bluuebunny/crossref_metadata_2025 huggingface dataset:
Improving crop water use in West Africa in the context of climate change
Authors: Agoungbome Sehouevi Mawuton David , van de Giesen Nick , Annor Frank Ohene , ten Veldhuis Marie-Claire
Published: March 2020

Africa’s population is growing fast and is expected to double by 2050, meaning the food production must follow the cadence in order to meet the demand. However, one of the major challenges of agriculture in Africa is productivity (World Bank, 2009; IFRI, 2016). For instance, more than 40 million hectares of farmland were dedicated to maize in Africa in 2017 (approx. 20% of world total maize farms), but only 7.4% of the total world maize production came from the African continent (FAO, 2017). This shows the poor productivity which has its causes rooted in lack of good climate and weather information, slow technology uptake and financial support for farmers. In West Africa, where more than 70% of crop production is rain-fed, millions of farmers depend on rainfall, yet the region is one of the most vulnerable and least monitored in terms of climate change and rainfall variability. With a high uncertainty of future climate conditions in the region, one must foresee the big challenges ahead: farmers will be exposed to a lot of damages and losses leading to food insecurity resulting in famine and poverty if measures are not put in place to improve productivity. This study aims at addressing low productivity in agriculture by providing farmers with the right moment to start farming in order to improve efficiency and productivity of crop water use. By analyzing yield response to water availability of specific crops using AquaCrop, the Food and Agriculture Organization crop growth model, we investigate the crop water productivity variability throughout the rainy season and come up with recommendations that help optimize rainfall water use and maximize crop yield.
UAV-derived Estimates of Vertical and Horizontal Structure across Forest Density Gradients
Authors: Sankey Temuulen , Belmonte Adam
Published: March 2020

Restoring forest ecosystems and predicting forest response to projected climate change have become an increasingly high priority for land managers. Restoration and management goals require accurate, quantitative estimates of vertical and horizontal forest structure, which has relied upon either field-based measurements, manned airborne, or satellite remote sensing datasets. We use unmanned aerial vehicle (UAV) image-derived structure from motion (SfM) models and high resolution multispectral and thermal orthoimagery to: 1) quantify vertical and horizontal forest structure at both fine- (< 4 ha) and mid-scales (4-400 ha) across a forest density gradient, and 2) quantify horizontal structure, health, and survival rates in a genetics experimental garden also with a density gradient. In both cases, we find that UAV multispectral and thermal image-derived SfM model estimates of individual tree height and canopy diameter are most accurate in low-density conditions, with accuracies degrading significantly in high-density conditions. In addition, UAV thermal images demonstrate significant differences in tree health and survival rates among various populations and genotypes within a single species.  Mid-scale estimates of canopy cover and forest density follow a similar pattern across the density gradient, demonstrating the effectiveness of UAV image-derived estimates in low to medium-density conditions as well as the challenges associated with high-density conditions.
Contribution of Gravity to Lunar Science, Exploration and Resource Assessment
Authors: Zuber Maria T. , Smith David E.
Published: March 2020

The recent development of high-resolution models of the lunar gravity field based on data from the NASA GRAIL mission have been instrumental in gaining knowledge about the structure of the Moon, and particularly, of the upper crust. Beneath the outer layer GRAIL data reveal evidence of massive ancient dikes and past processes that no longer have any surficial expression due to heavy bombardment during the Moon’s post-accretional epoch that pulverized the shallow crust. The gravity field of this outer crust, with lower density and higher porosity than expected, also reveals anomalies that indicate the presence of regions of even lower density possibly indicating the existence of lava tubes, as well as regions of higher density where mass anomalies could conceivably indicate locations of resources. Lava tubes, long suspected of existing beneath the maria, are places protected from particle and EM radiation and therefore potential locations for safe location of humans.  Gravity anomaly regions are thus prime locations for exploration studies that could help sustain a human presence. The use of high-resolution  gravity in lunar exploration, as well as science, is a tool for survivability for human expeditions.
Mapping lake drainage and drained lake basins around Point Lay, Alaska using multi-source remote sensing data
Authors: Bergstedt Helena , Jones Benjamin , Walker Donald , Farquharson Louise , Breen Amy , Hinkel Kenneth
Published: March 2020

The North Slope of Alaska is a permafrost affected landscape dominated by lakes and drained lake basins of different sizes, depths and ages. Local communities across the North Slope region rely on lakes as a fresh water source and as locations for subsistence fishing, while industry relies on lakes as a source of water for winter transportation. Lake drainage events are often disruptive to both communities and industry that rely on being in close proximity to surface water sources in a region underlain by continuous permafrost. Drained lake basins of different ages can provide information on the past effects of climate change in the region. Studying past drainage events gives insight about the causes and mechanisms of these complex systems and benefits our understanding of lake evolution on the Arctic Coastal Plain in Alaska and the circumpolar Arctic as a whole.

Lakes and drained lake basins can be identified using high to medium resolution multispectral imagery from a range of satellite-based sensors. We explore the history of lake drainage in the region around Point Lay, a community located on the northern Chukchi Coast of Alaska, using a multi-source remote sensing approach. We study the evolution of lake basins before and after drainage events, their transformation from fishing grounds and water sources to grazing grounds and the geomorphological changes in the surrounding permafrost-dominated landscapes associated with these transitions.  

We build a dense and long time series of satellite imagery of past lake drainage events by including a multitude of remote sensing acquisitions from different sources into our analysis. Incorporating imagery from different sensors that have different temporal and spatial resolutions allows us to assess past drainage events and current geomorphological states of lakes and drained lake basins at different temporal and spatial scales. Point Lay is known to be an area where drainage events occur frequently and are of high relevance to the community. In August of 2016, the village drinking water source drained during a period of intense rainfall causing the village to seek alternative sources for a freshwater supply. Our results from the analysis of the remotely sensed imagery were shared directly with the community as part of a public seminar series in the Spring of 2020. We hope that results from our study near Point Lay, Alaska can contribute towards the selection of a new freshwater source lake for the village.
The biological darkening of the Greenland Ice Sheet: impacts of visible and UV light on the photosynthetic performance, metabolome and transcriptome of glacier algae
Authors: Halbach Laura , Benning Liane G. , Doting Eva L. , Hansen Martin , Jakobsen Hans , Lund-Hansen Lars C. , Haraguchi Lumi , Sorrell Brian K. , Zervas Thanassis , Anesio Alexandre M.
Published: March 2020

Large blooms of purple-brownish pigmented glacier algae cover the ablation zones of the Greenland Ice Sheet (GrIS) and amplify its melt by lowering the ice surface albedo and increasing its solar radiation absorption. The darkening effect of these Zygnematophycean algae can be mainly attributed to their phenolic pigments, which absorb in the visible (VIS) and UV light ranges. Currently, a mechanistic understanding of the factors regulating the production of these pigments and their implications for the large-scale biologically-driven albedo reduction on the GrIS is missing. Here, we reveal how light (VIS vs. UV range) controls the phenolic pigment production, endo- and exometabolome, gene expression and photosynthetic performance of glacier algae. Two different algal communities (a mixed natural microbial community collected from snow-free ice and a laboratory-grown community of the ice algae Mesotaenium berggrenii without its original dark pigmentation) were used for a set of in situ incubations on Mittivakkat glacier in SE-Greenland. Pulse-amplitude-modulated (PAM) fluorometry revealed an overall higher photosynthetic performance (electron transport rate) at higher irradiances for the field population containing purpurogallin-like pigments compared to the lab community without dark pigmentation. The lab population showed a low maximum quantum efficiency of photosystem II under in situ light conditions, indicating a photo-damaging effect from high intensities of UV light in the absence of purpurogallin-derived phenolic pigments. Our study highlights the intracellular shading effect by purpurogallin-derived pigments, which are key for the survival of glacier algae on the ice and forms a cornerstone of understanding the large-scale variability in the biological darkening of the GrIS.
Assessing the impacts of shale gas development on the water-energy nexus across the semiarid Mexico’s northeast
Authors: Arciniega-Esparza Saul , Breña-Naranjo Agustín , Hernández-Espriú Antonio , Pedrozo-Acuña Adrián
Published: March 2020

An intensification of water use for hydraulic fracturing (HF) to extract oil and gas from deep shale formations has been observed during the last years across the USA, increasing concerns about water resources management in water-limited regions around the world. At the same time, HF has been associated to several environmental and water quality/quantity impacts in many developed plays of USA, China and Canada, nevertheless, assessing impacts on emergent plays involves several difficulties since future development of HF is generally unknown and because of the lack of local data to evaluate water resources baselines.

In this work, we present a framework that combines the use of remote sensing derived data to assess the baseline of water resources and the development and application of a statistical model to project the development of HF activities. Remote sensing and global land surface model products of precipitation (CHIRPS), evapotranspiration (MODIS), recharge (WaterGAP model), infiltration and runoff (MERRA) and water storage (GRACE) were used to estimate water availability and the hydrological response of watersheds and aquifers. Scenarios of HF were generated using a statistical model that simulates HF water requirements, hydrocarbon production, flowback-produced water and economic trends, among others factors that influence the HF development.

The proposed framework was applied to evaluate the impacts of HF development on the water energy-nexus at the transboundary Eagle Ford play, located across Mexico’s northeast, a water-limited region that contains substantial reserves of shale gas.

Scenarios were generated following two economic projections and assuming water use trends and historical HF development from the Eagle Ford, Barnett and Haynesville plays, in Texas, which are geologically similar to the Mexican Eagle Ford play.

Results suggested that the higher impacts on the water-energy nexus in Mexico resulted from reported trends in Eagle Ford, Texas, with ~14,000 wells drilled in ten years and an accumulative water use volume of ~450 millions cubic meters, representing about ~69% of the annual groundwater concessions for municipal use.

The framework presented in this work can be used in other plays around the world to assess the impacts of HF on water resources and their implications in its water-energy nexus.
Spatial variability of precipitation extremes over Italy using a fine-resolution gridded product
Authors: Moccia Benedetta , Papalexiou Simon Michael , Russo Fabio , Napolitano Francesco
Published: March 2020

Analysis of extreme precipitation events has been the cornerstone of statistical hydrology and plays a crucial role in planning and designing hydraulic structures. Extreme value theory offers a solid theoretical basis for using the Generalized Extreme Value (GEV) distribution as a probabilistic model to describe precipitation annual maxima. Several large-scale studies investigate the properties of the GEV distribution in point measurements offering insights on its spatial variability. Yet the sparse station network in most regions, as anticipated, leads to sparse point estimates that may distort the actual spatial patterns of the GEV’s parameters. Here, we use fine-resolution satellite-based gridded product, that is, the CHIRPS v2.0, to investigate the spatial variation of the GEV distribution over Italy. Our results show that the GEV shape parameter forms clear spatial patterns. We use these results to offer robust estimates and create maps for different return periods all over Italy.
Paraglacial responses in deglaciating cirque walls: Implications for rockfall magnitudes/frequencies and rockwall retreat
Authors: Hartmeyer Ingo , Delleske Robert , Keuschnig Markus , Krautblatter Michael , Lang Andreas , Schrott Lothar , Otto Jan-Christoph
Published: March 2020

Over the past 150 years almost half of the glacier volume disappeared in the European Alps. Besides glacier retreat, ice surface lowering reflects much of the volume loss and uncovers the adjacent rockwalls. In steep glacial cirques, this process exposes rock to atmospheric conditions for the very first time in many millennia. Instability of rockwalls has long been identified as one of the direct consequences of deglaciation, but so far cirque-wide quantification of rockfall at high-resolution is missing and the proportional contributions of low-, mid- and high magnitude rockfalls have remained poorly constrained. 
We use terrestrial LiDAR to establish a rockfall inventory for the permafrost-affected rockwalls of two rapidly deglaciating cirques in the Central Alps of Austria (Kitzsteinhorn). During six-year monitoring (2011-2017) 78 rockwall scans were acquired. Overall, we registered 632 rockfalls ranging from 0.003 to 879.4 m³, which concentrate along pre-existing structural weaknesses. 60 % of the rockfall volume detached from less than ten vertical meters above the glacier surface, indicating enhanced rockfall over tens of years following deglaciation. 
Antecedent rockfall preparation is assumed to start when the rockwall is still ice-covered: Inside the Randkluft (gap between cirque wall and glacier) sustained freezing and sufficient water supply likely cause enhanced weathering and high plucking stresses. Following deglaciation, pronounced thermomechanical strain is induced and an active layer penetrates into perennially frozen bedrock, likely contributing to the observed paraglacial rockfall increase close to the glacier surface. 
Observed mean cirque wall retreat of 1.9 mm a-1 ranks in the top range of reported values and is mainly driven by enhanced rockfall from the lowermost, freshly deglaciated sections of the investigated rockwalls. Rockfall magnitude-frequency distribution, which has never been quantified before for deglaciating cirques, follows a distinct negative power law distribution over four orders of magnitude. Magnitude-frequency distributions in glacier-proximal and glacier-distal rockwall sections differ significantly due to an increased occurrence of large rockfalls in recently deglaciated areas. The present study thus demonstrates how recent climate warming shapes glacial landforms, controls spatiotemporal rockfall variation in glacial environments and indicates an exhaustion law over decades for rockfall activity immediately following deglaciation crucial for future hazard assessments.
Global and regional geomagnetic variabilities recorded in late Quaternary sediments from the west Iberian Margin
Authors: Xuan Chuang , Nichols Matthew , Stoner Joseph , Richter Carl , Acton Gary
Published: March 2020

High-resolution palaeomagnetic records preserved in sediments (especially those that are well dated) provide valuable continuous information on past changes in Earth’s magnetic field. These data are essential for us to develop better understanding on the dynamics and causes of geomagnetic changes at various time scales. In this study, we conducted palaeomagnetic analyses on continuous u-channel samples collected from well-dated late Quaternary sediment sequences cored in the west Iberian Margin during Integrated Ocean Drilling Program (IODP) Expedition 339. Natural remanent magnetisations (NRM) as well as a suite of laboratory-induced magnetisations of the samples were measured at 1-cm interval resolution on a superconducting rock magnetometer before and after stepwise alternating field (AF) demagnetisation. NRM demagnetization data of the samples reveal a very stable and well-defined primary magnetisation component. Chronology of the studied cores is well constrained and tied to the polar ice cores as well as the absolutely dated Asian speleothem records. Average sedimentation rates of the studied cores range between ~10 cm/kyr to over 70 cm/kyr. Relative palaeointensity (RPI) records reconstructed from these sediments, when placed on the acquired age models, correlate well with other global and regional RPI records on time scales of ~10 kyr or longer. RPI features recorded at higher sedimentation rate sites appear slightly younger (a few hundreds to a couple of thousand years), possibly due to effects of the sediment magnetisation lock-in process. These Iberian Margin RPI records also show common millennial to multi-millennial scale variabilities, especially after deconvolution and correction of the lock-in induced age offset.
Uncertainties in forecasting orographic flows
Authors: Ólafsson Haraldur
Published: March 2020

The accuracy of a large set of high-resolution wind speed forecasts with different lead times is assessed for different parts of orographic flows, including upstream blockings, gap winds, corner winds, wakes and downslope winds.  The by far largest errors are in areas of downslope windstorms, but there are also considerable errors in the other parts of orographic disturbances to the flow and they are greater than in non-orographic flows in the same region.  The errors are discussed in view of the different dynamics and kinematics of the flows.  They are partly related to intermittency of i.e. gravity waves as well as strong spatial gradients in the wind field.
Seismic Structure and Tectonic Evolution of Borneo and Sulawesi
Authors: Linang Harry Telajan , Gilligan Amy , Jenkins Jennifer , Greenfield Tim , Rawlinson Nick
Published: March 2020

Southeast Asia (SEA) is one of the most active tectonic regions on the planet due to its convergent setting, which accommodates rapid northward motion of the Indo-Australian plate and westward motion of the Philippines Sea plate. This activity gives rise to intense seismicity along the convergent plate margins in and around SEA, including the Sunda Arc, which wraps its way around the southern margin of the Indonesian archipelago.

Borneo is located at the centre of SEA, on the leading edge of the Sundaland block of the Eurasian plate, and exhibits lower rates of seismicity when compared to the surrounding regions due to its intraplate setting. Sulawesi, an island which lies adjacent to Borneo in the east, is characterised by intense seismicity due to multiple subduction zones in its vicinity. The tectonic relationship between the two islands is poorly understood, as is the provenance of their lithosphere, which may have Eurasian or East Gondwana origin.

The aim of this presentation is to showcase recent receiver function results from temporary and permanent broadband seismic stations in the region, which can be used to help improve our understanding of the structure of the crust and the mantle lithosphere beneath Borneo and Sulawesi. H-K stacking, receiver function migration and inversion are all applied in an effort to determine robust crustal thickness estimates and variations in shear wavespeed with depth. Our preliminary results from Borneo indicate that the crust beneath Sabah (northern Borneo), which is a post-subduction setting, appears to be much more complex than the rest of the island. Furthermore, we find that crustal thickness varies between different tectonic blocks defined from surface mapping, with the thinnest crust (24 km thick) occurring beneath Sarawak in the northwest.
Isotopic analyses of the Middle Miocene evaporite assemblage and its fluid inclusions (Praid, Transylvanian Basin, Romania)
Authors: Gelencsér Orsolya , Palcsu László , Futó István , Szabó Csaba
Published: March 2020

The objective of this study is to constrain the formation conditions of deposition of the Middle Miocene marine evaporite in the Transylvanian Basin (TB).  The salt rock, formed during the Badenian Salinity Crisis (BSC), consists principally of halite (> 90%).  Representative samples were collected from Praid salt diapir.

Detailed petrographic study was carried out in order to distinguish primary features of the salt rock and to exclude secondary movements and their impacts.  Two types of salt rock can be distinguished: 1/ massive grey salt with large, elongated halite crystals, containing primary fluid inclusions (FIp), surrounded by submicrometer size halite grains and clay matrix, and 2/ layered salt building up greyish (clay rich) and white (clear halite) layers.  This type has quasi mosaic structure and contains very rarely FIps.

The primary fluid inclusions in halite, containing aqueous solutes, are expected to record compositions and isotopic characters of paleo-seawater during the BSC of the Paratethys.  Beside halite, authigenic anhydrite and dolomite are also present, which precipitated in marine environment and their compositions also reflect the geochemical conditions of the seawater.

Microthermometry of FIp in both types of halite shows low homogenization temperature (10-24 °C) which is typical for marine environment.  Isotopic characteristics of FIp are -15.55 – -7.07 ‰ for δ18O and -87,9 – -74.17 ‰ for δ2H.  Sulfate isotope values measured in anhydrite are ranging δ34S 20.4 – 22.4 ‰ and δ18O 12.9 – 14.5 ‰ that coincide with the Middle Miocene Outer Carpathians salt deposits (Halas & Krouse, 1981) and support evaporated seawater origin.  The geochemical signatures (Fe-zonation) and isotopic characters (δ18O -7.07 – -4.55 ‰ and δ13C -9.03 – -8.31 ‰) of the rombohedral translucent dolomite suggest mainly meteoric origin.  They possibly precipitated from an upper level of the seawater.  All of these isotopic and geochemical characters of the evaporite reveal a complex restricted hydrogeologic evolution environment.
Ice-nucleating Macromolecules from Alpine Forests as Possible Contributors to Cloud Glaciation Processes
Authors: Seifried Teresa M. , Bieber Paul , Felgitsch Laura , Grothe Hinrich
Published: March 2020

Ice nucleation in the atmosphere leads to the formation of mixed-phase as well as cirrus clouds in the upper troposphere. Cloud glaciation can either occur homogeneously at temperatures below -38°C or heterogeneously in the presence of ice-nucleating particles (INPs) at temperatures higher than -38°C. Depending on the aggregate state of a cloud, it’s life time and radiative properties vary and thus affect regional and global climate. The influence of biogenic INPs on atmospheric processes as well as the transport of these particles from the land surface to the atmosphere remains elusive. Several plants from boreal and alpine forests are known to contain ice-nucleating macromolecules (INMs) to survive in extreme conditions. However, less is known about chemical characteristics and actual emission rates of such INMs.

We present here our investigation of surface extracts from different tree tissues (Betula pendula and Pinus sylvestris). We were able to extract INMs from nearly all samples. Furthermore, we analyzed the ability of these INMs to be released during rain fall events in-situ. To investigate possible transport mechanisms of INMs from the canopy of studied tree species to the atmosphere we sampled aerosols with two small scale drones, carrying our self-build sampling systems called DAPSI (Drone-based Aerosol Particles Sampling Impinger/Impactor). Results indicate that birches and pines outline an important source of airborne biogenic INPs.
Mantle convection beneath East Asia under global mantle convection spherical framework
Authors: Zheng Qunfan , Zhang Huai
Published: March 2020

East Asia is a tectonically active area on earth and has a complicated lithospheric deformation due to the western Indo-Asian continental collision and the eastern oceanic subduction mainly from Pacific plate. Till now, mantle dynamics beneath this area is not well understood due to its complex mantle structure, especially in the framework of global spherical mantle convection. Hence, a series of numerical models are conducted in this study to reveal the key controlling parameters in shaping the present-day observed mantle structure beneath East Asia under 3-D global mantle flow models. Global mantle flow models with coarse mesh are firstly applied to give a rough constraint on global mantle convection. The detailed description of upper mantle dynamics of East Asia is left with regional refined mesh. A power-law rheology and absolute plate field are applied subsequently to get a better constraint on the related regional mantle rheological structure and surficial boundary conditions. Thus, the refined and reasonable velocity and stress distributions of upper mantle beneath East Asia at different depths are retrieved based on our 3-D global mantle flow simulations. The derived large shallow mantle flow beneath the Tibetan Plateau causes significant lithospheric shear drag and dynamic topography that result in prominent tectonic evolution of this area. And the Indo–Asian collision may have induced mantle flow beneath the Indian plate and the different velocity structures between the asthenosphere and lithosphere indicate the shear drag of asthenospheric mantle. That may explain the reason that Indo–Asian collision has occurred for 50 Ma, and this collision can still continue to accelerate uplift in the Tibetan plateau. Finally, we also consider the possible implementations of 3-D numerical simulations combined with global lithosphere and deep mantle dynamics so as to discuss the relevant influences.
A Buoyant Eifel Mantle Plume Revealed by GPS-Derived Large-Scale 3D Surface Deformation
Authors: Kreemer Corné , Blewitt Geoffrey , Davis Paul
Published: March 2020

 The Eifel hotspot is one of the few known active continental hotspots. The evidence is based on volcanism as recent as 11ka and a seismic velocity anomaly that shows a plume-like feature downward to at least the upper transition zone. However, the volcanism lacks a clear space-time progression of activity, and evidence for surface deformation has been ambiguous. Here, we show that the greater area above the Eifel plume shows a distinct and significant surface deformation anomaly not seen anywhere else in intraplate Europe. We use GPS data of thousands of stations in western Europe to image contemporary vertical land motion (VLM) and horizontal strain rates. We show significant surface uplift rates with a maximum of ~1.0 mm/yr (after subtracting the broader-scale VLM predicted by glacial isostatic adjustment) roughly centered on the Eifel Volcanic Field, and above the mantle plume. The same area that uplifts also undergoes significant N-S-oriented extension of ~3 nanostrain/yr, and this area is surrounded by a radial pattern of shortening. River terrace data have revealed tectonic uplift of ~150–250 m of the Eifel since 800 ka, when recent volcanism and uplift reactivated, which would imply an average VLM of 0.1–0.3 mm/yr since that time. Our VLM results suggest that the uplift may have accelerated significantly since Quaternary volcanism commenced. The remarkable superimposition of significant uplift, horizontal extension, and volcanism strongly suggests a causal relationship with the underlying mantle plume. We model the plume buoyancy as a half-space vertical force applied to a bi-modal Gaussian areal distribution exerted on a plane at 50 km depth. Our modelling shows a good regional fit to the long-wavelength aspects of the surface deformation by applying buoyancy forces related to the plume head at the bottom of the lithosphere. From our spatially integrated force and the first-order assumption that the plume has effectively been buoyant since 250 ka (to explain Quaternary uplift) or 800 ka (at today’s rate), we estimate that a 360 km high plume requires density reduction of 57-184 kg m-3 (i.e., ~0.7-5.6% of a 3300 kg m-3 dense reference mantle), which is consistent with observed seismic velocity reductions. Finally, we note that the highest extension rates are centred on the Lower Rhine Embayment (LRE), where intraplate seismicity rates are high, and where paleoseismic events increased since 800 ka. We suggest that the surface uplift imposed by the Eifel plume explains the relatively high activity rate on faults along the LRE, particularly since the N-S extension would promote failure on the NW-SE trending faults in the LRE.
What is respiration - response to glucose addition, presence of plant roots and differences across biomes
Authors: Dijkstra Paul , Chuckran Peter F. , Hungate Bruce A. , Schwartz Egbert , Glavina del Rio Tijana , Eloe-Fadrosh Emiley
Published: March 2020

Respiration is likely the most often measured process in soil ecology. It is used as a general measurement of soil activity, and physiologically related to microbial maintenance requirements, growth, and soil organic matter production via biochemical efficiency and CUE.

Genomic tools are increasingly used in soil ecology for measurement of community composition, and functional analysis of communities, and when combined with stable isotopes, can be used to infer activities, either of the whole community or of individual taxa. However, relating genomic or gene-expressed functions to whole ecosystem processes, such as respiration, remains a conceptual and practical problem.

We analyzed the biochemical processes related to respiration and determine how, during a short soil incubation experiment in the presence of glucose, these processes change. Furthermore, we will show how gene and transcript abundances of respiratory processes vary across more than 4000 soil and rhizosphere samples in forests and grasslands and other biomes.  

Results illustrate the treasure trove of biochemical information available to us in the form of metagenomes and metatranscriptomes.
Numerical behavior of a coupled surface/subsurface, flow/transport hydrological model
Authors: Paniconi Claudio , Lauvernet Claire
Published: March 2020

Integrated surface/subsurface hydrological models (ISSHMs) are by now widely used in research and applied hydrology. While most studies have so far focused on water flow alone, ISSHMs that include also solute transport are beginning to get attention (e.g., Scudeler et al., 2016, doi:10.5194/hess-20-4061-2016; Gatel et al., 2019, doi:10.1016/j.envsoft.2018.12.006). Numerous numerical challenges are associated with these "doubly coupled" systems: correct treatment of surface boundary conditions and other mass and flux exchange terms; appropriate time stepping schemes across subsystems that are characterized by different dynamic time scales and often also widely different numerical discretization approaches; performance assessments that can be highly sensitive to the response variables of interest; and so on. We will illustrate some of these challenges via test case simulations of an experimental hillslope using the CATHY (CATchment HYdrology) model (Camporese et al., 2010, doi:10.1029/2008WR007536; Weill et al., 2011, doi:10.1016/j.advwatres.2010.10.001). The boundary condition-based coupling strategy used in this model (Putti and Paniconi, 2004, doi:10.1016/S0167-5648(04)80152-7) has been shown to be mathematically rigorous and mass-conservative for the flow model (Sochala et al., 2009, doi:10.1016/j.cma.2009.02.024). The convergence-based time step adaptation strategy used for the nonlinear flow equation (Paniconi and Putti, 1994, doi:10.1029/94WR02046) is likewise thoroughly tested (e.g., D'Haese et al., 2007, doi:10.1002/fld.1369) and widely used. Nonetheless, these schemes, and analogous approaches used in other ISSHMs, need to be adapted and thoroughly tested for coupled systems that include solute transport.
Challenges in constructing a high-resolution, multi-site, and multivariate weather generator and potential solutions
Authors: Li Xin
Published: March 2020

A reliable simulation of the spatiotemporal characteristics of the meteorological field is of great significance for hydrological impact studies. To approach this target, a number of weather generators (WGs) have been developed over the past few decades. However, a detailed literature review shows that currently developed WGs are subject to one or several aspects of the following limitations: (1) low spatial and temporal resolutions to describe the real spatiotemporal dynamics of meteorological processes; 2) incapability to simulate a spatially coherent, temporally consistent, and physically meaningful meteorological field; and 3) inability to extend into the future in a climate change context. To tackle these problems, this study proposes some potential solutions: (1) using the multi-site multivariate WGs (MMWGs) to simulate the spatial, temporal, and inter-variable dependencies in the meteorological field; (2) coupling the MMWGs with the resampling-based algorithms to generate high-resolution spatiotemporal meteorological data; and (3) perturbing the parameters of the distribution and dependency models based on the future climate projection. A case study is carried out and shows that the proposed solutions are effective in addressing the aforementioned challenges. These findings could assist in developing high-resolution MMWGs for weather simulation and impact assessment.
Climate and soil type effects on crop residue decomposition
Authors: Gregorich Ed , Beare Mike , Curtin Denis , Janzen Henry , Ellert Ben , Helgason Bobbi
Published: March 2020

Crop residues are an important resource for maintaining soil productivity. The decay of crop residues is linked to many ecosystem functions, affecting atmospheric CO2, nutrient release, microbial diversity, and soil organic matter quality. The rate of decay, in turn, is regulated by soil type, management, and environmental variables, some of which will be changing in the future. Our objective in this study was to evaluate effects of soil type, climate, residue placement on the decomposition and retention of residue-derived C. 13C-labelled barley straw was either placed at the surface or mixed to 10 cm in soils at four sites in Canada and one site in New Zealand representing different soil types and climates. Soils were collected periodically over 10 yr to determine 13C remaining. The loss of C from crop residues occurred quickly, most (70-75%) within the first 2 yrs but with only 5-10% remaining after 10 yrs. There were large losses of C from the mixed treatments within the first year, with 20-50% lost after 6 months over winter and 50-70 % lost after one year; after that decomposition slowed. Temperature was the single most important factor regulating the rate of residue decay. Thermal time, expressed as cumulative degree days, explained more of the variability in residue C recovered than time (in calendar years). Slower decay of surface-placed residues may be attributed to lower mean annual precipitation at those sites. Thermal time is a robust, consistent way of predicting crop residue decay rates (or C storage) for comparing C kinetics across sites with different soils and climates.
Subsurface targets detection using Faster R-CNN for Unmanned Aerial Vehicle Magnetic Survey
Authors: Zheng Yaoxin , Zhang Xiaojuan , Mu Yaxin , Xie Wupeng
Published: March 2020

Unmanned Aerial Vehicle (UAV) has become a viable platform for magnetic surveys, but the interference generated during flight and lack of the interpretation method for survey data limits its application. In this paper, we present a structure of a half-fixed boom for the UAV-magnetometer system. Compared to suspend the magnetometer on a long rope or cable, our new structure reduces interference and positional error meanwhile increases flight stability. The interference field was removed through compensation based on leveling, with root mean square error significantly reduced from 2.7889 nT to 0.2809 nT. The Faster R-CNN network was adapted for the detection of subsurface buried objects (i.e. Unexploded Ordnance) in UAV magnetic surveys, our Faster R-CNN object detection network is composed of a feature extraction network followed by two subnetworks, the feature extraction network we use is a pre-trained CNN called ResNet-50, the first subnetwork is a region proposal network (RPN) and the second subnetwork is trained to predict the actual class of each object proposal. A labeled dataset that contains 740 images was used for training and each image contains one or more labeled instances of mag anomaly, data augmentation is used by randomly flipping the image and associated box labels horizontally to improve network accuracy, the trained object detector was evaluated on both simulated and field test images. All implementations in this work were accomplished through MATLAB Deep Learning Toolbox using a PC with a GPU compute capability 7.5. Preliminary results reveal that the proposed technique can automatically confirm the number of subsurface targets, in the meantime results from different field tests show its robustness. Significant improvements have made compared to traditional computer vision methods and hence become quite promising to be applied in the field of UAV magnetic survey.
Leaf nitrogen distribution within canopies is (also) optimal
Authors: Wang Han , Prentice Colin , Keenan Trevor , Niinemets Ülo , Stenseth Nils
Published: March 2020

The distribution of leaf nitrogen (NL) within canopies has been discussed for decades in relation to the optimality hypothesis that predicts coordination of carboxylation capacity with absorbed light. Although an optimal (that is, proportional) response of both carboxylation capacity and NLto light is extensively supported by field observations of variation among sites, the observed saturation curve of NLwithin canopies seems to challenge the generality of that response. By considering dynamic light regimes, we propose an optimality-based theory that successfully reconciles the apparent conflict of observed NLdistribution within and between canopies. This theory proposes that due to the highly uneven temporal distribution of sun flecks, the light level to which understory leaves acclimate is much higher than the average light level. This proposition leads to a saturation curve for the vertical distribution of NL. Our within-canopy data analysis supports this theory. Understorey leaves require significantly less NLto achieve photosynthetic capacity as an acclimation to sun flecks. The contribution of structural and photosynthetic components to NLpredicted by the theory is quantitatively and consistently supported by global datasets of variation both within and between canopies.
Sill Processes in the Saguenay Fjord
Authors: Guay Jérôme , Bourgault Daniel , Bluteau Cynthia , Chavanne Cédric , Galbraith Peter , Gostiaux Louis
Published: March 2020

The Saguenay Fjord is a 110 km long and 250 m deep (max depth) multi-silled glacial valley that connects the Saguenay River at its head with the St. Lawrence Estuary at its mouth. The bathymetry is characterized with 3 sills: a shallow 20-m deep sill at the mouth, an intermediate 60-m deep 20 km landward sill and a deep 120-m sill 35 km landward. These sills separate 3 basins, the outer, the intermediate and the inner basins. The circulation in the fjord is forced by the Saguenay River at its head that brings freshwater, large tides (up to 6 m range) at its mouth that brings salt water and by wind. The large-scale circulation has been characterized by three seasonally dependent regimes during which the deep, intermediate and subsurface waters of the inner basin are being renewed, respectively, during early winter, summer and late winter. There are indirect indications that those regimes are determined by turbulent processes occurring locally at each of these three sills. Here, we carried out a field experiment to more directly investigate the detailed dynamics of tidally-driven sill processes and water mass modifications occurring across these three sills. Our measurements provide to date the most accurate and complete description of the stratified tidal flow structures around these sills. We also found that an internal hydraulic jump seems to form every ebb tide on the seaward side of the intermediate sill but not during flood tide on the landward side. Research is ongoing to better understand this asymmetry but our hypothesis is that it is the presence of a salty pool landward of the sill that prevents the formation of a hydraulic jump, a process that may be similar to that documented in Knight Inlet (British Columbia, Canada).
Vulnerability assessment of the Trinity Aquifer in Texas due to sulfonamides antibiotics leaching to groundwater for
Authors: Zhang Kaiyi , Mendoza Itza
Published: March 2020

Texas has the largest population of cattle farming and the highest production of poultry farming across the United States. In northeastern region, antibiotics have been widely used in Concentrated Animal Feeding Operations (CAFO) as veterinary pharmaceuticals (VP). Not fully metabolized and excreted antibiotics have caused soil pollution and resulted groundwater contamination. Sulfonamides’ high excretion rate from animals, low sorption to soils, and impact on nitrate-reducing bacteria for nitrate reduction capabilities, enhance leaching and secondary pollution from inherent nitrate-N contamination. However, there is a limited understanding of sulfonamides transport from the surface to groundwater. This research assessed the Trinity Aquifer vulnerability by incorporating major hydrogeological factors that affect and control the groundwater contamination using GIS-based DRASTIC along with major chemical factors using HYDRUS solute transport modeling. The study reclassified and refined subareas with different vulnerability potentials by overlaying various spatially referenced digital data layers. Additionally, sulfonamides transport was simulated for different vulnerable scenarios to estimate persistence of the antibiotic and potential concentrations reaching the aquifer, developing predicted methods to prevent, mitigate and remediate groundwater contamination caused by sulfonamides antibiotics.

 
Global Wave Data Assimilation Model using Optimal Interpolation Method
Authors: Kim Kyeong Ok , Kim Hanna , Jung Kyung Tae , Kim Young Ho
Published: March 2020

To construct a reanalyzed global ocean wave data set with improved accuracy, which is important for the better understanding and simulation of various near-surface ocean dynamics, a data assimilation method has been embedded to the global spectral wave model based on WW3. The major factors controlling the wave simulation accuracy are the wind condition and the parameterization on the wave energy development, dissipation and nonlinear processes between wave components. However, the atmospheric prediction accuracy is still not sufficient, and the parameterization cannot be generalized due to the local geographic conditions.

In detail, the data assimilation using the optimal interpolation method has been applied, verification through the comparison with satellite altimeters and buoy observations has been made with examination of the data assimilation effects. The significant wave heights computed by the integration of wave energy spectra are showed to be quite similar with observed results. However, the wave periods and directions related to the shape of wave energy spectra are not sufficiently comparable. Generally there have been difficulties in predicting the propagation of long period waves such as swells.

The wave energy spectra on wave number and direction domains was multiplied by optimal interpolation method with the ratio of observed significant wave heights on first guessed simulated results. The energy spectra was thereafter shifted by the difference between simulated and observed peak wave periods and directions. From then examination of the reanalysis simulation during 1 year, it could be seen that the accuracy of the model with the data assimilation shows better results than that without data assimilation.
Long-term Observations of Atmospheric Speciated Mercury at a Coastal Site in the Northern Gulf of Mexico during 2007–2018
Authors: Ren Xinrong , Luke Winston , Kelley Paul , Cohen Mark , Olson Mark , Archer Michael , Stein Ariel
Published: March 2020

Atmospheric mercury species (including gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particulate-bound mercury (PBM)), trace pollutants (including O3, SO2, CO, NO, NOY and black carbon), and meteorological parameters have been continuously monitored since 2007 at an Atmospheric Mercury Network (AMNet) site located on the northern coast of the Gulf of Mexico at the Grand Bay National Estuarine Research Reserve (NERR) in Moss Point, Mississippi. For the data collected between 2007 and 2018, the average concentrations and standard deviations were 1.39 ± 0.22 ng m-3 for GEM, 5.1 ± 10.2 pg m-3 for GOM, 5.9 ± 13.0 pg m-3 for PBM, and 309 ± 407 ng m-2 wk-1 for mercury wet deposition, with interannual trends of -0.009 ng m-3 yr-1 for GEM, -0.36 pg m-3 yr-1 for GOM, 0.18 pg m-3 yr-1 for PBM, and 2.8 ng m-2 wk-1 yr-1 for mercury wet deposition. The trends are statistically significant for GEM and GOM, but not statistically significant for PBM and mercury wet deposition. Diurnal variation of GEM shows lower concentrations in the early morning due to GEM depletion likely due to plant uptake in high humidity events and slight elevation during the day likely due to downward mixing of higher concentrations of GEM in the air aloft to the surface. Seasonal variation of GEM shows higher levels in winter and spring and lower levels in summer and fall. Diurnal variations of both GOM and PBM show broad peaks in the afternoon likely due to photochemical oxidation of GEM. Seasonally, PBM measurements exhibit higher levels in winter and early spring and lower levels in summer, while GOM measurements show high levels in late spring/early summer and late fall and low levels in winter. The seasonal variation of mercury wet deposition shows higher values in summer and lower values in winter due to higher precipitation amounts in summer than in winter. As expected, anticorrelation between Hg wet deposition and the sum of GOM and PBM but positive correlation between Hg wet deposition and rainfall were observed. Correlation among GOM, ozone, and SO2 suggests two possible GOM sources: direct emissions and photochemical oxidation of GEM with the possible influence of boundary dynamics and seasonal variability. This study indicates that the monitoring site, which is located in a coastal environment of the Gulf of Mexico, might experience impacts from mercury sources that are both local and regional in nature.