bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploring the hydrogeological functioning and microbial habitats of the deep hillslope aeration zone in limestone-mudrock alternations
Authors: Lehmann Robert , Lazar Cassandre Sara , Küsel Kirsten , Totsche Kai Uwe
Published: March 2020

The aeration zone beneath topographic groundwater recharge areas, comprising variably water-saturated soil, regolith and bedrock is a typically large but hardly explored compartment of the Critical Zone. Fluid and matter exchange within the deep hillslope aeration zone, the dynamics of its diverse microbial dwellers and their contribution for subsurface matter cycling and groundwater quality are widely unknown. In the Hainich Critical Zone Exploratory (Collaborative Research Center AquaDiva, Küsel et al., 2016), we accessed the aeration zone and groundwater resources in fractured limestone-mudstone alternations by exploratory drillings and hillslope monitoring wells. Multi-year groundwater sampling, environmental monitoring, drill core and petrological analyses revealed a multi-storey architecture of the aeration zone, covering perched water bodies and multi-directional flow phenomena (Lehmann and Totsche 2020). In a ~50 m deep well that underwent pronounced seasonal head fluctuation up to 25 m of oligotrophic groundwater, we incubated bedrock fragments that mimicked large fracture habitats and monitored the dynamic environmental conditions in the fractured mixed carbonate-/siliciclastic alternations as well. During groundwater-saturated colonization, successional exposure to seasonal de-saturation and re-saturation, we analyzed the bacterial and archaeal 16S rRNA diversity and found a diverse bacterial, and less diverse archaeal community, both including persistent genera that withstood the harsh environmental changes. In accordance with mature fracture-surfaces (drill cores), the colonized rock fragments were dominated by Gammaproteobacteria. General compositional differences to communities within the phreatic zone (i.e. groundwater and rock matrices), and shallow sources in soil, suggest a distinct subsurface microbiome that is hardly represented by ecological surveys that utilize groundwater or rock samples.

 

References:

Küsel, K., Totsche, K. U., Trumbore, S. E., Lehmann, R., Steinhäuser, C., Herrmann, M. (2016). How deep can surface signals be traced in the critical zone? Merging biodiversity with biogeochemistry research in a central German Muschelkalk landscape. Frontiers in Earth Science 4 (32). https://doi.org/10.3389/feart.2016.00032

Lehmann, R., Totsche, K. U. (2020). Multi-directional flow dynamics shape groundwater quality in sloping bedrock strata. Journal of Hydrology 580. https://doi.org/10.1016/j.jhydrol.2019.124291
The rule of thumb for inferring plate coupling status based on the mantle lithospheric buoyancy
Authors: Lo Chung-Liang , Doo Wen-Bin , Hsu Shu-Kun
Published: March 2020

The subduction zone is a convergent plate boundary, and where most seismic activity is concentrated and megathrust may occur. To evaluate the potential hazard in subduction zones always relates to the plate coupling status. From previous studies, the status of plate coupling between plates can be reflected by the vibration of the buoyancy of mantle lithosphere (Hm). As far as the respective plate coupling states are concerned, more than a dozen Hm profiles across different subduction zones have been successfully verified. It is normally to determine the coupling status depending on the Hm vibration without manifest definition. We therefore propose a method to estimate the plate coupling factor (pcf) quantitatively. The pcf is defined as the difference of the Hm caused by the respective subduction and overriding plates between the distances where Hm deviated from the normal lithospheric Hm value across the plate boundary. The collected Hm profiles are calculated by the proposed method, the results show that the pcf value is corresponding well to the plate coupling status in the respective subduction zone. The small pcf is for strong plate coupling, such as the northern Sumatra and the southern central Andes subduction zones, while the large pcf is for weak coupling, such as the Calabria and the northern Manila subduction zones. The calculation of pcf is a feasible solution for determination of plate coupling status, but more Hm profiles across subduction zones will help the estimation more reliable.
Stratigraphy, environment and climate of the mid Cretaceous succession from the Arctic region (Baffin Bay)
Authors: Sliwinska Kasia K. , Bojesen-Koefoed Jørgen , Naafs David , Nøhr-Gansen Henrik , Krarup Pedersen Gunver , Hovikovski Jussi , Knutz Paul C.
Published: March 2020

The super greenhouse climate of the middle Cretaceous represents an analogue for an extreme CO2 induced (run-away) climate system. In order to improve the understanding of how the high northern latitudes responded to the escalating middle Cretaceous warmth we analysed dinocysts, palynofacies, δ13C and various biomarker proxies through a unique mid Cretaceous succession from the northern Baffin Bay. Our study is based on a several sites that were cored during the IODP Expedition 344S.
The composite section represents a nearly complete Albian - Turonian succession deposited during the syn-rift phase separating Greenland from Canada/North America. Depositional environments range from anoxic outer shelf and pro-delta fringe to oxygen-restricted lower delta front. The organic geochemical proxies are focusing on the OAE 2 and will investigate changes in the sea surface temperature and water column oxygenation related with this event.
Middle Miocene onset of thrusting along the basal décollement of the Jura Mountains: Evidence from carbonate U-Pb dating and clumped isotope thermometry
Authors: Looser Nathan , Madritsch Herfried , Guillong Marcel , Laurent Oscar , Wohlwend Stephan , Bernasconi Stefano M.
Published: March 2020

During its late-stage evolution, the European Alpine orogen witnessed a northwest-directed propagation of its deformation front along an evaporitic basal décollement into the foreland. This resulted in the decoupling of the northern Alpine Molasse Basin from its basement and the formation of the Jura fold-and-thrust belt. Here, we present the first absolute age and temperature constraints on deformation along this major décollement by using combined carbonate U-Pb dating by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and clumped isotope thermometry. We analyzed calcite veins associated with a secondary thrust fault branching off from the basal décollement in a deep borehole within the Swiss Molasse Basin providing evidence for three brittle deformation events related to Alpine contraction: Vein formation at ~14 Ma ago, thrust faulting with cataclasis ~13 Ma ago, and another vein formation event ~9 Ma ago. Clumped isotope data reveal vein calcite precipitation at temperatures of ~100 °C from fluids equilibrated with the host rock during all deformation intervals. These temperatures are in good agreement with temperature estimates from microfabrics of anhydrite mylonites in the basal décollement. Our data demonstrate that the propagation of Alpine deformation into its distal foreland occurred significantly earlier than previously inferred, at middle Miocene (Langhian) times at the latest, contributing to the debate about the late-stage geodynamics of the central Alps. The deformation sequence indicated by our results underpins fundamental kinematic models of viscous décollement-based foreland thrust belts. Beyond that, we demonstrate the potential of our methodological approach applied to foreland thrust systems in resolving the late-stage evolution of convergent orogens.
Aerosol sources identification in Kaunas city using stable carbon isotope and polycyclic aromatic hydrocarbons analysis
Authors: Garbaras Andrius , Garbariene Inga , Masalaite-Nalivaike Agne , Ceburnis Darius , Krugly Edvinas , Remeikis Vidmantas , Martuzevicius Dainius
Published: March 2020

The main idea of this research was to combine carbon stable isotope ratio (δ13C) analysis and polycyclic aromatic hydrocarbons (PAH) diagnostic ratios for the identification of pollution sources in Kaunas city, Lithuania. Aerosol particle sampling was performed in wintertime simultaneously in outdoor and indoor environments using cascade impactors.

Due too low mass not all impactors stages were analysed, especially in the indoor environment. It was determined that total carbon concentrations were higher in outdoor samples in the most cases. The outdoor δ13C values varied from -27.5 to -24.5 ‰. The indoor δ13C values varied from -28.5 to -25.8 ‰ and were close to δ13C values reported for biomass burning [1].

δ13C and PAH analysis revealed that main aerosol sources were biomass combustion and traffic emissions. Also coal combustion was identified as common source for aerosol particles in one location.

 

[1] A. Garbaras et al., “Stable carbon fractionation in size-segregated aerosol particles produced by controlled biomass burning,” J. Aerosol Sci., 2015.
Micromechanical modeling of crack propagation in weak snow layer
Authors: Bobillier Gregoire , van Herwijnen Alec , Bergfeld Bastian , Gaume Johan , Schweizer Jürg
Published: March 2020

Improving the prediction of snow avalanches requires a detailed understanding of the fracture behavior of snow, which is intimately linked to the mechanical properties of the snow layers (strength, elasticity of the weak and slab layer). While the basic concepts of avalanche release are conceptually relatively well understood, understanding crack propagation and fracture propensity remains a great challenge. About 15 years ago, the propagation saw test (PST) was developed. The PST is a fracture mechanical field test that provides information on crack propagation propensity in weak snowpack layers. It has become a valuable research tool to investigate processes and mechanical parameters involved in crack propagation.

Here, we use the discrete element method (DEM) to numerically simulate PST and therefore analyze fracture dynamics based on micromechanical approach. Using cohesive and non-cohesive ballistic deposition, we numerically reproduce the basic required layers for dry-snow avalanche: a highly porous and brittle weak layer covered by a dense cohesive slab.

The results of these numerical PTSs reproduce the main dynamics of crack propagation observed in the field. We developed different indicators to define the crack tip and therefore derive the crack velocity. Our results show that crack propagation on flat terrain reaches a stationary velocity if the snow column in long enough. The length of the snow column to reach stationary crack velocity depends on snowpack parameters. On sloped terrain our results show a transition in the local failure mode, this transition can be visualized from the crack tip morphology and from the main stress component.

Overall, our results lay the foundation for a comprehensive study on the influence of the snowpack mechanical properties on these fundamental processes for avalanche release.
Evaluation of the impact of preventive information on natural risks with original immersion tools
Authors: Beck Elise , André-Poyaud Isabelle , Arnaud Aurélie , Borelly Audrey , Chionne David , Duché Sarah , Gaïdatzis Christelle , Grancher Delphine , Jacquemet Etienne , Lutoff Céline , Revol Claire , Robinet Nicolas , Servet Pascal
Published: March 2020

Since its creation in the late 1990s, UNISDR has identified education and knowledge as priority factors for risk and disaster reduction, notably through Hyogo and Sendai frameworks for actions. More recently, the 2019 Assises Nationales des Risques Naturels (a major meeting event organized by the French Ministry of Ecology on the natural risks management) have pointed out the urgent need to develop a risk culture to improve the resilience of territories. One of the levers for developing this risk culture is to inform the population of the risks to which they are exposed. Preventive information can take a wide variety of forms: regulatory brochures, exhibitions, plays, etc. However, we can wonder about the impact of this information: is it effective? Does it reach its objectives? How to evaluate its influence?

In a geographical context where few natural disasters occur, questionnaire surveys can be a solution. However, several studies have shown that this method fails to put individuals in a situation of emergency and to project themselves into a potential event that they may have difficulties to imagine. This is why the I²PRI project proposes to go beyond these methods and develop innovative and immersive tools to assess the impact of preventive information on people's knowledge. The project developed both a video game and a play. The objective of these media is to immerse the respondents in a fictive but realistic disaster situation in order to evaluate their ability to mobilize their knowledge in the case of a real event. Those tools are based on a common scenario that aims at putting the respondents in a dilemma situation. They mobilize an artistic dimension and raise the question of how to transcribe natural events through sound and visual stimuli or through interactions with other characters. Each tool has an observation and a debriefing phase which allow not only to analyse the respondents reactions but also to assess the efficiency of the whole protocol.

Applied to two phenomena (fast kinetic floods and earthquakes), the survey has been carried out in six municipalities of the French Alps. Those municipalities are characterized by different geographical contexts (urban/rural, plain/mountain) and different preventive information contexts (old information, regulatory information, alternative information). The talk will present the two protocols and the first results of their deployment in the field: the results of the survey about the level of information of the population, the side effects of the protocols in terms of preventive action, and the action-based research process in terms of public action of preventive information.
Seismic Modeling of the Subcrustal Reflectivity Beneath the Iberian Massif (Spain)
Authors: Palomeras Imma , Ayarza Puy , Díaz Jordi , Andrés Juvenal , Carbonell Ramon
Published: March 2020

Sub-Moho reflectors have been identified in seismic refraction and wide-angle reflection recordings in western Iberia since the late ‘80s. These control source seismic wide-angle shot records have energy large enough to illuminate the uppermost mantle showing strong sub-Moho arrivals at distant offsets (>180 km) with amplitudes significantly higher than the Pn and a relatively long coda. The kinematics and wavelet characteristics of these features are probably produced by an increase in P-wave velocity, and forward modeling indicates that these arrivals reflect off an interface in the 60-80 km depth range beneath the Iberian Massif. The waveform and time length of this arrival suggests that it can result from the interaction of the seismic energy with a ~10 km thick heterogeneous layer. To test this hypothesis, we used a 2D second-order finite-difference acoustic and elastic full wave-field scheme with a layer consisting of randomly distributed bodies smaller than ¼ of the wavelength of the seismic waves in thickness and ΔVp=±0.2 km/s at the considered depth range. Resulting synthetic shot gathers reproduce well the observed amplitudes and codas as a result of the constructive interference caused by the tuning effect produced by this gradient heterogeneous zone. The contrast in physical properties and depth level of this feature are consistent with the top of the phase transition from spinel to garnet lherzolite, the so-called Hales discontinuity.

Some of the available gathers show a second and deeper reflection. Detailed analysis of the reflected wave-forms suggests that the reflected wavelet has reversed polarity, a feature suggesting. a velocity decrease with depth. Finite difference acoustic and elastic full wave-field modeling places this discontinuity around 90 km depth beneath the Ossa-Morena Zone (south Iberian Massif). A lateral change is observed beneath the Centro-Iberian Zone (central Iberian Massif) where it is imaged at 103-110 km depth on the southeast and shallows up to 80 km depth on the northeast. The indicated depth would be consistent with the depth location of the LAB, which is relatively well constrained for the target area by other geophysical observations.

Funding resources: EU EIT-RawMaterials Ref: 17024_20170331_92304; MINECO: CGL2016-81964-REDE CGL2014-56548-P: JCYL: SA065P17). 
Sounder Accelerated Particles at Mars: Observations, Mechanisms, and Applications
Authors: Voshchepynets Andrii , Barabash Stas , Holmstrom Mats , Frahm Rudy , Kopf Andrew
Published: March 2020

We report the first observations of sounder accelerated particles (SAP) in the ionosphere of a planet which does not possess a strong magnetic field (Mars). These observations were conducted onboard the Mars Express spacecraft by the ion and electron sensors of the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) experiment and the powerful topside sounder: Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS). Accelerated ions (O2+ , O+, and lighter ions) are observed in an energy range up to 800 eV when MARSIS transmits at a frequency close to the plasma frequency. Individual observations consist of almost monoenergetic ion beams either aligned with the MARSIS antenna or lying in the perpendicular plane. The observed ion beams are often accompanied by a decrease in the electron flux. Accelerated electrons are observed at energies up to 400 eV when MARSIS transmits at a frequency between the local plasma frequency and its harmonics (up to four times the plasma frequency). The majority of the sounder accelerated electrons are recorded close to the regions of intense crustal magnetic fields. The voltage applied to the MARSIS antenna causes spacecraft charging to 100’s of volts by electrons from the ambient plasma. Positively charged ions are accelerated when the spacecraft discharges. Accelerated photoelectrons are released by the highly charged spacecraft and after one gyration in the strong magnetic field, return to the spacecraft which has already discharged. The acceleration effect influences which ions can be observed by increasing the energy of the thermal ion species making it possible to detect them whereas they would be indistinguishable under normal circumstances. We present the relevant data and discuss how these effects can be used for diagnostic of the local plasma.
Modeling annual diffuse phosphorus concentrations in Danish mini-catchments
Authors: Tornbjerg Henrik , Windolf Jørgen , Thodsen Hans , Kjeldgaard Ane , Larsen Søren E , Kronvang Brian
Published: March 2020

Intensive monitoring data from the Danish National Monitoring programme (NOVANA) from 24 smaller catchments (mean: 14 km2) was used in a two layer cross-validation to establish a model for the annual diffuse phosphorus (P) flow-weighted concentration in Danish streams. A total of 196 monitoring years with data from automatic sampling (ISCO) of water from the 24 streams were used as a training dataset. Data in the training dataset covers the period 1994-2002.

Moreover, another dataset consisting of 108 agricultural mini-catchments with discrete water samples covering the period 1990-2017 was used as a control in the eight different georegions of Denmark. A total of four different models was established three models based on the intensive dataset and one model based on the larger dataset with discrete water sampling.

The best model established included eight explanatory parameters and explained 53 % of the variation in the annual flow-weighted total P concentrations in the training dataset. A validation of the four different models established showed that the best model has to be bias-corrected in some of the georegions. The result of the validation shows that the models generally overestimate the total P concentrations.   An overestimation of around 10-20% was to be expected as intensive automatic water sampling in streams has shown that the flow-weighted concentration of total P obtained from discrete sampling (monthly or fortnightly) is normally underestimated.

The validations of the three models based on intensive dataset showed an R-square between 0.08 and 0.12. The model based on the larger data with discrete samples had an R-square (0.29).
Meltwater and circulation characteristics adjacent to Larsen C ice shelf: insights from seawater oxygen isotopes
Authors: Mirkin Joshua , West Adam , Hutchinson Katherine , Flynn Raquel , Fawcett Sarah
Published: March 2020

The Larsen C ice shelf (LCIS) in the western Weddell Sea has recently undergone large-scale ice shelf collapse with the detachment of iceberg A68 in 2017. Cold cavity ice shelves, such as LCIS, are critical for the formation of the world’s coldest, densest waters and act to prevent the flow of land-fast ice into the ocean, which would result in sea-level rise. Their disintegration is thus of great scientific interest and growing public concern. It has been hypothesized that ice shelf breakup may result from ice shelf thinning, which can be caused by densification through surface processes, a decrease in grounded ice flow, or increased surface or basal melting. To investigate whether ice shelf melting may be contributing to the collapse of LCIS, we collected full depth profiles of seawater samples at 17 stations in the vicinity of LCIS in January 2019 during the Weddell Sea Expedition. To investigate the formation processes and distribution of water masses, as well as identify regions of ice shelf melt, the samples were measured for seawater oxygen isotopic composition (δ18O) using a Picarro Cavity Ring-Down Spectroscope (CRDS). The isotope data provide little evidence of large-scale surface or basal ice shelf melting, with basal ice shelf melt constituting a maximum of 0.5% of the Ice Shelf Water (ISW) observed in the vicinity of LCIS. One implication of this is that surface and basal melting may not be the primary factor driving the collapse of LCIS, although more data and further study are required to confirm this. In addition, the isotope data are consistent with previous work suggesting that the onshore advection of warm offshore waters occurs via the Jason Trough, a remnant depression in the seafloor caused by the flow of a palaeo-ice stream. This, in combination with the observation (based on incorporating seawater δ18O into a temperature-salinity-oxygen mass balance model) that the outflow of ISW occurs primarily to the north of the study region, supports a clockwise circulation pattern in the vicinity of LCIS.
Estimating additional root cohesion by exploiting a root topological model based on Leonardo’s Rule
Authors: Noto Leonardo Valerio , Francipane Antonio , Preti Federico , Petti Marco , Arnone Elisa
Published: March 2020

Root topological models are schematic representations of the root structure based on a defined topology graph theory. In the context of hillslope stabilization modeling against rainfall-induced shallow landslides, the root topological models may be used in combination with root strength models assessment, such as the Root Bundle Model (RBM), to estimate the ultimate root reinforcement. The effect of plant roots on slope stabilization is determined by the interaction between soil and the hydrological processes (within the root zone) and the biotechnical characteristics of the root system, such as root length, root density, root tensile strength, root area, root diameter profile and the total number of roots. Describing adequately the root architecture of a plant species is useful, for example, to evaluate how the root structure may change in different soil and/or climatological conditions and, ultimately, as an example, to assess the most suitable plant species to be adopted.
This study exploits the potentiality of a root topological model based on Leonardo’s rule in describing root architectures of (i) different species (and tree individual) at given growth conditions, (ii) same species at different environmental conditions, e.g., exposure to light, water and nutrient availability. The former is supported by field campaign measurements from Tuscany region, the latter are reproduced starting from a reference case and imposing growth assumptions. Next, the information of the root system, in terms of root length, density, root diameter profile, total number of roots, are used to estimate, through a RBM approach, the additional root tensile force, deriving it from the force-deformation theory of linear elasticity in a rigorous framework aimed to derive the additional shear resistance from the Mohr-Coulomb’s failure plane. 
The preliminary results demonstrated the capability of the root topological model of reproducing different types of root system; additional data are required to further validate the model, with regard to the growth conditions simulation. Similarly, laboratory test of root strength would allow to quantify the improvement derived from the rigorous method adopted to estimate the additional root strength.
Future European changes of extreme precipitation : What can we learn from inter-model cross-validation?
Authors: Schmith Torben , Thejll Peter , Boberg Fredrik , Berg Peter , Christensen Ole Bøssing , Christiansen Bo , Madsen Marianne Sloth , Christensen Jens Hesselbjerg
Published: March 2020

Severe precipitation events occur rarely and are often localized in space and of short duration, but are important for societal managing of infrastructure such as sewage systems, metros etc. Therefore, there is a demand for estimating expected future changes in the statistics of these rare events. These are usually projected using RCM scenario runs combined with extreme value analysis to obtain selected return levels of precipitation intensity. However, due to RCM imperfections, the modelled climate for the present-day usually has errors relative to observations. Therefore, the RCM results are ‘error corrected‘ to match observations more closely in order to increase reliability of results.

In the present work we evaluate different error correction techniques and compare with non-corrected projections. This is done in an inter-model cross-validation setup, in which each model in turn plays the role of observations, against which the remaining error-corrected models are validated. The study uses hourly data (historical & RCP8.5 late 21st century) from 13 models covering the EURO-CORDEX ensemble at 0.11 degree resolution (about 12.5 km), from which fields of selected return levels are extracted for 1 h and 24 h duration. The error correction techniques applied to the return levels are based on extreme value analysis and include analytical quantile-quantile matching together with a simpler climate factor approach.

The study identifies regions where the error correction techniques perform differently, and therefore contributes to guidelines on how and where to apply calibration techniques when projecting extreme return levels.
Holocene chronology and tephrostratigraphy for the varved record of Lake Diss Mere (UK)
Authors: Martin-Puertas Celia , Walsh Amy , Blockley Simon P.E , Biddulph George E. , Palmer Adrian , Ramisch Arne , Brauer Achim
Published: March 2020

The lacustrine record of Lake Diss Mere, Norfolk (UK) is 15 m long, and shows 4.2 m of finely-laminated sediments, which are present between 9 and 13 m of core depth. The microfacies analysis identified three major seasonal patterns of deposition (microfacies 1 – 3), which corroborate the annual nature of sedimentation throughout the whole interval. The sediments are diatomaceous organic and carbonate varves with an average thickness of 0.45 mm. Microfacies 1 consists of a pale layer made of authigenic calcite crystals and diatom frustules, and a dark layer composed of a planktonic diatoms and filaments of organic matter. Microfacies 2 is similar to microfacies 1 but includes a mono-specific diatom bloom layer preceding the calcite layer. Microfacies 3 are varves with an occasional very thin calcite layer and mono-specific diatom blooms in spring and autumn.

A total of 8252 varves were counted with an error of up to  27 varves. To tie the resulting floating varve chronology to the IntCal 2013 radiocarbon timescale, we used a Bayesian Deposition model (P_Sequence with outlier detection) on all available chronological data. The data included seven radiocarbon dates, six tephra layers with known radiocarbon ages, and the relative varve counts between dated points. The resulting age uncertainties are decadal in scale (95% confidence) and allow detailed comparisons to other high-resolution Holocene varved lake and ice-core records on absolute timescales. The potential for this record as a palaeoclimate archive for the British Isles is enhanced by the Glen Garry1(2172 ± 107 cal a BP) and OMH-1852(2667 ± 38 cal a BP) volcanic eruptions which lie amongst 3 further late-Holocene cryptotephra layers at ca 2400 cal a BP, 2540 cal a BP, and 3870 cal a BP, and a mid-Holocene cryptotephra layers at ca 6420 cal a BP. Initial investigations and geochemical characterisation suggest Icelandic eruption centres for these cryptotephra layers which are known to be present in sites in the British Isles and elsewhere in Europe.

1 Barber, K., Langdon, P., Blundell, A. Dating the Glen Garry tephra: a widespread late-Holocene marker horizon in the peatlands of northern Britain. The Holocene, 18: 31-43. 2008.

2 Plunkett, G.M., Pilcher, J.R., McCormac, F.G., Hall, V.A. New dates for first millennium BC tephra isochrones in Ireland. The Holocene, 14: 780-786. 2004
Where do crops take their water from? Using isotopic tracers in agricultural and agroforestry systems
Authors: Scandellari Francesca , Geris Josie , Hopp Luisa , Penna Daniele
Published: March 2020

 Improving the efficiency and sustainability in water resources management in agricultural and agroforestry systems is becoming increasingly important in the light of the increasing pressure on agro-food production due to the growing world population growth and the changing climatic conditions. In this context, achieving an accurate quantification of the proportions of different water sources (including irrigation) taken up by plants has important ecological and economic implications for water saving and utilization. Stable isotopes of hydrogen and oxygen in the water molecule are powerful and, nowadays, affordable tracers that can greatly help to identify and quantify the seasonal water uptake patterns by plants. This tool is largely adopted in natural systems (e.g., in ecohydrological applications in forested environments) but has not been fully exploited in agricultural and agroforestry ecosystems. Here, we outline the advantages and limitations of this technique and report some examples on how it can support more traditional approaches to understand root water uptake dynamics in agricultural and agroforestry systems. Finally, we present a vision for future challenges and new research lines using isotope tracers to investigate crop water use.
How alternating gaining and losing conditions along a low order agricultural stream govern the behavior of nitrogen species
Authors: Jimenez Fernandez Oscar , Osenbrück Karsten , Wang Zhe , Fleckenstein Jan , Schmidt Christian , Lüders Tillmann , Schwientek Marc
Published: March 2020

Perennial low order streams are normally well connected to shallow groundwater and therefore, they are among the first receptors of agricultural effluents. Understanding the processes governing the water quality in agricultural areas requires identifying sources of potential pollutants (such as nitrate), hotspots of biogeochemical reactivity and defining the different hydrologic flowpaths connecting groundwater and surface water. To this end, we have equipped an agricultural drainage system (Schönbrunnen) in south-western Germany with 3 stream gauging stations along a test segment of approximately 550 m and 33 piezometers in the adjacent shallow aquifer. Hydrological, hydrochemical, isotopic and microbiological variables have been monitored between August 2017 and December 2019 to spatially and temporally identify the controls of nitrogen cycling dynamics in our stream.

The Schönbrunnen generally loses water in its mid-segment and it gains in the lower part of the catchment, although this behavior showed strong seasonal variations, considering winter and summer as the two main annual seasons. The groundwater-streamwater (GW-SW) exchange flux, and the replacement of streamwater lost to the aquifer over a reach by shallow groundwater, defined as hydrologic turnover, was found to influence streamwater chemistry. The main groundwater flow directions were determined based on hydraulic head contour maps. We used them to characterize the nitrogen (N) species’ behavior along the flowpaths under two different hydrologic conditions: losing and gaining. Even though the losing condition at the midstream provides more favorable condition for N-species reduction at the GW-SW interface, reduction occurred also along gaining reaches. The isotope analyses of nitrate yielded data points plotting along the denitrification trend (slope of 0.5) in a dual isotope plot (15N-NO3- versus 18O-NO3-) for some of the sampling locations within the losing area. Comprehensive molecular approaches suggested a hotspot for denitrifying microbial communities in sediments of the losing stream reach. Along the GW flow path to the gaining area a depletion of nitrate was identified in concert with increasing sulfate and declining sulfide (H2S) concentrations. Sulfide-driven nitrate reduction was likely to occur under anoxic conditions in this part of the aquifer. In summary, the findings demonstrate, that hydrologic turnover does not only mean hydrological exchanges, but also triggers variations in water composition along the transition zone between groundwater and streamwater by linking both, mixing and reactive processes.
Advancing in Citizen Science Interoperability by testing standard components between Citizen Observatories
Authors: Masó Joan , Prat Ester , Cobley Andy , Matheus Andreas , Julià Núria , Jirka Simon , Klan Friederike , Tsiakos Valantis , Schade Sven
Published: March 2020

The first phase of the citizen science Interoperability Experiment organized by the Interoperability Community of Practice in the EU H2020 WeObserve project under the Open Geospatial Consortium (OGC) innovation program and supported by the four H2020 Citizen Observatories projects (SCENT, GROW, LandSense & GroundTruth 2.0) as well as the EU H2020 NEXTGEOSS project has finalized with the release of an Engineering Report in the OGC website. The activity, initiated by the European Space Agency (ESA), EC Joint Research Center (JRC), the Wilson Center, International Institute for Applied Systems Analysis (IIASA) and CREAF wanted to covered aspects of data sharing architectures for citizen science data, data quality, data definitions and user authentication. 

The final aim is to propose solutions for Citizen Science data to be integrated in the Global Earth Observation System of Systems (GEOSS). The solution is necessarily a combination of technical and networking components, being the first ones the focus of this work. The applications of international geospatial standards in current citizen science and citizen observatory projects to improve interoperability and foster innovation is one of the main tasks in during the experiment to achieve the final aim.

The main result was to demonstrate that OGC Sensor Observing Service (SOS) standard can be used for citizen science data (as already proposed in the OGC SWE4CS discussion paper) by implementing it in servers that were combined by visualization clients showing Citizen Science observations from different projects together. The adoption of SOS opened new opportunities for creating interoperable components such as a quality assessment tool. In parallel, an authentication server was used to federate three project observers in a single community. Lessons learned will be used to define an architecture for the H2020 COS4Cloud project. The second phase of the Interoperability Experiment has already started and developments and tests will be conducted by participants in the next 9 months. Some open issues identified and document in the Engineering Report will be addressed in the second phase of the experiment, including the use of a Definitions Server and the adoption of the OGC SensorThings API as an alternative to SOS. The second phase will finalize in September 2020 with a presentation in the Munich OGC Technical Committee meeting. The call for participation and additional contributions will remain for the whole duration of the activity
Drivers, climate sensitivity, and management of functional diversity in northeastern North America
Authors: Thom Dominik , Taylor Anthony , Seidl Rupert , Thuiller Wilfried , Wang Jiejie , Robideau Marie , Keeton William
Published: March 2020

The functional diversity (FD) represented by plant traits is fundamentally linked to the ecosystem’s capacity to respond to changes in the environment. Thus, there is an ongoing debate about including FD considerations in management plans to safeguard forests and their services to the society under climate change. However, incomplete scientific knowledge and difficulties to understand the concept of FD hinder the implementation of FD-based management approaches. Our study fills these knowledge gaps by (i) mapping the current distribution, (ii) analyzing the drivers, and (iii) testing the sensitivity of FD to projected increases in temperature and precipitation in northeastern North America. Following the stress-dominance hypothesis, we expected the strongest effect on FD from environmental filtering (i.e., climatic conditions) within our study region.

We combined a literature and database review of 44 traits for 43 tree species with terrestrial inventory data of 48,426 plots spanning an environmental gradient from northern boreal to temperate biomes. Employing multiple non-parametric models, we evaluated the impacts of 25 covariates on FD. Subsequently, we conducted a climate sensitivity analysis. The effect of rarity and commonness were tested for all outcomes using Hill numbers with different abundance weightings.

We identified FD hotspots in temperate forests and the boreal-temperate ecotone east and northeast of the Great Lakes. Forest stand structure explained most of the variation in FD. Elevated temperature increased FD in boreal, but lowered FD in temperate forests. Different species abundance weightings affected trait diversity distributions and drivers only marginally.

As environmental filtering was of secondary importance behind forest structure in explaining the trait diversity distribution of tree species in northeastern North America, our study provides only partial support for the stress-dominance hypothesis. Forest management can increase FD by promoting structural complexity. In addition, mixing species from functionally different groups identified in this study can enhance the response diversity of forests to an uncertain future.
Recycling of mercury pollution in the fluvial system - revitalize or not?
Authors: Hošek Michal , Matys Grygar Tomáš , Štojdl Jiří , Elznicová Jitka , Svoboda Jan
Published: March 2020

The catchments of the Kössein and the Röslau rivers (north-eastern Bavaria, Germany) was impacted by pollution from Chemical Factory Marktredwitz (CFM). The CFM produced Hg compounds for almost 200 years until the severe pollution of the factory surroundings and the Kössein River was revealed in the 1980s. The channel belt of the Kössein-Röslau rivers downstream the CFM is now one of the most severe Hg pollution hotspots in Central Europe. At the present days, more than 30 years after the factory abandonment, the Hg concentrations in fish muscles reach up to 6 mg/kg in the Skalka Reservoir, which acts as a sedimentary trap for that pollution.

The main vector for the actual fluvial recycling of Hg is suspended particulate matter (SPM) formed by the fluvial erosion of the channel belt. In previous work we found out that the Hg inventory in the Kössein-Röslau river system is approximately 20 t Hg deposited in a 22 km long channel belt, mainly as easily thermodesorbed form, perhaps natural organic matter bound Hg (NOM-Hg). Because the Kössein and the Röslau rivers still export SPM with mean concentrations of approximately 20 mg Hg/kg, revitalization options to stop Hg pollution recycling should be considered. We studied the Röslau River floodplain upstream the confluence with the Eger River, situated just upstream the inlet to the Skalka Reservoir. This locality is used for cattle grazing although Hg concentration up to 122 mg/kg can be found in some sediment strata and approximately 45 mg/kg is in topsoils. The locality has been investigated by geophysical methods ERT (electrical resistivity tomography) and DEMP (dipole electromagnetic profiling) to reveal the floodplain subsurface sedimentary architecture, because it is a key to find recent geomorphic traps for the polluted sediment. The floodplain was then sampled after drill coring, Hg analysis was performed by AMA-254 and element analysis by XRF. We found a close correlation between Zn and Hg concentrations, which facilitated the study of the pollution hotspot. We found three facies types of polluted sediments: channel belt (up to 122 mg Hg/kg), fills of shallow flood channels in floodplain (up to 73 mg Hg/kg), and top strata of overbank fines (up to 56 mg Hg/kg). The knowledge on the pollution distribution is essential for the future revitalization and protection measures.
Thermal thrust accelerations on LAGEOS satellites
Authors: Lucchesi David , Anselmo Luciano , Bassan Massimo , Lucente Marco , Magnafico Carmelo , Pardini Carmen , Peron Roberto , Pucacco Giuseppe , Visco Massimo
Published: March 2020

Thermal thrust forces are non-conservative forces that act on the surface of a satellite as a result of temperature gradients across its surface. In the case of the older LAGEOS satellite these kinds of perturbations have been well-known since the end of 80s. The main effects are due to the thermal inertia of the corner cube retroreflectors (CCRs) of the satellites with sources the Earth’s infrared radiation and the direct solar visible radiation modulated by the eclipses. However, the solar radiation reflected by the complex Earth-atmosphere system, i.e. the albedo, is also responsible for a non-uniform heating of the satellite surface. We reconsider such perturbations by means of a new thermal model for the satellites called LATOS (LArase Thermal mOdel Solutions), which is not based on averaged equations as those previously developed in the literature. Of course, in such analyses the attitude of the satellite plays an important key role; we modeled it by means of the LASSOS (LArase Satellites Spin mOdel Solutions) model for the evolution of the spin-vector that we have already developed within the LARASE (LAser RAnged Satellites Experiment) research program. We also included the contribution of the Earth’s albedo in the determination of the overall distribution of temperature on the surface of the satellites, that was not considered in previous works. The CERES (Clouds and the Earth’s Radiant Energy System) data have been used to account for this effect. The thermal thrust accelerations have been computed together with their effects on the orbital elements by means of the Gauss equations. These effects are compared with the orbit residuals of the satellites in the same elements, obtained by an independent Precise Orbit Determination (POD), in order to highlight the signature of the unmodeled effects. The improvement in the POD that can be achieved through a better modeling of the thermal thrust perturbations is of fundamental importance for the geophysical products that are determined by means of the analysis of the orbits of the two LAGEOS satellites. Similarly, the measurements in the field of fundamental physics that are obtained with these satellites can benefit from a more precise modeling of their orbit.
Dynamic groundwater recharge rates at field scale: how to successfully use soil moisture from cosmic-ray neutron sensing
Authors: Scheiffele Lena M. , Munz Matthias , Baroni Gabriele , Bauer Sonja , Oswald Sascha E.
Published: March 2020

Cosmic-ray neutron sensing (CRNS) is a non-invasive method that provides an average soil moisture for a large support volume (radial footprint up to 240 m, depth up to 80 cm) with high temporal resolution. It covers the most dynamic part of the vadose zone at a scale that is already a more substantial part of the landscape then local point measurements. This integral soil moisture value overcomes the limitations regarding issues of small-scale heterogeneity. Therefore, the use of CRNS soil moisture could improve the estimation of potential groundwater (GW) recharge at the field.

Besides the stochastic integration of point-scale soil moisture profiles, CRNS soil moisture estimates could be used for the inverse estimation of effective soil hydraulic properties by applying unsaturated soil hydrological models and to determine environmental fluxes such as GW recharge.

Within this study CRNS soil moisture is used to estimate the effective soil hydraulic properties within the model HYDRUS 1D. Resulting GW recharge represents the field scale because of the integrated nature of the soil moisture product, even though the model is calculating percolation fluxes for 1D - profiles. These integrated GW recharge fluxes are compared to established point scale methods of GW estimation using soil moisture from a distributed sensor network to inversely estimate the effective soil hydraulic properties within HYDRUS 1D.

CRNS is, however, sensitive to the vertical distribution of water content and this behavior should be explicitly considered. Two approaches are assessed further to account for that. On the one hand, a correction of CRNS, based on measured soil moisture profiles, is tested and CRNS soil moisture is directly used for recharge calculation in HYDRUS. On the other hand, the COSMIC-Operator, as implemented within HYDRUS, is used for calibrating the model by directly comparing neutron count rates from simulated soil moisture. Both approaches are assessed with respect to their ability to estimate natural groundwater recharge rates.