basin of southwestern China using SSiB4T/TRIFFID. The coupled model SSiB4T/TRIFFID produces higher soil wetness and evapotranspiration, lower total run‐off and more realistic partitioning of discharges between surface run‐off and base flow. All long‐term simulations for the subalpine basin show that the fraction of vegetation changes from a dominance of C3 grasses to tundra shrubs and then to forests. Annual evapotranspiration in the control run is 388.5 mm year−1 (dominance of C3 grasses), 445.3 mm year−1 (dominance of tundra shrubs) and 388.1 mm year−1 (dominance of forests). Under an increase in temperature by 5°C and in precipitation by 40%, the evapotranspiration of forests is the highest among the three vegetation types. In the humid region, Forest evapotranspiration increases the most with increases in temperature, which results in the role of forests in increasing run‐off changing to having no significant effect on run‐off, and then to reducing run‐off. In regions with water limitation, forest evapotranspiration increases the most as precipitation increases. The effect of forests in reducing run‐off increases with increased precipitation. The spatial variation in the climate exerts an important impact on spatial changes in forest–run‐off relationships.

Habitat Influence on the Molecular, Carbon and Hydrogen Isotope Compositions of Leaf Wax n-Alkanes in a Subalpine Basin, Central China

Epidermal leaf waxes of terrestrial higher plants have been widely utilized for the reconstructions of paleoenvironment and paleoclimate in peat deposits. In this study, specimens of four plant species growing in both peatland and non-peatland habitats were retrieved to compare their molecular, carbon (δ13C) and hydrogen (δ2H) isotopic compositions of leaf wax n-alkanes from a closed subalpine basin in Central China. Three of the four species show quite higher total concentrations of n-alkanes in the relatively dry non-peatland setting than in the peatland. In addition, the δ2H values of long-chain n-alkanes are generally less depleted in the peatland and are comparable among different plant species, which is interpreted as the influence of inundation condition and the possible limited supply of photosynthetic products. This study reveals different patterns of plant wax molecular and isotopic compositions between peatland and the surrounding non-peatland conditions, and confirms the paleoenvironmental potential of leaf wax ratios on the peat sequences.

Organic matter deposition and paleoenvironmental implications across the Cenomanian-Turonian boundary of the Subalpine Basin (SE France): Local and global controls

The Cenomanian-Turonian boundary is marked by global sea-level highstands and one of the warmest periods of the Mesozoic, with high pCO2 levels linked to a massive magmatic episode. This is associated with the establishment of a worldwide marine anoxia, the deposition of organic-rich facies and disturbances of the global carbon cycle, the so-called Oceanic Anoxic Event 2 (OAE2). The Pont d'Issole section's (Subalpine Basin, SE France) sedimentary succession represents the reference record of OAE2 in the Tethyan domain, although its organic fraction is extremely poorly studied. Therefore, the main objectives of this study are the characterization of the Pont d'Issole section's organic matter (OM) for paleoenvironmental interpretation and the assessment of the OM thermal maturity using organic petrology and organic geochemistry techniques.The organic record characterizes a shallowing-up marine system with varying redox and restriction conditions, associated with periods of stratified oxygen regimen. It displays the presence of two OM enrichment episodes with different paleoenvironmental and geodynamic contexts. The first OM enrichment episode (Unit Th1) is thought to be associated with the global mechanisms that trigger OAE2 and is characterized by a palynofacies association co-dominated by amorphous OM and marine microplankton, reflecting a context of high sea-level. This is followed by the Plenus Cold Event (Unit Th2), characterized by a decrease in amorphous OM and increase in marine microplankton, representing a reoxygenation associated with an increase in water level, and an apparent decrease in temperature (disappearance of Classopollis sp.). The second OM enrichment episode (Unit Th3 and base of Unit Th4) is characterized by an association dominated by amorphous OM, the occurrence of freshwater microplankton, and the development of a restricted environment with low sea level. These depositional conditions are thought to be connected to the beginning phases of basin closure, promoted by the regional tectonic framework (compressive trend between Africa and Europe).The molecular fraction showed the presence of unsaturated compounds, monoaromatic steranes, monoaromatic anthrasteroids and the biological ββ hopanes, indicating a low thermal evolution for the OM. This is corroborated by biomarkers ratios and organic petrographic data, namely vitrinite reflectance (0.29% Rr).The presence of Paleozoic reworked OM in the samples was also identified presenting a more complex thermal history than the Cretaceous OM. This OM is possibly related to the subaerial erosion of Hercynian Massifs.

Identifying persistent temperature inversion events in a subalpine basin using radon-222

Abstract. One year of meteorological and atmospheric radon observations in a topographically complex subalpine basin are used to identify persistent temperature inversion (PTI) events. PTI events play a key role in public health due to the accumulation of urban pollutants that they cause. Two techniques are compared: a new radon-based method (RBM), based on single-height 222Rn measurements from a single centrally located station, and an existing pseudo-vertical temperature gradient method (TGM) based on observations from eight weather stations around the subalpine basin. The RBM identified six PTI events (four in winter, two in autumn), a subset of the 17 events identified by the TGM. The RBM was more consistent in its identification of PTI events for all seasons and more selective of persistent strongly stable conditions. The comparatively poor performance of the TGM was attributed to seasonal inconsistencies in the validity of the method's key assumptions (influenced by mesoscale processes, such as local drainage flows, nocturnal jets, and intermittent turbulence influence) and a lack of snow cover in the basin for the 2016–2017 winter period. Corresponding meteorological quantities for RBM PTI events (constituting 27 % of the autumn–winter cold season) were well characterized. PTI wind speeds in the basin were consistently low over the whole diurnal cycle (typically 0.2–0.6 m s−1). Suitability of the two techniques for air quality assessment was compared using hourly PM10 observations. Peak PM10 concentrations for winter (autumn) PTI events were underestimated by 13 µg m−3 (11 µg m−3) by the TGM compared with the RBM. Only the RBM indicated that nocturnal hourly mean PM10 values in winter PTI events can exceed 100 µg m−3, the upper threshold of low-level short-term PM10 exposure according to World Health Organization guidelines. The efficacy, simplicity, and cost effectiveness of the RBM for identifying PTI events has the potential to make it a powerful tool for urban air quality management in complex terrain regions, for which it adds an additional dimension to contemporary atmospheric stability classification tools. Furthermore, the long-term consistency of the radon source function will enable the RBM to be used in the same way in future studies, enabling the relative magnitude of PTI events to be gauged, which is expected to assist with the assessment of public health risks.

ROLE OF METEOROLOGY AND LITHOLOGY IN THE TEMPORAL VARIATION OF THE OUTDOOR RADON LEVEL.

The outdoor radon concentration was monitored together with the meteorological parameters at two contrasting complex topographies: sub-Alpine basin (SA) and sub-Mediterranean valley (SM) in winter (December 2017-February 2018) and summer (June-August 2018). The time series for each site and each season are evaluated in three different ways: (i) clear-sky and cloudy condition together, (ii) clear-sky conditions only (cloud cover <20%) and (iii) cloudy condition only (cloud cover >20%), and compared to the expected atmospheric boundary layer (ABL) 'mixing volume' caused by meteorological changes. The results have confirmed the sensitivity of diurnal and seasonal radon concentration to the expected ABL 'mixing volume' at the two selected sites. The relationship is more pronounced in calm clear-sky conditions. Cloudy conditions are associated with fast weather changes, when the ABL is well mixed and hourly mean radon concentrations do not follow the typical diurnal trend.

Carbon-isotope events during the Pliensbachian (Lower Jurassic) on the African and European margins of the NW Tethyan Realm

Early Jurassic palaeoenvironments and palaeoclimates, based on chemostratigraphy, have been extensively studied for the northern Tethyan margin. For the first time, high-resolution chemostratigraphy for the entire Pliensbachian is proposed for the African Tethyan margin (Morocco), and compared with new sections from the European Tethyan margin (France). Precise ammonite determinations, completed by calcareous nannofossil distribution, provide an accurate biostratigraphic framework from the Upper Sinemurian to the Upper Pliensbachian. Bulk inorganic carbon (δ13Ccarb) and organic carbon (δ13Corg) isotope signals are used to characterise and compare carbon-cycle trends in the Central High Atlas Basin (Amellago-Ikis section, Morocco), the Paris Basin (Montcornet borehole, France), and the Subalpine Basin (Serre-Poncon section, France). Comparison of this new dataset with previously published geochemical data from European basins confirms the existence of five distinct carbon-isotope events, synchronous at the scale of the NW Tethyan Realm: (1) a clear –2‰ negative excursion of δ13Ccarb and δ13Corg, corresponding to the Sinemurian–Pliensbachian Boundary Event (SPBE), probably associated with a massive release of light carbon by volcanism and hydrothermalism during the breakup of Pangea; (2) a positive excursion (+1 to +1.5‰) in the Valdani and Luridum subzones (Ibex Zone), reflecting increased organic matter storage under warm climate conditions; (3) a broadly negative event from the Davoei Zone to the lower part of the Margaritatus Zone, associated with major oceanographic reorganisation in a transgressive context, and possible enhanced hydrothermalism related to the opening of the Hispanic corridor; (4) a positive carbon excursion (+2‰) during the Subnodosus and Gibbosus subzones (Margaritatus Zone), corresponding to the Late Pliensbachian Event (LPE), associated with organic matter storage; (5) an end-Margaritatus–Spinatum negative excursion, associated with sea-level fall, probably driven by glacio-eustasy. This new high-resolution carbon-isotope dataset highlights the synchroneity of carbon-cycle trends throughout the NW Tethyan Realm. Several major isotopic events, prior to those of the Toarcian, must therefore have occurred at a supra-regional to global scale during the Pliensbachian, involving significant internal and external geodynamic mechanisms.

Structure and Composition of Subalpine Conifers in the Emerald Lake WATERSHED, Sequoia National Park, California

Abstract The Emerald Lake watershed forms a subalpine basin in the upper drainage of the Marble Fork of the Kaweah River in Sequoia National Park, California, with elevations ranging from 2804–3416 m. Five conifer species are present in the basin, with western white pine (Pinus monticola Douglas ex D. Don) as the most dominant species forming 71% of the stems and 82% of basal area censused in 1985 and 1986. Lodgepole pine (Pinus contorta Loudon subsp. murrayana (Grev. & Balf.) Critchf.) was the second most dominant in the watershed as measured by numbers of individuals and basal area, but was almost entirely restricted to mesic bench and wet meadow habitats in the lower elevations of the watershed. Foxtail pine (Pinus balfouriana Grev. & Balf.) comprised 9.5% of the stems and 13.7% of the basal area within the basin, but was largely present on higher north-facing ridgelines where it formed 52% of stems and 65% of basal area. Jeffrey pine (Pinus jeffreyi Grev. & Balf.), and red fir (Abies magnifica A. Murr...

The theory of island biogeography applies to ectomycorrhizal fungi in subalpine tree “islands” at a fine scale

AbstractThe theory of island biogeography, which predicts that species richness is a function of island size and distance from the mainland, is well tested with macro‐fauna and flora. Yet, in many ways, microbes are more appropriate for testing this and other ecological theories due to their small size and short generation times that translate to an ease of replication. We used a natural experimental system of isolated “host islands” to test the generality of the theory of island biogeography. Specifically, we tested whether ectomycorrhizal fungal (EMF) richness increased with tree size and decreased with distance from forest in a subalpine basin in Yosemite National Park for two congeneric pine species, Pinus albicaulis and Pinus contorta. We determined EMF richness with next‐generation sequencing, measured the size and age of each tree island (n = 40), and calculated geographic distances from each tree to the nearest forest edge. We found that EMF richness increased with island size (as measured by tree volume) and tree age for both pine species and decreased with distance from forest edge for P. albicaulis. Thus, we show the applicability of the theory to microbial symbionts in harsh, dry, and likely non‐equilibrium systems. In addition, we found that despite the fact that our tree islands had a mean age of 65 yr, a pioneer community of EMF dominated. We interpret this as evidence that water stress interacts with succession to create a sustained period of early‐stage fungi even in mature trees.

The Cenomanian–Turonian Boundary Event (CTBE) on the southern slope of the Subalpine Basin (SE France) and its bearing on a probable tectonic pulse on a larger scale

The Cenomanian–Turonian Boundary Event (CTBE) event is not associated with a transgression on the southern margin of the Subalpine Basin, but with a steady shallowing-up trend beginning in the lower half of the δ13C positive shift. The SW–NE Rouaine Fault had a complex role, first in isolating a black shale basin to the west and a large, deep submarine plateau devoid of black shale to the east, then by a strike-slip movement that induced a forced progradation to the north of the southern platform in the eastern compartment. This compressive tectonic reactivation of the southern margin began around the deposition of the local equivalent of the Plenus bed of boreal basins, as shown by correlation supported by both isotope and palaeontological data. Other local data are pieced together to suggest that the whole of SE France underwent a short-lived transpressive tectonic pulse around the Cenomanian–Turonian boundary, probably connected with the early compressive movement of Africa vs. Europe. On a larger scale, other published data suggest that this pulse could be a global one. It is coeval with renewed thrust loading, volcanism and transgression in the North-American Western Interior, local emergences during the event along the eastern Atlantic margin, suggesting a slight tendency to inversion of the margin, and a tilting to the east of the North-Africa plate that could explain the large transgression recorded from Morocco to Tunisia on the Saharan Craton.New isotope and palaeontological (coiling ratio of Muricohedbergella delrioensis) data from SE France suggest that two coolings of suprabasinal importance occurred just before and during the build-up of the d13C shift, including the boreal “Plenus Marls“, especially its middle limestone bed and its SE France equivalent.Regarding the extinction of the genus Thalmaninella and Rotalipora and during the event, neither anoxia nor climate changes can fully explain the palaeontological crisis, given that Rotalipora cushmani crosses the first phase of anoxia without harm, as well as the two coolings, not only in SE France but on a large scale, as shown by the correlation of the published data. This extinction needs alternative explanations as we challenge both anoxia and climate as major causes.

Pseudoteloceras, a new stephanoceratid genus (Ammonitida) of the lower Humphriesianum Zone (lower Bajocian, Middle Jurassic) from western Tethys

The new dimorphic genus Pseudoteloceras (type-species: P. crosillense gen. et sp. nov.) is defined within the subfamily Stephanoceratinae. It constitutes the terminal step of an early Bajocian phyletic trend that produces Teloceras-like morphologies throughout the lower Humphriesianum Zone of the western Mediterranean-Caucasian Subrealm, at an older chronological interval and with morpho-structural features that stand apart from those of the best known genus Teloceras of the uppermost Humphriesianum and lower Niortense zones at the early/late Bajocian transition. Three new species are described: P. croisillense, P. maerteni and P. boursicoti. Their biochronostratigraphical ranges are confirmed by the distribution in expanded sections of the Subalpine Basin in Submediterranean Province (Digne area) and the taphonomic analysis of fossil assemblages from the condensed sections of the “Oolithe ferrugineuse de Bayeux” Formation in Calvados, North West European Province. The biochronostratigraphical range of Pseudoteloceras gen. nov. is limited to the Romani Subzone, lower Humphriesianum Zone. P. crosillense gen. et sp. nov. marks a well-defined biohorizon of the upper Romani Subzone in the Digne stratigraphical successions. The extreme degree of the cadiconic morphology in the inner whorls of P. boursicoti gen. et sp. nov., and the biostratigraphical gap separating the first appearance of the genus Teloceras in the upper Humphriesianum Zone, support its erection as a new taxon Pseudoteloceras gen. nov. A fourth species, Pseudoteloceras geometricum (Maubeuge), is interpreted as the earliest species of this phyletic lineage, derived from Stemmatoceras and widely distributed through western Tethys in the lower Humphriesianum Zone.

The base-of-slope carbonate breccia system of Céüse (Tithonian, S-E France): Occurrence of progradational stratification in the head plug of coarse granular flow deposits

Once interpreted as a deep-water canyon infilling and later as some kind of tempestite deposit, the Tithonian breccias of Ceüse are here reinterpreted as a small lobe deposit, emplaced at the mouth of a gully cutting into a slope between two deep-water terraces in the eastern part of the subalpine basin. The breccias belong to two basic categories: mostly grain-supported and occasionally mud-supported. Spectacular large-scale oblique geometries (apparent lateral accretions) are observed in the grain-supported breccias, both within the infilling of the lower feeder channel and in the updip part of the lobe. Detailed analyses of these geometries show that they correspond to progradational features. Both laterally and in a more distal position on the lobe, these progradational bodies evolve into a pile of unsorted massive breccias, sometimes showing a crude, even stratification. We thus propose a depositional model for the grain-supported breccias, linking the two facies as follows: the deposition of a gravity flow begins at the toe-of-slope (mouth of the tributary gully) by a progradational head which evolves downslope and laterally to a splay of massive or crudely stratified breccia. The internal oblique stratification flattens distally over a distance of a few kilometres. Elementary beds pile up in morphological compensation to build the 100m thick breccia body of Céüse. Because the breccias are derived from the gravity-reworking of deep-water nodular carbonates, there is no sand-sized material available in the depositional system, or only a little probably produced through an erosive clast grain diminution process during transport. This explains why the thick breccia beds pass quickly eastward to thin-bedded mud turbidites.

Geostatistical Methods for Predicting Soil Moisture Continuously in a Subalpine Basin

This study presents spatial statistical methods for examining the distribution of soil moisture in a sub-alpine environment. The high local variability of soil moisture is not well characterized by spatial interpolation from dispersed data points. Interpolation using only field samples from Loch Vale, Rocky Mountain National Park, Colorado produced coarse estimates that followed mean soil moisture trends, but failed to capture local mid-slope variation. A properly specified regression model was identified by using dispersed field samples and ancillary data derived from Ikonos-2 and lidar data. This model predicted soil moisture patterns at a much finer spatial resolution. An intensive field campaign provided independent soil moisture measurements that were used to assess the model’s accuracy. The modeled soil moisture estimates captured local variability associated with topographic terrain differences along mid-slope areas.

Duration of the Early Bajocian and the associated δ 13 C positive excursion based on cyclostratigraphy

The Early Bajocian, about 172 Ma ago, was a period of tectonic changes, a global carbon-isotope positive excursion, and biological diversification of marine invertebrates (e.g. ammonites, radiolarians and coccolithophores). Unfortunately, both the duration of the Early Bajocian and the associated palaeoenvironmental changes are still poorly constrained. We propose here an estimate of the duration of this sub-stage based on a cyclostratigraphic analysis of the carbonate content from the Chaudon–Norante section, French Subalpine Basin, France. The Chaudon–Norante succession has been correlated with Les Dourbes section using greyscale variations to detect possible local hiatuses. The duration estimated here for the entire Early Bajocian is 4.082 Ma. Two intervals were identified in the positive δ 13 C excursion: an increase of carbon isotope values lasting 1.36 Ma and climax isotope values lasting for 2.72 Ma. A cooling at high latitudes and warming at low latitudes may have enhanced the Earth’s temperature gradient leading to an increase in humidity, which in turn triggered ocean eutrophication at the origin of the δ 13 C positive excursion. Supplementary material: The complete dataset presented in the paper, a colour version of the figure 8 and correlation of δ 13 C excursions between our studied site and contemporaneous sites are available at www.geolsoc.org.uk/SUP18555 .

Aquatic insect assemblages associated with subalpine stream segment types in relict glaciated headwaters

Abstract Aquatic habitats and biotic assemblages in subalpine headwaters are sensitive to climate and human impacts. Understanding biotic responses to such perturbations and the contribution of high‐elevation headwaters to riverine biodiversity requires the assessment of assemblage composition among habitat types. We compared aquatic insect assemblages among headwater stream segment types in relict glaciated subalpine basins in Mt. Rainier National Park, Washington, USA. Aquatic insects were collected during summer and autumn in three headwater basins. In each basin, three different stream segment types were sampled: colluvial groundwater sources, alluvial lake inlets, and cascade‐bedrock lake outlets. Ward's hierarchical cluster analysis revealed high β diversity in aquatic insect assemblages, and non‐metric multidimensional scaling indicated that spatial and temporal patterns in assemblage composition differed among headwater stream segment types. Aquatic insect assemblages showed more fidelity to stream segment types than to individual basins, and the principal environmental variables associated with assemblage structure were temperature and substrate. Indicator species analyses identified specific aquatic insects associated with each stream segment type. Several rare and potentially endemic aquatic insect taxa were present, including the recently described species, Lednia borealis (Baumann and Kondratieff). Our results indicate that aquatic insect assemblages in relict glaciated subalpine headwaters were strongly differentiated among stream segment types. These results illustrate the contribution of headwaters to riverine biodiversity and emphasise the importance of these habitats for monitoring biotic responses to climate change. Monitoring biotic assemblages in high‐elevation headwaters is needed to prevent the potential loss of unique and sensitive biota.

Pollen accumulation in lake sediments during historic spruce beetle disturbances in subalpine forests of southern Utah, USA

Paleoecological reconstructions using lake sediments provide important information about ecological dynamics and forest disturbance processes that occurred prior to the historic period of scientific observation. In high-altitude and high-latitude ecosystems where landscape-scale disturbances recur at time intervals exceeding observation in many regions, e.g. western North America, reconstructed environmental data are essential in providing context for land managers. During the most recent two decades eruptive populations of bark beetles ( Dendroctonus spp.) have rapidly and profoundly altered subalpine forest ecosystems across western North America. Outbreaks of these insects are unprecedented in scale and severity, at least historically. Currently, little information exists about these destructive outbreaks and in general, the information that exists, does not extend beyond the most recent few centuries. The research presented here examines sedimentary pollen records from six subalpine basins affected by severe spruce beetle ( D. rufipennis) epidemics during the 20th century in the high-elevation plateaus and mountain ranges of south-central Utah. Reciprocal exchanges in dominance between pollen abundance of host spruce ( Picea engelmannii) and non-host subalpine fir ( Abies lasiocarpa) associated with historic outbreaks are conspicuous. Calculating simple ratios of host and non-host pollen accumulations offers a useful metric to visually identify spruce beetle outbreaks using sedimentary records. However, supporting lines of evidence may be required to identify these disturbances with greater certainty over the Holocene. Our data and findings provide a platform with which to begin exploration of other paleoecological proxy methods for the ultimate purpose of generating more temporally extensive reconstructions of bark beetle disturbances using sedimentary records.

New records of early Middle Jurassic belemnites in the French Subalpine Basin and their paleobiogeographic significance

A biostratigraphic and systematic study based on belemnites collected along with ammonites was performed on four sections in the Subalpine Basin (SE France): Lac du Castillon and La Baume (Castellane area), Galabrun and Grand Lara (Gap area). The specimens, originating from hemi-pelagic marl-limestone alternations in the lower part of the “Calcaires à Zoophycos” Formation, are dated from Middle Aalenian (Murchisonae Zone) to Lower Bajocian (Humphriesianum Zone). Five belemnite taxa (Megateuthis elliptica, Holcobelus munieri, H. trauthi, Pachybelemnopsis roettingensis, Hibolithes sp.) have been identified, and two more taxa are reported in an open nomenclature (Belemnitida incertae sedis sp. 1 and sp. 2). The biostratigraphic range of the belemnite fauna is established. The new findings contribute to a more detailed understanding of the paleobiogeography of holcobelid belemnites that flourished at the northern margin of the Tethys Ocean and formed a distinct sub-Mediterranean fauna. The association herein described is similar to the fauna of the Calabro-Peloritani Arc (Calabria, Italy), a further hint for the supposed paleogeographic position of the latter during the Middle Jurassic.

Calcareous nannofossil biostratigraphy (Upper Bajocian–Lower Bathonian) of the Ravin du Bès section (Bas Auran, Subalpine Basin, SE France): Evolutionary trends of Watznaueria barnesiae and new findings of “ Rucinolithus” morphotypes

A biostratigraphic study based on calcareous nannofossils was performed on the Ravin du Bès section (Bas Auran area, SE France). Semi-quantitative estimates of total nannofossil and single species abundances showed that calcareous nannofloras are rare to common and their preservation is poor to moderate. The following biohorizons were identified and calibrated to ammonite biozonation: the first occurrence (FO) of Watznaueria aff. W. communis, the FO of Pseudoconus enigma; the FO of “ Rucinolithus”; the last occurrence (LO) of Carinolithus magharensis; the FO of Stephanolithion speciosum octum and the FO of Watznaueria barnesiae. These results confirm that calcareous nannofossils are good biostratigraphic markers for the Bajocian/Bathonian boundary interval. Moreover, the occurrence of P. enigma allows a direct calibration between Tethyan and Boreal nannofossil events and biozones. Morphometric analyses were performed on the W. communis– W. barnesiae group in order to quantify changes between the two taxa. The intermediate form W. aff. W. communis has been identified; it comprises coccoliths very similar to W. communis, but with central area length ≤ 0.9 μm. This study allowed the detailed reconstruction of the evolutionary trends from W. communis to W. barnesiae: the intermediate taxon W. aff. W. communis appears abruptly in the latest Bajocian and persists after the FO of W. barnesiae in the earliest Bathonian. Our results support the model of punctuated equilibrium rather than a phyletic gradualism. The finding of “ Rucinolithus” morphotypes, very similar to the Cretaceous taxa R. terebrodentarius and R. terebrodentarius youngii, is intriguing. They might represent nannoliths strongly affected by a recurrent “Lazarus effect” or be diagenetic artifacts or of bacterial bioprecipitation.