Browsing by Subject "SPATIAL-DISTRIBUTION"

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  • Voothuluru, Priya; Mäkelä, Pirjo; Zhu, Jinming; Yamaguchi, Mineo; Oliver, Melvin J.; Simmonds, John; Sharp, Robert (2020)
    Reactive oxygen species (ROS) can act as signaling molecules involved in the acclimation of plants to various abiotic and biotic stresses. However, it is not clear how the generalized increases in ROS and downstream signaling events that occur in response to stressful conditions are coordinated to modify plant growth and development. Previous studies of maize (Zea mays L.) primary root growth under water deficit stress showed that cell elongation is maintained in the apical region of the growth zone but progressively inhibited further from the apex, and that the rate of cell production is also decreased. It was observed that apoplastic ROS, particularly hydrogen peroxide (H2O2), increased specifically in the apical region of the growth zone under water stress, resulting at least partly from increased oxalate oxidase activity in this region. To assess the function of the increase in apoplastic H2O2 in root growth regulation, transgenic maize lines constitutively expressing a wheat oxalate oxidase were utilized in combination with kinematic growth analysis to examine effects of increased apoplastic H2O2 on the spatial pattern of cell elongation and on cell production in well-watered and water-stressed roots. Effects of H2O2 removal (via scavenger pretreatment) specifically from the apical region of the growth zone were also assessed. The results show that apoplastic H2O2 positively modulates cell production and root elongation under well-watered conditions, whereas the normal increase in apoplastic H2O2 in water-stressed roots is causally related to down-regulation of cell production and root growth inhibition. The effects on cell production were accompanied by changes in spatial profiles of cell elongation and in the length of the growth zone. However, effects on overall cell elongation, as reflected in final cell lengths, were minor. These results reveal a fundamental role of apoplastic H2O2 in regulating cell production and root elongation in both well-watered and water-stressed conditions.
  • Turc, Lucile; Taryus, Vertti; Dimmock, Andrew P.; Battarbee, Markus; Ganse, Urs; Johlander, Andreas; Grandin, Maxime; Pfau-Kempf, Yann; Dubart, Maxime; Palmroth, Minna (2020)
    Bounded by the bow shock and the magnetopause, the magnetosheath forms the interface between solar wind and magnetospheric plasmas and regulates solar wind-magnetosphere coupling. Previous works have revealed pronounced dawn-dusk asymmetries in the magnetosheath properties. The dependence of these asymmetries on the upstream parameters remains however largely unknown. One of the main sources of these asymmetries is the bow shock configuration, which is typically quasi-parallel on the dawn side and quasi-perpendicular on the dusk side of the terrestrial magnetosheath because of the Parker spiral orientation of the interplanetary magnetic field (IMF) at Earth. Most of these previous studies rely on collections of spacecraft measurements associated with a wide range of upstream conditions which are processed in order to obtain average values of the magnetosheath parameters. In this work, we use a different approach and quantify the magnetosheath asymmetries in global hybrid-Vlasov simulations performed with the Vlasiator model. We concentrate on three parameters: the magnetic field strength, the plasma density, and the flow velocity. We find that the Vlasiator model reproduces the polarity of the asymmetries accurately but that their level tends to be higher than in spacecraft measurements, probably because the magnetosheath parameters are obtained from a single set of upstream conditions in the simulation, making the asymmetries more prominent. A set of three runs with different upstream conditions allows us to investigate for the first time how the asymmetries change when the angle between the IMF and the Sun-Earth line is reduced and when the Alfven Mach number decreases. We find that a more radial IMF results in a stronger magnetic field asymmetry and a larger variability of the magnetosheath density. In contrast, a lower Alfven Mach number leads to a reduced magnetic field asymmetry and a decrease in the variability of the magnetosheath density, the latter likely due to weaker foreshock processes. Our results highlight the strong impact of the quasi-parallel shock and its associated foreshock on global magnetosheath properties, in particular on the magnetosheath density, which is extremely sensitive to transient quasi-parallel shock processes, even with the perfectly steady upstream conditions in our simulations. This could explain the large variability of the density asymmetry levels obtained from spacecraft measurements in previous studies.
  • Zhou, Chenlin; Vastel, Charlotte; Montillaud, Julien; Ceccarelli, Cecilia; Demyk, Karine; Harju, Jorma; Juvela, Mika; Ristorcelli, Isabelle; Liu, Tie (2022)
    Context. A solar-type system starts from an initial molecular core that acquires organic complexity as it evolves. The so-called prestellar cores that can be studied are rare, which has hampered our understanding of how organic chemistry sets in and grows. Aims. We selected the best prestellar core targets from the cold core catalogue (based on Planck and Herschel observations) that represent a diversity in terms of their environment to explore their chemical complexity: 1390 (in the compressed shell of Lambda Ori), 869 (in the MBM12 cloud), and 4149 (in the California nebula). Methods. We obtained a spectral survey with the IRAM 30 m telescope in order to explore the molecular complexity of the cores. We carried out a radiative transfer analysis of the detected transitions in order to place some constraints on the physical conditions of the cores and on the molecular column densities. We also used the molecular ions in the survey to estimate the cosmic-ray ionisation rate and the S/H initial elemental abundance using a gas-phase chemical model to reproduce their abundances. Results. We found large differences in the molecular complexity (deuteration, complex organic molecules, sulphur, carbon chains, and ions) and compared their chemical properties with a cold core and two prestellar cores. The chemical diversity we found in the three cores seems to be correlated with their chemical evolution: two of them are prestellar (1390 and 4149), and one is in an earlier stage (869). Conclusions. The influence of the environment is likely limited because cold cores are strongly shielded from their surroundings. The high extinction prevents interstellar UV radiation from penetrating deeply into the cores. Higher spatial resolution observations of the cores are therefore needed to constrain the physical structure of the cores, as well as a larger-scale distribution of molecular ions to understand the influence of the environment on their molecular complexity.
  • Yan, Lijuan; Yu, Dan; Hui, Nan; Naanuri, Eve; Viggor, Signe; Gafarov, Arslan; Sokolov, Sergei L; Heinaru, Ain; Romantschuk, Martin L. (2018)
    The Baltic Sea is vulnerable to environmental changes. With the increasing shipping activities, the risk of oil spills remains high. Archaea are widely distributed in many environments. However, the distribution and the response of archaeal communities to oil contamination have rarely been investigated in brackish habitats. Hence, we conducted a survey to investigate the distribution, diversity, composition, and species interactions of indigenous archaeal communities at oil-contaminated sites along the coast of the Gulf of Finland (GoF) using high-throughput sequencing. Surface water and littoral sediment samples were collected at presumably oil-contaminated (oil distribution facilities) and clean sites along the coastline of the GoF in the winter 2015 and the summer 2016. Another three samples of open sea surface water were taken as offshore references. Of Archaea, Euryarchaeota dominated in the surface water and the littoral sediment of the coast of the GoF, followed by Crenarchaeota (including Thaumarchaeota, Thermoprotei, and Korarchaeota based on the Greengenes database used). The unclassified sequences accounted for 5.62% of the total archaeal sequences. Our study revealed a strong dependence of the archaeal community composition on environmental variables (e.g., salinity, pH, oil concentration, TOM, electrical conductivity, and total DNA concentration) in both littoral sediment and coastal water in the GoF. The composition of archaeal communities was season and ecosystem dependent. Archaea was highly diverse in the three ecosystems (littoral sediment, coastal water, and open sea water). Littoral sediment harbored the highest diversity of archaea. Oil was often detected in the littoral sediment but rarely detected in water at those presumably contaminated sites. Although the composition of archaeal community in the littoral sediment was sensitive to low-input oil contamination, the unchanged putative functional profiles and increased interconnectivity of the archaeal core species network plausibly revealed resilience and the potential for oil degradation. Halobacteriaceae and putative cytochrome P450 pathways were significantly enriched in the oil-contaminated littoral sediment.The archaeal taxa formed highly interconnected and interactive networks, in which Halobacteriaceae, Thermococcus, and methanogens were the main components, implying a potential relevant trophic connection between hydrocarbon degradation, methanogenesis, sulfate reduction, and/or fermentative growth.
  • Kotta, Jonne; Vanhatalo, Jarno Petteri; Jänes, Holger; Orav-Kotta, Helen; Rugiu, Luca; Jormalainen, Veijo; Bobsien, Ivo; Viitasalo, Markku; Virtanen, Elina; Nyström Sandman, Antonia; Isaeus, Martin; Leidenberger, Sonja; Jonsson, Per R.; Johannesson, Kerstin (2019)
    Predictive species distribution models are mostly based on statistical dependence between environmental and distributional data and therefore may fail to account for physiological limits and biological interactions that are fundamental when modelling species distributions under future climate conditions. Here, we developed a state-of-the-art method integrating biological theory with survey and experimental data in a way that allows us to explicitly model both physical tolerance limits of species and inherent natural variability in regional conditions and thereby improve the reliability of species distribution predictions under future climate conditions. By using a macroalga-herbivore association (Fucus vesiculosus - Idotea balthica) as a case study, we illustrated how salinity reduction and temperature increase under future climate conditions may significantly reduce the occurrence and biomass of these important coastal species. Moreover, we showed that the reduction of herbivore occurrence is linked to reduction of their host macroalgae. Spatial predictive modelling and experimental biology have been traditionally seen as separate fields but stronger interlinkages between these disciplines can improve species distribution projections under climate change. Experiments enable qualitative prior knowledge to be defined and identify cause-effect relationships, and thereby better foresee alterations in ecosystem structure and functioning under future climate conditions that are not necessarily seen in projections based on non-causal statistical relationships alone.
  • Milillo, A.; Fujimoto, M.; Murakami, G.; Benkhoff, J.; Zender, J.; Aizawa, S.; Dosa, M.; Griton, L.; Heyner, D.; Ho, G.; Imber, S. M.; Jia, Yan; Karlsson, T.; Killen, R. M.; Laurenza, M.; Lindsay, S. T.; McKenna-Lawlor, S.; Mura, A.; Raines, J. M.; Rothery, D. A.; Andre, N.; Baumjohann, W.; Berezhnoy, A.; Bourdin, P. A.; Bunce, E. J.; Califano, F.; Deca, J.; de la Fuente, S.; Dong, C.; Grava, C.; Fatemi, S.; Henri, P.; Ivanovski, S. L.; Jackson, B. V.; James, M.; Kallio, E.; Kasaba, Y.; Kilpua, E.; Kobayashi, M.; Langlais, B.; Leblanc, F.; Lhotka, C.; Mangano, V.; Martindale, A.; Massetti, S.; Masters, A.; Morooka, M.; Narita, Y.; Oliveira, J. S.; Odstrcil, D.; Orsini, S.; Pelizzo, M. G.; Plainaki, C.; Plaschke, F.; Sahraoui, Afaf; Seki, K.; Slavin, J. A.; Vainio, R.; Wurz, P.; Barabash, S.; Carr, C. M.; Delcourt, D.; Glassmeier, K. -H.; Grande, M.; Hirahara, M.; Huovelin, J.; Korablev, O.; Kojima, H.; Lichtenegger, H.; Livi, S.; Matsuoka, A.; Moissl, R.; Moncuquet, M.; Muinonen, K.; Quemerais, E.; Saito, Y.; Yagitani, S.; Yoshikawa, I.; Wahlund, J. -E. (2020)
    The ESA-JAXA BepiColombo mission will provide simultaneous measurements from two spacecraft, offering an unprecedented opportunity to investigate magnetospheric and exospheric dynamics at Mercury as well as their interactions with the solar wind, radiation, and interplanetary dust. Many scientific instruments onboard the two spacecraft will be completely, or partially devoted to study the near-space environment of Mercury as well as the complex processes that govern it. Many issues remain unsolved even after the MESSENGER mission that ended in 2015. The specific orbits of the two spacecraft, MPO and Mio, and the comprehensive scientific payload allow a wider range of scientific questions to be addressed than those that could be achieved by the individual instruments acting alone, or by previous missions. These joint observations are of key importance because many phenomena in Mercury's environment are highly temporally and spatially variable. Examples of possible coordinated observations are described in this article, analysing the required geometrical conditions, pointing, resolutions and operation timing of different BepiColombo instruments sensors.
  • Schulz, Torsti; Vanhatalo, Jarno; Saastamoinen, Marjo (2019)
    Species distribution models are the tool of choice for large-scale population monitoring, environmental association studies and predictions of range shifts under future environmental conditions. Available data and familiarity of the tools rather than the underlying population dynamics often dictate the choice of specific method - especially for the case of presence-absence data. Yet, for predictive purposes, the relationship between occupancy and abundance embodied in the models should reflect the actual population dynamics of the modelled species. To understand the relationship of occupancy and abundance in a heterogeneous landscape at the scale of local populations, we built a spatio-temporal regression model of populations of the Glanville fritillary butterfly Melitaea cinxia in a Baltic Sea archipelago. Our data comprised nineteen years of habitat surveys and snapshot data of land use in the region. We used variance partitioning to quantify relative contributions of land use, habitat quality and metapopulation covariates. The model revealed a consistent and positive, but noisy relationship between average occupancy and mean abundance in local populations. Patterns of abundance were highly variable across years, with large uncorrelated random variation and strong local population stochasticity. In contrast, the spatio-temporal random effect, habitat quality, population connectivity and patch size explained variation in occupancy, vindicating metapopulation theory as the basis for modelling occupancy patterns in fragmented landscapes. Previous abundance was an important predictor in the occupancy model, which points to a spillover of abundance into occupancy dynamics. While occupancy models can successfully model large-scale population structure and average occupancy, extinction probability estimates for local populations derived from occupancy-only models are overconfident, as extinction risk is dependent on actual, not average, abundance.
  • Phillips, N. W.; Yu, H.; Das, S.; Yang, D.; Mizohata, K.; Liu, W.; Xu, R.; Harder, R. J.; Hofmann, F. (2020)
    Developing a comprehensive understanding of the modification of material properties by neutron irradiation is important for the design of future fission and fusion power reactors. Self-ion implantation is commonly used to mimic neutron irradiation damage, however an interesting question concerns the effect of ion energy on the resulting damage structures. The reduction in the thickness of the implanted layer as the implantation energy is reduced results in the significant quandary: Does one attempt to match the primary knock-on atom energy produced during neutron irradiation or implant at a much higher energy, such that a thicker damage layer is produced? Here we address this question by measuring the full strain tensor for two ion implantation energies, 2 MeV and 20 MeV in self-ion implanted tungsten, a critical material for the first wall and divertor of fusion reactors. A comparison of 2 MeV and 20 MeV implanted samples is shown to result in similar lattice swelling. Multi-reflection Bragg coherent diffractive imaging (MBCDI) shows that implantation induced strain is in fact heterogeneous at the nanoscale, suggesting that there is a non-uniform distribution of defects, an observation that is not fully captured by micro-beam Laue diffraction. At the surface, MBCDI and high-resolution electron back-scattered diffraction (HR-EBSD) strain measurements agree quite well in terms of this clustering/non-uniformity of the strain distribution. However, MBCDI reveals that the heterogeneity at greater depths in the sample is much larger than at the surface. This combination of techniques provides a powerful method for detailed investigation of the microstructural damage caused by ion bombardment, and more generally of strain related phenomena in micro-volumes that are inaccessible via any other technique. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
  • Murakami, Mariana; Nunes Ramos, Flavio; Durand, Maxime; Ashton, Robert; Batke, Sven P. (2022)
    Forest canopies are incredibly complex self-maintaining biological structures. Conditions above and within the canopy can differ vastly, often resulting in a vertical gradient of microclimate conditions. Canopy epiphytic plants have to deal with climatic variability on much more variable scales compared to many other plant groups. The difficulty of sensor installation and their high cost can explain why it has been ignored in many studies on canopy epiphytes. Direct measurements of microenvironmental conditions are the only accurate way to assess specific intra-canopy environmental conditions, as there is also still a lack of methodologically and financially viable alternatives to allow the collection of this type of data. This study aims to make recommendations for the direct use of microclimate measurements in epiphyte research and to summarize key discussion points concerning the number and placement of sensors required for different types of epiphyte studies. In addition, we presented high-resolution field data from the United Kingdom, where we employed over 56 microclimate sensors, to demonstrate the spatial and temporal variability of radiation, temperature, and relative humidity (RH) in a tree canopy. Our data demonstrated that sensor height in the tree and leaf-set were the most important factors determining microclimate variability in the canopy. For the first time, we have made recommendations regarding the placement and number of sensors required in studies that specifically require the use of microclimate sensors in epiphyte studies in forest canopies.
  • Jenny, Jean-Philippe; Anneville, Orlane; Arnaud, Fabien; Baulaz, Yoann; Bouffard, Damien; Domaizon, Isabelle; Bocaniov, Serghei A.; Chevre, Nathalie; Dittrich, Maria; Dorioz, Jean-Marcel; Dunlop, Erin S.; Dur, Gael; Guillard, Jean; Guinaldo, Thibault; Jacquet, Stephan; Jamoneau, Aurelien; Jawed, Zobia; Jeppesen, Erik; Krantzberg, Gail; Lenters, John; Leoni, Barbara; Meybeck, Michel; Nava, Veronica; Noges, Tiina; Noges, Peeter; Patelli, Martina; Pebbles, Victoria; Perga, Marie-Elodie; Rasconi, Serena; Ruetz, Carl R.; Rudstam, Lars; Salmaso, Nico; Sapna, Sharma; Straile, Dietmar; Tammeorg, Olga; Twiss, Michael R.; Uzarski, Donald G.; Ventela, Anne-Mari; Vincent, Warwick F.; Wilhelm, Steven W.; Wangberg, Sten-Ake; Weyhenmeyer, Gesa A. (2020)
    Large lakes of the world are habitats for diverse species, including endemic taxa, and are valuable resources that provide humanity with many ecosystem services. They are also sentinels of global and local change, and recent studies in limnology and paleolimnology have demonstrated disturbing evidence of their collective degradation in terms of depletion of resources (water and food), rapid warming and loss of ice, destruction of habitats and ecosystems, loss of species, and accelerating pollution. Large lakes are particularly exposed to anthropogenic and climatic stressors. The Second Warning to Humanity provides a framework to assess the dangers now threatening the world's large lake ecosystems and to evaluate pathways of sustainable development that are more respectful of their ongoing provision of services. Here we review current and emerging threats to the large lakes of the world, including iconic examples of lake management failures and successes, from which we identify priorities and approaches for future conservation efforts. The review underscores the extent of lake resource degradation, which is a result of cumulative perturbation through time by long-term human impacts combined with other emerging stressors. Decades of degradation of large lakes have resulted in major challenges for restoration and management and a legacy of ecological and economic costs for future generations. Large lakes will require more intense conservation efforts in a warmer, increasingly populated world to achieve sustainable, high-quality waters. This Warning to Humanity is also an opportunity to highlight the value of a long-term lake observatory network to monitor and report on environmental changes in large lake ecosystems. (C) 2020 The Authors. Published by Elsevier B.V. on behalf of International Association for Great Lakes Research.
  • Starkenburg, Else; Oman, Kyle A.; Navarro, Julio F.; Crain, Robert A.; Fattahi, Azadeh; Frenk, Carlos S.; Sawala, Till; Schaye, Joop (2017)
    We examine the spatial distribution of the oldest and most metal-poor stellar populations of Milky Way-sized galaxies using the A Project Of Simulating The Local Environment (APOSTLE) cosmological hydrodynamical simulations of the Local Group. In agreement with earlier work, we find strong radial gradients in the fraction of the oldest (t(form) <0.8 Gyr) and most metal-poor ([Fe/H] <-2.5) stars, both of which increase outwards. The most metal-poor stars form over an extended period of time; half of them form after z = 5.3, and the last 10 per cent after z = 2.8. The age of the metal-poor stellar population also shows significant variation with environment; a high fraction of them are old in the galaxy's central regions and an even higher fraction in some individual dwarf galaxies, with substantial scatter from dwarf to dwarf. We investigate the dependence of these results on the assumptions made for metal mixing. Overall, over half of the stars that belong to both the oldest and most metal-poor population are found outside the solar circle. Somewhat counter-intuitively, we find that dwarf galaxies with a large fraction of metal-poor stars that are very old are systems where metal-poor stars are relatively rare, but where a substantial old population is present. Our results provide guidance for interpreting the results of surveys designed to hunt for the earliest and most pristine stellar component of our Milky Way.
  • Kärssin, Age; Häkkinen, Liidia; Niin, Enel; Peik, Katrin; Vilem, Annika; Jokelainen, Pikka; Lassen, Brian (2017)
    Background: Raccoon dogs and red foxes are well-adapted hosts for Trichinella spp. The aims of this study were to estimate Trichinella infection prevalence and biomass and to investigate which Trichinella species circulated in these indicator hosts in Estonia. Methods: From material collected for evaluating the effectiveness of oral vaccination program for rabies eradication in wildlife, samples from 113 raccoon dogs and 87 red foxes were included in this study. From each animal, 20 g of masseter muscle tissue was tested for the presence of Trichinella larvae using an artificial digestion method. The Trichinella larvae were identified to species level by multiplex polymerase chain reaction method. Results: The majority of tested animals were infected with Trichinella spp. The parasite species identified were T. nativa and T. britovi. The apparent infection prevalence was 57.5% in raccoon dogs and 69.0% in red foxes, which were higher than previous estimates. In addition, the larval burden had also increased in both hosts. We estimated that in 2011-2012, the Trichinella spp. biomass was more than 15 times higher in raccoon dogs and almost two times higher in red foxes than in 1992-2000 (based on mean larval burden), and almost 20 times higher in raccoon dogs and almost five times higher in red foxes than in 2000-2002 (based on median larval burden). Conclusions: Raccoon dogs and red foxes are relevant reservoirs for Trichinella spp. in Estonia. The biomass of Trichinella circulating in sylvatic cycles was substantial and had increased: there is substantial infection pressure in the sylvatic cycle.
  • Rusak, J. A.; Tanentzap, A. J.; Klug, J. L.; Rose, K. C.; Hendricks, S. P.; Jennings, E.; Laas, A.; Pierson, D.; Ryder, E.; Smyth, R. L.; White, D. S.; Winslow, L. A.; Adrian, R.; Arvola, L.; de Eyto, E.; Feuchtmayr, H.; Honti, M.; Istvanovics, V.; Jones, I. D.; McBride, C. G.; Schmidt, S. R.; Seekell, D.; Staehr, P. A.; Zhu, G. (2018)
    Phytoplankton biomass and production regulates key aspects of freshwater ecosystems yet its variability and subsequent predictability is poorly understood. We estimated within-lake variation in biomass using high-frequency chlorophyll fluorescence data from 18 globally distributed lakes. We tested how variation in fluorescence at monthly, daily, and hourly scales was related to high-frequency variability of wind, water temperature, and radiation within lakes as well as productivity and physical attributes among lakes. Within lakes, monthly variation dominated, but combined daily and hourly variation were equivalent to that expressed monthly. Among lakes, biomass variability increased with trophic status while, within-lake biomass variation increased with increasing variability in wind speed. Our results highlight the benefits of high-frequency chlorophyll monitoring and suggest that predicted changes associated with climate, as well as ongoing cultural eutrophication, are likely to substantially increase the temporal variability of algal biomass and thus the predictability of the services it provides.