bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of Inorganic Particles of Sedimentary Origin on Global Dissolved Iron and Phytoplankton Distribution
Authors: Beghoura H. , Gorgues T. , Aumont O. , Planquette H.F. , Tagliabue A. , Auger P.‐A. 
Published: November 2019

AbstractIron is known to be the limiting nutrient for the phytoplankton growth over ~40% of the global ocean and to impact the structure of marine ecosystems. Dissolved iron (DFe) is assumed to be the only form available to phytoplankton while particulate iron (PFe) has mostly been considered for its role in the biogenic iron remineralization and induced scavenging. Therefore, most studies focused on the nature of DFe external sources to the ocean (i.e., eolian dust, riverine fluxes, hydrothermal sources, and sediment) and their quantification, which still remain uncertain. Among these external sources, the sedimentary sources have been shown to be underestimated. Moreover, the iron supply from sediments has been documented to be often larger in the particle fraction. Here we test the impacts of an iron sediment source of inorganic particulate iron (PFeInorg) on global DFe and phytoplankton distribution. We use experimentally acquired knowledge to test a parameterization of a PFeInorg pool in a global biogeochemical model and compare with published indirect estimation. Depending on the parameterization of its dissolution and sinking speed, the PFeInorg can noticeably enrich water masses in DFe during its transport from the sediment to the open ocean, notably in regions not usually accessible to external DFe inputs. Indeed, the fact that DFe is prone to scavenging reduces the impact of equivalent Fe inputs from sediments in the dissolved form in those regions far from the sediment sources. PFeInorg thereby has the potential to fuel the phytoplankton growth in offshore regions impacting the coastal‐offshore chlorophyll gradient.
Black Carbon and Inorganic Aerosols in Arctic Snowpack
Authors: Mori Tatsuhiro , Goto‐Azuma Kumiko , Kondo Yutaka , Ogawa‐Tsukagawa Yoshimi , Miura Kazuhiko , Hirabayashi Motohiro , Oshima Naga , Koike Makoto , Kupiainen Kaarle , Moteki Nobuhiro , Ohata Sho , Sinha P.R. , Sugiura Konosuke , Aoki Teruo , Schneebeli Martin , Steffen Konrad , Sato Atsushi , Tsushima Akane , Makarov Vladimir , Omiya Satoshi , Sugimoto Atsuko , Takano Shinya , Nagatsuka Naoko 
Published: November 2019

AbstractBlack carbon (BC) deposited on snow lowers its albedo, potentially contributing to warming in the Arctic. Atmospheric distributions of BC and inorganic aerosols, which contribute directly and indirectly to radiative forcing, are also greatly influenced by depositions. To quantify these effects, accurate measurement of the spatial distributions of BC and ionic species representative of inorganic aerosols (ionic species hereafter) in snowpack in various regions of the Arctic is needed, but few such measurements are available. We measured mass concentrations of size‐resolved BC (CMBC) and ionic species in snowpack by using a single‐particle soot photometer and ion chromatography, respectively, over Finland, Alaska, Siberia, Greenland, and Spitsbergen during early spring in 2012–2016. Total BC mass deposited per unit area (DEPMBC) during snow accumulation periods was derived from CMBC and snow water equivalent (SWE). Our analyses showed that the spatial distributions of anthropogenic BC emission flux, total precipitable water, and topography strongly influenced latitudinal variations of CMBC, BC size distributions, SWE, and DEPMBC. The average size distributions of BC in Arctic snowpack shifted to smaller sizes with decreasing CMBC due to an increase in the removal efficiency of larger BC particles during transport from major sources. Our measurements of CMBC were lower by a factor of ~13 than previous measurements made with an Integrating Sphere/Integrating Sandwich spectrophotometer due mainly to interference from coexisting non‐BC particles such as mineral dust. The SP2 data presented here will be useful for constraining climate models that estimate the effects of BC on the Arctic climate.
Seasonal Variations of Arctic Low‐Level Clouds and Its Linkage to Sea Ice Seasonal Variations
Authors: Yu Yueyue , Taylor Patrick C. , Cai Ming 
Published: November 2019

AbstractUsing CALIPSO‐CloudSat‐Clouds and the Earth's Radiant Energy System‐Moderate Resolution Imaging Spectrometer data set, this study documents the seasonal variation of sea ice, cloud, and atmospheric properties in the Arctic (70°N–82°N) for 2007–2010. A surface‐type stratification—consisting Permanent Ocean, Land, Permanent Ice, and Transient Sea Ice—is used to investigate the influence of surface type on low‐level Arctic cloud liquid water path (LWP) seasonality. The results show significant variations in the Arctic low‐level cloud LWP by surface type linked to differences in thermodynamic state. Subdividing the Transient Ice region (seasonal sea ice zone) by melt/freeze season onset dates reveals a complex influence of sea ice variations on low cloud LWP seasonality. We find that lower tropospheric stability is the primary factor affecting the seasonality of cloud LWP. Our results suggest that variations in sea ice melt/freeze onset have a significant influence on the seasonality of low‐level cloud LWP by modulating the lower tropospheric thermal structure and not by modifying the surface evaporation rate in late spring and midsummer. We find no significant dependence of the May low‐level cloud LWP peak on the melt/freeze onset dates, whereas and September/October low‐level cloud LWP maximum shifts later in the season for earlier melt/later freeze onset regions. The Arctic low cloud LWP seasonality is controlled by several surface‐atmosphere interaction processes; the importance of each varies seasonally due to the thermodynamic properties of sea ice. Our results demonstrate that when analyzing Arctic cloud‐sea ice interactions, a seasonal perspective is critical.
Regional Biases in MODIS Marine Liquid Water Cloud Drop Effective Radius Deduced Through Fusion With MISR
Authors: Fu Dongwei , Di Girolamo Larry , Liang Lusheng , Zhao Guangyu 
Published: November 2019

AbstractSatellite measurements from Terra's Moderate Resolution Imaging Spectroradiometer (MODIS) represent our longest, single‐platform, global record of the effective radius (Re) of the cloud drop size distribution. Quantifying its error characteristics has been challenging because systematic errors in retrieved Re covary with the structural characteristics of the cloud and the Sun‐view geometry. Recently, it has been shown that the bias in MODIS Re can be estimated by fusing MODIS data with data from Terra's Multi‐angle Imaging SpectroRadiometer (MISR). Here, we relate the bias to the observed underlying conditions to derive regional‐scale, bias‐corrected, monthly‐mean Re1.6, Re2.1, and Re3.7 values retrieved from the 1.6, 2.1, and 3.7 μm MODIS spectral channels. Our results reveal that monthly‐mean bias in Re2.1 exhibits large regional dependency, ranging from at least ~1 to 10 μm (15 to 60%) varying with scene heterogeneity, optical depth, and solar zenith angle. Regional bias‐corrected monthly‐mean Re2.1 ranges from 4 to 17 μm, compared to 10 to 25 μm for uncorrected Re2.1, with estimated uncertainties of 0.1 to 1.8 μm. The bias‐corrected monthly‐mean Re3.7 and Re2.1 show difference of approximately +0.6 μm in the coastal marine stratocumulus regions and down to approximately −2 μm in the cumuliform cloud regions, compared to uncorrected values of about −1 to −6 μm, respectively. Bias‐corrected Re values compare favorably to other independent data sources, including field observations, global model simulations, and satellite retrievals that do not use retrieval techniques similar to MODIS. This work changes the interpretation of global Re distributions from MODIS Re products and may further impact studies, which use the original MODIS Re products to study, for example, aerosol‐cloud interactions and cloud microphysical parameterization.
Response of Humic Acids and Soil Organic Matter to Vegetation Replacement in Subtropical High Mountain Forests
Authors: Wang Hsueh‐Ching , Tian Guanglong , Chen Chiou‐Pin , Chang Ed‐Haun , Chou Chiao‐Ying , Chiou Chyi‐Rong , Chiu Chih‐Yu 
Published: November 2019

AbstractReforestation can alter the chemical composition of soil organic matter (SOM) and humification; however, information on how specific plant types impact SOM lability and humification is not well documented. In this study, we used solid‐state 13C nuclear magnetic resonance spectroscopy, photometric analysis, and chemical fractionation to examine carbon (C) components and lability of SOM in a Japanese cedar (Cryptomeria japonica) forest and bamboo (Phyllostachys edulis) plantation that reforested a cutover primary broadleaf forest. The ∆logK value of soil humic acids, the inverse index of SOM humification, was lowest in the bamboo plantation, suggesting a higher SOM humification stage in the bamboo plantation. The soil labile C/Total C ratio was highest in the bamboo plantation, and this can be attributed to low aromaticity and alkyl‐C/O‐alkyl‐C ratio (A/O‐A) in the bamboo litter. Intensive cultivation of the bamboo plantation accelerated litter breakdown in the strongly acidic soil, resulting in the depletion of SOM. Cedar coniferous leaves, with their high recalcitrant substances and slow decomposition, only slightly lowered SOM humification due to the substantial broadleaf understory. Our results suggest that the type of plants involved in reforestation and understory reestablishment is critical to how SOM humification and lability change during the reforestation through the control of litter C components. Further research into the interaction between microclimate change and forest type in forest conversion will be useful for increasing understanding on the impact of forest conversion on SOM lability and humification in subtropical high mountain forest ecosystems.
Organic Carbon Origin, Benthic Faunal Consumption, and Burial in Sediments of Northern Atlantic and Arctic Fjords (60–81°N)
Authors: Włodarska‐Kowalczuk Maria , Mazurkiewicz Mikołaj , Górska Barbara , Michel Loïc N. , Jankowska Emilia , Zaborska Agata 
Published: November 2019

AbstractFjords have been recently recognized as hot spots of organic carbon (Corg) sequestration in marine sediments. This study aims to identify regional and local drivers of variability of Corg burial in north Atlantic and Arctic fjords. We provide a comparative quantification of Corg, δ13C, photosynthetic pigments content, benthic biomass, consumption, Corg accumulation, and burial rates in sediments in six fjords (60–81°N). Higher sediment Corg content in southern Norway reflected longer phytoplankton growth season and higher productivity. Higher contributions of terrestrial Corg were noted in temperate/southern Norway (dense land vegetation and high precipitation) and Arctic/Svalbard (glacial erosion) than in subarctic/northern Norway locations. Benthic biomass and carbon consumption were best correlated to δ13C and photosynthetic pigments content indicating control by quality rather than quantity of available food. Benthic faunal consumption did not seem to affect the variability in Corg burial. Regional environmental factors (water temperature and latitude) combined with local factors (Corg, grain size, and pigment concentration) explained 94% of Corg burial variability. Based on the present study and literature data on Corg content, origin, and burial rates, the fjords were classified into four categories: temperate, subarctic, Arctic with glaciers, and Arctic without glaciers. The variability in marine productivity, terrestrial inflows, and carbon sequestration in fjords must be considered for global estimates of their role in blue carbon storage and for building scenarios of future changes in the course of climate warming.
Microbial Processing of Sediment‐Derived Dissolved Organic Matter: Implications for Its Subsequent Biogeochemical Cycling in Overlying Seawater
Authors: Cai Ruanhong , Zhou Wenchu , He Chen , Tang Kai , Guo Weidong , Shi Quan , Gonsior Michael , Jiao Nianzhi 
Published: November 2019

AbstractCoastal sediments contain a large amount of dissolved organic matter (DOM), which can be mobilized into the overlying water by natural and anthropogenic activities. The bioavailability and subsequent biogeochemical effects of this sediment‐derived DOM are unclear. To investigate those, we collected a sediment pore‐water DOM (SDOM) sample and its overlying seawater to conduct a bioassay experiment, which allowed tracking of both short‐term and long‐term microbial processes in the context of DOM transformations. Short‐term incubation results show that the SDOM extract supported the growth of specific taxa. The microbial community composition changed dramatically and an approximately 50% of SDOM‐derived carbon was consumed within the first 2 days. Viruses likely played a role in promoting bacterial community succession, further enhancing transformation of this SDOM. Long‐term incubation results show that labile DOM was gradually consumed, while approximately 16% of the initial SDOM appeared to be recalcitrant to microbial utilization and remained at the end (after 110 days) of the incubation experiment. Despite the short‐term drastic changes in microbial community composition, a highly diverse microbial community is similar to the control at the end of the incubation. It is suggested here that resuspension of coastal sediments weakens their role as a net sink of carbon, with most of the mobilized SDOM transformed by successive microbial communities in the overlying seawater and the remaining recalcitrant organic material becoming part of the long‐lived DOM pool. Thus, the bioavailability of the coastal SDOM might influence the carbon budget in coastal oceans.
Contrasting Global Patterns of Spatially Periodic Fairy Circles and Regular Insect Nests in Drylands
Authors: Getzin Stephan , Yizhaq Hezi , Cramer Michael D. , Tschinkel Walter R. 
Published: November 2019

AbstractNumerical analysis of spatial pattern is widely used in ecology to describe the characteristics of floral and faunal distributions. These methods allow attribution of pattern to causal mechanisms by uncovering the specific signatures of patterns and causal agents. For example, grassland‐gap patterns called fairy circles (FCs) in Namibia and Australia are characterized by highly regular and homogenous distributions across landscapes that show spatially periodic ordering. These FCs have been suggested to be caused by both social insects and competitive plant interactions. We compared eight Namibian and Australian FC patterns and also modeled FCs to 16 patterns of social insect nests in Africa, Australia, and America that include the most regular termite mound patterns known. For pattern‐process inference, we used spatial statistics based on both nearest‐neighbor analysis and neighborhood‐density functions. None of the analyzed insect‐nest distributions attain the spatially periodic ordering that is typical of FCs. The inherently more variable patterns of termite and ant nests are commonly attributable to well documented aspects of the faunal life‐history. Our quantitative evidence from drylands shows that the more variable insect‐nest distributions in water‐limited environments cannot explain the characteristic spatial signature of FCs. The analysis demonstrates the interpretation of scale‐dependent neighborhood‐density functions and that it is the identification of unique spatial signatures in regular patterns that need to be linked to process. While our results cannot verify a specific hypothesis, they support the hypothesis that FCs in these drylands are more likely an emergent vegetation pattern caused by strong plant competition for water.
Scalable Flux Metrics at the Channel‐Floodplain Interface as Indicators of Lateral Surface Connectivity During Flood Events
Authors: Byrne C. F. , Stone M. C. , Morrison R. R. 
Published: November 2019

AbstractLateral surface connectivity (LSC), defined here as the surficial component of hydrologic exchange flows perpendicular to longitudinal flow, is vital to biogeochemical, geomorphological, and ecological processes on floodplains. Because rivers throughout much of the world have been subjected to anthropogenic manipulation, LSC has been greatly altered. While qualitative descriptions of LSC exist, only a limited number of studies quantify this process. The objective of this study was to quantify mass and momentum flux as proxies for LSC. This objective was met through the analysis of hydrodynamic model outputs along a 10‐km reach of the Middle Rio Grande near Albuquerque, New Mexico, USA. Mass and momentum fluxes were quantified for two synthetic floods across three spatial scales: geomorphic sub‐units, units, and reaches. In addition, three floodplain surface elevations were defined: inset, restored, and historical. Mass and momentum fluxes displayed distinct hydrodynamic signatures at each floodplain surface elevation. Inset floodplains were subjected to the greatest and most widely distributed flux magnitudes, an indication of the anthropogenic alteration along the reach. Flux heterogeneity on inset surfaces was also greatest, and increased flood magnitude did not result in comparable heterogeneity at higher floodplain elevations. Unsteady results showed that peak flux magnitudes can occur on the rising and falling limbs of a flood hydrograph, providing evidence of hysteresis in channel‐floodplain connections. Ultimately, the results are indicative of complexities associated with LSC processes along geomorphologically altered channel‐floodplain systems. The scalable methods are applicable to a wide variety of river‐floodplain systems and are complementary to empirical flux measurements.
Illusory sound texture reveals multi-second statistical completion in auditory scene analysis
Authors: McWalter Richard , McDermott Josh H. 
Published: November 2019

AbstractSound sources in the world are experienced as stable even when intermittently obscured, implying perceptual completion mechanisms that “fill in” missing sensory information. We demonstrate a filling-in phenomenon in which the brain extrapolates the statistics of background sounds (textures) over periods of several seconds when they are interrupted by another sound, producing vivid percepts of illusory texture. The effect differs from previously described completion effects in that 1) the extrapolated sound must be defined statistically given the stochastic nature of texture, and 2) the effect lasts much longer, enabling introspection and facilitating assessment of the underlying representation. Illusory texture biases subsequent texture statistic estimates indistinguishably from actual texture, suggesting that it is represented similarly to actual texture. The illusion appears to represent an inference about whether the background is likely to continue during concurrent sounds, providing a stable statistical representation of the ongoing environment despite unstable sensory evidence.
Nature of excitations and defects in structural glasses
Authors: Scalliet Camille , Berthier Ludovic , Zamponi Francesco 
Published: November 2019

AbstractThe nature of defects in amorphous materials, analogous to vacancies and dislocations in crystals, remains elusive. Here, we explore their nature in a three-dimensional microscopic model glass-former that describes granular, colloidal, atomic and molecular glasses by changing the temperature and density. We find that all glasses evolve in a very rough energy landscape, with a hierarchy of barrier sizes corresponding to both localized and delocalized excitations. Collective excitations dominate in the jamming regime relevant for granular and colloidal glasses. By moving gradually to larger densities describing atomic and molecular glasses, the system crosses over to a regime dominated by localized defects and relatively simpler landscapes. We quantify the energy and temperature scales associated to these defects and their evolution with density. Our results pave the way to a systematic study of low-temperature physics in a broad range of physical conditions and glassy materials.
Control of the temporal and polarization response of a multimode fiber
Authors: Mounaix Mickael , Carpenter Joel 
Published: November 2019

AbstractControl of the spatial and temporal properties of light propagating in disordered media have been demonstrated over the last decade using spatial light modulators. Most of the previous studies demonstrated spatial focusing to the speckle grain size, and manipulation of the temporal properties of the achieved focus. In this work, we demonstrate an approach to control the total temporal impulse response, not only at a single speckle grain but over all spatial degrees of freedom (spatial and polarization modes) at any arbitrary delay time through a multimode fiber. Global enhancement or suppression of the total light intensity exiting a multimode fibre is shown for arbitrary delays and polarization states. This work could benefit to applications that require pulse delivery in disordered media.
From small-scale forest structure to Amazon-wide carbon estimates
Authors: Rödig Edna , Knapp Nikolai , Fischer Rico , Bohn Friedrich J. , Dubayah Ralph , Tang Hao , Huth Andreas 
Published: November 2019

AbstractTropical forests play an important role in the global carbon cycle. High-resolution remote sensing techniques, e.g., spaceborne lidar, can measure complex tropical forest structures, but it remains a challenge how to interpret such information for the assessment of forest biomass and productivity. Here, we develop an approach to estimate basal area, aboveground biomass and productivity within Amazonia by matching 770,000 GLAS lidar (ICESat) profiles with forest simulations considering spatial heterogeneous environmental and ecological conditions. This allows for deriving frequency distributions of key forest attributes for the entire Amazon. This detailed interpretation of remote sensing data improves estimates of forest attributes by 20–43% as compared to (conventional) estimates using mean canopy height. The inclusion of forest modeling has a high potential to close a missing link between remote sensing measurements and the 3D structure of forests, and may thereby improve continent-wide estimates of biomass and productivity.
WUSCHEL acts as an auxin response rheostat to maintain apical stem cells in Arabidopsis
Authors: Ma Yanfei , Miotk Andrej , Šutiković Zoran , Ermakova Olga , Wenzl Christian , Medzihradszky Anna , Gaillochet Christophe , Forner Joachim , Utan Gözde , Brackmann Klaus , Galván-Ampudia Carlos S. , Vernoux Teva , Greb Thomas , Lohmann Jan U. 
Published: November 2019

AbstractTo maintain the balance between long-term stem cell self-renewal and differentiation, dynamic signals need to be translated into spatially precise and temporally stable gene expression states. In the apical plant stem cell system, local accumulation of the small, highly mobile phytohormone auxin triggers differentiation while at the same time, pluripotent stem cells are maintained throughout the entire life-cycle. We find that stem cells are resistant to auxin mediated differentiation, but require low levels of signaling for their maintenance. We demonstrate that the WUSCHEL transcription factor confers this behavior by rheostatically controlling the auxin signaling and response pathway. Finally, we show that WUSCHEL acts via regulation of histone acetylation at target loci, including those with functions in the auxin pathway. Our results reveal an important mechanism that allows cells to differentially translate a potent and highly dynamic developmental signal into stable cell behavior with high spatial precision and temporal robustness.