Valley Sites Research Articles

Nest feathering responses by Tree Swallows (Tachycineta bicolor) to experimental warming

Among many functions, bird nests protect eggs, developing young, and incubating adults from inclement weather. In Tree Swallows (Tachycineta bicolor), prior to and while females are incubating, males compete with rivals for feathers that they use to line nests. The thermal benefits hypothesis proposes that males add feathers to improve heat retention of nests. We tested this hypothesis on Tree Swallows nesting near Wolfville, Nova Scotia, Canada in 2013, 2014, and 2015, and in St. Denis, Saskatchewan in 2013. In 2013, at both locations we experimentally heated nests. After young had fledged, we counted and measured feathers in each nest. The hypothesis was not supported. The only significant result was that St. Denis (52.2°N) had fewer feathers than the Annapolis Valley (45.1°N) site, which is contrary to expectation. Our findings challenge the prevailing hypothesis for why male Tree Swallows feather nests.

Taphonomic interpretations of the Haasgat HGD assemblage: A case study in the impact of sampling and preparation methods on reconstructing South African karstic assemblage formation

The Haasgat fossil-bearing karstic system is situated within the Skurweberg Mountain range in the northeastern portion of the Fossil Hominids of South Africa UNESCO World Heritage Site in South Africa. As is the case for the nearby Gondolin hominin locality, Haasgat occurs in an area of substantial modern topographic relief that contrasts with the low-relief landscape of the southwestern extent of the World Heritage Site surrounding the Blauubank Stream Valley sites (e.g., Sterkfontein, Swartkrans, Kromdraai, Bolt's Farm). This suggests differential landscape formation processes during the Neogene and potentially novel palaeoecosystems and taphonomic processes governing karstic fossil assemblage composition across even a small geographic region. This is particularly critical given the overall paucity of taphonomic data from the region, the substantial cercopithecoid primate assemblage that is uniquely dominated by the basal baboon species Papio angusticeps, and the recent announcement of the first hominin specimen from Haasgat.Here we provide the first comprehensive taphonomic analysis of the Haasgat HGD faunal assemblage that was developed from ex situ calcified sediment blocks in the 1990s. There is direct evidence for biotic activity (e.g., large-bodied carnivores and porcupines) mediating the formation of parts of the HGD faunal assemblage, including at least part of the primate craniodental and postcranial sample. There is minimal evidence for pre-depositional element UV exposure and weathering or winnowing of the assemblage, but there is abiotic distortion and crushing of elements. Our analysis has equally found that taphonomic data from the HGD assemblage is compromised by a modern ‘overprint’ of damage through mechanical preparation and a lack of documentation generated during sampling, processing, and initial curation. Nearly half the cortical surfaces and many dental specimens in the assemblage exhibit evidence of substantial preparation damage rendering many purported biotic modifications ambiguous or suspect. Element proportions may be artificially skewed towards craniodental specimens and more reflective of block selection and/or selective processing rather than original deposition composition. As a result, the Haasgat HGD sample provides only limited data on the depositional processes mediating karstic assemblage formation in the region, and ultimately serves as a cautionary tale of the impacts of palaeontological sampling strategies on subsequent analysis and research.

Electrochemical properties of stanene as an efficient anode material for Na-ion batteries

We address the suitability of two dimensional (2D) mono layer of tin for anode material of Na-ion batteries (NIBs), within the framework of density functional theory (DFT). The cohesive energy for the three possible structures (planar, buckled and puckered) of stanene have been calculated. Present calculations suggest that hollow (H) site is most favorable for Na adsorption. The optimized distance in perpendicular direction for Na adsorption at H site is 1.68 Å. However at top, bridge and valley sites it comes equal to 2.90, 2.55 and 3.04 Å, respectively. The adsorption energy has been computed for different number (n) of adsorbed Na atoms on stanene. The Bader charge analysis indicates that each Na loses 0.77 e¯ per atom electronic charge to Sn atoms of stanene. During the sodiation process, there is minor distortion in lattice vectors with respect to pristine stanene. We have also calculated the average intercalation voltage (AIV) for different values of n. To study diffusion of Na on stanene, the most reliable climbing image nudged elastic band (CI-NEB) method based calculations have been carried out, which provides energy barrier of Na diffusion between the two initial guess states.

How the diversity, abundance, size and climbing mechanisms of woody lianas are related to biotic and abiotic factors in a subtropical secondary forest, Taiwan

Lianas are woody vines that play an important role in forest dynamics in tropical and subtropical areas. Their relationship to various biotic and abiotic conditions is, however, not yet wholly clear. We explored how the size, climbing mechanisms, diversity and abundance of woody lianas is related to host plant size, environmental factors and topography. Liana assemblages were examined in twenty 20 × 20 m plots in each of three topographic sites (valley, slope and ridge) in a subtropical secondary forest in southeastern Taiwan. The valley site had the highest abundance and species richness of lianas. The abiotic factors, soil pH and rock cover, were related to different topographic sites. Larger lianas were always found on larger host trees, while smaller lianas were found in smaller trees; no lianas with a DBH greater than 10 cm were found. Significantly more adhesive lianas were found on larger trees whereas twining and leaning-hook lianas were found in smaller trees. In conclusion, this study demonstrates that the species of liana is associated with the size and type of tree growing under different topographic conditions.

Новые данные комплексных исследований памятников железоплавильного производства в долинах рек Куектанар и Тюргун (Юго-Восточный Алтай)

Новые данные комплексных исследований памятников железоплавильного производства в долинах рек Куектанар и Тюргун (Юго-Восточный Алтай)

First-principles study of hydrogen storage properties of silicene under different Li adsorption components

Alkali metal has predicted to be a promising candidate for decorating silicene surface to obtain the high hydrogen storage capacity, owing to their physical properties of lightweight, lower cohesive energy, and appropriate strength of the interaction with H2 molecules. However, though the high potential in hydrogen storage of alkali metal adatoms-decorated silicene under the fixed adatom adsorption component is well known, the evidence for the hydrogen storage capacity of alkali metal adatoms-decorated silicene under different adatom adsorption components remains largely unexplored, which may be of great significance to make the most advantages of alkali metal adatoms-decorated silicene in hydrogen storage aspects. Herein, according to the first-principles calculation corrected by the van der Waals effect, we take Li-decorated silicene for example and perform the detailed study of the geometry structure, the stability and the hydrogen storage capacity of silicene under different Li adsorption components (LixSi1-x), aiming to maximize the hydrogen storage performance of Li-decorated silicene. The results show that the preferred site of Li changes from the hollow site to the valley site as the Li component increases from 0.11 to 0.50, and binding energy of Li is always greater than the corresponding cohesive energy, showing the high stability of Li-decorated silicene and the feasibility of the method to obtain a higher hydrogen storage capacity by increasing the Li component. The hydrogen storage of silicene under different Li adsorption components is investigated by the sequential addition of H2 molecules nearby Li atoms in a stepwise manner. It can be observed that the hydrogen storage capacity of Li-decorated silicene increases and the average adsorption energy decreases with the increase of the Li component. The corresponding hydrogen storage capacities of Li0.11Si0.89, Li0.20Si0.80, Li0.33Si0.67, Li0.43Si0.57 can reach up to 2.54 wt%, 4.82 wt%, 6.00 wt% and 9.58 wt% with 0.58 eV/H2, 0.47 eV/H2, 0.54 eV/H2 and 0.41 eV/H2 average adsorption energy, respectively. When the Li component increases up to 0.50, Li atoms are saturated with a maximum hydrogen storage capacity of 11.46 wt% and an average adsorption energy of 0.34 eV/H2, which well meet the hydrogen storage standard set by the U.S. Department of Energy and mean that the hydrogen storage can be theoretically improved by increasing the Li adsorption component to a saturated level. Furthermore, we analyze the Mulliken charge population, the charge density difference and the density of states, showing that the charge-induced electrostatic interaction and the orbital hybridization are the key factors for the hydrogen adsorption of Li-decorated silicene. Our results may enhance our fundamental understanding of the hydrogen storage mechanism and explore the applications in areas of hydrogen storage for Li-decorated silicene, which are of great importance for the usage of hydrogen in the future.

Metal adsorption on monolayer blue phosphorene: A first principles study

We investigated the electronic structure, adsorption energies, magnetic properties, dipole moment and work function of metal adatoms (Mg, Cr, Mo, Pd, Pt, and Au) adsorption on a blue phosphorene monolayer. For Mg, Pt and Au metals, the most stable state was found in hollow site while for Cr, Mo and Pd metals we found an adsorption in valley site. We suggest that the Pd and Pt atoms prefer 2D growth mode while the Mg, Cr, Mo and Au atoms prefer 3D island growth mode on monolayer phosphorene. The electronic band structures and magnetic properties were dependent on the doping site and dopant materials. For instance, the semiconducting features were preserved in Mg, Pd, Pt, and Au doped systems. However, the Cr and Mo doped systems displayed half-metallic band structures. The total magnetic moment of 4.05, 2.0 and 0.77 μB/impurity atom were obtained in Cr, Mo and Au doped systems whereas the Mg, Pd and Pt doped systems remained nonmagnetic. We also investigated the magnetic interaction between two transition metal impurities. We observed ferromagnetic coupling between two transition metal impurities in Cr and Mo doped systems while the Au doped system displayed almost degenerated magnetic state. For Mg, Cr, and Mo adsorptions, we found relatively large values of dipole moments compared to those in the Pd, Pt and Au adsorptions. This resulted in a significant suppression of the work function in Mg, Cr and Mo adsorptions. Overall, adsorption can tune the physical and magnetic properties of phosphorene monolayer.

Long-term chemical analysis and organic aerosol source apportionment at nine sites in central Europe: source identification and uncertainty assessment

Abstract. Long-term monitoring of organic aerosol is important for epidemiological studies, validation of atmospheric models, and air quality management. In this study, we apply a recently developed filter-based offline methodology using an aerosol mass spectrometer (AMS) to investigate the regional and seasonal differences of contributing organic aerosol sources. We present offline AMS measurements for particulate matter smaller than 10 µm at nine stations in central Europe with different exposure characteristics for the entire year of 2013 (819 samples). The focus of this study is a detailed source apportionment analysis (using positive matrix factorization, PMF) including in-depth assessment of the related uncertainties. Primary organic aerosol (POA) is separated in three components: hydrocarbon-like OA related to traffic emissions (HOA), cooking OA (COA), and biomass burning OA (BBOA). We observe enhanced production of secondary organic aerosol (SOA) in summer, following the increase in biogenic emissions with temperature (summer oxygenated OA, SOOA). In addition, a SOA component was extracted that correlated with an anthropogenic secondary inorganic species that is dominant in winter (winter oxygenated OA, WOOA). A factor (sulfur-containing organic, SC-OA) explaining sulfur-containing fragments (CH3SO2+), which has an event-driven temporal behaviour, was also identified. The relative yearly average factor contributions range from 4 to 14 % for HOA, from 3 to 11 % for COA, from 11 to 59 % for BBOA, from 5 to 23 % for SC-OA, from 14 to 27 % for WOOA, and from 15 to 38 % for SOOA. The uncertainty of the relative average factor contribution lies between 2 and 12 % of OA. At the sites north of the alpine crest, the sum of HOA, COA, and BBOA (POA) contributes less to OA (POA / OA = 0.3) than at the southern alpine valley sites (0.6). BBOA is the main contributor to POA with 87 % in alpine valleys and 42 % north of the alpine crest. Furthermore, the influence of primary biological particles (PBOAs), not resolved by PMF, is estimated and could contribute significantly to OA in PM10.

Plasticity in gas-exchange physiology of mature Scots pine and European larch drive short- and long-term adjustments to changes in water availability.

Adjustment mechanisms of trees to changes in soil-water availability over long periods are poorly understood, but crucial to improve estimates of forest development in a changing climate. We compared mature trees of Scots pine (Pinus sylvestris) and European larch (Larix decidua) growing along water-permeable channels (irrigated) and under natural conditions (control) at three sites in inner-Alpine dry valleys. At two sites, the irrigation had been stopped in the 1980s. We combined measurements of basal area increment (BAI), tree height and gas-exchange physiology (Δ13 C) for the period 1970-2009. At one site, the Δ13 C of irrigated pine trees was higher than that of the control in all years, while at the other sites, it differed in pine and larch only in years with dry climatic conditions. During the first decade after the sudden change in water availability, the BAI and Δ13 C of originally irrigated pine and larch trees decreased instantly, but subsequently reached higher levels than those of the control by 2009 (15years afterwards). We found a high plasticity in the gas-exchange physiology of pine and larch and site-specific responses to changes in water availability. Our study highlights the ability of trees to adjust to new conditions, thus showing high resilience.

Cell anatomy and leaf δ13C as proxies for shading and canopy structure in a Miocene forest from Ethiopia

Plant fossils are most commonly preserved as isolated organs, making it difficult to determine plant life habit or ecosystem structure from fossils. In particular, paleoecologists have struggled to reconstruct forest canopy structure, a character that fundamentally influences hydrology, nutrient cycling, and plant and animal life. Analyses utilizing cellular morphology and leaf carbon isotope composition have been proposed to reconstruct light regime, itself a proxy for canopy structure, and we apply these proxies to exquisitely preserved leaf fossils from the early Miocene Mush Valley site in central Ethiopia. Epidermal cell wall undulation (undulation index, UI) and carbon isotope values (δ13C) were measured for 21 fossil leaves of a legume morphospecies, “Legume 1”. Five leaves of a second legume morphospecies were also analyzed using the same procedures. Carbon isotope ratios and total organic carbon content were measured for 85 additional fossil leaves belonging to at least nine morphospecies. A large range of both leaf δ13C and UI values were obtained for Legume 1, indicating that different leaves were exposed to different amounts of light, as would be expected in a closed-canopy forest. However, Legume 1 leaf UI values do not correlate with leaf δ13C values, implying that one or both of these variables is driven by factors other than light exposure. Additional modern calibrations are needed to determine the key environmental variables for each measure, as well as the influence of forest openings on preserved signatures.

European Skipper Butterfly (<i>Thymelicus lineola</i>) Associated with Reduced Seed Development of Showy Lady’s-slipper Orchid (<i>Cypripedium reginae</i>)

It has been suggested that European Skipper butterflies (Thymelicus lineola) trapped in the lips of the Showy Lady’s-slipper orchid (Cypripedium reginae) may interfere with pollination. This could occur through blockage of the pollinator pathway, facilitation of pollinator escape without pollination, and/or disturbance of the normal pollinators. A large population of the orchid at an Ottawa Valley site provided an opportunity to test the interference hypothesis. The number of trapped skippers was compared in 475 post-blooming flowers with regard to capsule development and thus seed development. The presence of any skippers within flowers was associated with reduced capsule development (P = 0.0075), and the probability of capsule development was found to decrease with increasing numbers of skippers (P = 0.0271). The extent of a negative effect will depend on the abundance of the butterflies and the coincidence of flowering time and other factors. Counts of skippers trapped in flowers were found to follow closely a negative binomial distribution (P = 0.8656).

Integration of natural stone features and conservation of the Upper Palaeolithic Côa Valley and Siega Verde open-air rock-art

ABSTRACTThis paper considers the established phenomenon of the integration of pre-existing natural features into Western European Upper Palaeolithic parietal imagery, aiming to present a preliminary inventory of such cases in the Côa Valley and Siega Verde rock-art sites. Attention is also given to other cases at these sites from which it can be inferred that areas of the engraved surfaces persisted since the original motifs were made until today in quite reasonable condition. It is concluded that the present research further emphasizes the complex traits behind the creation of Upper Palaeolithic artistic motifs in both the Portuguese and Spanish sites, and also suggests a reasonable preservation rate of Côa and Siega Verde rock-art.

Spatial patterns of degraded tropical forest and biodiversity restoration over 70-years of succession

Landscape metrics have often been used to analyse the spatial dynamics of habitat fragmentation accompanying forest loss. However, there are few studies of the spatial dynamics of natural forest succession, especially over periods longer than the operational period of imaging satellites. This study applies spatial metrics to understand the spatial processes of a 70-year tropical secondary forest succession in Hong Kong, since World War 2. The highest rate of forest regeneration at 11% a year from 1989 to 2001 occurred when the landscape achieved greatest habitat diversity and juxtapositioning of habitat patches. This rapid regeneration occurred by infilling from remnant forest in adjacent valleys rather than by an advance along a broad forest front, and led to simplification of the landscape and declining habitat diversity. It was also accompanied by declines in species richness and abundance in regenerated forest patches. Thus both habitat and woody plant species diversity show a humped trend over the successional period as disconnected forest patches amalgamate, and shade-intolerant pioneers are shaded out by taller pioneers. From this point onwards, the birds of mixed habitats including bulbuls and hwamei known to disperse seed in the study area, may become less effective as forest patches consolidate, and only a few forest mammals remain. The observed improved connectivity within forest patches and reduced edge disturbances accompanying landscape simplification provide better conditions for dispersion within forest of light-intolerant climax species from the oldest, species-rich valley sites to the newly regenerated areas. However, in addition to the loss of forest dispersal agents, other natural dispersal agents such as gravity, flash floods and slope wash involving downward processes may be ineffective, as forest has regenerated upwards to higher elevations. Progression to a mature, biodiverse and stable forest ecosystem may depend on introduction of dispersal agents other than those which have operated over recent decades. Forest patches with high internal connectivity, indicated by high Mean radius of Gyration (MRG) and low Mean Perimeter-to-Area Ratio (MPAR) would appear to offer the best movement opportunities and least disturbance to such introductions.

Stable isotopes reveal human influences on southern New Zealand soils

A multi-isotopic soil study across a southern New Zealand transect has been undertaken as part of a geochemical baseline survey to identify human impacts on New Zealand's landscape and characterise different land uses and anthropogenic effects. Carbon, nitrogen and sulphur isotopes from two soil depths (0–30 and 50–70 cm) were acquired across a variety of land uses (including pristine national parks, urban centres, intensively farmed pastoral land), climates (dry <500 mm annual rainfall to wet >6000 mm annual rainfall), altitude (sea level to >2300 m above sea level) and soil parent material lithology (sandstone, schist, basalt). Detrital organic matter accumulated more in lowlands than at higher altitudes with higher carbon and nitrogen contents found in river valleys. Carbon isotopes clearly differentiated between drier higher altitude or open pastoral sites (more positive values) and wetter forested sites (more negative values). Nitrogen isotopes reflect anthropogenic human influence with elevated values around urban and intensively farmed sites, and lower values characterising indigenous forests and pristine sites. Sulphur isotopes either show more positive values, typical of fertilisers, rain or sea spray in open pastoral sites, or more negative values consistent with weathered geological sources such as metamorphic sulphides found in schist in some river valley sites. The study demonstrates that regional isotope studies are a potential tool to understand the long and short term impacts on landscapes, and may be useful for future mineral exploration, urban health studies, agricultural site remediation, and land use control and regulation.

Oil Palm and Rubber Tree Water Use Patterns: Effects of Topography and Flooding.

Oil palm and rubber plantations extend over large areas and encompass heterogeneous site conditions. In periods of high rainfall, plants in valleys and at riparian sites are more prone to flooding than plants at elevated topographic positions. We asked to what extent topographic position and flooding affect oil palm and rubber tree water use patterns and thereby influence spatial and temporal heterogeneity of transpiration. In an undulating terrain in the lowlands of Jambi, Indonesia, plantations of the two species were studied in plot pairs consisting of upland and adjacent valley plots. All upland plots were non-flooded, whereas the corresponding valley plots included non-flooded, long-term flooded, and short-term flooded conditions. Within each plot pair, sap flux densities in palms or trees were monitored simultaneously with thermal dissipation probes. In plot pairs with non-flooded valleys, sap flux densities of oil palms were only slightly different between the topographic positions, whereas sap flux densities of rubber trees were higher in the valley than at the according upland site. In pairs with long-term flooded valleys, sap flux densities in valleys were lower than at upland plots for both species, but the reduction was far less pronounced in oil palms than in rubber trees (-22 and -45% in maximum sap flux density, respectively). At these long-term flooded valley plots palm and tree water use also responded less sensitively to fluctuations in micrometeorological variables than at upland plots. In short-term flooded valley plots, sap flux densities of oil palm were hardly affected by flooding, but sap flux densities of rubber trees were reduced considerably. Topographic position and flooding thus affected water use patterns in both oil palms and rubber trees, but the changes in rubber trees were much more pronounced: compared to non-flooded upland sites, the different flooding conditions at valley sites amplified the observed heterogeneity of plot mean water use by a factor of 2.4 in oil palm and by a factor of 4.2 in rubber plantations. Such strong differences between species as well as the pronounced heterogeneity of water use across space and time may be of relevance for eco-hydrological assessments of tropical plantation landscapes.

Small-scale spatial and temporal variation of life-history traits of common frogs (Rana temporaria) in sub-Arctic Finland

Small-scale spatial and temporal variation in abiotic and biotic environmental conditions can lead to large differences in mean values of important life-history traits in ectothermic vertebrates, such as amphibians. However, relatively little is known about small-scale variation in life-history traits of sub-Arctic amphibians. We studied the spatio-temporal variation of adult life-history traits linked to age and body size in the common frog (Rana temporaria) from low (i.e., valley at 480 m a.s.l.) and high (i.e., hill at 530–650 m a.s.l.) altitude sites in the sub-Arctic Kilpisjarvi area (Finland). Data on life-history traits of frogs from hill sites collected during a 3-year field study were compared with previously published data from the valley sites. The results showed spatio-temporal variation in life-history traits, frogs responding to spatio-temporal variation in the environmental conditions with variation in age, life span, survival rates, body size, and mass. Frogs from hill sites had shorter life span, both in terms of mean age (5.6 versus 10.5 years) and longevity (9–10 versus 18 years), smaller snout-vent length (63 versus 77 mm), and body mass (24 versus 45 g) than frogs from valley sites. The differences were more pronounced in females than in males indicating some sex-specific responses to environmental differences among sites. The results show that small differences in elevation (or elevation-related abiotic and biotic factors) can translate to large differences in mean values of important life-history traits in common frogs living at the edge of their distribution range.

Using magnetic fly ash to identify post-settlement alluvium and its record of atmospheric pollution, central USA

Abstract Fly ash has been atmospherically dispersed from coal burning in the central USA since the 1860s and subsequently incorporated into post-European settlement alluvial records. Regionally, the onset of significant coal burning approximately coincides with widespread land clearing for agriculture and accelerated erosion. Field identification of post-settlement alluvium (PSA) is difficult in many areas where the record lacks apparent contrast with older alluvium. Here, we show the PSA basal contact can be reliably identified based on the occurrence of magnetic fly ash. Fly ash methodology is relatively simple, effective, and inexpensive. The proportion of spheroidal fly ash grains in silt-size magnetic fractions was evaluated from 17 sites in the Upper Sangamon River Basin, central Illinois. Data indicate the PSA is 25–95 cm thick, increasing linearly with valley width (r2 = 0.74). Yet, the proportion of PSA within Holocene alluvium is inversely and linearly correlated with valley width (r2 = 0.87), implying significant storage of recent sediment in tributary valleys. A peak in fly ash content (∼15–50 cm in Sangamon Valley), circa 1945–1980, is coeval with peaks in 137Cs (cesium), Pb (lead) concentrations, magnetic susceptibility, and silt content during a time of maximal atmospheric pollution and accelerated topsoil erosion. Sharp decreases in fly ash in the upper 10–20 cm (post-1980) of some Sangamon Valley sites coincide with the implementation of particulate pollution controls and reductions in 137Cs and Pb concentrations; more sandy alluvium also suggests proportionally increased stream bank erosion relative to upland erosion. PSA sedimentation averages ∼5 mm/yr, an order of magnitude faster than pre-settlement rates, reflecting impacts of agriculture and other land-use changes.

Airolo-Madrano (TI): Palaeoenvironment and subsistence strategies of a hilltop settlement in the southern Swiss Alps during the Bronze and Iron Ages

The study of the Leventina valley site of Airolo-Madrano “In Grop” (Ticino, Switzerland; altitude 1156 m asl), inhabited during the Bronze and Iron Ages, is important in the current debate about mountain societies and economies in pre- and protohistoric times. The compilation of botanical data (seeds, pollen, charcoal) gathered during the excavations helps to define the type of occupation, the subsistence and the human impact on the upper Leventina valley between c. 1650 and 200 cal. BCE. Subsistence and husbandry activities, including cultivation, gathering, collecting of bedding and forage, even grazing in the forests, seems to have evolved in the local landscape. Under growing anthropogenic or environmental pressure from the Late/Final Bronze Age onwards, the opening of the landscape was not associated with expanding settlements, but more probably with a shift in forest subsistence economy activities. Like at other mid-altitude mountain sites in Switzerland and in bordering countries (Austria, Italy), barley (Hordum vulgare) was the most common crop, followed by other cereals (Triticum dicoccon, Tr. spelta, cf. Tr.aestivum/turgidum, cf. Panicum miliaceum), pulses (Pisum sativum, cf. Vicia faba beginning in the Iron Age) and oil-producing plants (Linum usitatissimum). Clear indicators of contact with the subalpine range that dominates the region of Madrano have not been found. However, the results of landscape surveys in that area show a human presence earlier, contemporary and later than that of the mountain dwelling in the valley, and moreover suggest that the tree line was at an elevation of more than 2000 m asl in the Bronze Age. The presence of pollen and cereal fruit in the Late Bronze Age (Hordeum vulgare) and post-Medieval periods (remains of threshing of Triticum cf. dicoccon/monococcum) might imply cultivation in high altitudes, the upper elevation of which remains undetermined, in spite of the coincidence between palaeoclimatical proxies and ethnographic data.

Tunable electronic and magnetic properties in stanene by 3d transition metal atoms absorption

The electronic and magnetic properties of transition metal (TM) atoms (V, Cr, Mn, Fe, Co, Ni) adsorption on stanene are investigated by first-principles calculations. The results indicate that the TM atoms prefer to be relaxed on a H site on stanene except V atom which lies on the valley site. Fe-absorbed stanene is a spin gapless semiconductor with up-spin electron and down-spin hole carriers allowing the coexistence of charge current and the pure spin current. Co-absorbed stanene lies in the half metal phase. The V-, Cr-, Mn-, and Cu-absorbed stanene turn the stanene into metal, while Ni- and Zn-absorbed stanene open a narrow band gap. For V-, Cr-, Mn-, Fe-, and Co-absorbed stanene, the magnetic moment of the TM will survive while the Ni-, Cu-, and Zn-absorbed stanene will be non-magnetic material. These findings may have great potential in the design of new electrically controllable spintronic devices.

Statistical Downscaling of Gridded Wind Speed Data Using Local Topography

Abstract Winds, particularly high winds, strongly affect snowmelt and snow redistribution. High winds during rain-on-snow events can lead to catastrophic flooding while strong redistribution events in mountain environments can generate dangerous avalanche conditions. To provide adequate warnings, accurate wind data are required. Yet, mountain wind fields exhibit a high degree of heterogeneity at small spatial lengths that are not resolved by currently available gridded forecast data. Wind data from over 200 stations across Switzerland were used to evaluate two forecast surface wind products (~2- and 7-km horizontal resolution) and develop a statistical downscaling technique to capture these finer-scaled heterogeneities. Wind exposure metrics derived from a 25-m horizontal resolution digital elevation model effectively segregated high, moderate, and low wind speed sites. Forecast performance was markedly compromised and biased low at the exposed sites and biased high at the sheltered, valley sites. It was also found that the variability of predicted wind speeds at these sites did not accurately represent the observed variability. A novel optimization scheme that accounted for local terrain structure while also nudging the forecasted distributions to better match the observed distributions and variability was developed. The resultant statistical downscaling technique notably decreased biases across a range of elevations and exposures and provided a better match to observed wind speed distributions.