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Sample records for acidic tundra mat

  1. Amino acid composition of humic substances in tundra soils

    NASA Astrophysics Data System (ADS)

    Vasilevich, R. S.; Beznosikov, V. A.

    2015-06-01

    Peripheral amino acid fragments of humic and fulvic acid molecules from tundra soils have been identified and quantified. A significant weight fraction of amino acids has been found in humic acid preparations, which exceeds their content in fulvic acids. Features of the amino acid composition of humic substances along the soil profile and depending on the degree of hydromorphism and the proportions of different (neutral, basic, acidic, cyclic) groups in amino acids have been revealed. The molar ratio between the hydroxy and heterocyclic amino acids reflects the degree of humification of the soil.

  2. Complexation of mercury(II) ions with humic acids in tundra soils

    NASA Astrophysics Data System (ADS)

    Vasilevich, R. S.; Beznosikov, V. A.; Lodygin, E. D.; Kondratenok, B. M.

    2014-03-01

    The interaction mechanisms of mercury(II) ions with preparations of humic acids (HAs) isolated from organic horizons of surface-gleyed soils (Haplic Stagnosol (Gelic, Siltic)) of shrub tundra and hydromorphic peat gley soils (Histic Cryosol (Reductaquic, Siltic)) of moss-lichen tundra have been studied. The particular features of the interactions between the mercury(II) ions and the HAs are related to the molecular structure of the HAs, the mercury concentration range, and the environmental parameters. The fixation of mercury(II) ions into stable coordination compounds is most efficient in the pH range of 2.5-3.5. At the element concentrations below 0.50 μmol/dm3, the main complexing sites of HAs are their peripheral aminoacid functional groups. Pyrocatechol, salicylate, and phenolic groups from the nuclear moiety of molecules interact in the concentration range of 0.0005-0.50 mmol/dm3; the physical sorption of mercury hydroxo complexes by the surface of HAs is the main process occurring in the system.

  3. Correlations between different acidity forms in amorphous loamy soils of the tundra and taiga zones

    NASA Astrophysics Data System (ADS)

    Shamrikova, E. V.; Sokolova, T. A.

    2013-05-01

    Pair correlation coefficients ( r) between the acidity parameters for the main genetic horizons of soddy-podzolic soils (SPSs), typical podzolic soils (TPSs), gley-podzolic soils (GPSs), and tundra surfacegley soils (TSGSs) have been calculated on the basis of a previously developed database. A significant direct linear correlation has been revealed between the pHwater and pHKCl values in the organic and eluvial horizons of each soil, but the degree of correlation decreased when going from the less acidic SPSs to the more acidic soils of other taxons. This could be related to the fact that, under strongly acid conditions, extra Al3+ was dissolved in the KCl solutions from complex compounds in the organic horizons and from Al hydroxide interlayers in the soil chlorites. No significant linear correlation has been found between the exchangeable acidity ( H exch) and the activity of the [H]+ ions in the KCl extract ( a(H+)KCl) calculated per unit of mass in the organic horizons of the SPSs, but it has been revealed in the organic horizons of the other soils because of the presence of the strongest organic acids in their KCl extracts. The high r values between the H exch and a(H+)KCl in all the soils of the taiga zones have been related to the common source and composition of the acidic components. The correlation between the exchangeable and total ( H tot) acidities in the organic horizons of the podzolic soils has been characterized by high r values because of the common source of the acidity: H+ and probably Al3+ ions located on the functional groups of organic acids. High r values between the H exch and a(H+)KCl have been observed in the mineral horizons of all the soils, because the Al3+ hydroxo complexes occurring on the surface and in the interlayer spaces of the clay minerals were sources of both acidity forms.

  4. Using Discriminant Analysis to Examine Spectral Differences Among Four Tundra Vegetation Communities at Ivotuk, Alaska

    NASA Astrophysics Data System (ADS)

    Bratsch, S.; Epstein, H. E.

    2014-12-01

    Warming in the Arctic has resulted in changes in the distribution and composition of tundra vegetation in addition to a lengthening of the growing season. Past studies have mapped tundra vegetation at relatively coarse spatial scales; however, vegetation changes in the Arctic are occurring at spatial scales within a few meters. This research uses hyperspectral remote sensing data to differentiate among four vegetation communities at Ivotuk, Alaska (68.49°N, 155.74°W). Ivotuk is located on the North Slope, and is dominated by four plant communities including moist acidic tundra (MAT), moist nonacidic tundra (MNT), mossy tussock tundra (MT), and shrub tundra (ST). Hand-held hyperspectral data were collected during the 1999 growing season (5 June-27 August) at biweekly intervals using narrow, ~1.42 nm wavebands. Only wavebands within 400-1060 nm were used in analysis. Two sets of comparisons were conducted using stepwise discriminant analysis: 1) MNT and ST, and 2) all four tundra plant communities. MNT and ST classification accuracy ranged from 91.3-100%, with 100% classification and cross-validated accuracy occurring on 27 July. Classification accuracy for the overall growing season was 97.9% for MNT and 98.1% for ST. The stepwise function indicated 18 significant bands including 8 near infrared (NIR) and 4 blue bands. MAT, MNT, MT, and ST classification accuracy ranged from 58-100%, with greatest classification accuracy (100%) also occurring during peak growing season on 27 July. Overall classification accuracy for the growing season was 97.6% for MNT, 92% for MT, 84% for ST, and 70.8% for MAT. There were 14 significant bands including 6 NIR and 3 blue bands. The results presented here demonstrate that discriminant analysis can be useful in distinguishing among the dominant tundra vegetation communities in the Arctic, and can potentially help us to better understand and monitor arctic vegetation and ecosystem responses to environmental changes.

  5. Availability of elements in tundra soils on acidic and ultramafic rocks in the Polar Urals

    NASA Astrophysics Data System (ADS)

    Kataeva, M. N.

    2013-02-01

    The chemical properties of soils and their particle-size distribution in ecotopes of the Polar Urals mountain tundra were considered in relation with the lithological and geochemical features of the parent rocks. In the soils of ecotopes on the ultramafic massif, the contents of the total Ni (2830 mg/kg) and the total Cr (2327 mg/kg) were found to exceed their clarke values, which suggested the accumulation of these elements by plants and their migration with water. In the soils of the ultramafic massif, the average content of mobile Ni was 46.8 mg/kg, which exceeded the Ni MPC by 11.7 times. The average concentration of mobile Cr in the soils of the massif made up 0.35 MPC. In the soils of geochemical acidic rocks, the contents of mobile Ni and Cr were lower than their MPC levels. A higher content of particles with an average diameter ≥5 μm was found in the soils of the ultramafic massif.

  6. Complexation of Hg (II) ions with humic acids of tundra soils

    NASA Astrophysics Data System (ADS)

    Vasilevich, Roman

    2013-04-01

    Humic acids (HA) play an important role in processes of heavy metals migration, controlling their geochemical streams in environment. Accumulative and detoxification abilities of HA to heavy metals are realized by means of formation of steady complexes salycylate and pyrocatechin types. Modern researches show that HA of the Arctic and Subarctic areas are poorly enriched by aromatic frames, so and metalbinding centres. The work purpose is to study interaction mechanisms of Hg (II) ions with HA and to define tread possibilities of a tundra soils humic acids. It is established that binding ability of Hg (II) ions depends on concentration of an element, on quantity of functional groups in peripheral and nuclear parts of HA molecule as well as on a solution pH. coomplexation proceeds at pH 2.5-3.5 efficiently. On the basis of kinetic models it is shown that HA interaction with Hg (II) ions, at microconcentration of a pollutant (0.025-5.0 mkmol/dm3), has a zero order of reaction. Rate of a reaction does not depend on initial components concentration and is defined by process of Hg (II) ions diffusion to organic ligands. High correlation of a HA sorption capacity to Hg (II) ions is observed: with the nitrogen content and maintenance of amino groups (according to a 13C-NMR, element composition) and negative correlation - with degree of HA aromaticity. It testifies to primary binding of Hg (II) ions by amino-acid fragments of a HA molecule peripheral part. When concentration of Hg (II) ions increases, binding proceeds on carboxylic and phenolic groups of a molecule nuclear part. Higher order of kinetic models reaction and FTIR spectroscopy data testify to it. Comparison of FTIR spectra of HA preparations and mercury humates, shows that Hg (II) ions binding in humate complexes is carried out mainly by -COOH. Reduction of a spectral line intensity not ionized -COOH at 1700-1720 sm-1 and intensity increases of dissymetric valency vibration at 1610-1650 sm-1 diagnose increase

  7. Dry deposition of ammonia, nitric acid, ammonium, and nitrate to alpine tundra at Niwot Ridge, Colorado

    USGS Publications Warehouse

    Rattray, G.; Sievering, H.

    2001-01-01

    Micrometeorological measurements and ambient air samples, analyzed for concentrations of NH3, HNO3, NH4+, and NO3-, were collected at an alpine tundra site on Niwot Ridge, Colorado. The measured concentrations were extremely low and ranged between 5 and 70ngNm-3. Dry deposition fluxes of these atmospheric species were calculated using the micrometeorological gradient method. The calculated mean flux for NH3 indicates a net deposition to the surface and indicates that NH3 contributed significantly to the total N deposition to the tundra during the August-September measurement period. Our pre-measurement estimate of the compensation point for NH3 in air above the tundra was 100-200ngNm-3; thus, a net emission of NH3 was expected given the low ambient concentrations of NH3 observed. Based on our results, however, the NH3 compensation point at this alpine tundra site appears to have been at or below about 20ngNm-3. Large deposition velocities (>2cms-1) were determined for nitrate and ammonium and may result from reactions with surface-derived aerosols. Copyright (C) 2001 Elsevier Science B.V.Micrometeorological measurements and ambient air samples, analyzed for concentrations of NH3, HNO3, NH4+, and NO3-, were collected at an alpine tundra site on Niwot Ridge, Colorado. The measured concentrations were extremely low and ranged between 5 and 70 ng N m-3. Dry deposition fluxes of these atmospheric species were calculated using the micrometeorological gradient method. The calculated mean flux for NH3 indicates a net deposition to the surface and indicates that NH3 contributed significantly to the total N deposition to the tundra during the August-September measurement period. Our pre-measurement estimate of the compensation point for NH3 in air above the tundra was 100-200 ng N m-3; thus, a net emission of NH3 was expected given the low ambient concentrations of NH3 observed. Based on our results, however, the NH3 compensation point at this alpine tundra site appears to

  8. Assembly and Succession of Iron Oxide Microbial Mat Communities in Acidic Geothermal Springs.

    PubMed

    Beam, Jacob P; Bernstein, Hans C; Jay, Zackary J; Kozubal, Mark A; Jennings, Ryan deM; Tringe, Susannah G; Inskeep, William P

    2016-01-01

    Biomineralized ferric oxide microbial mats are ubiquitous features on Earth, are common in hot springs of Yellowstone National Park (YNP, WY, USA), and form due to direct interaction between microbial and physicochemical processes. The overall goal of this study was to determine the contribution of different community members to the assembly and succession of acidic high-temperature Fe(III)-oxide mat ecosystems. Spatial and temporal changes in Fe(III)-oxide accretion and the abundance of relevant community members were monitored over 70 days using sterile glass microscope slides incubated in the outflow channels of two acidic geothermal springs (pH = 3-3.5; temperature = 68-75°C) in YNP. Hydrogenobaculum spp. were the most abundant taxon identified during early successional stages (4-40 days), and have been shown to oxidize arsenite, sulfide, and hydrogen coupled to oxygen reduction. Iron-oxidizing populations of Metallosphaera yellowstonensis were detected within 4 days, and reached steady-state levels within 14-30 days, corresponding to visible Fe(III)-oxide accretion. Heterotrophic archaea colonized near 30 days, and emerged as the dominant functional guild after 70 days and in mature Fe(III)-oxide mats (1-2 cm thick). First-order rate constants of Fe(III)-oxide accretion ranged from 0.046 to 0.05 day(-1), and in situ microelectrode measurements showed that the oxidation of Fe(II) is limited by the diffusion of O2 into the Fe(III)-oxide mat. The formation of microterracettes also implicated O2 as a major variable controlling microbial growth and subsequent mat morphology. The assembly and succession of Fe(III)-oxide mat communities follows a repeatable pattern of colonization by lithoautotrophic organisms, and the subsequent growth of diverse organoheterotrophs. The unique geochemical signatures and micromorphology of extant biomineralized Fe(III)-oxide mats are also useful for understanding other Fe(II)-oxidizing systems. PMID:26913020

  9. Assembly and Succession of Iron Oxide Microbial Mat Communities in Acidic Geothermal Springs

    PubMed Central

    Beam, Jacob P.; Bernstein, Hans C.; Jay, Zackary J.; Kozubal, Mark A.; Jennings, Ryan deM.; Tringe, Susannah G.; Inskeep, William P.

    2016-01-01

    Biomineralized ferric oxide microbial mats are ubiquitous features on Earth, are common in hot springs of Yellowstone National Park (YNP, WY, USA), and form due to direct interaction between microbial and physicochemical processes. The overall goal of this study was to determine the contribution of different community members to the assembly and succession of acidic high-temperature Fe(III)-oxide mat ecosystems. Spatial and temporal changes in Fe(III)-oxide accretion and the abundance of relevant community members were monitored over 70 days using sterile glass microscope slides incubated in the outflow channels of two acidic geothermal springs (pH = 3–3.5; temperature = 68–75°C) in YNP. Hydrogenobaculum spp. were the most abundant taxon identified during early successional stages (4–40 days), and have been shown to oxidize arsenite, sulfide, and hydrogen coupled to oxygen reduction. Iron-oxidizing populations of Metallosphaera yellowstonensis were detected within 4 days, and reached steady-state levels within 14–30 days, corresponding to visible Fe(III)-oxide accretion. Heterotrophic archaea colonized near 30 days, and emerged as the dominant functional guild after 70 days and in mature Fe(III)-oxide mats (1–2 cm thick). First-order rate constants of Fe(III)-oxide accretion ranged from 0.046 to 0.05 day−1, and in situ microelectrode measurements showed that the oxidation of Fe(II) is limited by the diffusion of O2 into the Fe(III)-oxide mat. The formation of microterracettes also implicated O2 as a major variable controlling microbial growth and subsequent mat morphology. The assembly and succession of Fe(III)-oxide mat communities follows a repeatable pattern of colonization by lithoautotrophic organisms, and the subsequent growth of diverse organoheterotrophs. The unique geochemical signatures and micromorphology of extant biomineralized Fe(III)-oxide mats are also useful for understanding other Fe(II)-oxidizing systems. PMID:26913020

  10. Seasonal variation in soil nitrogen availability across a fertilization chronosequence in moist acidic tundra

    NASA Astrophysics Data System (ADS)

    McLaren, J. R.; Gough, L.; Weintraub, M. N.

    2012-12-01

    Changes in global climate may result in altered timing of seasonal events including the timing of the spring-thaw and fall freeze-up. In addition to this changing seasonality, arctic environments are experiencing overall increases in nutrient availability caused by climate warming resulting in alterations of plant species composition, such as the observed increases in the abundance of deciduous shrubs. Changing species composition may have large effects on nutrient dynamics in the surrounding ecosystem because of documented differences in how particular plant species influence soil nutrient availability. Although we have some idea of how plant identity influences soil nutrients, soil biogeochemical processes are strongly seasonal, and we have a poor understanding of how plant identity, or nutrient levels, may influence these seasonal patterns. We examined the responses of moist acidic tundra to experimentally increased soil nutrient availability and the accompanying increase in shrub abundance at the Arctic Long Term Ecological Research (LTER) site at Toolik Lake, Alaska. We examined a chrono-sequence of long-term fertilization experiments, composed of experiments fertilized for 5, 15 and 22 years, which has resulted in increasing shrub density with time since fertilization. The fertilized plots receive both nitrogen (N, 10 g/m2/yr) and phosphorus (5 g/m2/yr) annually following snowmelt. In the 2011 growing season we measured variation in soil available N weekly, including measures of ammonium (NH4), nitrate (NO3) and total free amino acids (TFAA). We found that differences between fertilized and control plots depended strongly on both the seasonal timing of measurements, as well as the duration of the fertilization treatment. Early in the growing season fertilization resulted in large increases in available soil N (both NH4 and NO3) across the entire chronosequence. As the season progressed, however, older fertilized plots show evidence of N saturation, where

  11. Microbially mediated sulphide production in a thermal, acidic algal mat community in Yellowstone National Park.

    PubMed

    Ferris, Michael J; Magnuson, Timothy S; Fagg, Jennifer A; Thar, Roland; Kühl, Michael; Sheehan, Kathy B; Henson, Joan M

    2003-10-01

    Our objective in this study was to characterize prokaryotic sulphide production within the oxygenic, predominantly eukaryotic algal mat in an acidic stream, Nymph Creek, in Yellowstone National Park (YNP). We used microsensors to examine fluctuations in H2S and O2 concentrations over time through the vertical aspect of the approximately 3 mm mat in a 46-48 degrees C region of the creek. We also used analyses of PCR-amplified 16S rRNA gene sequences obtained from denaturing gradient gels, and PCR-amplified sequences of a functional gene associated with microbial sulphate respiration (dsrA) to characterize the bacterial community in the same region of the mat. During midday, photosynthesis rates were high within the first 500 micro m interval of the mat and high oxygen concentrations (600% air saturation) penetrated deeply (>1800 micro m) into the mat. During early evening and night, oxygen concentrations within the first 1100 micro m of the mat decreased over time from 60% air saturation (a.s) to 12% a.s. A precipitous decline in oxygen concentration occurred at a depth of 1100 micro m in all night measurements and anoxic conditions were present below 1200 micro m. Within this anoxic region, sulphide concentrations increased from nearly 0 micro M at 1200 micro m depth to 100 micro M at 2400 micro m depth. Enrichment cultures inoculated with Nymph Creek mat organisms also produced H2S. Sequence analyses of 16S rRNA and dsrA genes indicated the presence of at least five bacterial genera including species involved in dissimilative sulphate or sulphur reduction. PMID:14510849

  12. MAT1A variants modulate the effect of dietary fatty acids on plasma homocysteine concentrations and DNA damage

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dietary n-3 polyunsaturated fatty acids (PUFA) are associated with decreased plasma homocysteine (Hcy), an important biomarker for cardiovascular disease. Methionine adenosyltransferase (MAT1A) is an enzyme involved in formation of form S-adenosylmethionine during methionine metabolism. The objectiv...

  13. Developments in absorptive glass mat separators for cycling applications and 36 V lead-acid batteries

    NASA Astrophysics Data System (ADS)

    Toniazzo, V.; Lambert, U.

    The major markets for valve-regulated lead-acid (VRLA) batteries are undergoing a radical upheaval. In particular, the telecommunications industry requires more reliable power supplies, and the familiar 12 V electrical system in cars will probably be soon replaced by a 36/42 V system, or by other electrical systems if part of the automotive market is taken over by hybrid electrical vehicles (HEVs). In order to meet these new challenges and enable VRLA batteries to provide a satisfactory life in float and cycling applications in the telecommunication field, or in the high-rate-partial-state-of-charge service required by both 36/42 V automobiles and HEVs, the lead-acid battery industry has to improve substantially the quality of present VRLA batteries based on absorptive glass mat (AGM) technology. Therefore, manufacturing steps and cell components have to be optimized, especially AGM separators as these are key components for better production yields and battery performance. This paper shows how the optimal segregation of the coarse and fine fibres in an AGM separator structure can improve greatly the properties of the material. The superior capillarity, springiness and mechanical properties of the 100% glass Amerglass multilayer separator compared with commercial monolayer counterparts with the same specific surface-area is highlighted.

  14. Advances in recombinant battery separator mat (RBSM) separators for lead-acid batteries—a review

    NASA Astrophysics Data System (ADS)

    Zguris, G. C.

    Microglass separators have been used in lead-acid batteries for more than 20 years with excellent results. This type of separator (known as recombinant battery separator mat (RBSM)) has allowed valve-regulated lead-acid (VRLA) battery technology to become a commercial reality. When the concept of the VRLA battery was developed, the requirements of the RBSM separator were not fully known nor appreciated. In many cases, the direction charted for the separator has not been the most beneficial path to follow for separator performance and battery life. In some cases, such as the density of the separator media, experience has shown that the most correct path (low density) does not give rise to long battery life. As VRLA battery technology matures, greater pressure on cost and quality has arisen, especially with the proposed transition to 42 V automotive applications. This paper reviews some of the advances and changes in the RBSM separator made over the last 20 years, and provides some thoughts on future directions for this essential component of the VRLA battery.

  15. Geoarchaeota: a new candidate phylum in the Archaea from high-temperature acidic iron mats in Yellowstone National Park.

    PubMed

    Kozubal, Mark A; Romine, Margaret; Jennings, Ryan deM; Jay, Zack J; Tringe, Susannah G; Rusch, Doug B; Beam, Jacob P; McCue, Lee Ann; Inskeep, William P

    2013-03-01

    Geothermal systems in Yellowstone National Park (YNP) provide an outstanding opportunity to understand the origin and evolution of metabolic processes necessary for life in extreme environments including low pH, high temperature, low oxygen and elevated concentrations of reduced iron. Previous phylogenetic studies of acidic ferric iron mats from YNP have revealed considerable diversity of uncultivated and undescribed archaea. The goal of this study was to obtain replicate de novo genome assemblies for a dominant archaeal population inhabiting acidic iron-oxide mats in YNP. Detailed analysis of conserved ribosomal and informational processing genes indicates that the replicate assemblies represent a new candidate phylum within the domain Archaea referred to here as 'Geoarchaeota' or 'novel archaeal group 1 (NAG1)'. The NAG1 organisms contain pathways necessary for the catabolism of peptides and complex carbohydrates as well as a bacterial-like Form I carbon monoxide dehydrogenase complex likely used for energy conservation. Moreover, this novel population contains genes involved in the metabolism of oxygen including a Type A heme copper oxidase, a bd-type terminal oxidase and a putative oxygen-sensing protoglobin. NAG1 has a variety of unique bacterial-like cofactor biosynthesis and transport genes and a Type3-like CRISPR system. Discovery of NAG1 is critical to our understanding of microbial community structure and function in extant thermophilic iron-oxide mats of YNP, and will provide insight regarding the evolution of Archaea in early Earth environments that may have important analogs active in YNP today. PMID:23151644

  16. Geoarchaeota: a new candidate phylum in the Archaea from high-temperature acidic iron mats in Yellowstone National Park

    SciTech Connect

    Kozubal, Mark; Romine, Margaret F.; Jennings, Ryan; Jay, Z.; Tringe, Susannah G.; Rusch, Douglas B.; Beam, Jake; McCue, Lee Ann; Inskeep, William P.

    2013-03-01

    Geothermal systems in Yellowstone National Park (YNP) provide an outstanding opportunity to understand the origin and evolution of metabolic processes necessary for life in extreme environments including low pH, high temperature, low oxygen and elevated concentrations of reduced iron. Previous phylogenetic studies of acidic ferric iron mats from YNP have revealed considerable diversity of uncultivated and undescribed archaea. The goal of this study was to obtain replicate de novo genome assemblies for a dominant archaeal population inhabiting acidic iron oxide mats in YNP. Detailed analysis of conserved ribosomal and informational processing genes indicate that the replicate assemblies represent a new phylum-level lineage referred to here as 'novel archaeal group 1 (NAG1)'. The NAG1 organisms contain pathways necessary for the catabolism of peptides and complex carbohydrates as well as a bacterial-like Form I CO dehydrogenase complex likely used for energy conservation. Moreover, this novel population contains genes involved in metabolism of oxygen including a Type A heme copper oxidase, a bd-type terminal oxidase and a putative oxygen sensing protoglobin. NAG1 has a variety of unique bacterial-like cofactor biosynthesis and transport genes and a Type3-like CRISPR system. Discovery of NAG1 is critical to our understanding of microbial community structure and function in extant thermophilic iron mats of YNP, and will provide insight regarding the evolution of Archaea in early Earth environments that may have important analogues active in YNP today.

  17. Citric Acid Treatment of Flax, Cotton and Blended Nonwoven Mats for Copper Ion Absorption

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The removal of metal ions from polluted wate and wastewater with biodegradeable, natural products is an area of current interest in the environmental arena. The objective of this study is to determine whether nonwoven mats made of biodegradeable, natural fibers of flax and cotton can be used for rem...

  18. CITRIC ACID TREATMENT OF FLAX, COTTON AND BLENDED NONWOVEN MATS FOR COPPER ION ABSORPTION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The removal of metal ions from polluted water and wastewater with biodegradable, natural products is an area of current interest in the environmental arena. The objective of this study is to determine whether nonwoven mats made of biodegradable, natural fibers of flax and cotton can be used for rem...

  19. Effect of silver nanoparticles and cellulose nanocrystals on electrospun poly(lactic) acid mats: morphology, thermal properties and mechanical behavior.

    PubMed

    Cacciotti, Ilaria; Fortunati, Elena; Puglia, Debora; Kenny, Josè Maria; Nanni, Francesca

    2014-03-15

    The fabrication of ternary fibrous mats based on poly(lactic) acid (PLA), cellulose nanocrystals (CNCs, both pristine (p-CNCs) and modified with a commercial surfactant (s-CNCs)) and silver (Ag) nanoparticles by electrospinning is reported. Amounts of 1 and 5 wt.% were selected for Ag and CNCs, respectively. Neat PLA and binary PLA/Ag, PLA/p-CNCs and PLA/s-CNCs were produced as references. The CNCs and Ag influence on the microstructural, thermal and mechanical properties was investigated. The Ag and/or p-CNCs addition did not remarkably affect fiber morphology and average size dimension (between (468 ± 111) and (551 ± 122)nm), whereas the s-CNCs presence led to the deposition of a honeycomb-like network on a underneath layer of randomly oriented fibers. The efficiency of the surfactant use in promoting the CNC dispersion was demonstrated. A slight enhancement (e.g. around 25%, in terms of strength) of the mechanical properties of p-CNCs loaded fibers, particularly for PLA/Ag/p-CNCs, was revealed, whereas mats with s-CNCs showed a decrement (e.g. around 35-45%, in terms of strength), mainly imputable to the delamination between the upper honeycomb-like layer and the lower conventional fibrous mat. PMID:24528696

  20. Development of Suberin Fatty Acids and Chloramphenicol-Loaded Antimicrobial Electrospun Nanofibrous Mats Intended for Wound Therapy.

    PubMed

    Tamm, Ingrid; Heinämäki, Jyrki; Laidmäe, Ivo; Rammo, Liisi; Paaver, Urve; Ingebrigtsen, Sveinung G; Škalko-Basnet, Nataša; Halenius, Anna; Yliruusi, Jouko; Pitkänen, Pauliina; Alakurtti, Sami; Kogermann, Karin

    2016-03-01

    Suberin fatty acids (SFAs) isolated from outer birch bark were investigated as an antimicrobial agent and biomaterial in nanofibrous mats intended for wound treatment. Electrospinning (ES) was used in preparing the composite nonwoven nanomats containing chloramphenicol (CAM; as a primary antimicrobial drug), SFAs, and polyvinylpyrrolidone (as a carrier polymer for ES). The X-ray powder diffraction, differential scanning calorimetry, scanning electron microscopy, atomic force microscopy, and texture analysis were used for the physicochemical and mechanical characterization of the nanomats. ES produced nanofibrous mats with uniform structure and with an average fiber diameter ranging from 370 to 425 nm. Microcrystalline SFAs and crystalline CAM were found to undergo a solid-state transformation during ES processing. The ES process caused also the loss of CAM in the final nanofibers. In the texture analysis, the SFAs containing nanofibers exhibited significantly higher maximum detachment force to an isolated pig skin (p < 0.05) than that obtained with the reference nanofibers. CAM exists in an amorphous form in the nanofibers which needs to be taken into account in controlling the physical storage stability. In conclusion, homogeneous composite nanofibrous mats for wound healing can be electrospun from the ternary mixture(s) of CAM, SFAs, and polyvinylpyrrolidone. PMID:26886306

  1. Belowground plant biomass allocation in tundra ecosystems and its relationship with temperature

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Heijmans, Monique M. P. D.; Mommer, Liesje; van Ruijven, Jasper; Maximov, Trofim C.; Berendse, Frank

    2016-05-01

    Climate warming is known to increase the aboveground productivity of tundra ecosystems. Recently, belowground biomass is receiving more attention, but the effects of climate warming on belowground productivity remain unclear. Enhanced understanding of the belowground component of the tundra is important in the context of climate warming, since most carbon is sequestered belowground in these ecosystems. In this study we synthesized published tundra belowground biomass data from 36 field studies spanning a mean annual temperature (MAT) gradient from ‑20 °C to 0 °C across the tundra biome, and determined the relationships between different plant biomass pools and MAT. Our results show that the plant community biomass–temperature relationships are significantly different between above and belowground. Aboveground biomass clearly increased with MAT, whereas total belowground biomass and fine root biomass did not show a significant increase over the broad MAT gradient. Our results suggest that biomass allocation of tundra vegetation shifts towards aboveground in warmer conditions, which could impact on the carbon cycling in tundra ecosystems through altered litter input and distribution in the soil, as well as possible changes in root turnover.

  2. Geoarchaeota: a new candidate phylum in the Archaea from high-temperature acidic iron mats in Yellowstone National Park

    PubMed Central

    Kozubal, Mark A; Romine, Margaret; Jennings, Ryan deM; Jay, Zack J; Tringe, Susannah G; Rusch, Doug B; Beam, Jacob P; McCue, Lee Ann; Inskeep, William P

    2013-01-01

    Geothermal systems in Yellowstone National Park (YNP) provide an outstanding opportunity to understand the origin and evolution of metabolic processes necessary for life in extreme environments including low pH, high temperature, low oxygen and elevated concentrations of reduced iron. Previous phylogenetic studies of acidic ferric iron mats from YNP have revealed considerable diversity of uncultivated and undescribed archaea. The goal of this study was to obtain replicate de novo genome assemblies for a dominant archaeal population inhabiting acidic iron-oxide mats in YNP. Detailed analysis of conserved ribosomal and informational processing genes indicates that the replicate assemblies represent a new candidate phylum within the domain Archaea referred to here as ‘Geoarchaeota' or ‘novel archaeal group 1 (NAG1)'. The NAG1 organisms contain pathways necessary for the catabolism of peptides and complex carbohydrates as well as a bacterial-like Form I carbon monoxide dehydrogenase complex likely used for energy conservation. Moreover, this novel population contains genes involved in the metabolism of oxygen including a Type A heme copper oxidase, a bd-type terminal oxidase and a putative oxygen-sensing protoglobin. NAG1 has a variety of unique bacterial-like cofactor biosynthesis and transport genes and a Type3-like CRISPR system. Discovery of NAG1 is critical to our understanding of microbial community structure and function in extant thermophilic iron-oxide mats of YNP, and will provide insight regarding the evolution of Archaea in early Earth environments that may have important analogs active in YNP today. PMID:23151644

  3. Contrasting denitrifier communities relate to contrasting N2O emission patterns from acidic peat soils in arctic tundra

    PubMed Central

    Palmer, Katharina; Biasi, Christina; Horn, Marcus A

    2012-01-01

    Cryoturbated peat circles (that is, bare surface soil mixed by frost action; pH 3–4) in the Russian discontinuous permafrost tundra are nitrate-rich ‘hotspots' of nitrous oxide (N2O) emissions in arctic ecosystems, whereas adjacent unturbated peat areas are not. N2O was produced and subsequently consumed at pH 4 in unsupplemented anoxic microcosms with cryoturbated but not in those with unturbated peat soil. Nitrate, nitrite and acetylene stimulated net N2O production of both soils in anoxic microcosms, indicating denitrification as the source of N2O. Up to 500 and 10 μ nitrate stimulated denitrification in cryoturbated and unturbated peat soils, respectively. Apparent maximal reaction velocities of nitrite-dependent denitrification were 28 and 18 nmol N2O gDW−1 h−1, for cryoturbated and unturbated peat soils, respectively. Barcoded amplicon pyrosequencing of narG, nirK/nirS and nosZ (encoding nitrate, nitrite and N2O reductases, respectively) yielded ≈49 000 quality-filtered sequences with an average sequence length of 444 bp. Up to 19 species-level operational taxonomic units were detected per soil and gene, many of which were distantly related to cultured denitrifiers or environmental sequences. Denitrification-associated gene diversity in cryoturbated and in unturbated peat soils differed. Quantitative PCR (inhibition-corrected per DNA extract) revealed higher copy numbers of narG in cryoturbated than in unturbated peat soil. Copy numbers of nirS were up to 1000 × higher than those of nirK in both soils, and nirS nirK−1 copy number ratios in cryoturbated and unturbated peat soils differed. The collective data indicate that the contrasting N2O emission patterns of cryoturbated and unturbated peat soils are associated with contrasting denitrifier communities. PMID:22134649

  4. Soil bacterial community shifts in response to vegetation and soil temperature change in moist acidic tundra of Northern Alaska

    NASA Astrophysics Data System (ADS)

    Ricketts, M. P.; Gonzalez-Meler, M. A.

    2013-12-01

    The effects of rising temperatures on Earth's ecosystems remain largely unknown and are an active area of research. In temperate systems, plant species often respond directly to climate forcing factors causing complex cascading effects in ecosystem C and nutrient cycling. Similarly, in the Arctic tundra, shifts in aboveground species composition and distribution have been observed in response to warming and other climate change factors, following increases in active layer depth and soil temperature. These abiotic changes provide soil microorganisms access to previously unavailable soil organic matter via thawing soils and increases soil microbial mineralization rates, suggesting that soil microorganisms may be eliciting the plant response. It is hypothesized that this release of nutrients may be providing a competitive advantage to N rich woody species, such as dwarf birch and diamond-leaf willow, over grassy species such as cottongrass tussock. Here we examine how microbial communities respond to increases in soil thermal insulation and vegetative change caused by the accumulation of winter precipitation at a snowfence installed in 1998 at Toolik Field Station, Alaska. In addition to soil temperature, increased snow depth also results in increased surface moisture, soil temperature, and active layer depth. Bacterial phylogenies and relative abundances from soils collected in August of 2012 were determined by sequencing 16S rRNA genes and analyzed using the QIIME software package. We found many significant relative abundance shifts between snow depth treatments (deep, intermediate, low) and soil depths (organic, transition, mineral), most notable of which include in an increase in Deltaproteobacteria in the deep treatment zones, a decrease in Alphaproteobacteria with increased soil depth, and a marked increase in Chloroflexi Anaerolineae (a green non-sulfur bacteria found in a wide range of habitats) in the deep treatment and mineral layers. Other interesting

  5. Sulfonic Acid- and Lithium Sulfonate-Grafted Poly(Vinylidene Fluoride) Electrospun Mats As Ionic Liquid Host for Electrochromic Device and Lithium-Ion Battery.

    PubMed

    Zhou, Rui; Liu, Wanshuang; Leong, Yew Wei; Xu, Jianwei; Lu, Xuehong

    2015-08-01

    Electrospun polymer nanofibrous mats loaded with ionic liquids (ILs) are promising nonvolatile electrolytes with high ionic conductivity. The large cations of ILs are, however, difficult to diffuse into solid electrodes, making them unappealing for application in some electrochemical devices. To address this issue, a new strategy is used to introduce proton conduction into an IL-based electrolyte. Poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) copolymer is functionalized with sulfonic acid through covalent attachment of taurine. The sulfonic acid-grafted P(VDF-HFP) electrospun mats consist of interconnected nanofibers, leading to remarkable improvement in dimensional stability of the mats. IL-based polymer electrolytes are prepared by immersing the modified mats in 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM(+)BF4(-)). It is found that the SO3(-) groups can have Lewis acid-base interactions with the cations (BMIM(+)) of IL to promote the dissociation of ILs, and provide additional proton conduction, resulting in significantly improved ionic conductivity. Using this novel electrolyte, polyaniline-based electrochromic devices show higher transmittance contrast and faster switching behavior. Furthermore, the sulfonic acid-grafted P(VDF-HFP) electrospun mats can also be lithiated, giving additional lithium ion conduction for the IL-based electrolyte, with which Li/LiCoO2 batteries display enhanced C-rate performance. PMID:26167794

  6. Improving cytoactive of endothelial cell by introducing fibronectin to the surface of poly L-Lactic acid fiber mats via dopamine.

    PubMed

    Yang, Wufeng; Zhang, Xiazhi; Wu, Keke; Liu, Xiaoyan; Jiao, Yanpeng; Zhou, Changren

    2016-12-01

    A simple but straightforward approach was reported to prepare fiber mats modified with fibronectin (Fn) protein for endothelial cells activity study. Based on the self-polymerization and strong adhesion feature of dopamine, poly L-Lactic acid (PLLA) fibers mat was modified via simply immersing them into dopamine solution for 16h. Subsequently, Fn was immobilized onto the fiber mats surface by the coupling reactive polydopamine (PDA) layer and Fn. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to determine the chemical compositions of fiber mats surface, which confirmed the successful immobilization of PDA and Fn molecules on the fiber surface. Scanning electronic microscopy (SEM) was used to observe the surface morphology changes after modification with PDA and Fn. The data of water contact angle showed that the hydrophilicity of the fiber mats was improved after surface modification. The data of in vitro cell culture proved that the PDA and Fn modified surface significantly enhanced the adhesion, proliferation and cell activity of endothelial cells on the fiber mats. And the release of tumor necrosis factor-α (TNF-α) by endothelial cells on the modified surface was suppressed compared to that on culture plate and PLLA film at 2 and 4days, while the secretion of interleukin-1β (IL-1β) was increased compared to that on culture plate and PLLA film at 2days. PMID:27612725

  7. New York's TUNDRA.

    ERIC Educational Resources Information Center

    Kalinowski, Thomas

    1983-01-01

    Found at the summit of some of the highest peaks of New York State's Adirondack Mountains are low-growing plants similar, and in many cases, identical to plants growing in the Arctic. Describes these plants and the environment in which they are found. Includes a color plate of alpine tundra plants. (Author/JN)

  8. Benthic plant communities in acidic Lake Colden, New York: Sphagnum and the algal mat

    SciTech Connect

    Hendrey, G R; Vertucci, J A

    1980-03-01

    Lake Colden, in the central Adirondack Mountains of New York State is botanically similar to acidified lakes in Sweden. Acidification of some Swedish lakes has been associated with an expansion of Sphagnum, primarily in shallow, sheltered littoral areas but also to depths of 18m. During a brief botanical survey on 24-25 July 1979, we observed a dense meadow of Sphagnum pylaesii around much of the shoreline of Lake Colden. Plant community composition was determined by a visual estimate of cover along a single typical transect and through underwater photography on 28-29 August 1979. Water samples were collected and returned to our laboratory for analyses several days later. Sample pH was determined by potentiometry and alkalinity by multiple end point titrations. Biomass samples were also taken of the Sphagnum mat community and dry weight was determined. Chemical content of plant tissue was analyzed.

  9. Mercury methylation in Sphagnum moss mats and its association with sulfate-reducing bacteria in an acidic Adirondack forest lake wetland.

    PubMed

    Yu, Ri-Qing; Adatto, Isaac; Montesdeoca, Mario R; Driscoll, Charles T; Hines, Mark E; Barkay, Tamar

    2010-12-01

    Processes leading to the bioaccumulation of methylmercury (MeHg) in northern wetlands are largely unknown. We have studied various ecological niches within a remote, acidic forested lake ecosystem in the southwestern Adirondacks, NY, to discover that mats comprised of Sphagnum moss were a hot spot for mercury (Hg) and MeHg accumulation (190.5 and 18.6 ng g⁻¹ dw, respectively). Furthermore, significantly higher potential methylation rates were measured in Sphagnum mats as compared with other sites within Sunday Lake's ecosystem. Although MPN estimates showed a low biomass of sulfate-reducing bacteria (SRB), 2.8 × 10⁴ cells mL⁻¹ in mat samples, evidence consisting of (1) a twofold stimulation of potential methylation by the addition of sulfate, (2) a significant decrease in Hg methylation in the presence of the sulfate reduction inhibitor molybdate, and (3) presence of dsrAB-like genes in mat DNA extracts, suggested that SRB were involved in Hg methylation. Sequencing of dsrB genes indicated that novel SRB, incomplete oxidizers including Desulfobulbus spp. and Desulfovibrio spp., and syntrophs dominated the sulfate-reducing guild in the Sphagnum moss mat. Sphagnum, a bryophyte dominating boreal peatlands, and its associated microbial communities appear to play an important role in the production and accumulation of MeHg in high-latitude ecosystems. PMID:20955196

  10. Three-layered absorptive glass mat separator with membrane for application in valve-regulated lead-acid batteries

    NASA Astrophysics Data System (ADS)

    Naidenov, V.; Pavlov, D.; Cherneva, M.

    During charge and discharge of the lead-acid cell equal amounts of H 2SO 4 participate in the reactions at the two types of plates (electrodes). However, the charge and discharge reactions at the positive plates involve also 2 mol of water per every mole of reacted PbO 2. Consequently, a concentration difference appears in the electrolyte between the two electrodes (horizontal stratification), which affects the reversibility of the processes at the two electrodes and thus the cycle life of the battery. The present paper proposes the use of a three-layered absorptive glass mat (AGM) separator, the middle layer playing the role of a membrane that divides (separates) the anodic and cathodic electrolyte spaces, and controls the exchange rates of H 2SO 4, H + ions, O 2 and H 2O flows between the two electrode spaces. To be able to perform this membrane function, the thinner middle AGM layer (0.2 mm) is processed with an appropriate polymeric emulsion to acquire balanced hydrophobic/hydrophilic properties, which sustain constant H 2SO 4 concentration in the two electrode spaces during cycling. Three types of polymeric emulsions have been used for treatment of the membrane: (a) polyvinylpyrollidonestyrene (MPVS), (b) polyvinylpyrrolidone "Luviskol" (MPVP), or (c) polytetrafluorethylene modified with Luviskol (MMAGM). It is established experimentally that the MMAGM membrane maintains equal acid concentration in the anodic and cathodic spaces (no horizontal stratification) during battery cycling and hence ensures longer cycle life performance.

  11. Osteogenesis of human adipose-derived stem cells on poly(dopamine)-coated electrospun poly(lactic acid) fiber mats.

    PubMed

    Lin, Chi-Chang; Fu, Shu-Juan

    2016-01-01

    Electrospinning is a versatile technique to generate large quantities of micro- or nano-fibers from a wide variety of shapes and sizes of polymer. The aim of this study is to develop functionalized electrospun nano-fibers and use a mussel-inspired surface coating to regulate adhesion, proliferation and differentiation of human adipose-derived stem cells (hADSCs). We prepared poly(lactic acid) (PLA) fibers coated with polydopamine (PDA). The morphology, chemical composition, and surface properties of PDA/PLA were characterized by SEM and XPS. PDA/PLA modulated hADSCs' responses in several ways. Firstly, adhesion and proliferation of hADSCs cultured on PDA/PLA were significantly enhanced relative to those on PLA. Increased focal adhesion kinase (FAK) and collagen I levels and enhanced cell attachment and cell cycle progression were observed upon an increase in PDA content. In addition, the ALP activity and osteocalcin of hADSCs cultured on PDA/PLA were significantly higher than seen in those cultured on a pure PLA mat. Moreover, hADSCs cultured on PDA/PLA showed up-regulation of the ang-1 and vWF proteins associated with angiogenesis differentiation. Our results demonstrate that the bio-inspired coating synthetic degradable PLA polymer can be used as a simple technique to render the surfaces of synthetic biodegradable fibers, thus enabling them to direct the specific responses of hADSCs. PMID:26478309

  12. Stress-Survival Gene Identification From an Acid Mine Drainage Algal Mat Community

    NASA Astrophysics Data System (ADS)

    Urbina-Navarrete, J.; Fujishima, K.; Paulino-Lima, I. G.; Rothschild-Mancinelli, B.; Rothschild, L. J.

    2014-12-01

    Microbial communities from acid mine drainage environments are exposed to multiple stressors to include low pH, high dissolved metal loads, seasonal freezing, and desiccation. The microbial and algal communities that inhabit these niche environments have evolved strategies that allow for their ecological success. Metagenomic analyses are useful in identifying species diversity, however they do not elucidate the mechanisms that allow for the resilience of a community under these extreme conditions. Many known or predicted genes encode for protein products that are unknown, or similarly, many proteins cannot be traced to their gene of origin. This investigation seeks to identify genes that are active in an algal consortium during stress from living in an acid mine drainage environment. Our approach involves using the entire community transcriptome for a functional screen in an Escherichia coli host. This approach directly targets the genes involved in survival, without need for characterizing the members of the consortium.The consortium was harvested and stressed with conditions similar to the native environment it was collected from. Exposure to low pH (< 3.2), high metal load, desiccation, and deep freeze resulted in the expression of stress-induced genes that were transcribed into messenger RNA (mRNA). These mRNA transcripts were harvested to build complementary DNA (cDNA) libraries in E. coli. The transformed E. coli were exposed to the same stressors as the original algal consortium to select for surviving cells. Successful cells incorporated the transcripts that encode survival mechanisms, thus allowing for selection and identification of the gene(s) involved. Initial selection screens for freeze and desiccation tolerance have yielded E. coli that are 1 order of magnitude more resistant to freezing (0.01% survival of control with no transcript, 0.2% survival of E. coli with transcript) and 3 orders of magnitude more resistant to desiccation (0.005% survival of

  13. Paenibacillus tundrae sp. nov. and Paenibacillus xylanexedens sp. nov., Psychrotolerant, Xylan-Degrading, Bacteria from Alaskan Tundra

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Psychrotolerant, xylan-degrading, strains of bacteria were isolated from soil beneath moist non-acidic and acidic tundra in northern Alaska. Phylogenetic analysis based on 16S rRNA gene sequences revealed that each strain belonged to the genus Paenibacillus. The highest levels of 16S rRNA gene sim...

  14. Shrub tundra snowmelt

    NASA Astrophysics Data System (ADS)

    Pomeroy, J. W.; Bewley, D. S.; Essery, R. L. H.; Hedstrom, N. R.; Link, T.; Granger, R. J.; Sicart, J. E.; Ellis, C. R.; Janowicz, J. R.

    2006-03-01

    Observations of land surface and snowpack energetics and mass fluxes were made over arctic shrub tundra of varying canopy height and density using radiometers, eddy covariance flux measurements, and snow mass changes from snow surveys of depth and density. Over several years, snow accumulation in the shrubs was found to be consistently higher than in sparse tundra due to greater retention of snowfall by all shrubs and wind redistribution of snowfall to tall shrubs. Where snow accumulation was highest due to snow redistribution, shrubs often became buried by the end of winter. Three classes of shrub-snow interactions were observed: tall shrubs that were exposed over snow, tall shrubs that were bent over and buried by snow, and short shrubs buried by snow. Tall shrubs buried by snow underwent spring-up during melt. Though spring-up was episodic for a single shrub, over an area it was a progressive emergence from early to mid melt of vegetation that dramatically altered the radiative and aerodynamic properties of the surface. Short shrubs were exposed more rapidly once snow depth declined below shrub height, usually near the end of melt. Net radiation increased with increasing shrub due to the decreased reflectance of shortwave radiation overwhelming the increased longwave emission from relatively warm and dark shrubs. Net radiation to snow under shrubs was much smaller than that over shrubs, but was greater than that to snow with minimal shrub exposure, in this case the difference was due to downward longwave radiation from the canopy exceeding the effect of attenuated shortwave transmission through the canopy. Because of reduced turbulent transfer under shrub canopies and minimal water vapour contributions from the bare shrub branches, sublimation fluxes declined with increasing shrub exposure. In contrast, sensible heat fluxes to the shrub surface became more negative and those to the underlying snow surface more positive with increasing shrub exposure, because of

  15. Biogeochemistry of Microbial Mats

    NASA Technical Reports Server (NTRS)

    DesMarais, David J.; DeVincenizi, D. (Technical Monitor)

    2002-01-01

    The hierarchical organization of microbial ecosystems determines the rates of processes that shape Earth's environment, define the stage upon which major evolutionary events occurred, and create biosignatures in sediments and atmospheres. In cyanobacterial mats, oxygenic photosynthesis provides energy, organic substrates and oxygen to the ecosystem. Incident light changes with depth in the mat, both in intensity and spectral composition, and counteracting gradients of oxygen and sulfide shape the chemical microenvironment. A combination of benefits and hazards of light, oxygen and sulfide promotes the allocation of the various essential mat processes between light and dark periods and to various depths in the mat. Microliters produce hydrogen, small organic acids, nitrogen and sulfur species. Such compounds fuel a flow of energy and electrons in these ecosystems and thus shape interactions between groups of microorganisms. Coordinated observations of population distribution, abundance, and activity for an entire community are making fundamental questions in ecology accessible. These questions address those factors that sustain the remarkable diversity of microorganisms that are now being revealed by molecular techniques. These questions also target the processes that shape the various kinds of biosignatures that we will seek, both in ancient rocks from Earth and Mars, and in atmospheres of distant planets beyond our Solar System.

  16. USE OF PHOSPHOLIPID FATTY ACID PROFILES TO STUDY THE MICROBIAL COMPOSITION OF CYANOBACTERIAL MATS IN CABO ROJO SOLAR SALTERNS

    EPA Science Inventory

    The Cabo Rojo Saltern located in the West side of Puerto Rico is a hypersaline ecosystem that consists of crystallizer ponds surrounded by series of cyanobacterial mats. Although this ecosystem harbors a variety of microorganisms not much is known about their identity and relati...

  17. Micro-structural design and function of an improved absorptive glass mat (AGM) separator for valve-regulated lead-acid batteries

    NASA Astrophysics Data System (ADS)

    Nakayama, Y.; Kishimoto, K.; Sugiyama, S.; Sakaguchi, S.

    Two important properties of absorptive glass mat (AGM) separators are examined in order to design optimum separators for advanced valve-regulated lead-acid (VRLA) batteries. Acid stratification in the separator depends on its micro-glass-fibre diameter, and it is found that the extent of stratification can be estimated based on hydrodynamics theory. Decreasing the plate-group pressure of the separator in the wetted state is also investigated, and it is considered that the phenomenon is caused by the balance between the fibre strength and the surface tension of acid solution. Given these results, the way to design AGM separators according to purpose has been identified. Accordingly, a new AGM separator has been developed and this functions both to suppress stratification and to maintain plate-group pressure.

  18. Fabrication Of Ceramic Mats

    NASA Technical Reports Server (NTRS)

    Collins, Earl R., Jr.

    1991-01-01

    Process to make mats of fine zirconia filaments proposed. Ceramic mats formed by sintering mats of partially dried filaments extruded from slurry of ceramic powder, binder, and solvent. Mats of fine zirconia fibers easier to ball-mill than commercially available zirconia powder.

  19. Archean Microbial Mat Communities

    NASA Astrophysics Data System (ADS)

    Tice, Michael M.; Thornton, Daniel C. O.; Pope, Michael C.; Olszewski, Thomas D.; Gong, Jian

    2011-05-01

    Much of the Archean record of microbial communities consists of fossil mats and stromatolites. Critical physical emergent properties governing the evolution of large-scale (centimeters to meters) topographic relief on the mat landscape are (a) mat surface roughness relative to the laminar sublayer and (b) cohesion. These properties can be estimated for fossil samples under many circumstances. A preliminary analysis of Archean mat cohesion suggests that mats growing in shallow marine environments from throughout this time had cohesions similar to those of modern shallow marine mats. There may have been a significant increase in mat strength at the end of the Archean.

  20. Changes in tundra vascular plant biomass over thirty years at Imnavait Creek, Alaska.

    NASA Astrophysics Data System (ADS)

    Bret-Harte, M. S.; Euskirchen, E. S.; Edgar, C.; Huebner, D. C.; Okano, K.; Tucker, C.; Genet, H.; Ray, P. M.; Shaver, G. R.

    2014-12-01

    Understanding the magnitude of, and controls over, CO2 and water fluxes in arctic ecosystems is essential for accurate assessment and prediction of their responses to climate change. In 2013, we harvested vegetation and soils in the most common plant community types located in the source areas for fluxes measured by eddy covariance towers located in three representative Alaska tundra ecosystems along a toposequence (a ridge site composed of heath tundra and moist non-acidic tundra, a mid-slope site composed of moist acidic tussock tundra, and a valley bottom fen site composed of wet sedge tundra and moist acidic tundra) at Imnavait Creek, Alaska. While the purpose of this harvest was to relate biomass and production to estimates of overall net ecosystem CO2 exchange (NEE), gross primary productivity (GPP) and ecosystem respiration (ER) obtained by micrometeorological methods, it also afforded an opportunity to compare with biomass harvests done in the 1980s in moist acidic tundra at Imnavait Creek; there have been no other harvests than ours at Imnavait since then. Our data showed that plant biomass and production were greatest in the tussock tundra at the mid-slope tower, and least in the wet sedge community at the fen tower, while plant diversity was greatest in the communities at the ridge site. Aboveground biomass of vascular plants in our 2013 harvest in moist acidic tundra was nearly three times higher than that measured approximately thirty years earlier in three harvests of nearby areas at Imnavait Creek, due to an increase in the biomass of shrubs and graminoids. Comparison with other biomass harvests from the vicinity of Toolik Field Station indicate that vascular plant biomass in moist acidic tundra has increased over this time period, with the greatest increase evident by the mid-1990s, and a more gradual increase through to the present time, despite no obvious increase in air temperature as seen in data from nearby climate stations. These data will be

  1. Seasonal variation of ecosystem respiration delta 13C in response to experimental permafrost thaw and vegetation removal in moist acidic tundra

    NASA Astrophysics Data System (ADS)

    Mauritz, M.; Pegoraro, E.; Salmon, V. G.; Natali, S.; Schuur, E.

    2015-12-01

    Permafrost soils store twice as much carbon (C) as is contained in the atmosphere and about one-third of global soil C. Under a warmer future climate, permafrost is expected to thaw and decompose, releasing C to the atmosphere, further amplifying global warming. However, studies show that warmer arctic temperatures promote plant growth, in addition to stimulating losses from the soil C pool. Using delta 13C of ecosystem respiration (Reco) during the seasonal cycle of active layer thaw, we seek to understand the effect of permafrost thaw on the relative contributions from microbial decomposition of soil C and more recently fixed, plant-dominated C. We measured weekly CO2 flux rates and delta 13C of Reco from experimentally warmed plots with rapid permafrost thaw and control thaw. Vegetation removal plots, in un-warmed tundra, were monitored to isolate the seasonal contributions from soil alone. We expected delta 13C to be dominated by plant activity in vegetated plots, particularly in areas with greater permafrost thaw because they have highest plant biomass. In vegetation removal plots we expected to see greater contribution from deep soil as seasonal thaw progressed. From May to July delta 13C was extremely variable early in the growing season, but became more uniform as vegetation greened and thaw deepened. In vegetated plots CO2 fluxes doubled, but remained constant in vegetation removal plots. This indicates that, with thaw, microbes had access to a more spatially uniform C substrate, but this had little effect on the magnitude of CO2 flux. Overall delta 13C in rapidly thawed plots was least enriched (-29.4 ‰), control plots intermediate (-28.9 ‰), and vegetation removal plots were most enriched (-28.5 ‰). This suggests that in vegetation removal plots microbes used more decomposed soil C as substrate, and much of the increase in CO2 flux in vegetated plots was the result of C recently fixed and contributed by plants.

  2. Aboveground and belowground responses to nutrient additions and herbivore exclusion in Arctic tundra ecosystems in northern Alaska

    NASA Astrophysics Data System (ADS)

    Moore, J. C.; Gough, L.; Simpson, R.; Johnson, D. R.

    2011-12-01

    The Arctic has experienced significant increased regional warming over the past 30 years. Warming generally increases tundra soil nutrient availability by creating a more favorable environment for plant growth, decomposition and nutrient mineralization. Aboveground there has been a "greening" of the Arctic with increased net primary productivity (NPP), and an increase in woody vegetation. Concurrent with the changes aboveground has been an increase in root growth at lower depths and a loss of soil organic C (40 -100 g C m-2 yr-1). Given that arctic soils contain 14% of the global soil C pool, understanding the mechanisms behind shifts of this magnitude that are changing arctic soils from a net sink to a net source of atmospheric C is critical. We took an integrated multi-trophic level approach to examine how altering soil nutrients and mammalian herbivore activity affects vegetation, soil fauna, and microbial communities as well as soil physical characteristics in moist acidic (MAT) and dry heath (DH) tundra. Our work was conducted at the Arctic LTER site in northern Alaska. We sampled the nutrient (controls and annual N+P additions) and herbivore (controls and exclosures) manipulations established in 1996 after 10 years of treatment. Models that incorporated the biomass estimates from the field were used to characterize the trophic structure of the belowground food web and to estimate carbon flux among soil organisms and C-mineralization rates. Both MAT and DH exhibited significant increases in NPP and root growth and changes in vegetation structure with transitions from a mixed community to deciduous shrubs in MAT and from lichens to grasses and shrubs in DH, with nutrient additions and herbivore exclosures. Belowground responses to the treatments were dependent on ecosystem type, but exposed alterations in trophic structure that included changes in microbial biomass, the establishment of microbivorous enchytreaids, increases in root-feeding nematodes, and

  3. Deposition of ozone to tundra

    NASA Technical Reports Server (NTRS)

    Jacob, D. J.; Fan, S.-M.; Wofsy, S. C.; Spiro, P. A.; Bakwin, P. S.; Ritter, J. A.; Browell, E. V.; Gregory, G. L.; Fitzjarrald, D. R.; Moore, K. E.

    1992-01-01

    Eddy correlation measurements of O3 deposition fluxes to tundra during the Arctic Boundary Layer Expedition (ABLE 3A) are reported. The mean O3 deposition velocity was 0.24 cm/s in the daytime and 0.12 cm/s at night. The day-to-day difference in deposition velocity was driven by both atmospheric stability and surface reactivity. The mean surface resistance to O3 deposition was 2.6 s/cm in the daytime and 3.4 s/cm at night. The relatively low surface resistance at night is attributed to light-insensitive uptake of O3 at dry upland tundra surfaces. The small day-tonight difference in surface resistance is attributed to additional stomatal uptake by wet meadow tundra plants in the daytime. The mean O3 deposition flux to the world north of 60 deg N in July-August is estimated at 8.2 x 10 exp 10 molecules/sq cm/s. Suppression of photochemical loss by small anthropogenic inputs of nitrogen oxides could have a major effect on O3 concentrations in the summertime Arctic troposphere.

  4. Controls over nutrient flow through plants and microbes in Arctic tundra. Final report

    SciTech Connect

    Schimel, J.

    1994-02-01

    Ecosystem productivity in the Arctic is strongly controlled by N availability to plants. Thus, disturbances to the Arctic system are likely to have their greatest impacts by altering the supply of nutrients to plants. Thus, to understand the dynamics of Arctic tundra, a complete understanding of the controls on N cycling in tundra soils is necessary. This project focused on understanding nutrient dynamics in arctic tussock tundra, specifically evaluating the role of microbial uptake and competition for nutrients as a control on plant N-uptake. The project consisted of several major components: Short- and long-term partitioning of NH{sub 4}{sup +} in tussock tundra (1990--1991); Measurement of NH{sub 4}{sup +} uptake rates by Eriophorum vaginatum and by soil microbes; Determination of microbial NH{sub 4}{sup +} and NO{sub 3}{minus} uptake kinetics; and Determination of the partitioning of NH{sub 4}{sup +} and amino acids between E. vaginatum and soil microbes.

  5. Mat2exo

    2012-09-11

    MAT2EXO is a program which translates mesh data from Matlab mat-file format to Exodus II format. This tool is the inverse of the commonly used tool exo2mat which translates Exodus II data to the Matlab mat-file format. These tools provide a means for preprocessing an Exodus II model file or postprocessing an Exodus II results file using Matlab

  6. Gelled electrolytes for use in absorptive glass mat valve-regulated lead-acid (AGM VRLA) batteries working under 100% depth of discharge conditions

    NASA Astrophysics Data System (ADS)

    Tantichanakul, Titiporn; Chailapakul, Orawon; Tantavichet, Nisit

    2011-10-01

    Gelled electrolytes prepared from fumed silica for use in absorptive glass mat valve-regulated lead-acid (AGM VRLA) batteries and the effect of veratraldehyde addition on the electrochemical behavior and performance of AGM VRLA batteries are investigated. Cyclic voltammetry is used to investigate differences in the electrochemical behaviors of nongelled and gelled electrolytes and between gelled electrolytes with and without veratraldehyde. Battery performance is tested under 100% depth of discharge (100% DoD) conditions at both low- (0.1 C) and high- (1 C) rate discharges. The addition of silica or veratraldehyde does not affect the main reaction of the lead-acid batteries but tends to suppress the hydrogen evolution reaction. AGM VRLA batteries with gelled electrolytes have a higher discharge capacity and longer cycle life than the conventional nongel AGM VRLA batteries. The addition of 0.005% (w/v) veratraldehyde further improves battery performance, but higher (0.01%, w/v) veratraldehyde concentrations reduce it and correlate with the enhanced growth of lead sulfate crystals. The AGM VRLA battery prepared from a gelled electrolyte containing 0.005% (w/v) veratraldehyde provides the best battery performance in every operating temperature studied (0-60 °C).

  7. Microbial iron oxidation in the Arctic tundra and its implications for biogeochemical cycling.

    PubMed

    Emerson, David; Scott, Jarrod J; Benes, Joshua; Bowden, William B

    2015-12-01

    The role that neutrophilic iron-oxidizing bacteria play in the Arctic tundra is unknown. This study surveyed chemosynthetic iron-oxidizing communities at the North Slope of Alaska near Toolik Field Station (TFS) at Toolik Lake (lat 68.63, long -149.60). Microbial iron mats were common in submerged habitats with stationary or slowly flowing water, and their greatest areal extent is in coating plant stems and sediments in wet sedge meadows. Some Fe-oxidizing bacteria (FeOB) produce easily recognized sheath or stalk morphotypes that were present and dominant in all the mats we observed. The cool water temperatures (9 to 11°C) and reduced pH (5.0 to 6.6) at all sites kinetically favor microbial iron oxidation. A microbial survey of five sites based on 16S rRNA genes found a predominance of Proteobacteria, with Betaproteobacteria and members of the family Comamonadaceae being the most prevalent operational taxonomic units (OTUs). In relative abundance, clades of lithotrophic FeOB composed 5 to 10% of the communities. OTUs related to cyanobacteria and chloroplasts accounted for 3 to 25% of the communities. Oxygen profiles showed evidence for oxygenic photosynthesis at the surface of some mats, indicating the coexistence of photosynthetic and FeOB populations. The relative abundance of OTUs belonging to putative Fe-reducing bacteria (FeRB) averaged around 11% in the sampled iron mats. Mats incubated anaerobically with 10 mM acetate rapidly initiated Fe reduction, indicating that active iron cycling is likely. The prevalence of iron mats on the tundra might impact the carbon cycle through lithoautotrophic chemosynthesis, anaerobic respiration of organic carbon coupled to iron reduction, and the suppression of methanogenesis, and it potentially influences phosphorus dynamics through the adsorption of phosphorus to iron oxides. PMID:26386054

  8. Microbial Iron Oxidation in the Arctic Tundra and Its Implications for Biogeochemical Cycling

    PubMed Central

    Scott, Jarrod J.; Benes, Joshua; Bowden, William B.

    2015-01-01

    The role that neutrophilic iron-oxidizing bacteria play in the Arctic tundra is unknown. This study surveyed chemosynthetic iron-oxidizing communities at the North Slope of Alaska near Toolik Field Station (TFS) at Toolik Lake (lat 68.63, long −149.60). Microbial iron mats were common in submerged habitats with stationary or slowly flowing water, and their greatest areal extent is in coating plant stems and sediments in wet sedge meadows. Some Fe-oxidizing bacteria (FeOB) produce easily recognized sheath or stalk morphotypes that were present and dominant in all the mats we observed. The cool water temperatures (9 to 11°C) and reduced pH (5.0 to 6.6) at all sites kinetically favor microbial iron oxidation. A microbial survey of five sites based on 16S rRNA genes found a predominance of Proteobacteria, with Betaproteobacteria and members of the family Comamonadaceae being the most prevalent operational taxonomic units (OTUs). In relative abundance, clades of lithotrophic FeOB composed 5 to 10% of the communities. OTUs related to cyanobacteria and chloroplasts accounted for 3 to 25% of the communities. Oxygen profiles showed evidence for oxygenic photosynthesis at the surface of some mats, indicating the coexistence of photosynthetic and FeOB populations. The relative abundance of OTUs belonging to putative Fe-reducing bacteria (FeRB) averaged around 11% in the sampled iron mats. Mats incubated anaerobically with 10 mM acetate rapidly initiated Fe reduction, indicating that active iron cycling is likely. The prevalence of iron mats on the tundra might impact the carbon cycle through lithoautotrophic chemosynthesis, anaerobic respiration of organic carbon coupled to iron reduction, and the suppression of methanogenesis, and it potentially influences phosphorus dynamics through the adsorption of phosphorus to iron oxides. PMID:26386054

  9. Methane Suppression: The Impacts of Fe(III) and Humic Acids on Net Methane Flux from Arctic Tundra Wetlands in Alaska and Finland (Invited)

    NASA Astrophysics Data System (ADS)

    Lipson, D.; Miller, K.; Lai, C.

    2013-12-01

    Arctic soils contain large reservoirs of carbon (C) that are vulnerable to loss from climatic warming. However the potential global impacts of this C depend on whether it is lost primarily in the form of methane (CH4) or carbon dioxide (CO2), two gases with very different greenhouse warming potentials. In anaerobic environments, the relative production of CH4 vs. CO2 may be controlled by the presence of alternative terminal electron acceptors, which allow more thermodynamically favorable anaerobic respiratory pathways to dominate over methanogenesis. This work investigated how the addition of terminal electron acceptors, ferric iron (Fe(III)) and humic acids, affected net CH4 fluxes from high-latitude wetland ecosystems. We conducted two manipulative field experiments in Barrow, Alaska (71° N) and Finnish Lapland (69° N). The ecosystem in Barrow was known from previous studies to be rich in Fe(III) and to harbor a microbial community that is dominated by Fe(III)- and humic acid-reducing microorganisms. The role of these alternative electron acceptors had not previously been studied at the Finnish site. CH4 and CO2 fluxes were measured using a portable trace gas analyzer from experimental plots, before and after amendments with Fe(III) (in the chelated form, ferric nitrilotriacetic acid), humic acids, or water as a control. Both in the ecosystem with permafrost and naturally high levels of soil Fe (Barrow, AK) and in the ecosystem with no permafrost and naturally low levels of soil Fe (Petsikko, Finland), the addition of the alternative electron acceptors Fe(III) and humic acids significantly reduced net CH4 flux. CO2 fluxes were not significantly altered by the treatments. The reduction in CH4 flux persisted for at least several weeks post-treatment. There was no significant difference between the reduction caused by humic acids versus that from Fe(III). These results show that the suppression of CH4 flux by Fe(III) and humic acids is a widespread phenomenon that

  10. Microbial communities and exopolysaccharides from Polynesian mats.

    PubMed

    Rougeaux, H; Guezennec, M; Che, L M; Payri, C; Deslandes, E; Guezennec, J

    2001-03-01

    Microbial mats present in two shallow atolls of French Polynesia were characterized by high amounts of exopolysaccharides associated with cyanobacteria as the predominating species. Cyanobacteria were found in the first centimeters of the gelatinous mats, whereas deeper layers showing the occurrence of the sulfate reducers Desulfovibrio and Desulfobacter species as determined by the presence of specific biomarkers. Exopolysaccharides were extracted from these mats and partially characterized. All fractions contained both neutral sugars and uronic acids with a predominance of the former. The large diversity in monosaccharides can be interpreted as the result of exopolymer biosynthesis by either different or unidentified cyanobacterial species. PMID:14961381

  11. Changes in tundra vascular plant biomass over thirty years at Imnavait Creek, Alaska, and current ecosystem C and N dynamics.

    NASA Astrophysics Data System (ADS)

    Bret-Harte, M. S.; Shaver, G. R.; Euskirchen, E. S.; Huebner, D. C.; Drew, J. W.; Cherry, J. E.; Edgar, C.

    2015-12-01

    Understanding the magnitude of, and controls over, carbon fluxes in arctic ecosystems is essential for accurate assessment and prediction of their responses to climate change. In 2013, we harvested vegetation and soils in the most common plant community types in source areas for fluxes measured by eddy covariance towers located in three representative Alaska tundra ecosystems along a toposequence (a ridge site of heath tundra and moist non-acidic tundra, a mid-slope site of moist acidic tussock tundra, and a valley bottom site of wet sedge tundra and moist acidic tussock tundra) at Imnavait Creek, Alaska. This harvest sought to relate biomass, production, composition, and C and N stocks in soil and vegetation, to estimates of net ecosystem CO2 exchange obtained by micrometeorological methods. Soil C and N stocks in the seasonally unfrozen soil layer were greatest in the wet sedge community, and least in the heath community. In contrast, moist acidic tussock tundra at the valley bottom site had the highest C and N stocks in vascular plant biomass, while nearby wet sedge tundra had the lowest. Overall, soil C:N ratio was highest in moist acidic tussock tundra at the mid-slope site. Aboveground biomass of vascular plants in moist acidic tundra at the mid-slope site was nearly three times higher than that measured thirty years earlier in vegetation harvests of nearby areas at Imnavait Creek. Other harvests from sites near Toolik Field Station suggest that vascular plant biomass in moist acidic tundra has increased in multiple sites over this time period. Increased biomass in the mid-1990s corresponds with a switch from mostly negative to mostly positive spatially-averaged air temperature anomalies in the climate record. All our sites have been annual net sources of CO2 to the atmosphere over nine years of measurement, but in the last two years, the valley bottom site has been a particularly strong source, due to CO2 losses in fall and winter that correspond with a

  12. Absorptive glass mat separator surface modification and its influence on the heat generation in valve-regulated lead-acid battery

    NASA Astrophysics Data System (ADS)

    Drenchev, Boris; Dimitrov, Mitko; Boev, Victor; Aleksandrova, Albena

    2015-04-01

    This paper presents the results from a comparative study between two types of valve-regulated lead-acid battery cells, with uncoated and polymer composite coated absorptive glass mat (AGM) separators. The volt-ampere characteristics of the studied cells, recorded at different ambient temperatures, show that the cells with polymer coated separators have significantly lower overcharge (recombinant) current than the cells with conventional untreated AGM separator. During overcharge, the higher recombinant current in the cells with plain separator leads to higher cell temperature than that of the cells with polymer coated AGM separator. The possibility to avoid thermal runaway (TR) is also illustrated during polarization of the cells at 2.65 V. After 320 h, a conventional cell has C/4 current (trend to TR), while the cells with composite coating sustain low (C/26) constant current for long period of time (at least 650 h). The cycle life test indicates stable operation of the cells with coated separator, while the conventional cell reaches high recombinant current and thus, it is susceptible to thermal runaway phenomena.

  13. Biogeochemical modeling of tundra recovery following thermal erosion of permafrost

    NASA Astrophysics Data System (ADS)

    Pearce, A. R.; Rastetter, E. B.; Bowden, W. B.

    2011-12-01

    We simulate the biogeochemical recovery of tundra from a thermal erosion disturbance using the Multiple Element Limitation model (MEL) and compare model results with soil organic matter and nutrient chemistry measurements collected across a chronosequence of thermal erosion features. Thermal erosion of permafrost initially depletes the tundra of much of its vegetation and shallow soil organic matter. However, several decades later, there is often little distinguishing these scars from the surrounding undisturbed tundra. As thermal erosion features become more abundant on the arctic landscape, we desire to understand how the pools of carbon and nutrients rebuild after these disturbances. MEL is a plot-scale, process-based model that optimizes the acquisition of eight resources (light, water, CO2, PO4, NH4, NO3, DON and N-fixation) by vegetation based on how much of each is required and the effort needed to acquire it. Model output includes pool sizes of carbon, nitrogen and phosphorus in vegetation, litter, young soil organic matter and old soil organic matter and the fluxes among these pools over time. This calibration of MEL, operating on a daily timestep, was created with published data collected at or near the Toolik Field Station (Toolik Lake, AK, USA) from moist acidic tussock tundra sites. We corroborate our calibration with data from plot manipulations (N and P fertilization, greenhouse, and shade house) performed as part of the NSF Arctic LTER project. The initial conditions for the recovery simulations reflect post-failure observations of some of the variation in soil organic matter, and soil and water nutrient chemistry. With sufficient nutrients from residual soil or supplied in soil water from upslope, the model indicates that vegetation can recover within several decades, but recovery of C and nutrients lost from soils may take hundreds of years.

  14. Micro-hybrid electric vehicle application of valve-regulated lead-acid batteries in absorbent glass mat technology: Testing a partial-state-of-charge operation strategy

    NASA Astrophysics Data System (ADS)

    Schaeck, S.; Stoermer, A. O.; Hockgeiger, E.

    The BMW Group has launched two micro-hybrid functions in high volume models in order to contribute to reduction of fuel consumption in modern passenger cars. Both the brake energy regeneration (BER) and the auto-start-stop function (ASSF) are based on the conventional 14 V vehicle electrical system and current series components with only little modifications. An intelligent control algorithm of the alternator enables recuperative charging in braking and coasting phases, known as BER. By switching off the internal combustion engine at a vehicle standstill the idling fuel consumption is effectively reduced by ASSF. By reason of economy and package a lead-acid battery is used as electrochemical energy storage device. The BMW Group assembles valve-regulated lead-acid (VRLA) batteries in absorbent glass mat (AGM) technology in the micro-hybrid electrical power system since special challenges arise for the batteries. By field data analysis a lower average state-of-charge (SOC) due to partial state-of-charge (PSOC) operation and a higher cycling rate due to BER and ASSF are confirmed in this article. Similar to a design of experiment (DOE) like method we present a long-term lab investigation. Two types of 90 Ah VRLA AGM batteries are operated with a test bench profile that simulates the micro-hybrid vehicle electrical system under varying conditions. The main attention of this lab testing is focused on capacity loss and charge acceptance over cycle life. These effects are put into context with periodically refresh charging the batteries in order to prevent accelerated battery aging due to hard sulfation. We demonstrate the positive effect of refresh chargings concerning preservation of battery charge acceptance. Furthermore, we observe moderate capacity loss over 90 full cycles both at 25 °C and at 3 °C battery temperature.

  15. Consumption of atmospheric methane by tundra soils

    NASA Technical Reports Server (NTRS)

    Whalen, S. C.; Reeburgh, W. S.

    1990-01-01

    The results of field and laboratory experiments on methane consumption by tundra soils are reported. For methane concentrations ranging from below to well above ambient, moist soils are found to consume methane rapidly; in nonwaterlogged soils, equilibration with atmospheric methane is fast relative to microbial oxidation. It is concluded that lowering of the water table in tundra as a resulting from a warmer, drier climate will decrease methane fluxes and could cause these areas to provide negative feedback for atmospheric methane.

  16. Hypersaline Microbial Mat Lipid Biomarkers

    NASA Technical Reports Server (NTRS)

    Jahnke, Linda L.; Embaye, Tsegereda; Turk, Kendra A.; Summons, Roger E.

    2002-01-01

    Lipid biomarkers and compound specific isotopic abundances are powerful tools for studies of contemporary microbial ecosystems. Knowledge of the relationship of biomarkers to microbial physiology and community structure creates important links for understanding the nature of early organisms and paleoenvironments. Our recent work has focused on the hypersaline microbial mats in evaporation ponds at Guerrero Negro, Baja California Sur, Mexico. Specific biomarkers for diatoms, cyanobacteria, archaea, green nonsulfur (GNS), sulfate reducing, sulfur oxidizing and methanotrophic bacteria have been identified. Analyses of the ester-bound fatty acids indicate a highly diverse microbial community, dominated by photosynthetic organisms at the surface. The delta C-13 of cyanobacterial biomarkers such as the monomethylalkanes and hopanoids are consistent with the delta C-13 measured for bulk mat (-10%o), while a GNS biomarker, wax esters (WXE), suggests a more depleted delta C-13 for GNS biomass (-16%o). This isotopic relationship is different than that observed in mats at Octopus Spring, Yellowstone National Park (YSNP) where GNS appear to grow photoheterotrophic ally. WXE abundance, while relatively low, is most pronounced in an anaerobic zone just below the cyanobacterial layer. The WXE isotope composition at GN suggests that these bacteria utilize photoautotrophy incorporating dissolved inorganic carbon (DIC) via the 3-hydroxypropionate pathway using H2S or H2.

  17. Tundra Rehabilitation in Alaska's Arctic

    NASA Astrophysics Data System (ADS)

    Lynn, L. A.

    2012-12-01

    Oil exploration in Alaska's Arctic has been conducted for more than 40 years, resulting in over 3,640 ha of gravel fill placed for roads, pads, and airstrips to support the industry. Likewise, tundra disturbance from burying power lines and by tundra vehicle travel are also common. Rehabilitation of disturbed sites began around 2002, with well over 150 ha that has been previously treated or is currently being rehabilitated. Two primary goals of rehabilitation efforts have been 1) revegetation by indigenous species, and 2) limiting thermokarst. Early efforts were concerned that removing gravel and having exposed bare ground would lead to extensive subsidence and eolian erosion. Native grass cultivars (e.g. Poa glauca, Arctagrostis latifolia, and Festuca rubra) were seeded to create vegetation cover quickly with the expectation that these grasses would survive only temporarily. The root masses and leaf litter were also expected to trap indigenous seed to enhance natural recolonization by indigenous plants. Due to the remote location of these sites, many of which are only accessible by helicopter, most are visited only two to three times following cultivation treatments, providing a limited data pool. At many sites, the total live seeded grass cover declined about 15% over the first 5¬-6 years (from around 30% to 15% cover), while total live indigenous vascular cover increased from no or trace cover to an average of 10% cover in that time. Cover of indigenous vascular plants at sites that were not seeded with native grass cultivars averaged just less than 10% after 10 years, showing no appreciable difference between the two approaches. Final surface elevations at the sites affect local hydrology and soil moisture. Other factors that influence the success of vegetation cover are proximity to the Arctic coast (salt effects), depth of remaining gravel, and changes in characteristics of the near-surface soil. Further development of rehabilitation techniques and the

  18. ProMat

    2008-06-12

    ProMAT is a software tool for statistically analyzing data from enzyme-linked immunosorbent assay microarray experiments. The software estimates standard curves, sample protein concentrations and their uncertainties for multiple assays. ProMAT generates a set of comprehensive figures for assessing results and diagnosing process quality. The tool is available for Windows or Mac, and is distributed as open-source Java and R code

  19. Contexts for change in alpine tundra

    USGS Publications Warehouse

    Malanson, George P.; Rose, Jonathan P.; Schroeder, P. Jason; Fagre, Daniel B.

    2011-01-01

    Because alpine tundra is responding to climate change, a need exists to understand the meaning of observed changes. To provide context for such interpretation, the relevance of niche and neutral theories of biogeography and the continuum and classification approaches to biogeographic description are assessed. Two extensive studies of alpine tundra, from the Indian Peaks area, Colorado and Glacier National Park, Montana, are combined. The data are ordinated to describe relations. The pattern that emerges is one of a continuum of vegetation, but with the distinctions one might expect from distant sites. The relationships of the similarity of vegetation on all possible pairs of sites to the environmental differences and geographic distances are analyzed using Mantel correlations. Because distance and environmental differences in climate between the two sites are correlated, partial correlations are weak but still significant. More advanced analyses are suggested for this environment prior to interpretation of monitoring efforts such as GLORIA.

  20. Geochemical drivers of organic matter decomposition in Arctic tundra soils

    DOE PAGESBeta

    Herndon, Elizabeth M.; Yang, Ziming; Graham, David E.; Wullschleger, Stan D.; Gu, Baohua; Liang, Liyuan; Bargar, John; Janot, Noemie; Regier, Tom Z.

    2015-12-07

    Climate change is warming tundra ecosystems in the Arctic, resulting in the decomposition of previously-frozen soil organic matter (SOM) and release of carbon (C) to the atmosphere; however, the processes that control SOM decomposition and C emissions remain highly uncertain. In this study, we evaluate geochemical factors that influence anaerobic production of carbon dioxide (CO2) and methane (CH4) in the active layers of four ice-wedge polygons. Surface and soil pore waters were collected during the annual thaw season over a two-year period in an area containing waterlogged, low-centered polygons and well-drained, high-centered polygons. We report spatial and seasonal patterns ofmore » dissolved gases in relation to the geochemical properties of Fe and organic C as determined using spectroscopic and chromatographic techniques. Iron was present as Fe(II) in soil solution near the permafrost boundary but enriched as Fe(III) in the middle of the active layer, similar to dissolved aromatic-C and organic acids. Dissolved CH4 increased relative to dissolved CO2 with depth and varied with soil moisture in the middle of the active layer in patterns that were positively correlated with the proportion of dissolved Fe(III) in transitional and low-centered polygon soils but negatively correlated in the drier flat- and high-centered polygons. These results suggest that microbial-mediated Fe oxidation and reduction influence respiration/fermentation of SOM and production of substrates (e.g., low-molecular-weight organic acids) for methanogenesis. As a result, we infer that geochemical differences induced by water saturation dictate microbial products of SOM decomposition, and Fe geochemistry is an important factor regulating methanogenesis in anoxic tundra soils.« less

  1. Geochemical drivers of organic matter decomposition in Arctic tundra soils

    SciTech Connect

    Herndon, Elizabeth M.; Yang, Ziming; Graham, David E.; Wullschleger, Stan D.; Gu, Baohua; Liang, Liyuan; Bargar, John; Janot, Noemie; Regier, Tom Z.

    2015-12-07

    Climate change is warming tundra ecosystems in the Arctic, resulting in the decomposition of previously-frozen soil organic matter (SOM) and release of carbon (C) to the atmosphere; however, the processes that control SOM decomposition and C emissions remain highly uncertain. In this study, we evaluate geochemical factors that influence anaerobic production of carbon dioxide (CO2) and methane (CH4) in the active layers of four ice-wedge polygons. Surface and soil pore waters were collected during the annual thaw season over a two-year period in an area containing waterlogged, low-centered polygons and well-drained, high-centered polygons. We report spatial and seasonal patterns of dissolved gases in relation to the geochemical properties of Fe and organic C as determined using spectroscopic and chromatographic techniques. Iron was present as Fe(II) in soil solution near the permafrost boundary but enriched as Fe(III) in the middle of the active layer, similar to dissolved aromatic-C and organic acids. Dissolved CH4 increased relative to dissolved CO2 with depth and varied with soil moisture in the middle of the active layer in patterns that were positively correlated with the proportion of dissolved Fe(III) in transitional and low-centered polygon soils but negatively correlated in the drier flat- and high-centered polygons. These results suggest that microbial-mediated Fe oxidation and reduction influence respiration/fermentation of SOM and production of substrates (e.g., low-molecular-weight organic acids) for methanogenesis. As a result, we infer that geochemical differences induced by water saturation dictate microbial products of SOM decomposition, and Fe geochemistry is an important factor regulating methanogenesis in anoxic tundra soils.

  2. The unseen iceberg: Plant roots in arctic tundra

    USGS Publications Warehouse

    Iverson, Colleen M.; Sloan, Victoria L.; Sullivan, Patrick F.; Euskirchen, E.S.; McGuire, Anthony; Norby, Richard J.; Walker, Anthony P.; Warren, Jeffrey M.; Wullschleger, Stan D.

    2015-01-01

    Plant roots play a critical role in ecosystem function in arctic tundra, but root dynamics in these ecosystems are poorly understood. To address this knowledge gap, we synthesized available literature on tundra roots, including their distribution, dynamics and contribution to ecosystem carbon and nutrient fluxes, and highlighted key aspects of their representation in terrestrial biosphere models. Across all tundra ecosystems, belowground plant biomass exceeded aboveground biomass, with the exception of polar desert tundra. Roots were shallowly distributed in the thin layer of soil that thaws annually, and were often found in surface organic soil horizons. Root traits – including distribution, chemistry, anatomy and resource partitioning – play an important role in controlling plant species competition, and therefore ecosystem carbon and nutrient fluxes, under changing climatic conditions, but have only been quantified for a small fraction of tundra plants. Further, the annual production and mortality of fine roots are key components of ecosystem processes in tundra, but extant data are sparse. Tundra root traits and dynamics should be the focus of future research efforts. Better representation of the dynamics and characteristics of tundra roots will improve the utility of models for the evaluation of the responses of tundra ecosystems to changing environmental conditions.

  3. Pathways of anaerobic organic matter decomposition in tundra soils from Barrow, Alaska

    DOE PAGESBeta

    Herndon, Elizabeth M.; Mann, Benjamin F.; Chowdhury, Taniya Roy; Wullschleger, Stan D.; Graham, David E.; Liang, Liyuan; Gu, Baohua; Yang, Ziming

    2015-11-23

    Arctic tundra soils store a large quantity of organic carbon that is susceptible to decomposition and release to the atmosphere as methane (CH4) and carbon dioxide (CO2) under a warming climate. Anaerobic processes that generate CH4 and CO2 remain unclear because previous studies have focused on aerobic decomposition pathways. To predict releases of CO2 and CH4 from tundra soils, it is necessary to identify pathways of soil organic matter decomposition under the anoxic conditions that are prevalent in Arctic ecosystems. Here molecular and spectroscopic techniques were used to monitor biological degradation of water-extractable organic carbon (WEOC) during anoxic incubation ofmore » tundra soils from a region of continuous permafrost in northern Alaska. Organic and mineral soils from the tundra active layer were incubated at –2, +4, or +8°C for up to 60 days to mimic the short-term thaw season. Results suggest that, under anoxic conditions, fermentation converted complex organic molecules into simple organic acids that were used in concomitant Fe-reduction and acetoclastic methanogenesis reactions. Nonaromatic compounds increased over time as WEOC increased. Organic acid metabolites initially accumulated in soils but were mostly depleted by day 60 because organic acids were consumed to produce Fe(II), CO2, and CH4. We conclude that fermentation of nonprotected organic matter facilitates methanogenesis and Fe reduction reactions, and that the proportion of organic acids consumed by methanogenesis increases relative to Fe reduction with increasing temperature. As a result, the decomposition pathways observed in this study are important to consider in numerical modeling of greenhouse gas production in the Arctic.« less

  4. Pathways of anaerobic organic matter decomposition in tundra soils from Barrow, Alaska

    SciTech Connect

    Herndon, Elizabeth M.; Mann, Benjamin F.; Chowdhury, Taniya Roy; Wullschleger, Stan D.; Graham, David E.; Liang, Liyuan; Gu, Baohua; Yang, Ziming

    2015-11-23

    Arctic tundra soils store a large quantity of organic carbon that is susceptible to decomposition and release to the atmosphere as methane (CH4) and carbon dioxide (CO2) under a warming climate. Anaerobic processes that generate CH4 and CO2 remain unclear because previous studies have focused on aerobic decomposition pathways. To predict releases of CO2 and CH4 from tundra soils, it is necessary to identify pathways of soil organic matter decomposition under the anoxic conditions that are prevalent in Arctic ecosystems. Here molecular and spectroscopic techniques were used to monitor biological degradation of water-extractable organic carbon (WEOC) during anoxic incubation of tundra soils from a region of continuous permafrost in northern Alaska. Organic and mineral soils from the tundra active layer were incubated at –2, +4, or +8°C for up to 60 days to mimic the short-term thaw season. Results suggest that, under anoxic conditions, fermentation converted complex organic molecules into simple organic acids that were used in concomitant Fe-reduction and acetoclastic methanogenesis reactions. Nonaromatic compounds increased over time as WEOC increased. Organic acid metabolites initially accumulated in soils but were mostly depleted by day 60 because organic acids were consumed to produce Fe(II), CO2, and CH4. We conclude that fermentation of nonprotected organic matter facilitates methanogenesis and Fe reduction reactions, and that the proportion of organic acids consumed by methanogenesis increases relative to Fe reduction with increasing temperature. As a result, the decomposition pathways observed in this study are important to consider in numerical modeling of greenhouse gas production in the Arctic.

  5. Pathways of anaerobic organic matter decomposition in tundra soils from Barrow, Alaska

    NASA Astrophysics Data System (ADS)

    Herndon, Elizabeth M.; Mann, Benjamin F.; Roy Chowdhury, Taniya; Yang, Ziming; Wullschleger, Stan D.; Graham, David; Liang, Liyuan; Gu, Baohua

    2015-11-01

    Arctic tundra soils store a large quantity of organic carbon that is susceptible to decomposition and release to the atmosphere as methane (CH4) and carbon dioxide (CO2) under a warming climate. Anaerobic processes that generate CH4 and CO2 remain unclear because previous studies have focused on aerobic decomposition pathways. To predict releases of CO2 and CH4 from tundra soils, it is necessary to identify pathways of soil organic matter decomposition under the anoxic conditions that are prevalent in Arctic ecosystems. Here molecular and spectroscopic techniques were used to monitor biological degradation of water-extractable organic carbon (WEOC) during anoxic incubation of tundra soils from a region of continuous permafrost in northern Alaska. Organic and mineral soils from the tundra active layer were incubated at -2, +4, or +8°C for up to 60 days to mimic the short-term thaw season. Results suggest that, under anoxic conditions, fermentation converted complex organic molecules into simple organic acids that were used in concomitant Fe-reduction and acetoclastic methanogenesis reactions. Nonaromatic compounds increased over time as WEOC increased. Organic acid metabolites initially accumulated in soils but were mostly depleted by day 60 because organic acids were consumed to produce Fe(II), CO2, and CH4. We conclude that fermentation of nonprotected organic matter facilitates methanogenesis and Fe reduction reactions, and that the proportion of organic acids consumed by methanogenesis increases relative to Fe reduction with increasing temperature. The decomposition pathways observed in this study are important to consider in numerical modeling of greenhouse gas production in the Arctic.

  6. MILLIMETER-SCALE GENETIC GRADIENTS AND COMMUNITY-LEVEL MOLECULAR CONVERGENCE IN A HYPERSALINE MICROBIAL MAT

    SciTech Connect

    Fenner, Marsha W; Kunin, Victor; Raes, Jeroen; Harris, J. Kirk; Spear, John R.; Walker, Jeffrey J.; Ivanova, Natalia; Mering, Christian von; Bebout, Brad M.; Pace, Norman R.; Bork, Peer; Hugenholtz, Philip

    2008-04-30

    To investigate the extent of genetic stratification in structured microbial communities, we compared the metagenomes of 10 successive layers of a phylogenetically complex hypersaline mat from Guerrero Negro, Mexico. We found pronounced millimeter-scale genetic gradients that are consistent with the physicochemical profile of the mat. Despite these gradients, all layers displayed near identical and acid-shifted isoelectric point profiles due to a molecular convergence of amino acid usage indicating that hypersalinity enforces an overriding selective pressure on the mat community.

  7. THE ROLE OF THERMAL REGIMEN IN TUNDRA PLANT COMMUNITY RESTORATION

    EPA Science Inventory

    Mineral extraction activities in the Arctic regions of the world produce long-lasting ecological disturbances. Assisted recovery from such disturbances may require restoration of the tundra thermal regime. We transplanted plugs of entire root zone and live tundra plants to a dist...

  8. Intense, natural pollution affects Arctic tundra vegetation at the Smoking Hills, Canada

    SciTech Connect

    Freedman, B. ); Zobens, V.; Hutchinson, T.C.; Gizyn, W.I. )

    1990-04-01

    Long-term, natural emissions of sulfur dioxide and acidic aerosols have had an impact on remote tundra at the Smoking Hills. The emissions have caused plant damage by SO{sub 2} toxicity, and have severely acidified soil and freshwater. At the most intensively fumigated locations closest to the sources of emission, pollution stresses have devegetated the terrestrial ecosystem. The first plants that are encountered along a spatial gradient of decreasing pollution stress are Artemisia tilesii and Arctagrostis latifolia, which dominate a characteristic, pollution-tolerant community. Farther away at moderately polluted sites there are mixed communities with floristic elements of both fumigated and reference, unfumigated tundra. This pattern of ecosystem response to a concatenation of stresses caused by natural air and soil pollution is qualitatively similar to the damage that occurs in the vicinity of anthropogenic point sources of air pollution, such as smelters.

  9. Soil bacterial community composition altered by increased nutrient availability in Arctic tundra soils

    PubMed Central

    Koyama, Akihiro; Wallenstein, Matthew D.; Simpson, Rodney T.; Moore, John C.

    2014-01-01

    The pool of soil organic carbon (SOC) in the Arctic is disproportionally large compared to those in other biomes. This large quantity of SOC accumulated over millennia due to slow rates of decomposition relative to net primary productivity. Decomposition is constrained by low temperatures and nutrient concentrations, which limit soil microbial activity. We investigated how nutrients limit bacterial and fungal biomass and community composition in organic and mineral soils within moist acidic tussock tundra ecosystems. We sampled two experimental arrays of moist acidic tussock tundra that included fertilized and non-fertilized control plots. One array included plots that had been fertilized annually since 1989 and the other since 2006. Fertilization significantly altered overall bacterial community composition and reduced evenness, to a greater degree in organic than mineral soils, and in the 1989 compared to the 2006 site. The relative abundance of copiotrophic α-Proteobacteria and β-Proteobacteria was higher in fertilized than control soils, and oligotrophic Acidobacteria were less abundant in fertilized than control soils at the 1989 site. Fungal community composition was less sensitive to increased nutrient availability, and fungal responses to fertilization were not consistent between soil horizons and sites. We detected two ectomycorrhizal genera, Russula and Cortinarius spp., associated with shrubs. Their relative abundance was not affected by fertilization despite increased dominance of their host plants in the fertilized plots. Our results indicate that fertilization, which has been commonly used to simulate warming in Arctic tundra, has limited applicability for investigating fungal dynamics under warming. PMID:25324836

  10. Compositions of constructed microbial mats

    DOEpatents

    Bender, Judith A.; Phillips, Peter C.

    1999-01-01

    Compositions and methods of use of constructed microbial mats, comprising cyanobacteria and purple autotrophic bacteria and an organic nutrient source, in a laminated structure, are described. The constructed microbial mat is used for bioremediation of different individual contaminants and for mixed or multiple contaminants, and for production of beneficial compositions and molecules.

  11. M.A.T. Programs.

    ERIC Educational Resources Information Center

    Wildman, Louis

    A proposal is presented for developing a Master of Arts in Teaching (MAT) program at California State University, Bakersfield. The criteria for a MAT program are examined by outlining existing programs at: (1) Harvard Graduate School; (2) University of California, Berkeley; (3) Portland State University; (4) Stanford University; (5) University of…

  12. MueMat Multicrid Toolbox

    SciTech Connect

    2010-11-23

    MueMat is intended for the research and development of multigrid algorithms used in the solution of sparse linear systems arising from systems of partial differential equations. The software can generate example linear systems and provides short programs to demonstrate the various interfaces for creating, accessing, and applying the solvers. MueMat currently includes two types of algebraic multigrid methods and many commonly used smoothers. However, the software is intended to be extensible, and new methods can be incorporated easily. MueMat also allows for advanced usage, such as combining multiple methods and segregated solves. The library supports point and block access to matrix data. MueMat has been designed for use within the programming environment of the Mathworks program MATLAB®. All algorithms and methods in MueMat have been or will be published in the open scientific literature.

  13. MueMat Multicrid Toolbox

    2010-11-23

    MueMat is intended for the research and development of multigrid algorithms used in the solution of sparse linear systems arising from systems of partial differential equations. The software can generate example linear systems and provides short programs to demonstrate the various interfaces for creating, accessing, and applying the solvers. MueMat currently includes two types of algebraic multigrid methods and many commonly used smoothers. However, the software is intended to be extensible, and new methods canmore » be incorporated easily. MueMat also allows for advanced usage, such as combining multiple methods and segregated solves. The library supports point and block access to matrix data. MueMat has been designed for use within the programming environment of the Mathworks program MATLAB®. All algorithms and methods in MueMat have been or will be published in the open scientific literature.« less

  14. Nitrogen mineralization in a tussock tundra soil

    SciTech Connect

    Marion, G.M.; Miller, P.C.

    1982-01-01

    The effects of substrate quality, temperature, and moisture on nitrogen mineralization from a tussock tundra soil were examined with laboratory soil incubations utilizing both air-dried samples and field-moist intact cores. The potentially mineralizable nitrogen (PMN) was highly correlated to both total soil nitrogen (positively) and the carbon/nitrogen ratio (negatively). All soil horizons exhibited a net nitrogen mineralization even at a high carbon/nitrogen ratio of 92. It was concluded that field-moist intact soil cores provide a more reliable estimate than the air-dried samples of both PMN and the mineralization rate under standard laboratory conditions. There was no significant effect of moisture tension (0.0 to 0.4 bars) on net nitrogen mineralization. The average Q/sub 10/ (temperature effect) for net nitrogen mineralization was 2.5. Based on this study and others, it was concluded that temperature through its effect on nitrogen mineralization plays an important role in controlling plant productivity in these naturally nitrogen-deficient tundra ecosystems.

  15. Recent Arctic tundra fire initiates widespread thermokarst development.

    PubMed

    Jones, Benjamin M; Grosse, Guido; Arp, Christopher D; Miller, Eric; Liu, Lin; Hayes, Daniel J; Larsen, Christopher F

    2015-01-01

    Fire-induced permafrost degradation is well documented in boreal forests, but the role of fires in initiating thermokarst development in Arctic tundra is less well understood. Here we show that Arctic tundra fires may induce widespread thaw subsidence of permafrost terrain in the first seven years following the disturbance. Quantitative analysis of airborne LiDAR data acquired two and seven years post-fire, detected permafrost thaw subsidence across 34% of the burned tundra area studied, compared to less than 1% in similar undisturbed, ice-rich tundra terrain units. The variability in thermokarst development appears to be influenced by the interaction of tundra fire burn severity and near-surface, ground-ice content. Subsidence was greatest in severely burned, ice-rich upland terrain (yedoma), accounting for ~50% of the detected subsidence, despite representing only 30% of the fire disturbed study area. Microtopography increased by 340% in this terrain unit as a result of ice wedge degradation. Increases in the frequency, magnitude, and severity of tundra fires will contribute to future thermokarst development and associated landscape change in Arctic tundra regions. PMID:26511650

  16. Recent Arctic tundra fire initiates widespread thermokarst development

    PubMed Central

    Jones, Benjamin M.; Grosse, Guido; Arp, Christopher D.; Miller, Eric; Liu, Lin; Hayes, Daniel J.; Larsen, Christopher F.

    2015-01-01

    Fire-induced permafrost degradation is well documented in boreal forests, but the role of fires in initiating thermokarst development in Arctic tundra is less well understood. Here we show that Arctic tundra fires may induce widespread thaw subsidence of permafrost terrain in the first seven years following the disturbance. Quantitative analysis of airborne LiDAR data acquired two and seven years post-fire, detected permafrost thaw subsidence across 34% of the burned tundra area studied, compared to less than 1% in similar undisturbed, ice-rich tundra terrain units. The variability in thermokarst development appears to be influenced by the interaction of tundra fire burn severity and near-surface, ground-ice content. Subsidence was greatest in severely burned, ice-rich upland terrain (yedoma), accounting for ~50% of the detected subsidence, despite representing only 30% of the fire disturbed study area. Microtopography increased by 340% in this terrain unit as a result of ice wedge degradation. Increases in the frequency, magnitude, and severity of tundra fires will contribute to future thermokarst development and associated landscape change in Arctic tundra regions. PMID:26511650

  17. Evidence and Implications of Frequent Fires in Ancient Shrub Tundra

    SciTech Connect

    Higuera, P E; Brubaker, L B; Anderson, P M; Brown, T A; Kennedy, A T; Hu, F S

    2008-03-06

    Understanding feedbacks between terrestrial and atmospheric systems is vital for predicting the consequences of global change, particularly in the rapidly changing Arctic. Fire is a key process in this context, but the consequences of altered fire regimes in tundra ecosystems are rarely considered, largely because tundra fires occur infrequently on the modern landscape. We present paleoecological data that indicate frequent tundra fires in northcentral Alaska between 14,000 and 10,000 years ago. Charcoal and pollen from lake sediments reveal that ancient birchdominated shrub tundra burned as often as modern boreal forests in the region, every 144 years on average (+/- 90 s.d.; n = 44). Although paleoclimate interpretations and data from modern tundra fires suggest that increased burning was aided by low effective moisture, vegetation cover clearly played a critical role in facilitating the paleo-fires by creating an abundance of fine fuels. These records suggest that greater fire activity will likely accompany temperature-related increases in shrub-dominated tundra predicted for the 21st century and beyond. Increased tundra burning will have broad impacts on physical and biological systems as well as land-atmosphere interactions in the Arctic, including the potential to release stored organic carbon to the atmosphere.

  18. The unseen iceberg: Plant roots in arctic tundra

    DOE PAGESBeta

    Iversen, Colleen M; Sloan, Victoria L; Sullivan, Patrick F.; Euskirchen, Eugenie S; McGuire, A. David; Norby, Richard J; Walker, Anthony P; Warren, Jeffrey; Wullschleger, Stan D

    2015-01-01

    Arctic tundra is characterized by short-statured plant communities underlain by carbon (C)-rich soils and permafrost. Ecosystem C and nutrient cycles in tundra are driven by complex interactions between plants and their environment. However, root dynamics are one of the least understood aspects of plant growth in the Arctic. We synthesized available literature on tundra roots and discussed their representation in terrestrial biosphere models. Belowground biomass in tundra ecosystems can be an order of magnitude larger than aboveground biomass. Data on root production and turnover in tundra is sparse, limiting our understanding of the controls over root dynamics in these systems.more » Roots are shallowly distributed in the thin layer of soil that thaws each year, and are often found in the organic horizon at the soil surface. Species-specific differences in root distribution, mycorrhizal colonization, and resource partitioning may affect plant species competition under changing climatic conditions. Model representation of belowground processes has increased in complexity over recent years, but data are desperately needed to fill the gaps in model treatment of tundra roots. Future research should focus on estimates of root production and lifespan, and interactions between roots and the surrounding soil across the diversity of tundra ecosystems in the Arctic.« less

  19. The unseen iceberg: Plant roots in arctic tundra

    SciTech Connect

    Iversen, Colleen M; Sloan, Victoria L; Sullivan, Patrick F.; Euskirchen, Eugenie S; McGuire, A. David; Norby, Richard J; Walker, Anthony P; Warren, Jeffrey; Wullschleger, Stan D

    2015-01-01

    Arctic tundra is characterized by short-statured plant communities underlain by carbon (C)-rich soils and permafrost. Ecosystem C and nutrient cycles in tundra are driven by complex interactions between plants and their environment. However, root dynamics are one of the least understood aspects of plant growth in the Arctic. We synthesized available literature on tundra roots and discussed their representation in terrestrial biosphere models. Belowground biomass in tundra ecosystems can be an order of magnitude larger than aboveground biomass. Data on root production and turnover in tundra is sparse, limiting our understanding of the controls over root dynamics in these systems. Roots are shallowly distributed in the thin layer of soil that thaws each year, and are often found in the organic horizon at the soil surface. Species-specific differences in root distribution, mycorrhizal colonization, and resource partitioning may affect plant species competition under changing climatic conditions. Model representation of belowground processes has increased in complexity over recent years, but data are desperately needed to fill the gaps in model treatment of tundra roots. Future research should focus on estimates of root production and lifespan, and interactions between roots and the surrounding soil across the diversity of tundra ecosystems in the Arctic.

  20. Willow Shrub Expansion Following Tundra Fires in Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Racine, C.

    2010-12-01

    Climate warming in the Arctic is predicted to result in the expansion of woody shrubs and increased frequency and size of tundra fires. How will fire influence this shrub expansion? Over a period of 32 years, following a 1977 tundra fire in the central Seward Peninsula, we sampled seven times the post-fire vegetation at eight permanently marked sites on a long (2 Km) hillslope (Nimrod Hill). We had previously sampled vegetation here in 1973 prior to the fire. By 2001, 24 years post-fire conspicuous willow shrubs (mostly Salix pulchra) had increased in numbers, size and cover over the entire slope in moist tussock-shrub tundra, well-drained heath, and wet meadow. Prior to fire, willow on this slope was largely restricted to small drainages or watertracks. Willows here have originated from both seed and vegetative resprouting - the latter mostly in moist tussock-shrub tundra from willows resprouting within one to three years post-fire. With fire-induced removal of vascular plant competition and Spagnum moss cover and litter in tussock-shrub tundra, both seedling and resprouting willows have grown rapidly to overtop tussocks by 30-40 cm. Similar rapid post-fire resprouting of willows has been observed in tussock-shrub tundra after the 2007 Anaktuvuk River tundra fire and after the 1977 tundra fires in the Noatak River basin. On Nimrod Hill the most striking willow expansion has occurred on the severely burned and well-drained backslope where willow establishment from seed 5-10 years after fire has resulted in up to 40% cover of rapidly growing willows of both upright and spreading growth form. At several sites along the slope there is evidence of continuing willow expansion from seedlings 24 to 32 years post-fire, when we might expect the effects of fire on seedbeds would have ceased. We conclude that tundra fire may promote shrub expansion in the Arctic.

  1. Molecular cloning and expression analysis of MAT1 gene in black tiger shrimp (Penaeus monodon).

    PubMed

    Wang, Y; Fu, M J; Zhao, C; Bao, W Y; Zhou, F L; Yang, Q B; Jiang, S G; Qiu, L H

    2016-01-01

    MAT1 (ménage à trois 1), an assembly factor and targeting subunit of the CDK-dependent kinase (CAK), can regulate the cell cycle, transcription, and DNA repair. This study was intended to investigate the role of MAT1 in the reproductive maturation of black tiger shrimp (Penaeus monodon). In this study, the P. monodon MAT1 (PmMAT1) gene was identified and characterized. The full-length cDNA of PmMAT1 was 1490 bp in length with an open-reading frame of 993 bp corresponding to 330 amino acids. The temporal expression of PmMAT1 in various tissues was measured by quantitative real-time PCR with the highest expression observed in ovaries. In the ovaries, the PmMAT1 gene was continuously but differentially expressed during the maturation stages. Comparative analyses of MAT1, CDK7, and cyclin H in the CAK complex of P. monodon indicated that the expression of CDK7 and cyclin H coincided with that of MAT1 during the ovary maturation stages. Serotonin (5-HT) injection promoted the expression level of PmMAT1 in the ovaries of shrimp at 6-48 h post-injection. These results indicate that PmMat1 plays a prominent role in the process of ovarian maturation. PMID:26909956

  2. Electrospun chitosan-based nanofiber mats loaded with Garcinia mangostana extracts.

    PubMed

    Charernsriwilaiwat, Natthan; Rojanarata, Theerasak; Ngawhirunpat, Tanasait; Sukma, Monrudee; Opanasopit, Praneet

    2013-08-16

    The aim of this study was to prepare electrospun chitosan-based nanofiber mats and to incorporate the fruit hull of Garcinia mangostana (GM) extracts into the mats. Chitosan-ethylenediaminetetraacetic acid/polyvinyl alcohol (CS-EDTA/PVA) was selected as the polymers. The GM extracts with 1, 2 and 3 wt% α-mangostin were incorporated into the CS-EDTA/PVA solution and electrospun to obtain nanofibers. The morphology and diameters of the mats were analyzed using scanning electron microscopy (SEM). The mechanical and swelling properties were investigated. The amount of GM extracts was determined using high-performance liquid chromatography (HPLC). The antioxidative activity, antibacterial activity, extract release and stability of the mats were evaluated. In vivo wound healing tests were also performed in Wistar rats. The results indicated that the diameters of the fibers were on the nanoscale and that no crystals of the extract were observed in the mats at any concentration. The mats provided suitable tensile strength and swelling properties. All of the mats exhibited antioxidant and antibacterial activity. During the wound healing test, the mats accelerated the rate of healing when compared to the control (gauze-covered). The mats maintained 90% of their content of α-mangostin for 3 months. In conclusion, the chitosan-based nanofiber mats loaded with GM extracts were successfully prepared using the electrospinning method. These nanofiber mats loaded with GM extracts may provide a good alternative for accelerating wound healing. PMID:23680732

  3. A field operational test on valve-regulated lead-acid absorbent-glass-mat batteries in micro-hybrid electric vehicles. Part I. Results based on kernel density estimation

    NASA Astrophysics Data System (ADS)

    Schaeck, S.; Karspeck, T.; Ott, C.; Weckler, M.; Stoermer, A. O.

    2011-03-01

    In March 2007 the BMW Group has launched the micro-hybrid functions brake energy regeneration (BER) and automatic start and stop function (ASSF). Valve-regulated lead-acid (VRLA) batteries in absorbent glass mat (AGM) technology are applied in vehicles with micro-hybrid power system (MHPS). In both part I and part II of this publication vehicles with MHPS and AGM batteries are subject to a field operational test (FOT). Test vehicles with conventional power system (CPS) and flooded batteries were used as a reference. In the FOT sample batteries were mounted several times and electrically tested in the laboratory intermediately. Vehicle- and battery-related diagnosis data were read out for each test run and were matched with laboratory data in a data base. The FOT data were analyzed by the use of two-dimensional, nonparametric kernel estimation for clear data presentation. The data show that capacity loss in the MHPS is comparable to the CPS. However, the influence of mileage performance, which cannot be separated, suggests that battery stress is enhanced in the MHPS although a battery refresh function is applied. Anyway, the FOT demonstrates the unsuitability of flooded batteries for the MHPS because of high early capacity loss due to acid stratification and because of vanishing cranking performance due to increasing internal resistance. Furthermore, the lack of dynamic charge acceptance for high energy regeneration efficiency is illustrated. Under the presented FOT conditions charge acceptance of lead-acid (LA) batteries decreases to less than one third for about half of the sample batteries compared to new battery condition. In part II of this publication FOT data are presented by multiple regression analysis (Schaeck et al., submitted for publication [1]).

  4. 8. DETAIL OF QUONSET HUT SHOWING BOARDWALK ON TUNDRA CONNECTING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. DETAIL OF QUONSET HUT SHOWING BOARDWALK ON TUNDRA CONNECTING QUONSET HUTS THAT DID NOT HAVE INTERCONNNECTING WOOD FRAME CORRIDORS - Fort Randall, Neuro-Psychiatric Ward, Northeast of intersection of California Boulevard & Nurse Drive, Cold Bay, Aleutian Islands, AK

  5. A field operational test on valve-regulated lead-acid absorbent-glass-mat batteries in micro-hybrid electric vehicles. Part II. Results based on multiple regression analysis and tear-down analysis

    NASA Astrophysics Data System (ADS)

    Schaeck, S.; Karspeck, T.; Ott, C.; Weirather-Koestner, D.; Stoermer, A. O.

    2011-03-01

    In the first part of this work [1] a field operational test (FOT) on micro-HEVs (hybrid electric vehicles) and conventional vehicles was introduced. Valve-regulated lead-acid (VRLA) batteries in absorbent glass mat (AGM) technology and flooded batteries were applied. The FOT data were analyzed by kernel density estimation. In this publication multiple regression analysis is applied to the same data. Square regression models without interdependencies are used. Hereby, capacity loss serves as dependent parameter and several battery-related and vehicle-related parameters as independent variables. Battery temperature is found to be the most critical parameter. It is proven that flooded batteries operated in the conventional power system (CPS) degrade faster than VRLA-AGM batteries in the micro-hybrid power system (MHPS). A smaller number of FOT batteries were applied in a vehicle-assigned test design where the test battery is repeatedly mounted in a unique test vehicle. Thus, vehicle category and specific driving profiles can be taken into account in multiple regression. Both parameters have only secondary influence on battery degradation, instead, extended vehicle rest time linked to low mileage performance is more serious. A tear-down analysis was accomplished for selected VRLA-AGM batteries operated in the MHPS. Clear indications are found that pSoC-operation with periodically fully charging the battery (refresh charging) does not result in sulphation of the negative electrode. Instead, the batteries show corrosion of the positive grids and weak adhesion of the positive active mass.

  6. Capillography of Mats of Nanofibers

    NASA Technical Reports Server (NTRS)

    Noca, Flavio; Sansom, Elijah; Zhou, Jijie; Gharib, Mory

    2008-01-01

    Capillography (from the Latin capillus, 'hair', and the Greek graphein, to write ) is a recently conceived technique for forming mats of nanofibers into useful patterns. The concept was inspired by experiments on carpetlike mats of multiwalled carbon nanotubes. Capillography may have the potential to be a less-expensive, less-time-consuming alternative to electron-beam lithography as a means of nanoscale patterning for the fabrication of small devices and instruments. In capillography, one exploits the lateral capillary forces exerted on small objects that pierce the surface of a liquid. If the small objects are identical, then the forces are always attractive. Two examples of the effects of such forces are the agglomeration of small particles floating on the surface of a pond and the drawing together of hairs of a wet paintbrush upon removal of the brush from water. Because nanoscale objects brought into contact remain stuck together indefinitely due to Van der Waals forces, patterns formed by capillography remain even upon removal of the liquid. For the experiments on the mats of carbon nanotubes, a surfactant solution capable of wetting carbon nanotubes (which are ultra-hydrophobic) was prepared. The mats were wetted with the solution, then dried. Once the mats were dry, it was found that the nanotubes had become ordered into various patterns, including nestlike indentations, trenches, and various combinations thereof. It may be possible to exploit such ordering effects through controlled wetting and drying of designated portions of mats of carbon nanotubes (and, perhaps, mats of nanofibers of other materials) to obtain patterns similar to those heretofore formed by use of electron-beam lithography. For making patterns that include nestlike indentations, it has been conjectured that it could be possible to control the nesting processes by use of electrostatic fields. Further research is needed to understand the physics of the patterning processes in order to

  7. Above and below ground carbon stocks in northeast Siberia tundra ecosystems: a comparison between disturbed and undisturbed areas

    NASA Astrophysics Data System (ADS)

    Weber, L. R.; Pena, H., III; Curasi, S. R.; Ramos, E.; Loranty, M. M.; Alexander, H. D.; Natali, S.

    2014-12-01

    Changes in arctic tundra vegetation have the potential to alter the regional carbon (C) budget, with feedback implications for global climate. A number of studies have documented both widespread increases in productivity as well as shifts in the dominant vegetation. In particular, shrubs have been replacing other vegetation, such as graminoids, in response to changes in their environment. Shrub expansion is thought to be facilitated by exposure of mineral soil and increased nutrient availability, which are often associated with disturbance. Such disturbances can be naturally occurring, typically associated with permafrost degradation or with direct anthropogenic causes such as infrastructure development. Mechanical disturbance associated with human development is not uncommon in tundra and will likely become more frequent as warming makes the Arctic more hospitable for resource extraction and other human activities. As such, this type of disturbance will become an increasingly important component of tundra C balance. Both increased productivity and shrub expansion have clear impacts on ecosystem C cycling through increased C uptake and aboveground (AG) storage. What is less clear, however, are the concurrent changes in belowground (BG) C storage. Here we inventoried AG and BG C stocks in disturbed and undisturbed tundra ecosystems to determine the effects of disturbance on tundra C balance. We measured differences in plant functional type, AG and BG biomass, soil C, and specific leaf area (SLA) for the dominant shrub (Salix) in 2 tundra ecosystems in northern Siberia—an undisturbed moist acidic tundra and an adjacent ecosystem that was used as a road ~50 years ago. Deciduous shrubs and grasses dominated both ecosystems, but biomass for both functional types was higher in the disturbed area. SLA was also higher inside the disturbance. Conversely, nonvascular plants and evergreen shrubs were less abundant in the disturbed area. BG plant biomass was substantially

  8. Organic Carbon Transformation and Mercury Methylation in Tundra Soils from Barrow Alaska

    DOE Data Explorer

    Liang, L.; Wullschleger, Stan; Graham, David; Gu, B.; Yang, Ziming

    2016-04-20

    This dataset includes information on soil labile organic carbon transformation and mercury methylation for tundra soils from Barrow, Alaska. The soil cores were collected from high-centered polygon (trough) at BEO and were incubated under anaerobic laboratory conditions at both freezing and warming temperatures for up to 8 months. Soil organic carbon including reducing sugars, alcohols, and organic acids were analyzed, and CH4 and CO2 emissions were quantified. Net production of methylmercury and Fe(II)/Fe(total) ratio were also measured and provided in this dataset.

  9. Anoxic carbon flux in photosynthetic microbial mats as revealed by metatranscriptomics

    PubMed Central

    Burow, Luke C; Woebken, Dagmar; Marshall, Ian PG; Lindquist, Erika A; Bebout, Brad M; Prufert-Bebout, Leslie; Hoehler, Tori M; Tringe, Susannah G; Pett-Ridge, Jennifer; Weber, Peter K; Spormann, Alfred M; Singer, Steven W

    2013-01-01

    Photosynthetic microbial mats possess extraordinary phylogenetic and functional diversity that makes linking specific pathways with individual microbial populations a daunting task. Close metabolic and spatial relationships between Cyanobacteria and Chloroflexi have previously been observed in diverse microbial mats. Here, we report that an expressed metabolic pathway for the anoxic catabolism of photosynthate involving Cyanobacteria and Chloroflexi in microbial mats can be reconstructed through metatranscriptomic sequencing of mats collected at Elkhorn Slough, Monterey Bay, CA, USA. In this reconstruction, Microcoleus spp., the most abundant cyanobacterial group in the mats, ferment photosynthate to organic acids, CO2 and H2 through multiple pathways, and an uncultivated lineage of the Chloroflexi take up these organic acids to store carbon as polyhydroxyalkanoates. The metabolic reconstruction is consistent with metabolite measurements and single cell microbial imaging with fluorescence in situ hybridization and NanoSIMS. PMID:23190731

  10. Anoxic carbon flux in photosynthetic microbial mats as revealed by metatranscriptomics.

    PubMed

    Burow, Luke C; Woebken, Dagmar; Marshall, Ian P G; Lindquist, Erika A; Bebout, Brad M; Prufert-Bebout, Leslie; Hoehler, Tori M; Tringe, Susannah G; Pett-Ridge, Jennifer; Weber, Peter K; Spormann, Alfred M; Singer, Steven W

    2013-04-01

    Photosynthetic microbial mats possess extraordinary phylogenetic and functional diversity that makes linking specific pathways with individual microbial populations a daunting task. Close metabolic and spatial relationships between Cyanobacteria and Chloroflexi have previously been observed in diverse microbial mats. Here, we report that an expressed metabolic pathway for the anoxic catabolism of photosynthate involving Cyanobacteria and Chloroflexi in microbial mats can be reconstructed through metatranscriptomic sequencing of mats collected at Elkhorn Slough, Monterey Bay, CA, USA. In this reconstruction, Microcoleus spp., the most abundant cyanobacterial group in the mats, ferment photosynthate to organic acids, CO2 and H2 through multiple pathways, and an uncultivated lineage of the Chloroflexi take up these organic acids to store carbon as polyhydroxyalkanoates. The metabolic reconstruction is consistent with metabolite measurements and single cell microbial imaging with fluorescence in situ hybridization and NanoSIMS. PMID:23190731

  11. Vegetation shifts observed in arctic tundra 17 years after fire

    USGS Publications Warehouse

    Barrett, Kirsten; Rocha, Adrian V.; van de Weg, Martine Janet; Shaver, Gaius

    2012-01-01

    With anticipated climate change, tundra fires are expected to occur more frequently in the future, but data on the long-term effects of fire on tundra vegetation composition are scarce. This study addresses changes in vegetation structure that have persisted for 17 years after a tundra fire on the North Slope of Alaska. Fire-related shifts in vegetation composition were assessed from remote-sensing imagery and ground observations of the burn scar and an adjacent control site. Early-season remotely sensed imagery from the burn scar exhibits a low vegetation index compared with the control site, whereas the late-season signal is slightly higher. The range and maximum vegetation index are greater in the burn scar, although the mean annual values do not differ among the sites. Ground observations revealed a greater abundance of moss in the unburned site, which may account for the high early growing season normalized difference vegetation index (NDVI) anomaly relative to the burn. The abundance of graminoid species and an absence of Betula nana in the post-fire tundra sites may also be responsible for the spectral differences observed in the remotely sensed imagery. The partial replacement of tundra by graminoid-dominated ecosystems has been predicted by the ALFRESCO model of disturbance, climate and vegetation succession.

  12. ON TEACHING ARCELLANA'S "THE MATS".

    ERIC Educational Resources Information Center

    ANDERSON, TOMMY R.

    FRANCISCO ARCELLANA'S "THE MATS," LIKE ANY WELL-CONSTRUCTED SHORT STORY, CAN SERVE AS AN IMPORTANT TEACHING DEVICE IN GUIDING STUDENTS, ESPECIALLY THOSE LEARNING ENGLISH AS A SECOND LANGUAGE, TO READ WITH UNDERSTANDING AND APPRECIATION, THE TECHNIQUES OF CONVERTING VERBALS BACK INTO VERBS, REPLACING ALL PRONOUNS WITH THEIR ANTECEDENTS IN PARALLEL…

  13. Sparse Coding for Alpha Matting

    NASA Astrophysics Data System (ADS)

    Johnson, Jubin; Varnousfaderani, Ehsan Shahrian; Cholakkal, Hisham; Rajan, Deepu

    2016-07-01

    Existing color sampling based alpha matting methods use the compositing equation to estimate alpha at a pixel from pairs of foreground (F) and background (B) samples. The quality of the matte depends on the selected (F,B) pairs. In this paper, the matting problem is reinterpreted as a sparse coding of pixel features, wherein the sum of the codes gives the estimate of the alpha matte from a set of unpaired F and B samples. A non-parametric probabilistic segmentation provides a certainty measure on the pixel belonging to foreground or background, based on which a dictionary is formed for use in sparse coding. By removing the restriction to conform to (F,B) pairs, this method allows for better alpha estimation from multiple F and B samples. The same framework is extended to videos, where the requirement of temporal coherence is handled effectively. Here, the dictionary is formed by samples from multiple frames. A multi-frame graph model, as opposed to a single image as for image matting, is proposed that can be solved efficiently in closed form. Quantitative and qualitative evaluations on a benchmark dataset are provided to show that the proposed method outperforms current state-of-the-art in image and video matting.

  14. Electrospun chitosan/polyvinyl alcohol nanofibre mats for wound healing.

    PubMed

    Charernsriwilaiwat, Natthan; Rojanarata, Theerasak; Ngawhirunpat, Tanasait; Opanasopit, Praneet

    2014-04-01

    Chitosan (CS) aqueous salt blended with polyvinyl alcohol (PVA) nanofibre mats was prepared by electrospinning. CS was dissolved with hydroxybenzotriazole (HOBt), thiamine pyrophosphate (TPP) and ethylenediaminetetraacetic acid (EDTA) in distilled water without the use of toxic or hazardous solvents. The CS aqueous salts were blended with PVA at different weight ratios, and the effect of the solution ratios was investigated. The morphologies and mechanical and swelling properties of the generated fibres were analysed. Indirect cytotoxicity studies indicated that the CS/PVA nanofibre mats were non-toxic to normal human fibroblast cells. The CS-HOBt/PVA and CS-EDTA/PVA nanofibre mats demonstrated satisfactory antibacterial activity against both gram-positive and gram-negative bacteria, and an in vivo wound healing test showed that the CS-EDTA/PVA nanofibre mats performed better than gauze in decreasing acute wound size during the first week after tissue damage. In conclusion, the biodegradable, biocompatible and antibacterial CS-EDTA/PVA nanofibre mats have potential for use as wound dressing materials. PMID:22925275

  15. The Extracellular Matrix in Photosynthetic Mats: A Cyanobacterial Gingerbread House

    NASA Astrophysics Data System (ADS)

    Stuart, R.; Stannard, W.; Bebout, B.; Pett-Ridge, J.; Mayali, X.; Weber, P. K.; Lipton, M. S.; Lee, J.; Everroad, R. C.; Thelen, M.

    2014-12-01

    Hypersaline laminated cyanobacterial mats are excellent model systems for investigating photoautotrophic contributions to biogeochemical cycling on a millimeter scale. These self-sustaining ecosystems are characterized by steep physiochemical gradients that fluctuate dramatically on hour timescales, providing a dynamic environment to study microbial response. However, elucidating the distribution of energy from light absorption into biomass requires a complete understanding of the various constituents of the mat. Extracellular polymeric substances (EPS), which can be composed of proteins, polysaccharides, lipids and DNA are a major component of these mats and may function in the redistribution of nutrients and metabolites within the community. To test this notion, we established a model mat-building culture for comparison with the phylogenetically diverse natural mat communities. In these two systems we determined how proteins and glycans in the matrix changed as a function of light and tracked nutrient flow from the matrix. Using mass spectrometry metaproteomics analysis, we found homologous proteins in both field and culture extracellular matrix that point to cyanobacterial turnover of amino acids, inorganic nutrients, carbohydrates and nucleic acids from the EPS. Other abundant functions identified included oxidative stress response from both the cyanobacteria and heterotrophs and cyanobacterial structural proteins that may play a role in mat cohesion. Several degradative enzymes also varied in abundance in the EPS in response to light availability, suggesting active secretion. To further test cyanobacterial EPS turnover, we generated isotopically-labeled EPS and used NanoSIMS to trace uptake of this labeled EPS. Our findings suggest Cyanobacteria may facilitate nutrient transfer to other groups, as well as uptake of their own products through degradation of EPS components. This work provides evidence for the essential roles of EPS for storage, structural

  16. Future distribution of tundra refugia in northern Alaska

    USGS Publications Warehouse

    Hope, Andrew G.; Waltari, Eric; Payer, David C.; Cook, Joseph A.; Talbot, Sandra L.

    2013-01-01

    Climate change in the Arctic is a growing concern for natural resource conservation and management as a result of accelerated warming and associated shifts in the distribution and abundance of northern species. We introduce a predictive framework for assessing the future extent of Arctic tundra and boreal biomes in northern Alaska. We use geo-referenced museum specimens to predict the velocity of distributional change into the next century and compare predicted tundra refugial areas with current land-use. The reliability of predicted distributions, including differences between fundamental and realized niches, for two groups of species is strengthened by fossils and genetic signatures of demographic shifts. Evolutionary responses to environmental change through the late Quaternary are generally consistent with past distribution models. Predicted future refugia overlap managed areas and indicate potential hotspots for tundra diversity. To effectively assess future refugia, variable responses among closely related species to climate change warrants careful consideration of both evolutionary and ecological histories.

  17. A Comparative Review of North American Tundra Delineations

    NASA Technical Reports Server (NTRS)

    Silver, Kirk C.; Carroll, Mark

    2013-01-01

    Recent profound changes have been observed in the Arctic environment, including record low sea ice extents and high latitude greening. Studying the Arctic and how it is changing is an important element of climate change science. The Tundra, an ecoregion of the Arctic, is directly related to climate change due to its effects on the snow ice feedback mechanism and greenhouse gas cycling. Like all ecoregions, the Tundra border is shifting, yet studies and policies require clear delineation of boundaries. There are many options for ecoregion classification systems, as well as resources for creating custom maps. To help decision makers identify the best classification system possible, we present a review of North American Tundra ecoregion delineations and further explore the methodologies, purposes, limitations, and physical properties of five common ecoregion classification systems. We quantitatively compare the corresponding maps by area using a geographic information system.

  18. Terrimonas arctica sp. nov., isolated from Arctic tundra soil.

    PubMed

    Jiang, Fan; Qiu, Xia; Chang, Xulu; Qu, Zhihao; Ren, Lvzhi; Kan, Wenjing; Guo, Youhao; Fang, Chengxiang; Peng, Fang

    2014-11-01

    A novel, Gram-stain-negative, aerobic, non-motile and rod-shaped bacterium, designated R9-86(T), was isolated from tundra soil collected near Ny-Ålesund, Svalbard Archipelago, Norway (78° N). Growth occurred at 4-28 °C (optimum, 22-25 °C) and at pH 6.0-9.0 (optimum, pH 7.0). Flexirubin-type pigments were absent. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain R9-86(T) belonged to the genus Terrimonas in the family Chitinophagaceae. 16S rRNA gene sequence similarities between strain R9-86(T) and the type strains of species of the genus Terrimonas with validly published names ranged from 93.7 to 95.0%. Strain R9-86(T) contained iso-C(15:1)-G (25.7%), iso-C(15:0) (24.5%), iso-C(17:0)-3OH (18.3%) and summed feature 3 (C(16:1)ω7c and/or C(16:1)ω6c, 8.7%) as its major cellular fatty acids; phosphatidylethanolamine and an unknown polar lipid as its main polar lipids, and MK-7 as its predominant respiratory quinone. The DNA G+C content was 48.4 mol%. On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain R9-86(T) is considered to represent a novel species of the genus Terrimonas, for which the name Terrimonas arctica sp. nov. is proposed. The type strain is R9-86(T) ( =CCTCC AB 2011004(T) =NRRL B-59114(T)). PMID:25142212

  19. The lost intrinsic fragmentation of MAT1 protein during granulopoiesis promotes the growth and metastasis of leukemic myeloblasts

    PubMed Central

    Lou, Siyue; Liu, Gang; Shimada, Hiroyuki; Yang, Xiaochun; He, Qiaojun; Wu, Lingtao

    2013-01-01

    MAT1, an assembly factor and targeting subunit of both cyclin-dependent kinase-activating kinase (CAK) and general transcription factor IIH (TFIIH) kinase, regulates cell cycle and transcription. Previous studies show that expression of intact MAT1 protein is associated with expansion of human hematopoietic stem cells (HSC), whereas intrinsically programmed or retinoic acid (RA)-induced MAT1 fragmentation accompanies granulocytic differentiation of HSC or leukemic myeloblasts. Here we determined that, in humanized mouse microenvironment, MAT1 overexpression resisted intrinsic MAT1 fragmentation to sustain hematopoietic CD34+ cell expansion while preventing granulopoiesis. Conversely, we mimicked MAT1 fragmentation in vitro and in a mouse model by overexpressing a fragmented 81-aa MAT1 polypeptide (pM9) that retains the domain for assembling CAK but cannot affix CAK to TFIIH-core. Our results showed that pM9 formed ΔCAK by competing with MAT1 for CAK assembly to mimic MAT1 fragmentation-depletion of CAK. This resulting ΔCAK acted as a dominant negative to inhibit the growth and metastasis of different leukemic myeloblasts, with or without RA-resistance, by concurrently suppressing CAK and TFIIH kinase activities to inhibit cell cycle and gene transcription. These findings suggest that the intrinsically programmed MAT1 expression and fragmentation regulate granulopoiesis by inversely coordinating CAK and TFIIH activities, whereas pM9 shares a mechanistic resemblance with MAT1 fragmentation in suppressing myeloid leukemogenesis. PMID:23765726

  20. ProMAT: protein microarray analysis tool

    SciTech Connect

    White, Amanda M.; Daly, Don S.; Varnum, Susan M.; Anderson, Kevin K.; Bollinger, Nikki; Zangar, Richard C.

    2006-04-04

    Summary: ProMAT is a software tool for statistically analyzing data from ELISA microarray experiments. The software estimates standard curves, sample protein concentrations and their uncertainties for multiple assays. ProMAT generates a set of comprehensive figures for assessing results and diagnosing process quality. The tool is available for Windows or Mac, and is distributed as open-source Java and R code. Availability: ProMAT is available at http://www.pnl.gov/statistics/ProMAT. ProMAT requires Java version 1.5.0 and R version 1.9.1 (or more recent versions) which are distributed with the tool.

  1. Geochemical characterization of Arctic tundra and implications for organic matter degradation

    NASA Astrophysics Data System (ADS)

    Gu, B.; Herndon, E.; Graham, D. E.; Phelps, T. J.; Wullschleger, S. D.; Liang, L.

    2013-12-01

    Tundra soils are uniquely cold terrestrial environments that face irrevocable change under warming climate conditions. Specifically, many tundra soils store large quantities of organic carbon that may rapidly degrade with increasing temperature, releasing C into drainage systems or to the atmosphere as greenhouse gases (CH4, CO2). In order to predict rates of C release from tundra soils, it is necessary to quantify how biogeochemical factors such as pore water chemistry, terminal electron acceptor availability, and mineral adsorption regulate rates and pathways of soil organic carbon (SOC) degradation. In this study, we examine spatial and seasonal patterns of aqueous geochemistry and SOC characteristics from across an area of tundra landscape in the Arctic. We aim to identify factors that increase or decrease rates of SOC degradation, including: 1) the composition of organic substrates, 2) abundance of terminal electron acceptors, 3) vertical transport and spatial variability of both organic and inorganic compounds, and 4) adsorption to mineral surfaces. Soil and water samples were obtained from the Barrow Environmental Observatory (BEO) in northern Alaska as part of the Next Generation Ecosystem Experiment (NGEE) Arctic project. Tundra at the BEO is characterized by permafrost below ~60 cm and polygonal features that induce topographic gradients of water saturation. Soils are organic-rich and store large amounts of slowly decomposing plant material. Chemical and physical extractions were used to obtain operationally-defined pools of SOC to evaluate their mineral associations. Water samples collected in early and late summers were analyzed for pH, electrical conductivity, and dissolved concentrations of anions, cations, organic carbon, inorganic carbon, and ferrous iron, as well as dissolved and soil gases (CH4 and CO2). We observe a steep pH gradient, with acidic pH in surface waters and near neutral pH in pore waters >20 cm below the surface. Dissolved organic

  2. Expansion of forest stands into tundra in the Noatak National Preserve, northwest Alaska

    USGS Publications Warehouse

    Suarez, F.; Binkley, D.; Kaye, M.W.; Stottlemyer, R.

    1999-01-01

    Temperatures across the northern regions of North America have been increasing for 150 years, and forests have responded to this increase. In the Noatak National Preserve in Alaska, white spruce (Picea glauca [Moench] Voss) forests reach their northern limit, occurring primarily on well-drained sites and as gallery forests along streams. Rolling plateaus of tundra separate the white spruce forests into disjunct stands. We examined patterns of tree age, tree growth, and tree encroachment into tundra ecosystems in six stands along the Agashashok River. Warming over the past 150 years appears to have increased tree growth and resulted in forest expansion into adjacent tundra ecosystems. The forest/tundra ecotone shifted by about 80 to 100 m into the tundra in the past 200 years, as evidenced by declining maximum tree age with distance towards the tundra. The decadal-scale pattern of tree establishment at the farthest extent of trees into the tundra (the tundra-forest ecotone) correlated with the detrended growth index for trees within the forests; climate conditions that led to higher tree growth appeared to foster tree establishment in the tundra. This recent forest expansion has occurred across topographic boundaries, from well-drained soils on slopes onto poorly drained, flatter areas of tundra. Further expansion of the forests may be limited by more severe wind exposure and poor drainage that make the majority of tundra less suitable for trees.

  3. Metagenomic and Metabolic Profiling of Nonlithifying and Lithifying Stromatolitic Mats of Highborne Cay, The Bahamas

    PubMed Central

    Khodadad, Christina L. M.; Foster, Jamie S.

    2012-01-01

    Background Stromatolites are laminated carbonate build-ups formed by the metabolic activity of microbial mats and represent one of the oldest known ecosystems on Earth. In this study, we examined a living stromatolite located within the Exuma Sound, The Bahamas and profiled the metagenome and metabolic potential underlying these complex microbial communities. Methodology/Principal Findings The metagenomes of the two dominant stromatolitic mat types, a nonlithifying (Type 1) and lithifying (Type 3) microbial mat, were partially sequenced and compared. This deep-sequencing approach was complemented by profiling the substrate utilization patterns of the mats using metabolic microarrays. Taxonomic assessment of the protein-encoding genes confirmed previous SSU rRNA analyses that bacteria dominate the metagenome of both mat types. Eukaryotes comprised less than 13% of the metagenomes and were rich in sequences associated with nematodes and heterotrophic protists. Comparative genomic analyses of the functional genes revealed extensive similarities in most of the subsystems between the nonlithifying and lithifying mat types. The one exception was an increase in the relative abundance of certain genes associated with carbohydrate metabolism in the lithifying Type 3 mats. Specifically, genes associated with the degradation of carbohydrates commonly found in exopolymeric substances, such as hexoses, deoxy- and acidic sugars were found. The genetic differences in carbohydrate metabolisms between the two mat types were confirmed using metabolic microarrays. Lithifying mats had a significant increase in diversity and utilization of carbon, nitrogen, phosphorus and sulfur substrates. Conclusion/Significance The two stromatolitic mat types retained similar microbial communities, functional diversity and many genetic components within their metagenomes. However, there were major differences detected in the activity and genetic pathways of organic carbon utilization. These

  4. Emissions of biogenic sulfur gases from Alaskan tundra

    SciTech Connect

    Hines, M.E.; Morrison, M.C.

    1992-10-30

    Fluxes of the biogenic sulfur gases carbonyl sulfide (COS), dimethyl sulfide (DMS), methyl mercaptan (MeSH), and carbon disulfide (CS{sub 2}) were determined from several freshwater and coastal marine tundra habitats using a dynamic enclosure method and gas chromatography. In the freshwater tundra sites, highest emissions, with a mean of 6.0 nmol m{sup {minus}2}h{sup {minus}1} (1.5-10) occurred in the water-saturated wet meadow areas inhabited by grasses, sedges, and Shpagnum mosses. In the drier upland tundra sites, highest fluxes occurred in areas inhabited by mixed vegetation and labrador tea at 3.0 nmol m{sup {minus}2}h{sup {minus}1} (0-8.3) and lowest fluxes were from lichen-dominated areas at 0.8 nmol m{sup {minus}2}h{sup {minus}1}. Sulfur emissions from a lake surface were also low at 0.8 nmol m{sup {minus}2}h{sup {minus}1}. Of the compounds measured, DMS was the dominant gas emitted from all of these sites. Sulfur emissions from the marine sites were up to 20-fold greater than fluxes in the freshwater habitats and were also dominated by DMS. Emissions of DMS were highest from intertidal soils inhabited by Carex subspathacea. This Carex sp. was grazed thoroughly by geese and DMS fluxes doubled when goose feces were left within the flux chamber. Emissions were much lower from other types of vegetation which were more spatially dominant. Sulfur emissions from tundra were among the lowest reported in the literature. When emission data were extrapolated to include all tundra globally, the global flux of biogenic sulfur from this biome is 2-3 x 10{sup 8} g yr{sup {minus}1}. This represents less than 0.001% of the estimated annual global flux of biogenic sulfur and <0.01% of the estimated terrestrial flux. The low emissions are attributed to the low availability of sulfate, certain hydrological characteristics of tundra, and the tendency for tundra to accumulate organic matter. 31 refs., 1 fig., 2 tabs.

  5. Emissions of biogenic sulfur gases from Alaskan tundra

    NASA Technical Reports Server (NTRS)

    Hines, Mark E.; Morrison, Michael C.

    1992-01-01

    Fluxes of the biogenic sulfur gases carbonyl sulfide (COS), dimethyl sulfide (DMS), methyl mercaptan (MeSH), and carbon disulfide (CS2) were determined for several freshwater and coastal marine tundra habitats using a dynamic enclosure method and gas chromatography. In the freshwater tundra sites, highest emissions, with a mean of 6.0 nmol/m(sup -2)H(sup -1) (1.5-10) occurred in the water-saturated wet meadow areas inhabited by grasses, sedges, and Sphagnum mosses. In the drier upland tundra sites, highest fluxes occurred in areas inhabited by mixed vegetation and labrador tea at 3.0 nmol/m(sup -2)h(sup -1) (0-8.3) and lowest fluxes were from lichen-dominated areas at 0.9 nmol/m(sup -2)h(sup -1). Sulfur emissions from a lake surface were also low at 0.8 nmol/m(sup -2)h(sup -1). Of the compounds measured, DMS was the dominant gas emitted from all of these sites. Sulfure emissions from the marine sites were up to 20-fold greater than fluxes in the freshwater habitats and were also dominated by DMS. Emissions of DMS were highest from intertidal soils inhabited by Carex subspathacea (150-250 nmol/m(sup -2)h(sup -1)). This Carex sp. was grazed thoroughly by geese and DMS fluxes doubled when goose feces were left within the flux chamber. Emissions were much lower from other types of vegetation which were more spatially dominant. Sulfure emissions from tundra were among the lowest reported in the literature. When emission data were extrapolated to include all tundra globally, the global flux of biogenic sulfur from this biome is 2-3 x 10(exp 8) g/yr. This represents less than 0.001 percent of the estimated annual global flux (approximately 50 Tg) of biogenic sulfur and less than 0.01 percent of the estimated terrestrial flux. The low emissions are attributed to the low availability of sulfate, certain hydrological characteristics of tundra, and the tendency for tundra to accumulate organic matter.

  6. Bacterial community structure and soil properties of a subarctic tundra soil in Council, Alaska

    PubMed Central

    Kim, Hye Min; Jung, Ji Young; Yergeau, Etienne; Hwang, Chung Yeon; Hinzman, Larry; Nam, Sungjin; Hong, Soon Gyu; Kim, Ok-Sun; Chun, Jongsik; Lee, Yoo Kyung

    2014-01-01

    The subarctic region is highly responsive and vulnerable to climate change. Understanding the structure of subarctic soil microbial communities is essential for predicting the response of the subarctic soil environment to climate change. To determine the composition of the bacterial community and its relationship with soil properties, we investigated the bacterial community structure and properties of surface soil from the moist acidic tussock tundra in Council, Alaska. We collected 70 soil samples with 25-m intervals between sampling points from 0–10 cm to 10–20 cm depths. The bacterial community was analyzed by pyrosequencing of 16S rRNA genes, and the following soil properties were analyzed: soil moisture content (MC), pH, total carbon (TC), total nitrogen (TN), and inorganic nitrogen ( and ). The community compositions of the two different depths showed that Alphaproteobacteria decreased with soil depth. Among the soil properties measured, soil pH was the most significant factor correlating with bacterial community in both upper and lower-layer soils. Bacterial community similarity based on jackknifed unweighted unifrac distance showed greater similarity across horizontal layers than through the vertical depth. This study showed that soil depth and pH were the most important soil properties determining bacterial community structure of the subarctic tundra soil in Council, Alaska. PMID:24893754

  7. Quantification of DOC concentrations in relation with soil properties of soils in tundra and taiga of Northern European Russia

    NASA Astrophysics Data System (ADS)

    Oosterwoud, M. R.; Temminghoff, E. J. M.; van der Zee, S. E. A. T. M.

    2010-05-01

    Potential mobilization and transport of Dissolved Organic Carbon (DOC) in subarctic river basins towards the oceans is enormous, because 23-48% of the worlds Soil Organic Carbon (SOC) is stored in northern regions. As climate changes, the amount and composition of DOC exported from these basins are expected to change. The transfer of organic carbon between soils and rivers results in fractionation of organic carbon compounds. The aim of this research is to determine the DOC concentrations, its fractions, i.e. humic (HA), fulvic (FA), and hydrophilic (HY) acids, and soil characteristics that influence the DOC sorptive properties of different soil types within a tundra and taiga catchment of Northern European Russia. DOC in taiga and tundra soil profiles (soil solution) consisted only of HY and FA, where HY became more abundant with increasing depth. Adsorption of DOC on mineral phases is the key geochemical process for release and removal of DOC from potentially soluble carbon pool. We found that adsorbed organic carbon may desorb easily and can release DOC quickly, without being dependent on mineralization and degradation. Although Extractable Organic Carbon (EOC) comprise only a small part of SOC, it is a significant buffering pool for DOC. We found that about 80-90% of released EOC was previously adsorbed. Fractionation of EOC is also influenced by the fact that predominantly HA and FA adsorbed to soil and therefore also are the main compounds released when desorbed. Flowpaths vary between taiga and tundra and through seasons, which likely affects DOC concentration found in streams. As climate changes, also flowpaths of water through soils may change, especially in tundra caused by thawing soils. Therefore, adsorptive properties of thawing soils exert a major control on DOC leaching to rivers. To better understand the process of DOC ad- and de-sorption in soils, process based soil chemical modelling, which could bring more insight in solution speciation, mineral

  8. Methylmercury enters an aquatic food web through acidophilic microbial mats in Yellowstone National Park, Wyoming

    USGS Publications Warehouse

    Boyd, E.S.; King, S.; Tomberlin, J.K.; Nordstrom, D.K.; Krabbenhoft, D.P.; Barkay, T.; Geesey, G.G.

    2009-01-01

    Summary Microbial mats are a visible and abundant life form inhabiting the extreme environments in Yellowstone National Park (YNP), WY, USA. Little is known of their role in food webs that exist in the Park's geothermal habitats. Eukaryotic green algae associated with a phototrophic green/purple Zygogonium microbial mat community that inhabits low-temperature regions of acidic (pH ??? 3.0) thermal springs were found to serve as a food source for stratiomyid (Diptera: Stratiomyidae) larvae. Mercury in spring source water was taken up and concentrated by the mat biomass. Monomethylmercury compounds (MeHg +), while undetectable or near the detection limit (0.025 ng l -1) in the source water of the springs, was present at concentrations of 4-7 ng g-1 dry weight of mat biomass. Detection of MeHg + in tracheal tissue of larvae grazing the mat suggests that MeHg+ enters this geothermal food web through the phototrophic microbial mat community. The concentration of MeHg+ was two to five times higher in larval tissue than mat biomass indicating MeHg+ biomagnification occurred between primary producer and primary consumer trophic levels. The Zygogonium mat community and stratiomyid larvae may also play a role in the transfer of MeHg+ to species in the food web whose range extends beyond a particular geothermal feature of YNP. ?? 2008 The Authors. Journal compilation ?? 2008 Society for Applied Microbiology and Blackwell Publishing Ltd.

  9. Methylmercury enters an aquatic food web through acidophilic microbial mats in Yellowstone National Park, Wyoming.

    PubMed

    Boyd, Eric S; King, Susan; Tomberlin, Jeffery K; Nordstrom, D Kirk; Krabbenhoft, David P; Barkay, Tamar; Geesey, Gill G

    2009-04-01

    Microbial mats are a visible and abundant life form inhabiting the extreme environments in Yellowstone National Park (YNP), WY, USA. Little is known of their role in food webs that exist in the Park's geothermal habitats. Eukaryotic green algae associated with a phototrophic green/purple Zygogonium microbial mat community that inhabits low-temperature regions of acidic (pH approximately 3.0) thermal springs were found to serve as a food source for stratiomyid (Diptera: Stratiomyidae) larvae. Mercury in spring source water was taken up and concentrated by the mat biomass. Monomethylmercury compounds (MeHg(+)), while undetectable or near the detection limit (0.025 ng l(-1)) in the source water of the springs, was present at concentrations of 4-7 ng g(-1) dry weight of mat biomass. Detection of MeHg(+) in tracheal tissue of larvae grazing the mat suggests that MeHg(+) enters this geothermal food web through the phototrophic microbial mat community. The concentration of MeHg(+) was two to five times higher in larval tissue than mat biomass indicating MeHg(+) biomagnification occurred between primary producer and primary consumer trophic levels. The Zygogonium mat community and stratiomyid larvae may also play a role in the transfer of MeHg(+) to species in the food web whose range extends beyond a particular geothermal feature of YNP. PMID:19170726

  10. Unequal Recombination and Evolution of the Mating-Type (MAT) Loci in the Pathogenic Fungus Grosmannia clavigera and Relatives

    PubMed Central

    Tsui, Clement K.-M.; DiGuistini, Scott; Wang, Ye; Feau, Nicolas; Dhillon, Braham; Bohlmann, Jörg; Hamelin, Richard C.

    2013-01-01

    Sexual reproduction in fungi is regulated by the mating-type (MAT) locus where recombination is suppressed. We investigated the evolution of MAT loci in eight fungal species belonging to Grosmannia and Ophiostoma (Sordariomycetes, Ascomycota) that include conifer pathogens and beetle symbionts. The MAT1-2 idiomorph/allele was identified from the assembled and annotated Grosmannia clavigera genome, and the MAT locus is flanked by genes coding for cytoskeleton protein (SLA) and DNA lyase. The synteny of these genes is conserved and consistent with other members in Ascomycota. Using sequences from SLA and flanking regions, we characterized the MAT1-1 idiomorph from other isolates of G. clavigera and performed dotplot analysis between the two idiomorphs. Unexpectedly, the MAT1-2 idiomorph contains a truncated MAT1-1-1 gene upstream of the MAT1-2-1 gene that bears the high-mobility-group domain. The nucleotide and amino acid sequence of the truncated MAT1-1-1 gene is similar to its homologous copy in the MAT1-1 idiomorph in the opposite mating-type isolate, except that positive selection is acting on the truncated gene and the alpha(α)-box that encodes the transcription factor has been deleted. The MAT idiomorphs sharing identical gene organization were present in seven additional species in the Ophiostomatales, suggesting that the presence of truncated MAT1-1-1 gene is a general pattern in this order. We propose that an ancient unequal recombination event resulted in the ancestral MAT1-1-1 gene integrated into the MAT1-2 idiomorph and surviving as the truncated MAT1-1-1 genes. The α-box domain of MAT1-1-1 gene, located at the same MAT locus adjacent to the MAT1-2-1 gene, could have been removed by deletion after recombination due to mating signal interference. Our data confirmed a 1:1 MAT/sex ratio in two pathogen populations, and showed that all members of the Ophiostomatales studied here including those that were previously deemed asexual have the potential to

  11. Canopy Spectral Imaging (NDVI) As A Proxy For Shrub Biomass And Ecosystem Carbon Fluxes Across Arctic Tundra Habitats

    NASA Astrophysics Data System (ADS)

    Flower, C. E.; Welker, J. M.; Gonzalez-Meler, M. A.

    2015-12-01

    There is widespread consensus that climate change is contributing to rapid vegetation shifts in the ecologically sensitive Arctic tundra. These tussock grass dominated systems are shifting to tussock/woody shrub communities leading to likely alterations in carbon (C) sequestration and ecosystem productivity, which in turn can manifest in "greening" and changes in normalized difference vegetation index values (NDVI). While the expansion of woody vegetation is well established, our understanding of the ecosystem dynamics associated with this new habitat remain largely unknown. To untangle how the Arctic tundra may be impacted by these vegetation shifts we paired vegetation measurements (i.e. shrub biomass, leaf area, and shrub canopy area) and ecosystem C fluxes (e.g. net ecosystem exchange, NEE, and ecosystem respiration) with ground-level measurements of NDVI. Measurements were conducted at the Toolik Field Station in dry heath and moist acidic tundra habitats which are two primary habitat types on the North Slope of Alaska. We found strong positive relationships between shrub leaf area and biomass as well as shrub canopy area and biomass, relationships that were corroborated with NDVI measurements. This lends support for the use of NDVI as a proxy measurement of leaf area and shrub biomass. Additionally, NDVI was negatively correlated with ecosystem respiration across habitats, with respiratory fluxes consistently higher in the moist acidic relative to the dry heath tundra. Finally, we observed a significant positive nonlinear relationship between NEE and NDVI (R2~0.8; P<0.01). Shrub removal revealed that NEE was strongly controlled by woody shrubs. The positive relationship between NDVI and NEE highlights the potential shifts in the C balance of the Arctic tundra associated with woody encroachment. This increased plant productivity may offset greenhouse gas losses from permafrost degradation contributing some resilience to this system otherwise considered a

  12. Direct piezoelectric responses of soft composite fiber mats

    NASA Astrophysics Data System (ADS)

    Varga, M.; Morvan, J.; Diorio, N.; Buyuktanir, E.; Harden, J.; West, J. L.; Jákli, A.

    2013-04-01

    Recently soft fiber mats electrospun from solutions of Barium Titanate (BT) ferroelectric ceramics particles and polylactic acid (PLA) were found to have large (d33 ˜ 1 nm/V) converse piezoelectric signals offering a myriad of applications ranging from active implants to smart textiles. Here, we report direct piezoelectric measurements (electric signals due to mechanical stress) of the BT/PLA composite fiber mats at several BT concentrations. A homemade testing apparatus provided AC stresses in the 50 Hz-1.5 kHz-frequency range. The piezoelectric constant d33 ˜ 0.5 nC/N and the compression modulus Y ˜ 104-105 Pa found are in agreement with the prior converse piezoelectric and compressibility measurements. Importantly, the direct piezoelectric signal is large enough to power a small LCD by simple finger tapping of a 0.15 mm thick 2-cm2 area mat. We propose using these mats in active Braille cells and in liquid crystal writing tablets.

  13. Impacts of Arctic Climate Change on Tundra Fire Regimes at Interannual to Millennial Timescales

    NASA Astrophysics Data System (ADS)

    Hu, F.; Young, A. M.; Chipman, M. L.; Duffy, P.; Higuera, P. E.

    2014-12-01

    Tundra burning is emerging as a key process in the rapidly changing Arctic, and knowledge of tundra fire-regime responses to climate change is essential for projecting Earth system dynamics. This presentation will focus on climate-fire relationships in the Arctic, spatiotemporal patterns of Holocene tundra burning, and the effects of tundra burning on carbon cycling. Analysis of historical records reveals that across the Arctic, tundra burning occurred primarily in areas where mean summer temperature exceeded 9 °C and total summer precipitation was below 115 mm. In Alaska, summer temperature and precipitation explain >90% of the interannual variability in tundra area burned from AD 1950-2009, with thresholds of 10.5 °C and 140 mm. These patterns imply tipping points in tundra fire-regime responses to climate change. The frequency of tundra fires has varied greatly across space and through time. Approximately 1.0% of the circum-Arctic tundra burned from AD 2002-2013, and 4.5% of the Alaskan tundra burned from AD 1950-2009. The latter encompassed ecoregions with fire rotation periods ranging from ~400 to 13,640 years. Charcoal analysis of lake sediments also shows that Arctic tundra can sustain a wide range of fire regimes. Fires were rare on the Alaskan North Slope throughout the Holocene, implying that the climate thresholds evident in the historical records have seldom been crossed. In contrast, in areas of NW Alaska, tundra has burned regularly at 100-250 year intervals during the late Holocene. Tundra burning may cause sudden releases of the enormous amount of Arctic soil C. Charcoal particles from recent burns yielded 14C ages of AD 1952-2006. Thus the C consumed in recent fires may recover through vegetation succession. However, our results suggest that in areas that have burned multiple times in recent decades, old soil C is vulnerable to future fires.

  14. Effect of the biota diversity on the composition of low-molecular-weight water-soluble organic compounds in southern tundra soils

    NASA Astrophysics Data System (ADS)

    Shamrikova, E. V.; Kubik, O. S.; Punegov, V. V.; Gruzdev, I. V.

    2014-03-01

    Water extracts from the organic horizons of southern-tundra loamy permafrost-affected soils (a surface-gleyed tundra soil, a surface-gleyed soddy tundra soil (Haplic Stagnosols (Gelic)), and a peaty tundra soil (Histic Cryosol (Reductaquic)) and their undecomposed moss layers have been analyzed. The total weight concentration of the cations (Ca2+, Mg2+, K+, and Na+) determined by the atomic absorption method reaches 20 mg/dm3 in the organic horizons and 40-90 mg/dm3 in the undecomposed moss layers. Potassium and calcium ions dominate in all the organic horizons (80-90% of the total weight); potassium ions prevail in the mosses (about 70%). The weight concentration of carbon in the water-soluble organic compounds is 0.04-0.07 g/dm3 in the organic horizons and 0.20-0.40 g/dm3 in the undecomposed moss layers. The content of low-molecular-weight organic compounds (alcohols, carbohydrates, and acids) identified by gas chromatography and chromatomass spectrometry is 1-30 mg/dm3 in the organic horizons of the soils and 80-180 mg/dm3 in the mosses, which does not exceed 26% of the total organic carbon in the extracts.

  15. Phylogenetic group-associated differences in regulation of the common colonization factor Mat fimbria in Escherichia coli.

    PubMed

    Lehti, Timo A; Bauchart, Philippe; Kukkonen, Maini; Dobrindt, Ulrich; Korhonen, Timo K; Westerlund-Wikström, Benita

    2013-03-01

    Heterogeneity of cell population is a key component behind the evolutionary success of Escherichia coli. The heterogeneity supports species adaptation and mainly results from lateral gene transfer. Adaptation may also involve genomic alterations that affect regulation of conserved genes. Here we analysed regulation of the mat (or ecp) genes that encode a conserved fimbrial adhesin of E. coli. We found that the differential and temperature-sensitive expression control of the mat operon is dependent on mat promoter polymorphism and closely linked to phylogenetic grouping of E. coli. In the mat promoter lineage favouring fimbriae expression, the mat operon-encoded regulator MatA forms a positive feedback loop that overcomes the repression by H-NS and stabilizes the fimbrillin mRNA under low growth temperature, acidic pH or elevated levels of acetate. The study exemplifies phylogenetic group-associated expression of a highly common surface organelle in E. coli. PMID:23347101

  16. Bacterial contamination control mats: a comparative study.

    PubMed Central

    Meddick, H. M.

    1977-01-01

    The ability of six different types of contamination control mats currently in use at the entrances to theatre suites and other clean areas to remove bacteria-carrying particles from theatre trolley wheeels was compared. Marked differences in the effectiveness of this property were obtained; and all mats showed some disadvantages. Modification of one of the mats has resulted in improved efficiency under working conditions. Images Plate 1 PMID:267665

  17. Summertime N2O, CH4 and CO2 exchanges from a tundra marsh and an upland tundra in maritime Antarctica

    NASA Astrophysics Data System (ADS)

    Zhu, Renbin; Ma, Dawei; Xu, Hua

    2014-02-01

    This study provides the first concurrent measurements of nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) fluxes from a tundra marsh and an upland tundra in maritime Antarctica over the summers of 2007/2008 and 2011/2012. Tundra N2O and CH4 fluxes showed large spatial variations depending on local hydrological regimes. N2O sinks generally occurred at waterlogged marsh sites (-3.0 to 27.5 μg N2O m-2 h-1) whereas relatively dry and mesic sites presented weak or strong N2O sources (2.2-41.6 μg N2O m-2 h-1). Upland tundra sites showed negligible N2O emissions due to low soil TN and NH4+-N contents. Dry/upland tundra sites showed weak to strong CH4 uptake (-4.5 to -85.8 μg CH4 m-2 h-1). The waterlogged sites showed weak to strong CH4 emissions (29.8 μg CH4 m-2 h-1-2.4 mg CH4 m-2 h-1). Both tundra marsh and upland tundra experienced a large net CO2 uptake with the greatest mean CO2 uptake rate (-92.1 mg CO2 m-2 h-1) at dry marsh sites. Mean ecosystem respiration (ER) ranged between 82.5 ± 13.2 and 174.9 ± 25.7 mg CO2 m-2 h-1 at all the sites, and showed a strong exponential correlation (P < 0.001) with 0-10 cm soil temperature. Gross photosynthesis (Pg) was more than two times higher in tundra marsh than in upland tundra due to the difference of vegetation coverage. N2O flux showed a strong negative correlation (P < 0.01) with 0-10 cm soil temperature at the marsh sites, and significant or weak positive correlations with total daily radiation (TDR) and sunlight time (ST). No significant correlation was obtained between CH4 fluxes and environmental variables at tundra marsh and upland tundra sites. There was a significant negative correlation (P < 0.01) between NEE and 0-10 cm mean soil temperature, total daily radiation. Our results indicated that the lowering of water table significantly increased N2O emissions and CH4 consumption, but decreased C loss from the tundra marsh. In the future, the combination of climate warming and frequent precipitation

  18. MatLab Script and Functional Programming

    NASA Technical Reports Server (NTRS)

    Shaykhian, Gholam Ali

    2007-01-01

    MatLab Script and Functional Programming: MatLab is one of the most widely used very high level programming languages for scientific and engineering computations. It is very user-friendly and needs practically no formal programming knowledge. Presented here are MatLab programming aspects and not just the MatLab commands for scientists and engineers who do not have formal programming training and also have no significant time to spare for learning programming to solve their real world problems. Specifically provided are programs for visualization. The MatLab seminar covers the functional and script programming aspect of MatLab language. Specific expectations are: a) Recognize MatLab commands, script and function. b) Create, and run a MatLab function. c) Read, recognize, and describe MatLab syntax. d) Recognize decisions, loops and matrix operators. e) Evaluate scope among multiple files, and multiple functions within a file. f) Declare, define and use scalar variables, vectors and matrices.

  19. Bentonite mat demonstration. Final report

    SciTech Connect

    Serrato, M.G.

    1994-12-30

    The Bentonite Mat Demonstration was developed to provide the Environmental Restoration Department with field performance characteristics and engineering data for an alternative closure cover system configuration. The demonstration was initiated in response to regulatory concerns regarding the use of an alternative cover system for future design configurations. These design considerations are in lieu of the US Environmental Protection Agency (EPA) Recommended Design for Closure Cover Systems and specifically a single compacted kaolin clay layer with a hydraulic conductivity of 1 {times} 10{sup {minus}7} cm/sec. This alternative configuration is a composite geosynthetic material hydraulic barrier consisting from bottom to top: 2 ft compacted sandy clay layer (typical local Savannah River Site soil type) that is covered by a bentonite mat--geosynthetic clay liner (GCL) and is overlaid by a 40 mil High Density Polyethylene (HDPE) geomembrane--flexible membrane liner. This effort was undertaken to obtain and document the necessary field performance/engineering data for future designs and meet regulatory technical requirements for an alternative cover system configuration. The composite geosynthetic materials hydraulic barrier is the recommended alternative cover system configuration for containment of hazardous and low level radiological waste layers that have a high potential of subsidence to be used at the Savannah River Site (SRS). This alternative configuration mitigates subsidence effects in providing a flexible, lightweight cover system to maintain the integrity of the closure. The composite geosynthetic materials hydraulic barrier is recommended for the Sanitary Landfill and Low Level Radiological Waste Disposal Facility (LLRWDF) Closures.

  20. Effects of mat characteristics on plantar pressure patterns and perceived mat properties during landing in gymnastics.

    PubMed

    Pérez-Soriano, Pedro; Llana-Belloch, Salvador; Morey-Klapsing, Gaspar; Perez-Turpin, Jose Antonio; Cortell-Tormo, Juan Manuel; van den Tillaar, Roland

    2010-11-01

    Shock absorption and stability during landings is provided by both, gymnast ability and mat properties. The aims of this study were to determine the influence of different mat constructions on their energy absorption and stability capabilities, and to analyse how these properties affect gymnast's plantar pressures as well as subjective mat perception during landing. Six mats were tested using a standard mechanical drop test. In addition, plantar pressures and subjective perception during landing were obtained from 15 expert gymnasts. The different mats influenced plantar pressures and gymnasts' subjective perception during landing of gymnasts. Significant correlations between plantar pressures at the medial metatarsal and lateral metatarsal zones of the gymnasts' feet with the different shock absorption characteristics of the mats were found. However, subjective perception tests were not able to discriminate mat functionality between the six mats as no significant correlations between the mechanical mat properties with the subjective perception of these properties were found. This study demonstrated that plantar pressures are a useful tool for discriminating different landing mats. Using similar approaches, ideally including kinematics as well, could help us in our understanding about the influences of different mats upon gymnast-mat interaction. PMID:21309299

  1. Winter precipitation and snow accumulation drive the methane sink or source strength of Arctic tussock tundra.

    PubMed

    Blanc-Betes, Elena; Welker, Jeffrey M; Sturchio, Neil C; Chanton, Jeffrey P; Gonzalez-Meler, Miquel A

    2016-08-01

    Arctic winter precipitation is projected to increase with global warming, but some areas will experience decreases in snow accumulation. Although Arctic CH4 emissions may represent a significant climate forcing feedback, long-term impacts of changes in snow accumulation on CH4 fluxes remain uncertain. We measured ecosystem CH4 fluxes and soil CH4 and CO2 concentrations and (13) C composition to investigate the metabolic pathways and transport mechanisms driving moist acidic tundra CH4 flux over the growing season (Jun-Aug) after 18 years of experimental snow depth increases and decreases. Deeper snow increased soil wetness and warming, reducing soil %O2 levels and increasing thaw depth. Soil moisture, through changes in soil %O2 saturation, determined predominance of methanotrophy or methanogenesis, with soil temperature regulating the ecosystem CH4 sink or source strength. Reduced snow (RS) increased the fraction of oxidized CH4 (Fox) by 75-120% compared to Ambient, switching the system from a small source to a net CH4 sink (21 ± 2 and -31 ± 1 mg CH4  m(-2)  season(-1) at Ambient and RS). Deeper snow reduced Fox by 35-40% and 90-100% in medium- (MS) and high- (HS) snow additions relative to Ambient, contributing to increasing the CH4 source strength of moist acidic tundra (464 ± 15 and 3561 ± 97 mg CH4  m(-2)  season(-1) at MS and HS). Decreases in Fox with deeper snow were partly due to increases in plant-mediated CH4 transport associated with the expansion of tall graminoids. Deeper snow enhanced CH4 production within newly thawed soils, responding mainly to soil warming rather than to increases in acetate fermentation expected from thaw-induced increases in SOC availability. Our results suggest that increased winter precipitation will increase the CH4 source strength of Arctic tundra, but the resulting positive feedback on climate change will depend on the balance between areas with more or less snow accumulation than they are currently

  2. Differential Utilization of Carbon Substrates by Bacteria and Fungi in Tundra Soil▿

    PubMed Central

    Rinnan, Riikka; Bååth, Erland

    2009-01-01

    Little is known about the contribution of bacteria and fungi to decomposition of different carbon compounds in arctic soils, which are an important carbon store and possibly vulnerable to climate warming. Soil samples from a subarctic tundra heath were incubated with 13C-labeled glucose, acetic acid, glycine, starch, and vanillin, and the incorporation of 13C into different phospholipid fatty acids (PLFA; indicative of growth) and neutral lipid fatty acids (NLFA; indicative of fungal storage) was measured after 1 and 7 days. The use of 13C-labeled substrates allowed the addition of substrates at concentrations low enough not to affect the total amount of PLFA. The label of glucose and acetic acid was rapidly incorporated into the PLFA in a pattern largely corresponding to the fatty acid concentration profile, while glycine and especially starch were mainly taken up by bacteria and not fungi, showing that different groups of the microbial community were responsible for substrate utilization. The 13C-incorporation from the complex substrates (starch and vanillin) increased over time. There was significant allocation of 13C into the fungal NLFA, except for starch. For glucose, acetic acid, and glycine, the allocation decreased over time, indicating use of the storage products, whereas for vanillin incorporation into fungal NLFA increased during the incubation. In addition to providing information on functioning of the microbial communities in an arctic soil, our study showed that the combination of PLFA and NLFA analyses yields additional information on the dynamics of substrate degradation. PMID:19363072

  3. Natural causes of the tundra-taiga boundary.

    PubMed

    Sveinbjörnsson, Bjartmar; Hofgaard, Annika; Lloyd, Andrea

    2002-08-01

    The tundra-taiga interface is characterized by a change in tree cover or density, tree size and shape, tree growth, and reproduction. Generally, trees get denser, taller, and less damaged as one moves from the tundra into the taiga proper. The environmental covariates and possible mechanisms resulting in these patterns are addressed in the paper. Low seed rain density, lack of safe sites caused by microclimatic variation, low surface substrate moisture, and low soil nutrient availability may limit the density of the tree species. Tree growth may be limited by a short growing season and further diminished, by shoot and root damage reducing carbon and nutrient stores as well as by reducing carbon and nutrient uptake capacities. Positive and negative feedbacks of tree density on tree growth exist at treeline. Increased tree density leads to increased air temperature and decreased wind damage, but also to lower soil temperature, reduced nutrient availability, and greater nutrient competition. PMID:12374055

  4. Diversification of Nitrogen Sources in Various Tundra Vegetation Types in the High Arctic

    PubMed Central

    Skrzypek, Grzegorz; Wojtuń, Bronisław; Richter, Dorota; Jakubas, Dariusz; Wojczulanis-Jakubas, Katarzyna; Samecka-Cymerman, Aleksandra

    2015-01-01

    Low nitrogen availability in the high Arctic represents a major constraint for plant growth, which limits the tundra capacity for carbon retention and determines tundra vegetation types. The limited terrestrial nitrogen (N) pool in the tundra is augmented significantly by nesting seabirds, such as the planktivorous Little Auk (Alle alle). Therefore, N delivered by these birds may significantly influence the N cycling in the tundra locally and the carbon budget more globally. Moreover, should these birds experience substantial negative environmental pressure associated with climate change, this will adversely influence the tundra N-budget. Hence, assessment of bird-originated N-input to the tundra is important for understanding biological cycles in polar regions. This study analyzed the stable nitrogen composition of the three main N-sources in the High Arctic and in numerous plants that access different N-pools in ten tundra vegetation types in an experimental catchment in Hornsund (Svalbard). The percentage of the total tundra N-pool provided by birds, ranged from 0–21% in Patterned-ground tundra to 100% in Ornithocoprophilous tundra. The total N-pool utilized by tundra plants in the studied catchment was built in 36% by birds, 38% by atmospheric deposition, and 26% by atmospheric N2-fixation. The stable nitrogen isotope mixing mass balance, in contrast to direct methods that measure actual deposition, indicates the ratio between the actual N-loads acquired by plants from different N-sources. Our results enhance our understanding of the importance of different N-sources in the Arctic tundra and the used methodological approach can be applied elsewhere. PMID:26376204

  5. Cold season emissions dominate the Arctic tundra methane budget

    NASA Astrophysics Data System (ADS)

    Zona, Donatella; Gioli, Beniamino; Commane, Róisín; Lindaas, Jakob; Wofsy, Steven C.; Miller, Charles E.; Dinardo, Steven J.; Dengel, Sigrid; Sweeney, Colm; Karion, Anna; Chang, Rachel Y.-W.; Henderson, John M.; Murphy, Patrick C.; Goodrich, Jordan P.; Moreaux, Virginie; Liljedahl, Anna; Watts, Jennifer D.; Kimball, John S.; Lipson, David A.; Oechel, Walter C.

    2016-01-01

    Arctic terrestrial ecosystems are major global sources of methane (CH4); hence, it is important to understand the seasonal and climatic controls on CH4 emissions from these systems. Here, we report year-round CH4 emissions from Alaskan Arctic tundra eddy flux sites and regional fluxes derived from aircraft data. We find that emissions during the cold season (September to May) account for ≥50% of the annual CH4 flux, with the highest emissions from noninundated upland tundra. A major fraction of cold season emissions occur during the "zero curtain" period, when subsurface soil temperatures are poised near 0 °C. The zero curtain may persist longer than the growing season, and CH4 emissions are enhanced when the duration is extended by a deep thawed layer as can occur with thick snow cover. Regional scale fluxes of CH4 derived from aircraft data demonstrate the large spatial extent of late season CH4 emissions. Scaled to the circumpolar Arctic, cold season fluxes from tundra total 12 ± 5 (95% confidence interval) Tg CH4 y-1, ∼25% of global emissions from extratropical wetlands, or ∼6% of total global wetland methane emissions. The dominance of late-season emissions, sensitivity to soil environmental conditions, and importance of dry tundra are not currently simulated in most global climate models. Because Arctic warming disproportionally impacts the cold season, our results suggest that higher cold-season CH4 emissions will result from observed and predicted increases in snow thickness, active layer depth, and soil temperature, representing important positive feedbacks on climate warming.

  6. Cold season emissions dominate the Arctic tundra methane budget.

    PubMed

    Zona, Donatella; Gioli, Beniamino; Commane, Róisín; Lindaas, Jakob; Wofsy, Steven C; Miller, Charles E; Dinardo, Steven J; Dengel, Sigrid; Sweeney, Colm; Karion, Anna; Chang, Rachel Y-W; Henderson, John M; Murphy, Patrick C; Goodrich, Jordan P; Moreaux, Virginie; Liljedahl, Anna; Watts, Jennifer D; Kimball, John S; Lipson, David A; Oechel, Walter C

    2016-01-01

    Arctic terrestrial ecosystems are major global sources of methane (CH4); hence, it is important to understand the seasonal and climatic controls on CH4 emissions from these systems. Here, we report year-round CH4 emissions from Alaskan Arctic tundra eddy flux sites and regional fluxes derived from aircraft data. We find that emissions during the cold season (September to May) account for ≥ 50% of the annual CH4 flux, with the highest emissions from noninundated upland tundra. A major fraction of cold season emissions occur during the "zero curtain" period, when subsurface soil temperatures are poised near 0 °C. The zero curtain may persist longer than the growing season, and CH4 emissions are enhanced when the duration is extended by a deep thawed layer as can occur with thick snow cover. Regional scale fluxes of CH4 derived from aircraft data demonstrate the large spatial extent of late season CH4 emissions. Scaled to the circumpolar Arctic, cold season fluxes from tundra total 12 ± 5 (95% confidence interval) Tg CH4 y(-1), ∼ 25% of global emissions from extratropical wetlands, or ∼ 6% of total global wetland methane emissions. The dominance of late-season emissions, sensitivity to soil environmental conditions, and importance of dry tundra are not currently simulated in most global climate models. Because Arctic warming disproportionally impacts the cold season, our results suggest that higher cold-season CH4 emissions will result from observed and predicted increases in snow thickness, active layer depth, and soil temperature, representing important positive feedbacks on climate warming. PMID:26699476

  7. Analysis of state of vehicular scars on Arctic Tundra, Alaska

    NASA Technical Reports Server (NTRS)

    Lathram, E. H.

    1974-01-01

    Identification on ERTS images of severe vehicular scars in the northern Alaska tundra suggests that, if such scars are of an intensity or have spread to a dimension such that they can be resolved by ERTS sensors (20 meters), they can be identified and their state monitored by the use of ERTS images. Field review of the state of vehicular scars in the Umiat area indicates that all are revegetating at varying rates and are approaching a stable state.

  8. Impact of permafrost thaw on Arctic tundra pond geochemistry

    NASA Astrophysics Data System (ADS)

    Reyes, F.; Lougheed, V.

    2012-12-01

    Increasing evidence indicates the arctic tundra is changing physically, biologically, and chemically due to climate warming. With a warmer climate, permafrost is expected to thaw and influence the chemistry of arctic aquatic ecosystems. However, knowledge is limited on how geochemistry of arctic tundra pond ecosystems will respond. By re-sampling historical IBP ponds in Barrow, AK first sampled in the 1970s, previous studies have shown an increase in water temperature, nutrients and algal biomass through time. Results from this study indicate an increase of Ca, Mg, and Na in the water column, and a decrease in pH relative to the 1970s, suggesting an increased rate and magnitude of carbonate and Mg release. Seasonal trends were also examined to understand what processes, such as mineral weathering, peat decomposition and evaporation, were currently most influential in determining pond geochemistry. An increase in Ca/Na molar ratios, and carbonate and magnesium concentrations indicates that these tundra ponds are experiencing greater carbonate weathering compared to the 1970s and the rate of carbonate weathering increases in ponds as the summer progresses. However, increasing dissolved organic carbon (DOC) concentrations originating from peat decomposition are likely neutralizing additional inputs of carbonate, causing pond pH to decrease and exacerbating mineral weathering. A strong positive relationship between element concentrations and active layer pond thaw depth suggests that the origin of these additional solutes is likely from permafrost thaw. Active layer thaw depth has increased substantially over the past 40 years in the IBP ponds. Chloride/Bromide molar ratios and Deuterium/ 18-Oxygen isotope ratios will be used to determine the degree of evaporation occurring in tundra ponds. Ultimately, this study provides evidence for how geochemistry can identify the sources of chemical inputs to Arctic ponds affected by climate change and permafrost thaw.

  9. Cold season emissions dominate the Arctic tundra methane budget

    PubMed Central

    Zona, Donatella; Gioli, Beniamino; Lindaas, Jakob; Wofsy, Steven C.; Miller, Charles E.; Dinardo, Steven J.; Dengel, Sigrid; Sweeney, Colm; Karion, Anna; Chang, Rachel Y.-W.; Henderson, John M.; Murphy, Patrick C.; Goodrich, Jordan P.; Moreaux, Virginie; Liljedahl, Anna; Watts, Jennifer D.; Kimball, John S.; Lipson, David A.; Oechel, Walter C.

    2016-01-01

    Arctic terrestrial ecosystems are major global sources of methane (CH4); hence, it is important to understand the seasonal and climatic controls on CH4 emissions from these systems. Here, we report year-round CH4 emissions from Alaskan Arctic tundra eddy flux sites and regional fluxes derived from aircraft data. We find that emissions during the cold season (September to May) account for ≥50% of the annual CH4 flux, with the highest emissions from noninundated upland tundra. A major fraction of cold season emissions occur during the “zero curtain” period, when subsurface soil temperatures are poised near 0 °C. The zero curtain may persist longer than the growing season, and CH4 emissions are enhanced when the duration is extended by a deep thawed layer as can occur with thick snow cover. Regional scale fluxes of CH4 derived from aircraft data demonstrate the large spatial extent of late season CH4 emissions. Scaled to the circumpolar Arctic, cold season fluxes from tundra total 12 ± 5 (95% confidence interval) Tg CH4 y−1, ∼25% of global emissions from extratropical wetlands, or ∼6% of total global wetland methane emissions. The dominance of late-season emissions, sensitivity to soil environmental conditions, and importance of dry tundra are not currently simulated in most global climate models. Because Arctic warming disproportionally impacts the cold season, our results suggest that higher cold-season CH4 emissions will result from observed and predicted increases in snow thickness, active layer depth, and soil temperature, representing important positive feedbacks on climate warming. PMID:26699476

  10. How to preserve the tundra in a warming climate?

    NASA Astrophysics Data System (ADS)

    Käyhkö, Jukka

    2014-05-01

    The warming climate of the polar regions may change much of the current arctic-alpine tundra to forest or dense scrubland. This modification requires adaptation by traditional livelihoods such as reindeer herding, which relies on diverse, seasonal pasturelands. Vegetation change may also trigger positive warming feedbacks, where more abundant forest-scrub vegetation will decrease the global albedo. NCoE Tundra team investigates the complex climate-animal-plant interaction of the tundra ecosystem and aim to unravel the capability of herbivorous mammals to control the expansion of woody vegetation. Our interdisciplinary approach involves several work packages, whose results will be summarised in the presentation. In the ecological WPs, we study the dynamics of the natural food chains involving small herbivorous and the impacts of reindeer on the vegetation and the population dynamics of those arctic-alpine plants, which are most likely to become threatened in a warmer climate. Our study demonstrates the potential of a relatively sparse reindeer stocks (2-5 heads per km2) together with natural populations of arvicoline rodents to prevent the expansion of erect woody plants at the arctic-alpine timberline. In the climatic WPs we study the impact of grazing-dependent vegetation differences on the fraction of solar energy converted to heat. In the socio-economic WPs, we study the conditions for maintaining the economic and cultural viability of reindeer herding while managing the land use so that the arctic-alpine biota would be preserved.

  11. Anurans in a Subarctic Tundra Landscape Near Cape Churchill, Manitoba

    USGS Publications Warehouse

    Reiter, M.E.; Boal, C.W.; Andersen, D.E.

    2008-01-01

    Distribution, abundance, and habitat relationships of anurans inhabiting subarctic regions are poorly understood, and anuran monitoring protocols developed for temperate regions may not be applicable across large roadless areas of northern landscapes. In addition, arctic and subarctic regions of North America are predicted to experience changes in climate and, in some areas, are experiencing habitat alteration due to high rates of herbivory by breeding and migrating waterfowl. To better understand subarctic anuran abundance, distribution, and habitat associations, we conducted anuran calling surveys in the Cape Churchill region of Wapusk National Park, Manitoba, Canada, in 2004 and 2005. We conducted surveys along ~l-km transects distributed across three landscape types (coastal tundra, interior sedge meadow-tundra, and boreal forest-tundra interface) to estimate densities and probabilities of detection of Boreal Chorus Frogs (Pseudacris maculata) and Wood Frogs (Lithobates sylvaticus). We detected a Wood Frog or Boreal Chorus Frog on 22 (87%) of 26 transects surveyed, but probability of detection varied between years and species and among landscape types. Estimated densities of both species increased from the coastal zone inland toward the boreal forest edge. Our results suggest anurans occur across all three landscape types in our study area, but that species-specific spatial patterns exist in their abundances. Considerations for both spatial and temporal variation in abundance and detection probability need to be incorporated into surveys and monitoring programs for subarctic anurans.

  12. Advancing the long view of ecological change in tundra systems

    PubMed Central

    Post, Eric; Høye, Toke T.

    2013-01-01

    Despite uncertainties related to sustained funding, ideological rivalries and the turnover of research personnel, long-term studies and studies espousing a long-term perspective in ecology have a history of contributing landmark insights into fundamental topics, such as population- and community dynamics, species interactions and ecosystem function. They also have the potential to reveal surprises related to unforeseen events and non-stationary dynamics that unfold over the course of ongoing observation and experimentation. The unprecedented rate and magnitude of current and expected abiotic changes in tundra environments calls for a synthetic overview of the scope of ecological responses these changes have elicited. In this special issue, we present a series of contributions that advance the long view of ecological change in tundra systems, either through sustained long-term research, or through retrospective or prospective modelling. Beyond highlighting the value of long-term research in tundra systems, the insights derived herein should also find application to the study of ecological responses to environmental change in other biomes as well. PMID:23836784

  13. Emissions of biogenic sulfur gases from Alaskan tundra

    NASA Technical Reports Server (NTRS)

    Hines, Mark E.; Morrison, Michael C.

    1992-01-01

    Results of sulfur emission measurements made in freshwater and marine wetlands in Alaskan tundra during the Arctic Boundary Layer Expedition 2A (ABLE 3A) in July 1988 are presented. The data indicate that this type of tundra emits very small amounts of gaseous sulfur and, when extrapolated globally, accounts for a very small percentage of the global flux of biogenic sulfur to the atmosphere. Sulfur emissions from marine sites are up to 20-fold greater than fluxes from freshwater habitats and are dominated by dimethyl sulfide (DMS). Highest emissions, with a mean of 6.0 nmol/sq m/h, occurred in water-saturated wet meadow areas. In drier upland tundra sites, highest fluxes occurred in areas inhabited by mixed vegetation and labrador tea at 3.0 nmol/sq m/h and lowest fluxes were from lichen-dominated areas at 0.9 nmol/sq m/h. DMS was the dominant gas emitted from all these sites. Emissions of DMS were highest from intertidal soils inhabited by Carex subspathacea.

  14. Siberian tundra ecosystem vegetation and carbon stocks four decades after wildfire

    NASA Astrophysics Data System (ADS)

    Loranty, Michael M.; Natali, Susan M.; Berner, Logan T.; Goetz, Scott J.; Holmes, Robert M.; Davydov, Sergei P.; Zimov, Nikita S.; Zimov, Sergey A.

    2014-11-01

    Tundra ecosystem fire regimes are intensifying with important implications for regional and global carbon (C) and energy dynamics. Although a substantial portion of the tundra biome is located in Russia, the vast majority of accessible studies describe North American tundra fires. Here we use field observations and high-resolution satellite remote sensing observations to describe the effects of wildfire on ecosystem C pools and vegetation communities four decades after fire for a tundra ecosystem in northeastern Siberia. Our analyses reveal no differences between soil physical properties and C pools in burned and unburned tundra, which we attribute to low combustion of organic soil associated with low-severity fire. Field and remote sensing data show no differences in aboveground C pools and vegetation communities indicating recovery to prefire conditions. These results are comparable to observations of ecosystem recovery in North American tundra. An assessment of literature data indicate that the average annual area burned in Russian tundra is an order of magnitude larger than that of Alaskan tundra, highlighting a crucial need to assess Russian tundra fire regimes in order to understand the current and future role of the biome wide fire regime in regional and global C and energy dynamics.

  15. Nonwoven glass fiber mat reinforces polyurethane adhesive

    NASA Technical Reports Server (NTRS)

    Roseland, L. M.

    1967-01-01

    Nonwoven glass fiber mat reinforces the adhesive properties of a polyurethane adhesive that fastens hardware to exterior surfaces of aluminum tanks. The mat is embedded in the uncured adhesive. It ensures good control of the bond line and increases the peel strength.

  16. Complex polar lipids of a hot spring cyanobacterial mat and its cultivated inhabitants

    NASA Technical Reports Server (NTRS)

    Ward, D. M.; Panke, S.; Kloppel, K. D.; Christ, R.; Fredrickson, H.

    1994-01-01

    The complex polar lipids of the hot spring cyanobacterial mat in the 50 to 55 degrees C region of Octopus Spring, Yellowstone National Park, and of thermophilic bacteria cultivated from this or similar habitats, were compared in an attempt to understand the microbial sources of the major lipid biomarkers in this community. Intact complex lipids were analyzed directly by fast atom bombardment mass spectrometry (FAB-MS), two-dimensional thin-layer chromatography (TLC), and combined TLC-FAB-MS. FAB-MS and TLC gave qualitatively similar results, suggesting that the mat contains major lipids most like those of the cyanobacterial isolate we studied, Synechococcus sp. strain Y-7c-s. These include monoglycosyl, diglycosyl, and sulfoquinosovyl diglycerides (MG, DG, and SQ, respectively) and phosphatidyl glycerol (PG). Though Chloroflexus aurantiacus also contains MG, DG, and PG, the fatty acid chain lengths of mat MGs, DGs, and PGs resemble more those of cyanobacterial than green nonsulfur bacterial lipids. FAB-MS spectra of the lipids of nonphototrophic bacterial isolates were distinctively different from those of the mat and phototrophic isolates. The lipids of these nonphototrophic isolates were not detected in the mat, but most could be detected when added to mat samples. The mat also contains major glycolipids and aminophospholipids of unknown structure and origin. FAB-MS and TLC did not always give quantitatively similar results. In particular, PG and SQ may give disproportionately high FAB-MS responses.

  17. The micromorphology of Younger Dryas-aged black mats from Nevada, Arizona, Texas and New Mexico

    NASA Astrophysics Data System (ADS)

    Harris-Parks, Erin

    2016-01-01

    Black mats are organic-rich sediments and soils that form in wet environments associated with spring discharge. Micromorphological and geochemical analyses of 25 black mats dating to the Younger Dryas Chronozone (12.9-11.7 ka) and early Holocene were conducted to determine their composition and depositional environment. Samples were collected from Arizona, New Mexico, Texas and Nevada. Micromorphological analyses were conducted on thin sections using polarized and blue fluorescent light. These analyses determined that black mats contain humic acids, fine (5-20 μm) plant fragments, diatoms, phytoliths, and gastropods. The dominant type of organic matter in black mats is derived from herbaceous plants, contradicting previous studies that supported algal or charcoal sources. Differences in the micromorphological characteristics of the samples revealed that black mats formed as three different types, organic horizons, moist soils and, ponded sediments, depending on their topographic position in relation to the water table. The microscopic evidence found in black mats supports the presence of widespread wet environments in Nevada and Arizona during the Younger Dryas Chronozone, clearly indicating a sustained period of greater effective moisture, optimal for spring discharge and black mat formation.

  18. Carbon pools and isotopic trends in a hypersaline cyanobacterial mat.

    PubMed

    Wieland, A; Pape, T; Möbius, J; Klock, J-H; Michaelis, W

    2008-03-01

    The fine-scale depth distribution of major carbon pools and their stable carbon isotopic signatures (delta(13)C) were determined in a cyanobacterial mat (Salin-de-Giraud, Camargue, France) to study early diagenetic alterations and the carbon preservation potential in hypersaline mat ecosystems. Particular emphasis was placed on the geochemical role of extracellular polymeric substances (EPS). Total carbon (C(tot)), organic carbon (C(org)), total nitrogen (N(tot)), total hydrolysable amino acids (THAA), carbohydrates, cyanobacteria-derived hydrocarbons (8-methylhexadecane, n-heptadec-5-ene, n-heptadecane) and EPS showed highest concentrations in the top millimetre of the mat and decreased with depth. The hydrocarbons attributed to cyanobacteria showed the strongest decrease in concentration with depth. This correlated well with the depth profiles of oxygenic photosynthesis and oxygen, which were detected in the top 0.6 and 1.05 mm, respectively, at a high down-welling irradiance (1441 micromol photons m(-2) s(-1)). At depths beneath the surface layer, the C(org) was composed mainly of amino acids and carbohydrates. A resistance towards microbial degradation could have resulted from interactions with diverse functional groups present in biopolymers (EPS) and with minerals deposited in the mat. A (13)C enrichment with depth for the total carbon pool (C(tot)) was observed, with delta(13)C values ranging from -16.3 per thousand at the surface to -11.3 per thousand at 9-10 mm depth. Total lipids depicted a delta(13)C value of -17.2 per thousand in the top millimetre and then became depleted in (13)C with depth (-21.7 to -23.3 per thousand). The delta(13)C value of EPS varied only slightly with depth (-16.1 to -17.3 per thousand) and closely followed the delta(13)C value of C(org) at depths beneath 4 mm. The EPS represents an organic carbon pool of preservation potential during early stages of diagenesis in recent cyanobacterial mats as a result of a variety of possible

  19. Investigation of VEGGIE Root Mat

    NASA Technical Reports Server (NTRS)

    Subbiah, Arun M.

    2013-01-01

    VEGGIE is a plant growth facility that utilizes the phenomenon of capillary action as its primary watering system. A cloth made of Meta Aramid fiber, known as Nomex is used to wick water up from a reservoir to the bottom of the plants roots. This root mat system is intended to be low maintenance with no moving parts and requires minimal crew interface time. Unfortunately, the water wicking rates are inconsistent throughout the plant life cycle, thus causing plants to die. Over-wicking of water occurs toward the beginning of the cycle, while under-wicking occurs toward the middle. This inconsistency of wicking has become a major issue, drastically inhibiting plant growth. The primary objective is to determine the root cause of the inconsistent wicking through experimental testing. Suspect causes for the capillary water column to break include: a vacuum effect due to a negative pressure gradient in the water reservoir, contamination of material due to minerals in water and back wash from plant fertilizer, induced air bubbles while using syringe refill method, and material limitations of Nomex's ability to absorb and retain water. Experimental testing will be conducted to systematically determine the cause of under and over-wicking. Pressure gages will be used to determine pressure drop during the course of the plant life cycle and during the water refill process. A debubbler device will be connected to a root mat in order to equalize pressure inside the reservoir. Moisture and evaporation tests will simultaneously be implemented to observe moisture content and wicking rates over the course of a plant cycle. Water retention tests will be performed using strips of Nomex to determine materials wicking rates, porosity, and absorptivity. Through these experimental tests, we will have a better understanding of material properties of Nomex, as well as determine the root cause of water column breakage. With consistent test results, a forward plan can be achieved to resolve

  20. Flat laminated microbial mat communities

    NASA Astrophysics Data System (ADS)

    Franks, Jonathan; Stolz, John F.

    2009-10-01

    Flat laminated microbial mats are complex microbial ecosystems that inhabit a wide range of environments (e.g., caves, iron springs, thermal springs and pools, salt marshes, hypersaline ponds and lagoons, methane and petroleum seeps, sea mounts, deep sea vents, arctic dry valleys). Their community structure is defined by physical (e.g., light quantity and quality, temperature, density and pressure) and chemical (e.g., oxygen, oxidation/reduction potential, salinity, pH, available electron acceptors and donors, chemical species) parameters as well as species interactions. The main primary producers may be photoautotrophs (e.g., cyanobacteria, purple phototrophs, green phototrophs) or chemolithoautophs (e.g., colorless sulfur oxidizing bacteria). Anaerobic phototrophy may predominate in organic rich environments that support high rates of respiration. These communities are dynamic systems exhibiting both spatial and temporal heterogeneity. They are characterized by steep gradients with microenvironments on the submillimeter scale. Diel oscillations in the physical-chemical profile (e.g., oxygen, hydrogen sulfide, pH) and species distribution are typical for phototroph-dominated communities. Flat laminated microbial mats are often sites of robust biogeochemical cycling. In addition to well-established modes of metabolism for phototrophy (oxygenic and non-oxygenic), respiration (both aerobic and anaerobic), and fermentation, novel energetic pathways have been discovered (e.g., nitrate reduction couple to the oxidation of ammonia, sulfur, or arsenite). The application of culture-independent techniques (e.g., 16S rRNA clonal libraries, metagenomics), continue to expand our understanding of species composition and metabolic functions of these complex ecosystems.

  1. Chemical and spectroscopic analyses of organic matter transformation in warming tundra soils

    NASA Astrophysics Data System (ADS)

    Herndon, E.; Roy Chowdhury, T.; Mann, B. F.; Graham, D. E.; Bargar, J.; Gu, B.; Liang, L.

    2013-12-01

    Many tundra soils are currently major carbon sinks; however, an increase in temperature may shift these systems to C sources and create a positive feedback for warming. In order to predict future C release from tundra soils, it is necessary to quantify rates of SOM degradation and to identify the reactants and products of microbial decomposition reactions. In this study, multiple spectroscopic techniques are used to investigate SOM during laboratory incubations of tundra soils. We aim to characterize the chemical transformation of organic matter during decomposition as a function of temperature and geochemistry. Frozen soil cores were obtained from the Barrow Environmental Observatory (BEO) in northern Alaska as part of the Next Generation Ecosystem Experiment Arctic project. To investigate the influence of temperature on organic matter degradation and compositional changes, soil horizons from each core were homogenized and soil material was incubated at -2°C, +4°C, or +8°C. Samples were sacrificed periodically over 100 days, and chemical and physical extractions were used to separate SOM into operationally-defined pools, including light (density < 1.6 g cm-2) and mineral-bound, and water-, acid-, base-, and non-soluble fractions. A suite of wet-chemical and spectroscopic analyses was used to measure CO2 and CH4 formation and soil C compositional changes, including techniques such as Fourier transform infrared spectroscopy, high performance liquid chromatography (HPLC), high resolution mass spectrometry, and X-ray absorption spectroscopy. Detailed chemical and spectroscopic analyses reveal significant differences amongst extracts and with depth in the soil. In general, more organic C was extracted in the base than in the acid and water fractions, and mineral-bound organic C increased with depth. The water-soluble C fraction showed the lowest molar absorptivity of the three extracts and consisted of mostly lower-molecular weight organics. Acid-soluble C increased

  2. Distinct temperature sensitivity among taiga and tundra shrubs in Alaska

    NASA Astrophysics Data System (ADS)

    Andreu-Hayles, L.; Anchukaitis, K. J.; D'Arrigo, R.

    2014-12-01

    Shrub expansion into Arctic and alpine tundra ecosystems is well documented, mostly over the last 50 years, based on remote sensing data, aerial photography, and in-situ observations. Warming temperatures are considered the main driver of the observed change in shrub vegetation patterns. Here, we assess the relationship between temperatures and shrub growth from five populations of Salix spp. (willow) and Alnus spp. (alder) in Alaska growing within the tundra and the boreal forest (~taiga) using dendrochronological techniques. The three tundra shrub sites are located on the Dalton Highway north from Toolik Lake (~69ºN 148ºW), whereas the two taiga shrub sites are located closer to Fairbanks at the Twelve Mile Summit site (~65ºN 146ºW). Because shrub ages vary among the studied populations lead to different time spans for the ring-width chronologies generated, a common period with available satellite data spanning from 1982 to 2010 was selected for this study. All tundra shrub chronologies shared a strong positive response to summer temperatures despite growing in heterogeneous site conditions and belonging to different species. In contrast, in the taiga, summer temperatures enhance willow growth, whereas alder growth appears almost insensitive to temperature over the interval studied. Extending the analyses back in time, a very strong positive relationship was found between alder ring-width and June temperatures prior to 1970. This phenomenon, a weakening of the previously existing relationship between growth and temperatures, was also detected in white spruce (Picea glauca) growing at the same site, and it is known in the literature as the 'divergence problem'. Thus, at this taiga location, alder shrubs and trees seem to have similar growth patterns. Summer temperatures no longer seem to enhance taiga alder growth. Shrubs of different species exposed to the same climatic conditions can exhibit varied growth responses. The distinct temperature sensitivities

  3. Changing Seasonality of Tundra Vegetation and Associated Climatic Variables

    NASA Astrophysics Data System (ADS)

    Bhatt, U. S.; Walker, D. A.; Raynolds, M. K.; Bieniek, P.; Epstein, H. E.; Comiso, J. C.; Pinzon, J.; Tucker, C. J.; Steele, M.; Ermold, W. S.; Zhang, J.

    2014-12-01

    This study documents changes in the seasonality of tundra vegetation productivity and its associated climate variables using long-term data sets. An overall increase of Pan-Arctic tundra greenness potential corresponds to increased land surface temperatures and declining sea ice concentrations. While sea ice has continued to decline, summer land surface temperature and vegetation productivity increases have stalled during the last decade in parts of the Arctic. To understand the processes behind these features we investigate additional climate parameters. This study employs remotely sensed weekly 25-km sea ice concentration, weekly surface temperature, and bi-weekly NDVI from 1982 to 2013. Maximum NDVI (MaxNDVI, Maximum Normalized Difference Vegetation Index), Time Integrated NDVI (TI-NDVI), Summer Warmth Index (SWI, sum of degree months above freezing during May-August), ocean heat content (PIOMAS, model incorporating ocean data assimilation), and snow water equivalent (GlobSnow, assimilated snow data set) are explored. We analyzed the data for the full period (1982-2013) and for two sub-periods (1982-1998 and 1999-2013), which were chosen based on the declining Pan-Arctic SWI since 1998. MaxNDVI has increased from 1982-2013 over most of the Arctic but has declined from 1999 to 2013 over western Eurasia, northern Canada, and southwest Alaska. TI-NDVI has trends that are similar to those for MaxNDVI for the full period but displays widespread declines over the 1999-2013 period. Therefore, as the MaxNDVI has continued to increase overall for the Arctic, TI-NDVI has been declining since 1999. SWI has large relative increases over the 1982-2013 period in eastern Canada and Greenland and strong declines in western Eurasia and southern Canadian tundra. Weekly Pan-Arctic tundra land surface temperatures warmed throughout the summer during the 1982-1998 period but display midsummer declines from 1999-2013. Weekly snow water equivalent over Arctic tundra has declined over

  4. Alaska North Slope Tundra Travel Model and Validation Study

    SciTech Connect

    Harry R. Bader; Jacynthe Guimond

    2006-03-01

    The Alaska Department of Natural Resources (DNR), Division of Mining, Land, and Water manages cross-country travel, typically associated with hydrocarbon exploration and development, on Alaska's arctic North Slope. This project is intended to provide natural resource managers with objective, quantitative data to assist decision making regarding opening of the tundra to cross-country travel. DNR designed standardized, controlled field trials, with baseline data, to investigate the relationships present between winter exploration vehicle treatments and the independent variables of ground hardness, snow depth, and snow slab thickness, as they relate to the dependent variables of active layer depth, soil moisture, and photosynthetically active radiation (a proxy for plant disturbance). Changes in the dependent variables were used as indicators of tundra disturbance. Two main tundra community types were studied: Coastal Plain (wet graminoid/moist sedge shrub) and Foothills (tussock). DNR constructed four models to address physical soil properties: two models for each main community type, one predicting change in depth of active layer and a second predicting change in soil moisture. DNR also investigated the limited potential management utility in using soil temperature, the amount of photosynthetically active radiation (PAR) absorbed by plants, and changes in microphotography as tools for the identification of disturbance in the field. DNR operated under the assumption that changes in the abiotic factors of active layer depth and soil moisture drive alteration in tundra vegetation structure and composition. Statistically significant differences in depth of active layer, soil moisture at a 15 cm depth, soil temperature at a 15 cm depth, and the absorption of photosynthetically active radiation were found among treatment cells and among treatment types. The models were unable to thoroughly investigate the interacting role between snow depth and disturbance due to a lack

  5. Feedbacks between tall shrubland development and active layer temperatures in northwest Siberian arctic tundra

    NASA Astrophysics Data System (ADS)

    Epstein, H. E.; Frost, G. V.; Walker, D. A.; Matyshak, G.

    2013-12-01

    Permafrost soils are a globally significant carbon store, but changes in permafrost thermal regime observed in recent decades across much of the Arctic suggest that permafrost carbon balance is likely to change with continued climate warming. Critical to changes in permafrost carbon balance in a warmer world, however, are feedbacks between changes in the composition and density of surface vegetation, and the thermal state of permafrost. Shrub expansion has been widely observed in the northwest Siberian Low Arctic, but the magnitude and direction of shrub-induced impacts to permafrost temperature and stability remain poorly understood. Here we evaluate changes to active layer properties and thermal regime that occur during tall shrubland development (shrubs > 1.5 m height) within a northwest Siberian landscape dominated by well-developed, small-scale patterned ground features (e.g., non-sorted circles). We measured the annual time-series of soil temperature at 5 cm and 20 cm depth, and the structural attributes of vegetation at patterned-ground microsites across four stages of tall shrubland development: low-growing tundra lacking erect shrubs, newly-developed shrublands, mature shrublands, and paludified shrublands. Mean summer soil temperatures declined with increasing shrub cover and moss thickness, but winter soil temperatures increased with shrub development. Shrubland development strongly attenuated cryoturbation, promoting the establishment of complete vegetation cover and the development of a continuous organic mat. Increased vegetation cover, in turn, led to further reduced cryoturbation and an aggrading permafrost table. These observations indicate that tall shrub expansion that is now occurring in patterned-ground landscapes of the northwest Siberian Arctic may buffer permafrost from atmospheric warming, and increase carbon storage in these systems at least in the short term.

  6. Morphology, release characteristics, and antimicrobial effect of nisin-loaded electrospun gelatin fiber mat.

    PubMed

    Dheraprasart, Chanuttaporn; Rengpipat, Sirirat; Supaphol, Pitt; Tattiyakul, Jirarat

    2009-11-01

    Gelatin electrospun (e-spun) fiber mats containing nisin were produced by electrostatic spinning of gelatin-nisin in 70% (vol/vol) acetic acid aqueous solutions. Varying nisin loading concentration (0 to 3% [wt/wt]) did not affect the fiber average diameter, whereas increasing gelatin concentration from 20 to 24% (wt/vol) caused an increase in the average diameter. All nisin-loaded gelatin e-spun fiber mats demonstrated inhibition against Lactobacillus plantarum TISTR 850. However, all fiber mats were fragile and easily dissolved in water. Cross-linking by saturated glutaraldehyde vapor at 37 degrees C for 5 min was done to strengthen the mat. Tensile strength, Young's modulus, and elongation of the cross-linked gelatin-nisin e-spun fiber mats varied in the range of 2.6 to 20.3 MPa, 163 to 966 MPa, and 1.7 to 5.9% , respectively. Cross-linking did not affect the mat's inhibition activity against L. plantarum TISTR 850. Nisin retention in cross-linked antimicrobial gelatin e-spun fiber mats was in the range of 1.0 to 1.22% . Increasing temperature caused an increase in nisin release, but increasing water activity did not cause a significant difference in nisin release over 50 h. After storage at 25 degrees C for 5 months, the antimicrobial gelatin e-spun fiber mat still showed inhibition against L. plantarum TISTR 850. The mats also inhibited the growth of Staphylococcus aureus and Listeria monocytogenes but not Salmonella Typhimurium. PMID:19903391

  7. Characterization of metal-binding bioflocculants produced by the cyanobacterial component of mixed microbial mats.

    PubMed Central

    Bender, J; Rodriguez-Eaton, S; Ekanemesang, U M; Phillips, P

    1994-01-01

    Mixed-species microbial mats that were dominated by the cyanobacterium Oscillatoria sp. and contained heterotrophic and purple autotrophic bacteria were constructed for specific bioremediation applications. When the mats were challenged with metals, production and secretion of metal-binding extracellular polysaccharide bioflocculants were observed. The concentration of these negatively charged polysaccharides was correlated with the removal of manganese from the water column beneath a surface microbial mat. Bioflocculants from an Oscillatoria sp. that was isolated from the mat were collected and concentrated for characterization. A chromatographic analysis revealed a heterogeneous population of polysaccharides with respect to charge density and molecular size. The subpopulation of polysaccharides which exhibited the highest level of flocculating activity was polyanionic and had a molecular weight of more than 200,000. A glycosyl analysis of the bioflocculants revealed the presence of galacturonic acid (2.2%) and glucuronic acid (1.86%). The presence of these components, which were negatively charged at the pH levels generated by the mats during photosynthesis (pH > 7.5), may account for the metal-binding properties of the mats. PMID:8074512

  8. Spatiotemporal patterns of tundra fires: late-Quaternary charcoal records from Alaska

    NASA Astrophysics Data System (ADS)

    Chipman, M. L.; Hudspith, V.; Higuera, P. E.; Duffy, P. A.; Kelly, R.; Oswald, W. W.; Hu, F. S.

    2015-07-01

    Anthropogenic climate change has altered many ecosystem processes in the Arctic tundra and may have resulted in unprecedented fire activity. Evaluating the significance of recent fires requires knowledge from the paleofire record because observational data in the Arctic span only several decades, much shorter than the natural fire rotation in Arctic tundra regions. Here we report results of charcoal analysis on lake sediments from four Alaskan lakes to infer the broad spatial and temporal patterns of tundra-fire occurrence over the past 35 000 years. Background charcoal accumulation rates are low in all records (range is 0-0.05 pieces cm-2 yr-1), suggesting minimal biomass burning across our study areas. Charcoal peak analysis reveals that the mean fire-return interval (FRI; years between consecutive fire events) ranged from ca. 1650 to 6050 years at our sites, and that the most recent fire events occurred from ca. 880 to 7030 years ago, except for the CE 2007 Anaktuvuk River Fire. These mean FRI estimates are longer than the fire rotation periods estimated for the past 63 years in the areas surrounding three of the four study lakes. This result suggests that the frequency of tundra burning was higher over the recent past compared to the late Quaternary in some tundra regions. However, the ranges of FRI estimates from our paleofire records overlap with the expected values based on fire-rotation-period estimates from the observational fire data, and the differences are statistically insignificant. Together with previous tundra-fire reconstructions, these data suggest that the rate of tundra burning was spatially variable and that fires were extremely rare in our study areas throughout the late Quaternary. Given the rarity of tundra burning over multiple millennia in our study areas and the pronounced effects of fire on tundra ecosystem processes such as carbon cycling, dramatic tundra ecosystem changes are expected if anthropogenic climate change leads to more

  9. Fermentation couples Chloroflexi and sulfate-reducing bacteria to Cyanobacteria in hypersaline microbial mats.

    PubMed

    Lee, Jackson Z; Burow, Luke C; Woebken, Dagmar; Everroad, R Craig; Kubo, Mike D; Spormann, Alfred M; Weber, Peter K; Pett-Ridge, Jennifer; Bebout, Brad M; Hoehler, Tori M

    2014-01-01

    Past studies of hydrogen cycling in hypersaline microbial mats have shown an active nighttime cycle, with production largely from Cyanobacteria and consumption from sulfate-reducing bacteria (SRB). However, the mechanisms and magnitude of hydrogen cycling have not been extensively studied. Two mats types near Guerrero Negro, Mexico-permanently submerged Microcoleus microbial mat (GN-S), and intertidal Lyngbya microbial mat (GN-I)-were used in microcosm diel manipulation experiments with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), molybdate, ammonium addition, and physical disruption to understand the processes responsible for hydrogen cycling between mat microbes. Across microcosms, H2 production occurred under dark anoxic conditions with simultaneous production of a suite of organic acids. H2 production was not significantly affected by inhibition of nitrogen fixation, but rather appears to result from constitutive fermentation of photosynthetic storage products by oxygenic phototrophs. Comparison to accumulated glycogen and to CO2 flux indicated that, in the GN-I mat, fermentation released almost all of the carbon fixed via photosynthesis during the preceding day, primarily as organic acids. Across mats, although oxygenic and anoxygenic phototrophs were detected, cyanobacterial [NiFe]-hydrogenase transcripts predominated. Molybdate inhibition experiments indicated that SRBs from a wide distribution of DsrA phylotypes were responsible for H2 consumption. Incubation with (13)C-acetate and NanoSIMS (secondary ion mass-spectrometry) indicated higher uptake in both Chloroflexi and SRBs relative to other filamentous bacteria. These manipulations and diel incubations confirm that Cyanobacteria were the main fermenters in Guerrero Negro mats and that the net flux of nighttime fermentation byproducts (not only hydrogen) was largely regulated by the interplay between Cyanobacteria, SRBs, and Chloroflexi. PMID:24616716

  10. Fermentation couples Chloroflexi and sulfate-reducing bacteria to Cyanobacteria in hypersaline microbial mats

    PubMed Central

    Lee, Jackson Z.; Burow, Luke C.; Woebken, Dagmar; Everroad, R. Craig; Kubo, Mike D.; Spormann, Alfred M.; Weber, Peter K.; Pett-Ridge, Jennifer; Bebout, Brad M.; Hoehler, Tori M.

    2013-01-01

    Past studies of hydrogen cycling in hypersaline microbial mats have shown an active nighttime cycle, with production largely from Cyanobacteria and consumption from sulfate-reducing bacteria (SRB). However, the mechanisms and magnitude of hydrogen cycling have not been extensively studied. Two mats types near Guerrero Negro, Mexico—permanently submerged Microcoleus microbial mat (GN-S), and intertidal Lyngbya microbial mat (GN-I)—were used in microcosm diel manipulation experiments with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), molybdate, ammonium addition, and physical disruption to understand the processes responsible for hydrogen cycling between mat microbes. Across microcosms, H2 production occurred under dark anoxic conditions with simultaneous production of a suite of organic acids. H2 production was not significantly affected by inhibition of nitrogen fixation, but rather appears to result from constitutive fermentation of photosynthetic storage products by oxygenic phototrophs. Comparison to accumulated glycogen and to CO2 flux indicated that, in the GN-I mat, fermentation released almost all of the carbon fixed via photosynthesis during the preceding day, primarily as organic acids. Across mats, although oxygenic and anoxygenic phototrophs were detected, cyanobacterial [NiFe]-hydrogenase transcripts predominated. Molybdate inhibition experiments indicated that SRBs from a wide distribution of DsrA phylotypes were responsible for H2 consumption. Incubation with 13C-acetate and NanoSIMS (secondary ion mass-spectrometry) indicated higher uptake in both Chloroflexi and SRBs relative to other filamentous bacteria. These manipulations and diel incubations confirm that Cyanobacteria were the main fermenters in Guerrero Negro mats and that the net flux of nighttime fermentation byproducts (not only hydrogen) was largely regulated by the interplay between Cyanobacteria, SRBs, and Chloroflexi. PMID:24616716

  11. Nitrogen dynamics in arctic tundra soils of varying age: differential responses to fertilization and warming.

    PubMed

    Yano, Yuriko; Shaver, Gaius R; Rastetter, Edward B; Giblin, Anne E; Laundre, James A

    2013-12-01

    In the foothills of the Brooks Range, Alaska, different glaciation histories have created landscapes with varying soil age. Productivity of most of these landscapes is generally N limited, but varies widely, as do plant species composition and soil properties (e.g., pH). We hypothesized that the projected changes in productivity and vegetation composition under a warmer climate might be mediated through differential changes in N availability across soil age. We compared readily available [water-soluble NH4 (+), NO3 (-), and amino acids (AA)], moderately available (soluble proteins), hydrolyzable, and total N pools across three tussock-tundra landscapes with soil ages ranging from 11.5k to 300k years. The effects of fertilization and warming on these N pools were also compared for the two younger sites. Readily available N was highest at the oldest site, and AA accounted for 80-89 % of this N. At the youngest site, inorganic N constituted the majority (80-97 %) of total readily available N. This variation reflected the large differences in plant functional group composition and soil chemical properties. Long-term (8-16 years) fertilization increased the soluble inorganic N by 20- to 100-fold at the intermediate-age site, but only by twofold to threefold at the youngest site. Warming caused small and inconsistent changes in the soil C:N ratio and AA, but only in soils beneath Eriophorum vaginatum, the dominant tussock-forming sedge. These differential responses suggest that the ecological consequences of warmer climates on these tundra ecosystems are more complex than simply elevated N-mineralization rates, and that the responses of landscapes might be impacted by soil age, or time since deglaciation. PMID:23928888

  12. Increased wintertime CO2 loss as a result of sustained tundra warming

    NASA Astrophysics Data System (ADS)

    Webb, Elizabeth E.; Schuur, Edward A. G.; Natali, Susan M.; Oken, Kiva L.; Bracho, Rosvel; Krapek, John P.; Risk, David; Nickerson, Nick R.

    2016-02-01

    Permafrost soils currently store approximately 1672 Pg of carbon (C), but as high latitudes warm, this temperature-protected C reservoir will become vulnerable to higher rates of decomposition. In recent decades, air temperatures in the high latitudes have warmed more than any other region globally, particularly during the winter. Over the coming century, the arctic winter is also expected to experience the most warming of any region or season, yet it is notably understudied. Here we present nonsummer season (NSS) CO2 flux data from the Carbon in Permafrost Experimental Heating Research project, an ecosystem warming experiment of moist acidic tussock tundra in interior Alaska. Our goals were to quantify the relationship between environmental variables and winter CO2 production, account for subnivean photosynthesis and late fall plant C uptake in our estimate of NSS CO2 exchange, constrain NSS CO2 loss estimates using multiple methods of measuring winter CO2 flux, and quantify the effect of winter soil warming on total NSS CO2 balance. We measured CO2 flux using four methods: two chamber techniques (the snow pit method and one where a chamber is left under the snow for the entire season), eddy covariance, and soda lime adsorption, and found that NSS CO2 loss varied up to fourfold, depending on the method used. CO2 production was dependent on soil temperature and day of season but atmospheric pressure and air temperature were also important in explaining CO2 diffusion out of the soil. Warming stimulated both ecosystem respiration and productivity during the NSS and increased overall CO2 loss during this period by 14% (this effect varied by year, ranging from 7 to 24%). When combined with the summertime CO2 fluxes from the same site, our results suggest that this subarctic tundra ecosystem is shifting away from its historical function as a C sink to a C source.

  13. Lipid Biomarkers for a Hypersaline Microbial Mat Community

    NASA Technical Reports Server (NTRS)

    Jahnke, Linda; Orphan, Victoria; Embaye, Tsegereda; Turk, Kendra; Kubo, Mike; Summons, Roger

    2004-01-01

    The use of lipid biomarkers and their carbon isotopic compositions are valuable tools for establishing links to ancient microbial ecosystems. Various lipids associated with specific microbial groups can serve as biomarkers for establishing organism source and function in contemporary microbial ecosystems (membrane lipids), and by analogy, potential relevance to ancient organic-rich sedimentary rocks (geolipids). As witnessed by the stromatolite record, benthic microbial mats grew in shallow water lagoonal environments. Our recent work has focused on lipid biomarker analysis of a potential analogue for such ancient mats growing in a set of hypersaline evaporation ponds at Guerrero Negro, Baja California Sur, Mexico. The aerobic, surface layer of this mat (0 to 1 mm) contained a variety of ester-bound fatty acids (FA) representing a diverse bacterial population including cyanobacteria, sulphate reducers (SRB) and heterotrophs. Biomarkers for microeukaryotes detected in this layer included sterols, C-20 polyunsaturated FA and a highly branched isoprenoid, diagnostic for diatoms. Cyanobacteria were also indicated by the presence of a diagnostic set of mid-chain methylalkanes. C-28, to C-34 wax esters (WXE) present in relatively small amounts in the upper 3 mm of the mat are considered biomarkers for green non-sulphur bacteria. Ether-bound isoprenoids were also identified although in considerably lower abundance than ester-bound FA (approx. 1:l0). These complex ether lipids included archatol, hydroxyarchaeol and a C-40 tetraether, all in small amounts. After ether cleavage with boron tribromide, the major recovered isoprenyl was a C-30:1. This C(sub 30;1) yelded squalane after hydrogenation, a known geobiomarker for hypersaline environments in ancient oils and sediments. In this mat, it represents the dominant Archaeal population. The carbon isotopic composition of biomarker lipids were generally depleted relative to the bulk organic material (delta C-13 TOC -10%). Most

  14. Airborne Spectral Measurements of Surface-Atmosphere Anisotropy for Arctic Sea Ice and Tundra

    NASA Technical Reports Server (NTRS)

    Arnold, G. Thomas; Tsay, Si-Chee; King, Michael D.; Li, Jason Y.; Soulen, Peter F.

    1999-01-01

    Angular distributions of spectral reflectance for four common arctic surfaces: snow-covered sea ice, melt-season sea ice, snow-covered tundra, and tundra shortly after snowmelt were measured using an aircraft based, high angular resolution (1-degree) multispectral radiometer. Results indicate bidirectional reflectance is higher for snow-covered sea ice than melt-season sea ice at all wavelengths between 0.47 and 2.3 pm, with the difference increasing with wavelength. Bidirectional reflectance of snow-covered tundra is higher than for snow-free tundra for measurements less than 1.64 pm, with the difference decreasing with wavelength. Bidirectional reflectance patterns of all measured surfaces show maximum reflectance in the forward scattering direction of the principal plane, with identifiable specular reflection for the melt-season sea ice and snow-free tundra cases. The snow-free tundra had the most significant backscatter, and the melt-season sea ice the least. For sea ice, bidirectional reflectance changes due to snowmelt were more significant than differences among the different types of melt-season sea ice. Also the spectral-hemispherical (plane) albedo of each measured arctic surface was computed. Comparing measured nadir reflectance to albedo for sea ice and snow-covered tundra shows albedo underestimated 5-40%, with the largest bias at wavelengths beyond 1 pm. For snow-free tundra, nadir reflectance underestimates plane albedo by about 30-50%.

  15. Dynamics of Aboveground Phytomass of the Circumpolar Arctic Tundra During the Past Three Decades

    NASA Technical Reports Server (NTRS)

    Epstein, Howard E.; Raynolds, Martha K.; Walker, Donald A.; Bhatt, Uma S.; Tucker, Compton J.; Pinzon, Jorge E.

    2012-01-01

    Numerous studies have evaluated the dynamics of Arctic tundra vegetation throughout the past few decades, using remotely sensed proxies of vegetation, such as the normalized difference vegetation index (NDVI). While extremely useful, these coarse-scale satellite-derived measurements give us minimal information with regard to how these changes are being expressed on the ground, in terms of tundra structure and function. In this analysis, we used a strong regression model between NDVI and aboveground tundra phytomass, developed from extensive field-harvested measurements of vegetation biomass, to estimate the biomass dynamics of the circumpolar Arctic tundra over the period of continuous satellite records (1982-2010). We found that the southernmost tundra subzones (C-E) dominate the increases in biomass, ranging from 20 to 26%, although there was a high degree of heterogeneity across regions, floristic provinces, and vegetation types. The estimated increase in carbon of the aboveground live vegetation of 0.40 Pg C over the past three decades is substantial, although quite small relative to anthropogenic C emissions. However, a 19.8% average increase in aboveground biomass has major implications for nearly all aspects of tundra ecosystems including hydrology, active layer depths, permafrost regimes, wildlife and human use of Arctic landscapes. While spatially extensive on-the-ground measurements of tundra biomass were conducted in the development of this analysis, validation is still impossible without more repeated, long-term monitoring of Arctic tundra biomass in the field.

  16. 50 CFR 20.107 - Seasons, limits, and shooting hours for tundra swans.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... section, see the List of CFR Sections Affected, which appears in the Finding Aids section of the printed... tundra swans. 20.107 Section 20.107 Wildlife and Fisheries UNITED STATES FISH AND WILDLIFE SERVICE..., and Shooting Hours Schedules § 20.107 Seasons, limits, and shooting hours for tundra swans....

  17. 50 CFR 20.107 - Seasons, limits, and shooting hours for tundra swans.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... section, see the List of CFR Sections Affected, which appears in the Finding Aids section of the printed... tundra swans. 20.107 Section 20.107 Wildlife and Fisheries UNITED STATES FISH AND WILDLIFE SERVICE..., and Shooting Hours Schedules § 20.107 Seasons, limits, and shooting hours for tundra swans....

  18. 50 CFR 20.107 - Seasons, limits, and shooting hours for tundra swans.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... section, see the List of CFR Sections Affected, which appears in the Finding Aids section of the printed... tundra swans. 20.107 Section 20.107 Wildlife and Fisheries UNITED STATES FISH AND WILDLIFE SERVICE..., and Shooting Hours Schedules § 20.107 Seasons, limits, and shooting hours for tundra swans....

  19. 50 CFR 20.107 - Seasons, limits, and shooting hours for tundra swans.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... section, see the List of CFR Sections Affected, which appears in the Finding Aids section of the printed... tundra swans. 20.107 Section 20.107 Wildlife and Fisheries UNITED STATES FISH AND WILDLIFE SERVICE..., and Shooting Hours Schedules § 20.107 Seasons, limits, and shooting hours for tundra swans....

  20. 50 CFR 20.107 - Seasons, limits, and shooting hours for tundra swans.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... section, see the List of CFR Sections Affected, which appears in the Finding Aids section of the printed... tundra swans. 20.107 Section 20.107 Wildlife and Fisheries UNITED STATES FISH AND WILDLIFE SERVICE..., and Shooting Hours Schedules § 20.107 Seasons, limits, and shooting hours for tundra swans....

  1. Hydroponic root mats for wastewater treatment-a review.

    PubMed

    Chen, Zhongbing; Cuervo, Diego Paredes; Müller, Jochen A; Wiessner, Arndt; Köser, Heinz; Vymazal, Jan; Kästner, Matthias; Kuschk, Peter

    2016-08-01

    Hydroponic root mats (HRMs) are ecotechnological wastewater treatment systems where aquatic vegetation forms buoyant filters by their dense interwoven roots and rhizomes, sometimes supported by rafts or other floating materials. A preferential hydraulic flow is created in the water zone between the plant root mat and the bottom of the treatment system. When the mat touches the bottom of the water body, such systems can also function as HRM filter; i.e. the hydraulic flow passes directly through the root zone. HRMs have been used for the treatment of various types of polluted water, including domestic wastewater; agricultural effluents; and polluted river, lake, stormwater and groundwater and even acid mine drainage. This article provides an overview on the concept of applying floating HRM and non-floating HRM filters for wastewater treatment. Exemplary performance data are presented, and the advantages and disadvantages of this technology are discussed in comparison to those of ponds, free-floating plant and soil-based constructed wetlands. Finally, suggestions are provided on the preferred scope of application of HRMs. PMID:27164889

  2. Summertime CO2 fluxes and ecosystem respiration from marine animal colony tundra in maritime Antarctica

    NASA Astrophysics Data System (ADS)

    Zhu, Renbin; Bao, Tao; Wang, Qing; Xu, Hua; Liu, Yashu

    2014-12-01

    Net ecosystem CO2 exchange (NEE) and ecosystem respiration (ER) were investigated at penguin, seal and skua colony tundra and the adjacent animal-lacking tundra sites in maritime Antarctica. Net CO2 fluxes showed a large difference between marine animal colonies and animal-lacking tundra sites. The mean NEE from penguin, seal and skua colony tundra sites ranged from -37.2 to 5.2 mg CO2 m-2 h-1, whereas animal-lacking tundra sites experienced a larger net gain of CO2 with the mean flux range from -85.6 to -23.9 mg CO2 m-2 h-1. Ecosystem respiration rates at penguin colony tundra sites (mean 201.3 ± 31.4 mg CO2 m-2 h-1) were significantly higher (P < 0.01) than those at penguin-lacking tundra sites (64.0-87.1 mg CO2 m-2 h-1). The gross photosynthesis (Pg) showed a consistent trend to ER with the highest mean Pg (219.7 ± 34.5 mg CO2 m-2 h-1) at penguin colony tundra sites. When all the data were combined from different types of tundra ecosystems, summertime tundra NEE showed a weak or strong positive correlation with air temperature, 0-10 cm soil temperature or precipitation. The NEE from marine animal colony and animal-lacking tundra was significantly positively correlated (P < 0.001) with soil organic carbon (SOC), total nitrogen (TN) contents and C:N ratios. The ER showed a significant exponential correlation (P < 0.01) with mean 0-15 cm soil temperature, and much higher Q10 value (9.97) was obtained compared with other terrestrial ecosystems, indicating greater temperature sensitivity of tundra ecosystem respiration. Our results indicate that marine animals and the deposition of their excreta might have an important effect on tundra CO2 exchanges and ecosystem respiration, and current climate warming will further decrease tundra CO2 sink in maritime Antarctica.

  3. Long-Term Release of Carbon Dioxide from Arctic Tundra Ecosystems in Northern Alaska

    NASA Astrophysics Data System (ADS)

    Euskirchen, E. S.; Bret-Harte, M. S.; Edgar, C.; Shaver, G. R.

    2014-12-01

    Recent data syntheses and modeling studies of arctic tundra carbon dioxide (CO2) balance have suggested that the tundra is a CO2 sink, a source or neutral. Much of this uncertainty arises from a lack of data pertaining to winter CO2 flux, as well as how these ecosystems have responded to recent warming trends. Due to a harsh, remote environment, long-term, continuous measurements of arctic tundra CO2 fluxes over the full annual cycle have been non-existent. In September 2007, we began eddy covariance measurements of net ecosystem exchange (NEE, where a negative value denotes a sink) of CO2 in northern Alaska at two ecosystems, heath and wet sedge tundra. These measurements continue to the present, and represent the longest continuous record of arctic tundra NEE currently available. From January 2008 - December 2013, the ecosystems were annual sources of CO2, with the wet sedge tundra acting as a greater source (mean ± standard deviation of 50 ± 30 g C m-2 y-1) than the heath tundra (16 ± 6 g C m-2 y-1). During these same years, the ecosystems were sinks of CO2 in the summer (June - August), with less variability between the ecosystems, -77 ± 15 g C m-2 in the wet sedge tundra, and -70 ± 12 g C m-2 in the heath. Environmental controls over NEE differed between ecosystems and seasons, with the wet sedge tundra acting particularly responsive in terms of CO2 release during periods with warm air temperatures from fall to early winter. During cold winter periods, CO2 release from the snowpack in both ecosystems was related to increases in wind speed and drops in atmospheric pressure. Overall, the measured differences in the annual versus summer NEE illustrate how the sink strength of the tundra can be overestimated if data are only collected during the growing season. Furthermore, eddy covariance measurements of methane (CH4) in the wet sedge tundra during late spring to early fall from 2012 to present show that this ecosystem releases 0.34 ± 11 mg CH4 m-2 d-1

  4. Identifying nitrogen limitations to organic sediments accumulation in various vegetation types of arctic tundra (Hornsund, Svalbard)

    NASA Astrophysics Data System (ADS)

    Skrzypek, G.; Wojtuń, B.; Hua, Q.; Richter, D.; Jakubas, D.; Wojczulanis-Jakubas, K.; Samecka-Cymerman, A.

    2015-12-01

    Arctic and subarctic regions play important roles in the global carbon balance. However, nitrogen (N) deficiency is a major constraint for organic carbon sequestration in the High Arctic. Hence, the identification of the relative contributions from different N-sources is critical for understanding the constraints that limit tundra growth. The stable nitrogen composition of the three main N-sources and numerous plants were analyzed in ten tundra types in the Fuglebekken catchment (Hornsund Fjord, Svalbard, 77°N 15°E). The percentage of the total tundra N-pool provided by seabirds' feces (colonially breeding, planktivorous Alle alle), ranged from 0-21% in Patterned-ground tundra to 100% in Ornithocoprophilous tundra. The total N-pool utilized by tundra plants in the studied catchment was built in 36% by birds, 38% by atmospheric deposition, and 26% by N2-fixation. The results clearly show that N-pool in the tundra is significantly supplemented by nesting seabirds. Thus, if they experienced substantial negative environmental pressure associated with climate change, it would adversely influence the tundra N-budget [1]. The growth rates and the sediment thickness (<15 cm) in different tundra types varied considerably but the tundra age was similar, <450 cal BP. The only exception was Ornithocoprophilous tundra with very diverse ages ranging from 235 to 2300 cal BP and thickness up to 110cm. The growth rates for this tundra (62 cm core, 18 AMS 14C dates) were high (1.5-3.0 mm/yr) between 1568 and 1804 AD and then substantially declined for the period between 1804 and 1929 AD (0.2 mm/yr). These findings deliver an additional argument, that the organic matter accumulation is driven not only directly by climatic conditions but also by birds' contribution to the tundra N-pool. [1] Skrzypek G, Wojtuń B, Richter D, Jakubas D, Wojczulanis-Jakubas K, Samecka-Cymerman A, 2015. Diversification of nitrogen sources in various tundra vegetation types in the high Arctic. PLoS ONE

  5. Spatial Heterogeneity in Arctic Tundra Snow: Processes, Patterns, and Problems

    NASA Astrophysics Data System (ADS)

    Sturm, M.; Liston, G. E.; Wagner, A. M.; Hiemstra, C. A.

    2014-12-01

    Tundra snow (exclusive of drifts) tends to be a thin veneer (<1 m) modified by extensive aeolian features like dunes and barchans. These features are on the order of 0.2 to 1.0 m high, and the substrate beneath the veneer snow (often various types of tundra) can have similar local relief. Consequently, veneer snow depths exhibit a high degree of spatial heterogeneity. Lateral variations of depth as high as 50% or more can be observed over a few meters. Even greater depth variations occur where the topography creates traps that hold drifts as thick as 5 m. We have been measuring and modeling the tundra snow in a nested series of basins ranging from 1 to 200 km in northern Alaska for 30 years. These efforts show that while modeling can produce reasonably accurate simulations of the deeper drifts, in many cases it does not do a good job in capturing the more subtle aspects of the snow distribution, being hampered by limited precipitation and wind data. More accurate and detailed patterns of snow distribution can be revealed through direct measurement or through melt period sequential imagery. These can improve the accuracy of weather-driven model depth distributions, but producing pattern maps remains labor- and time-intensive. Both approaches tend to do poorly at scales of 100-m or less where surface features like sastrugi and dunes alter the snow depth. These small-scale variations in depth and snow water equivalent might not seem important, but comparison of point values of snow depth from observing stations with spatial maps of the snow surrounding the stations suggests that significant differences can exist. A more comprehensive understanding of drifting and drift features is needed in order to improve our ability to model and understand this dynamic and fascinating class of snow.

  6. Assessments of recent tundra change based on repeated vegetation surveys

    NASA Astrophysics Data System (ADS)

    Elmendorf, S.; Henry, G.; Thetundra Vegetation Change Group

    2010-12-01

    Results from experimental warming studies suggest tundra vegetation will respond rapidly and dramatically to climate warming, and indeed, NDVI data from remote sensing and repeat aerial photography suggest such changes may already be occurring. NDVI changes, however, may reflect responses to a variety of processes. Repeat measurements of permanently marked plots offer an invaluable opportunity to monitor detailed changes in vegetation composition and abundance. Here, we report results from a synthesis of repeat measurements of 195 permanent plots in Arctic and alpine tundra plant communities in North America (90 plots), Europe (82 plots), Asia (10 plots), Australia (12 plots), and Antarctica (1 plot) that were revisited at least twice between 1980 and 2010, with an average timespan of 13 years between first and last sampling periods. Annual air-temperature warming over the sampling period varied considerably among sites, ranging from slight cooling to increases of nearly 2°C per decade. In our preliminary analyses, we found significant tundra-wide increases in vegetation height as well as abundance of evergreen shrubs and graminoids, but declines in mosses. We anticipated that changes in vegetation height, abundance of deciduous shrubs, and percent of vegetated ground would be highest in areas where climate warming is occurring most rapidly, but found no support for these predictions in our observational dataset. It is possible that local vegetation dynamics in these areas are affected more by other longer-term non-equilibrium processes such as recovery from glaciation, or an alternative suite of local drivers, such as snow cover, precipitation, disturbance or herbivory.

  7. Cyanobacterial mats: Microanalysis of community metabolism

    NASA Technical Reports Server (NTRS)

    Cohen, Y.; Bermudes, D.; Fischer, U.; Haddad, R.; Prufert, L.; Scheulderman-Suylen, T.; Shaw, T.

    1985-01-01

    The microbial communities in two sites were studied using several approaches: (1) light microscopy; (2) the measurement of microprofiles of oxygen and sulfide at the surface of the microbial mat; (3) the study of diurnal variation of oxygen and sulfides; (4) in situ measurement of photosynthesis and sulfate reduction and study of the coupling of these two processes; (5) measurement of glutathione in the upper layers of the microbial mat as a possible oxygen quencher; (6) measurement of reduced iron as a possible intermediate electron donor along the established redoxcline in the mats; (7) measurement of dissolved phosphate as an indicator of processes of break down of organic matter in these systems; and (8) measurement of carbon dioxide in the interstitial water and its delta C-13 in an attempt to understand the flow of CO2 through the systems. Microbial processes of primary production and initial degradation at the most active zone of the microbial mat were analyzed.

  8. Tundra Fire Effects Mapping from Synthetic Aperture Radar Satellite Data

    NASA Astrophysics Data System (ADS)

    Jenkins, L. K.; Bourgeau-Chavez, L. L.; French, N. H.; Loboda, T. V.; Chavez, M. C.; Hawkins, S. M.

    2013-12-01

    Traditional electro-optical, satellite-based methods of fire detection and monitoring are severely limited in the arctic due to persistent cloud cover and short growing seasons. Radar data can provide an alternative to traditional electro-optical methods due to all-weather imaging capabilities. Previous research in boreal forests and current evaluation in the Alaskan tundra shows that synthetic aperture radar (SAR) data can be used successfully to map burn perimeters and distinguish burned and unburned areas within the perimeter over a longer period of time than optical sensors. Results will be presented on the use of SAR data to measure spatial variations in the microwave signature across a fire scar as well as temporally throughout the growing season and across multiple years. The extensive historical archive of ERS-1 and -2 SAR data has been used to characterize three burned areas in the tundra regions of Alaska. These fires include the 1993 Wainwright fires in the north-western part of the North Slope (Fig 1), the 1999 Uvgoon fire in the Noatak National Preserve and 2007 Anaktuvuk River fire north of the Brooks Range in the central area of the North Slope. The data record includes pre-burn, burn, and post-burn observations until the fire scars are no longer discernible on the landscape. Our results show that burned areas are visible reliably five years post burn and then faintly apparent thereafter up to 12 or more years post-burn. Conversely, our analysis of electro-optical (Landsat) imagery shows near complete obscuration of the fire scar one year post-burn (Loboda et al. 2013). Also presented are results of an analysis of the effects of post-fire soil moisture, as measured in weather and climate datasets, on the SAR signature measured from the available image data archive. Reference: Loboda, T L, N H F French, C Hight-Harf, L Jenkins, M E Miller. 2013. Mapping fire extent and burn severity in Alaskan tussock tundra: An analysis of the spectral response of

  9. Recovery of plant biomass and soil N cycling in Alaskan tundra following an unusual fire

    NASA Astrophysics Data System (ADS)

    Bret-Harte, M. S.; Mack, M. C.; Huebner, D. C.; Johnston, M.; Shaver, G. R.

    2012-12-01

    Climate warming is likely to increase the frequency of disturbances in the Arctic. The Anaktuvuk River fire of 2007 burned 1039 km2 of northern Alaskan tundra; this was unprecedented for this vegetation, which is clonal, slow-growing, and long-lived. We harvested plant biomass and soils from severely and moderately burned areas and controls in 2011 to assess recovery of plant productivity and soil N cycling four years after the fire. Biomass of vascular plants had recovered to nearly control levels in moderately burned areas, due primarily to resprouting by graminoids, particularly Eriophorum vaginatum. Graminoid biomass was actually greater in moderately burned tundra than in unburned tundra. Deciduous shrub and evergreen shrub biomass in moderately burned tundra was approximately half that seen in unburned tundra, but non-vascular plant biomass was much less, so that total aboveground biomass in moderately burned tundra had not returned to control levels. Severely burned tundra had less of all components of the community than in moderately burned tundra, except that there was higher biomass of non-vascular plants, due to colonization by fire-following liverworts and mosses. Productivity of vascular plants was similar in unburned and severely burned tundra plots, and higher in moderately burned plots, due in part to higher soil N availability. Recovery of plant biomass was largely due to resprouting of species that survived the fire, though numerous seedlings were seen. Biomass of vascular plants has recovered rapidly in the moderately burned sites, while severely burned sites and nonvascular plants are recovering more slowly, but the relative abundance of different species differs from unburned tundra. The relationship between spectral indices (NDVI, EVI-2) collected at the plot level and either biomass or NPP varied with burn category, which may complicate assessments of NPP by remote sensing following fire.

  10. Nonwoven filtration mat production by electrospinning method

    NASA Astrophysics Data System (ADS)

    Lackowski, M.; Krupa, A.; Jaworek, A.

    2011-06-01

    The filtration of nanoparticles and submicron particles is an important problem in industry and health protection. One of the methods which can be used to solve this problem is to use nonwoven nanofibrous filters. The process of producing filtration mats of different thickness by electrospinning is presented in the paper. The experimental results on filtration properties of nanofibrous filter mat, including the efficiency of removal of cigarette smoke particles from a gas are also presented.

  11. Mattingly and Hartsfield Salute President Regan

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Columbia Space Shuttle astronauts Commander Thomas K. Mattingly, foreground, and Pilot Henry W. Hartsfield salute President Ronald Reagan and his wife, Nancy, as the astronauts begin the customary walk-around inspection of the orbiter after landing. Mattingly and Hartsfield were the first to land the Shuttle on a concrete runway. The landing proved that the shuttle could return safely to a precisely targeted location on Earth.

  12. Microbial Diversity and Lipid Abundance in Microbial Mats from a Sulfidic, Saline, Warm Spring in Utah, USA

    NASA Astrophysics Data System (ADS)

    Gong, J.; Edwardson, C.; Mackey, T. J.; Dzaugis, M.; Ibarra, Y.; Course 2012, G.; Frantz, C. M.; Osburn, M. R.; Hirst, M.; Williamson, C.; Hanselmann, K.; Caporaso, J.; Sessions, A. L.; Spear, J. R.

    2012-12-01

    The microbial diversity of Stinking Springs, a sulfidic, saline, warm spring northeast of the Great Salt Lake was investigated. The measured pH, temperature, salinity, and sulfide concentration along the flow path ranged from 6.64-7.77, 40-28° C, 2.9-2.2%, and 250 μM to negligible, respectively. Five sites were selected along the flow path and within each site microbial mats were dissected into depth profiles based on the color and texture of the mat layers. Genomic DNA was extracted from each layer, and the 16S rRNA gene was amplified and sequenced on the Roche 454 Titanium platform. Fatty acids were also extracted from the mat layers and analyzed by liquid chromatography and mass spectrometry. The mats at Stinking Springs were classified into roughly two morphologies with respect to their spatial distribution: loose, sometimes floating mats proximal to the spring source; and thicker, well-laminated mats distal to the spring source. Loosely-laminated mats were found in turbulent stream flow environments, whereas well-laminated mats were common in less turbulent sheet flows. Phototrophs, sulfur oxidizers, sulfate reducers, methanogens, other bacteria and archaea were identified by 16S rRNA gene sequences. Diatoms, identified by microscopy and lipid analysis were found to increase in abundance with distance from the source. Methanogens were generally more abundant in deeper mat laminae. Photoheterotrophs were found in all mat layers. Microbial diversity increased significantly with depth at most sites. In addition, two distinct microbial streamers were identified and characterized at the two fast flowing sites. These two streamer varieties were dominated by either cyanobacteria or flavobacteria. Overall, our genomic and lipid analysis suggest that the physical and chemical environment is more predictive of the community composition than mat morphology. Site Map

  13. Exploring defocus matting: nonparametric acceleration, super-resolution, and off-center matting.

    PubMed

    Joshi, Neel; Matusik, Wojciech; Avidan, Shai; Pfister, Hanspeter; Freeman, William T

    2007-01-01

    Defocus matting is a fully automatic and passive method for pulling mattes from video captured with coaxial cameras that have different depths of field and planes of focus. Nonparametric sampling can accelerate the video-matting process from minutes to seconds per frame. In addition a super-resolution technique efficiently bridges the gap between mattes from high-resolution video cameras and those from low-resolution cameras. Off-center matting pulls mattes for an external high-resolution camera that doesn't share the same center of projection as the low-resolution cameras used to capture the defocus matting data. PMID:17388202

  14. Eukaryotes in Arctic and Antarctic cyanobacterial mats.

    PubMed

    Jungblut, Anne D; Vincent, Warwick F; Lovejoy, Connie

    2012-11-01

    Cyanobacterial mats are commonly found in freshwater ecosystems throughout the polar regions. Most mats are multilayered three-dimensional structures with the filamentous cyanobacteria embedded in a gel-like matrix. Although early descriptions mentioned the presence of larger organisms including metazoans living in the mats, there have been few studies specifically focused on the microbial eukaryotes, which are often small cells with few morphological features suitable for identification by microscopy. Here, we applied 18S rRNA gene clone library analysis to identify eukaryotes in cyanobacterial mat communities from both the Antarctic and the extreme High Arctic. We identified 39 ribotypes at the level of 99% sequence similarity. These consisted of taxa within algal and other protist groups including Chlorophyceae, Prasinophyceae, Ulvophyceae, Trebouxiophyceae, Bacillariophyceae, Chrysophyceae, Ciliophora, and Cercozoa. Fungi were also recovered, as were 21 metazoan ribotypes. The eukaryotic taxa appeared habitat-specific with little overlap between lake, pond, and ice shelf communities. Some ribotypes were common to both Arctic and Antarctic mats, suggesting global dispersal of these taxa and similarity in the environmental filters acting on protist communities. Many of these eukaryotic taxa likely benefit from protected, nutrient-rich microhabitats within the cyanobacterial mat environment. PMID:22630054

  15. Cloning of mating-type gene MAT1-1 from the caterpillar medicinal mushroom, Cordyceps militaris (Ascomycetes) using TAIL-PCR technology.

    PubMed

    Cong, Wei-Ran; Gong, Zhen-Hua; Shi, Dan-Dan; Guo, Hui; Zhou, Xuanwei

    2014-01-01

    Cordyceps militaris and Ophiocordyceps sinensis (syn. Cordyceps sinensis), 2 well-known traditional Chinese medicines, contain the same bioactive components and share a similar developmental process. In this study, one C. militaris strain preserved in our laboratory was proven to be a MAT1 mating-type strain using a polymerase chain reaction-based mating-type assay. A 5000-bp nucleotide sequence of the mating-type MAT1-1 from C. militaris was amplified by thermal asymmetric interlaced polymerase chain reaction, but genes within the mating-type MAT1-2 remain undetectable. Sequence analysis shows that the mating-type gene MAT1-1 idiomorph contains 2 genes, MAT1-1-1 and MAT1-1-2. The MAT1-1-1 gene consists of 1480-bp nucleotides that encode 456 amino acids and contain the conserved a-box domain interrupted by 2 introns; the MAT1-1-2 gene consists of 1066 nucleotides that encode 377 amino acids interrupted by one intron. The intervening distance between MAT1-1-1 and MAT1-1-2 is 778 bp. The C. militaris MAT1-1 idiomorph organization is the same as that of Cordyceps takaomontana. The MAT1-1 mating-type idiomorph of both Cordyceps species lacks the MAT1-1-3 gene, which is typically present in Pyrenomycetes. These studies provide some insights for further study of the morphological development of C. militaris and will eventually benefit the domestication of O. sinensis. PMID:25271980

  16. Enhanced dechlorination of trichloroethylene using electrospun polymer nanofibrous mats immobilized with iron/palladium bimetallic nanoparticles.

    PubMed

    Ma, Hui; Huang, Yunpeng; Shen, Mingwu; Guo, Rui; Cao, Xueyan; Shi, Xiangyang

    2012-04-15

    Fe/Pd bimetallic nanoparticles (NPs) have held great promise for treating trichloroethylene (TCE)-contaminated groundwater, without the accumulation of chlorinated intermediates. However, the conventionally used colloidal Fe/Pd NPs usually aggregate rapidly, resulting in a reduced reactivity. To reduce the particle aggregation, we employed electrospun polyacrylic acid (PAA)/polyvinyl alcohol (PVA) polymer nanofibers as a nanoreactor to immobilize Fe/Pd bimetallic NPs. In the study, the water-stable PAA/PVA nanofibrous mats were complexed with Fe (III) ions via the binding with the free carboxyl groups of PAA for subsequent formation and immobilization of zero-valent iron (ZVI) NPs. Fe/Pd bimetallic NPs were then formed by the partial reduction of Pd(II) ions with ZVI NPs. The formed electrospun nanofibrous mats containing Fe/Pd bimetallic NPs with a diameter of 2.8 nm were characterized by scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, thermogravimetric analysis, and inductively coupled plasma-atomic emission spectroscopy. The Fe/Pd NP-containing electrospun PAA/PVA nanofibrous mats exhibited higher reactivity than that of the ZVI NP-containing mats or colloidal Fe/Pd NPs in the dechlorination of trichloroethylene (TCE), which was used as a model contaminant. With the high surface area to volume ratio, high porosity, and great reusability of the fibrous mats immobilized with the bimetallic NPs, the composite nanofibrous mats should be amenable for applications in remediation of various environmental contaminants. PMID:22138171

  17. Permafrost degradation stimulates carbon loss from experimentally warmed tundra.

    PubMed

    Natali, Susan M; Schuur, Edward A G; Webb, Elizabeth E; Pries, Caitlin E Hicks; Crummer, Kathryn G

    2014-03-01

    A large pool of organic carbon (C) has been accumulating in the Arctic for thousands of years because cold and waterlogged conditions have protected soil organic material from microbial decomposition. As the climate warms this vast and frozen C pool is at risk of being thawed, decomposed, and released to the atmosphere as greenhouse gasses. At the same time, some C losses may be offset by warming-mediated increases in plant productivity. Plant and microbial responses to warming ultimately determine net C exchange from ecosystems, but the timing and magnitude of these responses remain uncertain. Here we show that experimental warming and permafrost (ground that remains below 0 degrees C for two or more consecutive years) degradation led to a two-fold increase in net ecosystem C uptake during the growing season. However, warming also enhanced winter respiration, which entirely offset growing-season C gains. Winter C losses may be even higher in response to actual climate warming than to our experimental manipulations, and, in that scenario, could be expected to more than double overall net C losses from tundra to the atmosphere. Our results highlight the importance of winter processes in determining whether tundra acts as a C source or sink, and demonstrate the potential magnitude of C release from the permafrost zone that might be expected in a warmer climate. PMID:24804439

  18. Climate sensitivity of shrub growth across the tundra biome

    NASA Astrophysics Data System (ADS)

    Myers-Smith, Isla H.; Elmendorf, Sarah C.; Beck, Pieter S. A.; Wilmking, Martin; Hallinger, Martin; Blok, Daan; Tape, Ken D.; Rayback, Shelly A.; Macias-Fauria, Marc; Forbes, Bruce C.; Speed, James D. M.; Boulanger-Lapointe, Noémie; Rixen, Christian; Lévesque, Esther; Schmidt, Niels Martin; Baittinger, Claudia; Trant, Andrew J.; Hermanutz, Luise; Collier, Laura Siegwart; Dawes, Melissa A.; Lantz, Trevor C.; Weijers, Stef; Jørgensen, Rasmus Halfdan; Buchwal, Agata; Buras, Allan; Naito, Adam T.; Ravolainen, Virve; Schaepman-Strub, Gabriela; Wheeler, Julia A.; Wipf, Sonja; Guay, Kevin C.; Hik, David S.; Vellend, Mark

    2015-09-01

    Rapid climate warming in the tundra biome has been linked to increasing shrub dominance. Shrub expansion can modify climate by altering surface albedo, energy and water balance, and permafrost, yet the drivers of shrub growth remain poorly understood. Dendroecological data consisting of multi-decadal time series of annual shrub growth provide an underused resource to explore climate-growth relationships. Here, we analyse circumpolar data from 37 Arctic and alpine sites in 9 countries, including 25 species, and ~42,000 annual growth records from 1,821 individuals. Our analyses demonstrate that the sensitivity of shrub growth to climate was: (1) heterogeneous, with European sites showing greater summer temperature sensitivity than North American sites, and (2) higher at sites with greater soil moisture and for taller shrubs (for example, alders and willows) growing at their northern or upper elevational range edges. Across latitude, climate sensitivity of growth was greatest at the boundary between the Low and High Arctic, where permafrost is thawing and most of the global permafrost soil carbon pool is stored. The observed variation in climate-shrub growth relationships should be incorporated into Earth system models to improve future projections of climate change impacts across the tundra biome.

  19. Tundra carbon balance under varying temperature and moisture regimes

    NASA Astrophysics Data System (ADS)

    Huemmrich, K. F.; Kinoshita, G.; Gamon, J. A.; Houston, S.; Kwon, H.; Oechel, W. C.

    2010-12-01

    To understand the effects of environmental change on tundra carbon balance, a manipulation experiment was performed in wet sedge tundra near Barrow, Alaska. Three replicates of six environmental treatments were made: control, heating, raising or lowering water table, and heating along with raising or lowering water table. Carbon fluxes were measured using a portable chamber for six days during the 2001 growing season. Spectral reflectance and meteorological measurements were also collected. Empirical models derived from flux measurements were developed for daily gross ecosystem production (GEP) and ecosystem respiration (Re). The amount of photosynthetically active radiation absorbed by the plants was strongly correlated with GEP. This relationship was not affected by treatment or time during the growing season. Re was related to soil temperature with a different relationship for each water level treatment. Re in the lowered water table treatment had a strong response to temperature changes, while the raised water table treatment showed little temperature response. These models calculated daily net ecosystem exchange for all of the treatments over the growing season. Warming increased both the seasonal carbon gain and carbon loss. By the end of summer the lowered water table treatments, both heated and unheated, were net carbon sources while all other treatments were sinks. Warming and/or raising the water table increased the strength of the net sink. Over the timescale of this experiment, water table primarily determined whether the ecosystem was a source or sink, with temperature modifying the strength of the source or sink.

  20. Can antibrowsing defense regulate the spread of woody vegetation in arctic tundra?

    USGS Publications Warehouse

    Bryant, John P.; Joly, Kyle; Chapin, F. Stuart, III; DeAngelis, Donald L.; Kielland, Knut

    2014-01-01

    Global climate warming is projected to promote the increase of woody plants, especially shrubs, in arctic tundra. Many factors may affect the extent of this increase, including browsing by mammals. We hypothesize that across the Arctic the effect of browsing will vary because of regional variation in antibrowsing chemical defense. Using birch (Betula) as a case study, we propose that browsing is unlikely to retard birch expansion in the region extending eastward from the Lena River in central Siberia across Beringia and the continental tundra of central and eastern Canada where the more effectively defended resin birches predominate. Browsing is more likely to retard birch expansion in tundra west of the Lena to Fennoscandia, Iceland, Greenland and South Baffin Island where the less effectively defended non-resin birches predominate. Evidence from the literature supports this hypothesis. We further suggest that the effect of warming on the supply of plant-available nitrogen will not significantly change either this pan-Arctic pattern of variation in antibrowsing defense or the resultant effect that browsing has on birch expansion in tundra. However, within central and east Beringia warming-caused increases in plant-available nitrogen combined with wildfire could initiate amplifying feedback loops that could accelerate shrubification of tundra by the more effectively defended resin birches. This accelerated shrubification of tundra by resin birch, if extensive, could reduce the food supply of caribou causing population declines. We conclude with a brief discussion of modeling methods that show promise in projecting invasion of tundra by woody plants.

  1. Frequent fires in ancient shrub tundra: implications of paleorecords for arctic environmental change.

    PubMed

    Higuera, Philip E; Brubaker, Linda B; Anderson, Patricia M; Brown, Thomas A; Kennedy, Alison T; Hu, Feng Sheng

    2008-01-01

    Understanding feedbacks between terrestrial and atmospheric systems is vital for predicting the consequences of global change, particularly in the rapidly changing Arctic. Fire is a key process in this context, but the consequences of altered fire regimes in tundra ecosystems are rarely considered, largely because tundra fires occur infrequently on the modern landscape. We present paleoecological data that indicate frequent tundra fires in northcentral Alaska between 14,000 and 10,000 years ago. Charcoal and pollen from lake sediments reveal that ancient birch-dominated shrub tundra burned as often as modern boreal forests in the region, every 144 years on average (+/- 90 s.d.; n = 44). Although paleoclimate interpretations and data from modern tundra fires suggest that increased burning was aided by low effective moisture, vegetation cover clearly played a critical role in facilitating the paleofires by creating an abundance of fine fuels. These records suggest that greater fire activity will likely accompany temperature-related increases in shrub-dominated tundra predicted for the 21(st) century and beyond. Increased tundra burning will have broad impacts on physical and biological systems as well as on land-atmosphere interactions in the Arctic, including the potential to release stored organic carbon to the atmosphere. PMID:18320025

  2. Succession Stages of Tundra Plant Communities Following Wildfire Disturbance in Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Breen, A. L.; Hollingsworth, T. N.; Mack, M. C.; Jones, B. M.

    2015-12-01

    Rapid climate change is affecting climate-sensitive disturbance regimes throughout the world. In particular, the impacts of climate change on Arctic disturbance regimes are poorly understood because landscape-scale disturbances are infrequent or occur in remote localities. Wildfire in Arctic Alaska is presently limited by ignition source and favorable burn weather. With rapid climate change, a lengthening growing season, and subsequent increase in plant biomass and productivity, wildfire frequency and annual area burned in tundra ecosystems is expected to increase over the next century. Yet, post-fire tundra vegetation succession is inadequately characterized except at a few point locations. We identify succession stages of tussock tundra communities following wildfire using a chronosequence of 65 relevés in 10 tundra fire scars (1971-2011) and nearby unburned tundra from sites on the Seward Peninsula and northern foothills of the Brooks Range. We used the Braun-Blanquét approach to classify plant communities, and applied nonmetric multidimentional scaling (NMDS) to identify ecological gradients underlying community differentiation. The ordination revealed a clear differentiation between unburned and burned tundra communities. Ecological gradients, reflected by ordination axes, correspond to fire history (e.g., time since last fire, number of times burned, burn severity) and a complex productivity gradient. Post-fire species richness is less than unburned tundra; primarily reflected as a decrease in lichen species and turnover of bryophyte species immediately post-fire. Species richness of grasses increases post-fire and is greatest in communities that burned more than once in the past 30 years. Shrub cover and total aboveground biomass are greatest in repeat burn sites. We review and discuss our results focusing on the implications of a changing tundra fire regime, its effect on vegetation succession trajectories, and subsequent rates of carbon sequestration and

  3. Late-Summer Tundra Methane Concentrations and Fluxes on the North Slope of Alaska

    NASA Astrophysics Data System (ADS)

    Smith, J. P.; Suriben, R. S.; Coffin, R. B.; Boyd, T. J.; Rose, P. S.; Douglas, T. A.; Millholland, L. C., IV; Boudart, E. R.; Woods, J. E.

    2014-12-01

    Scientific evidence indicates wide-scale changes in Arctic climate. The Arctic contains large expanses of tundra with permafrost, or permanently frozen subsoil. Climate change impacts on the tundra have the potential to enhance biogenic methane (CH4) production in thawed, active soils or release CH4 trapped in or below the permafrost. Methane is a highly effective greenhouse gas so CH4 released from thawing tundra or melting massive ice features constitutes a potential positive feedback to Arctic climate change. In August, 2013 the U.S. Naval Research Laboratory (NRL-6114) led an expedition to investigate late-summer tundra CH4 concentrations and fluxes on the North Slope of Alaska near Prudhoe Bay. Permafrost cores were collected to measure tundra CH4 concentrations and soil parameters and a series of gas traps were deployed to measure tundra CH4 flux at 9 locations spread across a study area of ~1800 km2. Thaw probe measurements at each site provided information on the depth of the seasonally-thawed (active) layer. Results show large differences in tundra CH4 concentrations with depth through the active layer and into the upper permafrost terrain and fine-scale variability in daily CH4 flux over a relatively small spatial area. It is likely that variations in biogeochemical and geomorphological characteristics such as soil composition, microbial activity, moisture type, active layer composition and extent from site-to-site control the CH4 regime. In order to provide more accurate estimates of permafrost tundra CH4 storage and fluxes, controls on CH4 variability from location to location must be better understood. Further research is required to quantify and predict tundra CH4 flux in order to better understand the potential impact it will have on Arctic climate, particularly if, as predicted, climate warming leads to the liberation of permafrost carbon in these landscapes.

  4. Lipids of recently-deposited algal mats at Laguna Mormona, Baja California

    NASA Technical Reports Server (NTRS)

    Cardoso, J.; Brooks, P. W.; Eglinton, G.; Goodfellow, R.; Maxwell, J. R.; Philp, R. P.

    1976-01-01

    A preliminary survey of the lipid composition of the core of a recently deposited algal mat of a subtropical, hypersaline coastal pond is described. Two layers of the core were examined: the upper, 2-cm-thick layer, comprising the fresh algal mat of predominantly the blue-green species Microcoleus chthonoplastes, and the black anaerobic algal ooze at a depth of 10 cm. About 75% of the n-alkanes in the mat were accounted for by n-C17, with smaller amounts of higher homologues maximizing at n-C27. The ooze was characterized by a bimodal distribution with maxima at n-C17 and n-C27. The n-alkanoic acids distributions were similar to the corresponding n-alkane distributions. A marked decrease in the ratio of monounsaturated to saturated acids in the ooze relative to the mat was observed, which indicates a preferential removal of unsaturated components. Certain triterpenes of the hopane skeletal type were present in the mat and ooze. The presence of stanols and sterenes in the ooze with similar carbon number distributions suggests a relationship between them.

  5. The Effect of Silver Nanoparticles on Seasonal Change in Arctic Tundra Bacterial and Fungal Assemblages

    PubMed Central

    Kumar, Niraj; Palmer, Gerald R.; Shah, Vishal; Walker, Virginia K.

    2014-01-01

    The impact of silver nanoparticles (NPs) and microparticles (MPs) on bacterial and fungal assemblages was studied in soils collected from a low arctic site. Two different concentrations (0.066% and 6.6%) of Ag NPs and Ag MPs were tested in microcosms that were exposed to temperatures mimicking a winter to summer transition. Toxicity was monitored by differential respiration, phospholipid fatty acid analysis, polymerase chain reaction-denaturing gradient gel electrophoresis and DNA sequencing. Notwithstanding the effect of Ag MPs, nanosilver had an obvious, additional impact on the microbial community, underscoring the importance of particle size in toxicity. This impact was evidenced by levels of differential respiration in 0.066% Ag NP-treated soil that were only half that of control soils, a decrease in signature bacterial fatty acids, and changes in both richness and evenness in bacterial and fungal DNA sequence assemblages. Prominent after Ag NP-treatment were Hypocreales fungi, which increased to 70%, from only 1% of fungal sequences under control conditions. Genera within this Order known for their antioxidant properties (Cordyceps/Isaria) dominated the fungal assemblage after NP addition. In contrast, sequences attributed to the nitrogen-fixing Rhizobiales bacteria appeared vulnerable to Ag NP-mediated toxicity. This combination of physiological, biochemical and molecular studies clearly demonstrate that Ag NPs can severely disrupt the natural seasonal progression of tundra assemblages. PMID:24926877

  6. The effect of silver nanoparticles on seasonal change in arctic tundra bacterial and fungal assemblages.

    PubMed

    Kumar, Niraj; Palmer, Gerald R; Shah, Vishal; Walker, Virginia K

    2014-01-01

    The impact of silver nanoparticles (NPs) and microparticles (MPs) on bacterial and fungal assemblages was studied in soils collected from a low arctic site. Two different concentrations (0.066% and 6.6%) of Ag NPs and Ag MPs were tested in microcosms that were exposed to temperatures mimicking a winter to summer transition. Toxicity was monitored by differential respiration, phospholipid fatty acid analysis, polymerase chain reaction-denaturing gradient gel electrophoresis and DNA sequencing. Notwithstanding the effect of Ag MPs, nanosilver had an obvious, additional impact on the microbial community, underscoring the importance of particle size in toxicity. This impact was evidenced by levels of differential respiration in 0.066% Ag NP-treated soil that were only half that of control soils, a decrease in signature bacterial fatty acids, and changes in both richness and evenness in bacterial and fungal DNA sequence assemblages. Prominent after Ag NP-treatment were Hypocreales fungi, which increased to 70%, from only 1% of fungal sequences under control conditions. Genera within this Order known for their antioxidant properties (Cordyceps/Isaria) dominated the fungal assemblage after NP addition. In contrast, sequences attributed to the nitrogen-fixing Rhizobiales bacteria appeared vulnerable to Ag NP-mediated toxicity. This combination of physiological, biochemical and molecular studies clearly demonstrate that Ag NPs can severely disrupt the natural seasonal progression of tundra assemblages. PMID:24926877

  7. Changes in microbial communities along redox gradients in polygonized Arctic wet tundra soils.

    PubMed

    Lipson, David A; Raab, Theodore K; Parker, Melanie; Kelley, Scott T; Brislawn, Colin J; Jansson, Janet

    2015-08-01

    This study investigated how microbial community structure and diversity varied with depth and topography in ice wedge polygons of wet tundra of the Arctic Coastal Plain in northern Alaska and what soil variables explain these patterns. We observed strong changes in community structure and diversity with depth, and more subtle changes between areas of high and low topography, with the largest differences apparent near the soil surface. These patterns are most strongly correlated with redox gradients (measured using the ratio of reduced Fe to total Fe in acid extracts as a proxy): conditions grew more reducing with depth and were most oxidized in shallow regions of polygon rims. Organic matter and pH also changed with depth and topography but were less effective predictors of the microbial community structure and relative abundance of specific taxa. Of all other measured variables, lactic acid concentration was the best, in combination with redox, for describing the microbial community. We conclude that redox conditions are the dominant force in shaping microbial communities in this landscape. Oxygen and other electron acceptors allowed for the greatest diversity of microbes: at depth the community was reduced to a simpler core of anaerobes, dominated by fermenters (Bacteroidetes and Firmicutes). PMID:26034016

  8. Changes in microbial communities along redox gradients in polygonized Arctic wet tundra soils

    SciTech Connect

    Lipson, David A.; Raab, Theodore K.; Parker, Melanie; Kelley, Scott T.; Brislawn, Colin J.; Jansson, Janet K.

    2015-08-01

    Summary This study investigated how microbial community structure and diversity varied with depth and topography in ice wedge polygons of wet tundra of the Arctic Coastal Plain in northern Alaska and what soil variables explain these patterns. We observed strong changes in community structure and diversity with depth, and more subtle changes between areas of high and low topography, with the largest differences apparent near the soil surface. These patterns are most strongly correlated with redox gradients (measured using the ratio of reduced Fe to total Fe in acid extracts as a proxy): conditions grew more reducing with depth and were most oxidized in shallow regions of polygon rims. Organic matter and pH also changed with depth and topography but were less effective predictors of the microbial community structure and relative abundance of specific taxa. Of all other measured variables, lactic acid concentration was the best, in combination with redox, for describing the microbial community. We conclude that redox conditions are the dominant force in shaping microbial communities in this landscape. Oxygen and other electron acceptors allowed for the greatest diversity of microbes: at depth the community was reduced to a simpler core of anaerobes,

  9. Changes in microbial communities along redox gradients in polygonized Arctic wet tundra soils

    SciTech Connect

    Lipson, David A.; Raab, Theodore K.; Parker, Melanie; Kelley, Scott T.; Brislawn, Colin J.; Jansson, Janet K.

    2015-07-21

    This study investigated how microbial community structure and diversity varied with depth and topography in ice wedge polygons of wet tundra of the Arctic Coastal Plain in northern Alaska, and what soil variables explain these patterns. We observed strong changes in community structure and diversity with depth, and more subtle changes between areas of high and low topography, with the largest differences apparent near the soil surface. These patterns are most strongly correlated with redox gradients (measured using the ratio of reduced Fe to total Fe in acid extracts as a proxy): conditions grew more reducing with depth and were most oxidized in shallow regions of polygon rims. Organic matter and pH also changed with depth and topography, but were less effective predictors of the microbial community structure and relative abundance of specific taxa. Of all other measured variables, lactic acid concentration was the best, in combination with redox, for describing the microbial community. We conclude that redox conditions are the dominant force in shaping microbial communities in this landscape. Oxygen and other electron acceptors allowed for the greatest diversity of microbes: at depth the community was reduced to a simpler core of anaerobes, dominated by fermenters (Bacteroidetes and Firmicutes).

  10. The Tundra is a Net Source of CO2 Measured by Autochambers and Eddy Covariance Techniques During Five Years in a Site With Permafrost Thawing.

    NASA Astrophysics Data System (ADS)

    Celis, G.; Mauritz, M.; Bracho, R. G.; Salmon, V. G.; Webb, E.; Hutchings, J. A.; Natali, S.; Crummer, K. G.; Schuur, E.; Schaedel, C.

    2015-12-01

    Current and future warming of high latitude tundra ecosystems will play an important role in climate change through feedbacks to the global carbon (C) cycle. Long-term observational and experimental studies are pivotal for detecting and understanding changes in the coming decades. Yet studies of the C feedbacks from observational studies and manipulative experiments made on tundra plant communities often have significantly different conclusions with regards to impacts of warming on the ecosystem. Comparing results from these two study types, however, often involves integrating CO2 flux measurements that were collected on different spatial scales using a variety of methods. The process of data assimilation for landscape level analysis is often complicated by the fact that many projects only utilize one method for measuring CO2 fluxes at a given site. This study compares five years of C dynamics in a moist acidic tundra from control plots in a manipulative warming experiment (CiPEHR - plot-scale) and landscape-level natural permafrost thaw gradient (Gradient - Eddy covariance) observations all within a 1km distance from each other. We found net ecosystem exchange (NEE) to be an annual net source of carbon using both methods (Gradient 12.3 - 125.6 g CO2-C m-2 and CiPEHR warming manipulation 80.2 - 175.8 g CO2-C m-2). The differences between sites were biggest in the first three years of observation, and can be explained by lower growing season gross primary production (GPP - first three years) from the manipulation (CiPEHR), and lower ecosystem respiration (Reco) from CiPEHR in the first year only. Suppressed GPP and Reco could be from the impact of experimental setup (chamber soil collars - root damage), which lowered the plant community's capacity to fix C, but recovered within three years. This warrants caution of making generalization of short-term experiments in the tundra and more research is needed evaluating coupling of belowground and aboveground C dynamics.

  11. Remotely Sensing Tundra Fire Impacts Using InSAR

    NASA Astrophysics Data System (ADS)

    Liu, L.; Schaefer, K. M.; Jafarov, E. E.; Williams, C. A.; Rogan, J.; Zebker, H. A.

    2013-12-01

    Fire is a major disturbance affecting the arctic tundra and boreal forests, with a significant impacts on the ecosystem, soil hydrology, carbon cycling, and permafrost. The increasing trend in frequency and severity of large fires since 1980, associated with progressively drier conditions, is expected to continue and lead to still greater impacts. In this study, we explore the use of Interferometric Synthetic Aperture Radar (InSAR) to map and quantify several results of tundra fires, including fire severity, the increase in permafrost active layer thickness (ALT), and changes in organic layer thickness. Here we present as an example observations of the Anaktuvuk River fire on the North Slope of Alaska, which burned over 1,000 km2 of tundra in the summer of 2007. Fire causes an abrupt change in the surface scattering characteristics and results in a large drop in InSAR coherence. The magnitude of coherence loss is proportional to the amount of vegetation burned, and thus fire severity. Coherence between two PALSAR images taken by the Japanese ALOS satellite before and after the Anaktuvuk River fire shows a spatial pattern consistent with a map of burn severity based on optical MODIS images using differential Normalized Burn Ratio. Additionally, we used InSAR to calculate the seasonal ground subsidence for the 2006 and 2009 thaw seasons representing pre- and post-fire conditions, and estimated the change in ALT using a retrieval algorithm. Our results are consistent with the 8 to 24 cm ALT increases derived from in situ probing measurements, which we relate to the change in the organic layer thickness due to the fire. Our results illustrate the potential of InSAR for remote sensing of fire impacts in Arctic regions. (a) Burn severity for the Anaktuvuk Rivre Fire based on differential Normalized Burn Ratio (dNBR) from MODIS images. (b) Interferometric coherence loss due to the fire. Spatial mean has been subtracted. Negative values (yellow and red colors) indicate

  12. Climate Variations and Alaska Tundra Vegetation Productivity Declines in Spring

    NASA Astrophysics Data System (ADS)

    Bhatt, U. S.; Walker, D. A.; Bieniek, P.; Raynolds, M. K.; Epstein, H. E.; Comiso, J. C.; Pinzon, J. E.; Tucker, C. J.

    2015-12-01

    While sea ice has continued to decline, vegetation productivity increases have declined particularly during spring in Alaska as well as many parts of the Arctic tundra. To understand the processes behind these features we investigate spring climate variations that includes temperature, circulation patterns, and snow cover to determine how these may be contributing to spring browning. This study employs remotely sensed weekly 25-km sea ice concentration, weekly surface temperature, and bi-weekly NDVI from 1982 to 2014. Maximum NDVI (MaxNDVI, Maximum Normalized Difference Vegetation Index), Time Integrated NDVI (TI-NDVI), Summer Warmth Index (SWI, sum of degree months above freezing during May-August), atmospheric reanalysis data, dynamically downscaled climate data, meteorological station data, and snow water equivalent (GlobSnow, assimilated snow data set). We analyzed the data for the full period (1982-2014) and for two sub-periods (1982-1998 and 1999-2014), which were chosen based on the declining Alaska SWI since 1998. MaxNDVI has increased from 1982-2014 over most of the Arctic but has declined from 1999 to 2014 southwest Alaska. TI-NDVI has trends that are similar to those for MaxNDVI for the full period but display widespread declines over the 1999-2014 period. Therefore, as the MaxNDVI has continued to increase overall for the Arctic, TI-NDVI has been declining since 1999 and these declines are particularly noteworthy during spring in Alaska. Spring declines in Alaska have been linked to increased spring snow cover that can delay greenup (Bieniek et al. 2015) but recent ground observations suggest that after an initial warming and greening, late season freezing temperature are damaging the plants. The late season freezing temperature hypothesis will be explored with meteorological climate/weather data sets for Alaska tundra regions. References P.A. Bieniek, US Bhatt, DA Walker, MK Raynolds, JC Comiso, HE Epstein, JE Pinzon, CJ Tucker, RL Thoman, H Tran, N M

  13. Carbon and Oxygen Budgets of Subtidal and Intertidal Cyanobacterial Mats

    NASA Technical Reports Server (NTRS)

    DesMarais, David J.; Discipulo, Mykell; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    Intertidal cyanobacterial mats (Lyngbya-dominated) are contrasted with mats (Microcoleus-dominated) that grow in subtidal (0.7m water depth) hypersaline (90-110 permil) environments. In benthic chamber experiments conducted in Oct., 1999, mats exhibited greater net uptake of dissolved inorganic carbon (DIC) from overlying water during the daylight period than Microcoleus mats (e.g., 200 vs 120 mmol C/m. at 26 deg C, respectively). Net DIC release at night was similar for both mats (approx. 80 mmol C/m). Daytime net O2 release by Lyngby mats exceeded that by Microcoleus mats (150 vs 100 mmol O2/m), and O2 uptake at night was comparable for both mats (60-80 mmol O2/m). Nonphotosynthetic populations are more prominent within the subtidal versus intertidal mats, and accordingly exhibited greater internal 02 uptake and DIC production during the day. Over 24 hours, Lyngby-dominated mats exhibited greater net uptake of DIC than subtidal Microcoleus mats, consistent with these intertidal mats being "pioneer" communities that constantly recover from periodic physical disruption in energetic environments. The Microcoleus-dominated mats achieve steady-state mat thicknesses by balancing primary production against diagenetic decomposition of cellular and extracellular organic constituents.

  14. Reactive composite compositions and mat barriers

    DOEpatents

    Langton, Christine A.; Narasimhan, Rajendran; Karraker, David G.

    2001-01-01

    A hazardous material storage area has a reactive multi-layer composite mat which lines an opening into which a reactive backfill and hazardous material are placed. A water-inhibiting cap may cover the hazardous material storage area. The reactive multi-layer composite mat has a backing onto which is placed an active layer which will neutralize or stabilize hazardous waste and a fronting layer so that the active layer is between the fronting and backing layers. The reactive backfill has a reactive agent which can stabilize or neutralize hazardous material and inhibit the movement of the hazardous material through the hazardous material storage area.

  15. Qualification of HiMAT flight systems

    NASA Technical Reports Server (NTRS)

    Myers, A. F.; Sheets, S. G.

    1980-01-01

    The highly maneuverable aircraft technology (HiMAT) remotely piloted research vehicle is discussed with emphasis on the advanced composite and metallic structures, digital fly-by-wire controls, and digitally implemented integrated propulsion control systems. Techniques used to qualify the systems for flight are examined. Computation and simulation of the HiMAT system are investigated in relation to Cyber-Varian simulation. The techniques used in flight qualification are complicated by ground based flight critical systems and severe onboard volume constraints imposed by the scale design.

  16. Nitrogen cycle in microbial mats: completely unknown?

    NASA Astrophysics Data System (ADS)

    Coban, O.; Bebout, B.

    2015-12-01

    Microbial mats are thought to have originated around 3.7 billion years ago, most likely in the areas around submarine hydrothermal vents, which supplied a source of energy in the form of reduced chemical species from the Earth's interior. Active hydrothermal vents are also believed to exist on Jupiter's moon Europa, Saturn's moon Enceladus, and on Mars, earlier in that planet's history. Microbial mats have been an important force in the maintenance of Earth's ecosystems and the first photosynthesis was also originated there. Microbial mats are believed to exhibit most, if not all, biogeochemical processes that exist in aquatic ecosystems, due to the presence of different physiological groups of microorganisms therein. While most microbially mediated biogeochemical transformations have been shown to occur within microbial mats, the nitrogen cycle in the microbial mats has received very little study in spite of the fact that nitrogen usually limits growth in marine environments. We will present the first results in the determination of a complete nitrogen budget for a photosynthetic microbial mat. Both in situ sources and sinks of nitrogen in photosynthetic microbial mats are being measured using stable isotope techniques. Our work has a particular focus on recently described, but poorly understood, processes, e.g., anammox and dissimilatory nitrate reduction, and an emphasis on understanding the role that nitrogen cycling may play in generating biogenic nitrogen isotopic signatures and biomarker molecules. Measurements of environmental controls on nitrogen cycling should offer insight into the nature of co-evolution of these microbial communities and their planets of origin. Identifying the spatial (microscale) as well as temporal (diel and seasonal) distribution of nitrogen transformations, e.g., rates of nitrification and denitrification, within mats, particularly with respect to the distribution of photosynthetically-produced oxygen, is anticipated. The results

  17. RPRV research focus on HiMAT

    NASA Technical Reports Server (NTRS)

    Lockenour, J. L.; Layton, G. P.

    1976-01-01

    A review is presented of the F-15 Remotely Piloted Research Vehicle (RPRV) project. The F-15 RPRV is air-launched from a B-52 at 50,000 ft. Following launch a series of research maneuvers are performed during an unpowered descent to a recovery altitude. Another RPRV program considered is the Highly Maneuverable Aircraft Technology (HiMAT) program. This program is designed to use RPRVs to speed the technology transition from wind tunnel to flight and to reduce the cost of aeronautical experiments. It is pointed out that HiMAT will make extensive use of composite materials.

  18. BRDF characteristics of tundra vegetation communities in Yamal, Western Siberia

    NASA Astrophysics Data System (ADS)

    Buchhorn, Marcel; Heim, Birgit; Walker, Donald A. Skip; Epstein, Howard; Leibman, Marina

    2013-04-01

    Satellite data from platforms with pointing capabilities (CHRIS/Proba, RapidEye) or from sensors with wide swath (AVHRR, MODIS, MERIS) is influenced by the bidirectional reflectance distribution function (BRDF). This effect can cause significant changes in the measured spectral surface reflectance depending on the solar illumination geometry and sensor viewing conditions. The Environmental Mapping and Analysis Program (EnMAP), a German hyperspectral mission with expected launch in 2016, will provide high spectral resolution observations with a ground sampling distance of 30 meters. Since the EnMAP sensor has pointing capabilities, both spectral and directional reflection characteristics need to be taken into account for the algorithms development for vegetation parameters. The 'hyperspectral method development for Arctic VEGetation biomes' (hy-Arc-VEG) project is part of the national preparation program for the EnMAP mission. Within the EnMAP projcect hy-Arc-VEG we developed a portable field spectro-goniometer, named ManTIS (Manual Transportable Instrument for Spherical BRDF observations), for the in-situ measurements of anisotropic effects of tundra surfaces (national and international patent pending - DE 102011117713.6). The goniometer was designed for field use in difficult as well as challenging terrain and climate. It is therefore of low weight, without electrical devices and weatherproof. It can be disassembled and packed into small boxes for transport. The current off-nadir viewing capacity is matched to the EnMAP sensor configuration (up to 30°). We carried out spectral field and goniometer measurements on the joint YAMAL 2011 expedition (RU-US-DE) organized by the Earth-Cryosphere Institute (ECI) in August 2011 on the Yamal Peninsula, northwestern Siberia, Russia. The field goniometer measurements (conducted under varying sun zenith angles) as well as field spectro-radiometrical measurements were carried out at the NASA Yamal Land Cover/Land Use Change

  19. Effect of Salinity on the Stable Carbon Isotopic Composition of Microbial Mats and Associated Lipid Biomarkers

    NASA Astrophysics Data System (ADS)

    Jahnke, L. L.; Parenteau, M. N.; Kubo, M. D.; Des Marais, D. J.

    2014-12-01

    Modern microbial mats are commonly used as analogs for understanding early ecosystem evolution. A primary feature of benthic ecosystems is the fixation of CO2 in the photic zone and transfer and/or mineralization of organic carbon through a diverse tropic structure. Generally, the resulting δ13C values for organic matter relative to DIC is small which indicates that these mats are CO2-limited. Microcoleus mat flux measurements indicate that small amounts of CO2 fixed during the day are lost to the overlying water at night as C13-enriched DIC (Des Marais and Canfield 1994). This loss results in depletion in mat organic matter and is thought to occur as a result of remineralized DIC fixation by chemo- and/or photoautotrophs. We have examined the fate of fixed carbon in hypersaline mats by analysis of the stable C-isotopes of bulk organic carbon and lipid compounds in a laminated-Microcoleus mat (90 ‰, pH 8.6) and in a gypsum-endoevaporitic, Halothece mat (163‰, pH 7.4). In the surface photic zone of Microcoleus mat, the δ13C TOC was -10.0 ‰ with membrane fatty acids (i-15, n-16, n-18, cy-19) ranging from -17.2 to -18.0‰. Cyanobacterial alkanes were similarly depleted (n-17 = -19.5‰). Eurkaryotic sterols and bacterial hopanoids were somewhat enriched with δ13C values ~-15‰. For Microcoleus mat, little variation occurred over 70 mm of core depth. The TOC and FA values for surface, endoevaporitic Halothece mat were generally similar to those of Microcoleus. However, below the surface gypsum crust, discrimination increased. Mass balance calculations for surface FA = -18.5‰ while the FA from layers below the crust = -25.2‰. The δ13C values for cyanobacterial alkanes (~-20‰) were similar from all layers while hopanoids from below crust were slightly depleted relative to those from surface. An apparent increased discrimination during fixation of remineralized DIC presumably by anoxygenic phototrophs present below the surface gypsum crust (Jahnke et al

  20. Fourfold higher tundra volatile emissions due to arctic summer warming

    NASA Astrophysics Data System (ADS)

    Lindwall, Frida; Schollert, Michelle; Michelsen, Anders; Blok, Daan; Rinnan, Riikka

    2016-03-01

    Biogenic volatile organic compounds (BVOCs), which are mainly emitted by vegetation, may create either positive or negative climate forcing feedbacks. In the Subarctic, BVOC emissions are highly responsive to temperature, but the effects of climatic warming on BVOC emissions have not been assessed in more extreme arctic ecosystems. The Arctic undergoes rapid climate change, with air temperatures increasing at twice the rate of the global mean. Also, the amount of winter precipitation is projected to increase in large areas of the Arctic, and it is unknown how winter snow depth affects BVOC emissions during summer. Here we examine the responses of BVOC emissions to experimental summer warming and winter snow addition—each treatment alone and in combination—in an arctic heath during two growing seasons. We observed a 280% increase relative to ambient in BVOC emissions in response to a 4°C summer warming. Snow addition had minor effects on growing season BVOC emissions after one winter but decreased BVOC emissions after the second winter. We also examined differences between canopy and air temperatures and found that the tundra canopy surface was on average 7.7°C and maximum 21.6°C warmer than air. This large difference suggests that the tundra surface temperature is an important driver for emissions of BVOCs, which are temperature dependent. Our results demonstrate a strong response of BVOC emissions to increasing temperatures in the Arctic, suggesting that emission rates will increase with climate warming and thereby feed back to regional climate change.

  1. Quantifying the historic and future distribution of fire in Alaskan tundra ecosystems

    NASA Astrophysics Data System (ADS)

    Young, A. M.; Higuera, P. E.; Duffy, P. A.

    2012-12-01

    During the past 60 years fire has been relatively rare and small in size within tundra ecosystems. However, historical observations and paleoecological evidence indicates that fire regimes vary widely across Alaskan tundra, in both space and time. These lines of evidence suggest that fire occupies a highly specified niche or ecological space in Alaskan tundra, which may change significantly with future climate warming. The objective of this research was to quantify the relationships between fire occurrence and different seasonal climate variables, and to begin to make inferences about future distributions of fire across the tundra landscape. The results of this research will ultimately contribute to the goal of summarizing the linkages that exist among climate, vegetation, and fire in the historical record, and for making predictions concerning fire disturbance in tundra ecosystems throughout the next century. Historic tundra fires occurred non-randomly across space, and a relationship exists between fire occurrence and warm, dry climates. We quantified this relationship with generalized boosting models (GBM) using datasets of downscaled temperature and precipitation (2 km, 1971-2000), and historic records of tundra area burned (1950-2010). The GBM used six seasonal climate variables, focused on growing season temperature and precipitation, to predict the probability of fire occurrence over the 1950-2010 time period. To understand implications of these historic relationships given ongoing climate warming, we constructed future climatologies of temperature and precipitation for the five GCMs which performed best in Alaska under the IPCC AR4 A1B (middle-of-the-road) emissions scenario for the time period 2021-2050. The GBM performed well predicting the observed spatial distribution of tundra area burned, capturing key regions which experienced the most fire activity from 1950-2010. The mean temperature of the warmest month (MeanMaxTemp) was the most influential

  2. Isotopic identification of soil and permafrost nitrate sources in an Arctic tundra ecosystem

    DOE PAGESBeta

    Heikoop, Jeffrey M.; Throckmorton, Heather M.; Newman, Brent D.; Perkins, George B.; Iversen, Colleen M.; Chowdhury, Taniya Roy; Romanovsky, Vladimir; Graham, David E.; Norby, Richard J.; Wilson, Cathy J.; et al

    2015-05-13

    The nitrate (NO3–) dual isotope approach was applied to snowmelt, tundra active layer pore waters, and underlying permafrost in Barrow, Alaska, USA, to distinguish between NO3– derived from atmospheric deposition versus that derived from microbial nitrification.

  3. Transformation of nitrogen compounds in the tundra soils of Northern Fennoscandia

    NASA Astrophysics Data System (ADS)

    Maslov, M. N.; Makarov, M. I.

    2016-07-01

    The transformation of organic nitrogen compounds in the soils of tundra ecosystems of Northern Fennoscandia has been studied under laboratory and natural conditions. Tundra soils contain significant reserves of total nitrogen, but they are poor in its extractable mineral and organic forms. The potential rates of the net mineralization and net immobilization of nitrogen by microorganisms vary among the soils and depend on the C: N ratio in the extractable organic matter and microbial biomass of soil. Under natural conditions, the rate of nitrogen net mineralization is lower than the potential rate determined under laboratory conditions by 6-25 times. The incubation of tundra soils in the presence of plants does not result in the accumulation of mineral nitrogen compounds either in the soil or in microbial biomass. This confirms the high competitive capacity of plants under conditions of limited nitrogen availability in tundra ecosystems.

  4. Unexpected Diversity and Complexity of the Guerrero Negro Hypersaline Microbial Mat

    PubMed Central

    Ley, Ruth E.; Harris, J. Kirk; Wilcox, Joshua; Spear, John R.; Miller, Scott R.; Bebout, Brad M.; Maresca, Julia A.; Bryant, Donald A.; Sogin, Mitchell L.; Pace, Norman R.

    2006-01-01

    We applied nucleic acid-based molecular methods, combined with estimates of biomass (ATP), pigments, and microelectrode measurements of chemical gradients, to map microbial diversity vertically on a millimeter scale in a hypersaline microbial mat from Guerrero Negro, Baja California Sur, Mexico. To identify the constituents of the mat, small-subunit rRNA genes were amplified by PCR from community genomic DNA extracted from layers, cloned, and sequenced. Bacteria dominated the mat and displayed unexpected and unprecedented diversity. The majority (1,336) of the 1,586 bacterial 16S rRNA sequences generated were unique, representing 752 species (≥97% rRNA sequence identity) in 42 of the main bacterial phyla, including 15 novel candidate phyla. The diversity of the mat samples differentiated according to the chemical milieu defined by concentrations of O2 and H2S. Bacteria of the phylum Chloroflexi formed the majority of the biomass by percentage of bulk rRNA and of clones in rRNA gene libraries. This result contradicts the general belief that cyanobacteria dominate these communities. Although cyanobacteria constituted a large fraction of the biomass in the upper few millimeters (>80% of the total rRNA and photosynthetic pigments), Chloroflexi sequences were conspicuous throughout the mat. Filamentous Chloroflexi bacteria were identified by fluorescence in situ hybridization within the polysaccharide sheaths of the prominent cyanobacterium Microcoleus chthonoplastes, in addition to free living in the mat. The biological complexity of the mat far exceeds that observed in other polysaccharide-rich microbial ecosystems, such as the human and mouse distal guts, and suggests that positive feedbacks exist between chemical complexity and biological diversity. PMID:16672518

  5. Marine animals significantly increase tundra N2O and CH4 emissions in maritime Antarctica

    NASA Astrophysics Data System (ADS)

    Zhu, Renbin; Liu, Yashu; Xu, Hua; Ma, Dawei; Jiang, Shan

    2013-12-01

    studies on greenhouse gas emissions from animals concentrated on domestic animals, with limited data available from wild animals. The number of marine animals is potentially large in coastal Antarctica. In this paper, N2O and CH4 emissions were investigated from a penguin colony, a seal colony, a skua colony, the adjacent animal-lacking tundra, and background tundra sites to test the effects of marine animals on their fluxes in maritime Antarctica. Extremely high N2O emissions occurred in the penguin puddles (mean 392 µg N2O m-2 h-1) and seal wallows (mean 579 µg N2O m-2 h-1). The N2O emissions from animal colony tundra (13-57 µg N2O m-2 h-1) are much higher than those from the animal-lacking tundra, whereas the background tundra showed negligible N2O fluxes. Penguin puddles and seal wallows were stronger CH4 emitters than animal colony tundra soils, while animal-lacking tundra soils were strong CH4 sinks. Overall high N2O and CH4 emissions were modulated by soil physical and chemical processes associated with marine animal activities: sufficient supply of the nutrients NH4+-N and NO3--N, total nitrogen, and total organic carbon from marine animal excreta, animal tramp, and high soil water-filled pore space. Laboratory incubation experiments further confirmed that penguin and seal colony soils produced much higher N2O and CH4 emissions than animal-lacking tundra soils. Our results indicate that marine animal colonies are the hot spots for N2O and CH4 emissions in maritime Antarctica, and even at the global scale, and current climate warming will further increase their emissions.

  6. Initial Conceptualization and Simulation of Arctic Tundra Landscape Evolution Using the Alaska Thermokarst Model

    NASA Astrophysics Data System (ADS)

    Bolton, W. R.; Romanovsky, V. E.; McGuire, A. D.; Grosse, G.; Lara, M. J.

    2014-12-01

    Thermokarst topography forms whenever ice-rich permafrost thaws and the ground subsides due to the volume loss when excess ground ice transitions to water. The Alaska Thermokarst Model (ATM) is a large-scale, state-and-transition model designed to simulate transitions between [non-]thermokarst landscape units, or cohorts. The ATM uses a frame-based methodology to track transitions and proportion of cohorts within a 1-km2 grid cell. In the arctic tundra environment, the ATM tracks thermokarst-related transitions between wetland tundra, graminoid tundra, shrub tundra, and thermokarst lakes. The transition from one cohort to another due to thermokarst processes can take place if thaw reaches ice-rich ground layers either due to pulse disturbance events such as a large precipitation event or fires or due to gradual active layer deepening that eventually results in penetration of the protective layer. The protective layer buffers the ice-rich soils from the land surface and is critical to determine how susceptible an area is to thermokarst degradation. The rate of terrain transition in our model is determined by the ice-content of the soil, the drainage efficiency (or ability of the landscape to store or transport water), and a cumulative probability of thermokarst initiation. Tundra types are allowed to transition from one type to another (ie wetland tundra to a graminoid tundra) under favorable climatic conditions. In this study, we present our conceptualization and initial simulation results from the ATM model for an 1792 km2 area on the Barrow Peninsula, Alaska. The area selected for simulation is located in a polygonal tundra landscape under varying degrees of thermokarst degradation. The goal of this modeling study is to simulate landscape evolution in response to thermokarst disturbance as a result of climate change. The ATM will eventually be incorporated into the Integrated Ecosystem Model (IEM) for Alaska and Northwest Canada for use in management decisions

  7. Fire behavior, weather, and burn severity of the 2007 anaktuvuk river tundra fire, North Slope, Alaska

    USGS Publications Warehouse

    Jones, B.; Kolden, C.; Jandt, R.; Abatzoglou, J.; Urban, F.; Arp, C.

    2009-01-01

    In 2007, the Anaktuvuk River Fire (ARF) became the largest recorded tundra fire on the North Slope of Alaska. The ARF burned for nearly three months, consuming more than 100,000 ha. At its peak in early September, the ARF burned at a rate of 7000 ha d-1. The conditions potentially responsible for this large tundra fire include modeled record high summer temperature and record low summer precipitation, a late-season high-pressure system located over the Beaufort Sea, extremely dry soil conditions throughout the summer, and sustained southerly winds during the period of vegetation senescence. Burn severity mapping revealed that more than 80% of the ARF burned at moderate to extreme severity, while the nearby Kuparuk River Fire remained small and burned at predominantly (80%) low severity. While this study provides information that may aid in the prediction of future large tundra fires in northern Alaska, the fact that three other tundra fires that occurred in 2007 combined to burn less than 1000 ha suggests site specific complexities associated with tundra fires on the North Slope, which may hamper the development of tundra fire forecasting models.

  8. Multi-Sensor Approach for Assessing the Taiga-Tundra Boundary

    NASA Technical Reports Server (NTRS)

    Ranson, K. J.; Sun, G.; Kharuk, V. I.; Kovacs, K.

    2003-01-01

    Monitoring the dynamics of the tundra-taiga boundary is critical for our understanding of the causes and consequences of the changes in this area. Because of its inaccessibility, remote sensing data will play an important role. In this study we examined the use of several remote sensing techniques for identifying the existing tundra-taiga ecotone. These include Landsat, MISR and RADARSAT data. High-resolution IKONOS images were used for local ground truth. It was found that on Landsat ETM+ summer images, reflectance from tundra and taiga at band 4 (NIR) is similar, but different at other bands such as red, and MIR bands. When the incidence angle is small, C-band HH-pol backscattering coefficients from both tundra and taiga are relatively high. The backscattering from tundra targets decreases faster than taiga targets when the incidence angle increases, because the tundra targets look smoother than taiga. Because of the shading effect of the vegetation, the MISR data, both multi-spectral data at nadir looking and multi-angle data at red and NIR bands, clearly show the transition zone.

  9. Tundra ecosystems observed to be CO2 sources due to differential amplification of the carbon cycle.

    PubMed

    Belshe, E F; Schuur, E A G; Bolker, B M

    2013-10-01

    Are tundra ecosystems currently a carbon source or sink? What is the future trajectory of tundra carbon fluxes in response to climate change? These questions are of global importance because of the vast quantities of organic carbon stored in permafrost soils. In this meta-analysis, we compile 40 years of CO2 flux observations from 54 studies spanning 32 sites across northern high latitudes. Using time-series analysis, we investigated if seasonal or annual CO2 fluxes have changed over time, and whether spatial differences in mean annual temperature could help explain temporal changes in CO2 flux. Growing season net CO2 uptake has definitely increased since the 1990s; the data also suggest (albeit less definitively) an increase in winter CO2 emissions, especially in the last decade. In spite of the uncertainty in the winter trend, we estimate that tundra sites were annual CO2 sources from the mid-1980s until the 2000s, and data from the last 7 years show that tundra continue to emit CO2 annually. CO2 emissions exceed CO2 uptake across the range of temperatures that occur in the tundra biome. Taken together, these data suggest that despite increases in growing season uptake, tundra ecosystems are currently CO2 sources on an annual basis. PMID:23953054

  10. Labile carbon concentrations are strongly linked to plant production in Arctic tussock tundra soils

    NASA Astrophysics Data System (ADS)

    Darrouzet-Nardi, A.; Weintraub, M. N.; Euskirchen, E. S.; Steltzer, H.; Sullivan, P.

    2013-12-01

    The exchange of carbon and nutrients between plants and microbes is a key determinant of carbon balance in Arctic soils. Microbes rely on labile plant carbon for the energy they need to produce enzymes that can release nutrients and less energetically favorable carbon from soil organic matter. One of the main mechanisms of carbon transfer is rhizodeposition, the exudation of labile plant carbon such as sugars from roots into the rhizosphere. Despite the importance of this flow of energy and materials from plants to microbes, there have been few attempts to quantify labile carbon pools or fluxes in Arctic soils. To improve our knowledge of labile carbon dynamics in Arctic soils, we address two basic questions: (1) What are the seasonal patterns of labile carbon concentrations? and (2) How do seasonal patterns in labile carbon correlate with plant production, microbial biomass, and soil nutrients? We measured concentrations of total reducing sugars (TRS) in the soil solution of moist acidic tussock tundra on 28 dates during the 2012 growing season in 20 plots of an early snowmelt × warming experiment. We evaluated these total reducing sugar concentrations in the context of eddy flux carbon exchange data, plant NDVI, total dissolved carbon in soils, microbial biomass, and soil nutrients. Though we did not see treatment effects of the snowmelt × warming experiment, we did observe a clear seasonal pattern in TRS concentrations in which they started low at the time of thaw, then built to a maximum value around the time of peak plant physiology in July, followed by a decline as plants senesced. We observed a clear correlation between TRS and gross primary production (GPP). NDVI values also increased with TRS concentrations during the first half of the season and then leveled off as TRS began its decline. These relationships were in contrast to labile N concentrations, which remained at low concentrations all season. Our data suggest that rhizodeposition of labile carbon

  11. Increasing shrub abundance and N addition in Arctic tundra affect leaf and root litter decomposition differently

    NASA Astrophysics Data System (ADS)

    McLaren, J.; van de Weg, M. J.; Shaver, G. R.; Gough, L.

    2013-12-01

    Changes in global climate have resulted in a ';greening' of the Arctic as the abundance of deciduous shrub species increases. Consequently, not only the living plant community, but also the litter composition changes, which in turn can affect carbon turnover patterns in the Arctic. We examined effects of changing litter composition (both root and leaf litter) on decomposition rates with a litter bag study, and specifically focused on the impact of deciduous shrub Betula nana litter on litter decomposition from two evergreen shrubs (Ledum palustre, and Vaccinium vitis-idaea) and one graminoid (Eriophorum vaginatum) species. Additionally, we investigated how decomposition was affected by nutrient availability by placing the litterbags in an ambient and a fertilized moist acidic tundra environment. Measurements were carried out seasonally over 2 years (after snow melt, mid-growing season, end growing season). We measured litter mass loss over time, as well as the respiration rates (standardized for temperature and moisture) and temperature sensitivity of litter respiration at the time of harvesting the litter bags. For leaves, Betula litter decomposed faster than the other three species, with Eriophorum leaves decomposing the slowest. This pattern was observed for both mass loss and litter respiration rates, although the differences in respiration became smaller over time. Surprisingly, combining Betula with any other species resulted in slower overall weight loss rates than would be predicted based on monoculture weight loss rates. This contrasted with litter respiration at the time of sampling, which showed a positive mixing effect of adding Betula leaf liter to the other species. Apparently, during the first winter months (September - May) Betula litter decomposition is negatively affected by mixing the species and this legacy can still be observed in the total mass loss results later in the year. For root litter there were fewer effects of species identity on root

  12. Organic matter composition and stabilization in a polygonal tundra soil of the Lena Delta

    NASA Astrophysics Data System (ADS)

    Höfle, S.; Rethemeyer, J.; Mueller, C. W.; John, S.

    2013-05-01

    This study investigated soil organic matter (OM) composition of differently stabilized soil OM fractions in the active layer of a polygonal tundra soil in the Lena Delta, Russia, by applying density and particle size fractionation combined with qualitative OM analysis using solid state 13C nuclear magnetic resonance spectroscopy, and lipid analysis combined with 14C analysis. Bulk soil OM was mainly composed of plant-derived, little-decomposed material with surprisingly high and strongly increasing apparent 14C ages with active layer depth suggesting slow microbial OM transformation in cold climate. Most soil organic carbon was stored in clay and fine-silt fractions (< 6.3 μm), which were composed of little-decomposed plant material, indicated by the dominance of long n-alkane and n-fatty acid compounds and low alkyl/O-alkyl C ratios. Organo-mineral associations, which are suggested to be a key mechanism of OM stabilization in temperate soils, seem to be less important in the active layer as the mainly plant-derived clay- and fine-silt-sized OM was surprisingly "young", with 14C contents similar to the bulk soil values. Furthermore, these fractions contained less organic carbon compared to density fractionated OM occluded in soil aggregates - a further important OM stabilization mechanism in temperate soils restricting accessibility of microorganisms. This process seems to be important at greater active layer depth where particulate OM, occluded in soil aggregates, was "older" than free particulate OM.

  13. Organic matter composition and stabilization in a polygonal tundra soil of the Lena-Delta

    NASA Astrophysics Data System (ADS)

    Höfle, S.; Rethemeyer, J.; Mueller, C. W.; John, S.

    2012-09-01

    This study investigated soil organic matter (OM) composition of differently stabilized soil OM fractions in the active layer of a polygonal tundra soil in the Lena-Delta, Russia by applying density and particle-size fractionation combined with qualitative OM analysis using solid state 13C nuclear magnetic resonance spectroscopy, and lipid analysis combined with 14C analysis. Bulk soil OM was mainly composed of plant-derived, little decomposed material with surprisingly low and strongly increasing apparent 14C ages with active layer depth suggesting slow microbial OM transformation in cold climate. Most soil organic carbon was stored in clay and fine silt fractions (< 6.3 μm), which were composed of little decomposed plant material indicated by the dominance of long n-alkane and n-fatty acid compounds and low alkyl/O-alkyl C ratios. Organo-mineral associations, which are suggested to be a key mechanism of OM stabilization in temperate soils, seem to be less important in the active layer as the mainly plant-derived clay and fine silt sized OM was surprisingly "young" with 14C contents similar to the bulk soil values. Furthermore these fractions contained less organic carbon compared to density fractionated OM occluded in soil aggregates - a further important OM stabilization mechanism in temperate soils restricting accessibility of microorganisms. This process seems to be important at greater active layer depth where particulate OM, occluded in soil aggregates, was "older" than free particulate OM.

  14. Old soil carbon losses increase with ecosystem respiration in experimentally thawed tundra

    NASA Astrophysics Data System (ADS)

    Hicks Pries, Caitlin E.; Schuur, Edward A. G.; Natali, Susan M.; Crummer, K. Grace

    2016-02-01

    Old soil carbon (C) respired to the atmosphere as a result of permafrost thaw has the potential to become a large positive feedback to climate change. As permafrost thaws, quantifying old soil contributions to ecosystem respiration (Reco) and understanding how these contributions change with warming is necessary to estimate the size of this positive feedback. We used naturally occurring C isotopes (δ13C and Δ14C) to partition Reco into plant, young soil and old soil sources in a subarctic air and soil warming experiment over three years. We found that old soil contributions to Reco increased with soil temperature and Reco flux. However, the increase in the soil warming treatment was smaller than expected because experimentally warming the soils increased plant contributions to Reco by 30%. On the basis of these data, an increase in mean annual temperature from -5 to 0 °C will increase old soil C losses from moist acidic tundra by 35-55 g C m-2 during the growing season. The largest losses will probably occur where the plant response to warming is minimal.

  15. Distribution of cultivated and uncultivated cyanobacteria and Chloroflexus-like bacteria in hot spring microbial mats

    NASA Technical Reports Server (NTRS)

    Ruff-Roberts, A. L.; Kuenen, J. G.; Ward, D. M.

    1994-01-01

    Oligodeoxynucleotide hybridization probes were developed to complement specific regions of the small subunit (SSU) rRNA sequences of cultivated and uncultivated cyanobacteria and Chloroflexus-like bacteria, which inhabit hot spring microbial mats. The probes were used to investigate the natural distribution of SSU rRNAs from these species in mats of Yellowstone hot springs of different temperatures and pHs as well as changes in SSU rRNA distribution resulting from 1-week in situ shifts in temperature, pH, and light intensity. Synechococcus lividus Y-7c-s SSU rRNA was detected only in the mat of a slightly acid spring, from which it may have been initially isolated, or when samples from a more alkaline spring were incubated in the more acid spring. Chloroflexus aurantiacus Y-400-fl SSU rRNA was detected only in a high-temperature mat sample from the alkaline Octopus Spring or when lower-temperature samples from this mat were incubated at the high-temperature site. SSU rRNAs of uncultivated species were more widely distributed. Temperature distributions and responses to in situ temperature shifts suggested that some of the uncultivated cyanobacteria might be adapted to high-, moderate-, and low-temperature ranges whereas an uncultivated Chloroflexus-like bacterium appears to have broad temperature tolerance. SSU rRNAs of all uncultivated species inhabiting a 48 to 51 degrees C Octopus Spring mat site were most abundant in the upper 1 mm and were not detected below a 2.5-to 3.5-mm depth, a finding consistent with their possible phototrophic nature. However, the effects of light intensity reduction on these SSU rRNAs were variable, indicating the difficulty of demonstrating a phototrophic phenotype in light reduction experiments.

  16. Distribution of cultivated and uncultivated cyanobacteria and Chloroflexus-like bacteria in hot spring microbial mats.

    PubMed Central

    Ruff-Roberts, A L; Kuenen, J G; Ward, D M

    1994-01-01

    Oligodeoxynucleotide hybridization probes were developed to complement specific regions of the small subunit (SSU) rRNA sequences of cultivated and uncultivated cyanobacteria and Chloroflexus-like bacteria, which inhabit hot spring microbial mats. The probes were used to investigate the natural distribution of SSU rRNAs from these species in mats of Yellowstone hot springs of different temperatures and pHs as well as changes in SSU rRNA distribution resulting from 1-week in situ shifts in temperature, pH, and light intensity. Synechococcus lividus Y-7c-s SSU rRNA was detected only in the mat of a slightly acid spring, from which it may have been initially isolated, or when samples from a more alkaline spring were incubated in the more acid spring. Chloroflexus aurantiacus Y-400-fl SSU rRNA was detected only in a high-temperature mat sample from the alkaline Octopus Spring or when lower-temperature samples from this mat were incubated at the high-temperature site. SSU rRNAs of uncultivated species were more widely distributed. Temperature distributions and responses to in situ temperature shifts suggested that some of the uncultivated cyanobacteria might be adapted to high-, moderate-, and low-temperature ranges whereas an uncultivated Chloroflexus-like bacterium appears to have broad temperature tolerance. SSU rRNAs of all uncultivated species inhabiting a 48 to 51 degrees C Octopus Spring mat site were most abundant in the upper 1 mm and were not detected below a 2.5-to 3.5-mm depth, a finding consistent with their possible phototrophic nature. However, the effects of light intensity reduction on these SSU rRNAs were variable, indicating the difficulty of demonstrating a phototrophic phenotype in light reduction experiments. Images PMID:11536630

  17. Method for production of carbon nanofiber mat or carbon paper

    SciTech Connect

    Naskar, Amit K.

    2015-08-04

    Method for the preparation of a non-woven mat or paper made of carbon fibers, the method comprising carbonizing a non-woven mat or paper preform (precursor) comprised of a plurality of bonded sulfonated polyolefin fibers to produce said non-woven mat or paper made of carbon fibers. The preforms and resulting non-woven mat or paper made of carbon fiber, as well as articles and devices containing them, and methods for their use, are also described.

  18. Biomarkers as Indicators of Respiration During Laboratory Incubations of Alaskan Arctic Tundra Permafrost Soils

    NASA Astrophysics Data System (ADS)

    Hutchings, J.; Schuur, E.; Bianchi, T. S.; Bracho, R. G.

    2015-12-01

    High latitude permafrost soils are estimated to store 1,330 - 1,580 Pg C, which account for ca. 40% of global soil C and nearly twice that of atmospheric C. Disproportionate heating of high latitude regions during climate warming potentially results in permafrost thaw and degradation of surficial and previously-frozen soil C. Understanding how newly-thawed soils respond to microbial degradation is essential to predicting C emissions from this region. Laboratory incubations have been a key tool in understanding potential respiration rates from high latitude soils. A recent study found that among the common soil measurements, C:N was the best predictor of C losses. Here, we analyzed Alaskan Arctic tundra soils from before and after a nearly 3-year laboratory incubation. Bulk geochemical values as well as the following biomarkers were measured: lignin, amino acids, n-alkanes, and glycerol dialkyl glycerol tetraethers (GDGT). We found that initial C:N did not predict C losses and no significant change in C:N between initial and final samples. The lignin acid to aldehyde (Ad:Al) degradation index showed the same results with a lack of C loss prediction and no significant change during the experiment. However, we did find that C:N and Ad:Al had a significant negative correlation suggesting behavior consistent with expectations. The failure to predict C losses was likely influenced by a number of factors, including the possibility that biomarkers were tracking a smaller fraction of slower cycling components of soil C. To better interpret these results, we also used a hydroxyproline-based amino acid degradation index and n-alkanes to estimate the contribution Sphagnum mosses to soil samples - known to have slower turnover times than vascular plants. Finally, we applied a GDGT soil temperature proxy to estimate the growing season soil temperatures before each incubation, as well as investigating the effects of incubation temperature on the index's temperature estimate.

  19. Lipid Biomarkers for a Hypersaline Microbial Mat Community

    NASA Technical Reports Server (NTRS)

    Jahnke, Linda L.; Embaye, Tsege; Turk, Kendra A.

    2003-01-01

    The use of lipid biomarkers and their carbon isotopic compositions are valuable tools for establishing links to ancient microbial ecosystems. As witnessed by the stromatolite record, benthic microbial mats grew in shallow water lagoonal environments where microorganisms had virtually no competition apart from the harsh conditions of hypersalinity, desiccation and intense light. Today, the modern counterparts of these microbial ecosystems find appropriate niches in only a few places where extremes eliminate eukaryotic grazers. Answers to many outstanding questions about the evolution of microorganisms and their environments on early Earth are best answered through study of these extant analogs. Lipids associated with various groups of bacteria can be valuable biomarkers for identification of specific groups of microorganisms both in ancient organic-rich sedimentary rocks (geolipids) and contemporary microbial communities (membrane lipids). Use of compound specific isotope analysis adds additional refinement to the identification of biomarker source, so that it is possible to take advantage of the 3C-depletions associated with various functional groups of organisms (i.e. autotrophs, heterotrophs, methanotrophs, methanogens) responsible for the cycling of carbon within a microbial community. Our recent work has focused on a set of hypersaline evaporation ponds at Guerrero Negro, Baja California Sur, Mexico which support the abundant growth of Microcoleus-dominated microbial mats. Specific biomarkers for diatoms, cyanobacteria, archaea, green nonsulfur (GNS), sulfate reducing, and methanotrophic bacteria have been identified. Analyses of the ester-bound fatty acids indicate a highly diverse microbial community, dominated by photosynthetic organisms at the surface.

  20. 30 CFR 77.513 - Insulating mats at power switches.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Insulating mats at power switches. 77.513... COAL MINES Electrical Equipment-General § 77.513 Insulating mats at power switches. Dry wooden platforms, insulating mats, or other electrically nonconductive material shall be kept in place at...

  1. 30 CFR 77.513 - Insulating mats at power switches.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Insulating mats at power switches. 77.513... COAL MINES Electrical Equipment-General § 77.513 Insulating mats at power switches. Dry wooden platforms, insulating mats, or other electrically nonconductive material shall be kept in place at...

  2. 30 CFR 77.513 - Insulating mats at power switches.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Insulating mats at power switches. 77.513... COAL MINES Electrical Equipment-General § 77.513 Insulating mats at power switches. Dry wooden platforms, insulating mats, or other electrically nonconductive material shall be kept in place at...

  3. 30 CFR 77.513 - Insulating mats at power switches.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Insulating mats at power switches. 77.513... COAL MINES Electrical Equipment-General § 77.513 Insulating mats at power switches. Dry wooden platforms, insulating mats, or other electrically nonconductive material shall be kept in place at...

  4. Characterizing adsorptive properties and DOC concentrations in soils of Northern European Russian tundra and taiga.

    NASA Astrophysics Data System (ADS)

    Oosterwoud, Marieke; Temminghoff, Erwin; van der Zee, Sjoerd

    2010-05-01

    Subarctic river basins have an enormous potential to mobilize and transport terrestrial OC to the Arctic Ocean, because 23-48% of the worlds soils organic carbon (SOC) is stored in the high latitude region. Currently the Arctic drainage basin (~24 x 106 km2) processes about 11% of the global dissolved organic carbon (DOC), which is exported to the ocean. About 10-25% of annual C input to the organic surface layer with litter is leached from the organic surface layers. As climate changes, the amount and chemical composition of DOC exported from these basins are expected to change. Adsorption of DOC on mineral phases is the key geochemical process for the release and removal of DOC from this potentially soluble carbon pool. Most DOC leached from organic horizons is adsorbed and retained in the subsoils. The adsorption depends much on the content of sesquioxides and amount of carbon previously accumulated in soils. Besides adsorption, polyvalent metal ions in solution, such as Al and Ca, can cause precipitation of DOC. Along with the decrease of DOC concentrations on its passage through mineral soil, there are major biochemical alterations of DOC composition. Hydrophobic compounds (humic and fulvic acids) of high molecular weight that are rich in acidic functional groups and aromatic compounds adsorb most strongly. Hydrophilic compounds can contribute to DOC adsorption but are also easily desorbed because of the weaker bonding strength. The aim of this study was to characterize the DOC concentrations and their chemical composition as well as the DOC adsorptive properties of soils found in a tundra and taiga catchment of Northern Russia. We sampled soil and soil solution from two catchments in the Komi Republic of European Northern Russia: a tundra (67N/62E) and a taiga (62N/50E). The soil samples were analysed for total organic carbon (Ct) and the content of sequioxides. By extracting soil samples with water we got an impression of the potentially extractable organic

  5. Shrub expansion and climate feedbacks in Arctic tundra

    NASA Astrophysics Data System (ADS)

    Loranty, Michael M.; Goetz, Scott J.

    2012-03-01

    Arctic tundra ecosystems stand to play a substantial role in both the magnitude and rate of global climate warming over the coming decades and centuries. The exact nature of this role will be determined by the combined effects of currently amplified rates of climate warming in the Arctic (Serreze et al 2000) and a series of related positive climate feedbacks that include mobilization of permafrost carbon (Schuur et al 2008), decreases in surface albedo (Chapin et al 2005) and evapotranspiration (ET) mediated increases in atmospheric water vapor (Swann et al 2010). Conceptually, these feedback mechanisms are intuitive and readily comprehensible: warming-induced permafrost thaw will make new soil carbon pools accessible for microbial respiration, and increased vegetation productivity, expansion of shrubs in particular, will lower surface reflectance and increase ET. However, our current understanding of these feedback mechanisms relies largely on limited and local field studies and, as such, the quantitative estimates of feedback effects on regional and global climate require spatial upscaling and uncertainty estimates derived from models. Moreover, the feedback mechanisms interact and their combined net effect on climate is highly variable and not well characterized. A recent study by Bonfils et al (2012) is among the first to explicitly examine how shrub expansion in tundra ecosystems will impact regional climate. Using an Earth system model, Bonfils et al find that an idealized 20% increase in shrub cover north of 60°N latitude will lead to annual temperature increases of 0.66 °C and 1.84 °C, respectively, when the shrubs are 0.5 m and 2 m tall. The modeled temperature increases arise from atmospheric heating as a combined consequence of decreased albedo and increased ET. The primary difference between the two cases is associated with the fact that tall shrubs protrude above the snow, thus reducing albedo year round, whereas short shrubs are completely

  6. Methane dynamics in warming tundra of Northeast European Russia

    NASA Astrophysics Data System (ADS)

    Marushchak, M. E.; Friborg, T.; Biasi, C.; Herbst, M.; Johansson, T.; Kiepe, I.; Liimatainen, M.; Lind, S. E.; Martikainen, P. J.; Virtanen, T.; Soegaard, H.; Shurpali, N. J.

    2015-08-01

    Methane (CH4) fluxes were investigated in a subarctic Russian tundra site in a multi-approach study combining plot scale data, ecosystem scale eddy covariance (EC) measurements and fine resolution land cover classification scheme for regional upscaling. The flux data as measured by the two independent techniques resulted in a seasonal (May-October 2008) cumulative CH4 emission of 2.4 (EC) and 3.7 g CH4 m-2 (manual chambers) for the source area representative of the footprint of the EC instruments. Upon upscaling for the entire study region of 98.6 km2, the chamber measured flux data yielded a regional flux estimate of 6.7 g CH4 m-2 yr-1. Our upscaling efforts accounted for the large spatial variability in the distribution of the various land cover types (LCTs) predominant at our study site. In particular, wetlands with emissions ranging from 34 to 53 g CH4 m-2 yr-1 were the most dominant CH4 emitting surfaces. Emissions from thermokarst lakes were an order of magnitude lower, while the rest of the landscape (mineral tundra) was a weak sink for atmospheric methane. Vascular plant cover was a key factor in explaining the spatial variability of CH4 emissions among wetland types, as indicated by the positive correlation of emissions with the leaf area index (LAI). As elucidated through a stable isotope analysis, the plant transport was the dominant CH4 release pathway that discriminates against heavier δ13C-CH4. The methane released from wetlands was lighter than that in the surface porewater and δ13C in the emitted CH4 correlated with the vascular plant cover (LAI) implying that the plant-mediated CH4 release dominates. A mean value of δ13C obtained here for the emitted CH4, -68.2 ± 2.0 ‰, is within the range of values from other wetlands, thus reinforcing the use of inverse modeling tools to better constrain the CH4 budget. Based on the IPCC A1B emission scenario, a temperature increase of 7 °C has been predicted for the tundra region of European Russia by the

  7. Satellite based permafrost modeling in low land tundra landscapes

    NASA Astrophysics Data System (ADS)

    Langer, M.; Westermann, S.; Heikenfeld, M.; Boike, J.

    2012-12-01

    For most of the cryosphere components such as glaciers, ice sheets, sea ice, and snow satellite monitoring and change detection is well established since several decades. For permafrost, however, which represents the largest component of the Arctic cryosphere operational satellite monitoring schemes do not exist so far. Most of the processes which control the Arctic terrestrial ecosystems are related to the thermal state of permafrost and the freeze/thaw dynamics of the active layer. Hence, satellite based permafrost monitoring would be highly beneficial for the impact assessment of climate change in the Arctic. Permafrost monitoring could also be highly beneficial for the risk assessment of infrastructure in the Arctic such as roads, pipelines, and buildings which are directly affected by the thermal stability of permafrost. Increasing thaw depths and prolonged thaw periods can damage pipelines and interrupt the access to vast regions due to road damages. Sustained warming of permafrost can result in thermal erosion and landslides which threaten buildings and other infrastructural facilities. In this study we present a possible permafrost monitoring scheme based on a numerical heat flow model which is forced by multiple satellite products and initialized by weather reanalysis data. The used forcing and initialization dataset includes the land surface temperature (LST), the snow cover fraction (SCF), and the snow water equivalent (SWE). Previous studies demonstrated that MODIS LST products can deliver reasonable surface temperature measurements in tundra landscapes (Langer et al. 2010, Westermann et al. 2011). This study is based on the ten year record of the daily MOD11A1v5 and MYD11A1v5 land surface temperature products with a spatial resolution of 1km. The snow cover evolution is obtained from the daily GlobSnow SWE product with a spatial resolution of about 25km. In addition, the MODIS snow cover products MOD10A1v5 and MYD10v5 with a resolution of 1km are used

  8. Ecophysiological Changes in Microbial Mats Incubated in a Greenhouse Collaboratory

    NASA Technical Reports Server (NTRS)

    Bebout, Brad; DesMarais, David J.; GarciaPichel, Ferran; Hogan, Mary; Jahnke, Linda; Keller, Richard M.; Miller, Scott R.

    2001-01-01

    Microbial mats are modern examples of the earliest microbial communities known. Among the best studied are microbial mats growing in hypersaline ponds managed for the production of salt by Exportadora de Sal, S.A. de C.V., Guerrero Negro, Baja California Sur, Mexico. In May, 2001, we collected mats from Ponds 4 and 5 in this system and returned them to Ames Research Center, where they have been maintained for a period of over nine months. We report here on both the ecophysiological changes occurring in the mats over that period of time as well as the facility in which they were incubated. Mats (approximately 1 sq. meter total area) were incubated in a greenhouse facility modified to provide the mats with natural levels of visible and ultraviolet radiation as well as constantly flowing, temperature-controlled water. Two replicated treatments were maintained, a 'high salinity' treatment (about 120 ppt) and a 'low salinity' treatment (about 90 ppt). Rates of net biological activity (e.g., photosynthesis, respiration, trace gas production) in the mats were relatively constant over the several months, and were similar to rates of activity measured in the field. However, over the course of the incubation, mats in both treatments changed in physical appearance. The most obvious change was that mats in the higher salinity treatments developed a higher proportion of carotenoid pigments (relative to chlorophyll), resulting in a noticeably orange color in the high salinity mats. This trend is also seen in the natural salinity gradient present at the field site. Changes in the community composition of the mats, as assayed by denaturing gradient gel electrophoresis (DGGE), as well as biomarker compounds produced in the mats were also monitored. The degree to which the mats kept in the greenhouse changed from the originally collected mats, as well as differences between high and low salinity mats will be discussed. Additional information is contained in the original extended

  9. Can lemmings control the expansion of woody plants on tundra?

    NASA Astrophysics Data System (ADS)

    Oksanen, Lauri; Oksanen, Tarja; Olofsson, Johan; Virtanen, Risto; Hoset, Katrine; Tuomi, Maria; Kyrö, Kukka

    2013-04-01

    The ongoing expansion of woody vegetation in the arctic, due to global warming, creates a positive feed back loop. Increasing abundance of woody plants reduces surface albedo both directly and via speeding up snow melt. Thus a successively greater fraction of incoming solar radiation is absorbed and converted to heat. Browsing mammals - both big and small - can prevent this by consuming woody plants. However, the grazer/browser community of many tundra areas is dominated by brown/Norwegian lemmings (Lemmus spp.) which eat graminoids and mosses and cannot use woody plants as forage. It would seem a priori likely that in such areas, mammalian herbivores speed up the expansion of woody plants by improving the chances of their seedlings to get established. We studied the impact of lemmings on woody plants by constructing lemming proof exclosures within piece high-altitude tundra at Joatkanjávri, northernmost Norway. The exclosures were constructed in 1998, during a period of low lemming densities, in snow-beds, where Norwegian lemmings (L. lemmus) were the only ecologically significant herbivorous mammals. (Reindeer migrate through the area in May, when snow-beds are inaccessible for them; during the fall migration, the area represents a dead end and is therefore avoided.) We chose pairs of maximally similar vegetation patches of 0.5 by 0.5 m and randomly assigned one of each pair to become an exclosure while the other plot was left open. The initial state of the vegetation was documented by the point frequency method. In 2008, after the 2007 lemming outbreak, the same documentation was repeated; thereafter the plots were harvested, the vegetation was sorted to species, oven dried and weighed. Exclusion of lemmings resulted to pronounced increase in community level plant biomass. Evergreen woody plants were especially favored by the exclusion of lemming: their above-ground biomass in exclosures was 14 times as great as their biomass on open reference plots. The

  10. Water track distribution and effects on carbon dioxide flux in an eastern Siberian upland tundra landscape

    NASA Astrophysics Data System (ADS)

    Curasi, Salvatore R.; Loranty, Michael M.; Natali, Susan M.

    2016-04-01

    Shrub expansion in tundra ecosystems may act as a positive feedback to climate warming, the strength of which depends on its spatial extent. Recent studies have shown that shrub expansion is more likely to occur in areas with high soil moisture and nutrient availability, conditions typically found in sub-surface water channels known as water tracks. Water tracks are 5–15 m wide channels of subsurface water drainage in permafrost landscapes and are characterized by deeper seasonal thaw depth, warmer soil temperatures, and higher soil moisture and nutrient content relative to adjacent tundra. Consequently, enhanced vegetation productivity, and dominance by tall deciduous shrubs, are typical in water tracks. Quantifying the distribution of water tracks may inform investigations of the extent of shrub expansion and associated impacts on tundra ecosystem carbon cycling. Here, we quantify the distribution of water tracks and their contribution to growing season CO2 dynamics for a Siberian tundra landscape using satellite observations, meteorological data, and field measurements. We find that water tracks occupy 7.4% of the 448 km2 study area, and account for a slightly larger proportion of growing season carbon uptake relative to surrounding tundra. For areas inside water tracks dominated by shrubs, field observations revealed higher shrub biomass and higher ecosystem respiration and gross primary productivity relative to adjacent upland tundra. Conversely, a comparison of graminoid-dominated areas in water tracks and inter-track tundra revealed that water track locations dominated by graminoids had lower shrub biomass yet increased net uptake of CO2. Our results show water tracks are an important component of this landscape. Their distribution will influence ecosystem structural and functional responses to climate, and is therefore of importance for modeling.

  11. Using Image Segmentation to Identify Tundra Vegetation Variability in High Resolution Satellite Images

    NASA Astrophysics Data System (ADS)

    Lazow, Z.; Roemke, L.; Loranty, M. M.

    2014-12-01

    Arctic tundra ecosystems will play an important role in the global carbon cycle in coming decades and centuries. Amplified climate warming at high northern latitudes has stimulated carbon uptake via plant productivity, while thawing permafrost is releasing carbon to the atmosphere. Accurately quantifying the effect of changing tundra ecosystems on global climate will require detailed understanding of both of these processes. In this context, accounting for the spatial variation of landscape features is critical to creating carbon budgets for ecosystems and regions, and for forecasting the effects of climate change in the tundra. Water tracks and other areas that feature channelized subsurface water flow are landscape features with distinct differences in carbon stocks and fluxes relative to adjacent upland tundra areas. Numerous studies have shown that water tracks and flowpaths have greater water and nutrient availability that leads relatively high carbon stocks and rates of carbon uptake. However a clear understanding of the relative proportion of tundra ecosystems that are comprised of these landscape features is lacking. Recently developed fine-scale remote sensing technology allows for the spatial analysis of tundra landscapes and specifically water tracks. This study automates process of distinguishing water tracks through the use of image classification and segmentation techniques on high-resolution satellite imagery. Both supervised and unsupervised classification techniques identify water tracks as distinctive and tundra landscape features. Unlike the unsupervised classification, edge detection and region-thresholding algorithms in the supervised classification differentiates water tracks from locations with high productivity by assessing connectivity shape. Depending on the area of inquiry, water tracks comprise roughly 10%-25% of the landscape. Field observations indicate that water tracks have greater plant productivity, and rates of carbon cycling

  12. Astronaut Thomas Mattingly performs EVA during Apollo 16 transearth coast

    NASA Technical Reports Server (NTRS)

    1972-01-01

    Astronaut Thomas K. Mattingly II, command module pilot of the Apollo 16 lunar landing mission, performs extravehicular activity (EVA) during the Apollo 16 transearth coast. mattingly is assisted by Astronaut Charles M. Duke Jr., lunar module pilot. Mattingly inspected the SIM bay of the Service Module, and retrieved film from the Mapping and Panoramic cameras. Mattingly is wearing the helmet of Astronaut John W. Young, commander. The helmet's lunar extravehicular visor assembly helped protect Mattingly's eyes frmo the bright sun. This view is a frame from motion picture film exposed by a 16mm Maurer camera.

  13. ChemMatCARS Data Archive

    DOE Data Explorer

    ChemMatCARS is a high-brilliance national synchrotron x-ray facility dedicated primarily to static and dynamic condensed matter chemistry and materials science. The scientific focus of the facility includes the study of surface and interfacial properties of liquids and solids as well as their bulk structure at atomic, molecular and mesoscopic length scales with high spatial and energy resolution. Experimental techniques supported by the facility include: 1) Liquid Surface X-ray Scattering; 2) Solid Surface X-ray Scattering; 3) Time-Resolved Crystallography; 4) Micro-Crystal Diffraction; 5) Small and Wide-angle X-ray Scattering. The data archive referenced here contains data for various components along the beamline within the First Optics Enclosure and is intended to be input or parameter data. See the Science Nuggets at http://cars9.uchicago.edu/chemmat/pages/nuggets.html for leads to some of the research conducted at the ChemMatCARS beamline.

  14. Microbial mats: an ecological niche for fungi

    PubMed Central

    Cantrell, Sharon A.; Duval-Pérez, Lisabeth

    2013-01-01

    Fungi were documented in tropical hypersaline microbial mats and their role in the degradation of complex carbohydrates (exopolymeric substance – EPS) was explored. Fungal diversity is higher during the wet season with Acremonium, Aspergillus, Cladosporium, and Penicillium among the more common genera. Diversity is also higher in the oxic layer and in young and transient mats. Enrichments with xanthan (a model EPS) show that without antibiotics (full community) degradation is faster than enrichments with antibacterial (fungal community) and antifungal (bacterial community) agents, suggesting that degradation is performed by a consortium of organisms (bacteria and fungi). The combined evidence from all experiments indicates that bacteria carried out approximately two-third of the xanthan degradation. The pattern of degradation is similar between seasons and layers but degradation is faster in enrichments from the wet season. The research suggests that fungi thrive in these hypersaline consortia and may participate in the carbon cycle through the degradation of complex carbohydrates. PMID:23577004

  15. Bioflumology: Microbial mat growth in flumes

    NASA Astrophysics Data System (ADS)

    Airo, A.; Weigert, S.; Beck, C.

    2014-04-01

    The emergence of oxygenic photosynthesis resulted in a transformational change of Earth's geochemical cycles and the subsequent evolution of life. However, it remains vigorously debated when this metabolic ability had evolved in cyanobacteria. This is largely because studies of Archean microfossil morphology, molecular biomarkers, and isotopic characteristics are frequently ambiguous. However, the high degree of morphological similarities between modern photosynthetic and Archean fossil mats has been interpreted to indicate phototactic microbial behavior or oxygenic photosynthesis. In order to better evaluate the relationship between mat morphology and metabolism, we here present a laboratory set-up for conducting month-long experiments in several sterilizable circular flumes designed to allow single-species cyanobacterial growth under adjustable fluid-flow conditions and protected from contamination.

  16. The southernmost Andean Mountain soils: a toposequence from Nothofagus Forest to Sub Antarctic Tundra at Ushuaia, Tierra del Fuego

    NASA Astrophysics Data System (ADS)

    Firme Sá, Mariana M.; Schaefer, Carlos E.; Loureiro, Diego C.; Simas, Felipe N.; Francelino, Marcio R.; Senra, Eduardo O.

    2015-04-01

    Located at the southern tip of the Fuegian Andes Cordilhera, the Martial glacier witnessed a rapid process of retreat in the last century. Up to now little is known about the development and genesis of soils of this region. A toposequence of six soils, ranging from 430-925 m a.s.l, was investigated, with emphasis on genesis, chemical and mineralogical properties. The highest, youngest soil is located just below the Martial Glacier Martial Sur sector, and the lowest soils occur on sloping moraines under Nothofagus pumilio forests. Based on chemical, physical and mineralogical characteristics, the soils were classified according to the Soil taxonomy, being keyed out as Inceptisols and Entisols. Soil parent material of the soil is basically moraines, in which the predominant lithic components dominated by metamorphic rocks, with allochthonous contributions of wind-blown materials (very small fragments of volcanic glass) observed by hand lens in all horizons, except the highest profile under Tundra. In Nothofagus Deciduous Forests at the lowest part of the toposequence, poorly developed Inceptisols occur with Folistic horizons, with mixed "andic" and "spodic" characters, but with a predominance of andosolization (Andic Drystrocryepts). Under Tundra vegetation, Inceptisols are formed under hydromorphism and andosolization processes (Oxiaquic Dystrocrepts and Typic Dystrocrepts). On highland periglacial environments, soils without B horizon with strong evidence of cryoturbation and cryogenesis occur, without present-day permafrost down to 2 meters (Typic Cryorthents and Lithic Haploturbels). The mountain soils of Martial glacier generalize young, stony and rich in organic matter, with the exception of barely vegetated Tundra soils at higher altitudes. The forest soils are more acidic and have higher Al3+activity. All soils are dystrophic, except for the highest profile of the local periglacial environment. The organic carbon amounts are higher in forest soils and

  17. The effects of mats on back and leg fatigue.

    PubMed

    Kim, J Y; Stuart-Buttle, C; Marras, W S

    1994-02-01

    Prolonged standing is common in many industrial workplaces. It is also quite common for workers to complain of discomfort in the back and legs as a result of prolonged standing. Mats are often provided for the worker to relieve this fatigue. However, there is no quantitative evidence that these mats relieve leg and back fatigue. Five subjects were asked to stand on a concrete surface and two mat surfaces for prolonged periods of time. Spectral electromyographic analyses indicated that mats reduced localized muscle fatigue in the erector spinae muscle only. Furthermore, this fatigue reduction occurred only with the more compressible of the two mats tested. These results imply that localized muscular fatigue in the leg may not be relieved with 'anti-fatigue' mats, and some of these mats only benefit the back. PMID:15676945

  18. Mycorrhizal colonization mediated by species interactions in arctic tundra.

    PubMed

    Urcelay, Carlos; Bret-Harte, M Syndonia; Díaz, Sandra; Chapin, F Stuart

    2003-11-01

    The Alaskan tussock tundra is a strongly nutrient-limited ecosystem, where almost all vascular plant species are mycorrhizal. We established a long-term removal experiment to document effects of arctic plant species on ecto- and ericoid mycorrhizal fungi and to investigate whether species interactions and/or nutrient availability affect mycorrhizal colonization. The treatments applied were removal of Betula nana ( Betulaceae, dominant deciduous shrub species), removal of Ledum palustre ( Ericaceae, dominant evergreen shrub species), control (no removal), and each of these three treatments with the addition of fertilizer. After 3 years of Ledum removal and fertilization, we found that overall ectomycorrhizal colonization in Betula was significantly reduced. Changes in ectomycorrhizal morphotype composition in removal and fertilized treatments were also observed. These results suggest that the effect of Ledum on Betula's mycorrhizal roots is due to sequestration of nutrients by Ledum, leading to reduced nutrient availability in the soil. In contrast, ericoid mycorrhizal colonization was not affected by fertilization, but the removal of Betula and to a lower degree of Ledum resulted in a reduction of ericoid mycorrhizal colonization suggesting a direct effect of these species on ericoid mycorrhizal colonization. Nutrient availability was only higher in fertilized treatments, but caution should be taken with the interpretation of these data as soil microbes may effectively compete with the ion exchange resins for the nutrients released by plant removal in these nutrient-limited soils. PMID:12905060

  19. Modelling tundra vegetation response to recent arctic warming.

    PubMed

    Miller, Paul A; Smith, Benjamin

    2012-01-01

    The Arctic land area has warmed by > 1 °C in the last 30 years and there is evidence that this has led to increased productivity and stature of tundra vegetation and reduced albedo, effecting a positive (amplifying) feedback to climate warming. We applied an individual-based dynamic vegetation model over the Arctic forced by observed climate and atmospheric CO(2) for 1980-2006. Averaged over the study area, the model simulated increases in primary production and leaf area index, and an increasing representation of shrubs and trees in vegetation. The main underlying mechanism was a warming-driven increase in growing season length, enhancing the production of shrubs and trees to the detriment of shaded ground-level vegetation. The simulated vegetation changes were estimated to correspond to a 1.75 % decline in snow-season albedo. Implications for modelling future climate impacts on Arctic ecosystems and for the incorporation of biogeophysical feedback mechanisms in Arctic system models are discussed. PMID:22864701

  20. Climate Forced Alpine Tundra Ecosystem Dynamics: A Model Approach

    NASA Astrophysics Data System (ADS)

    Jarosch, A. H.; Clarke, G. K.; Danby, R. K.; Hik, D. S.

    2007-12-01

    Insights concerning the future evolution of alpine ecosystems depend on understanding and simulating their response to climate change. Comprehensive studies of these regions require novel spatio-temporal computational models of climate-forced landscape/ecosystem interactions. As part of the International Polar Year (IPY) we are examining alpine tundra landscapes and ecosystems in the Kluane region of southwest Yukon, Canada. Based on the combination of long-term geophysical and ecological field studies and driven by different climate change scenarios, such a model is being used to explore the range of possible future scenarios for the region. As the first step in building such a complex model, we present a simplified, grid-based model to demonstrate potential changes in plant community distribution driven by key climate variables such as temperature and precipitation. A linear orographic precipitation model is used to downscale climate data which, in combination with a digital elevation model, forms the geophysical input for the model. Simplified ecological rules describing the potential state transition of different plant communities and land cover types are incorporated in the model in a cellular automation fashion. The response of the ecosystem to several different climate scenarios will be presented, including a set of North American Regional Reanalysis climate data. This simplified model is used to demonstrate the potential of such interdisciplinary simulations to gain deeper understanding of ecosystem evolution with climate change.

  1. The Archaea of a Hypersaline Microbial Mat

    NASA Astrophysics Data System (ADS)

    Robertson, C.; Spear, J. R.; Pace, N. R.

    2006-12-01

    The overarching goal of this work is to describe and understand the organismal composition within the domain Archaea for the microbial ecosystem of a hypersaline microbial mat. Sea salt is crystallized by solar evaporation at North America's largest saltworks, the Exportadora de Sal, in Guerrero Negro, Baja California Sur. Sea water flows through a series of evaporative basins with an increase in salinity until saturation is reached and halite crystallization begins. Several of these ponds are underlined with thick microbial mats. To date, it has not been known what kinds of organisms comprise these complex microbial ecosystems. Here, we report a survey of the stratified microbial communities for the distribution of representatives of Archaea in layers of the mats. This survey uses molecular approaches, based on cloning and sequencing of SSU rRNA genes for phylogenetic analyses, to determine the nature and extent of archaeal diversity that constitute these ecosystems. We compiled an altogether new phylogenetic backbone for the domain Archaea and placed representative sequences from this hypersaline analysis onto that framework. Analyses to date indicate the ubiquitous dominance of uncultured organisms of phylogenetic kinds not generally thought to be associated with hypersaline environments. Collectively, the results indicate that the diversity of life is extensive even in this seemingly inhospitable "extreme" environment.

  2. Domibacillus tundrae sp. nov., isolated from active layer soil of tussock tundra in Alaska, and emended description of the genus Domibacillus.

    PubMed

    Gyeong, Hye Ryeon; Baek, Kiwoon; Hwang, Chung Yeon; Park, Key Hun; Kim, Hye Min; Lee, Hong Kum; Lee, Yoo Kyung

    2015-10-01

    A novel Gram-stain-positive, spore-forming, aerobic, motile and rod-shaped bacterium designated strain PAMC 80007T was isolated from an active layer soil sample of Council, Alaska. Optimal growth of strain PAMC 80007T was observed at 30 °C, pH 7.0 and in the presence of 2 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequence indicated that strain PAMC 80007T belonged to the genus Domibacillus. This strain was closely related to Domibacillus enclensis (98.3 %), Domibacillus robiginosus (98.3 %) and Domibacillus indicus (97.2 %). Genomic DNA G+C content was 43.5 mol% and genomic relatedness analyses based on the average nucleotide identity and the genome-to-genome distance showed that strain PAMC 80007T is clearly distinguished from the closely related species of the genus Domibacillus. The major fatty acids (>5 %) were iso-C15 : 0 (24.7 %), C16 : 1ω11c (16.8 %), anteiso-C15 : 0 (16.5 %), C16 : 0 (15.6 %) and anteiso-C17 : 0 (8.7 %). The major respiratory isoprenoid quinones were menaquinone-6 (MK-6) and menaquinone-7 (MK-7), and the polar lipid profile contained diphosphatidylglycerol, phosphatidylglycerol, phosphoglycolipid, phospholipid and two unidentified lipids. meso-Diaminopimelic acid (type A1γ) was present in the cell-wall peptidoglycan, and the major whole-cell sugar was ribose with a minor quantity of glucose. Results from a polyphasic study suggested that strain PAMC 80007T represents a novel species of the genus Domibacillus for which the name Domibacillus tundrae sp. nov. is proposed. The type strain is PAMC 80007T ( = JCM 30371T = KCTC 33549T = DSM 29572T). An emended description of the genus Domibacillus is also provided. PMID:26296675

  3. Vectors and transmission dynamics for Setaria tundra (Filarioidea; Onchocercidae), a parasite of reindeer in Finland

    PubMed Central

    Laaksonen, Sauli; Solismaa, Milla; Kortet, Raine; Kuusela, Jussi; Oksanen, Antti

    2009-01-01

    Background Recent studies have revealed expansion by an array of Filarioid nematodes' into the northern boreal region of Finland. The vector-borne nematode, Setaria tundra, caused a serious disease outbreak in the Finnish reindeer population in 2003–05. The main aim of this study was to understand the outbreak dynamics and the rapid expansion of S. tundra in the sub arctic. We describe the vectors of S. tundra, and its development in vectors, for the first time. Finally we discuss the results in the context of the host-parasite ecology of S. tundra in Finland Results Development of S. tundra to the infective stage occurs in mosquitoes, (genera Aedes and Anopheles). We consider Aedes spp. the most important vectors. The prevalence of S. tundra naturally infected mosquitoes from Finland varied from 0.5 to 2.5%. The rate of development in mosquitoes was temperature-dependent. Infective larvae were present approximately 14 days after a blood meal in mosquitoes maintained at room temperature (mean 21 C), but did not develop in mosquitoes maintained outside for 22 days at a mean temperature of 14.1 C. The third-stage (infective) larvae were elongated (mean length 1411 μm (SD 207), and width 28 μm (SD 2)). The anterior end was blunt, and bore two liplike structures, the posterior end slight tapering with a prominent terminal papilla. Infective larvae were distributed anteriorly in the insect's body, the highest abundance being 70 larvae in one mosquito. A questionnaire survey revealed that the peak activity of Culicidae in the reindeer herding areas of Finland was from the middle of June to the end of July and that warm summer weather was associated with reindeer flocking behaviour on mosquito-rich wetlands. Conclusion In the present work, S. tundra vectors and larval development were identified and described for the first time. Aedes spp. mosquitoes likely serve as the most important and competent vectors for S. tundra in Finland. Warm summers apparently promote

  4. Modeling carbon-nutrient interactions during the early recovery of tundra after fire.

    PubMed

    Jiang, Yueyang; Rastetter, Edward B; Rocha, Adrian V; Pearce, Andrea R; Kwiatkowski, Bonnie L; Shaver, Gaius R

    2015-09-01

    Fire frequency has dramatically increased in the tundra of northern Alaska, USA, which has major implications for the carbon budget of the region and the functioning of these ecosystems, which support important wildlife species. We investigated the postfire succession of plant and soil carbon (C), nitrogen (N), and phosphorus (P) fluxes and stocks along a burn severity gradient in the 2007 Anaktuvuk River fire scar in northern Alaska. Modeling results indicated that the early regrowth of postfire tundra vegetation was limited primarily by its canopy photosynthetic potential, rather than nutrient availability, because of the initially low leaf area and relatively high inorganic N and P concentrations in soil. Our simulations indicated that the postfire recovery of tundra vegetation was sustained predominantly by the uptake of residual inorganic N (i.e., in the remaining ash), and the redistribution of N and P from soil organic matter to vegetation. Although residual nutrients in ash were higher in the severe burn than the moderate burn, the moderate burn recovered faster because of the higher remaining biomass and consequent photosynthetic potential. Residual nutrients in ash allowed both burn sites to recover and exceed the unburned site in both aboveground biomass and production five years after the fire. The investigation of interactions among postfire C, N, and P cycles has contributed to a mechanistic understanding of the response of tundra ecosystems to fire disturbance. Our study provided insight on how the trajectory of recovery of tundra from wildfire is regulated during early succession. PMID:26552271

  5. Permafrost collapse after shrub removal shifts tundra ecosystem to a methane source

    NASA Astrophysics Data System (ADS)

    Nauta, Ake L.; Heijmans, Monique M. P. D.; Blok, Daan; Limpens, Juul; Elberling, Bo; Gallagher, Angela; Li, Bingxi; Petrov, Roman E.; Maximov, Trofim C.; van Huissteden, Jacobus; Berendse, Frank

    2015-01-01

    Arctic tundra ecosystems are warming almost twice as fast as the global average. Permafrost thaw and the resulting release of greenhouse gases from decomposing soil organic carbon have the potential to accelerate climate warming. In recent decades, Arctic tundra ecosystems have changed rapidly, including expansion of woody vegetation, in response to changing climate conditions. How such vegetation changes contribute to stabilization or destabilization of the permafrost is unknown. Here we present six years of field observations in a shrub removal experiment at a Siberian tundra site. Removing the shrub part of the vegetation initiated thawing of ice-rich permafrost, resulting in collapse of the originally elevated shrub patches into waterlogged depressions within five years. This thaw pond development shifted the plots from a methane sink into a methane source. The results of our field experiment demonstrate the importance of the vegetation cover for protection of the massive carbon reservoirs stored in the permafrost and illustrate the strong vulnerability of these tundra ecosystems to perturbations. If permafrost thawing can more frequently trigger such local permafrost collapse, methane-emitting wet depressions could become more abundant in the lowland tundra landscape, at the cost of permafrost-stabilizing low shrub vegetation.

  6. Boundary layer O3 dynamics and deposition to tundra during a summer in the Alaskan Arctic

    NASA Astrophysics Data System (ADS)

    Van Dam, B. A.; Helmig, D.; Doskey, P. V.; Oltmans, S. J.; Boylan, P.

    2014-12-01

    Atmospheric turbulence quantities, boundary layer O3 levels and deposition to the tundra surface were investigated at Toolik Lake, AK during the 2011 summer season. Beginning immediately after snowmelt a diurnal cycle in ambient O3 developed, and O3 values measured over tundra throughout the summer varied significantly between nighttime minima of 5 ppbv and daytime maxima of 50 ppbv. The mean amplitude of the diurnal cycle in surface O3 following snowmelt was 13 ppbv, far larger than observed at other high Arctic locations. The diurnal cycle is attributed to a combination of surface deposition to the tundra and stable boundary layer conditions at night, and the entrainment of O3 from higher in the atmosphere during increased daytime mixing. The mean O3 deposition velocity during the month of June was 0.11 cm s-1. O3 deposition to tundra exhibited a diurnal cycle, with daytime mean of 0.2 cm s-1 and nighttime mean of 0.08 cm s-1. These values are slightly lower than previously reported summertime deposition velocities in the northern latitudes over tundra or fen, although measurements for comparison were limited.

  7. [The processes of methane formation and oxidation in the soils of the Russian arctic tundra].

    PubMed

    Berestovskaia, Iu Iu; Rusanov, I I; Vasil'eva, L V; Pimenov, N V

    2005-01-01

    Methane emission from the following types of tundra soils was studied: coarse humic gleyey loamy cryo soil, peaty gley soil, and peaty gleyey midloamy cryo soil of the arctic tundra. All the soils studied were found to be potential sources of atmospheric methane. The highest values of methane emission were recorded in August at a soil temperature of 8-10 degrees C. Flooded parcels were the sources of atmospheric methane throughout the observation period. The rates of methane production and oxidation in tundra soils of various types at 5 and 15 degrees C were studied by the radioisotope method. Methane oxidation was found to occur in bog water, in the green part of peat moss, and in all the soil horizons studied. Methane formation was recorded in the horizons of peat, in clay with plant roots, and in peaty moss dust of the bogey parcels. At both temperatures, the methane oxidation rate exceeded the rate of methane formation in all the horizons of the mossy-lichen tundra and of the bumpy sinkhole complex. Methanogenesis prevailed only in a sedge-peat moss bog at 15 degrees C. Enrichment bacterial cultures oxidizing methane at 5 and 15 degrees C were obtained. Different types of methanotrophic bacteria were shown to be responsible for methane oxidation under these conditions. A representative of type I methylotrophs oxidized methane at 5 degrees C, and Methylocella tundrae, a psychroactive representative of an acidophilic methanotrophic genus Methylocella, at 15 degrees C. PMID:15938404

  8. Atmospheric methane sources - Alaskan tundra bogs, an alpine fen, and a subarctic boreal marsh

    NASA Technical Reports Server (NTRS)

    Sebacher, D. I.; Harriss, R. C.; Grice, S. S.; Bartlett, K. B.; Sebacher, S. M.

    1986-01-01

    Methane (CH4) flux measurements from Alaska tundra bogs, an alpine fen, and a subarctic boreal marsh were obtained at field sites ranging from Prudhoe Bay on the coast of the Arctic Ocean to the Alaskan Range south of Fairbanks during August 1984. In the tundra, average CH4 emission rates varied from 4.9 mg CH4 per sq m per day (moist tundra) to 119 mg CH4 per sq m per day (waterlogged tundra). Fluxes averaged 40 mg CH4 per sq m per day from wet tussock meadows in the Brooks Range and 289 mg Ch4 per sq m per day from an alpine fen in the Alaskan Range. The boreal marsh had an average CH4 emission rate of 106 mg CH4 per sq m per day. Significant emissions were detected in tundra areas where peat temperatures were as low as 4 C, and permafrost was only 25 cm below the ground surface. Emission rates from the 17 sites sampled were found to be logarithmically related to water levels at the sites. Extrapolation of the data to an estimate of the total annual CH4 emission from all arctic and boreal wetlands suggests that these ecosystems are a major source of atmospheric CH4 and could account for up to 23 percent of global CH4 emissions from wetlands.

  9. USE OF GREENHOUSE CHAMBERS FOR ENHANCING GROWTH OF TUNDRA TRANSPLANTS ON THIN GRAVEL FILL IN PRUDHOE BAY, ALASKA

    EPA Science Inventory

    An approach is presented that could facilitate disturbed tundra revegetation and monitoring in Alaska North Slope Oil Fields. xperiments were conducted on an abandoned drilling pad where the gravel was removed to a thin layer (Ca. 20 am) above tundra grade and mixed with underlyi...

  10. Variation in bird's originating nitrogen availability limits High Arctic tundra development over last 2000 year (Hornsund, Svalbard)

    NASA Astrophysics Data System (ADS)

    Skrzypek, Grzegorz; Wojtuń, Bronisław; Hua, Quan; Richter, Dorota; Jakubas, Dariusz; Wojczulanis-Jakubas, Katarzyna; Samecka-Cymerman, Aleksandra

    2016-04-01

    Arctic and subarctic regions play important roles in the global carbon balance. However, nitrogen (N) deficiency is a major constraint for organic carbon sequestration in the High Arctic. Hence, the identification of the relative contributions from different N-sources is critical for understanding the constraints that limit tundra growth. The stable nitrogen composition of the three main N-sources and numerous plants were analyzed in ten tundra types (including those influenced by seabirds) in the Fuglebekken catchment (Hornsund, Svalbard, 77°N 15°E). The percentage of the total tundra N-pool provided by seabirds' feces (from planktivorous colonially breeding little auks Alle alle), ranged from 0-21% in Patterned-ground tundra to 100% in Ornithocoprophilous tundra. The total N-pool utilized by tundra plants in the studied catchment originated from birds (36%), atmospheric deposition (38%), and N2-fixation (26%). The results clearly show that N-pool in the tundra is significantly supplemented by nesting seabirds. Thus, if they experienced climate change induced substantial negative environmental pressure, it would adversely influence the tundra N-budget (Skrzypek et al. 2015). The growth rates and the sediment thickness (<15cm) in different tundra types varied considerably but the tundra age was similar in the whole area, <450 cal BP. The only exception was Ornithocoprophilous bird-N rich tundra with very diverse ages ranging from 235 to 2300 cal BP and thickness up to 110 cm. The growth rates for this tundra (62 cm core, 18 AMS 14C dates) were high (1.5-3.0 mm/yr) between 1568 and 1804 AD and then substantially declined for the period between 1804 and 1929 AD (0.2 mm/yr). These findings deliver an additional argument, that the organic matter accumulation is driven not only directly by climatic conditions but also by birds' contribution to the tundra N-pool. Skrzypek G, Wojtuń B, Richter D, Jakubas D, Wojczulanis-Jakubas K, Samecka-Cymerman A, 2015

  11. Controls over nutrient flow through plants and microbes in Arctic tundra. Final technical report

    SciTech Connect

    Chapin, F.S. III

    1995-01-01

    We successfully developed a series of models to explore the importance of species differences in phenologies of growth and nitrogen uptake to competitive interactions in upland tussock tundra. We developed growth models for 4 major tussock tundra species, based on observed growth rates and phenologies. We found that differences in phenology and nutrient use strategy could permit coexistence of some, but not all of the tundra plants modeled. The plant that was the best competitor, because of its rapid growth rate and superior ability to retranslocate nitrogen, may be naturally limited in its competitive ability by its tussock growth form. The mechanisms behind this limitation, and the contributions of patterns of mortality to observed production, will be explored in future modeling and experimental studies. In addition, our models point out that our understanding of the dynamics of nitrogen supply is still inadequate.

  12. Shrub Abundance Mapping in Arctic Tundra with Misr

    NASA Astrophysics Data System (ADS)

    Duchesne, R.; Chopping, M. J.; Wang, Z.; Schaaf, C.; Tape, K. D.

    2013-12-01

    Over the last 60 years an increase in shrub abundance has been observed in the Arctic tundra in connection with a rapid surface warming trend. Rapid shrub expansion may have consequences in terms of ecosystem structure and function, albedo, and feedbacks to climate; however, its rate is not yet known. The goal of this research effort is thus to map large scale changes in Arctic tundra vegetation by exploiting the structural signal in moderate resolution satellite remote sensing images from NASA's Multiangle Imaging SpectroRadiometer (MISR), mapped onto a 250m Albers Conic Equal Area grid. We present here large area shrub mapping supported by reference data collated using extensive field inventory data and high resolution panchromatic imagery. MISR Level 1B2 Terrain radiance scenes from the Terra satellite from 15 June-31 July, 2000 - 2010 were converted to surface bidirectional reflectance factors (BRF) using MISR Toolkit routines and the MISR 1 km LAND product BRFs. The red band data in all available cameras were used to invert the RossThick-LiSparse-Reciprocal BRDF model to retrieve kernel weights, model-fitting RMSE, and Weights of Determination. The reference database was constructed using aerial survey, three field campaigns (field inventory for shrub count, cover, mean radius and height), and high resolution imagery. Tall shrub number, mean crown radius, cover, and mean height estimates were obtained from QuickBird and GeoEye panchromatic image chips using the CANAPI algorithm, and calibrated using field-based estimates, thus extending the database to over eight hundred locations. Tall shrub fractional cover maps for the North Slope of Alaska were constructed using the bootstrap forest machine learning algorithm that exploits the surface information provided by MISR. The reference database was divided into two datasets for training and validation. The model derived used a set of 19 independent variables(the three kernel weights, ratios and interaction terms

  13. Fire disturbance effects on land surface albedo in Alaskan tundra

    NASA Astrophysics Data System (ADS)

    French, Nancy H. F.; Whitley, Matthew A.; Jenkins, Liza K.

    2016-03-01

    The study uses satellite Moderate Resolution Imaging Spectroradiometer albedo products (MCD43A3) to assess changes in albedo at two sites in the treeless tundra region of Alaska, both within the foothills region of the Brooks Range, the 2007 Anaktuvuk River Fire (ARF) and 2012 Kucher Creek Fire (KCF). Results are compared to each other and other studies to assess the magnitude of albedo change and the longevity of impact of fire on land surface albedo. In both sites there was a marked decrease of albedo in the year following the fire. In the ARF, albedo slowly increased until 4 years after the fire, when it returned to albedo values prior to the fire. For the year immediately after the fire, a threefold difference in the shortwave albedo decrease was found between the two sites. ARF showed a 45.3% decrease, while the KCF showed a 14.1% decrease in shortwave albedo, and albedo is more variable in the KCF site than ARF site 1 year after the fire. These differences are possibly the result of differences in burn severity of the two fires, wherein the ARF burned more completely with more contiguous patches of complete burn than KCF. The impact of fire on average growing season (April-September) surface shortwave forcing in the year following fire is estimated to be 13.24 ± 6.52 W m-2 at the ARF site, a forcing comparable to studies in other treeless ecosystems. Comparison to boreal studies and the implications to energy flux are discussed in the context of future increases in fire occurrence and severity in a warming climate.

  14. Responses of Tundra Ecosystems to Environmental Change: Observational and Experimental Results

    NASA Astrophysics Data System (ADS)

    Henry, G. H.

    2004-05-01

    Evidence of environmental changes due to human-enhanced climate warming continues to accumulate from polar regions. Responses in tundra and taiga ecosystems to climate changes have been variable because of the wide range in process response rates, from metabolic processes to adjustments in ecosystem carbon balance, and the variability in environmental settings across local to regional scales. For example, strong increases in rates of plant growth and changes in species composition and abundance have been observed in parts of the Low Arctic, but very little change has been measured in high arctic tundra. A dramatic increase in the cover of deciduous shrubs in areas of the western North American Arctic is predicted to result in positive feedbacks to soil temperature, through increased surface roughness and snow depth, and to atmospheric heating by reducing albedo. Increased shrub cover has also been found in long-term experimental warming studies conducted throughout the tundra biome as part of the International Tundra Experiment (ITEX). Warming is also affecting the carbon balance of tundra and taiga, which hold 25% of the soil carbon of global terrestrial ecosystems. However, trajectories of these changes are largely unknown for most northern systems, and differ because of initial conditions of the carbon and nutrient economy. Over the longer-term, the positive increases in plant growth may be constrained by negative feedbacks to nutrient cycling, as increases in C:N ratios of plant litter slow the release of nitrogen to soils. However, nitrogen availability has been shown to increase in response to short-term warming. In this presentation, I will review the responses of tundra ecosystems to climate variability and change, both through observational and experimental studies.

  15. Can Long-Term Precipitation Trends Explain Net Annual Carbon Loss From High Elevation Alpine Tundra?

    NASA Astrophysics Data System (ADS)

    Knowles, J. F.; Blanken, P.; Williams, M. W.

    2013-12-01

    Five continuous years of eddy covariance measurements over predominantly snow-free alpine tundra on Niwot Ridge, Colorado show that ecosystem respiration dominates over gross primary productivity on an annual basis, and that this ecosystem is a significant source of carbon to the atmosphere over long periods of time. Long-term data also show that precipitation has increased since the 1960s, in contrast to modeled forecasts that generally predict decreasing precipitation through the 21st century across the Rocky Mountain region. To constrain the specific relationship between precipitation and the alpine tundra carbon cycle, we tested the degree to which precipitation and soil moisture determined respiration fluxes over the course of three years, and across a range of 17 sites, including xeric, mesic, and hydric alpine tundra soils, within the footprint of ongoing eddy covariance measurements. Overall, we found that respiration from this ecosystem was principally moisture-limited. Cumulatively, the highest respiration rates were measured from hydric soils associated with seasonal ice lenses and perched water tables, however, growing season respiration rates peaked in mesic areas when hydric soils were saturated. Respiration from xeric soils increased with soil moisture, but fluxes from these areas were small in magnitude relative to mesic and hydric soils. Changes in precipitation and resultant soil moisture thus invoked a bidirectional response from alpine tundra soils, as moisture and respiration were positively correlated in some areas, but negatively correlated in others, depending on landscape position and prevailing soil moisture regime. Interannually, however, respiration fluxes were highest in wet years, indicating that moisture stimulated respiration from xeric and mesic soils more than it was suppressed from hydric soils. In sum, increased precipitation over the last half-century may be augmenting respiratory fluxes from alpine tundra, but changes in

  16. Reduced postfire tree regeneration along a boreal forest-forest-tundra transect in northern Quebec

    SciTech Connect

    Sirois, L.; Payette, S. )

    1991-04-01

    The large 1950s fires that burned > 5,500 km{sup 2} of land across a south-to-north climatic gradient in northern Quebec provide an opportunity to evaluate the role of fire in forest-tundra development on a demographic basis. The tree population density before and {approx} 30 yr after fire was estimated by censusing trees in plots of 400 m{sup 2} located in upland and lowland within four representative ecoregions of northern Quebec. The analysis of tree recruitment before and after fire, in 410 randomly selected sites along a transect crossing the upper boreal forest and forest-tundra zones, indicated that wildfires induced substantial depletion of tree populations. Taken as a whole, fires have significantly reduced the density of black spruce populations in forest-tundra uplands, but not in the lowlands. Sustained reduction of tree population density after several destructive fires appears as one of the main deforestation processed in the subarctic zone. This leads to the patchy distribution of forest stands and scattered tree populations typical of the forest-tundra biome. Comparisons with paleoecological data suggest that the impact of the 1950s fires contributed to the expansion of the forest tundra into the upper boreal forest. The ecological impact of these fires was probably similar to those fires responsible for development of the forest tundra during the Holocene. It is suggested that the fire-climate interaction should be considered in order to predict the ecological impact of warming climate on high-latitude forest ecosystems.

  17. Flow-induced Development of Unicellular Cyanobacterial Mats

    NASA Astrophysics Data System (ADS)

    Gong, J.; Tice, M. M.

    2011-12-01

    Microbial mats/biofilms are abundant microbial growth structures throughout the history of life on Earth. Understanding the mechanisms for their morphogenesis and interactions with physical sedimentary forces are important topics that allow deeper understanding of related records. When subjected to hydrodynamic influences, mats are known to vary in morphology and structure in response to fluid shear, yet mechanistically, the underlying cellular architecture due to interactions with flow remain unexplained. Moreover, mats are found to emerge larger scale roughness elements and modified cohesive strength growing under flow. It is a mystery how and why these mat-community-level features are linked in association with modified boundary layers at the mats surface. We examined unicellular cyanobacterium Synechocystis sp. PCC 6803 in a circular flow bioreactor designed to maintain a fixed set of hydrodynamic conditions. The use of monoculture strains and unidirectional currents, while not replicating natural mat systems (almost certainly multi-species and often multi-directional currents under complex wind or tidal wave actions), helps to simplify these systems and allows for specific testing of hypotheses regarding how mats evolve distinctive morphologies induced by flow. The unique design of the reactor also makes measurements such as critical erosional shear stress of the mats possible, in addition to microscopic, macroscopic imaging and weeks of continuous mats growth monitoring. We report the finding that linear chains, filament-like cell groups were present from unicellular cyanobacterial mats growing under flow (~1-5 cm/s) and these structures are organized within ~1-3mm size streamers and ~0.5-1mm size nodular macrostructures. Ultra-small, sub-micron thick EPS strings are observed under TEM and are likely the cohesive architectural elements in mats across different fluid regimes. Mat cohesion generally grows with and adapts to increasing flow shear stress within

  18. A Cyanine Dye Encapsulated Porous Fibrous Mat for Naked-Eye Ammonia Sensing.

    PubMed

    Ji, Chendong; Ma, Lijing; Yin, Meizhen; Yang, Wantai; Pan, Kai

    2016-08-19

    Electrospun ultrathin fiber-based sensors are desirable because of their practicality and sensitivity. Ammonia-detection systems are in high demand in different areas, including the industrial and agricultural fields. However, current technologies rely on large and complex instruments that restrict their actual utilization. Herein, we report a flexible naked-eye ammonia sensor, the polylactic acid-cyanine (PLA-Cy) fibrous mat, which was fabricated by blending a carboxyl-functionalized cyanine dye (D1) into electospun PLA porous fibers. The sensing mat was shown to undergo a naked-eye-detectable color change from white to blue upon exposure to ammonia vapor. The mat showed high selectivity to ammonia gas with a detection limit of 3.3 ppm. Aggregated D1 was first encapsulated by PLA and was then ionized by NH3 . These mechanisms were examined by photophysical studies and scanning electron microscopy. The aggregation-deaggregation process of D1 in the PLA-Cy fibrous mat led to the color change. This work provides a facile method for the naked-eye detection of ammonia and a novel strategy for the use of organic dyes in ammonia sensing. PMID:27411059

  19. Microscale characterization of dissolved organic matter production and uptake in marine microbial mat communities

    NASA Technical Reports Server (NTRS)

    Paerl, H. W.; Bebout, B. M.; Joye, S. B.; Des Marais, D. J.

    1993-01-01

    Intertidal marine microbial mats exhibited biologically mediated uptake of low molecular weight dissolved organic matter (DOM), including D-glucose, acetate, and an L-amino acid mixture at trace concentrations. Uptake of all compounds occurred in darkness, but was frequently enhanced under natural illumination. The photosystem 2 inhibitor, 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU) generally failed to inhibit light-stimulated DOM uptake. Occasionally, light plus DCMU-amended treatments led to uptake rates higher than light-incubated samples, possibly due to phototrophic bacteria present in subsurface anoxic layers. Uptake was similar with either 3H- or 14C-labeled substrates, indicating that recycling of labeled CO2 via photosynthetic fixation was not interfering with measurements of light-stimulated DOM uptake. Microautoradiographs showed a variety of pigmented and nonpigmented bacteria and, to a lesser extent, cyanobacteria and eucaryotic microalgae involved in light-mediated DOM uptake. Light-stimulated DOM uptake was often observed in bacteria associated with sheaths and mucilage surrounding filamentous cyanobacteria, revealing a close association of organisms taking up DOM with photoautotrophic members of the mat community. The capacity for dark- and light-mediated heterotrophy, coupled to efficient retention of fixed carbon in the mat community, may help optimize net production and accretion of mats, even in oligotrophic waters.

  20. Super-Hydrophobic High Throughput Electrospun Cellulose Acetate (CA) Nanofibrous Mats as Oil Selective Sorbents

    NASA Astrophysics Data System (ADS)

    Han, Chao

    The threat of oil pollution increases with the expansion of oil exploration and production activities, as well as the industrial growth around the world. Use of sorbents is a common method to deal with the oil spills. In this work, an advanced sorbent technology is described. A series of non-woven Cellulose Acetate (CA) nanofibrous mats with a 3D fibrous structure were synthesized by a novel high-throughput electrospinning technique. The precursor was solutions of CA/ acetic acid-acetone in various concentrations. Among them, 15.0% CA exhibits a superhydrophobic surface property, with a water contact angle of 128.95°. Its oil sorption capacity is many times higher the oil sorption capacity of the best commercial sorbent available in the market. Also, it showed good buoyancy properties on the water both as dry-mat and oil-saturated mat. In addition, it is biodegradable, easily available, easily manufactured, so the CA nanofibrous mat is an excellent candidate as oil sorbent for oil spill in water treatment.

  1. Carbon and Oxygen Budgets of Hypersaline Cyanobacterial Mats: Effects of Tidal Cycle and Temperature

    NASA Technical Reports Server (NTRS)

    DesMarais, David J.; Bebout, Brad M.; Carpenter, Steven; Discipulo, Mykell; Turk, Kendra

    2003-01-01

    The hierarchical organization of microbial ecosystems determines the rates of processes that shape Earth#s environment, define the stage upon which major evolutionary events occurred, and create biosignatures in sediments and atmospheres. In cyanobacterial mats, oxygenic photosynthesis provides energy, organic substrates and oxygen to the ecosystem. Incident light changes with depth in the mat, both in intensity and spectral composition, and counteracting gradients of oxygen and sulfide shape the chemical microenvironment. A combination of benefits and hazards of light, oxygen and sulfide promotes the allocation of the various essential mat processes between light and dark periods and to various depths in the mat. Microbiota produce hydrogen, small organic acids, and nitrogen and sulfur species. Such compounds fuel a flow of energy and electrons in these ecosystems and thus shape interactions between groups of microorganisms. Coordinated observations of population distribution, abundance, and activity for an entire community are making fundamental questions in ecology accessible. These questions address those factors that sustain the remarkable diversity of microorganisms that are now being revealed by molecular techniques. These questions also target the processes that shape the various kinds of biosignatures that we will seek, both in ancient rocks from Earth and Mars, and in atmospheres of distant planets beyond our Solar System.

  2. Proliferation of Purple Sulphur Bacteria at the Sediment Surface Affects Intertidal Mat Diversity and Functionality

    PubMed Central

    Hubas, Cédric; Jesus, Bruno; Ruivo, Mickael; Meziane, Tarik; Thiney, Najet; Davoult, Dominique; Spilmont, Nicolas; Paterson, David M.; Jeanthon, Christian

    2013-01-01

    There is a relative absence of studies dealing with mats of purple sulphur bacteria in the intertidal zone. These bacteria display an array of metabolic pathways that allow them to disperse and develop under a wide variety of conditions, making these mats important in terms of ecosystem processes and functions. Mass blooms of purple sulphur bacteria develop during summer on sediments in the intertidal zone especially on macroalgal deposits. The microbial composition of different types of mats differentially affected by the development of purple sulphur bacteria was examined, at low tide, using a set of biochemical markers (fatty acids, pigments) and composition was assessed against their influence on ecosystem functions (sediment cohesiveness, CO2 fixation). We demonstrated that proliferation of purple sulphur bacteria has a major impact on intertidal mats diversity and functions. Indeed, assemblages dominated by purple sulphur bacteria (Chromatiaceae) were efficient exopolymer producers and their biostabilisation potential was significant. In addition, the massive growth of purple sulphur bacteria resulted in a net CO2 degassing whereas diatom dominated biofilms represented a net CO2 sink. PMID:24340018

  3. Modeling dynamics of tundra plant communities on the Yamal Peninsula, Russia

    NASA Astrophysics Data System (ADS)

    Yu, Q.; Epstein, H. E.; Walker, D. A.

    2010-12-01

    Multiple environmental drivers, including climate, soil conditions and herbivory, affect arctic tundra vegetation dynamics. These factors may have been evaluated individually in the past; however, their interactions contribute to more complicated tundra plant community dynamics and may represent a substantial source of uncertainty in predicting tundra ecosystem properties in the changing Arctic. This study investigates the effects of soils, grazing, and climate change on tundra plant communities at the plant functional type (PFT) level, based on previous integrated modeling research at the ecosystem level. The study area encompasses the Yamal Peninsula, northwestern Siberia, where soil and biomass data were collected along the Yamal Arctic Transect (YAT), to drive a nutrient-based tundra vegetation model (ArcVeg) and to validate the simulation results. We analyzed plant functional type biomass and net primary productivity (NPP), and found that with higher temperatures (+2°C mean growing season temperature), most plant functional types responded positively with increased biomass and NPP, while grazing suppressed such responses in both high and low soil organic nitrogen (SON) sites. The magnitudes of the responses to warming depended on SON and grazing intensity. Relatively, there were greater responses of biomass and NPP in low SON sites compared to high SON sites. Moss biomass (in contrast to other plant types) declined 34% with warming in the low SON site and 28% in the high SON site in subzone E (the most southern tundra subzone). Increases in Low Arctic shrub biomass with warming were 61% in the high SON site in subzone E and 96% in the low SON site. Decrease in moss biomass due to warming was mitigated about 2% by high grazing frequency (maximum of 25% of biomass removal every two years) in the high SON site in subzone E, with an opposite effect in the low SON site. High grazing frequency caused greater relative increases in total shrub biomass for both low

  4. Metagenomics Reveals Pervasive Bacterial Populations and Reduced Community Diversity across the Alaska Tundra Ecosystem.

    PubMed

    Johnston, Eric R; Rodriguez-R, Luis M; Luo, Chengwei; Yuan, Mengting M; Wu, Liyou; He, Zhili; Schuur, Edward A G; Luo, Yiqi; Tiedje, James M; Zhou, Jizhong; Konstantinidis, Konstantinos T

    2016-01-01

    How soil microbial communities contrast with respect to taxonomic and functional composition within and between ecosystems remains an unresolved question that is central to predicting how global anthropogenic change will affect soil functioning and services. In particular, it remains unclear how small-scale observations of soil communities based on the typical volume sampled (1-2 g) are generalizable to ecosystem-scale responses and processes. This is especially relevant for remote, northern latitude soils, which are challenging to sample and are also thought to be more vulnerable to climate change compared to temperate soils. Here, we employed well-replicated shotgun metagenome and 16S rRNA gene amplicon sequencing to characterize community composition and metabolic potential in Alaskan tundra soils, combining our own datasets with those publically available from distant tundra and temperate grassland and agriculture habitats. We found that the abundance of many taxa and metabolic functions differed substantially between tundra soil metagenomes relative to those from temperate soils, and that a high degree of OTU-sharing exists between tundra locations. Tundra soils were an order of magnitude less complex than their temperate counterparts, allowing for near-complete coverage of microbial community richness (~92% breadth) by sequencing, and the recovery of 27 high-quality, almost complete (>80% completeness) population bins. These population bins, collectively, made up to ~10% of the metagenomic datasets, and represented diverse taxonomic groups and metabolic lifestyles tuned toward sulfur cycling, hydrogen metabolism, methanotrophy, and organic matter oxidation. Several population bins, including members of Acidobacteria, Actinobacteria, and Proteobacteria, were also present in geographically distant (~100-530 km apart) tundra habitats (full genome representation and up to 99.6% genome-derived average nucleotide identity). Collectively, our results revealed that

  5. Metagenomics Reveals Pervasive Bacterial Populations and Reduced Community Diversity across the Alaska Tundra Ecosystem

    PubMed Central

    Johnston, Eric R.; Rodriguez-R, Luis M.; Luo, Chengwei; Yuan, Mengting M.; Wu, Liyou; He, Zhili; Schuur, Edward A. G.; Luo, Yiqi; Tiedje, James M.; Zhou, Jizhong; Konstantinidis, Konstantinos T.

    2016-01-01

    How soil microbial communities contrast with respect to taxonomic and functional composition within and between ecosystems remains an unresolved question that is central to predicting how global anthropogenic change will affect soil functioning and services. In particular, it remains unclear how small-scale observations of soil communities based on the typical volume sampled (1–2 g) are generalizable to ecosystem-scale responses and processes. This is especially relevant for remote, northern latitude soils, which are challenging to sample and are also thought to be more vulnerable to climate change compared to temperate soils. Here, we employed well-replicated shotgun metagenome and 16S rRNA gene amplicon sequencing to characterize community composition and metabolic potential in Alaskan tundra soils, combining our own datasets with those publically available from distant tundra and temperate grassland and agriculture habitats. We found that the abundance of many taxa and metabolic functions differed substantially between tundra soil metagenomes relative to those from temperate soils, and that a high degree of OTU-sharing exists between tundra locations. Tundra soils were an order of magnitude less complex than their temperate counterparts, allowing for near-complete coverage of microbial community richness (~92% breadth) by sequencing, and the recovery of 27 high-quality, almost complete (>80% completeness) population bins. These population bins, collectively, made up to ~10% of the metagenomic datasets, and represented diverse taxonomic groups and metabolic lifestyles tuned toward sulfur cycling, hydrogen metabolism, methanotrophy, and organic matter oxidation. Several population bins, including members of Acidobacteria, Actinobacteria, and Proteobacteria, were also present in geographically distant (~100–530 km apart) tundra habitats (full genome representation and up to 99.6% genome-derived average nucleotide identity). Collectively, our results revealed

  6. Reduced Gas Cycling in Microbial Mats: Implications for Early Earth

    NASA Technical Reports Server (NTRS)

    Hoehler, Tori M.; Bebout, Brad M.; DesMarais, David J.; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    For more than half the history of life on Earth, biological productivity was dominated by photosynthetic microbial mats. During this time, mats served as the preeminent biological influence on earth's surface and atmospheric chemistry and also as the primary crucible for microbial evolution. We find that modern analogs of these ancient mat communities generate substantial quantities of hydrogen, carbon monoxide, and methane. Escape of these gases from the biosphere would contribute strongly to atmospheric evolution and potentially to the net oxidation of earth's surface; sequestration within the biosphere carries equally important implications for the structure, function, and evolution of anaerobic microbial communities within the context of mat biology.

  7. Organic geochemical studies of modern microbial mats from Shark Bay: Part I: Influence of depth and salinity on lipid biomarkers and their isotopic signatures.

    PubMed

    Pagès, A; Grice, K; Ertefai, T; Skrzypek, G; Jahnert, R; Greenwood, P

    2014-09-01

    The present study investigated the influence of abiotic conditions on microbial mat communities from Shark Bay, a World Heritage area well known for a diverse range of extant mats presenting structural similarities with ancient stromatolites. The distributions and stable carbon isotopic values of lipid biomarkers [aliphatic hydrocarbons and polar lipid fatty acids (PLFAs)] and bulk carbon and nitrogen isotope values of biomass were analysed in four different types of mats along a tidal flat gradient to characterize the microbial communities and systematically investigate the relationship of the above parameters with water depth. Cyanobacteria were dominant in all mats, as demonstrated by the presence of diagnostic hydrocarbons (e.g. n-C17 and n-C17:1). Several subtle but important differences in lipid composition across the littoral gradient were, however, evident. For instance, the shallower mats contained a higher diatom contribution, concordant with previous mat studies from other locations (e.g. Antarctica). Conversely, the organic matter (OM) of the deeper mats showed evidence for a higher seagrass contribution [high C/N, 13C-depleted long-chain n-alkanes]. The morphological structure of the mats may have influenced CO2 diffusion leading to more 13C-enriched lipids in the shallow mats. Alternatively, changes in CO2 fixation pathways, such as increase in the acetyl COA-pathway by sulphate-reducing bacteria, could have also caused the observed shifts in δ13C values of the mats. In addition, three smooth mats from different Shark Bay sites were analysed to investigate potential functional relationship of the microbial communities with differing salinity levels. The C25:1 HBI was identified in the high salinity mat only and a lower abundance of PLFAs associated with diatoms was observed in the less saline mats, suggesting a higher abundance of diatoms at the most saline site. Furthermore, it appeared that the most and least saline mats were dominated by

  8. Deeper winter snow reduces ecosystem C losses but increases the global warming potential of Arctic tussock tundra over the growing season.

    NASA Astrophysics Data System (ADS)

    Blanc-Betes, E.; Welker, J. M.; Gomez-Casanovas, N.; Gonzalez-Meler, M. A.

    2015-12-01

    Arctic winter precipitation is projected to increase globally over the next decades, spatial variability encompassing areas with increases and decreases in winter snow. Changes in winter precipitation strongly affect C dynamics in Arctic systems and may lead to major positive climate forcing feedbacks. However, impacts of predicted changes in snowfall and accumulation on the rate and form of C fluxes (CO2 and CH4) and associated forcing feedbacks from Arctic tundra remain uncertain. We investigated how changes in winter precipitation affect net ecosystem CO2 and CH4 fluxes and budgets of moist acidic tundra in an 18-yrs snow fence experiment over a complete growing season at Toolik Lake, AK. Arctic tundra under ambient winter precipitation (CTL) was a net source of CO2 and CH4, yielding net C losses over the growing season. Reduced snow (-15-30% snow depth; RS) switched the system to a net CO2 sink mostly by limiting SOC decomposition within colder soils. Snow additions progressively reduced net ecosystem CO2 losses compared to CTL, switching the system into a weaker net CO2 source with medium additions (+20-45% snow depth; MS) and into a small net CO2 sink with high additions (+70-100% snow depth; HS). Increasingly wetter soils with snow additions constrained the temperature sensitivity of aerobic decomposition and favored the anaerobic metabolism, buffering ecosystem CO2 losses despite substantial soil warming. Accordingly, Arctic tundra switched from a sustained CH4 sink at RS site to an increasingly stronger CH4 source with snow additions. Accounting for both CO2 and CH4, the RS site became a net C sink over the growing season, overall reducing the global warming potential (CO2 equiv.; GWP) of the system relative to CTL. Snow additions progressively reduced net C losses at the MS site compared to CTL and the system transitioned into a net C sink at HS plots, partly due to the slower metabolism of anaerobic decomposition. However, given the greater radiative

  9. Specific features of the genesis of automorphic soils of the northern forest-tundra (southeast of the Bol'shezemel'skaya tundra)

    NASA Astrophysics Data System (ADS)

    Rusanova, G. V.; Deneva, S. V.; Shakhtarova, O. V.

    2015-02-01

    Automorphic soils developed from sandy materials (podzolized podburs, (Entic Podzols) and iron-illuvial podzols (Haplic Podzols)) and loamy materials (organic cryometamorphic soils (Gelic Cambisols) and iron-illuvial svetlozems (Spodi-Stagnic Cambisols)) were studied in the northern forest-tundra zone. Podzolized podburs and podzols of tundra cenoses were less podzolized in comparison with the analogous soils developed under forest cenoses. This can be explained by a higher intensity of cryogenic processes favoring the fixation of iron-humus films on skeletal grains in the sandy soils of tundra cenoses. In the organic cryometamorphic soils, the illuviation of Al-Fe-humus compounds with the formation of bleached skeletans in the upper part of the mineral horizon was identified. The eluvial-illuvial differentiation of the soil mass diagnosed by the analyses of intraped mass was weakly pronounced. The features attributed to the activity of cryogenic processes were also described in these soils. Iron-illuvial svetlozems were characterized by the migration of iron compounds within the microprofile of podzol in the topsoil and by the specific well-structured cryometamorphic horizons in the lower part of the profile. The features inherited from the previous stages of soil development were identified in these soils.

  10. Estimating carbon and energy fluxes in arctic tundra

    NASA Astrophysics Data System (ADS)

    Gokkaya, K.; Jiang, Y.; Rastetter, E.; Shaver, G. R.; Rocha, A. V.

    2013-12-01

    Arctic ecosystems are undergoing a very rapid change due to climate change and their response to climate change has important implications for the global energy budget and carbon (C) cycling. Therefore, it is important to understand how (C) and energy fluxes in the Arctic will respond to climate change. However, attribution of these responses to climate is challenging because measured fluxes are the sum of multiple processes that respond differently to environmental factors. For example, net ecosystem exchange of CO2 (NEE) is the net result of gross (C) uptake by plant photosynthesis (GPP) and (C) loss by ecosystem respiration (ER) and similarly, evapotranspiration (i.e. latent energy, LE) is the sum of transpiration and evaporation. Partitioning of NEE into GPP and ER requires nighttime measurements of NEE, when photosynthesis does not take place, to be extrapolated to daytime. This is challenging in the Arctic because of the long photoperiod during the growing season and the errors involved during the extrapolation. Transpiration (energy), photosynthesis (carbon), and vegetation phenology are inherently coupled because leaf stomata are the primary regulators of gas exchange. Our objectives in this study are to i) estimate canopy resistance (Rc) based on a light use efficiency model, ii) utilize the estimated Rc to predict GPP and transpiration using a coupled C and energy model and thus improve the partitioning of NEE and LE, and iii) to test ensemble Kalman filter (EnKF) to estimate model parameters and improve model predictions. Results from one growing season showed that the model predictions can explain 75 and 71% of the variance in GPP and LE in the Arctic tundra ecosystem, respectively. When the model was embedded within the EnKF for estimating Rc, the amount of variance explained for GPP increased to 81% but there was no improvement for the prediction of LE. This suggests that the factors controlling LE are not fully integrated in the model such as the

  11. Stromatolites, Metals, Statistics and Microbial Mats: A Complex Interplay

    NASA Astrophysics Data System (ADS)

    Spear, J. R.

    2014-12-01

    Initially thought to be relatively 'simple' ecosystems for study, microbial mats have long been considered ideal for any number of research questions. Microbial mats can be found in any number of environments, both natural and manmade, and are typically dependent upon the physiochemical environment for their structure, maintenance and longevity. Ultimately, these and other parameters govern community whereby a microbial mat provides overall ecosystem services to their environment. On the edge of a hotspring in Yellowstone National Park we have found an active microbial mat community that can form a laminated, lithified, accretionary structure that is likely the best example of a living and growing stromatolite. In the outfall channel of the sulfidic Stinking Spring, Utah, we have found examples of both naturally occurring laminated and floating mats where the carbon flux is controlled by abiotic degassing of CO2 rather than metabolism. δ13C-bicarbonate uptake experiments reveal an autotrophic growth rate of 0 - 0.16%/day while δ13C-acetate reveals a higher heterotrophic growth rate of 0.03 - 0.65%/day, which highlights the role of heterotrophs in these mats. Similar growth experiments on Little Hot Creek, California laminated microbial mats reveal a trend for top-down microbial growth with similar microbial taxonomy and diversity to other mat-types. Of a curious note is that incubation experiments with Little Hot Creek mats reveals the importance of particular metals in mat structure and function. Statistically, alpha- and beta-diversity metrics are often used to characterize microbial communities in such systems, but from an analysis of a wastewater treatment system, Hill diversities can better interpret the effective number of species to produce an ecologically intuitive quantity to better understand a microbial mat ecosystem.

  12. The footprint of Alaskan tundra fires during the past half-century: implications for surface properties and radiative forcing

    USGS Publications Warehouse

    Rocha, Adrian V.; Loranty, Michael M.; Higuera, Phil E.; Mack, Michelle C.; Hu, Feng Sheng; Jones, Benjamin M.; Breen, Amy L.; Rastetter, Edward B.; Goetz, Scott J.; Shaver, Gus R.

    2012-01-01

    Recent large and frequent fires above the Alaskan arctic circle have forced a reassessment of the ecological and climatological importance of fire in arctic tundra ecosystems. Here we provide a general overview of the occurrence, distribution, and ecological and climate implications of Alaskan tundra fires over the past half-century using spatially explicit climate, fire, vegetation and remote sensing datasets for Alaska. Our analyses highlight the importance of vegetation biomass and environmental conditions in regulating tundra burning, and demonstrate that most tundra ecosystems are susceptible to burn, providing the environmental conditions are right. Over the past two decades, fire perimeters above the arctic circle have increased in size and importance, especially on the North Slope, indicating that future wildfire projections should account for fire regime changes in these regions. Remote sensing data and a literature review of thaw depths indicate that tundra fires have both positive and negative implications for climatic feedbacks including a decadal increase in albedo radiative forcing immediately after a fire, a stimulation of surface greenness and a persistent long-term (>10 year) increase in thaw depth. In order to address the future impact of tundra fires on climate, a better understanding of the control of tundra fire occurrence as well as the long-term impacts on ecosystem carbon cycling will be required.

  13. Winter and early spring CO2 efflux from tundra communities of northern Alaska

    NASA Astrophysics Data System (ADS)

    Fahnestock, J. T.; Jones, M. H.; Brooks, P. D.; Walker, D. A.; Welker, J. M.

    1998-11-01

    Carbon dioxide concentrations through snow were measured in different arctic tundra communities on the North Slope of Alaska during winter and early spring of 1996. Subnivean CO2 concentrations were always higher than atmospheric CO2. A steady state diffusion model was used to generate conservative estimates of CO2 flux to the atmosphere. The magnitude of CO2 efflux differed with tundra community type, and rates of carbon release increased from March to May. Winter CO2 efflux was highest in riparian and snow bed communities and lowest in dry heath, upland tussock, and wet sedge communities. Snow generally accrues earlier in winter and is deeper in riparian and snow bed communities compared with other tundra communities, which are typically windswept and do not accumulate much snow during the winter. These results support the hypothesis that early and deep snow accumulation may insulate microbial populations from very cold temperatures, allowing sites with earlier snow cover to sustain higher levels of activity throughout winter compared to communities that have later developing snow cover. Extrapolating our estimates of CO2 efflux to the entire snow-covered season indicates that total carbon flux during winter in the Arctic is 13-109 kg CO2-C ha-1, depending on the vegetation community type. Wintertime CO2 flux is a potentially important, yet largely overlooked, part of the annual carbon cycle of tundra, and carbon release during winter should be accounted for in estimates of annual carbon balance in arctic ecosystems.

  14. Nutrients and biomass spatial patterns in alpine tundra ecosystem on Changbai Mountains, Northeast China.

    PubMed

    Wu, Gang; Jiang, Ping; Wei, Jing; Shao, Hongbo

    2007-11-15

    Biomass and nutrients were investigated in 2003, 2004 and 2005 growing seasons by using a chronosequence of five vegetation types in alpine tundra on Changbai Mountains. The objective of this study was to test whether nutrients at biointerfaces were significant differences among five vegetation types. The biomass and elevation are highly related (biomass=-237.3ln(elevation)+494.36; R(2)=0.8092; p<0.05). There were no significant differences in phosphorus (P) and sulphur (S) concentrations of roots, stems and leaves among five vegetation types while there are significant differences in nitrogen (N) and P stocks of roots, stems and leaves and in S stock of stems and leaves among typical alpine tundra vegetation (TA), meadow alpine tundra vegetation (MA), and swamp alpine tundra vegetation (SA) (p<0.05). Vegetation nutrients stock is averagely 72.46kg hm(-2), and N, P, S stocks are 48.55, 10.33 and 13.61kg hm(-2), respectively. Soil N and S concentrations in MA are significantly higher than those in other four soil types. P is higher in SA (p<0.05). Soil nutrients stock (0-20cm) is averagely 39.59t hm(-2), and N, P, S stocks are 23.74, 5.86 and 9.99t hm(-2), respectively. PMID:17659864

  15. CLIMATIC EFFECTS ON TUNDRA CARBON STORAGE INFERRED FROM EXPERIMENTAL DATA AND A MODEL

    EPA Science Inventory

    We used a process-based model of ecosystem carbon (C) and nitrogen (N)dynamics, MBL-GEM (Marine Biological Laboratory General Ecosystem Model), to integrated and analyze the results of several experiments that examined the response of arctic tussock tundra to manipulations of CO2...

  16. Global assessment of experimental climate warming on tundra vegetation: heterogeneity over space and time.

    PubMed

    Elmendorf, Sarah C; Henry, Gregory H R; Hollister, Robert D; Björk, Robert G; Bjorkman, Anne D; Callaghan, Terry V; Collier, Laura Siegwart; Cooper, Elisabeth J; Cornelissen, Johannes H C; Day, Thomas A; Fosaa, Anna Maria; Gould, William A; Grétarsdóttir, Járngerður; Harte, John; Hermanutz, Luise; Hik, David S; Hofgaard, Annika; Jarrad, Frith; Jónsdóttir, Ingibjörg Svala; Keuper, Frida; Klanderud, Kari; Klein, Julia A; Koh, Saewan; Kudo, Gaku; Lang, Simone I; Loewen, Val; May, Jeremy L; Mercado, Joel; Michelsen, Anders; Molau, Ulf; Myers-Smith, Isla H; Oberbauer, Steven F; Pieper, Sara; Post, Eric; Rixen, Christian; Robinson, Clare H; Schmidt, Niels Martin; Shaver, Gaius R; Stenström, Anna; Tolvanen, Anne; Totland, Orjan; Troxler, Tiffany; Wahren, Carl-Henrik; Webber, Patrick J; Welker, Jeffery M; Wookey, Philip A

    2012-02-01

    Understanding the sensitivity of tundra vegetation to climate warming is critical to forecasting future biodiversity and vegetation feedbacks to climate. In situ warming experiments accelerate climate change on a small scale to forecast responses of local plant communities. Limitations of this approach include the apparent site-specificity of results and uncertainty about the power of short-term studies to anticipate longer term change. We address these issues with a synthesis of 61 experimental warming studies, of up to 20 years duration, in tundra sites worldwide. The response of plant groups to warming often differed with ambient summer temperature, soil moisture and experimental duration. Shrubs increased with warming only where ambient temperature was high, whereas graminoids increased primarily in the coldest study sites. Linear increases in effect size over time were frequently observed. There was little indication of saturating or accelerating effects, as would be predicted if negative or positive vegetation feedbacks were common. These results indicate that tundra vegetation exhibits strong regional variation in response to warming, and that in vulnerable regions, cumulative effects of long-term warming on tundra vegetation - and associated ecosystem consequences - have the potential to be much greater than we have observed to date. PMID:22136670

  17. Importance of Marine-Derived Nutrients Supplied by Planktivorous Seabirds to High Arctic Tundra Plant Communities

    PubMed Central

    Zwolicki, Adrian; Zmudczyńska-Skarbek, Katarzyna; Richard, Pierre; Stempniewicz, Lech

    2016-01-01

    We studied the relative importance of several environmental factors for tundra plant communities in five locations across Svalbard (High Arctic) that differed in geographical location, oceanographic and climatic influence, and soil characteristics. The amount of marine-derived nitrogen in the soil supplied by seabirds was locally the most important of the studied environmental factors influencing the tundra plant community. We found a strong positive correlation between δ15N isotopic values and total N content in the soil, confirming the fundamental role of marine-derived matter to the generally nutrient-poor Arctic tundra ecosystem. We also recorded a strong correlation between the δ15N values of soil and of the tissues of vascular plants and mosses, but not of lichens. The relationship between soil δ15N values and vascular plant cover was linear. In the case of mosses, the percentage ground cover reached maximum around a soil δ 15N value of 8‰, as did plant community diversity. This soil δ15N value clearly separated the occurrence of plants with low nitrogen tolerance (e.g. Salix polaris) from those predominating on high N content soils (e.g. Cerastium arcticum, Poa alpina). Large colonies of planktivorous little auks have a great influence on Arctic tundra vegetation, either through enhancing plant abundance or in shaping plant community composition at a local scale. PMID:27149113

  18. Determining Regional Arctic Tundra Carbon Exchange: A Bottom-Up Approach

    NASA Technical Reports Server (NTRS)

    Huemmrich, Fred

    2006-01-01

    This viewgraph presentation reviews the carbon atmospheric exchange with Arctic tundra. In the Arctic the ecosystem has been a net carbon sink. The project investigates the question of how might climate warming effect high latitude ecosystems and the Earth ecosystems and how to measure the changes.

  19. Assessing the Tundra-taiga Boundary with Multi-Sensor Satellite Data

    NASA Technical Reports Server (NTRS)

    Ranson, K. J.; Sun, G.; Kharuk, V. I.; Kovacs, K.

    2004-01-01

    Monitoring the dynamics of the circumpolar boreal forest (taiga) and Arctic tundra boundary is important for understanding the causes and consequences of changes observed in these areas. This ecotone, the world's largest, stretches for over 13,400 km and marks the transition between the northern limits of forests and the southern margin of the tundra. Because of the inaccessibility and large extent of this zone, remote sensing data can play an important role for mapping the characteristics and monitoring the dynamics. Basic understanding of the capabilities of existing space borne instruments for these purposes is required. In this study we examined the use of several remote sensing techniques for identifying the existing tundra- taiga ecotone. These include Landsat-7, MISR, MODIS and RADARSAT data. Historical cover maps, recent forest stand measurements and high-resolution IKONOS images were used for local ground truth. It was found that a tundra-taiga transitional area can be characterized using multi- spectral Landsat ETM+ summer images, multi-angle MISR red band reflectance images, RADARSAT images with larger incidence angle, or multi-temporal and multi-spectral MODIS data. Because of different resolutions and spectral regions covered, the transition zone maps derived from different data types were not identical, but the general patterns were consistent.

  20. Importance of Marine-Derived Nutrients Supplied by Planktivorous Seabirds to High Arctic Tundra Plant Communities.

    PubMed

    Zwolicki, Adrian; Zmudczyńska-Skarbek, Katarzyna; Richard, Pierre; Stempniewicz, Lech

    2016-01-01

    We studied the relative importance of several environmental factors for tundra plant communities in five locations across Svalbard (High Arctic) that differed in geographical location, oceanographic and climatic influence, and soil characteristics. The amount of marine-derived nitrogen in the soil supplied by seabirds was locally the most important of the studied environmental factors influencing the tundra plant community. We found a strong positive correlation between δ15N isotopic values and total N content in the soil, confirming the fundamental role of marine-derived matter to the generally nutrient-poor Arctic tundra ecosystem. We also recorded a strong correlation between the δ15N values of soil and of the tissues of vascular plants and mosses, but not of lichens. The relationship between soil δ15N values and vascular plant cover was linear. In the case of mosses, the percentage ground cover reached maximum around a soil δ 15N value of 8‰, as did plant community diversity. This soil δ15N value clearly separated the occurrence of plants with low nitrogen tolerance (e.g. Salix polaris) from those predominating on high N content soils (e.g. Cerastium arcticum, Poa alpina). Large colonies of planktivorous little auks have a great influence on Arctic tundra vegetation, either through enhancing plant abundance or in shaping plant community composition at a local scale. PMID:27149113

  1. Isotopic identification of soil and permafrost nitrate sources in an Arctic tundra ecosystem

    SciTech Connect

    Heikoop, Jeffrey M.; Throckmorton, Heather M.; Newman, Brent D.; Perkins, George B.; Iversen, Colleen M.; Chowdhury, Taniya Roy; Romanovsky, Vladimir; Graham, David E.; Norby, Richard J.; Wilson, Cathy J.; Wullschleger, Stan D.

    2015-05-13

    The nitrate (NO3) dual isotope approach was applied to snowmelt, tundra active layer pore waters, and underlying permafrost in Barrow, Alaska, USA, to distinguish between NO3 derived from atmospheric deposition versus that derived from microbial nitrification.

  2. Alpine forest-tundra ecotone response to temperature change,Sayan Mountains, Siberia

    NASA Technical Reports Server (NTRS)

    Ranson, K Jon; Kharuk, Vyetcheslav I.

    2007-01-01

    Models of climate change predict shifts of vegetation zones. Tree response to climate trends is most likely observable in the forest-tundra ecotone, where temperature mainly limits tree growth. There is evidence of vegetation change on the northern treeline However, observations on alpine tree line response are controversial. In this NEESPI related study we show that during the past three decades in the forest-tundra ecotone of the Sayan Mountains, Siberia, there was an increase in forest stand crown closure, regeneration propagation into the alpine tundra, and transformation of prostrate Siberian pine and fir into arboreal forms. We found that these changes occurred since the mid 1980s, and strongly correlates with positive temperature (and to a lesser extent, precipitation) trends. Improving climate for forest growth( i.e., warmer temperatures and increased precipitation) provides competitive advantages to Siberian pine in the alpine forest-tundra ecotone, as well as in areas typically dominated by larch, where it has been found to be forming a secondary canopy layer. Substitution of deciduous conifer, larch, for evergreen conifers, decreases albedo and provides positive feedback for temperature increase.

  3. Contrasting soil thermal responses to fire in Alaskan tundra and boreal forest

    NASA Astrophysics Data System (ADS)

    Jiang, Yueyang; Rocha, Adrian V.; O'Donnell, Jonathan A.; Drysdale, Jessica A.; Rastetter, Edward B.; Shaver, Gaius R.; Zhuang, Qianlai

    2015-02-01

    Recent fire activity throughout Alaska has increased the need to understand postfire impacts on soils and permafrost vulnerability. Our study utilized data and modeling from a permafrost and ecosystem gradient to develop a mechanistic understanding of the short- and long-term impacts of tundra and boreal forest fires on soil thermal dynamics. Fires influenced a variety of factors that altered the surface energy budget, soil moisture, and the organic-layer thickness with the overall effect of increasing soil temperatures and thaw depth. The postfire thickness of the soil organic layer and its impact on soil thermal conductivity was the most important factor determining postfire soil temperatures and thaw depth. Boreal and tundra ecosystems underlain by permafrost experienced smaller postfire soil temperature increases than the nonpermafrost boreal forest from the direct and indirect effects of permafrost on drainage, soil moisture, and vegetation flammability. Permafrost decreased the loss of the insulating soil organic layer, decreased soil drying, increased surface water pooling, and created a significant heat sink to buffer postfire soil temperature and thaw depth changes. Ecosystem factors also played a role in determining postfire thaw depth with boreal forests taking several decades longer to recover their soil thermal properties than tundra. These factors resulted in tundra being less sensitive to postfire soil thermal changes than the nonpermafrost boreal forest. These results suggest that permafrost and soil organic carbon will be more vulnerable to fire as climate warms.

  4. Micrometeorological measurements of CH4 and CO2 exchange between the atmosphere and subarctic tundra

    NASA Technical Reports Server (NTRS)

    Fan, S. M.; Wofsy, S. C.; Bakwin, P. S.; Jacob, D. J.; Anderson, S. M.; Kebabian, P. L.; Mcmanus, J. B.; Kolb, C. E.; Fitzjarrald, D. R.

    1992-01-01

    Eddy correlation flux measurements and concentration profiles of total hydrocarbons (THC) and CO2 were combined to provide a comprehensive record of atmosphere-biosphere exchange for these gases over a 30-day period in July-August 1988 in the Yukon-Kuskokwin River Delta of Alaska. Over 90 percent of net ecosystem exchanges of THC were due to methane. Lakes and wet meadow tundra provided the major sources of methane. The average fluxes from lake, dry tundra, and wet tundra were 11 +/- 3, 29 +/- 3, and 57 +/- 6 mg CH4/sq m/d, respectively. The mean remission rate for the site was 25 mg/sq m/d. Maximum uptake of CO2 by the tundra was 1.4 gC/sq m/d between 1000 and 1500 hrs, and nocturnal respiration averaged 0.73 gC/sq m/d. Net uptake of CO2 was 0.30 gC/sq m/d for the 30 days of measurement; methane flux accounted for 6 percent of CO2 net uptake.

  5. Identification of a novel cyanobacterial group as active diazotrophs in a coastal microbial mat using NanoSIMS analysis

    PubMed Central

    Woebken, Dagmar; Burow, Luke C; Prufert-Bebout, Leslie; Bebout, Brad M; Hoehler, Tori M; Pett-Ridge, Jennifer; Spormann, Alfred M; Weber, Peter K; Singer, Steven W

    2012-01-01

    N2 fixation is a key process in photosynthetic microbial mats to support the nitrogen demands associated with primary production. Despite its importance, groups that actively fix N2 and contribute to the input of organic N in these ecosystems still remain largely unclear. To investigate the active diazotrophic community in microbial mats from the Elkhorn Slough estuary, Monterey Bay, CA, USA, we conducted an extensive combined approach, including biogeochemical, molecular and high-resolution secondary ion mass spectrometry (NanoSIMS) analyses. Detailed analysis of dinitrogenase reductase (nifH) transcript clone libraries from mat samples that fixed N2 at night indicated that cyanobacterial nifH transcripts were abundant and formed a novel monophyletic lineage. Independent NanoSIMS analysis of 15N2-incubated samples revealed significant incorporation of 15N into small, non-heterocystous cyanobacterial filaments. Mat-derived enrichment cultures yielded a unicyanobacterial culture with similar filaments (named Elkhorn Slough Filamentous Cyanobacterium-1 (ESFC-1)) that contained nifH gene sequences grouping with the novel cyanobacterial lineage identified in the transcript clone libraries, displaying up to 100% amino-acid sequence identity. The 16S rRNA gene sequence recovered from this enrichment allowed for the identification of related sequences from Elkhorn Slough mats and revealed great sequence diversity in this cluster. Furthermore, by combining 15N2 tracer experiments, fluorescence in situ hybridization and NanoSIMS, in situ N2 fixation activity by the novel ESFC-1 group was demonstrated, suggesting that this group may be the most active cyanobacterial diazotroph in the Elkhorn Slough mat. Pyrotag sequences affiliated with ESFC-1 were recovered from mat samples throughout 2009, demonstrating the prevalence of this group. This work illustrates that combining standard and single-cell analyses can link phylogeny and function to identify previously unknown key

  6. Magnetoacoustic tomography with magnetic induction (MAT-MI).

    PubMed

    Xu, Yuan; He, Bin

    2005-11-01

    We report our theoretical and experimental investigations on a new imaging modality, magnetoacoustic tomography with magnetic induction (MAT-MI). In MAT-MI, the sample is located in a static magnetic field and a time-varying (micros) magnetic field. The time-varying magnetic field induces an eddy current in the sample. Consequently, the sample will emit ultrasonic waves by the Lorentz force. The ultrasonic signals are collected around the object to reconstruct images related to the electrical impedance distribution in the sample. MAT-MI combines the good contrast of electrical impedance tomography with the good spatial resolution of sonography. MAT-MI has two unique features due to the solenoid nature of the induced electrical field. Firstly, MAT-MI could provide an explicit or simple quantitative reconstruction algorithm for the electrical impedance distribution. Secondly, it promises to eliminate the shielding effects of other imaging modalities in which the current is applied directly with electrodes. In the theoretical part, we provide formulae for both the forward and inverse problems of MAT-MI and estimate the signal amplitude in biological tissues. In the experimental part, the experimental setup and methods are introduced and the signals and the image of a metal object by means of MAT-MI are presented. The promising pilot experimental results suggest the feasibility of the proposed MAT-MI approach. PMID:16237248

  7. Compositions and method of use of constructed microbial mats

    DOEpatents

    Bender, Judith A.; Phillips, Peter C.

    1997-01-01

    Compositions and methods of use of constructed microbial mats, comprising cyanobacteria and purple autotrophic bacteria and an organic nutrient source, in a laminated structure, are described. The constructed microbial mat is used for bioremediation of different individual contaminants and for mixed or multiple contaminants, and for production of beneficial compositions and molecules.

  8. Pilot Bill Dana in HiMAT cockpit

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The HiMAT (Highly Maneuverable Aircraft Technology) simulator was used from 1978 to 1983. The HiMAT was a remotely piloted research vehicle built to develop high-performance fighter technology that included advanced structures, and integrated controls and propulsion systems. The simulator was used in support of the flight program.

  9. Magnetoacoustic Tomography with Magnetic Induction (MAT-MI)

    PubMed Central

    Xu, Yuan; He, Bin

    2007-01-01

    We report our theoretical and experimental investigations on a new imaging modality, magnetoacoustic tomography with magnetic induction (MAT-MI). In MAT-MI, the sample is located in a static magnetic field and a time-varying (μs ) magnetic field. The time-varying magnetic field induces eddy current in the sample. Consequently, the sample will emit ultrasonic waves by the Lorentz force. The ultrasonic signals are collected around the object to reconstruct images related with the electrical impedance distribution in the sample. MAT-MI combines the good contrast of electrical impedance tomography with the good spatial resolution of sonography. In principle, MAT-MI mainly has two unique features due to the solenoid nature of the induced electrical field. Firstly, MAT-MI could provide explicit or simple quantitative reconstruction algorithm for the electrical impedance distribution. Secondly, it promises to eliminate the shielding effects of other imaging modalities in which the current is applied directly with electrodes. In the theoretical part, we provide the formulas for both the forward and inverse problems of MAT-MI and estimate the signal amplitude in biological tissues. In the experimental part, the experiment setup and methods are introduced and the signals and the image of a metal object by means of MAT-MI are presented. The promising pilot experimental results suggest the feasibility of the proposed MAT-MI approach. PMID:16237248

  10. MAT@USC Candidates and Latino English Language Learners

    ERIC Educational Resources Information Center

    Lomeli, Cynthia Leticia

    2012-01-01

    The purpose of this study was to further understand the perceptions of MAT@USC teacher candidates and how their perceptions and previous experiences affect the educational experiences of Latino English language learners. Three questions were developed to guide this study: (1) What are the perceptions of MAT@USC candidates in selected courses…

  11. DEMONSTRATION OF INPUFF WITH THE MATS DATA BASE

    EPA Science Inventory

    An integrated puff model, INPUFF, is evaluated using the MATS data base. A description of the model is provided outlining the salient characteristics. A brief description of the MATS data base, which consists of 14 SF6 tracer releases with associated meteorology, is also provided...

  12. Quantitative PCR Analysis of Functional Genes in Iron-Rich Microbial Mats at an Active Hydrothermal Vent System (Lō'ihi Seamount, Hawai'i)

    PubMed Central

    Jesser, Kelsey J.; Fullerton, Heather; Hager, Kevin W.

    2015-01-01

    The chemolithotrophic Zetaproteobacteria represent a novel class of Proteobacteria which oxidize Fe(II) to Fe(III) and are the dominant bacterial population in iron-rich microbial mats. Zetaproteobacteria were first discovered at Lō'ihi Seamount, located 35 km southeast off the big island of Hawai'i, which is characterized by low-temperature diffuse hydrothermal venting. Novel nondegenerate quantitative PCR (qPCR) assays for genes associated with microbial nitrogen fixation, denitrification, arsenic detoxification, Calvin-Benson-Bassham (CBB), and reductive tricarboxylic acid (rTCA) cycles were developed using selected microbial mat community-derived metagenomes. Nitrogen fixation genes were not detected, but all other functional genes were present. This suggests that arsenic detoxification and denitrification processes are likely cooccurring in addition to two modes of carbon fixation. Two groups of microbial mat community types were identified by terminal restriction fragment length polymorphism (T-RFLP) and were further described based on qPCR data for zetaproteobacterial abundance and carbon fixation mode preference. qPCR variance was associated with mat morphology but not with temperature or sample site. Geochemistry data were significantly associated with sample site and mat morphology. Together, these qPCR assays constitute a functional gene signature for iron microbial mat communities across a broad array of temperatures, mat types, chemistries, and sampling sites at Lō'ihi Seamount. PMID:25681182

  13. Quantitative PCR analysis of functional genes in iron-rich microbial mats at an active hydrothermal vent system (Lō'ihi Seamount, Hawai'i).

    PubMed

    Jesser, Kelsey J; Fullerton, Heather; Hager, Kevin W; Moyer, Craig L

    2015-05-01

    The chemolithotrophic Zetaproteobacteria represent a novel class of Proteobacteria which oxidize Fe(II) to Fe(III) and are the dominant bacterial population in iron-rich microbial mats. Zetaproteobacteria were first discovered at Lō'ihi Seamount, located 35 km southeast off the big island of Hawai'i, which is characterized by low-temperature diffuse hydrothermal venting. Novel nondegenerate quantitative PCR (qPCR) assays for genes associated with microbial nitrogen fixation, denitrification, arsenic detoxification, Calvin-Benson-Bassham (CBB), and reductive tricarboxylic acid (rTCA) cycles were developed using selected microbial mat community-derived metagenomes. Nitrogen fixation genes were not detected, but all other functional genes were present. This suggests that arsenic detoxification and denitrification processes are likely cooccurring in addition to two modes of carbon fixation. Two groups of microbial mat community types were identified by terminal restriction fragment length polymorphism (T-RFLP) and were further described based on qPCR data for zetaproteobacterial abundance and carbon fixation mode preference. qPCR variance was associated with mat morphology but not with temperature or sample site. Geochemistry data were significantly associated with sample site and mat morphology. Together, these qPCR assays constitute a functional gene signature for iron microbial mat communities across a broad array of temperatures, mat types, chemistries, and sampling sites at Lō'ihi Seamount. PMID:25681182

  14. Greater shrub dominance alters breeding habitat and food resources for migratory songbirds in Alaskan arctic tundra.

    PubMed

    Boelman, Natalie T; Gough, Laura; Wingfield, John; Goetz, Scott; Asmus, Ashley; Chmura, Helen E; Krause, Jesse S; Perez, Jonathan H; Sweet, Shannan K; Guay, Kevin C

    2015-04-01

    Climate warming is affecting the Arctic in multiple ways, including via increased dominance of deciduous shrubs. Although many studies have focused on how this vegetation shift is altering nutrient cycling and energy balance, few have explicitly considered effects on tundra fauna, such as the millions of migratory songbirds that breed in northern regions every year. To understand how increasing deciduous shrub dominance may alter breeding songbird habitat, we quantified vegetation and arthropod community characteristics in both graminoid and shrub dominated tundra. We combined measurements of preferred nest site characteristics for Lapland longspurs (Calcarius lapponicus) and Gambel's White-crowned sparrows (Zonotrichia leucophrys gambelii) with modeled predictions for the distribution of plant community types in the Alaskan arctic foothills region for the year 2050. Lapland longspur nests were found in sedge-dominated tussock tundra where shrub height does not exceed 20 cm, whereas White-crowned sparrows nested only under shrubs between 20 cm and 1 m in height, with no preference for shrub species. Shrub canopies had higher canopy-dwelling arthropod availability (i.e. small flies and spiders) but lower ground-dwelling arthropod availability (i.e. large spiders and beetles). Since flies are the birds' preferred prey, increasing shrubs may result in a net enhancement in preferred prey availability. Acknowledging the coarse resolution of existing tundra vegetation models, we predict that by 2050 there will be a northward shift in current White-crowned sparrow habitat range and a 20-60% increase in their preferred habitat extent, while Lapland longspur habitat extent will be equivalently reduced. Our findings can be used to make first approximations of future habitat change for species with similar nesting requirements. However, we contend that as exemplified by this study's findings, existing tundra modeling tools cannot yet simulate the fine-scale habitat

  15. Critical review of mercury fates and contamination in the Arctic tundra ecosystem.

    PubMed

    Poissant, Laurier; Zhang, Hong H; Canário, João; Constant, Philippe

    2008-08-01

    Mercury (Hg) contamination in tundra region has raised substantial concerns, especially since the first report of atmospheric mercury depletion events (AMDEs) in the Polar Regions. During the past decade, steady progress has been made in the research of Hg cycling in the Polar Regions. This has generated a unique opportunity to survey the whole Arctic in respect to Hg issue and to find out new discoveries. However, there are still considerable knowledge gaps and debates on the fate of Hg in the Arctic and Antarctica, especially regarding the importance and significance of AMDEs vs. net Hg loadings and other processes that burden Hg in the Arctic. Some studies argued that climate warming since the last century has exerted profound effects on the limnology of High Arctic lakes, including substantial increases in autochthonous primary productivity which increased in sedimentary Hg, whereas some others pointed out the importance of the formation and postdeposition crystallographic history of the snow and ice crystals in determining the fate and concentration of mercury in the cryosphere in addition to AMDEs. Is mercury re-emitted back to the atmosphere after AMDEs? Is Hg methylation effective in the Arctic tundra? Where the sources of MeHg are? What is its fate? Is this stimulated by human made? This paper presents a critical review about the fate of Hg in the Arctic tundra, such as pathways and process of Hg delivery into the Arctic ecosystem; Hg concentrations in freshwater and marine ecosystems; Hg concentrations in terrestrial biota; trophic transfer of Hg and bioaccumulation of Hg through food chain. This critical review of mercury fates and contamination in the Arctic tundra ecosystem is assessing the impacts and potential risks of Hg contamination on the health of Arctic people and the global northern environment by highlighting and "perspectiving" the various mercury processes and concentrations found in the Arctic tundra. PMID:18707754

  16. Surface energy exchanges along a tundra-forest transition and feedbacks to climate

    USGS Publications Warehouse

    Beringer, J.; Chapin, F. S., III; Thompson, Catharine Copass; McGuire, A.D.

    2005-01-01

    Surface energy exchanges were measured in a sequence of five sites representing the major vegetation types in the transition from arctic tundra to forest. This is the major transition in vegetation structure in northern high latitudes. We examined the influence of vegetation structure on the rates of sensible heating and evapotranspiration to assess the potential feedbacks to climate if high-latitude warming were to change the distribution of these vegetation types. Measurements were made at Council on the Seward Peninsula, Alaska, at representative tundra, low shrub, tall shrub, woodland (treeline), and boreal forest sites. Structural differences across the transition from tundra to forest included an increase in the leaf area index (LAI) from 0.52 to 2.76, an increase in canopy height from 0.1 to 6.1 m, and a general increase in canopy complexity. These changes in vegetation structure resulted in a decrease in albedo from 0.19 to 0.10 as well as changes to the partitioning of energy at the surface. Bulk surface resistance to water vapor flux remained virtually constant across sites, apparently because the combined soil and moss evaporation decreased while transpiration increased along the transect from tundra to forest. In general, sites became relatively warmer and drier along the transect with the convective fluxes being increasingly dominated by sensible heating, as evident by an increasing Bowen ratio from 0.94 to 1.22. The difference in growing season average daily sensible heating between tundra and forest was 21 W m-2. Fluxes changed non-linearly along the transition, with both shrubs and trees substantially enhancing heat transfer to the atmosphere. These changes in vegetation structure that increase sensible heating could feed back to enhance warming at local to regional scales. The magnitude of these vegetation effects on potential high-latitude warming is two to three times greater than suggested by previous modeling studies. ?? 2005 Elsevier B.V. All

  17. Atmospheric loading of nitrogen to Alpine Tundra in the Colorado Front Range

    NASA Astrophysics Data System (ADS)

    Sievering, H.; Burton, D.; Caine, N.

    1992-12-01

    Dry deposition of atmospheric nitrogen gas and aerosol species was estimated for the alpine tundra of Niwot Ridge, 3525 m elevation in the Colorado Rockies. Comparisons, for the 4 month long growing season and the remaining 8 months of the year, were made with wet deposition and throughfall incident measurements taken during 1987-1989. Dry deposition of N to the tundra is estimated to be equal to or slightly greater than its wet deposition. During the mid-May to mid-September growing season, atmospheric N deposition is >1.0 mg N m-2d-1 directly from the atmosphere with a similar amount contributed indirectly as NO3-N in snowmelt water as a result of dry and wet deposition to the winter snowpack. The total N deposition to Niwot Ridge tundra during the growing season of about 2 mg N m-2d-1 may be compared to an earlier measurement of dry plus fog deposition (1 - 2 mg N m-2d-1) to a subalpine coniferous canopy at Niwot Ridge. Nitrate yields from two small drainage basins at Niwot Ridge match these fluxes. Seven years of record from an unvegetated glacial cirque suggest an average yield from the alpine of 0.7 mg N m-2d-1. The equivalent estimate for a basin with 50% tundra vegetation cover is 0.4 mg N m-2d-1. The contrast in these two estimates of daily averaged N yields for the entire year suggests the retention of nearly 1 mg N m-2d-1 during the growing season in the more vegetated basin. The sink for this N could be the tundra soil and vegetation where biological activity is often limited by the availability of N.

  18. Will Arctic ground squirrels impede or accelerate climate-induced vegetation changes to the Arctic tundra?

    NASA Astrophysics Data System (ADS)

    Dalton, J.; Flower, C. E.; Brown, J.; Gonzalez-Meler, M. A.; Whelan, C.

    2014-12-01

    Considerable attention has been given to the climate feedbacks associated with predicted vegetation shifts in the Arctic tundra in response to global environmental change. However, little is known regarding the extent to which consumers can facilitate or respond to shrub expansion. Arctic ground squirrels, the largest and most northern ground squirrel, are abundant and widespread throughout the North American tundra. Their broad diet of seeds, flowers, herbage, bird's eggs and meat speaks to the need to breed, feed, and fatten in a span of some 12-16 weeks that separate their 8-9 month bouts of hibernation with the potential consequence to impact ecosystem dynamics. Therefore Arctic ground squirrels are a good candidate to evaluate whether consumers are mere responders (bottom-up effects) or drivers (top-down) of the observed and predicted vegetation changes. As a start towards this question, we measured the foraging intensity (giving-up densities) of Arctic ground squirrels in experimental food patches within which the squirrels experience diminishing returns as they seek the raisins and peanuts that we provided at the Toolik Lake field station in northern Alaska. If the squirrels show their highest feeding intensity in the shrubs, they may impede vegetation shifts by slowing the establishment and expansion of shrubs in the tundra. Conversely, if they show their lowest feeding intensity within shrub dominated areas, they may accelerate vegetation shifts. We found neither. Feeding intensity varied most among transects and times of day, and least along a tundra-to-shrub vegetation gradient. This suggests that the impacts of squirrels will be heterogeneous - in places responders and in others drivers. We should not be surprised then to see patches of accelerated and impeded vegetation changes in the tundra ecosystem. Some of these patterns may be predictable from the foraging behavior of Arctic ground squirrels.

  19. Greater deciduous shrub abundance extends tundra peak season and increases modeled net CO2 uptake.

    PubMed

    Sweet, Shannan K; Griffin, Kevin L; Steltzer, Heidi; Gough, Laura; Boelman, Natalie T

    2015-06-01

    Satellite studies of the terrestrial Arctic report increased summer greening and longer overall growing and peak seasons since the 1980s, which increases productivity and the period of carbon uptake. These trends are attributed to increasing air temperatures and reduced snow cover duration in spring and fall. Concurrently, deciduous shrubs are becoming increasingly abundant in tundra landscapes, which may also impact canopy phenology and productivity. Our aim was to determine the influence of greater deciduous shrub abundance on tundra canopy phenology and subsequent impacts on net ecosystem carbon exchange (NEE) during the growing and peak seasons in the arctic foothills region of Alaska. We compared deciduous shrub-dominated and evergreen/graminoid-dominated community-level canopy phenology throughout the growing season using the normalized difference vegetation index (NDVI). We used a tundra plant-community-specific leaf area index (LAI) model to estimate LAI throughout the green season and a tundra-specific NEE model to estimate the impact of greater deciduous shrub abundance and associated shifts in both leaf area and canopy phenology on tundra carbon flux. We found that deciduous shrub canopies reached the onset of peak greenness 13 days earlier and the onset of senescence 3 days earlier compared to evergreen/graminoid canopies, resulting in a 10-day extension of the peak season. The combined effect of the longer peak season and greater leaf area of deciduous shrub canopies almost tripled the modeled net carbon uptake of deciduous shrub communities compared to evergreen/graminoid communities, while the longer peak season alone resulted in 84% greater carbon uptake in deciduous shrub communities. These results suggest that greater deciduous shrub abundance increases carbon uptake not only due to greater leaf area, but also due to an extension of the period of peak greenness, which extends the period of maximum carbon uptake. PMID:25556338

  20. Algal Species and Light Microenvironment in a Low-pH, Geothermal Microbial Mat Community

    PubMed Central

    Ferris, M. J.; Sheehan, K. B.; Kühl, M.; Cooksey, K.; Wigglesworth-Cooksey, B.; Harvey, R.; Henson, J. M.

    2005-01-01

    Unicellular algae are the predominant microbial mat-forming phototrophs in the extreme environments of acidic geothermal springs. The ecology of these algae is not well known because concepts of species composition are inferred from cultivated isolates and microscopic observations, methods known to provide incomplete and inaccurate assessments of species in situ. We used sequence analysis of 18S rRNA genes PCR amplified from mat samples from different seasons and different temperatures along a thermal gradient to identify algae in an often-studied acidic (pH 2.7) geothermal creek in Yellowstone National Park. Fiber-optic microprobes were used to show that light for algal photosynthesis is attenuated to <1% over the 1-mm surface interval of the mat. Three algal sequences were detected, and each was present year-round. A Cyanidioschyzon merolae sequence was predominant at temperatures of ≥49°C. A Chlorella protothecoides var. acidicola sequence and a Paradoxia multisita-like sequence were predominant at temperatures of ≤39°C. PMID:16269755

  1. Algal species and light microenvironment in a low-pH, geothermal microbial mat community.

    PubMed

    Ferris, M J; Sheehan, K B; Kühl, M; Cooksey, K; Wigglesworth-Cooksey, B; Harvey, R; Henson, J M

    2005-11-01

    Unicellular algae are the predominant microbial mat-forming phototrophs in the extreme environments of acidic geothermal springs. The ecology of these algae is not well known because concepts of species composition are inferred from cultivated isolates and microscopic observations, methods known to provide incomplete and inaccurate assessments of species in situ. We used sequence analysis of 18S rRNA genes PCR amplified from mat samples from different seasons and different temperatures along a thermal gradient to identify algae in an often-studied acidic (pH 2.7) geothermal creek in Yellowstone National Park. Fiber-optic microprobes were used to show that light for algal photosynthesis is attenuated to < 1% over the 1-mm surface interval of the mat. Three algal sequences were detected, and each was present year-round. A Cyanidioschyzon merolae sequence was predominant at temperatures of > or = 49 degrees C. A Chlorella protothecoides var. acidicola sequence and a Paradoxia multisita-like sequence were predominant at temperatures of < or = 39 degrees C. PMID:16269755

  2. Pressure influence on the structural characteristics of modified absorptive glass mat separators: A standard contact porosimetry study

    NASA Astrophysics Data System (ADS)

    Burashnikova, M. M.; Khramkova, T. S.; Kazarinov, I. A.; Shmakov, S. L.

    2015-09-01

    The article presents a comparative analysis of the structural characteristics of absorptive glass mats manufactured by "Hollingsworth & Vose" (a 2.8 mm thickness) and "Bernard Dumas" (a 3.0 mm thickness) modified by impregnation with polymeric emulsions based on polyvinylidene fluoride, a polyvinylpyrrolidone styrene copolymer, and polytetrafluoroethylene, by means of standard contact porosimetry. The key study is influence of features of the porous structure on the compression properties, the rate of wicking, and the oxygen cycle efficiency in lead-acid battery mock-ups under several plate-group compression pressures. It is found that the treatment of the absorptive glass mat separators with polymeric emulsions leads to redistribution of their pores by size. An increased pressure in the electrode unit insignificantly changes the pore structure of the modified absorptive glass mat separators, and the oxygen cycle efficiency rises in comparison with unmodified separators.

  3. Research on Bayes matting algorithm based on Gaussian mixture model

    NASA Astrophysics Data System (ADS)

    Quan, Wei; Jiang, Shan; Han, Cheng; Zhang, Chao; Jiang, Zhengang

    2015-12-01

    The digital matting problem is a classical problem of imaging. It aims at separating non-rectangular foreground objects from a background image, and compositing with a new background image. Accurate matting determines the quality of the compositing image. A Bayesian matting Algorithm Based on Gaussian Mixture Model is proposed to solve this matting problem. Firstly, the traditional Bayesian framework is improved by introducing Gaussian mixture model. Then, a weighting factor is added in order to suppress the noises of the compositing images. Finally, the effect is further improved by regulating the user's input. This algorithm is applied to matting jobs of classical images. The results are compared to the traditional Bayesian method. It is shown that our algorithm has better performance in detail such as hair. Our algorithm eliminates the noise well. And it is very effectively in dealing with the kind of work, such as interested objects with intricate boundaries.

  4. Characterization and in vitro evaluation of electrospun chitosan/polycaprolactone blend fibrous mat for skin tissue engineering.

    PubMed

    Prasad, Tilak; Shabeena, E A; Vinod, D; Kumary, T V; Anil Kumar, P R

    2015-01-01

    The electrospinning technique allows engineering biomimetic scaffolds within micro to nanoscale range mimicking natural extracellular matrix (ECM). Chitosan (CS) and polycaprolactone (PCL) were dissolved in a modified solvent mixture consisting of formic acid and acetone (3:7) and mixed in different weight ratios to get chitosan-polycaprolactone [CS-PCL] blend solutions. The CS-PCL blend polymer was electrospun in the same solvent system and compared with PCL. The physicochemical characterization of the electrospun fibrous mats was done using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), tensile test, swelling properties, water contact angle (WCA) analysis, surface profilometry and thermo gravimetric analysis (TGA). The CS-PCL fibrous mat showed decreased hydrophobicity. The CS-PCL mats also showed improved swelling property, tensile strength, thermal stability and surface roughness. The cytocompatibility of the CS-PCL and PCL fibrous mats were examined using mouse fibroblast (L-929) cell line by direct contact and cellular activity with extract of materials confirmed non-cytotoxic nature. The potential of CS-PCL and PCL fibrous mats as skin tissue engineering scaffolds were assessed by cell adhesion, viability, proliferation and actin distribution using human keratinocytes (HaCaT) and L-929 cell lines. Results indicate that CS-PCL is a better scaffold for attachment and proliferation of keratinocytes and is a potential material for skin tissue engineering. PMID:25578706

  5. Benthic Marine Cyanobacterial Mat Ecosystems: Biogeochemistry and Biomarkers

    NASA Technical Reports Server (NTRS)

    DesMarais, David J.; DeVincenzi, Donald (Technical Monitor)

    2001-01-01

    Cyanobacterial mats are complete ecosystems that can include processes of primary production, diagenesis and lithification. Light sustains oxygenic photosynthesis, which in turn provides energy, organic matter and oxygen to the community. Due to both absorption and scattering phenomena, incident light is transformed with depth in the mat, both in intensity and spectral composition. Mobile photo synthesizers optimize their position with respect to this light gradient. When photosynthesis ceases at night, the upper layers of the mat become reduced and sulfidic. Counteracting gradients of oxygen and sulfide combine to provide daily-contrasting environments separated on a scale of a few mm. The functional complexity of mats, coupled with the highly proximal and ordered spatial arrangement of biota, offers the potential for a staggering number of interactions. At a minimum, the products of each functional group of microorganisms affect the other groups both positively and negatively. For example, cyanobacteria generate organic matter (potential substrates) but also oxygen (a toxin for many anaerobes). Anaerobic activity recycles nutrients to the photosynthesizers but also generates potentially toxic sulfide. The combination of benefits and hazards of light, oxygen and sulfide promotes the allocation of the various essential mat processes between light and dark periods, and to various depths in the mat. Observations of mats have produced numerous surprises. For example, obligately anaerobic processes can occur in the presence of abundant oxygen, highly reduced gases are produced in the presence of abundant sulfate, meiofauna thrive at high sulfide concentrations, and the mats' constituent populations respond to environmental changes in complex ways. While photosynthetic bacteria dominate the biomass and productivity of the mat, nonphotosynthetic, anaerobic processes constitute the ultimate biological filter on the ecosystem's emergent biosignatures, including those

  6. Chlorophyll and carotenoid pigments in solar saltern microbial mats

    NASA Astrophysics Data System (ADS)

    Villanueva, Joan; Grimalt, Joan O.; de Wit, Rutger; Keely, Brendan J.; Maxwell, James R.

    1994-11-01

    The distributions of carotenoids, chlorophylls, and their degradation products have been studied in two microbial mat systems developed in the calcite and calcite/gypsum evaporite domains of a solar saltern system. Phormidium valderianum and Microcoleus chthonoplastes are the dominant cyanobacterial species, respectively, and large amounts of Chloroflexus-like bacteria occur in the carbonate/gypsum mat. In both systems, the major pigments are chlorophyll a, zeaxanthin, β-carotene and myxoxanthophyll, which originate from these mat-building cyanobacteria. This common feature contrasts with differences in other pigments that are specific for each mat community. Thus, chlorophyll c and fucoxanthin, reflecting diatom inputs, are only found in the calcite mat, whereas the calcite/gypsum mat contains high concentrations of bacteriochlorophylls c produced by the multicellular green filamentous bacteria. In both cases, the depth concentration profiles (0-30 and 0-40 mm) show a relatively good preservation of the cyanobacterial carotenoids, zeaxanthin, β-carotene, myxoxanthophyll, and echinenone. This contrasts with the extensive biodegradation of cyanobacterial remains observed microscopically. Fucoxanthin in the calcite mat is also transformed at a faster rate than the cyanobacterial carotenoids. Chlorophyll a, the major pigment in both mats, exhibits different transformation pathways. In the calcite/gypsum mat, it is transformed via C-13 2 carbomethoxy defunctionalization prior to loss of the phytyl chain, leading to the formation of pyrophaeophytin a and, subsequently, pyrophaeophorbide a. On the other hand, the occurrence of the enzyme chlorophyllase, attributed to diatoms in the calcite mat, gives rise to extensive phytyl hydrolysis, with the formation of chlorophyllide a, pyrophaeophorbide a and, in minor proportion, phaeophorbide a. Studies of the sources of the photosynthetic pigments and of their transformation pathways in such simplified ecosystems provide a

  7. Elastic-plastic behavior of non-woven fibrous mats

    NASA Astrophysics Data System (ADS)

    Silberstein, Meredith N.; Pai, Chia-Ling; Rutledge, Gregory C.; Boyce, Mary C.

    2012-02-01

    Electrospinning is a novel method for creating non-woven polymer mats that have high surface area and high porosity. These attributes make them ideal candidates for multifunctional composites. Understanding the mechanical properties as a function of fiber properties and mat microstructure can aid in designing these composites. Further, a constitutive model which captures the membrane stress-strain behavior as a function of fiber properties and the geometry of the fibrous network would be a powerful design tool. Here, mats electrospun from amorphous polyamide are used as a model system. The elastic-plastic behavior of single fibers are obtained in tensile tests. Uniaxial monotonic and cyclic tensile tests are conducted on non-woven mats. The mat exhibits elastic-plastic stress-strain behavior. The transverse strain behavior provides important complementary data, showing a negligible initial Poisson's ratio followed by a transverse:axial strain ratio greater than -1:1 after an axial strain of 0.02. A triangulated framework has been developed to emulate the fibrous network structure of the mat. The micromechanically based model incorporates the elastic-plastic behavior of single fibers into a macroscopic membrane model of the mat. This representative volume element based model is shown to capture the uniaxial elastic-plastic response of the mat under monotonic and cyclic loading. The initial modulus and yield stress of the mat are governed by the fiber properties, the network geometry, and the network density. The transverse strain behavior is linked to discrete deformation mechanisms of the fibrous mat structure including fiber alignment, fiber bending, and network consolidation. The model is further validated in comparison to experiments under different constrained axial loading conditions and found to capture the constraint effect on stiffness, yield, post-yield hardening, and post-yield transverse strain behavior. Due to the direct connection between

  8. Lipid Biomarkers and Carbon Isotope Signatures of a Microbial (Beggiatoa) Mat Associated with Gas Hydrates in the Gulf of Mexico

    PubMed Central

    Zhang, Chuanlun L.; Huang, Zhiyong; Cantu, James; Pancost, Richard D.; Brigmon, Robin L.; Lyons, Timothy W.; Sassen, Roger

    2005-01-01

    White and orange mats are ubiquitous on surface sediments associated with gas hydrates and cold seeps in the Gulf of Mexico. The goal of this study was to determine the predominant pathways for carbon cycling within an orange mat in Green Canyon (GC) block GC 234 in the Gulf of Mexico. Our approach incorporated laser-scanning confocal microscopy, lipid biomarkers, stable carbon isotopes, and 16S rRNA gene sequencing. Confocal microscopy showed the predominance of filamentous microorganisms (4 to 5 μm in diameter) in the mat sample, which are characteristic of Beggiatoa. The phospholipid fatty acids extracted from the mat sample were dominated by 16:1ω7c/t (67%), 18:1ω7c (17%), and 16:0 (8%), which are consistent with lipid profiles of known sulfur-oxidizing bacteria, including Beggiatoa. These results are supported by the 16S rRNA gene analysis of the mat material, which yielded sequences that are all related to the vacuolated sulfur-oxidizing bacteria, including Beggiatoa, Thioploca, and Thiomargarita. The δ13C value of total biomass was −28.6‰; those of individual fatty acids were −29.4 to −33.7‰. These values suggested heterotrophic growth of Beggiatoa on organic substrates that may have δ13C values characteristic of crude oil or on their by-products from microbial degradation. This study demonstrated that integrating lipid biomarkers, stable isotopes, and molecular DNA could enhance our understanding of the metabolic functions of Beggiatoa mats in sulfide-rich marine sediments associated with gas hydrates in the Gulf of Mexico and other locations. PMID:15812044

  9. Lipid biomarkers and carbon isotope signatures of a microbial (Beggiatoa) mat associated with gas hydrates in the gulf of Mexico.

    PubMed

    Zhang, Chuanlun L; Huang, Zhiyong; Cantu, James; Pancost, Richard D; Brigmon, Robin L; Lyons, Timothy W; Sassen, Roger

    2005-04-01

    White and orange mats are ubiquitous on surface sediments associated with gas hydrates and cold seeps in the Gulf of Mexico. The goal of this study was to determine the predominant pathways for carbon cycling within an orange mat in Green Canyon (GC) block GC 234 in the Gulf of Mexico. Our approach incorporated laser-scanning confocal microscopy, lipid biomarkers, stable carbon isotopes, and 16S rRNA gene sequencing. Confocal microscopy showed the predominance of filamentous microorganisms (4 to 5 mum in diameter) in the mat sample, which are characteristic of Beggiatoa. The phospholipid fatty acids extracted from the mat sample were dominated by 16:1omega7c/t (67%), 18:1omega7c (17%), and 16:0 (8%), which are consistent with lipid profiles of known sulfur-oxidizing bacteria, including Beggiatoa. These results are supported by the 16S rRNA gene analysis of the mat material, which yielded sequences that are all related to the vacuolated sulfur-oxidizing bacteria, including Beggiatoa, Thioploca, and Thiomargarita. The delta13C value of total biomass was -28.6 per thousand; those of individual fatty acids were -29.4 to -33.7 per thousand. These values suggested heterotrophic growth of Beggiatoa on organic substrates that may have delta13C values characteristic of crude oil or on their by-products from microbial degradation. This study demonstrated that integrating lipid biomarkers, stable isotopes, and molecular DNA could enhance our understanding of the metabolic functions of Beggiatoa mats in sulfide-rich marine sediments associated with gas hydrates in the Gulf of Mexico and other locations. PMID:15812044

  10. Identification And Survival Of Bacteriohopanepolyol In A Hot Spring Microbial Mat

    NASA Technical Reports Server (NTRS)

    Janke, Linda L.; Chang, Sherwood (Technical Monitor)

    1995-01-01

    The polar lipids of a hot spring microbial mat located in Yellowstone National Park were examined for the presence of bacteriohopanepolvols (BHP). BHP are a group of molecules consisting of a hopanoid (peotacyclic triterpene) linked via a n-alkyl polyhydroxylated chain to a variety of polar end groups. BHP have been isolated in varying amounts from phylogenetically diverse eubacterial groups including cyanobacteria, methanotrophs and the Rhodospirillaceae. The hopanoids are excellent biomarkers and have been detected in sedimentary rocks as old as 1.7 bya. In order to interpret the ancient organic record, it is important to understand the abundance, source and fate of such biomarker compounds in microbial mats. A 40 sq cm mat section was taken from a 52 to 55 C site in the effluent channel of Octopus Spring and was sampled vertically over approximately 16 mm. The first 5-6 mm was sectioned into a top green layer (310 mg dry weight) and several subjacent, deep orange layers (240 and 250 mg, respectively). The lower 10 mm of the mat was sectioned into two gelatinous orange layers containing a siliceous gritty material (260 and 440 mg) which increased with depth, and a bottom layer composed almost exclusively of siliceous sinter (4.1 g). The progressive decrease in total organic carbon from 45% in the top green layer to only 4% in the bottom layer reflects the observed increase in siliceous deposition. GC-MS analysis of the phospholipid and glycolipid fatty acids yielded predominantly saturated normal chain acids, n-15 to n-18, and iso-branched acids, i-15 to i-17. Small amounts of unsaturated fatty acids (16:1, two positional isomers of 18:1, and two cyclopropyl acids, C(sub 17) and C(sub 19)) were present mainly in the top layer. Esterified fatty acid which is a good index for intact cellular membrane, i.e. viable organisms, was highest in the top two layers (203 and 231 micro g/mg total lipid, respectively) and gradually decreased to 66 micro g/mg total lipid in

  11. Diel metabolomics analysis of a hot spring chlorophototrophic microbial mat leads to new hypotheses of community member metabolisms.

    PubMed

    Kim, Young-Mo; Nowack, Shane; Olsen, Millie T; Becraft, Eric D; Wood, Jason M; Thiel, Vera; Klapper, Isaac; Kühl, Michael; Fredrickson, James K; Bryant, Donald A; Ward, David M; Metz, Thomas O

    2015-01-01

    Dynamic environmental factors such as light, nutrients, salt, and temperature continuously affect chlorophototrophic microbial mats, requiring adaptive and acclimative responses to stabilize composition and function. Quantitative metabolomics analysis can provide insights into metabolite dynamics for understanding community response to such changing environmental conditions. In this study, we quantified volatile organic acids, polar metabolites (amino acids, glycolytic and citric acid cycle intermediates, nucleobases, nucleosides, and sugars), wax esters, and polyhydroxyalkanoates, resulting in the identification of 104 metabolites and related molecules in thermal chlorophototrophic microbial mat cores collected over a diel cycle in Mushroom Spring, Yellowstone National Park. A limited number of predominant taxa inhabit this community and their functional potentials have been previously identified through metagenomic and metatranscriptomic analyses and in situ metabolisms, and metabolic interactions among these taxa have been hypothesized. Our metabolomics results confirmed the diel cycling of photorespiration (e.g., glycolate) and fermentation (e.g., acetate, propionate, and lactate) products, the carbon storage polymers polyhydroxyalkanoates, and dissolved gasses (e.g., H2 and CO2) in the waters overlying the mat, which were hypothesized to occur in major mat chlorophototrophic community members. In addition, we have formulated the following new hypotheses: (1) the morning hours are a time of biosynthesis of amino acids, DNA, and RNA; (2) photo-inhibited cells may also produce lactate via fermentation as an alternate metabolism; (3) glycolate and lactate are exchanged among Synechococcus and Roseiflexus spp.; and (4) fluctuations in many metabolite pools (e.g., wax esters) at different times of day result from species found at different depths within the mat responding to temporal differences in their niches. PMID:25941514

  12. Diel metabolomics analysis of a hot spring chlorophototrophic microbial mat leads to new hypotheses of community member metabolisms

    PubMed Central

    Kim, Young-Mo; Nowack, Shane; Olsen, Millie T.; Becraft, Eric D.; Wood, Jason M.; Thiel, Vera; Klapper, Isaac; Kühl, Michael; Fredrickson, James K.; Bryant, Donald A.; Ward, David M.; Metz, Thomas O.

    2015-01-01

    Dynamic environmental factors such as light, nutrients, salt, and temperature continuously affect chlorophototrophic microbial mats, requiring adaptive and acclimative responses to stabilize composition and function. Quantitative metabolomics analysis can provide insights into metabolite dynamics for understanding community response to such changing environmental conditions. In this study, we quantified volatile organic acids, polar metabolites (amino acids, glycolytic and citric acid cycle intermediates, nucleobases, nucleosides, and sugars), wax esters, and polyhydroxyalkanoates, resulting in the identification of 104 metabolites and related molecules in thermal chlorophototrophic microbial mat cores collected over a diel cycle in Mushroom Spring, Yellowstone National Park. A limited number of predominant taxa inhabit this community and their functional potentials have been previously identified through metagenomic and metatranscriptomic analyses and in situ metabolisms, and metabolic interactions among these taxa have been hypothesized. Our metabolomics results confirmed the diel cycling of photorespiration (e.g., glycolate) and fermentation (e.g., acetate, propionate, and lactate) products, the carbon storage polymers polyhydroxyalkanoates, and dissolved gasses (e.g., H2 and CO2) in the waters overlying the mat, which were hypothesized to occur in major mat chlorophototrophic community members. In addition, we have formulated the following new hypotheses: (1) the morning hours are a time of biosynthesis of amino acids, DNA, and RNA; (2) photo-inhibited cells may also produce lactate via fermentation as an alternate metabolism; (3) glycolate and lactate are exchanged among Synechococcus and Roseiflexus spp.; and (4) fluctuations in many metabolite pools (e.g., wax esters) at different times of day result from species found at different depths within the mat responding to temporal differences in their niches. PMID:25941514

  13. Diel metabolomics analysis of a hot spring chlorophototrophic microbial mat leads to new hypotheses of community member metabolisms

    DOE PAGESBeta

    Kim, Young-Mo; Nowack, Shane; Olsen, Millie; Becraft, Eric; Wood, Jason M.; Thiel, Vera; Klapper, Isaac; Kuhl, Michael; Fredrickson, Jim K.; Bryant, Donald A.; et al

    2015-04-17

    Dynamic environmental factors such as light, nutrients, salt, and temperature continuously affect chlorophototrophic microbial mats, requiring adaptative and acclimative responses to stabilize composition and function. Quantitative metabolomics analysis can provide insights into metabolite dynamics for understanding community response to such changing environmental conditions. In this study, we quantified volatile organic acids, polar metabolites (amino acids, glycolytic and citric acid cycle intermediates, nucleobases, nucleosides, and sugars), wax esters, and polyhydroxyalkanoates, resulting in the identification of 104 metabolites and related molecules in thermal chlorophototrophic microbial mat cores collected over a diel cycle in Mushroom Spring, Yellowstone National Park. A limited number ofmore » predominant taxa inhabiting this community and their functional potentials have been previously identified through metagenomic and metatranscriptomic analyses and in situ metabolisms and metabolic interactions among these taxa have been hypothesized. Our metabolomics results confirmed the diel cycling of photorespiration (e.g. glycolate) and fermentation (e.g. acetate, propionate, and lactate) products, the carbon storage polymers polyhydroxyalkanoates, and dissolved gases (e.g. H2 and CO2) in the waters overlying the mat, which were hypothesized to occur in major mat chlorophototrophic community members. In addition, we have formulated the following new hypotheses: 1) the morning hours are a time of biosynthesis of amino acids, DNA, and RNA; 2) Synechococcus spp. produce CH4 via metabolism of phosphonates, and photo-inhibited cells may also produce lactate via fermentation as an alternate metabolism; 3) glycolate and lactate are exchanged among Synechococcus and Roseiflexus spp.; and 4) fluctuations in many metabolite pools (e.g. wax esters) at different times of day result from species found at different depths within the mat responding to temporal differences

  14. Diel metabolomics analysis of a hot spring chlorophototrophic microbial mat leads to new hypotheses of community member metabolisms

    SciTech Connect

    Kim, Young-Mo; Nowack, Shane; Olsen, Millie; Becraft, Eric; Wood, Jason M.; Thiel, Vera; Klapper, Isaac; Kuhl, Michael; Fredrickson, Jim K.; Bryant, Donald A.; Ward, David M.; Metz, Thomas O.

    2015-04-17

    Dynamic environmental factors such as light, nutrients, salt, and temperature continuously affect chlorophototrophic microbial mats, requiring adaptative and acclimative responses to stabilize composition and function. Quantitative metabolomics analysis can provide insights into metabolite dynamics for understanding community response to such changing environmental conditions. In this study, we quantified volatile organic acids, polar metabolites (amino acids, glycolytic and citric acid cycle intermediates, nucleobases, nucleosides, and sugars), wax esters, and polyhydroxyalkanoates, resulting in the identification of 104 metabolites and related molecules in thermal chlorophototrophic microbial mat cores collected over a diel cycle in Mushroom Spring, Yellowstone National Park. A limited number of predominant taxa inhabiting this community and their functional potentials have been previously identified through metagenomic and metatranscriptomic analyses and in situ metabolisms and metabolic interactions among these taxa have been hypothesized. Our metabolomics results confirmed the diel cycling of photorespiration (e.g. glycolate) and fermentation (e.g. acetate, propionate, and lactate) products, the carbon storage polymers polyhydroxyalkanoates, and dissolved gases (e.g. H2 and CO2) in the waters overlying the mat, which were hypothesized to occur in major mat chlorophototrophic community members. In addition, we have formulated the following new hypotheses: 1) the morning hours are a time of biosynthesis of amino acids, DNA, and RNA; 2) Synechococcus spp. produce CH4 via metabolism of phosphonates, and photo-inhibited cells may also produce lactate via fermentation as an alternate metabolism; 3) glycolate and lactate are exchanged among Synechococcus and Roseiflexus spp.; and 4) fluctuations in many metabolite pools (e.g. wax esters) at different times of day result from species found at different depths within the mat responding to temporal differences in their

  15. The temperature response of methane emission in Arctic wet sedge tundra

    NASA Astrophysics Data System (ADS)

    Lim, Edward; Zona, Donatella

    2015-04-01

    Since the last glacial maximum Arctic tundra soils have acted as an important carbon sink, having accumulated carbon under cold, anaerobic conditions (Zona et al. 2009). Several studies indicate that recent climate warming has altered this balance, with the Arctic tundra now posited to be a significant annual source of atmospheric methane (CH4) (McGuire et al. 2012). Nonetheless, the response of Arctic tundra CH4 fluxes to continued climate warming remains uncertain. Laboratory and field studies indicate that CH4 fluxes are temperature sensitive, thus accurate calculation of the temperature sensitivity is vital for the prediction of future CH4 emission. For this, the increase in reaction rate over a 10°C range (Q10) is frequently used, with single fixed Q10 values (between 2 and 4) commonly incorporated into climate-carbon cycle models. However, the temperature sensitivity of CH4 emission can vary considerably depending on factors such as vegetation composition, water table and season. This promotes the use of spatially and seasonally variable Q10 values for accurate CH4 flux estimation under different future climate change scenarios. This study investigates the temperature sensitivity (Q10) of Arctic tundra methane fluxes, using an extensive number of soil cores (48) extracted from wet sedge polygonal tundra (Barrow Experimental Observatory, Alaska). 'Wet' and 'dry' cores were taken from the centre and raised perimeter of ice-wedge polygons, where the water tables are 0cm and -15cm respectively. Cores were incubated in two controlled environment chambers (University of Sheffield, UK) for 12 weeks under different thaw depth treatments (control and control + 6.8cm), water tables (surface and -15cm), and CO2 concentrations (400ppm and 850ppm) in a multifactorial manner. Chamber temperature was gradually increased from -5°C to 20°C, then gradually decreased to -5°C, with each temperature stage lasting one week. Average CH4 fluxes from 'dry' cores were consistently

  16. A Recombinationally Repressed Region between Mat2 and Mat3 Loci Shares Homology to Centromeric Repeats and Regulates Directionality of Mating-Type Switching in Fission Yeast

    PubMed Central

    Grewal, SIS.; Klar, AJS.

    1997-01-01

    Cells of the fission yeast Schizosaccharomyces pombe switch mating type by replacing genetic information at the transcriptionally active mat1 locus with sequences copied from one of two closely linked silent loci, mat2-P or mat3-M. By a process referred to as directionality of switching, cells predominantly switch to the opposite mat1 allele; the mat1-P allele preferentially recombines with mat3, while mat1-M selects the mat2. In contrast to efficient recombination at mat1, recombination within the adjoining mat2-mat3 interval is undetectable. We defined the role of sequences between mat2 and mat3, designated the K-region, in directionality as well as recombinational suppression. Cloning and sequencing analysis revealed that a part of the K-region is homologous to repeat sequences present at centromeres, which also display transcriptional and recombinational suppression. Replacement of 7.5 kb of the K-region with the ura4(+) gene affected directionality in a variegated manner. Analysis of the swi6-mod locus, which was previously shown to affect directionality, in KΔ::ura4(+) strains suggested the existence of at least two overlapping directionality mechanisms. Our work furthers the model that directionality is regulated by cell-type-specific organization of the heterochromatin-like structure in the mating-type region and provides evidence that the K-region contributes to silencing of the mat2-mat3 interval. PMID:9258669

  17. Biosphere/atmosphere CO2 exchange in tundra ecosystems - Community characteristics and relationships with multispectral surface reflectance

    NASA Technical Reports Server (NTRS)

    Whiting, Gary J.; Bartlett, David S.; Fan, Song-Miao; Bakwin, Peter S.; Wofsy, Steven C.

    1992-01-01

    CO2 exchange rates were measured at selected tundra sites near Bethel, Alaska using portable, climate-controlled, instrumented enclosures. The empirically modeled exchange rate for a representative area of vegetated tundra was 1.2 +/- 1.2 g/sq m/d, compared to a tower-measured exchange over the same time period of 1.1 +.0- 1.2 g/sq m/d. Net exchange in response to varying light levels was compared to wet meadow and dry upland tundra, and to the net exchange measured by the micrometeoroidal tower technique. The multispectral reflectance properties of the sites were measured and related to exchange rates in order to provide a quantitative foundation for the use of satellite remote sensing to monitor biosphere/atmosphere CO2 exchange in the tundra biome.

  18. The effect of a permafrost disturbance on growing-season carbon-dioxide fluxes in a high Arctic tundra ecosystem

    NASA Astrophysics Data System (ADS)

    Cassidy, A. E.; Christen, A.; Henry, G. H. R.

    2015-12-01

    Soil carbon stored in high-latitude permafrost landscapes is threatened by warming, and could contribute significant amounts of carbon to the atmosphere and hydrosphere as permafrost thaws. Permafrost disturbances, especially active layer detachments and retrogressive thaw slumps, have increased in frequency and magnitude across the Fosheim Peninsula, Ellesmere Island, Canada. To determine the effects of retrogressive thaw slumps on net ecosystem exchange (NEE) of CO2 in high Arctic tundra, we used two eddy covariance (EC) tower systems to simultaneously and continuously measure CO2 fluxes from a disturbed site and the surrounding undisturbed tundra. During the 32-day measurement period in the 2014 growing season the undisturbed tundra was a small net sink (NEE = -0.12 g C m-2 d-1); however, the disturbed terrain of the retrogressive thaw slump was a net source (NEE = +0.39 g C m-2 d-1). Over the measurement period, the undisturbed tundra sequestered 3.84 g C m-2, while the disturbed tundra released 12.48 g C m-2. Before full leaf out in early July, the undisturbed tundra was a small source of CO2, but shifted to a sink for the remainder of the sampling season (July), whereas the disturbed tundra remained a source of CO2 throughout the season. A static chamber system was also used to measure fluxes in the footprints of the two towers, in both disturbed and undisturbed tundra, and fluxes were partitioned into ecosystem respiration (Re) and gross primary production (GPP). Average GPP and Re found in disturbed tundra were smaller (+0.41 μmol m-2 s-1 and +0.50 μmol m-2 s-1, respectively) than those found in undisturbed tundra (+1.21 μmol m-2 s-1 and +1.00 μmol m-2 s-1, respectively). Our measurements indicated clearly that the permafrost disturbance changed the high Arctic tundra system from a sink to a source for CO2 during the growing season.

  19. The effect of a permafrost disturbance on growing-season carbon-dioxide fluxes in a high Arctic tundra ecosystem

    NASA Astrophysics Data System (ADS)

    Cassidy, Alison E.; Christen, Andreas; Henry, Gregory H. R.

    2016-04-01

    Soil carbon stored in high-latitude permafrost landscapes is threatened by warming and could contribute significant amounts of carbon to the atmosphere and hydrosphere as permafrost thaws. Thermokarst and permafrost disturbances, especially active layer detachments and retrogressive thaw slumps, are present across the Fosheim Peninsula, Ellesmere Island, Canada. To determine the effects of retrogressive thaw slumps on net ecosystem exchange (NEE) of CO2 in high Arctic tundra, we used two eddy covariance (EC) tower systems to simultaneously and continuously measure CO2 fluxes from a disturbed site and the surrounding undisturbed tundra. During the 32-day measurement period in the 2014 growing season, the undisturbed tundra was a small net sink (NEE = -0.1 g C m-2 d-1); however, the disturbed terrain of the retrogressive thaw slump was a net source (NEE = +0.4 g C m-2 d-1). Over the measurement period, the undisturbed tundra sequestered 3.8 g C m-2, while the disturbed tundra released 12.5 g C m-2. Before full leaf-out in early July, the undisturbed tundra was a small source of CO2 but shifted to a sink for the remainder of the sampling season (July), whereas the disturbed tundra remained a source of CO2 throughout the season. A static chamber system was also used to measure daytime fluxes in the footprints of the two towers, in both disturbed and undisturbed tundra, and fluxes were partitioned into ecosystem respiration (Re) and gross primary production (GPP). Average GPP and Re found in disturbed tundra were smaller (+0.40 µmol m-2 s-1 and +0.55 µmol m-2 s-1, respectively) than those found in undisturbed tundra (+1.19 µmol m-2 s-1 and +1.04 µmol m-2 s-1, respectively). Our measurements indicated clearly that the permafrost disturbance changed the high Arctic tundra system from a sink to a source for CO2 during the majority of the growing season (late June and July).

  20. Relative roles of different-sized herbivores and plant-plant interactions in tall shrub tundra vegetation

    NASA Astrophysics Data System (ADS)

    Ravolainen, Virve; Ims, Rolf; Bårdsen, Bård-Jørgen; Stien, Audun; Kollstrøm, Julie; Lægreid, Eiliv; Bråthen, Kari Anne

    2013-04-01

    Tall shrubs play important roles in the ecology of Arctic tundra ecosystems, including support of high shrub-associated biodiversity and regulation of a range of ecosystem processes. Tall shrub patches and herbaceous vegetation surrounding them often form a two-state vegetation mosaic. Such tall shrub tundra vegetation is an important locus for current vegetation changes in the Arctic. Both abiotic and biotic drivers are known to influence the shrub component. However, although expansion of the shrub state has received much focus lately, relative strengths of the multiple drivers of vegetation state are currently not fully understood. We investigated the role of herbivory relative to temperature and relative to plant-plant interactions, conducting a field survey and experimental studies at large spatial scales in riparian tall shrub tundra in Norway. We found both summer temperatures and summer grazing by reindeer (Rangifer tarandus) to affect tall shrub distribution and expansion potential. Furthermore, we found strong and rapid shrub growth change in response to abundance of key arctic herbivores; small rodents. Finally, we quantified the relative importance of neighboring plants and both herbivore types to recruiting tall shrubs. The previously unforeseen rate at which tall shrub tundra responded to altered herbivore pressures further exemplifies its central role in the tundra ecosystems, promoting tall shrub tundra as a bell-whether of change with respect to both abiotic and biotic drivers. While many of the results clearly relate to herbivory, neighboring plants or climate as drivers, some variation remains unexplained warranting future research focus on this highly dynamic part of the tundra ecosystem. Our results suggest that spatially variable biotic interactions are likely to modify forcing by climate, calling for an ecosystem approach when studying change in tundra ecosystems.

  1. The MAT Locus Genes Play Different Roles in Sexual Reproduction and Pathogenesis in Fusarium graminearum

    PubMed Central

    Juanyu; Zhang; Ma, Jiwen; Wu, Zhongshou; Wang, Guanghui; Wang, Chenfang; Xu, Jin-Rong

    2013-01-01

    Sexual reproduction plays a critical role in the infection cycle of Fusarium graminearum because ascospores are the primary inoculum. As a homothallic ascomycete, F. graminearum contains both the MAT1-1 and MAT1-2-1 loci in the genome. To better understand their functions and regulations in sexual reproduction and pathogenesis, in this study we assayed the expression, interactions, and mutant phenotypes of individual MAT locus genes. Whereas the expression of MAT1-1-1 and MAT12-1 rapidly increased after perithecial induction and began to decline after 1 day post-perithecial induction (dpi), the expression of MAT1-1-2 and MAT1-1-3 peaked at 4 dpi. MAT1-1-2 and MAT1-1-3 had a similar expression profile and likely are controlled by a bidirectional promoter. Although none of the MAT locus genes were essential for perithecium formation, all of them were required for ascosporogenesis in self-crosses. In outcrosses, the mat11-1-2 and mat11-1-3 mutants were fertile but the mat1-1-1 and mat1-2-1 mutants displayed male- and female-specific defects, respectively. The mat1-2-1 mutant was reduced in FgSO expression and hyphal fusion. Mat1-1-2 interacted with all other MAT locus transcription factors, suggesting that they may form a protein complex during sexual reproduction. Mat1-1-1 also interacted with FgMcm1, which may play a role in controlling cell identity and sexual development. Interestingly, the mat1-1-1 and mat1-2-1 mutants were reduced in virulence in corn stalk rot assays although none of the MAT locus genes was important for wheat infection. The MAT1-1-1 and MAT1-2-1 genes may play a host-specific role in colonization of corn stalks. PMID:23826182

  2. The MAT locus genes play different roles in sexual reproduction and pathogenesis in Fusarium graminearum.

    PubMed

    Zheng, Qian; Hou, Rui; Juanyu; Zhang; Ma, Jiwen; Wu, Zhongshou; Wang, Guanghui; Wang, Chenfang; Xu, Jin-Rong

    2013-01-01

    Sexual reproduction plays a critical role in the infection cycle of Fusarium graminearum because ascospores are the primary inoculum. As a homothallic ascomycete, F. graminearum contains both the MAT1-1 and MAT1-2-1 loci in the genome. To better understand their functions and regulations in sexual reproduction and pathogenesis, in this study we assayed the expression, interactions, and mutant phenotypes of individual MAT locus genes. Whereas the expression of MAT1-1-1 and MAT12-1 rapidly increased after perithecial induction and began to decline after 1 day post-perithecial induction (dpi), the expression of MAT1-1-2 and MAT1-1-3 peaked at 4 dpi. MAT1-1-2 and MAT1-1-3 had a similar expression profile and likely are controlled by a bidirectional promoter. Although none of the MAT locus genes were essential for perithecium formation, all of them were required for ascosporogenesis in self-crosses. In outcrosses, the mat11-1-2 and mat11-1-3 mutants were fertile but the mat1-1-1 and mat1-2-1 mutants displayed male- and female-specific defects, respectively. The mat1-2-1 mutant was reduced in FgSO expression and hyphal fusion. Mat1-1-2 interacted with all other MAT locus transcription factors, suggesting that they may form a protein complex during sexual reproduction. Mat1-1-1 also interacted with FgMcm1, which may play a role in controlling cell identity and sexual development. Interestingly, the mat1-1-1 and mat1-2-1 mutants were reduced in virulence in corn stalk rot assays although none of the MAT locus genes was important for wheat infection. The MAT1-1-1 and MAT1-2-1 genes may play a host-specific role in colonization of corn stalks. PMID:23826182

  3. Circumpolar Dynamics of Arctic Tundra Vegetation in Relation to Temperature Trends

    NASA Astrophysics Data System (ADS)

    Epstein, H. E.; Bhatt, U. S.; Raynolds, M. K.; Walker, D. A.; Reichle, L.

    2015-12-01

    Arctic tundra vegetation has generally exhibited a "greening" trend for at least the past three decades. However, these temporal trends in tundra vegetation are highly heterogeneous in space across different arctic regions, as well as showing variability over time. The factors controlling this variability are likely numerous with complex interactions, however, a first approach is to examine how vegetation dynamics relate to trends in temperature. We used a 32-year record (1982-2013) of the Normalized Difference Vegetation Index (NDVI) and Land Surface Temperatures from Advanced Very High Resolution Radiometer (AVHRR) sensors onboard NOAA satellites (GIMMS 3g dataset) to analyze observed changes in both aboveground tundra vegetation and surface temperatures. We divided the circumpolar dataset into two continental regions (North America and Eurasia), as well as by tundra subzone (A-E) sensu the Circumpolar Arctic Vegetation Map (CAVM). We 1) compared temporal trends in both MaxNDVI (peak values) and TI-NDVI (seasonally integrated values) with those of the Summer Warmth Index (SWI - sum of mean monthly temperatures > 0 °C); 2) assessed how the detrended interannual variabilities in NDVI compared to those of SWI; and 3) analyzed current and prior year SWI, as well as prior year NDVI, as controls on current year NDVI. Interannual coefficients of variation for SWI were 2.0 - 2.5 times greater than those for NDVI, and the temporal trendlines for NDVI were much "tighter" with greater r² values than those for SWI. Interannual variability in NDVI was greatest in the "Mid-Low" Arctic, whereas interannual variability in SWI was greatest in the most southern Arctic. Surprisingly, the observed relative rates of change in NDVI were greater than those of SWI for the warmer subzones for both North America and Eurasia. Finally, the change in NDVI from one year to the next was only weakly correlated with current year SWI. These results suggest that 1) there are clearly factors

  4. Tundra fire alters stream water chemistry and benthic invertebrate communities, North Slope, Alaska

    NASA Astrophysics Data System (ADS)

    Allen, A. R.; Bowden, W. B.; Kling, G. W.; Schuett, E.; Kostrzewski, J. M.; Kolden Abatzoglou, C.; Findlay, R. H.

    2010-12-01

    Increased fire frequency and severity are potentially important consequences of climate change in high latitude ecosystems. The 2007 Anaktuvuk River fire, which burned from July until October, is the largest recorded tundra fire from Alaska's north slope (≈1,000 km2). The immediate effects of wildfire on water chemistry and biotic assemblages in tundra streams are heretofore unknown. We hypothesized that a tundra fire would increase inorganic nutrient inputs to P-limited tundra streams, increasing primary production and altering benthic macroinvertebrate community structure. We examined linkages among: 1) percentage of riparian zone and overall watershed vegetation burned, 2) physical, chemical and biological stream characteristics, and 3) macroinvertebrate communities in streams draining burned and unburned watersheds during the summers of 2008 and 2009. Streams in burned watersheds contained higher mean concentrations of soluble reactive phosphorus (SRP), ammonium (NH4+), and dissolved organic carbon (DOC). In contrast, stream nitrate (NO3-) concentrations were lower in burned watersheds. The net result was that the tundra fire did not affect concentrations of dissolved inorganic nitrogen (NH4+ + NO3-). In spite of increased SRP, benthic chlorophyll-a biomass was not elevated. Macroinvertebrate abundances were 1.5 times higher in streams draining burned watersheds; Chironomidae midges, Nematodes, and Nemoura stoneflies showed the greatest increases in abundance. Multivariate multiple regression identified environmental parameters associated with the observed changes in the macroinvertebrate communities. Since we identified stream latitude as a significant predictor variable, latitude was included in the model as a covariate. After removing the variation associated with latitude, 67.3 % of the variance in macroinvertebrate community structure was explained by a subset of 7 predictor variables; DOC, conductivity, mean temperature, NO3-, mean discharge, SRP and NH

  5. The Pleistocene ``Tundra-Steppe'' and the productivity paradox: the landscape approach

    NASA Astrophysics Data System (ADS)

    Yurtsev, Boris A.

    2001-01-01

    "Tundra-steppe" means either a certain type of plant community with codominance of both steppe and tundra species (including prostrate shrubs), or a type of landscape, codominated by both steppe and tundra (Yurtsev, Relic Steppe Complexes of Northeastern Asia. Nauka Press, Novosibirsk (in Russian) 1981; In: Hopkins, Matthews Jr., Schweger, Young, (Eds.), Paleoecology of Beringia. Academic Press, New York, 1982, pp. 157-177). A discrepancy between Pleistocene glacial climates that were much colder and drier than present in Beringia and the highly diverse herbivorous fossil fauna (the "productivity paradox") is explained in terms of much greater diversity of herbaceous vegetation (grasses, sedges and forbs) in the mosaic of Beringian 'tundra-steppe' landscapes. Analysis of the relic distribution of some predominantly herbaceous plant communities throughout Beringia (Yurtsev, 1981, 1982, Komarovskiye chteniya (Vladivostok) 33 (1986) 3-53 (in Russian); Protection of Gene- and Coenotic Pool of the Herbaceous Biogeocoenoses, Sverdlovsk, 1988, pp. 128-129 (in Russian); Bridges of Science Between North America and the Russian Far East, 45th Arctic Science Conference, Abstracts, Vol. 1. Dalnauka Press, Vladivostok, 1994, p. 268; Paleontological Journal, 6 (1996)) provides the phytogeographic and landscape — ecological grounds for the reconstruction of plant cover of these landscapes. Dry watersheds and slopes had cryophytic (cold-adapted) steppes, cryoxerophytic (cold and dry-adapted) herbaceous and prostrate shrub-herbaceous communities, dry herb-prostrate shrub tundras, and tundra-steppe communities proper. All sorts of depressions on interfluves and in valleys along with concave pediments were occupied by dry steppe-meadows and brackish-water moist meadows. In some specific habitats sparse groupings of continental halophytes (plants growing in saline soils) of "arctic takkyrs", zoochoric (plants with seeds dispersed by animals) groupings of annual-biennial "ruderals

  6. Long-term recovery patterns of arctic tundra after winter seismic exploration.

    PubMed

    Jorgenson, Janet C; Ver Hoef, Jay M; Jorgenson, M T

    2010-01-01

    In response to the increasing global demand for energy, oil exploration and development are expanding into frontier areas of the Arctic, where slow-growing tundra vegetation and the underlying permafrost soils are very sensitive to disturbance. The creation of vehicle trails on the tundra from seismic exploration for oil has accelerated in the past decade, and the cumulative impact represents a geographic footprint that covers a greater extent of Alaska's North Slope tundra than all other direct human impacts combined. Seismic exploration for oil and gas was conducted on the coastal plain of the Arctic National Wildlife Refuge, Alaska, USA, in the winters of 1984 and 1985. This study documents recovery of vegetation and permafrost soils over a two-decade period after vehicle traffic on snow-covered tundra. Paired permanent vegetation plots (disturbed vs. reference) were monitored six times from 1984 to 2002. Data were collected on percent vegetative cover by plant species and on soil and ground ice characteristics. We developed Bayesian hierarchical models, with temporally and spatially autocorrelated errors, to analyze the effects of vegetation type and initial disturbance levels on recovery patterns of the different plant growth forms as well as soil thaw depth. Plant community composition was altered on the trails by species-specific responses to initial disturbance and subsequent changes in substrate. Long-term changes included increased cover of graminoids and decreased cover of evergreen shrubs and mosses. Trails with low levels of initial disturbance usually improved well over time, whereas those with medium to high levels of initial disturbance recovered slowly. Trails on ice-poor, gravel substrates of riparian areas recovered better than those on ice-rich loamy soils of the uplands, even after severe initial damage. Recovery to pre-disturbance communities was not possible where trail subsidence occurred due to thawing of ground ice. Previous studies of

  7. Using Intact Iron Microbial Mats to Gain Insights Into Mat Ecology and Geochemical Niche at the Microbial Scale

    NASA Astrophysics Data System (ADS)

    Glazer, B. T.; Chan, C. S. Y.; Mcallister, S.; Leavitt, A.; Emerson, D.

    2015-12-01

    Microbial mats are formed by microorganisms working in coordinated symbiosis, often benefitting the community by controlling the local geochemical or physical environment. Thus, the ecology of the mat depends on the individual roles of microbes organized into niches within a larger architecture. Chemolithotrophic Fe-oxidizing bacteria (FeOB) form distinctive Fe oxyhydroxide biominerals which constitute the building blocks of the mat. However, the majority of our progress has been in understanding the overall community structure. Understanding the physical mat structure on the microbial scale is important to unraveling FeOB evolution, the biogeochemistry and ecology of Fe-rich habitats, and ultimately interpreting FeOB biosignatures in the rock record. Mats in freshwater and marine environments contain strikingly similar biomineral morphologies, yet they are formed by phylogenetically distinct microorganisms. This suggests that the overall architecture and underlying genetics of freshwater and marine mats has evolved to serve particular roles specific to Fe oxidation. Thus, we conducted a comparative study of Fe seep freshwater mats and marine hydrothermal mats. We have developed a new approach to sampling Fe mats in order to preserve the delicate structure for analysis by confocal and scanning electron microscopy. Our analyses of these intact mats show that freshwater and marine mats are similarly initiated by a single type of structure-former. These ecosystem engineers form either a hollow sheath or a twisted stalk biomineral during mat formation, with a highly directional structure. These microbes appear to be the vanguard organisms that anchor the community within oxygen/Fe(II) gradients, further allowing for community succession in the mat interior as evidenced by other mineralized morphologies. Patterns in biomineral thickness and directionality were indicative of redox gradients and temporal changes in the geochemical environment. These observations show that

  8. Manganese Influences Carbonate Precipitation in a Laminated Microbial Mat

    NASA Astrophysics Data System (ADS)

    Krusor, M.; Grim, S. L.; Wilmeth, D.; Johnson, H.; Berelson, W.; Stevenson, B. S.; Stamps, B. W.; Corsetti, F. A.; Spear, J. R.

    2015-12-01

    Investigating mineralization within modern microbial mats informs our interpretation of ancient microbialites and the mineralization process. Microbial mats in Little Hot Creek (LHC), California contain 4 distinct layers with different microbiota. Each layer of the mat is supersaturated with regard to calcium carbonate (CaCO3), which increases with depth. Total organic carbon decreases with depth through the mat. We used 13C-labeled bicarbonate incubations of each mat layer to calculate growth rates of organic carbon and CaCO3 within the mat. Incubations were also amended with Mn or Mg to test their effect on rates of CaCO3 and organic carbon formation. The Mn-amended top layer increased CaCO3 precipitation and organic carbon growth. Mn increased organic carbon production in the lowest layer to a lesser extent, but not growth of CaCO3. Mn addition had no effect on growth rates in the two intervening layers. Mg amendment stimulated only organic carbon formation in the top layer, with little to no effect on the lower layers or overall CaCO3 formation. We attribute the elevated CaCO3 precipitation noted after Mn addition to increased oxygenic photosynthetic activity. Oxygenic photosynthesis requires Mn as an enzyme cofactor and promotes carbonate precipitation. We propose that the phototrophic community was responsible for most of the CaCO3 precipitation in the upper layer. Phototrophs gradually moved upwards for optimal access to sunlight, and as the mat grew, "tenant" microorganisms inhabited the lower carbonate layers while the "builders" remained on top. The relatively constant percentages of inorganic carbon below the top layer combined with observed minimal CaCO3 precipitation under laboratory conditions suggest that additional research into potential metabolisms that impact carbonate formation would be informative. These results improve our understanding of the linkages between microbial metabolisms, carbonate precipitation in microbial mats, and the potential

  9. Monitoring Survival and Preservation of Recent Cyanobacterial Mats

    NASA Astrophysics Data System (ADS)

    Chacon, Elizabeth; Negron-Mendoza, Alicia; Camargo, Claudia

    2010-05-01

    Through geobiological evolution cyanobacterial mats have played a fundamental role through the development of early microbial carbonate ecosystems and through the sustainment of major biogeochemical cycling in the biosphere; nonetheless their sedimentary record is relatively modest in comparison with their biological impact; this apparent under-representation in the fossil record may be due to their intrinsic poor preservation potential but also to our inability to recognize some subtle microbial signatures. Modern studies on cyanobacterial mats involve high-tech molecular approaches to identify, analyze and even quantify the genetic diversity of ancient and modern microbial mats, yet the physical changes of mats, their survival and preservation potential, remain almost unknown and experimentally poorly explored. If we are going to succeed in the astrobiological quest for traces of life we should develop integrated methods and diagnostic features to address biosignatures at both, the phenotypic and genotypic levels when possible. The correct recognition and interpretation of biosignatures in this emerging field needs, aside these fine molecular tools, plain experimental approaches to test microbial resistance, survival and preservation potential of microbial mats after exposure to diagenetic changes. In this work we study some effects on fresh slices of cyanobacterial mats and cultures of specific external simulated agents that normally occur during diagenesis such as dehydratation, heat, abrasion or pressure among others. Samples from different cyanobacterial communities associated to carbonates collected from different rivers and falls around Mexico were subjected to same lab procedures. Physical and textural changes were monitored through microscopic analysis where cell integrity and mat cohesiveness were analyzed before and after treatment. Preliminary results show that mats enriched in halite and clay sediments were preferentially preserved; however those mats

  10. Water flow and solute transport in floating fen root mats

    NASA Astrophysics Data System (ADS)

    Stofberg, Sija F.; EATM van der Zee, Sjoerd

    2015-04-01

    Floating fens are valuable wetlands, found in North-Western Europe, that are formed by floating root mats when old turf ponds are colonized by plants. These terrestrialization ecosystems are known for their biodiversity and the presence of rare plant species, and the root mats reveal different vegetation zones at a small scale. The vegetation zones are a result of strong gradients in abiotic conditions, including groundwater dynamics, nutrients and pH. To prevent irreversible drought effects such as land subsidence and mineralization of peat, water management involves import of water from elsewhere to maintain constant surface water levels. Imported water may have elevated levels of salinity during dry summers, and salt exposure may threaten the vegetation. To assess the risk of exposure of the rare plant species to salinity, the hydrology of such root mats must be understood. Physical properties of root mats have scarcely been investigated. We have measured soil characteristics, hydraulic conductivity, vertical root mat movement and groundwater dynamics in a floating root mat in the nature reserve Nieuwkoopse Plassen, in the Netherlands. The root mat mostly consists of roots and organic material, in which the soil has a high saturated water content, and strongly varies in its stage of decomposition. We have found a distinct negative correlation between degree of decomposition and hydraulic conductivity, similar to observations for bogs in the literature. Our results show that the relatively young, thin edge of the root mat that colonizes the surface water has a high hydraulic conductivity and floats in the surface water, resulting in very small groundwater fluctuations within the root mat. The older part of the root mat, that is connected to the deeper peat layers is hydrologically more isolated and the material has a lower conductivity. Here, the groundwater fluctuates strongly with atmospheric forcing. The zones of hydraulic properties and vegetation, appear to

  11. Electrospun graphene-ZnO nanofiber mats for photocatalysis applications

    NASA Astrophysics Data System (ADS)

    An, Seongpil; Joshi, Bhavana N.; Lee, Min Wook; Kim, Na Young; Yoon, Sam S.

    2014-03-01

    Graphene-decorated zinc oxide (G-ZnO) nanofibers were fabricated, for the first time, by electrospinning. The effect of graphene concentration on the properties of G-ZnO mats were investigated by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and thermo gravimetric analysis. The G-ZnO mats decorated with 0.5 wt.% of graphene showed excellent photocatalytic activity through degradation of methylene blue under UV irradiation. The highest photocatalytic activity (80% degradation) was observed for 0.5 wt.% G-ZnO mats annealed at 400 °C after 4 h of UV irradiation.

  12. Protocyanobacteria: Oxygenic and Anoxygenic photosynthesis in mat-forming bacteria

    NASA Technical Reports Server (NTRS)

    Cohen, Y.

    1985-01-01

    The oldest record of life is preserved in prePhanerozoic stromatolites dated 3500 million years old and is most likely of filamentous mat-forming cyanobacteria. The sedimentary records of cyanobacterial mats in stromatolites are the most abundant record of life throughout the prePhanerozoic. Stromatolites persisted into the Phanerozoic Eon, yet they become much less pronounced relative to earlier ones. The abundance and persistence of cyanobacterial mats throughout most of geological time point to the evolutionary success of these kinds of microbial communities and their possible role in the evolution of the earth and atmosphere.

  13. Morphology and properties of the soils of permafrost peatlands in the southeast of the Bol'shezemel'skaya tundra

    NASA Astrophysics Data System (ADS)

    Kaverin, D. A.; Pastukhov, A. V.; Lapteva, E. M.; Biasi, C.; Marushchak, M.; Martikainen, P.

    2016-05-01

    The morphology and properties of the soils of permafrost peatlands in the southeast of the Bol'shezemel'skaya tundra are characterized. The soils developing in the areas of barren peat circles differ from oligotrophic permafrost-affected peat soils (Cryic Histosols) of vegetated peat mounds in a number of morphological and physicochemical parameters. The soils of barren circles are characterized by the wellstructured surface horizons, relatively low exchangeable acidity, and higher rates of decomposition and humification of organic matter. It is shown that the development of barren peat circles on tops of peat mounds is favored by the activation of erosional and cryogenic processes in the topsoil. The role of winter wind erosion in the destruction of the upper peat and litter horizons is demonstrated. A comparative analysis of the temperature regime of soils of vegetated peat mounds and barren peat circles is presented. The soil-geocryological complex of peat mounds is a system consisting of three major layers: seasonally thawing layer-upper permafrost-underlying permafrost. The upper permafrost horizons of peat mounds at the depth of 50-90 cm are morphologically similar to the underlying permafrost. However, these layers differ in their physicochemical properties, especially in the composition and properties of their organic matter.

  14. Fabrication and Formation Mechanism of Ag Nanoplate-Decorated Nanofiber Mats and Their Application in SERS.

    PubMed

    Jia, Peng; Chang, Jiao; Wang, Jianqiang; Zhang, Pan; Cao, Bing; Geng, Yuting; Wang, Xiuxing; Pan, Kai

    2016-01-01

    We report a new simple method to fabricate a highly active SERS substrate consisting of poly-m-phenylenediamine/polyacrylonitrile (PmPD/PAN) decorated with Ag nanoplates. The formation mechanism of Ag nanoplates is investigated. The synthetic process of the Ag nanoplate-decorated PmPD/PAN (Ag nanoplates@PmPD/PAN) nanofiber mats consists of the assembly of Ag nanoparticles on the surface of PmPD/PAN nanofibers as crystal nuclei followed by in situ growth of Ag nanoparticles exclusively into nanoplates. Both the reducibility of the polymer and the concentration of AgNO3 are found to play important roles in the formation and the density of Ag nanoplates. The optimized Ag nanoplates@PmPD/PAN nanofiber mats exhibit excellent activity and reproducibility in surface-enhanced Raman scattering (SERS) detection of 4-mercaptobenzoic acid (4-MBA) with a detection limit of 10(-10)  m, making the Ag nanoplates@PmPD/PAN nanofiber mats a promising substrate for SERS detection of chemical molecules. In addition, this work also provides a design and fabrication process for a 3D SERS substrate made of a reducible polymer with noble metals. PMID:26395245

  15. Tracking the Effect of Algal Mats on Coral Bleaching Using Remote Sensing

    NASA Astrophysics Data System (ADS)

    El-Askary, H. M.; Johnson, S. H.; Idris, N.; Qurban, M. A. B.

    2014-12-01

    Benthic habitats rely on relatively stable environmental conditions for survival. The introduction of algal mats into an ecosystem can have a notable effect on the livelihood of organisms such as coral reefs by causing changes in the biogeochemistry of the surrounding water. Increasing levels of acidity and new competition for sunlight caused by congregations of cyanobacteria essentially starve coral reefs of natural resources. These changes are particularly prevalent in waters near quickly developing population centers, such as the ecologically diverse Arabian Gulf. While ground-truthing studies to determine the extensiveness of coral death proves useful on a microcosmic level, new ventures in remote sensing research allow scientists to utilize satellite data to track these changes on a broader scale. Satellite images acquired from Landsat 5, 1987, Landsat 7, 2000, and Landsat 8, 2013 along with higher resolution IKONOS data are digitally analyzed in order to create spectral libraries for relevant benthic types, which in turn can be used to perform supervised classifications and change detection analyses over a larger area. The supervised classifications performed over the three scenes show five significant marine-related classes, namely coral, mangroves, macro-algae, and seagrass, in different degrees of abundance, yet here we focus only on the algal mats impact on corals bleaching. The change detection analysis is introduced to study see the degree of algal mats impact on coral bleaching over the course of time with possible connection to the local meteorology and current climate scenarios.

  16. The modeled effects of fire on carbon balance and vegetation abundance in Alaskan tundra

    NASA Astrophysics Data System (ADS)

    Dietze, M. C.; Davidson, C. D.; Kelly, R.; Higuera, P. E.; Hu, F.

    2012-12-01

    Arctic climate is warming at a rate disproportionately faster than the rest of the world. Changes have been observed within the tundra that are attributed to this trend, including active layer thickening, shrub land expansion, and increases in fire frequency. Whether tundra remains a global net sink of carbon could depend upon the effects of fire on vegetation, specifically concerning the speed at which vegetation reestablishes, the stimulation of growth after fire, and the changes that occur in species composition during succession. While rapid regeneration of graminoid vegetation favors the spread of this functional type in early succession, late succession appears to favor shrub vegetation at abundances greater than those observed before fire. Possible reasons for this latter observation include changes in albedo, soil insulation, and soil moisture regimes. Here we investigate the course of succession after fire disturbance within tundra ecosystems, and the mechanisms involved. A series of simulated burn experiments were conducted on the burn site left by the 2007 Anaktuvuk River fire to access the behavior of the Ecosystem Demography model v2.2 (ED2) in the simulation of fire on the tundra. The land surface sub-model within ED is modified to improve simulate permafrost through the effects of an increased soil-column depth, a peat texture class, and the effects of wind compaction and depth hoar on snow density. Parameterization is conducted through Bayesian techniques used to constrain parameter distributions based upon data from a literature survey, field measurements at Toolik Lake, Alaska, and a data assimilation over three datasets. At each step, priority was assigned to measurements that could constrain parameters that account for the greatest explained variance in model output as determined through sensitivity analysis. Following parameterization, a series of simulations were performed to gauge the suitability of the model in predicting carbon balance and

  17. Alaska tundra vegetation trends and their links to the large-scale climate

    NASA Astrophysics Data System (ADS)

    Bieniek, P. A.; Bhatt, U. S.; Walker, D. A.; Raynolds, M. K.; Comiso, J. C.

    2011-12-01

    The arctic Normalized Vegetation Index (NDVI) data set (a measure of vegetation photosynthetic capacity) has been used to document coherent temporal relationships between near-coastal sea ice, summer tundra land surface temperatures, and vegetation productivity throughout the Arctic (Bhatt et al. 2010). Land warming over North America has displayed larger trends (+30%) when compared to Eurasia (+16%) since 1982. In the tundra of northern Alaska the greatest change was found in absolute maximum NDVI along the Beaufort Sea coast (+14%). In contrast, tundra areas in southwest Alaska along the Bering Sea have seen a decline (-4%). Greenup date in these regions has been occurring as much as 1-4 days earlier per decade, but trends are mixed. Winter snow water equivalent (SWE) has only increased slightly (+0.1 mm/yr) in the Arctic region of Alaska since 1987 (R. Muskett, personal communication). These findings suggest that there have been changes in the seasonal climate in Alaska during the NDVI record. The tundra trends are further investigated by evaluating remotely sensed sea ice, surface air temperature, SWE, daily snow cover, and NDVI3g. While the snow data has a relatively short record (1999-2010), notable trends can be observed in snow melt, occurring as much 15 days earlier per decade in northern Alaska. Unfortunately, other snow data sets have been found to be problematic and could not be used to extend our analysis. This highlights the need for a long-term pan-arctic snow data set that is suitable for climate analysis. Possible climate drivers are also investigated. Results show that the summer tundra, in terms of NDVI and summer warmth index (SWI), has few direct links with the large-scale climate. However, the sea ice concentration along the coast of the tundra regions has strong preseason links to the large-scale climate. This suggests that the large-scale climate influences the sea ice concentration which then affects the NDVI and SWI. Three tundra regions

  18. InSAR detects increase in surface subsidence caused by an Arctic tundra fire

    USGS Publications Warehouse

    Liu, Lin; Jafarov, Elchin E.; Schaefer, Kevin M.; Jones, Benjamin M.; Zebker, Howard A.; Williams, Christopher A.; Rogan, John; Zhang, Tingjun

    2014-01-01

    Wildfire is a major disturbance in the Arctic tundra and boreal forests, having a significant impact on soil hydrology, carbon cycling, and permafrost dynamics. This study explores the use of the microwave Interferometric Synthetic Aperture Radar (InSAR) technique to map and quantify ground surface subsidence caused by the Anaktuvuk River fire on the North Slope of Alaska. We detected an increase of up to 8 cm of thaw-season ground subsidence after the fire, which is due to a combination of thickened active layer and permafrost thaw subsidence. Our results illustrate the effectiveness and potential of using InSAR to quantify fire impacts on the Arctic tundra, especially in regions underlain by ice-rich permafrost. Our study also suggests that surface subsidence is a more comprehensive indicator of fire impacts on ice-rich permafrost terrain than changes in active layer thickness alone.

  19. Species differences in whole plant carbon balance following winter dormancy in Alaskan tundra plants

    SciTech Connect

    Bret-Harte, M.S.; Chapin, F.S. III

    1995-09-01

    We froze ramets of seven vascular plant species and a mixed community of mosses common to upland tussock tundra for several months, then measured whole-plant photosynthesis and respiration in a growth chamber under simulated spring conditions, to examine whole plant carbon metabolism following winter dormancy. In addition, respiration and photosynthesis of aboveground stems and leaves were measured in the field in a spatial gradient away from a melting snowbank, at comparable developmental stages. Species differences in early respiration were not pronounced, but large differences were seen once development of leaves began. Root development in deciduous shrubs delayed their attainment of a positive whole plant carbon balance compared to that seen in aboveground stems and leaves alone, and partially compensated for differences in photosynthetic rates between shrubs and other species. Temporal patterns of carbon metabolism during spring growth may affect competitive balance in tussock tundra and vegetation response to global change.

  20. Sequencing and analysis of the complete mitochondrial genome of tundra shrew (Sorex tundrensis) from China.

    PubMed

    Xu, Chunzhu; Zhao, Shuai; Wu, Hualin; Wu, Shengyang; Zhang, Zhongwen; Wang, Bo; Dou, Huashan

    2016-07-01

    The complete mitogenome sequence of tundra shrew (Sorex tundrensis) was determined using long PCR. The genome was 17,444 bp in length and contained 13 protein-coding genes, 2 ribosomal RNA genes, 23 transfer RNA genes, 1 origin of L strand replication and 1 control region. The overall base composition of the heavy strand is A (32.9%), C (24.8%), T (29.0%), and G (13.3%). The base compositions present clearly the A-T skew, which is most obviously in the control region and protein-coding genes. The extended termination-associated sequence domain, the central conserved domain and the conserved sequence block domain are defined in the mitochondrial genome control region of tundra shrew. Mitochondrial genome analyses based on MP, ML, NJ and Bayesian analyses yielded identical phylogenetic trees. The three Sorex species formed a monophyletic group with the high bootstrap value (100 %) in all examinations. PMID:25812054

  1. AmeriFlux US-ICh Imnavait Creek Watershed Heath Tundra

    DOE Data Explorer

    Bret-Harte, Syndonia [University of Alaska Fairbanks; Euskirchen, Eugenie [University of Alaska Fairbanks; Shaver, Gaius [Marine Biological Laboratory

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-ICh Imnavait Creek Watershed Heath Tundra. Site Description - The Imnavait Creek Watershed Heath Tundra (Ridge Station) is located near Imnavait Creek in Alaska, north of the Brooks Range in the Kuparuk basin near Lake Toolik and the Toolik Field Station. The Kuparuk River has its headwaters in the Brooks Range and drains through northern Alaska into the Arctic Ocean. Within these headwaters lies the Imnavait basin at an average elevation of 930 m. Water tracks run down the hill in parallel zones with a spacing of approximately 10 m. The Ridge Station was deployed at the end of Summer 2007.

  2. AmeriFlux US-ICs Imnavait Creek Watershed Wet Sedge Tundra

    DOE Data Explorer

    Bret-Harte, Syndonia [University of Alaska Fairbanks; Euskirchen, Eugenie [University of Alaska Fairbanks; Shaver, Gaius [Marine Biological Laboratory

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-ICs Imnavait Creek Watershed Wet Sedge Tundra. Site Description - The Imnavait Creek Watershed Wet Sedge Tundra (Fen Station) is located near Imnavait Creek in Alaska, north of the Brooks Range in the Kuparuk basin near Lake Toolik and the Toolik Field Station. The Kuparuk River has its headwaters in the Brooks Range and drains through northern Alaska into the Arctic Ocean. Within these headwaters lies the Imnavait basin at an average elevation of 930 m. Water tracks run down the hill in parallel zones with a spacing of approximately 10 m. The Fen Station was deployed at the end of Summer 2007.

  3. AmeriFlux US-ICt Imnavait Creek Watershed Tussock Tundra

    DOE Data Explorer

    Bret-Harte, Syndonia [University of Alaska Fairbanks; Euskirchen, Eugenie [University of Alaska Fairbanks; Shaver, Gaius [Marine Biological Laboratory

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-ICt Imnavait Creek Watershed Tussock Tundra. Site Description - The Imnavait Creek Watershed Tussock Tundra (Biocomplexity Station) is located near Imnavait Creek in Alaska, north of the Brooks Range in the Kuparuk basin near Lake Toolik and the Toolik Field Station. The Kuparuk River has its headwaters in the Brooks Range and drains through northern Alaska into the Arctic Ocean. Within these headwaters lies the Imnavait basin at an average elevation of 930 m. Water tracks run down the hill in parallel zones with a spacing of approximately 10 m. The Biocomplexity Station was deployed in 2004, and it has been in operation during the melt seasons ever since.

  4. InSAR detects increase in surface subsidence caused by an Arctic tundra fire

    NASA Astrophysics Data System (ADS)

    Liu, Lin; Jafarov, Elchin E.; Schaefer, Kevin M.; Jones, Benjamin M.; Zebker, Howard A.; Williams, Christopher A.; Rogan, John; Zhang, Tingjun

    2014-06-01

    Wildfire is a major disturbance in the Arctic tundra and boreal forests, having a significant impact on soil hydrology, carbon cycling, and permafrost dynamics. This study explores the use of the microwave Interferometric Synthetic Aperture Radar (InSAR) technique to map and quantify ground surface subsidence caused by the Anaktuvuk River fire on the North Slope of Alaska. We detected an increase of up to 8 cm of thaw-season ground subsidence after the fire, which is due to a combination of thickened active layer and permafrost thaw subsidence. Our results illustrate the effectiveness and potential of using InSAR to quantify fire impacts on the Arctic tundra, especially in regions underlain by ice-rich permafrost. Our study also suggests that surface subsidence is a more comprehensive indicator of fire impacts on ice-rich permafrost terrain than changes in active layer thickness alone.

  5. Psychrotolerant actinomycetes of plants and organic horizons in tundra and taiga soils

    NASA Astrophysics Data System (ADS)

    Dubrova, M. S.; Zenova, G. M.; Yakushev, A. V.; Manucharova, N. A.; Makarova, E. P.; Zvyagintsev, D. G.; Chernov, I. Yu.

    2013-08-01

    It has been revealed that in organic horizons and plants of the tundra and taiga ecosystems under low temperatures, actinomycetal complexes form. The population density of psychrotolerant actinomycetes in organic horizons and plants reaches tens and hundreds of thousands CFU/g of substrate or soil, and decreases in the sequence litters > plants > soils > undecomposed plant remains > moss growths. The mycelium length of psychrotolerant actinomycetes reaches 220 m/g of substrate. Application of the FISH method has demonstrated that metabolically active psychrotolerant bacteria of the phylum Actinobacteria constitute 30% of all metabolically active psychrotolerant representatives of the Bacterià domain of the prokaryotic microbial community of soils and plants. Psychrotolerant actinomycetes in tundra and taiga ecosystems possess antimicrobial properties.

  6. Microbial Diversity in Sediment Ecosystems (Evaporites Domes, Microbial Mats, and Crusts) of Hypersaline Laguna Tebenquiche, Salar de Atacama, Chile.

    PubMed

    Fernandez, Ana B; Rasuk, Maria C; Visscher, Pieter T; Contreras, Manuel; Novoa, Fernando; Poire, Daniel G; Patterson, Molly M; Ventosa, Antonio; Farias, Maria E

    2016-01-01

    We combined nucleic acid-based molecular methods, biogeochemical measurements, and physicochemical characteristics to investigate microbial sedimentary ecosystems of Laguna Tebenquiche, Atacama Desert, Chile. Molecular diversity, and biogeochemistry of hypersaline microbial mats, rhizome-associated concretions, and an endoevaporite were compared with: The V4 hypervariable region of the 16S rRNA gene was amplified by pyrosequencing to analyze the total microbial diversity (i.e., bacteria and archaea) in bulk samples, and in addition, in detail on a millimeter scale in one microbial mat and in one evaporite. Archaea were more abundant than bacteria. Euryarchaeota was one of the most abundant phyla in all samples, and particularly dominant (97% of total diversity) in the most lithified ecosystem, the evaporite. Most of the euryarchaeal OTUs could be assigned to the class Halobacteria or anaerobic and methanogenic archaea. Planctomycetes potentially also play a key role in mats and rhizome-associated concretions, notably the aerobic organoheterotroph members of the class Phycisphaerae. In addition to cyanobacteria, members of Chromatiales and possibly the candidate family Chlorotrichaceae contributed to photosynthetic carbon fixation. Other abundant uncultured taxa such as the candidate division MSBL1, the uncultured MBGB, and the phylum Acetothermia potentially play an important metabolic role in these ecosystems. Lithifying microbial mats contained calcium carbonate precipitates, whereas endoevoporites consisted of gypsum, and halite. Biogeochemical measurements revealed that based on depth profiles of O2 and sulfide, metabolic activities were much higher in the non-lithifying mat (peaking in the least lithified systems) than in lithifying mats with the lowest activity in endoevaporites. This trend in decreasing microbial activity reflects the increase in salinity, which may play an important role in the biodiversity. PMID:27597845

  7. Microbial Diversity in Sediment Ecosystems (Evaporites Domes, Microbial Mats, and Crusts) of Hypersaline Laguna Tebenquiche, Salar de Atacama, Chile

    PubMed Central

    Fernandez, Ana B.; Rasuk, Maria C.; Visscher, Pieter T.; Contreras, Manuel; Novoa, Fernando; Poire, Daniel G.; Patterson, Molly M.; Ventosa, Antonio; Farias, Maria E.

    2016-01-01

    We combined nucleic acid-based molecular methods, biogeochemical measurements, and physicochemical characteristics to investigate microbial sedimentary ecosystems of Laguna Tebenquiche, Atacama Desert, Chile. Molecular diversity, and biogeochemistry of hypersaline microbial mats, rhizome-associated concretions, and an endoevaporite were compared with: The V4 hypervariable region of the 16S rRNA gene was amplified by pyrosequencing to analyze the total microbial diversity (i.e., bacteria and archaea) in bulk samples, and in addition, in detail on a millimeter scale in one microbial mat and in one evaporite. Archaea were more abundant than bacteria. Euryarchaeota was one of the most abundant phyla in all samples, and particularly dominant (97% of total diversity) in the most lithified ecosystem, the evaporite. Most of the euryarchaeal OTUs could be assigned to the class Halobacteria or anaerobic and methanogenic archaea. Planctomycetes potentially also play a key role in mats and rhizome-associated concretions, notably the aerobic organoheterotroph members of the class Phycisphaerae. In addition to cyanobacteria, members of Chromatiales and possibly the candidate family Chlorotrichaceae contributed to photosynthetic carbon fixation. Other abundant uncultured taxa such as the candidate division MSBL1, the uncultured MBGB, and the phylum Acetothermia potentially play an important metabolic role in these ecosystems. Lithifying microbial mats contained calcium carbonate precipitates, whereas endoevoporites consisted of gypsum, and halite. Biogeochemical measurements revealed that based on depth profiles of O2 and sulfide, metabolic activities were much higher in the non-lithifying mat (peaking in the least lithified systems) than in lithifying mats with the lowest activity in endoevaporites. This trend in decreasing microbial activity reflects the increase in salinity, which may play an important role in the biodiversity. PMID:27597845

  8. Herbivore Impact on Tundra Plant Community Dynamics Using Long-term Remote Sensing Observation

    NASA Astrophysics Data System (ADS)

    Yu, Q.; Engstrom, R.; Shiklomanov, N. I.

    2014-12-01

    Arctic tundra biome is now experiencing dramatic environmental changes accentuated by summer sea-ice decline, permafrost thaw, and shrub expansion. Multi-decadal time-series of the Normalized Difference Vegetation Index (NDVI, a spectral metric of vegetation productivity) shows an overall "greening" trend across the Arctic tundra biome. Regional trends in climate plausibly explain large-scale patterns of increasing plant productivity, as diminished summer sea-ice extent warms the adjacent land causing tundra vegetation to respond positively (increased photosynthetic aboveground biomass). However, at more local scales, there is a great deal of spatial variability in NDVI trends that likely reflects differences in hydrology and soil conditions, disturbance history, and use by wildlife and humans. Particularly, habitat use by large herbivores, such as reindeer and caribou, has large impacts on vegetation dynamics at local and regional scales, but the role of herbivores in modulating the response of vegetation to warming climate has received little attention. This study investigates regional tundra plant community dynamics within inhabits of different sizes of wild caribou/reindeer herds across the Arctic using GIMMS NDVI (Normalized Difference Vegetation Index) 3g data product. The Taimyr herd in Russia is one of the largest herds in the world with a population increase from 450,000 in 1975 to about 1 million animals in 2000. The population of the porcupine caribou herd has fluctuated in the past three decades between 100,000 and 180,000. Time-series of the maximum NDVI within the inhabit area of the Taimyr herd has increased about 2% per decade over the past three decades, while within the inhabit area of the Porcupine herd the maximum NDVI has increased about 5% per decade. Our results indicate that the impact of large herbivores can be detected from space and further analyses on seasonal dynamics of vegetation indices and herbivore behavior may provide more

  9. Estimated storage of amorphous silica in soils of the circum-Arctic tundra region

    NASA Astrophysics Data System (ADS)

    Alfredsson, H.; Clymans, W.; Hugelius, G.; Kuhry, P.; Conley, D. J.

    2016-03-01

    We investigated the vertical distribution, storage, landscape partitioning, and spatial variability of soil amorphous silica (ASi) at four different sites underlain by continuous permafrost and representative of mountainous and lowland tundra, in the circum-Arctic region. Based on a larger set of data, we present the first estimate of the ASi soil reservoir (0-1 m depth) in circum-Arctic tundra terrain. At all sites, the vertical distribution of ASi concentrations followed the pattern of either (1) declining concentrations with depth (most common) or (2) increasing/maximum concentrations with depth. Our results suggest that a set of processes, including biological control, solifluction and other slope processes, cryoturbation, and formation of inorganic precipitates influence vertical distributions of ASi in permafrost terrain, with the capacity to retain stored ASi on millennial timescales. At the four study sites, areal ASi storage (0-1 m) is generally higher in graminoid tundra compared to wetlands. Our circum-Arctic upscaling estimates, based on both vegetation and soil classification separately, suggest a storage amounting to 219 ± 28 and 274 ± 33 Tmol Si, respectively, of which at least 30% is stored in permafrost. This estimate would account for about 3% of the global soil ASi storage while occupying an equal portion of the global land area. This result does not support the hypothesis that the circum-Arctic tundra soil ASi reservoir contains relatively higher amounts of ASi than other biomes globally as demonstrated for carbon. Nevertheless, climate warming has the potential to significantly alter ASi storage and terrestrial Si cycling in the Arctic.

  10. Blood lead concentrations in Alaskan tundra swans: linking breeding and wintering areas with satellite telemetry

    USGS Publications Warehouse

    Ely, Craig R.; Franson, Christian

    2014-01-01

    Tundra swans (Cygnus columbianus) like many waterfowl species are susceptible to lead (Pb) poisoning, and Pb-induced mortality has been reported from many areas of their wintering range. Little is known however about Pb levels throughout the annual cycle of tundra swans, especially during summer when birds are on remote northern breeding areas where they are less likely to be exposed to anthropogenic sources of Pb. Our objective was to document summer Pb levels in tundra swans throughout their breeding range in Alaska to determine if there were population-specific differences in blood Pb concentrations that might pose a threat to swans and to humans that may consume them. We measured blood Pb concentrations in tundra swans at five locations in Alaska, representing birds that winter in both the Pacific Flyway and Atlantic Flyway. We also marked swans at each location with satellite transmitters and coded neck bands, to identify staging and wintering sites and determine if winter site use correlated with summer Pb concentrations. Blood Pb levels were generally low (<0.2 μg/ml) in swans across all breeding areas. Pb levels were lower in cygnets than adults, suggesting that swans were likely exposed to Pb on wintering areas or on return migration to Alaska, rather than on the summer breeding grounds. Blood Pb levels varied significantly across the five breeding areas, with highest concentrations in birds on the North Slope of Alaska (wintering in the Atlantic Flyway), and lowest in birds from the lower Alaska Peninsula that rarely migrate south for winter.

  11. CO2 flux from tundra lichen, moss, and tussock, Council, Alaska: Assessment of spatial representativeness

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Chae, N.

    2012-12-01

    CO2 flux-measurement in dominant tundra vegetation on the Seward Peninsula of Alaska was examined for spatial representativeness, using a manual chamber system. In order to assess the representativeness of CO2 flux, a 40 m × 40 m (5-m interval; 81 total points) plot was used in June, August, and September of 2011. Average CO2 fluxes in lichen, moss, and tussock tundra were 3.4 ± 2.7, 4.5 ± 2.9, and 7.2 ± 5.7 mgCO2/m2/m during growing season, respectively, suggesting that tussock tundra is a significant CO2 source, especially considering the wide distribution of tussock tundra in the circumpolar region. Further, soil temperature, rather than soil moisture, held the key role in regulating CO2 flux at the study site: CO2 flux from tussock increased linearly as soil temperature increased, while the flux from lichen and moss followed soil temperature nearly exponentially, reflecting differences in surface area covered by the chamber system. Regarding sample size, the 81 total sampling points over June, August, and September satisfy an experimental average that falls within ±10% of full sample average, with a 95% confidence level. However, the number of sampling points for each variety of vegetation during each month must provide at least ±20%, with an 80% confidence level. In order to overcome the logistical constraints, we were required to identify the site's characteristics with a manual chamber system over a 40 m × 40 m plot and to subsequently employ an automated chamber for spatiotemporal representativeness.

  12. Long-term persistence of spent lead shot in tundra wetlands

    USGS Publications Warehouse

    Flint, Paul L.; Schamber, Jason L.

    2010-01-01

    We seeded experimental plots with number 4 lead pellets and sampled these plots for 10 years to assess the settlement rate of pellets in tundra wetland types commonly used by foraging waterfowl. After 10 years, about 10% of pellets remained within 6 cm of the surface, but >50% remained within 10 cm. We predict that spent lead pellets will eventually become unavailable to waterfowl; however, it will likely require >25 years for all pellets to exceed depths at which waterfowl species may forage.

  13. The cyanobacterium Mastigocladus fulfills the nitrogen demand of a terrestrial hot spring microbial mat.

    PubMed

    Estrella Alcamán, María; Fernandez, Camila; Delgado, Antonio; Bergman, Birgitta; Díez, Beatriz

    2015-10-01

    Cyanobacteria from Subsection V (Stigonematales) are important components of microbial mats in non-acidic terrestrial hot springs. Despite their diazotrophic nature (N2 fixers), their impact on the nitrogen cycle in such extreme ecosystems remains unknown. Here, we surveyed the identity and activity of diazotrophic cyanobacteria in the neutral hot spring of Porcelana (Northern Patagonia, Chile) during 2009 and 2011-2013. We used 16S rRNA and the nifH gene to analyze the distribution and diversity of diazotrophic cyanobacteria. Our results demonstrate the dominance of the heterocystous genus Mastigocladus (Stigonematales) along the entire temperature gradient of the hot spring (69-38 °C). In situ nitrogenase activity (acetylene reduction), nitrogen fixation rates (cellular uptake of (15)N2) and nifH transcription levels in the microbial mats showed that nitrogen fixation and nifH mRNA expression were light-dependent. Nitrogen fixation activities were detected at temperatures ranging from 58 °C to 46 °C, with maximum daily rates of 600 nmol C2H4 cm(-2) per day and 94.1 nmol N cm(-2) per day. These activity patterns strongly suggest a heterocystous cyanobacterial origin and reveal a correlation between nitrogenase activity and nifH gene expression during diurnal cycles in thermal microbial mats. N and C fixation in the mats contributed ~3 g N m(-2) per year and 27 g C m(-2) per year, suggesting that these vital demands are fully met by the diazotrophic and photoautotrophic capacities of the cyanobacteria in the Porcelana hot spring. PMID:26230049

  14. BIOGEOCHEMICAL STUDIES OF PHOTOSYNTHETIC MICROBIAL MATS AND THEIR BIOTA

    NASA Technical Reports Server (NTRS)

    DesMarais, David; Discipulo, M.; Turk, K.; Londry, K. L.

    2005-01-01

    Photosynthetic microbial mats offer an opportunity to define holistic functionality at the millimeter scale. At the same time. their biogeochemistry contributes to environmental processes on a planetary scale. These mats are possibly direct descendents of the most ancient biological communities; communities in which oxygenic photosynthesis might have been invented. Mats provide one of the best natural systems to study how microbial populations associate to control dynamic biogeochemical gradients. These are self- sustaining, complete ecosystems in which light energy absorbed over a dial (24 hour) cycle drives the synthesis of spatially-organized, diverse biomass. Tightly-coupled microorganisms in the mat have specialized metabolisms that catalyze transformations of carbon, nitrogen, sulfur, and a host of other elements.

  15. Microbial mats and the early evolution of life

    NASA Technical Reports Server (NTRS)

    Des Marais, D. J.

    1990-01-01

    Microbial mats have descended from perhaps the oldest and most widespread biological communities known. Mats harbor microbes that are crucial for studies of bacterial phylogeny and physiology. They illustrate how several oxygen-sensitive biochemical processes have adapted to oxygen, and they show how life adapted to dry land long before the rise of plants. The search for the earliest grazing protists and metazoa in stromatolites is aided by observations of mats: in them, organic compounds characteristic of ancient photosynthetic protists can be identified. Recent mat studies suggest that the 13C/12C increase observed over geological time in stromatolitic organic matter was driven at least in part by a long-term decline in atmospheric carbon dioxide levels.

  16. A Modular Sensorized Mat for Monitoring Infant Posture

    PubMed Central

    Donati, Marco; Cecchi, Francesca; Bonaccorso, Filippo; Branciforte, Marco; Dario, Paolo; Vitiello, Nicola

    2014-01-01

    We present a novel sensorized mat for monitoring infant's posture through the measure of pressure maps. The pressure-sensitive mat is based on an optoelectronic technology developed in the last few years at Scuola Superiore Sant'Anna: a soft silicone skin cover, which constitutes the mat, participates in the transduction principle and provides the mat with compliance. The device has a modular structure (with a minimum of one and a maximum of six sub-modules, and a total surface area of about 1 m2) that enables dimensional adaptation of the pressure-sensitive area to different specific applications. The system consists of on-board electronics for data collection, pre-elaboration, and transmission to a remote computing unit for analysis and posture classification. In this work we present a complete description of the sensing apparatus along with its experimental characterization and validation with five healthy infants. PMID:24385029

  17. Microbial mats and modern stromatolites in Shark Bay, Western Australia

    NASA Technical Reports Server (NTRS)

    Golubic, S.

    1985-01-01

    Distribution, external morphology, texture, and microbial composition of microbial mats in Hamelin Pool, Shark Bay, Western Australia, have been studied and reviewed along a composite representative profile starting from the permanently submerged zone, across the zones of periodic flooding, toward permanently emerged land and coastal dunes. The following nine types of algal mats have been recognized: colloform, gelatinous, smooth, pincushion, tufted, mamillate, film, reticulate, and blister. Solar ponds represent a particular environment. The mat types represent microbial communities that are characterized by one or more dominant microorganisms. The colonization and stabilization of loose sediment is carried out by a microbial assemblage of generalists that prepare the ground for later replacement and succession by specialized microflora. Lithification of microbial mats takes place periodically, mainly during the austral summer. This process is destructive for the microbial community but increases the preservation potential of the stromatolitic structures.

  18. Remote sensing of vegetation and land-cover change in Arctic Tundra Ecosystems

    USGS Publications Warehouse

    Stow, D.A.; Hope, A.; McGuire, D.; Verbyla, D.; Gamon, J.; Huemmrich, F.; Houston, S.; Racine, C.; Sturm, M.; Tape, K.; Hinzman, L.; Yoshikawa, K.; Tweedie, C.; Noyle, B.; Silapaswan, C.; Douglas, D.; Griffith, B.; Jia, G.; Epstein, H.; Walker, D.; Daeschner, S.; Petersen, A.; Zhou, L.; Myneni, R.

    2004-01-01

    The objective of this paper is to review research conducted over the past decade on the application of multi-temporal remote sensing for monitoring changes of Arctic tundra lands. Emphasis is placed on results from the National Science Foundation Land-Air-Ice Interactions (LAII) program and on optical remote sensing techniques. Case studies demonstrate that ground-level sensors on stationary or moving track platforms and wide-swath imaging sensors on polar orbiting satellites are particularly useful for capturing optical remote sensing data at sufficient frequency to study tundra vegetation dynamics and changes for the cloud prone Arctic. Less frequent imaging with high spatial resolution instruments on aircraft and lower orbiting satellites enable more detailed analyses of land cover change and calibration/validation of coarser resolution observations. The strongest signals of ecosystem change detected thus far appear to correspond to expansion of tundra shrubs and changes in the amount and extent of thaw lakes and ponds. Changes in shrub cover and extent have been documented by modern repeat imaging that matches archived historical aerial photography. NOAA Advanced Very High Resolution Radiometer (AVHRR) time series provide a 20-year record for determining changes in greenness that relates to photosynthetic activity, net primary production, and growing season length. The strong contrast between land materials and surface waters enables changes in lake and pond extent to be readily measured and monitored. ?? 2003 Elsevier Inc. All rights reserved.

  19. Remote sensing of vegetation and land-cover change in Arctic tundra ecosystems

    USGS Publications Warehouse

    Checkstow, D.A.; Hope, A.; McGuire, D.; Verbyla, D.; Gamon, J.; Huemmrich, F.; Houston, S.; Racine, C.; Sturm, M.; Tape, K.; Hinzman, L.; Yoshikawa, K.; Tweedie, C.

    2004-01-01

    The objective of this paper is to review research conducted over the past decade on the application of multi-temporal remote sensing for monitoring changes of Arctic tundra lands. Emphasis is placed on results from the National Science Foundation Land-Air-Ice Interactions (LAII) program and on optical remote sensing techniques. Case studies demonstrate that ground-level sensors on stationary or moving track platforms and wide-swath imaging sensors on polar orbiting satellites are particularly useful for capturing optical remote sensing data at sufficient frequency to study tundra vegetation dynamics and changes for the cloud prone Arctic. Less frequent imaging with high spatial resolution instruments on aircraft and lower orbiting satellites enable more detailed analyses of land cover change and calibration/validation of coarser resolution observations. The strongest signals of ecosystem change detected thus far appear to correspond to expansion of tundra shrubs and changes in the amount and extent of thaw lakes and ponds. Changes in shrub cover and extent have been documented by modern repeat imaging that matches archived historical aerial photography. NOAA Advanced Very High Resolution Radiometer (AVHRR) time series provide a 20-year record for determining changes in greenness that relates to photosynthetic activity, net primary production, and growing season length. The strong contrast between land materials and surface waters enables changes in lake and pond extent to be readily measured and monitored.

  20. Element cycling in the dominant plant community in the Alpine tundra zone of Changbai Mountains, China.

    PubMed

    Liu, Jing-Shuang; Yu, Jun-Bao

    2005-01-01

    Element cycling in the dominant plant communities including Rh. aureum, Rh. redowskianum and Vaccinium uliginosum in the Alpine tundra zone of Changbai Mountains in northeast China was studied. The results indicate that the amount of elements from litter decomposition was less than that of the plant uptake from soil, but that from plant uptake was higher than that in soil with mineralization process released. On the other hand, in the open system including precipitation input and soil leaching output, because of great number of elements from precipitation into the open system, the element cycling(except N, P) in the Alpine tundra ecosystem was in a dynamic balance. In this study, it was also found that different organ of plants had significant difference in accumulating elements. Ca, Mg, P and N were accumulated more obviously in leaves, while Fe was in roots. The degree of concentration of elements in different tissues of the same organ of the plants also was different, a higher concentration of Ca, Mg, P and N in mesophyll than in nerve but Fe was in a reversed order. The phenomenon indicates (1) a variety of biochemical functions of different elements, (2) the elements in mesophyll were with a shorter turnover period than those in nerve or fibre, but higher utilization rate for plant. Therefore, this study implies the significance of keeping element dynamic balance in the alpine tundra ecosystem of Changbai Mountains. PMID:16083139

  1. Mapping wildfire burn severity in the Arctic Tundra from downsampled MODIS data

    USGS Publications Warehouse

    Kolden, Crystal A.; Rogan, John

    2013-01-01

    Wildfires are historically infrequent in the arctic tundra, but are projected to increase with climate warming. Fire effects on tundra ecosystems are poorly understood and difficult to quantify in a remote region where a short growing season severely limits ground data collection. Remote sensing has been widely utilized to characterize wildfire regimes, but primarily from the Landsat sensor, which has limited data acquisition in the Arctic. Here, coarse-resolution remotely sensed data are assessed as a means to quantify wildfire burn severity of the 2007 Anaktuvuk River Fire in Alaska, the largest tundra wildfire ever recorded on Alaska's North Slope. Data from Landsat Thematic Mapper (TM) and downsampled Moderate-resolution Imaging Spectroradiometer (MODIS) were processed to spectral indices and correlated to observed metrics of surface, subsurface, and comprehensive burn severity. Spectral indices were strongly correlated to surface severity (maximum R2 = 0.88) and slightly less strongly correlated to substrate severity. Downsampled MODIS data showed a decrease in severity one year post-fire, corroborating rapid vegetation regeneration observed on the burned site. These results indicate that widely-used spectral indices and downsampled coarse-resolution data provide a reasonable supplement to often-limited ground data collection for analysis and long-term monitoring of wildfire effects in arctic ecosystems.

  2. Tundra soil carbon is vulnerable to rapid microbial decomposition under climate warming

    NASA Astrophysics Data System (ADS)

    Xue, Kai; M. Yuan, Mengting; J. Shi, Zhou; Qin, Yujia; Deng, Ye; Cheng, Lei; Wu, Liyou; He, Zhili; van Nostrand, Joy D.; Bracho, Rosvel; Natali, Susan; Schuur, Edward. A. G.; Luo, Chengwei; Konstantinidis, Konstantinos T.; Wang, Qiong; Cole, James R.; Tiedje, James M.; Luo, Yiqi; Zhou, Jizhong

    2016-06-01

    Microbial decomposition of soil carbon in high-latitude tundra underlain with permafrost is one of the most important, but poorly understood, potential positive feedbacks of greenhouse gas emissions from terrestrial ecosystems into the atmosphere in a warmer world. Using integrated metagenomic technologies, we showed that the microbial functional community structure in the active layer of tundra soil was significantly altered after only 1.5 years of warming, a rapid response demonstrating the high sensitivity of this ecosystem to warming. The abundances of microbial functional genes involved in both aerobic and anaerobic carbon decomposition were also markedly increased by this short-term warming. Consistent with this, ecosystem respiration (Reco) increased up to 38%. In addition, warming enhanced genes involved in nutrient cycling, which very likely contributed to an observed increase (30%) in gross primary productivity (GPP). However, the GPP increase did not offset the extra Reco, resulting in significantly more net carbon loss in warmed plots compared with control plots. Altogether, our results demonstrate the vulnerability of active-layer soil carbon in this permafrost-based tundra ecosystem to climate warming and the importance of microbial communities in mediating such vulnerability.

  3. Sensitivity analysis of a model of CO2 exchange in tundra ecosystems by the adjoint method

    NASA Technical Reports Server (NTRS)

    Waelbroek, C.; Louis, J.-F.

    1995-01-01

    A model of net primary production (NPP), decomposition, and nitrogen cycling in tundra ecosystems has been developed. The adjoint technique is used to study the sensitivity of the computed annual net CO2 flux to perturbation in initial conditions, climatic inputs, and model's main parameters describing current seasonal CO2 exchange in wet sedge tundra at Barrow, Alaska. The results show that net CO2 flux is most sensitive to parameters characterizing litter chemical composition and more sensitive to decomposition parameters than to NPP parameters. This underlines the fact that in nutrient-limited ecosystems, decomposition drives net CO2 exchange by controlling mineralization of main nutrients. The results also indicate that the short-term (1 year) response of wet sedge tundra to CO2-induced warming is a significant increase in CO2 emission, creating a positive feedback to atmosphreic CO2 accumulation. However, a cloudiness increase during the same year can severely alter this response and lead to either a slight decrease or a strong increase in emitted CO2, depending on its exact timing. These results demonstrate that the adjoint method is well suited to study systems encountering regime changes, as a single run of the adjoint model provides sensitivities of the net CO2 flux to perturbations in all parameters and variables at any time of the year. Moreover, it is shown that large errors due to the presence of thresholds can be avoided by first delimiting the range of applicability of the adjoint results.

  4. Wet meadow ecosystems contribute the majority of overwinter soil respiration from snow-scoured alpine tundra

    NASA Astrophysics Data System (ADS)

    Knowles, John F.; Blanken, Peter D.; Williams, Mark W.

    2016-04-01

    We measured soil respiration across a soil moisture gradient ranging from dry to wet snow-scoured alpine tundra soils throughout three winters and two summers. In the absence of snow accumulation, soil moisture variability was principally determined by the combination of mesotopographical hydrological focusing and shallow subsurface permeability, which resulted in a patchwork of comingled ecosystem types along a single alpine ridge. To constrain the subsequent carbon cycling variability, we compared three measures of effective diffusivity and three methods to calculate gradient method soil respiration from four typical vegetation communities. Overwinter soil respiration was primarily restricted to wet meadow locations, and a conservative estimate of the rate of overwinter soil respiration from snow-scoured wet meadow tundra was 69-90% of the maximum carbon dioxide (CO2) respired by seasonally snow-covered soils within this same catchment. This was attributed to higher overwinter soil temperatures at wet meadow locations relative to fellfield, dry meadow, and moist meadow communities, which supported liquid water and heterotrophic respiration throughout the winter. These results were corroborated by eddy covariance-based measurements that demonstrated an average of 272 g C m-2 overwinter carbon loss during the study period. As a result, we updated a conceptual model of soil respiration versus snow cover to express the potential for soil respiration variability from snow-scoured alpine tundra.

  5. Functional convergence of tundra vegetation simplifies the interpretation of flux observations at larger spatial scales

    NASA Astrophysics Data System (ADS)

    Stoy, P. C.; Williams, M.; Evans, J. G.; Lloyd, C. R.; Prieto-Blanco, A.; Disney, M.; Street, L. E.; Shaver, G. R.

    2007-12-01

    A central challenge in terrestrial carbon cycle research is upscaling measurements of vegetation function to larger spatial and temporal scales. A solution is required to, for example, make chamber-based measurements relevant at larger spatial scales and to make eddy covariance measurements applicable to leaf or chamber- based studies. Here we demonstrate that a simple model for photosynthesis and ecosystem respiration parameterized using pan-arctic chamber flux measurements closely matches eddy covariance flux observations in a tundra ecosystem near Abisko, Sweden. The agreement holds when using a generic parameter set that does not account for vegetation type or measurement location. Inverting the model to predict leaf area using eddy covariance-measured net ecosystem exchange closely approximates tower-based LAI estimates across seasons and during periods of drought stress. Thus, recent findings documenting functional convergence of arctic vegetation holds at multiple spatial as well as temporal scales using both chamber and tower measurements. After validating the model using the eddy covariance measurements, we integrate the model with meteorological and LAI observations using a simple data assimilation scheme. The reduction of error achieved via data assimilation is compared to standard techniques of estimating eddy covariance error. Our analysis demonstrates that accurate estimates of C flux at multiple spatial scales across the tundra biome are possible given accurate estimates of photosynthetically active radiation, temperature, and leaf area index given the observed functional convergence of tundra vegetation.

  6. Evaluation of Moderate-Resolution Imaging Spectroradiometer (MODIS) Snow Albedo Product (MCD43A) over Tundra

    NASA Technical Reports Server (NTRS)

    Wang, Zhuosen; Schaaf, Crystal B.; Chopping, Mark J.; Strahler, Alan H.; Wang, Jindi; Roman, Miguel O.; Rocha, Adrian V.; Woodcock, Curtis E.; Shuai, Yanmin

    2012-01-01

    This study assesses the MODIS standard Bidirectional Reflectance Distribution Function (BRDF)/Albedo product, and the daily Direct Broadcast BRDF/Albedo algorithm at tundra locations under large solar zenith angles and high anisotropic diffuse illumination and multiple scattering conditions. These products generally agree with ground-based albedo measurements during the snow cover period when the Solar Zenith Angle (SZA) is less than 70deg. An integrated validation strategy, including analysis of the representativeness of the surface heterogeneity, is performed to decide whether direct comparisons between field measurements and 500- m satellite products were appropriate or if the scaling of finer spatial resolution airborne or spaceborne data was necessary. Results indicate that the Root Mean Square Errors (RMSEs) are less than 0.047 during the snow covered periods for all MCD43 albedo products at several Alaskan tundra areas. The MCD43 1- day daily albedo product is particularly well suited to capture the rapidly changing surface conditions during the spring snow melt. Results also show that a full expression of the blue sky albedo is necessary at these large SZA snow covered areas because of the effects of anisotropic diffuse illumination and multiple scattering. In tundra locations with dark residue as a result of fire, the MODIS albedo values are lower than those at the unburned site from the start of snowmelt.

  7. Summertime surface O3 behavior and deposition to tundra in the Alaskan Arctic

    NASA Astrophysics Data System (ADS)

    Van Dam, Brie; Helmig, Detlev; Doskey, Paul V.; Oltmans, Samuel J.

    2016-07-01

    Atmospheric turbulence quantities, boundary layer ozone (O3) levels, and O3 deposition to the tundra surface were investigated at Toolik Lake, AK, during the 2011 summer season. Beginning immediately after snowmelt, a diurnal cycle of O3 in the atmospheric surface layer developed with daytime O3 maxima, and minima during low-light hours, resulting in a mean amplitude of 13 ppbv. This diurnal O3 cycle is far larger than observed at other high Arctic locations during the snow-free season. During the snow-free months of June, July, and August, O3 deposition velocities were ˜3 to 5 times faster than during May, when snow covered the ground most of the month. The overall mean O3 deposition velocity between June and August was 0.10 cm s-1. The month of June had the highest diurnal variation, with a median O3 deposition velocity of 0.2 cm s-1 during the daytime and 0.08 cm s-1 during low-light conditions. These values are slightly lower than previously reported summertime deposition velocities in northern latitudes over tundra or fen. O3 loss during low-light periods was attributed to a combination of surface deposition to the tundra and stable boundary layer conditions. We also hypothesize that emissions of reactive biogenic volatile organic compounds into the shallow boundary layer may contribute to nighttime O3 loss.

  8. The response of Arctic vegetation and soils following an unusually severe tundra fire

    PubMed Central

    Bret-Harte, M. Syndonia; Mack, Michelle C.; Shaver, Gaius R.; Huebner, Diane C.; Johnston, Miriam; Mojica, Camilo A.; Pizano, Camila; Reiskind, Julia A.

    2013-01-01

    Fire causes dramatic short-term changes in vegetation and ecosystem function, and may promote rapid vegetation change by creating recruitment opportunities. Climate warming likely will increase the frequency of wildfire in the Arctic, where it is not common now. In 2007, the unusually severe Anaktuvuk River fire burned 1039 km2 of tundra on Alaska's North Slope. Four years later, we harvested plant biomass and soils across a gradient of burn severity, to assess recovery. In burned areas, above-ground net primary productivity of vascular plants equalled that in unburned areas, though total live biomass was less. Graminoid biomass had recovered to unburned levels, but shrubs had not. Virtually all vascular plant biomass had resprouted from surviving underground parts; no non-native species were seen. However, bryophytes were mostly disturbance-adapted species, and non-vascular biomass had recovered less than vascular plant biomass. Soil nitrogen availability did not differ between burned and unburned sites. Graminoids showed allocation changes consistent with nitrogen stress. These patterns are similar to those seen following other, smaller tundra fires. Soil nitrogen limitation and the persistence of resprouters will likely lead to recovery of mixed shrub–sedge tussock tundra, unless permafrost thaws, as climate warms, more extensively than has yet occurred. PMID:23836794

  9. Analysis of nitrogen saturation potential in Rocky Mountain tundra and forest: implications for aquatic systems

    USGS Publications Warehouse

    Baron, Jill S.; Ojima, Dennis S.; Holland, Elisabeth A.; Parton, William J.

    1994-01-01

    We employed grass and forest versions of the CENTURY model under a range of N deposition values (0.02–1.60 g N m−2 y−1) to explore the possibility that high observed lake and stream N was due to terrestrial N saturation of alpine tundra and subalpine forest in Loch Vale Watershed, Rocky Mountain National Park, Colorado. Model results suggest that N is limiting to subalpine forest productivity, but that excess leachate from alpine tundra is sufficient to account for the current observed stream N. Tundra leachate, combined with N leached from exposed rock surfaces, produce high N loads in aquatic ecosystems above treeline in the Colorado Front Range. A combination of terrestrial leaching, large N inputs from snowmelt, high watershed gradients, rapid hydrologic flushing and lake turnover times, and possibly other nutrient limitations of aquatic organisms constrain high elevation lakes and streams from assimilating even small increases in atmospheric N. CENTURY model simulations further suggest that, while increased N deposition will worsen the situation, nitrogen saturation is an ongoing phenomenon.

  10. Temperature and plant species control over litter decomposition in Alaskan tundra

    SciTech Connect

    Hobbie, S.E.

    1996-11-01

    This study compared effects of increased temperature and litter from different Alaskan tundra plant species on cycling of carbon and nitrogen through litter and soil in microcosms. Warming between 4{degrees} and 10{degrees}C significantly increased rates of soil and litter respiration, litter decomposition, litter nitrogen release, and soil net nitrogen mineralization. Thus, future warming will directly increase rates of carbon and nitrogen cycling through litter and soil in tundra. In addition, differences among species` litter in rates of decomposition, N release, and effects on soil net nitrogen mineralization were sometimes larger than differences between the two temperature treatments within a species. Thus, changes in plant community structure and composition associated with future warming will have important consequences for how elements cycle through litter and soil in tundra. In general, species within a growth form (graminoids, evergreen shrubs, deciduous shrubs, and mosses) were more similar in their effects on decomposition than were species belonging to different growth forms, with gramminoid litter having the fastest rate and litter of deciduous shrubs and mosses having the slowest rates. Differences in rates of litter decomposition were more related to carbon quality than to nitrogen concentration. Increased abundance of deciduous shrubs with future climate warming will promote carbon storage, because of their relatively large allocation to woody stems that decompose slowly. Changes in moss abundance will also have important consequences for future carbon and nitrogen cycling, since moss litter is extremely recalcitrant and has a low potential to immobilize nitrogen. 82 refs., 8 figs., 7 tabs.

  11. Soils of Sub-Antarctic tundras: diversity and basic chemical characteristics

    NASA Astrophysics Data System (ADS)

    Abakumov, Evgeny; Vlasov, Dmitry; Mukhametova, Nadezhda

    2014-05-01

    Antarctic peninsula is known as specific part of Antarctica, which is characterizes by humid and relatively warm climate of so-called sub Antarctic (maritime) zone. Annual precipitation and long above zero period provides the possibility of sustainable tundra's ecosystem formation. Therefore, the soil diversity of these tundra landscapes is maximal in the whole Antarctic. Moreover, the thickness of parent material debris's is also highest and achieves a 1 or 2 meters as highest. The presence of higher vascular plants Deshampsia antarctica which is considered as one of the main edificators provides the development of humus accumulation in upper solum. Penguins activity provides an intensive soil fertilization and development of plant communities with increased density. All these factors leads to formation of specific and quite diverse soil cover in sub Antarctic tundra's. These ecosystems are presented by following permafrost affected soils: Leptosols, Lithoosols, Crysols, Gleysols, Peats and Ornhitosols. Also the post Ornhitosols are widely spreaded in subantarcic ecosystems, they forms on the penguin rockeries during the plant succession development, leaching of nutrients and organic matter mineralization. "Amphibious" soils are specific for seasonal lakes, which evaporates in the end if Australian summer. These soils have specific features of bio sediments and soils as well. Soil chemical characteristic as well as organic matter features discussed in comparison with Antacrtic continental soil in presentation.

  12. The biogeochemistry of microbial mats, stromatolites and the ancient biosphere

    NASA Technical Reports Server (NTRS)

    Desmarais, D. J.; Canfield, D. E.

    1991-01-01

    Stromatolites offer an unparalleled geologic record of early life, because they constitute the oldest and most abundant recognizable remains of microbial ecosystems. Microbial mats are living homologs of stromatolites; thus, the physiology of the microbiota as well as the processes which create those features of mats (e.g., biomarker organic compounds, elemental and stable isotopic compositions) which are preserved in the ancient record. Observations of the carbon isotopic composition (delta C-13) of stromatolites and microbial mats were made and are consistent with the hypothesis that atmospheric CO2 concentrations have declined by at least one to two orders of magnitude during the past 2.5 Ga. Whereas delta C-13 values of carbonate carbon average about 0 permil during both the early and mid-Proterozoic, the delta C-13 values of stromatolitic organic matter increase from an average of -35 between 2.0 and 2.6 Ga ago to an average of about -28 about 1.0 Ga ago. Modern microbial mats in hypersaline environments have delta C-13 values typically in the range of -5 to -9, relative to an inorganic bicarbonate source at 0 permil. Both microbial mats and pur cultures of cyanobacteria grown in waters in near equilibrium with current atmospheric CO2 levels exhibit minimal discrimination against C-13. In contrast, hot spring cyanobacterial mats or cyanobacterial cultures grown under higher CO2 levels exhibit substantially greater discrimination. If care is taken to compare modern mats with stromatolites from comparable environments, it might be possible to estimate ancient levels of atmospheric CO2. In modern microbial mats, a tight coupling exists between photosynthetic organic carbon production and subsequent carbon oxidation, mostly by sulfate reduction. The rate of one process fuels a high rate of the other, with much of the sulfate reduction occurring within the same depth interval as oxygenic photosynthesis. Other aspects of this study are presented.

  13. Nitrification and Nitrifying Bacteria in a Coastal Microbial Mat.

    PubMed

    Fan, Haoxin; Bolhuis, Henk; Stal, Lucas J

    2015-01-01

    The first step of nitrification, the oxidation of ammonia to nitrite, can be performed by ammonia-oxidizing archaea (AOA) or ammonium-oxidizing bacteria (AOB). We investigated the presence of these two groups in three structurally different types of coastal microbial mats that develop along the tidal gradient on the North Sea beach of the Dutch barrier island Schiermonnikoog. The abundance and transcription of amoA, a gene encoding for the alpha subunit of ammonia monooxygenase that is present in both AOA and AOB, were assessed and the potential nitrification rates in these mats were measured. The potential nitrification rates in the three mat types were highest in autumn and lowest in summer. AOB and AOA amoA genes were present in all three mat types. The composition of the AOA and AOB communities in the mats of the tidal and intertidal stations, based on the diversity of amoA, were similar and clustered separately from the supratidal microbial mat. In all three mats AOB amoA genes were significantly more abundant than AOA amoA genes. The abundance of neither AOB nor AOA amoA genes correlated with the potential nitrification rates, but AOB amoA transcripts were positively correlated with the potential nitrification rate. The composition and abundance of amoA genes seemed to be partly driven by salinity, ammonium, temperature, and the nitrate/nitrite concentration. We conclude that AOB are responsible for the bulk of the ammonium oxidation in these coastal microbial mats. PMID:26648931

  14. Nitrification and Nitrifying Bacteria in a Coastal Microbial Mat

    PubMed Central

    Fan, Haoxin; Bolhuis, Henk; Stal, Lucas J.

    2015-01-01

    The first step of nitrification, the oxidation of ammonia to nitrite, can be performed by ammonia-oxidizing archaea (AOA) or ammonium-oxidizing bacteria (AOB). We investigated the presence of these two groups in three structurally different types of coastal microbial mats that develop along the tidal gradient on the North Sea beach of the Dutch barrier island Schiermonnikoog. The abundance and transcription of amoA, a gene encoding for the alpha subunit of ammonia monooxygenase that is present in both AOA and AOB, were assessed and the potential nitrification rates in these mats were measured. The potential nitrification rates in the three mat types were highest in autumn and lowest in summer. AOB and AOA amoA genes were present in all three mat types. The composition of the AOA and AOB communities in the mats of the tidal and intertidal stations, based on the diversity of amoA, were similar and clustered separately from the supratidal microbial mat. In all three mats AOB amoA genes were significantly more abundant than AOA amoA genes. The abundance of neither AOB nor AOA amoA genes correlated with the potential nitrification rates, but AOB amoA transcripts were positively correlated with the potential nitrification rate. The composition and abundance of amoA genes seemed to be partly driven by salinity, ammonium, temperature, and the nitrate/nitrite concentration. We conclude that AOB are responsible for the bulk of the ammonium oxidation in these coastal microbial mats. PMID:26648931

  15. Regulation of electron transfer processes affects phototrophic mat structure and activity.

    PubMed

    Ha, Phuc T; Renslow, Ryan S; Atci, Erhan; Reardon, Patrick N; Lindemann, Stephen R; Fredrickson, James K; Call, Douglas R; Beyenal, Haluk

    2015-01-01

    Phototrophic microbial mats are among the most diverse ecosystems in nature. These systems undergo daily cycles in redox potential caused by variations in light energy input and metabolic interactions among the microbial species. In this work, solid electrodes with controlled potentials were placed under mats to study the electron transfer processes between the electrode and the microbial mat. The phototrophic microbial mat was harvested from Hot Lake, a hypersaline, epsomitic lake located near Oroville (Washington, USA). We operated two reactors: graphite electrodes were polarized at potentials of -700 mVAg/AgCl [cathodic (CAT) mat system] and +300 mVAg/AgCl [anodic (AN) mat system] and the electron transfer rates between the electrode and mat were monitored. We observed a diel cycle of electron transfer rates for both AN and CAT mat systems. Interestingly, the CAT mats generated the highest reducing current at the same time points that the AN mats showed the highest oxidizing current. To characterize the physicochemical factors influencing electron transfer processes, we measured depth profiles of dissolved oxygen (DO) and sulfide in the mats using microelectrodes. We further demonstrated that the mat-to-electrode and electrode-to-mat electron transfer rates were light- and temperature-dependent. Using nuclear magnetic resonance (NMR) imaging, we determined that the electrode potential regulated the diffusivity and porosity of the microbial mats. Both porosity and diffusivity were higher in the CAT mats than in the AN mats. We also used NMR spectroscopy for high-resolution quantitative metabolite analysis and found that the CAT mats had significantly higher concentrations of osmoprotectants such as betaine and trehalose. Subsequently, we performed amplicon sequencing across the V4 region of the 16S rRNA gene of incubated mats to understand the impact of electrode potential on microbial community structure. These data suggested that variation in the

  16. Regulation of electron transfer processes affects phototrophic mat structure and activity

    PubMed Central

    Ha, Phuc T.; Renslow, Ryan S.; Atci, Erhan; Reardon, Patrick N.; Lindemann, Stephen R.; Fredrickson, James K.; Call, Douglas R.; Beyenal, Haluk

    2015-01-01

    Phototrophic microbial mats are among the most diverse ecosystems in nature. These systems undergo daily cycles in redox potential caused by variations in light energy input and metabolic interactions among the microbial species. In this work, solid electrodes with controlled potentials were placed under mats to study the electron transfer processes between the electrode and the microbial mat. The phototrophic microbial mat was harvested from Hot Lake, a hypersaline, epsomitic lake located near Oroville (Washington, USA). We operated two reactors: graphite electrodes were polarized at potentials of -700 mVAg/AgCl [cathodic (CAT) mat system] and +300 mVAg/AgCl [anodic (AN) mat system] and the electron transfer rates between the electrode and mat were monitored. We observed a diel cycle of electron transfer rates for both AN and CAT mat systems. Interestingly, the CAT mats generated the highest reducing current at the same time points that the AN mats showed the highest oxidizing current. To characterize the physicochemical factors influencing electron transfer processes, we measured depth profiles of dissolved oxygen (DO) and sulfide in the mats using microelectrodes. We further demonstrated that the mat-to-electrode and electrode-to-mat electron transfer rates were light- and temperature-dependent. Using nuclear magnetic resonance (NMR) imaging, we determined that the electrode potential regulated the diffusivity and porosity of the microbial mats. Both porosity and diffusivity were higher in the CAT mats than in the AN mats. We also used NMR spectroscopy for high-resolution quantitative metabolite analysis and found that the CAT mats had significantly higher concentrations of osmoprotectants such as betaine and trehalose. Subsequently, we performed amplicon sequencing across the V4 region of the 16S rRNA gene of incubated mats to understand the impact of electrode potential on microbial community structure. These data suggested that variation in the

  17. Disruption of photoautotrophic intertidal mats by filamentous fungi.

    PubMed

    Carreira, Cátia; Staal, Marc; Falkoski, Daniel; de Vries, Ronald P; Middelboe, Mathias; Brussaard, Corina P D

    2015-08-01

    Ring-like structures, 2.0-4.8 cm in diameter, observed in photosynthetic microbial mats on the Wadden Sea island Schiermonnikoog (the Netherlands) showed to be the result of the fungus Emericellopsis sp. degrading the photoautotrophic top layer of the mat. The mats were predominantly composed of cyanobacteria and diatoms, with large densities of bacteria and viruses both in the top photosynthetic layer and in the underlying sediment. The fungal attack cleared the photosynthetic layer; however, no significant effect of the fungal lysis on the bacterial and viral abundances could be detected. Fungal-mediated degradation of the major photoautotrophs could be reproduced by inoculation of non-infected mat with isolated Emericellopsis sp., and with an infected ring sector. Diatoms were the first re-colonizers followed closely by cyanobacteria that after about 5 days dominated the space. The study demonstrated that the fungus Emericellopsis sp. efficiently degraded a photoautotrophic microbial mat, with potential implications for mat community composition, spatial structure and productivity. PMID:25728280

  18. Cyanobacterial reuse of extracellular organic carbon in microbial mats.

    PubMed

    Stuart, Rhona K; Mayali, Xavier; Lee, Jackson Z; Craig Everroad, R; Hwang, Mona; Bebout, Brad M; Weber, Peter K; Pett-Ridge, Jennifer; Thelen, Michael P

    2016-05-01

    Cyanobacterial organic matter excretion is crucial to carbon cycling in many microbial communities, but the nature and bioavailability of this C depend on unknown physiological functions. Cyanobacteria-dominated hypersaline laminated mats are a useful model ecosystem for the study of C flow in complex communities, as they use photosynthesis to sustain a more or less closed system. Although such mats have a large C reservoir in the extracellular polymeric substances (EPSs), the production and degradation of organic carbon is not well defined. To identify extracellular processes in cyanobacterial mats, we examined mats collected from Elkhorn Slough (ES) at Monterey Bay, California, for glycosyl and protein composition of the EPS. We found a prevalence of simple glucose polysaccharides containing either α or β (1,4) linkages, indicating distinct sources of glucose with differing enzymatic accessibility. Using proteomics, we identified cyanobacterial extracellular enzymes, and also detected activities that indicate a capacity for EPS degradation. In a less complex system, we characterized the EPS of a cyanobacterial isolate from ES, ESFC-1, and found the extracellular composition of biofilms produced by this unicyanobacterial culture were similar to that of natural mats. By tracing isotopically labeled EPS into single cells of ESFC-1, we demonstrated rapid incorporation of extracellular-derived carbon. Taken together, these results indicate cyanobacteria reuse excess organic carbon, constituting a dynamic pool of extracellular resources in these mats. PMID:26495994

  19. Methane Production by Microbial Mats Under Low Sulfate Concentrations

    NASA Technical Reports Server (NTRS)

    Bebout, Brad M.; Hoehler, Tori M.; Thamdrup, Bo; Albert, Dan; Carpenter, Steven P.; Hogan, Mary; Turk, Kendra; DesMarais, David J.

    2003-01-01

    Cyanobacterial mats collected in hypersaline salterns were incubated in a greenhouse under low sulfate concentrations ([SO4]) and examined for their primary productivity and emissions of methane and other major carbon species. Atmospheric greenhouse warming by gases such as carbon dioxide and methane must have been greater during the Archean than today in order to account for a record of moderate to warm paleoclemates, despite a less luminous early sun. It has been suggested that decreased levels of oxygen and sulfate in Archean oceans could have significantly stimulated microbial methanogenesis relative to present marine rates, with a resultant increase in the relative importance of methane in maintaining the early greenhouse. We maintained modern microbial mats, models of ancient coastal marine communities, in artificial brine mixtures containing both modern [SO4=] (ca. 70 mM) and "Archean" [SO4] (less than 0.2 mM). At low [SO4], primary production in the mats was essentially unaffected, while rates of sulfate reduction decreased by a factor of three, and methane fluxes increased by up to ten-fold. However, remineralization by methanogenesis still amounted to less than 0.4 % of the total carbon released by the mats. The relatively low efficiency of conversion of photosynthate to methane is suggested to reflect the particular geometry and chemical microenvironment of hypersaline cyanobacterial mats. Therefore, such mats w-ere probably relatively weak net sources of methane throughout their 3.5 Ga history, even during periods of low- environmental levels oxygen and sulfate.

  20. Swi6, a Gene Required for Mating-Type Switching, Prohibits Meiotic Recombination in the Mat2-Mat3 ``cold Spot'' of Fission Yeast

    PubMed Central

    Klar, AJS.; Bonaduce, M. J.

    1991-01-01

    Mitotic interconversion of the mating-type locus (mat1) of the fission yeast Schizosaccharomyces pombe is initiated by a double-strand break at mat1. The mat2 and mat3 loci act as nonrandom donors of genetic information for mat1 switching such that switches occur primarily (or only) to the opposite mat1 allele. Location of the mat1 ``hot spot'' for transposition should be contrasted with the ``cold spot'' of meiotic recombination located within the adjoining mat2-mat3 interval. That is, meiotic interchromosomal recombination in mat2, mat3 and the intervening 15-kilobase region does not occur at all. swi2 and swi6 switching-deficient mutants possess the normal level of double-strand break at mat1, yet they fail to switch efficiently. By testing for meiotic recombination in the cold spot, we found the usual lack of recombination in a swi2 mutant but a significant level of recombination in a swi6 mutant. Therefore, the swi6 gene function is required to keep the donor loci inert for interchromosomal recombination. This finding, combined with the additional result that switching primarily occurs intrachromosomally, suggests that the donor loci are made accessible for switching by folding them onto mat1, thus causing the cold spot of recombination. PMID:1783290

  1. ERB master archival tape specification no. T 134081 ERB MAT, revision 1

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The Earth radiation budget (ERB)MAT tapes are generated by the ERB MATGEN software using the IBM 3081 computer system operated by the Science and Applications Computer Center at Goddard Space Flight Center. All MAT's are 9-track and MAT data are in ascending time order. The gross tape format for NIMBUS year-1 and year-2 MAT's is different from the format of MAT's starting with year-3. The MATs from the first two years are to contain one day's worth of data while all other MATs are to contain multiple day's worth of data stacked onto the tapes.

  2. Modeling dynamics of tundra plant communities on the Yamal Peninsula, Russia, in response to climate change and grazing pressure

    NASA Astrophysics Data System (ADS)

    Yu, Q.; Epstein, H. E.; Walker, D. A.; Frost, G. V.; Forbes, B. C.

    2011-10-01

    Understanding the responses of the arctic tundra biome to a changing climate requires knowledge of the complex interactions among the climate, soils and biological system. This study investigates the individual and interaction effects of climate change and reindeer grazing across a variety of climate zones and soil texture types on tundra vegetation community dynamics using an arctic vegetation model that incorporates the reindeer diet, where grazing is a function of both foliar nitrogen concentration and reindeer forage preference. We found that grazing is important, in addition to the latitudinal climate gradient, in controlling tundra plant community composition, explaining about 13% of the total variance in model simulations for all arctic tundra subzones. The decrease in biomass of lichen, deciduous shrub and graminoid plant functional types caused by grazing is potentially dampened by climate warming. Moss biomass had a nonlinear response to increased grazing intensity, and such responses were stronger when warming was present. Our results suggest that evergreen shrubs may benefit from increased grazing intensity due to their low palatability, yet a growth rate sensitivity analysis suggests that changes in nutrient uptake rates may result in different shrub responses to grazing pressure. Heavy grazing caused plant communities to shift from shrub tundra toward moss, graminoid-dominated tundra in subzones C and D when evergreen shrub growth rates were decreased in the model. The response of moss, lichen and forbs to warming varied across the different subzones. Initial vegetation responses to climate change during transient warming are different from the long term equilibrium responses due to shifts in the controlling mechanisms (nutrient limitation versus competition) within tundra plant communities.

  3. Epicardial delivery of VEGF and cardiac stem cells guided by 3-dimensional PLLA mat enhancing cardiac regeneration and angiogenesis in acute myocardial infarction.

    PubMed

    Chung, Hye-Jin; Kim, Jong-Tae; Kim, Hee-Jung; Kyung, Hei-Won; Katila, Pramila; Lee, Jeong-Han; Yang, Tae-Hyun; Yang, Young-Il; Lee, Seung-Jin

    2015-05-10

    Congestive heart failure is mostly resulted in a consequence of the limited myocardial regeneration capacity after acute myocardial infarction. Targeted delivery of proangiogenic factors and/or stem cells to the ischemic myocardium is a promising strategy for enhancing their local and sustained therapeutic effects. Herein, we designed an epicardial delivery system of vascular endothelial growth factor (VEGF) and cardiac stem cells (CSCs) using poly(l-lactic acid) (PLLA) mat applied to the acutely infarcted myocardium. The fibrous VEGF-loaded PLLA mat was fabricated by an electrospinning method using PLLA solution emulsified VEGF. This mat not only allowed for sustained release of VEGF for 4weeks but boosted migration and proliferation of both endothelial cells and CSCs in vitro. Furthermore, sustained release of VEGF showed a positive effect on in vitro capillary-like network formation of endothelial cells compared with bolus treatment of VEGF. PLLA mat provided a permissive 3-dimensional (3D) substratum that led to spontaneous cardiomyogenic differentiation of CSCs in vitro. Notably, sustained stimulation by VEGF-loaded PLLA mat resulted in a substantial increase in the expression of proangiogenic mRNAs of CSCs in vitro. The epicardially implanted VEGF-loaded PLLA mat showed modest effects on angiogenesis and cardiomyogenesis in the acutely infarcted hearts. However, co-implantation of VEGF and CSCs using the PLLA mat showed meaningful therapeutic effects on angiogenesis and cardiomyogenesis compared with controls, leading to reduced cardiac remodeling and enhanced global cardiac function. Collectively, the PLLA mat allowed a smart cargo that enabled the sustained release of VEGF and the delivery of CSCs, thereby synergistically inducing angiogenesis and cardiomyogenesis in acute myocardial infarction. PMID:25681051

  4. Gaps in Data and Modeling Tools for Understanding Fire and Fire Effects in Tundra Ecosystems

    NASA Astrophysics Data System (ADS)

    French, N. H.; Miller, M. E.; Loboda, T. V.; Jenkins, L. K.; Bourgeau-Chavez, L. L.; Suiter, A.; Hawkins, S. M.

    2013-12-01

    As the ecosystem science community learns more about tundra ecosystems and disturbance in tundra, a review of base data sets and ecological field data for the region shows there are many gaps that need to be filled. In this paper we will review efforts to improve our knowledge of the occurrence and impacts of fire in the North American tundra region completed under a NASA Terrestrial Ecology grant. Our main source of information is remote sensing data from satellite sensors and ecological data from past and recent field data collections by our team, collaborators, and others. Past fire occurrence is not well known for this region compared with other North American biomes. In this presentation we review an effort to use a semi-automated detection algorithm to identify past fire occurrence using the Landsat TM/ETM+ archives, pointing out some of the still-unaddressed issues for a full understanding of fire regime for the region. For this task, fires in Landsat scenes were mapped using the Random Forest classifier (Breiman 2001) to automatically detect potential burn scars. Random Forests is an ensemble classifier that employs machine learning to build a large collection of decision trees that are grown from a random selection of user supplied training data. A pixel's classification is then determined by which class receives the most 'votes' from each tree. We also review the use fire location records and existing modeling methods to quantify emissions from these fires. Based on existing maps of vegetation fuels, we used the approach developed for the Wildland Fire Emissions Information System (WFEIS; French et al. 2011) to estimate emissions across the tundra region. WFEIS employs the Consume model (http://www.fs.fed.us/pnw/fera/research/smoke/consume/index.shtml) to estimate emissions by applying empirically developed relationships between fuels, fire conditions (weather-based fire indexes), and emissions. Here again, we will review the gaps in data and modeling

  5. MatMRI and MatHIFU: Matlab{trade mark, serif} toolboxes for real-time monitoring and control of MR-HIFU

    NASA Astrophysics Data System (ADS)

    Sinclair, Tony; Mougenot, Charles; Kivinen, Jon; Pichardo, Samuel

    2012-11-01

    Background. Availability of open tools is a key feature to facilitate the development of pre-clinical research of Magnetic Resonance-guided High Intensity Focused Ultrasound (MR-HIFU). MatMRI is a toolbox that allows direct communication with a Philips{trade mark, serif} MRI scanner in a Matlab{trade mark, serif} environment, which is well-known in many laboratories. MatMRI performs real-time acquisition of magnitude and phase images that can be processed to estimate changes of temperature. Available functionality of MatMRI includes acquisition of individual slices and volumetric data. Analogously to MatMRI, MatHIFU is a toolbox for the control of the Philips Sonalleve MR-HIFU system. MatHIFU allows the execution of user-defined treatment protocols such as thermal ablation, hyperthermia or drug delivery. MatMRI and MatHIFU can be used independently or in combination. Methods. MatMRI was based on the official tool for MRI data-dumping made by Philips Healthcare. Multi-threading capabilities were added to maximize real-time processing performance. Basic use of MatMRI involves four basic steps: initiate communication, subscribe to MRI data, query for new images and unsubscribe. If required, MatMRI can also pause/resume the scanning and update on real-time the location and orientation of the images. MatHIFU performs the execution of sonication protocols and allows real-time monitoring. Basic use of MatHIFU requires also four steps: preparation of sonication protocol, initiate communication, execute sonication protocol and monitor the state of execution. Results. MatMRI was integrated into existing software used to control a table designed for animal experimentation (FUS Instruments, Canada). The integration in the existing software was seamless and delivered real-time estimation of changes of temperature in a mouse model. Using MatHIFU and MatMRI, a complete new interface to control the Sonalleve system was developed to perform in vivo experiments allowing adapted

  6. Photosynthetic Microbial Mats are Exemplary Sources of Diverse Biosignatures (Invited)

    NASA Astrophysics Data System (ADS)

    Des Marais, D. J.; Jahnke, L. L.

    2013-12-01

    Marine cyanobacterial microbial mats are widespread, compact, self-contained ecosystems that create diverse biosignatures and have an ancient fossil record. Within the mats, oxygenic photosynthesis provides organic substrates and O2 to the community. Both the absorption and scattering of light change the intensity and spectral composition of incident radiation as it penetrates a mat. Some phototrophs utilize infrared light near the base of the photic zone. A mat's upper layers can become highly reduced and sulfidic at night. Counteracting gradients of O2 and sulfide shape the chemical environment and provide daily-contrasting microenvironments separated on a scale of a few mm. Radiation hazards (UV, etc.), O2 and sulfide toxicity elicit motility and other physiological responses. This combination of benefits and hazards of light, O2 and sulfide promotes the allocation of various essential mat processes between light and dark periods and to various depths in the mat. Associated nonphotosynthetic communities, including anaerobes, strongly influence many of the ecosystem's overall characteristics, and their processes affect any biosignatures that enter the fossil record. A biosignature is an object, substance and/or pattern whose origin specifically requires a biological agent. The value of a biosignature depends not only on the probability of life creating it, but also on the improbability of nonbiological processes producing it. Microbial mats create biosignatures that identify particular groups of organisms and also reveal attributes of the mat ecosystem. For example, branched hydrocarbons and pigments can be diagnostic of cyanobacteria and other phototrophic bacteria, and isoprenoids can indicate particular groups of archea. Assemblages of lipid biosignatures change with depth due to changes in microbial populations and diagenetic transformations of organic matter. The 13C/12C values of organic matter and carbonates reflect isotopic discrimination by particular

  7. Diel Migrations of Microorganisms within a Benthic, Hypersaline Mat Community

    PubMed Central

    Garcia-Pichel, Ferran; Mechling, Margaret; Castenholz, Richard W.

    1994-01-01

    We studied the diel migrations of several species of microorganisms in a hypersaline, layered microbial mat. The migrations were quantified by repeated coring of the mat with glass capillary tubes. The resulting minicores were microscopically analyzed by using bright-field and epifluorescence (visible and infrared) microscopy to determine depths of coherent layers and were later dissected to determine direct microscopic counts of microorganisms. Microelectrode measurements of oxygen concentration, fiber optic microprobe measurements of light penetration within the mat, and incident irradiance measurements accompanied the minicore sampling. In addition, pigment content, photosynthesis and irradiance responses, the capacity for anoxygenic photosynthesis, and gliding speeds were determined for the migrating cyanobacteria. Heavily pigmented Oscillatoria sp. and Spirulina cf. subsalsa migrated downward into the mat during the early morning and remained deep until dusk, when upward migration occurred. The mean depth of the migration (not more than 0.4 to 0.5 mm) was directly correlated with the incident irradiance over the mat surface. We estimated that light intensity at the upper boundary of the migrating cyanobacteria was attenuated to such an extent that photoinhibition was effectively avoided but that intensities which saturated photosynthesis were maintained through most of the daylight hours. Light was a cue of paramount importance in triggering and modulating the migration of the cyanobacteria, even though the migrating phenomenon could not be explained solely in terms of a light response. We failed to detect diel migration patterns for other cyanobacterial species and filamentous anoxyphotobacteria. The sulfide-oxidizing bacterium Beggiatoa sp. migrated as a band that followed low oxygen concentrations within the mat during daylight hours. During the nighttime, part of this population migrated toward the mat surface, but a significant proportion remained deep

  8. Extraction of high molecular weight DNA from microbial mats.

    PubMed

    Bey, Benjamin S; Fichot, Erin B; Norman, R Sean

    2011-01-01

    Successful and accurate analysis and interpretation of metagenomic data is dependent upon the efficient extraction of high-quality, high molecular weight (HMW) community DNA. However, environmental mat samples often pose difficulties to obtaining large concentrations of high-quality, HMW DNA. Hypersaline microbial mats contain high amounts of extracellular polymeric substances (EPS)1 and salts that may inhibit downstream applications of extracted DNA. Direct and harsh methods are often used in DNA extraction from refractory samples. These methods are typically used because the EPS in mats, an adhesive matrix, binds DNA during direct lysis. As a result of harsher extraction methods, DNA becomes fragmented into small sizes. The DNA thus becomes inappropriate for large-insert vector cloning. In order to circumvent these limitations, we report an improved methodology to extract HMW DNA of good quality and quantity from hypersaline microbial mats. We employed an indirect method involving the separation of microbial cells from the background mat matrix through blending and differential centrifugation. A combination of mechanical and chemical procedures was used to extract and purify DNA from the extracted microbial cells. Our protocol yields approximately 2 μg of HMW DNA (35-50 kb) per gram of mat sample, with an A(260/280) ratio of 1.6. Furthermore, amplification of 16S rRNA genes suggests that the protocol is able to minimize or eliminate any inhibitory effects of contaminants. Our results provide an appropriate methodology for the extraction of HMW DNA from microbial mats for functional metagenomic studies and may be applicable to other environmental samples from which DNA extraction is challenging. PMID:21775955

  9. Modeling dynamics of circum-arctic tundra plant communities in response to climate warming and grazing pressure

    NASA Astrophysics Data System (ADS)

    Yu, Q.; Epstein, H. E.; Walker, D. A.; Forbes, B. C.; Vors, L. S.

    2011-12-01

    The Arctic is a complex system with strong interconnectedness among system components. Understanding the responses of the arctic tundra biome to a changing climate requires knowledge of the complex interactions among climate, soils, and the biological system. In this study, we investigate the individual and interactive effects of projected climate change and reindeer/caribou grazing across a variety of climate zones and soil nutrient levels on tundra plant community dynamics using an arctic vegetation model - ArcVeg. Our research questions include: 1) How does soil nutrient availability affect tundra vegetation responses to projected climate warming? 2) How does grazing affect tundra vegetation responses? 3) How do interactions of soil nutrients, climate warming and grazing affect tundra vegetation? We based our simulations on A1B scenario temperature data from the Intergovernmental Panel on Climate Change (IPCC), soil organic nitrogen data from Terrestrial Ecosystem Model (TEM) simulations and grazing pressure derived from reindeer/caribou population data from the CircumArctic Rangifer Monitoring and Assessment Network (CARMA). We found that in general tundra communities responded to warming with increased plant biomass, but the magnitude of the response is affected by the bioclimate zones, warming magnitude, available soil nutrients and grazing pressures. Regions with greater soil organic nitrogen responded to warming with greater biomass increase, Low Arctic tundra tended to have greater biomass increase than High Arctic tundra due to greater shrub abundance. However, such responses are mitigated by grazing. Regions with greater reindeer population and thus greater grazing intensity tended to have stronger negative effects on plant responses to warming than regions with less grazing. For example, in Subzone D, total biomass and NPP increases due to warming were about 71% and 43% in an Alaskan low grazing-intensity region, but 63% and 36% in a northwestern Canada

  10. Molecular detection of hematozoa infections in tundra swans relative to migration patterns and ecological conditions at breeding grounds

    USGS Publications Warehouse

    Ramey, Andrew M.; Ely, Craig R.; Schmutz, Joel A.; Pearce, John M.; Heard, Darryl J.

    2012-01-01

    Tundra swans (Cygnus columbianus) are broadly distributed in North America, use a wide variety of habitats, and exhibit diverse migration strategies. We investigated patterns of hematozoa infection in three populations of tundra swans that breed in Alaska using satellite tracking to infer host movement and molecular techniques to assess the prevalence and genetic diversity of parasites. We evaluated whether migratory patterns and environmental conditions at breeding areas explain the prevalence of blood parasites in migratory birds by contrasting the fit of competing models formulated in an occupancy modeling framework and calculating the detection probability of the top model using Akaike Information Criterion (AIC). We described genetic diversity of blood parasites in each population of swans by calculating the number of unique parasite haplotypes observed. Blood parasite infection was significantly different between populations of Alaska tundra swans, with the highest estimated prevalence occurring among birds occupying breeding areas with lower mean daily wind speeds and higher daily summer temperatures. Models including covariates of wind speed and temperature during summer months at breeding grounds better predicted hematozoa prevalence than those that included annual migration distance or duration. Genetic diversity of blood parasites in populations of tundra swans appeared to be relative to hematozoa prevalence. Our results suggest ecological conditions at breeding grounds may explain differences of hematozoa infection among populations of tundra swans that breed in Alaska.

  11. Master function for the solid:solution equilibrium of DOC in taiga and tundra soils of N. Russia: experimental and modeling results

    NASA Astrophysics Data System (ADS)

    Oosterwoud, M. R.; van der Zee, S. E. A. T. M.; Meeussen, J. C. L.; Temminghoff, E. J. M.

    2012-04-01

    The formation and degradation of Dissolved Organic Carbon (DOC) in arctic environments is intensively investigated, in the context of DOC loading of arctic rivers and seas as well as climate change. However, chemical interaction studies are more scarce, in particular those involving modeling. We investigated DOC interactions in N. Russian taiga and tundra soils, and found that water extractable organic carbon (WEOC) comprises only a small fraction of total organic carbon, whereas DOC is again a small fraction of WEOC. The chemical composition of DOC in terms of humic, fulvic, and hydrophilic acids, the concentrations of dominant cations such as Ca and Al, and the solid iron oxide contents appear to differ profoundly for different soil horizons, as well as between taiga and tundra soils. To reconcile these differences, we processed the data with a simple Freundlich model and with advanced LCD (Ligand and Charge Distribution) modeling of DOC interactions. In the LCD modeling, a combination is made of advances such as CD-MUSIC, and Nica-Donnan approaches, that are implemented in the software ORCHESTRA (though adjusted for computational stability by us). To avoid fitting without good foundation, use is made of the generic parameterization of LCD in combination with measured, site-specific chemical data such as concentrations. We observe that the soil samples from both regions, soil types and horizons can be described with a single DOC sorption Freundlich isotherm. More interestingly, for the same set of samples, the LCD modeling enables us to cast DOC sorption into a single Master Function, that takes iron oxide content and Al and Ca concentrations of soil samples into account in a purely predictive way. Based on this Master Function, it is feasible to assess how DOC is sorbed onto the solid surface. In combination with DOC production and degradation models, our results provide a more balanced instrument to address changes in DOC loading to surface waters due to

  12. Documentation generator application for MatLab source codes

    NASA Astrophysics Data System (ADS)

    Niton, B.; Pozniak, K. T.; Romaniuk, R. S.

    2011-06-01

    The UML, which is a complex system modeling and description technology, has recently been expanding its uses in the field of formalization and algorithmic approach to such systems like multiprocessor photonic, optoelectronic and advanced electronics carriers; distributed, multichannel measurement systems; optical networks, industrial electronics, novel R&D solutions. The paper describes a realization of an application for documenting MatLab source codes. There are presented own novel solution based on Doxygen program which is available on the free license, with accessible source code. The used supporting tools for parser building were Bison and Flex. There are presented the practical results of the documentation generator. The program was applied for exemplary MatLab codes. The documentation generator application is used for design of large optoelectronic and electronic measurement and control systems. The paper consists of three parts which describe the following components of the documentation generator for photonic and electronic systems: concept, MatLab application and VHDL application. This is part two which describes the MatLab application. MatLab is used for description of the measured phenomena.

  13. Microcosm experiments of oil degradation by microbial mats.

    PubMed

    de Oteyza, Tirso García; Grimalt, Joan O; Llirós, Marc; Esteve, Isabel

    2006-03-15

    Several microcosm experiments were run in parallel to evaluate the efficiency of microbial mats for crude oil degradation as compared with physico-chemical weathering. The oils used in the experiments constituted representative examples of those currently used for commercial purposes. One was aliphatic and of low viscosity (33.4 American Petroleum Institute degrees, degrees API) and the other was predominantly aromatic, with high sulphur content (ca. 2.7%) and viscosity (16.6 degrees API). After crude oil introduction, the microcosms were kept under cyclic changes in water level to mimic coastal tidal movements. The transformations observed showed that water weathering leads to more effective and rapid elimination of low molecular weight hydrocarbons than microbial mat metabolism, e.g. n-alkanes with chain length shorter than n-pentadecane or n-heptadecane, regular isoprenoid hydrocarbons with chain length lower than C16 or C18 or lower molecular weight naphthalenes. Microbial mats preserved these hydrocarbons from volatilization and water washing. However, hydrocarbons of lower volatility such as the C24-C30 n-alkanes or containing nitrogen atoms, e.g. carbazoles, were eliminated in higher proportion by microbial mats than by water weathering. The strong differences in composition between the two oils used for the experiments were also reflected in significant differences between water weathering and microbial mat biodegradation. Higher oil viscosity seemed to hinder the former but not the later. PMID:15935450

  14. Mating-Type Genes and MAT Switching in Saccharomyces cerevisiae

    PubMed Central

    Haber, James E.

    2012-01-01

    Mating type in Saccharomyces cerevisiae is determined by two nonhomologous alleles, MATa and MATα. These sequences encode regulators of the two different haploid mating types and of the diploids formed by their conjugation. Analysis of the MATa1, MATα1, and MATα2 alleles provided one of the earliest models of cell-type specification by transcriptional activators and repressors. Remarkably, homothallic yeast cells can switch their mating type as often as every generation by a highly choreographed, site-specific homologous recombination event that replaces one MAT allele with different DNA sequences encoding the opposite MAT allele. This replacement process involves the participation of two intact but unexpressed copies of mating-type information at the heterochromatic loci, HMLα and HMRa, which are located at opposite ends of the same chromosome-encoding MAT. The study of MAT switching has yielded important insights into the control of cell lineage, the silencing of gene expression, the formation of heterochromatin, and the regulation of accessibility of the donor sequences. Real-time analysis of MAT switching has provided the most detailed description of the molecular events that occur during the homologous recombinational repair of a programmed double-strand chromosome break. PMID:22555442

  15. Alaska's Living Tundra. Alaska Wildlife Week, 25-29 April 1988. Unit 6: Primary Teacher's Guide; Upper Elementary Teacher's Guide; Junior/Senior High School Teacher's Guide; Supplement.

    ERIC Educational Resources Information Center

    Quinlan, Susan E.

    Despite its cold and barren appearance, Alaska's tundra supports a surprising variety of insects, birds, and mammals. In this document, three teacher's guides (for primary, upper elementary, and junior and senior high schools) and a supplementary resource packet present a comprehensive unit of study on Alaska's living tundra. The five lessons in…

  16. Dynamics of the recovery of damaged tundra vegetation: preliminary results of revegetation experiments of maritime tundra with Elymus mollis on Adak Island, Alaska. Progress report

    SciTech Connect

    Amundsen, C C; McCord, R A

    1982-08-01

    The vegetation of the central Aleutian Islands, Alaska is maritime tundra (Amundsen, 1977). While maritime tundra is not characterized by the presence of permafrost, the soil temperatures remain low (5 to 7/sup 0/C) year-round (Williams, 1980). The low soil temperature, a high level of soil moisture, and a low level of incident solar radiation are thought to delay the development of the vegetation. Natural revegetation of natural or man made open areas is relatively slow. Disturbed areas from World War II military activity are not completely revegetated after almost 40 years. Because of the windy and wet climate of the region, exposed soil is unstable and subject to extensive freeze-thaw action and erosion. Insults to the vegetation, both marine and aeolian, are common. Successful reproduction by seed is uncommon among species of this flora. The primary means of reproduction appears to be by vegetative propagules which are usually fragments of the shoot and rhizome. While the transport of the fragments by wind and water aids in the dispersal of the propagules, the same action often removes these fragments from open areas. This later activity further delays the revegetation of open and disturbed areas. Elymus mollis Trin. is the most successful major native species found to date as it fragments due to wind and water action and transplants easily. Transplanting experiments with sprigs of Elymus mollis Trin. have been conducted on Adak Island, Alaska since 1977. Preliminary results indicate that Elymus mollis may be transplanted for revegetation with a survival rate of at least 90 percent. Experiments were set up in 1979 to determine appropriate planting density, sprig rhizome length, and best time of year for transplanting. Preliminary results for these experiments are reported here.

  17. Viruses Occur Incorporated in Biogenic High-Mg Calcite from Hypersaline Microbial Mats.

    PubMed

    De Wit, Rutger; Gautret, Pascale; Bettarel, Yvan; Roques, Cécile; Marlière, Christian; Ramonda, Michel; Nguyen Thanh, Thuy; Tran Quang, Huy; Bouvier, Thierry

    2015-01-01

    Using three different microscopy techniques (epifluorescence, electronic and atomic force microscopy), we showed that high-Mg calcite grains in calcifying microbial mats from the hypersaline lake "La Salada de Chiprana", Spain, contain viruses with a diameter of 50-80 nm. Energy-dispersive X-ray spectrometer analysis revealed that they contain nitrogen and phosphorus in a molar ratio of ~9, which is typical for viruses. Nucleic acid staining revealed that they contain DNA or RNA. As characteristic for hypersaline environments, the concentrations of free and attached viruses were high (>10(10) viruses per g of mat). In addition, we showed that acid treatment (dissolution of calcite) resulted in release of viruses into suspension and estimated that there were ~15 × 10(9) viruses per g of calcite. We suggest that virus-mineral interactions are one of the possible ways for the formation of nano-sized structures often described as "nanobacteria" and that viruses may play a role in initiating calcification. PMID:26115121

  18. Disks solid phase extraction based polypyrrole functionalized core-shell nanofibers mat.

    PubMed

    Qi, FeiFei; Li, XiaoQing; Yang, BiYi; Rong, Fei; Xu, Qian

    2015-11-01

    A novel disks solid phase extraction (SPE) based on polypyrrole (PPy) functionalized core-shell electrospun nanofibers mat was proposed. The performance of the established disks SPE technique was evaluated in the extraction of trace polar analytes from environmental water samples. Disulphonated (acid yellow 9) and monosulphonated azo dyes (acid orange 7 and metanil yellow) were selected as typical model analytes. Under the optimum conditions, detection limits were 0.15-0.3 μg/L for all target analytes and the enrichment coefficients were 106-121. The recoveries of sulfonated azo dyes added to typical environmental water samples were 87.6-112.3%, suggesting that the interferences of the sample matrix did not affect the enrichment. Compared with existing methods, the device in this study showed higher recovery, lower detection limit and better precision. Moreover, the miniaturized disks SPE technique for sample preparation is simple and fast, with significantly reduced sorbent bed mass (2.5 mg) and eluent volume (500 μL). These results indicate that PPy nanofibers mat-based disks SPE may be a promising device that can effectively extract the polar species in water samples. PMID:26452802

  19. Viruses Occur Incorporated in Biogenic High-Mg Calcite from Hypersaline Microbial Mats

    PubMed Central

    De Wit, Rutger; Gautret, Pascale; Bettarel, Yvan; Roques, Cécile; Marlière, Christian; Ramonda, Michel; Nguyen Thanh, Thuy; Tran Quang, Huy; Bouvier, Thierry

    2015-01-01

    Using three different microscopy techniques (epifluorescence, electronic and atomic force microscopy), we showed that high-Mg calcite grains in calcifying microbial mats from the hypersaline lake “La Salada de Chiprana”, Spain, contain viruses with a diameter of 50–80 nm. Energy-dispersive X-ray spectrometer analysis revealed that they contain nitrogen and phosphorus in a molar ratio of ~9, which is typical for viruses. Nucleic acid staining revealed that they contain DNA or RNA. As characteristic for hypersaline environments, the concentrations of free and attached viruses were high (>1010 viruses per g of mat). In addition, we showed that acid treatment (dissolution of calcite) resulted in release of viruses into suspension and estimated that there were ~15 × 109 viruses per g of calcite. We suggest that virus-mineral interactions are one of the possible ways for the formation of nano-sized structures often described as “nanobacteria” and that viruses may play a role in initiating calcification. PMID:26115121

  20. Optimizing burn severity assessments in Alaskan tussock tundra from optical imagery

    NASA Astrophysics Data System (ADS)

    Loboda, T. V.; Jenkins, L. K.; French, N. H.; Bourgeau-Chavez, L. L.

    2013-12-01

    Over the past decade Alaskan tundra has experienced an increase in fire occurrence prompting rising concerns in the scientific community. Fire occurrence in tundra ecosystems has the potential to release a large amount of organic carbon stored in the deep organic layer, modify soil moisture and respiration, and make more organic matter available for decomposition and future burning through impacts on the active depth layer. Monitoring and characterization of fire occurrence and impacts in extensive, remote, and largely inaccessible tundra regions rely on satellite observations of land surface and require robust approaches to burn severity measurements. The relatively low fire activity in tundra regions between 1950 and 2000 has resulted in overall lack of understanding of fire impacts on tundra landscapes outside the Seward Peninsula where tundra fire record is better known. Thus satellite-based mapping of burn severity is limited by the lack of quantified knowledge of fire-induced physical changes on the landscape on the one hand and the capabilities of optical remote sensing systems to capture those characteristics on the other. Here we present an analysis of satellite mapping of burn severity using multi-date Landsat imagery and two field-based measurements of burn severity - the operationally applied Composite Burn Index (CBI) and the more simplistic Burn Severity Index (BSI), also known as the Burn Severity Code Matrix. The BSI used here is a four-point scale (unburned, low, moderate, severe) assessed for the surface substrate and vegetation layers. The BSI and CBI used to compare to the remote sensing data were determined from the field data by converting the qualitative fractional assessment of burn severity within 10 x 10 m plots to a single value. Since both indices represent mostly ocular assessment of the fire-impacted surface, they can relate well to Landsat's optical sensors measurements. The analysis shows that overall satellite indices have closer

  1. Constraining predictions of tundra permafrost and vegetation through model-data feedbacks and data-assimilation

    NASA Astrophysics Data System (ADS)

    Davidson, C. D.; Dietze, M.

    2011-12-01

    Arctic climate is warming at a rate disproportionate to the rest of the world, and recent interest has emerged in using terrestrial biosphere models to understand and predict the response of tundra ecosystems to such warming. Of particular interest are the potential feedbacks between permafrost melting, plant community dynamics, and biogeochemical cycles. Here, we report on efforts to calibrate and validate version 2 of the Ecosystem Demography model (ED2) for the Alaskan tundra and on the use of model analyses to motivate targeted field measurements. ED2 is a terrestrial biosphere model unique in its ability to scale physiological and plant community dynamics to regional levels. We began by assessing the ability of ED2's land surface model to capture permafrost thermodynamics and hydrology. Simulations at Barrow and Toolik Lake, Alaska bore several incongruities with observed data, with soil temperatures significantly higher and soil moisture lower than observed. Modifications were made to increase the soil column depth and to simulate the effect of wind compaction on snow density, and in turn, the insulation of winter soils. In addition to these changes, a new soil class was created to represent unique characteristics within the organic horizon of tundra soils. Together these changes significantly improved permafrost dynamics without substantially altering dynamics in the temperate region. To capture tundra vegetation dynamics, tundra species were classified into three plant functional types (graminoid, deciduous shrub, evergreen shrub). ED2 was then iteratively calibrated for the tundra using the Predictive Ecosystem Analyzer (PEcAn), a scientific workflow and ecoinformatics toolbox developed to aid model parameterization and analysis. Initial parameter estimates were derived from a formal Bayesian meta-analysis of compiled plant trait data. Sensitivity analyses and variance decomposition demonstrated that model uncertainties were driven by the minimum

  2. Community structure of a microbial mat: the phylogenetic dimension.

    PubMed Central

    Risatti, J B; Capman, W C; Stahl, D A

    1994-01-01

    Traditional studies of microbial communities are incomplete because of the inability to identify and quantify all contributing populations. In the present study, we directly determine the abundance and distribution of sulfate-reducing bacterial populations in a microbial mat community by using hybridization probes complementary to the 16S-like rRNAs of major phylogenetic groups. Most of the major groups were found in this single community, distributed for the most part in nonoverlapping depth intervals of the mat. The reflection of the phylogenetic structure in the community structure suggests that those species making up the major phylogenetic groups perform specific interrelated metabolic functions in the community. Comparison of population profiles to previously observed rates of sulfate reduction suggests there are additional populations of sulfate-reducing bacteria both within the photooxic zone and deeper in the mat. Images PMID:7937858

  3. Controlled release of dual drugs from emulsion electrospun nanofibrous mats.

    PubMed

    Yan, Su; Xiaoqiang, Li; Shuiping, Liu; Xiumei, Mo; Ramakrishna, Seeram

    2009-10-15

    The purpose of this work is to develop a novel type of tissue engineering scaffold or drugs delivery carrier with the capability of encapsulation and controlled release drugs. In this study, Rhodamine B and Bovine Serum Albumin (BSA) were successfully incorporated into nanofibers by means of emulsion electrospinning. The morphology of composite nanofibers was studied by Scanning Electron Microscopy (SEM). The composite nanofibrous mats made from emulsion electrospinning were characterized by water contact angle measurement and X-ray diffraction. In vitro dual drugs release behaviors from composite nanofibrous mats were investigated. The results indicated that the incorporated drug and/or proteins in composite fibrous mats made from electrospinning could be control released by adjusting the processes of emulsions preparation. PMID:19586756

  4. Community structure of a microbial mat: The phylogenetic dimension

    USGS Publications Warehouse

    Risatti, J.B.; Capman, W.C.; Stahl, D.A.

    1994-01-01

    Traditional studies of microbial communities are incomplete because of the inability to identify and quantify all contributing populations. In the present study, we directly determine the abundance and distribution of sulfate-reducing bacterial populations in a microbial mat community by using hybridization probes complementary to the 16S-like rRNAs of major phylogenetic groups. Most of the major groups were found in this single community, distributed for the most part in nonoverlapping depth intervals of the mat. The reflection of the phylogenetic structure in the community structure suggests that those species making up the major phylogenetic groups perform specific interrelated metabolic functions in the community. Comparison of population profiles to previously observed rates of sulfate reduction suggests there are additional populations of sulfate-reducing bacteria both within the photooxic zone and deeper in the mat.

  5. The MATS Satellite Mission - Tomographic Perspectives on the Mesosphere

    NASA Astrophysics Data System (ADS)

    Karlsson, B.; Gumbel, J.

    2015-12-01

    Tomography in combination with space-borne limb imaging opens exciting new ways of probing atmospheric structures. MATS (Mesospheric Airglow/Aerosol Tomography and Spectroscopy) is a new Swedish satellite mission that applies these ideas to the mesosphere. MATS science questions focus on mesospheric wave activity and noctilucent clouds. Primary measurement targets are O2 Atmospheric band dayglow and nightglow in the near infrared (759-767 nm) and sunlight scattered from noctilucent clouds in the ultraviolet (270-300 nm). While tomography provides horizontally and vertically resolved data, spectroscopy allows analysis in terms of mesospheric composition, temperature and cloud properties. This poster introduces instrument and analysis ideas, and discusses scientific perspectives and connections to other missions. MATS is being prepared for a launch in 2018.

  6. Pressure Mapping Mat for Tele-Home Care Applications

    PubMed Central

    Saenz-Cogollo, Jose Francisco; Pau, Massimiliano; Fraboni, Beatrice; Bonfiglio, Annalisa

    2016-01-01

    In this paper we present the development of a mat-like pressure mapping system based on a single layer textile sensor and intended to be used in home environments for monitoring the physical condition of persons with limited mobility. The sensor is fabricated by embroidering silver-coated yarns on a light cotton fabric and creating pressure-sensitive resistive elements by stamping the conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) at the crossing points of conductive stitches. A battery-operated mat prototype was developed and includes the scanning circuitry and a wireless communication module. A functional description of the system is presented together with a preliminary experimental evaluation of the mat prototype in the extraction of plantar pressure parameters. PMID:26978369

  7. Community structure of a microbial mat: the phylogenetic dimension.

    PubMed

    Risatti, J B; Capman, W C; Stahl, D A

    1994-10-11

    Traditional studies of microbial communities are incomplete because of the inability to identify and quantify all contributing populations. In the present study, we directly determine the abundance and distribution of sulfate-reducing bacterial populations in a microbial mat community by using hybridization probes complementary to the 16S-like rRNAs of major phylogenetic groups. Most of the major groups were found in this single community, distributed for the most part in nonoverlapping depth intervals of the mat. The reflection of the phylogenetic structure in the community structure suggests that those species making up the major phylogenetic groups perform specific interrelated metabolic functions in the community. Comparison of population profiles to previously observed rates of sulfate reduction suggests there are additional populations of sulfate-reducing bacteria both within the photooxic zone and deeper in the mat. PMID:7937858

  8. [Laboratory analogs of cyanobacterial mats of the alkaline geochemical barrier].

    PubMed

    Zavarzin, G A; Orleanskiĭ, V K; Gerasimenko, L M; Pushko, S N; Ushatinskaia, G T

    2003-01-01

    The goal of this work was to illustrate a possible interaction between the "soda continent" and the ocean. A laboratory simulation was undertaken of the development of alkaliphilic mat with calcium carbonate and calcium phosphate interlayers in the zone where ocean waters, containing calcium and manganese, come into contact with carbonate- and phosphate-rich alkaline waters. The macrostructure of the layered cyanobacterial mat turned out to little dependent on the chemical conditions causing sediment formation. The chemical composition of freshly formed mineral interlayers of the mat was found to vary with the medium composition. The mineralogical composition of the sediment is determined by diagenesis conditions in its depth, which can cause mineral phase conversions. PMID:12698798

  9. Lead toxicosis in tundra swans near a mining and smelting complex in northern Idaho.

    PubMed

    Blus, L J; Henny, C J; Hoffman, D J; Grove, R A

    1991-11-01

    Die-offs of waterfowl have occurred in the Coeur d'Alene River system in northern Idaho since at least the early 1900's. We investigated causes of mortality and lead and cadmium contamination of 46 tundra swans (Cygnus columbianus) from 1987 to 1989; an additional 22 swans found dead in 1990 were not examined. We necropsied 43 of the 46 birds found from 1987 to 1989; 38 of these were from the Coeur d'Alene River system, which has been contaminated with mining and smelting wastes for a century, and the other 5 were from a nearby, relatively uncontaminated area. Of the 36 livers of swans from the contaminated area that were analyzed, 32 contained lethal levels of lead (6 to 40 micrograms/g, wet weight) and all birds exhibited several symptoms of lead poisoning, notably enlarged gall bladders containing viscous, dark-green bile. Only 13% of the lead-poisoned birds (10% when data were included from other studies of swans in the area) contained shot, compared to 95% of lead-poisoning swans in studies outside northern Idaho. Lead concentrations in blood samples from 16 apparently healthy swans (0.5 to 2.3 micrograms/g, and 4 lead-poisoned birds found moribund (1.3 to 9.6 micrograms/g) indicating that tundra swans accumulated high levels of lead from ingestion of sediment that contained up to 8,700 micrograms/g of lead and plants that contained up to 400 micrograms/g. The swans spend only a few weeks in the area staging during the spring migration. The five tundra swans from the uncontaminated area had low levels of lead and essentially no symptoms of lead poisoning.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1759849

  10. Nitrogen accumulation and partitioning in a High Arctic tundra ecosystem from extreme atmospheric N deposition events.

    PubMed

    Choudhary, Sonal; Blaud, Aimeric; Osborn, A Mark; Press, Malcolm C; Phoenix, Gareth K

    2016-06-01

    Arctic ecosystems are threatened by pollution from recently detected extreme atmospheric nitrogen (N) deposition events in which up to 90% of the annual N deposition can occur in just a few days. We undertook the first assessment of the fate of N from extreme deposition in High Arctic tundra and are presenting the results from the whole ecosystem (15)N labelling experiment. In 2010, we simulated N depositions at rates of 0, 0.04, 0.4 and 1.2 g Nm(-2)yr(-1), applied as (15)NH4(15)NO3 in Svalbard (79(°)N), during the summer. Separate applications of (15)NO3(-) and (15)NH4(+) were also made to determine the importance of N form in their retention. More than 95% of the total (15)N applied was recovered after one growing season (~90% after two), demonstrating a considerable capacity of Arctic tundra to retain N from these deposition events. Important sinks for the deposited N, regardless of its application rate or form, were non-vascular plants>vascular plants>organic soil>litter>mineral soil, suggesting that non-vascular plants could be the primary component of this ecosystem to undergo measurable changes due to N enrichment from extreme deposition events. Substantial retention of N by soil microbial biomass (70% and 39% of (15)N in organic and mineral horizon, respectively) during the initial partitioning demonstrated their capacity to act as effective buffers for N leaching. Between the two N forms, vascular plants (Salix polaris) in particular showed difference in their N recovery, incorporating four times greater (15)NO3(-) than (15)NH4(+), suggesting deposition rich in nitrate will impact them more. Overall, these findings show that despite the deposition rates being extreme in statistical terms, biologically they do not exceed the capacity of tundra to sequester pollutant N during the growing season. Therefore, current and future extreme events may represent a major source of eutrophication. PMID:26956177

  11. Twenty year record of vegetation change from long-term plots in Alaskan tundra

    NASA Astrophysics Data System (ADS)

    Gould, W. A.; Mercado Díaz, J. A.

    2008-12-01

    We examined change in plant species composition at two sites in the Southern Alaska Foothills, on the north slope of the Brooks Range, over a 20-year period. Current models and experimental work with tundra vegetation have predicted an increase in shrub species and a decrease in graminoid species as a response to climatic warming. Furthermore, the warming of the Alaskan Arctic during the past 150 years has accelerated over the last three decades and is expected to increase vegetation productivity in tundra if shrubs become more abundant. Decadal change in vegetation in tundra landscapes may be both subtle and slow. Interpreting such change is complicated by spatial variation at small scales and by difficulty in understanding how point changes in species composition relate to landscape-level change in vegetation. Our approach involved resampling the same points in a series of permanent plots over a multi-year interval, using large sample sizes, and analyzing several aspects of compositional change. Our analysis was designed to look at changes in overall species' abundance over time and at relationships between species in terms of the likelihood of one species replacing another. Understanding relationships between species increases the predictive power of measures of species composition and abundance in a time series. We found significant increases in abundance of specific shrub and graminoid species, and a general increase in the extent of the canopy, with a concurrent decrease in the abundance of understory mosses. These changes, extrapolated over the broad expanse of similar vegetation in the Arctic, may have profound above and below ground effects including changes in soil properties, carbon storage and nutrient cycling, and plant community composition.

  12. The impacts of thawing permafrost on tundra lakes, Mackenzie Delta region, NWT, Canada. (Invited)

    NASA Astrophysics Data System (ADS)

    Kokelj, S.; Thompson, M. S.; Lantz, T.; Thienpont, J.; Pisaric, M. F.; Smol, J. P.; Blais, J.; Zajdlik, B.

    2009-12-01

    Many arctic regions with abundant lakes and ponds are characterized by ice-rich terrain sensitive to thermokarst disturbance. In the Mackenzie Delta region, retrogressive thaw slumps commonly develop adjacent to tundra lakes and may impact several hectares of terrain. The numbers, size and growth rates of slumps have increased significantly since the 1970s with rising air and permafrost temperatures. To examine the chemical effects of thawing permafrost on lake water quality we assessed water chemistry for large number of slump-disturbed and undisturbed lakes across tundra uplands in the Mackenzie Delta region. The environmental factors typically evoked to explain variation in tundra lake water quality, including surficial geology and proximity to the treeline or to the coast, were subordinate to the main driver, permafrost degradation. Thaw slump-affected lakes had elevated ionic concentrations and water clarity in comparison with undisturbed lakes. The strength of the ionic impact was positively associated with the proportion of catchment affected by slumping and inversely related to disturbance age. We also found that fire-induced active-layer deepening had a detectable influence on lake water ionic strength. Preliminary evidence suggests sedimentary diatom assemblages track the changes in chemical and physical limnology coincident with the timing of thermokarst slumping, and thus, may prove a valuable tool for inferring changes at the base of the aquatic food web in these lakes. In a warming arctic, we can anticipate that thermokarst processes will increase in importance as a driver of ionic chemistry and optical properties of small lakes and ponds with potential to alter aquatic food webs.

  13. Phytomass patterns across a temperature gradient of the North American arctic tundra

    NASA Astrophysics Data System (ADS)

    Epstein, Howard E.; Walker, Donald A.; Raynolds, Martha K.; Jia, Gensuo J.; Kelley, Alexia M.

    2008-09-01

    Only a few studies to date have collectively examined the vegetation biomass and production of arctic tundra ecosystems and their relationships to broadly ranging climate variables. An additional complicating factor for studying vegetation of arctic tundra is the high spatial variability associated with small patterned-ground features, resulting from intense freeze-thaw processes. In this study, we sampled and analyzed the aboveground plant biomass components of patterned-ground ecosystems in the Arctic of northern Alaska and Canada along an 1800-km north-south gradient that spans approximately 11°C of mean July temperatures. Vegetation biomass was analyzed as functions of the summer warmth index (SWI-sum of mean monthly temperatures > 0°C). The total absolute biomass (g m-2) and biomass of shrubs increased monotonically with SWI, however, biomass of nonvascular species (mosses and lichens), were a parabolic function of SWI, with greatest values at the ends of the gradient. The components of plant biomass on patterned-ground features (i.e., on nonsorted circles or within small polygons) were constrained to a greater degree with colder climate than undisturbed tundra, likely due to the effect of frost heave disturbances on the vegetation. There were also clear differences in the relative abundances of vascular versus nonvascular plants on and off patterned-ground features along the SWI gradient. The spatial patterns of biomass differ among plant functional groups and suggest that plant community responses to temperature, and land-surface processes that produce patterned-ground features, are quite complex.

  14. Molecular detection of Setaria tundra (Nematoda: Filarioidea) and an unidentified filarial species in mosquitoes in Germany

    PubMed Central

    2012-01-01

    Background Knowledge of the potential vector role of Culicidae mosquitoes in Germany is very scanty, and until recently it was generally assumed that they are not involved in the transmission of anthroponotic or zoonotic pathogens in this country. However, anticipated changes in the course of global warming and globalization may alter their status. Methods We conducted a molecular mass screening of mosquitoes for filarial parasites using mitochondrial 12S rRNA-based real-time PCR. Results No parasites causing disease in humans such as Dirofilaria spp. were detected in about 83,000 mosquitoes tested, which had been collected in 2009 and 2010 in 16 locations throughout Germany. However, minimum infection rates of up to 24 per 1000 mosquitoes were revealed, which could be attributed to mosquito infection with Setaria tundra and a yet unidentified second parasite. Setaria tundra was found to be widespread in southern Germany in various mosquito species, except Culex spp. In contrast, the unidentified filarial species was exclusively found in Culex spp. in northern Baden-Württemberg, and is likely to be a bird parasite. Conclusions Although dirofilariasis appears to be emerging and spreading in Europe, the absence of Dirofilaria spp. or other zoonotic filariae in our sample allows the conclusion that the risk of autochthonous infection in Germany is still very low. Potential vectors of S. tundra in Germany are Ochlerotatus sticticus, Oc. cantans, Aedes vexans and Anopheles claviger. Technically, the synergism between entomologists, virologists and parasitologists, combined with state-of-the-art methods allows a very efficient near-real-time monitoring of a wide spectrum of both human and veterinary pathogens, including new distribution records of parasite species and the incrimination of their potential vectors. PMID:22236560

  15. Permafrost thaw and soil moisture driving CO2 and CH4 release from upland tundra

    NASA Astrophysics Data System (ADS)

    Natali, Susan M.; Schuur, Edward A. G.; Mauritz, Marguerite; Schade, John D.; Celis, Gerardo; Crummer, Kathryn G.; Johnston, Catherine; Krapek, John; Pegoraro, Elaine; Salmon, Verity G.; Webb, Elizabeth E.

    2015-03-01

    As permafrost degrades, the amount of organic soil carbon (C) that thaws during the growing season will increase, but decomposition may be limited by saturated soil conditions common in high-latitude ecosystems. However, in some areas, soil drying is expected to accompany permafrost thaw as a result of increased water drainage, which may enhance C release to the atmosphere. We examined the effects of ecosystem warming, permafrost thaw, and soil moisture changes on C balance in an upland tundra ecosystem. This study was conducted at a water table drawdown experiment, established in 2011 and located within the Carbon in Permafrost Experimental Heating Research project, an ecosystem warming and permafrost thawing experiment in Alaska. Warming and drying increased cumulative growing season ecosystem respiration by ~20% over 3 years of this experiment. Warming caused an almost twofold increase in decomposition of a common substrate in surface soil (0-10 cm) across all years, and drying caused a twofold increase in decomposition (0-20 cm) relative to control after 3 years of drying. Decomposition of older C increased in the dried and in the combined warmed + dried plots based on soil pore space 14CO2. Although upland tundra systems have been considered CH4 sinks, warming and ground thaw significantly increased CH4 emission rates. Water table depth was positively correlated with monthly respiration and negatively correlated with CH4 emission rates. These results demonstrate that warming and drying may increase loss of old permafrost C from tundra ecosystems, but the form and magnitude of C released to the atmosphere will be driven by changes in soil moisture.

  16. Arctic Tundra Vegetation Functional Types Based on Photosynthetic Physiology and Optical Properties

    NASA Technical Reports Server (NTRS)

    Huemmrich, Karl F.; Gamon, John; Tweedie, Craig; Campbell, Petya P. K.; Landis, David; Middleton, Elizabeth

    2012-01-01

    Climate change in tundra regions may alter vegetation species composition and ecosystem carbon balance. Remote sensing provides critical tools for monitoring these changes as optical signals provide a way to scale from plot measurements to regional patterns. Gas exchange measurements of pure patches of key vegetation functional types (lichens, mosses, and vascular plants) in sedge tundra at Barrow AK, show three significantly different values of light use efficiency (LUE) with values of 0.013+/-0.001, 0.0018+/-0.0002, and 0.0012 0.0001 mol C/mol absorbed quanta for vascular plants, mosses and lichens, respectively. Further, discriminant analysis of patch reflectance identifies five spectral bands that can separate each vegetation functional type as well as nongreen material (bare soil, standing water, and dead leaves). These results were tested along a 100 m transect where midsummer spectral reflectance and vegetation coverage were measured at one meter intervals. Area-averaged canopy LUE estimated from coverage fractions of the three functional types varied widely, even over short distances. Patch-level statistical discriminant functions applied to in situ hyperspectral reflectance successfully unmixed cover fractions of the vegetation functional types. These functions, developed from the tram data, were applied to 30 m spatial resolution Earth Observing-1 Hyperion imaging spectrometer data to examine regional variability in distribution of the vegetation functional types and from those distributions, the variability of LUE. Across the landscape, there was a fivefold variation in tundra LUE that was correlated to a spectral vegetation index developed to detect vegetation chlorophyll content.

  17. Tall shrub and tree expansion in Siberian tundra ecotones since the 1960s.

    PubMed

    Frost, Gerald V; Epstein, Howard E

    2014-04-01

    Circumpolar expansion of tall shrubs and trees into Arctic tundra is widely thought to be occurring as a result of recent climate warming, but little quantitative evidence exists for northern Siberia, which encompasses the world's largest forest-tundra ecotonal belt. We quantified changes in tall shrub and tree canopy cover in 11, widely distributed Siberian ecotonal landscapes by comparing very high-resolution photography from the Cold War-era 'Gambit' and 'Corona' satellite surveillance systems (1965-1969) with modern imagery. We also analyzed within-landscape patterns of vegetation change to evaluate the susceptibility of different landscape components to tall shrub and tree increase. The total cover of tall shrubs and trees increased in nine of 11 ecotones. In northwest Siberia, alder (Alnus) shrubland cover increased 5.3-25.9% in five ecotones. In Taymyr and Yakutia, larch (Larix) cover increased 3.0-6.7% within three ecotones, but declined 16.8% at a fourth ecotone due to thaw of ice-rich permafrost. In Chukotka, the total cover of alder and dwarf pine (Pinus) increased 6.1% within one ecotone and was little changed at a second ecotone. Within most landscapes, shrub and tree increase was linked to specific geomorphic settings, especially those with active disturbance regimes such as permafrost patterned-ground, floodplains, and colluvial hillslopes. Mean summer temperatures increased at most ecotones since the mid-1960s, but rates of shrub and tree canopy cover expansion were not strongly correlated with temperature trends and were better correlated with mean annual precipitation. We conclude that shrub and tree cover is increasing in tundra ecotones across most of northern Siberia, but rates of increase vary widely regionally and at the landscape scale. Our results indicate that extensive changes can occur within decades in moist, shrub-dominated ecotones, as in northwest Siberia, while changes are likely to occur much more slowly in the highly continental

  18. Molecular detection of Dirofilaria immitis, Dirofilaria repens and Setaria tundra in mosquitoes from Germany

    PubMed Central

    2014-01-01

    Background As a result of globalization and climate change, Dirofilaria immitis and Dirofilaria repens, the causative agents of dirofilariosis in Europe, continue to spread from endemic areas in the Mediterranean to northern and northeastern regions of Europe where autochthonous cases of dirofilarial infections have increasingly been observed in dogs and humans. Whilst D. repens was recently reported from mosquitoes in putatively non-endemic areas, D. immitis has never been demonstrated in mosquitoes from Europe outside the Mediterranean. Methods From 2011 to 2013, mosquitoes collected within the framework of a German national mosquito monitoring programme were screened for filarial nematodes using a newly designed filarioid-specific real-time PCR assay. Positive samples were further processed by conventional PCR amplification of the cytochrome c oxidase subunit I (COI) gene, amplicons were sequenced and sequences blasted against GenBank. Results Approximately 17,000 female mosquitoes were subjected to filarial screening. Out of 955 pools examined, nine tested positive for filariae. Two of the COI sequences indicated D. immitis, one D. repens and four Setaria tundra. Two sequences could not be assigned to a known species due to a lack of similar GenBank entries. Whilst D. immitis and the unknown parasites were detected in Culex pipiens/torrentium, D. repens was found in a single Anopheles daciae and all S. tundra were demonstrated in Aedes vexans. All positive mosquitoes were collected between mid-June and early September. Conclusion The finding of dirofilariae in German mosquitoes implies the possibility of a local natural transmission cycle. While the routes of introduction to Germany and the origin of the filariae cannot be determined retrospectively, potential culicid vectors and reservoir hosts must prospectively be identified and awareness among physicians, veterinarians and public health personnel be created. The health impact of S. tundra on the indigenous

  19. Radiation budget and soil heat fluxes in different Arctic tundra vegetation types

    NASA Astrophysics Data System (ADS)

    Juszak, Inge; Iturrate Garcia, Maitane; Gastellu-Etchegorry, Jean-Philippe; Schaepman, Michael E.; Schaepman-Strub, Gabriela

    2016-04-01

    While solar radiation is one of the primary energy sources for warming and thawing permafrost soil, the amount of shortwave radiation reaching the soil is reduced by vegetation shading. Climate change has led to greening, shrub expansion and encroachment in many Arctic tundra regions and further changes are anticipated. These vegetation changes feed back to the atmosphere and permafrost as they modify the surface energy budget. However, canopy transmittance of solar radiation has rarely been measured or modelled for a variety of tundra vegetation types. We assessed the radiation budget of the most common vegetation types at the Kytalyk field site in North-East Siberia (70.8°N, 147.5°E) with field measurements and 3D radiative transfer modelling and linked it to soil heat fluxes. Our results show that Arctic tundra vegetation types differ in canopy albedo and transmittance as well as in soil heat flux and active layer thickness. Tussock sedges transmitted on average 56% of the incoming light and dwarf shrubs 27%. For wet sedges we found that the litter layer was very important as it reduced the average transmittance to only 6%. Model output indicated that both, albedo and transmittance, also depend on the spatial aggregation of vegetation types. We found that permafrost thaw was more strongly related to soil properties than to canopy shading. The presented radiative transfer model allows quantifying effects of the vegetation layer on the surface radiation budget in permafrost areas. The parametrised model can account for diverse vegetation types and variation of properties within types. Our results highlight small scale radiation budget and permafrost thaw variability which are indicated and partly caused by vegetation. As changes in species composition and biomass increase can influence thaw rates, small scale patterns should be considered in assessments of climate-vegetation-permafrost feedbacks.

  20. Phylogenetic stratigraphy in the Guerrero Negro hypersaline microbial mat

    PubMed Central

    Kirk Harris, J; Gregory Caporaso, J; Walker, Jeffrey J; Spear, John R; Gold, Nicholas J; Robertson, Charles E; Hugenholtz, Philip; Goodrich, Julia; McDonald, Daniel; Knights, Dan; Marshall, Paul; Tufo, Henry; Knight, Rob; Pace, Norman R

    2013-01-01

    The microbial mats of Guerrero Negro (GN), Baja California Sur, Mexico historically were considered a simple environment, dominated by cyanobacteria and sulfate-reducing bacteria. Culture-independent rRNA community profiling instead revealed these microbial mats as among the most phylogenetically diverse environments known. A preliminary molecular survey of the GN mat based on only ∼1500 small subunit rRNA gene sequences discovered several new phylum-level groups in the bacterial phylogenetic domain and many previously undetected lower-level taxa. We determined an additional ∼119 000 nearly full-length sequences and 28 000 >200 nucleotide 454 reads from a 10-layer depth profile of the GN mat. With this unprecedented coverage of long sequences from one environment, we confirm the mat is phylogenetically stratified, presumably corresponding to light and geochemical gradients throughout the depth of the mat. Previous shotgun metagenomic data from the same depth profile show the same stratified pattern and suggest that metagenome properties may be predictable from rRNA gene sequences. We verify previously identified novel lineages and identify new phylogenetic diversity at lower taxonomic levels, for example, thousands of operational taxonomic units at the family-genus levels differ considerably from known sequences. The new sequences populate parts of the bacterial phylogenetic tree that previously were poorly described, but indicate that any comprehensive survey of GN diversity has only begun. Finally, we show that taxonomic conclusions are generally congruent between Sanger and 454 sequencing technologies, with the taxonomic resolution achieved dependent on the abundance of reference sequences in the relevant region of the rRNA tree of life. PMID:22832344

  1. Microsensor measurements of hydrogen gas dynamics in cyanobacterial microbial mats

    PubMed Central

    Nielsen, Michael; Revsbech, Niels P.; Kühl, Michael

    2015-01-01

    We used a novel amperometric microsensor for measuring hydrogen gas production and consumption at high spatio-temporal resolution in cyanobacterial biofilms and mats dominated by non-heterocystous filamentous cyanobacteria (Microcoleus chtonoplastes and Oscillatoria sp.). The new microsensor is based on the use of an organic electrolyte and a stable internal reference system and can be equipped with a chemical sulfide trap in the measuring tip; it exhibits very stable and sulfide-insensitive measuring signals and a high sensitivity (1.5–5 pA per μmol L-1 H2). Hydrogen gas measurements were done in combination with microsensor measurements of scalar irradiance, O2, pH, and H2S and showed a pronounced H2 accumulation (of up to 8–10% H2 saturation) within the upper mm of cyanobacterial mats after onset of darkness and O2 depletion. The peak concentration of H2 increased with the irradiance level prior to darkening. After an initial build-up over the first 1–2 h in darkness, H2 was depleted over several hours due to efflux to the overlaying water, and due to biogeochemical processes in the uppermost oxic layers and the anoxic layers of the mats. Depletion could be prevented by addition of molybdate pointing to sulfate reduction as a major sink for H2. Immediately after onset of illumination, a short burst of presumably photo-produced H2 due to direct biophotolysis was observed in the illuminated but anoxic mat layers. As soon as O2 from photosynthesis started to accumulate, the H2 was consumed rapidly and production ceased. Our data give detailed insights into the microscale distribution and dynamics of H2 in cyanobacterial biofilms and mats, and further support that cyanobacterial H2 production can play a significant role in fueling anaerobic processes like e.g., sulfate reduction or anoxygenic photosynthesis in microbial mats. PMID:26257714

  2. Neurospora crassa mat A-2 and mat A-3 proteins weakly interact in the yeast two-hybrid system and affect yeast growth

    PubMed Central

    2009-01-01

    Mating-type genes control the entry into the sexual cycle, mating identity and sexual development in fungi. The mat A-2 and mat A-3 genes, present in the mat A idiomorph of the filamentous fungus Neurospora crassa, are required for post-fertilization functions but are not essential for mating identity. Their putative roles as transcription factors are based on the similarity of mat A-2 with the Podospora anserina SMR1 gene and an HMG motif present in the mat A-3 gene. In this work the yeast two-hybrid system was used to identify transcriptional activity and protein-protein interaction of N. crassamat A-2 and mat A-3 genes. We observed that the mat A-3 protein alone is capable of weakly activating transcription of yeast reporter genes; it also binds with low specificity to the GAL1 promoter sequence, possibly due to its HMG domain. Our results also indicate that mat A-3 is capable to form homodimers, and interact with mat A-2. Interference on yeast growth was observed on some transformants suggesting a toxic action of the mat A-2 protein. Our data on pattern of interactions of mat proteins contributes towards understanding the control of vegetative and sexual cycles in filamentous fungi. PMID:21637691

  3. The heterothallic sugarbeet pathogen Cercospora beticola contains exon fragments of both MAT genes that are homogenized by concerted evolution

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dothideomycetes is one of the most ecologically diverse and economically important classes of fungi. Sexual reproduction in this group is governed by mating type (MAT) genes at the MAT1 locus. Self-sterile (heterothallic) species contain one of two genes at MAT1, MAT1-1-1 or MAT1-2-1, and only isol...

  4. Phenological dynamics of arctic tundra vegetation and its implications on satellite imagery interpretation

    NASA Astrophysics Data System (ADS)

    Juutinen, Sari; Aurela, Mika; Mikola, Juha; Räsänen, Aleksi; Virtanen, Tarmo

    2016-04-01

    Remote sensing is a key methodology when monitoring the responses of arctic ecosystems to climatic warming. The short growing season and rapid vegetation development, however, set demands to the timing of image acquisition in the arctic. We used multispectral very high spatial resolution satellite images to study the effect of vegetation phenology on the spectral reflectance and image interpretation in the low arctic tundra in coastal Siberia (Tiksi, 71°35'39"N, 128°53'17"E). The study site mainly consists of peatlands, tussock, dwarf shrub, and grass tundra, and stony areas with some lichen and shrub patches. We tested the hypotheses that (1) plant phenology is responsive to the interannual weather variation and (2) the phenological state of vegetation has an impact on satellite image interpretation and the ability to distinguish between the plant communities. We used an empirical transfer function with temperature sums as drivers to reconstruct daily leaf area index (LAI) for the different plant communities for years 2005, and 2010-2014 based on measured LAI development in summer 2014. Satellite images, taken during growing seasons, were acquired for two years having late and early spring, and short and long growing season, respectively. LAI dynamics showed considerable interannual variation due to weather variation, and particularly the relative contribution of graminoid dominated communities was sensitive to these phenology shifts. We have also analyzed the differences in the reflectance values between the two satellite images taking account the LAI dynamics. These results will increase our understanding of the pitfalls that may arise from the timing of image acquisition when interpreting the vegetation structure in a heterogeneous tundra landscape. Very high spatial resolution multispectral images are available at reasonable cost, but not in high temporal resolution, which may lead to compromises when matching ground truth and the imagery. On the other hand

  5. Ecosystem Respiration Rates of Arctic Tundra Mesocosms in Response to Cold-Season Temperatures

    NASA Astrophysics Data System (ADS)

    Oberbauer, S. F.; Moser, J. G.; Olivas, P. C.; Starr, G.; Mortazavi, B.

    2013-12-01

    The cold season in the Arctic extends over 8 to 9 mo, during which air temperatures often reach as low as -40 °C. However, as a result of the insulating layer created by snow cover, temperatures seldom fall below -15 °C, and are likely warm enough to support some metabolism. Little research has been conducted on arctic plants and tundra during the cold season, despite its length and the fact that warming is predicted to be greatest during this period. The primary focus of cold-season research has been on rates of winter ecosystem respiration (ER) for estimates of annual carbon balance. The majority of these measurements during the winter or at winter temperatures indicate that some respiration is occurring. Although rates are low, they may contribute substantially to the annual carbon balance because of the length of the cold season. However, estimates of respiration at low temperatures differ substantially, have been taken at different temperatures using different methodologies, and importantly almost none provide quantitative relationships across a range of temperatures. We measured respiration rates of intact arctic tundra monoliths from 15 to -15 °C at 5 °C steps to facilitate improved model estimates of tundra respiration. Six tundra monoliths (~900 cm2) taken from Toolik Field Station, Alaska were conditioned for the cold season in growth chambers at shortened photoperiods and low, but above-freezing temperatures. Desired temperatures were obtained with a combination of growth chambers and a modified freezer. The average of five samplings of [CO2] at each temperature step was used to estimate the ER rates. Measurements were conducted with a closed system using incubation periods of 30 to 180 min, depending on the temperature. Carbon dioxide concentrations were measured by syringe samples injected into a N2 gas stream flowing through an infrared gas analyzer. Rates of ER calculated on an area basis were close to zero at -15 °C, but increased steadily with

  6. Shrub line advance in Arctic and alpine tundra of the Yukon Territory

    NASA Astrophysics Data System (ADS)

    Myers-Smith, I. H.; Hik, D.

    2010-12-01

    Growing evidence indicates an expansion of canopy-forming woody shrubs up mountain slopes and northward into Arctic tundra. The correlation between warming and greening has been used to link climate change with shrub expansion; however, the exact mechanisms driving observed increases in canopy-forming shrubs are probably more complex. Shrub expansion that results in a change in canopy cover may modify the ecology of tundra ecosystems by changing understory plant composition, soil thermal dynamics, surface albedo, nutrient turnover times and carbon storage. We surveyed the abundance of all tundra willow species (Salix spp.) growing at three sites in the Yukon Territory: the mountains of the Kluane Region, the Richardson Mountains, and on Qikiqtaruk - Herschel Island in the Beaufort Sea. At the two mountainous sites, we collected sections from the largest stem of willow shrubs at shrub line (the maximum elevation at which canopy-forming shrubs grow) and below shrub line (at approximately 50% shrub cover) in a total of 16 valleys. At the coastal site we collected samples from each of the 4 vegetation types: the alluvial fan, ridges, tussock tundra and disturbed terrain. Shrub stems were thin-sectioned using a microtome, photographed with a microscope and ring widths were measured from the digital images. We compared age distributions of willow individuals at and below shrub line and found younger populations at higher elevations, particularly on warm, south-facing aspects. Younger willows at shrub line and a lack of significant mortality in the field surveys indicate that shrubs have advanced up slope at the mountainous sites. Photographic and long-term plot data indicate increases in cover and height of willow shrub patches at the coastal site. We compared growth rings to regional weather data, and found positive correlations between annual growth and summer temperatures. Our results indicate that willows grew most in years with a warm June and July. This evidence of

  7. Isotope Hydrology of Arctic Tundra Lakes in a Region Impacted by Permafrost Disturbance

    NASA Astrophysics Data System (ADS)

    Peters, D. L.

    2009-05-01

    A projected "hot spot" of climate warming and development is the Mackenzie River Delta region, Northwest Territories, Canada. The upland tundra areas within the Mackenzie Gas Project development area north of Inuvik contain thousands of small lakes and ponds with poorly defined ephemeral drainage that are underlain by thick permafrost and ice-rich sediments for which the basic water balance controls are not fully understood. Natural retrogressive thaw slumps are common along lakeshores and the rapid drainage of ice-rich permafrost-dammed lakes has been occurring. Ongoing oil/gas exploration activities and infrastructure construction may result in terrain disturbance and localized degradation of permafrost, while climate change may increase the magnitude and frequency of thermokarst processes. These disturbed lakes are believed to act as historical analogues for the future effects of climate change on the hydrology, geochemistry, and aquatic ecology of small tundra lake catchments in the continuous permafrost zone of northwestern Canada. Environment Canada initiated an integrated research program in 2005 with the overall goal of improving our understanding of hydro-ecological processes in freshwater aquatic ecosystems affected by shoreline slumping vs. pristine lakes. Limited catchment studies have examined water-balance parameters (e.g., precipitation, evaporation, and surface flows) for tundra lakes in the development area. Enrichment of oxygen-18 (18O) and deuterium (2H) stable isotopes in surface waters have been shown to be useful indicators of water balance variations in remote permafrost regions of Canada where hydroclimatic information is very limited. In particular, information on evaporation: inflow (E/I) ratios and residence times would provide useful information for estimating appropriate water withdrawals from lakes within the proposed development area. A key question is "does permafrost slumping impact the hydrology of tundra lakes via catchment area

  8. Arctic Tundra Vegetation Functional Types Based on Photosynthetic Physiology and Optical Properties

    NASA Technical Reports Server (NTRS)

    Huemmrich, Karl Fred; Gamon, John A.; Tweedie, Craig E.; Campbell, Petya K. Entcheva; Landis, David R.; Middleton, Elizabeth M.

    2013-01-01

    Non-vascular plants (lichens and mosses) are significant components of tundra landscapes and may respond to climate change differently from vascular plants affecting ecosystem carbon balance. Remote sensing provides critical tools for monitoring plant cover types, as optical signals provide a way to scale from plot measurements to regional estimates of biophysical properties, for which spatial-temporal patterns may be analyzed. Gas exchange measurements were collected for pure patches of key vegetation functional types (lichens, mosses, and vascular plants) in sedge tundra at Barrow, AK. These functional types were found to have three significantly different values of light use efficiency (LUE) with values of 0.013 plus or minus 0.0002, 0.0018 plus or minus 0.0002, and 0.0012 plus or minus 0.0001 mol C mol (exp -1) absorbed quanta for vascular plants, mosses and lichens, respectively. Discriminant analysis of the spectra reflectance of these patches identified five spectral bands that separated each of these vegetation functional types as well as nongreen material (bare soil, standing water, and dead leaves). These results were tested along a 100 m transect where midsummer spectral reflectance and vegetation coverage were measured at one meter intervals. Along the transect, area-averaged canopy LUE estimated from coverage fractions of the three functional types varied widely, even over short distances. The patch-level statistical discriminant functions applied to in situ hyperspectral reflectance data collected along the transect successfully unmixed cover fractions of the vegetation functional types. The unmixing functions, developed from the transect data, were applied to 30 m spatial resolution Earth Observing-1 Hyperion imaging spectrometer data to examine variability in distribution of the vegetation functional types for an area near Barrow, AK. Spatial variability of LUE was derived from the observed functional type distributions. Across this landscape, a

  9. Delineation of Tundra Swan Cygnus c. columbianus populations in North America: geographic boundaries and interchange

    USGS Publications Warehouse

    Ely, Craig R.; Sladen, William J. L.; Wilson, Heather M.; Savage, Susan E.; Sowl, Kristine M.; Henry, Bill; Schwitters, Mike; Snowden, James

    2014-01-01

    North American Tundra Swans Cygnus c. columbianus are composed of two wellrecognised populations: an Eastern Population (EP) that breeds across northern Canada and north of the Brooks Range in Alaska, which migrates to the eastern seaboard of the United States, and a Western Population (WP) that breeds in coastal regions of Alaska south of the Brooks Range and migrates to western North America. We present results of a recent major ringing effort from across the breeding range in Alaska to provide a better definition of the geographic extent of the migratory divide in Alaska. We also reassess the staging and winter distributions of these populations based on locations of birds tracked using satellite transmitters, and recent recoveries and sightings of neck-collared birds. Summer sympatry of EP and WP Tundra Swans is very limited, and largely confined to a small area in northwest Alaska. Autumn migration pathways of EP and WP Tundra swans abut in southwest Saskatchewan, a region where migrating WP birds turn west, and EP birds deviate abruptly eastward. Overall, from 1989 to 2013 inclusive, 2.6% of recoveries or resightings reported to the USGS Bird Banding Laboratory were of birds that moved from the domain of the population in which they were initially captured to within the range of the other population; a proportion roughly comparable to the results of Limpert et al. (1991) for years before 1990. Of the 70 cross-boundary movements reported since 1989, 39% were of birds marked on breeding areas and 61% were of birds marked on wintering areas. Dispersing swans (i.e. those that made crossboundary movements) did not differ with respect to age or sex from those that did not move between populations. The Brooks Range in northern Alaska effectively separates the two populations within Alaska, but climate-induced changes in tundra breeding habitats and losses of wetlands on staging areas may alter the distribution for both of these populations.

  10. Nitrogen Accumulation and Partitioning in High Arctic Tundra from Extreme Atmospheric N Deposition Events

    NASA Astrophysics Data System (ADS)

    Phoenix, G. K.; Osborn, A.; Blaud, A.; Press, M. C.; Choudhary, S.

    2013-12-01

    Arctic ecosystems are threatened by pollution from extreme atmospheric nitrogen (N) deposition events. These events occur from the long-range transport of reactive N from pollution sources at lower latitudes and can deposit up to 80% of the annual N deposition in just a few days. To date, the fate and impacts of these extreme pollutant events has remained unknown. Using a field simulation study, we undertook the first assessment of the fate of acutely deposited N on arctic tundra. Extreme N deposition events were simulated on field plots at Ny-Ålesund, Svalbard (79oN) at rates of 0, 0.04, 0.4 and 1.2 g N m-2 yr-1 applied as NH4NO3 solution over 4 days, with 15N tracers used in the second year to quantify the fate of the deposited N in the plant, soil, microbial and leachate pools. Separate applications of 15NO3- and 15NH4+ were also made to determine the importance of N form in the fate of N. Recovery of the 15N tracer at the end of the first growing season approached 100% of the 15N applied irrespective of treatment level, demonstrating the considerable capacity of High Arctic tundra to capture pollutant N from extreme deposition events. Most incorporation of the 15N was found in bryophytes, followed by the dominant vascular plant (Salix polaris) and the microbial biomass of the soil organic layer. Total recovery remained high in the second growing season (average of 90%), indicating highly conservative N retention. Between the two N forms, recovery of 15NO3- and 15NH4+ were equal in the non-vascular plants, whereas in the vascular plants (particularly Salix polaris) recovery of 15NO3- was four times higher than of 15NH4+. Overall, these findings show that High Arctic tundra has considerable capacity to capture and retain the pollutant N deposited in acute extreme deposition events. Given they can represent much of the annual N deposition, extreme deposition events may be more important than increased chronic N deposition as a pollution source. Furthermore

  11. Long-term persistence of spent lead shot in tundra wetlands

    USGS Publications Warehouse

    Flint, P.L.; Schamber, J.L.

    2010-01-01

    We seeded experimental plots with number 4 lead pellets and sampled these plots for 10 years to assess the settlement rate of pellets in tundra wetland types commonly used by foraging waterfowl. After 10 years, about 10% of pellets remained within 6 cm of the surface, but >50% remained within 10 cm. We predict that spent lead pellets will eventually become unavailable to waterfowl; however, it will likely require >25 years for all pellets to exceed depths at which waterfowl species may forage. ?? 2010 The Wildlife Society.

  12. Biogeochemistry of Stinking Springs, Utah. Part II: Microbial Diversity and Photo- and Chemo-Autotrophic Growth Rates in a Layered Microbial Mat

    NASA Astrophysics Data System (ADS)

    Monteverde, D.; Metzger, J. G.; Bournod, C.; Kelly, H.; Johnson, H.; Sessions, A. L.; Osburn, M.; Shapiro, R. S.; Rideout, J.; Johnston, D. T.; Stevenson, B.; Stamps, B. W.; Vuono, D.; Hanselmann, K.; Spear, J. R.

    2013-12-01

    Layered microbial mats have garnered attention for their high phylogenetic diversity and exploitation of geochemical gradients often on the mm scale. However, despite their novelty and implications for early life diversification, little is known about layered microbial mat growth rates or the interdependence of the microbial communities within the system. Stinking Springs, a warm, sulfidic, saline spring northeast of the Great Salt Lake, serves as our test-site to investigate some of these questions. Stinking Springs undergoes downstream changes in pH (6.59-8.14), sulfide (527μM - below detection), sulfate (13-600μM), TCO2 (7.77-3.71mM), and temperature (40-21°C) along its ~150m flow path. The first 10m of discharge is channelized, beyond that, the spring supports a 10 to 40mm-thick layered microbial mat covering ~40% of the total spring runoff area. The mat was divided into four texturally-distinct layers which were each analyzed for 16S rRNA, lipid abundance, and bicarbonate and acetate uptake rates in addition to standard microscopy analyses. 16S rRNA analyses confirmed high taxa diversity within each layer, which varied significantly in taxa makeup such that no single phylum dominated the abundance (>33%) in more than one mat layer. The taxonomic diversity tended to increase with mat depth, a similar finding to other studies on layered microbial mats. A mat sampling transect across 16 meters showed that layer taxonomic diversity was conserved horizontally for all four mat layers, which implies mat depth has a larger control on diversity than physical or chemical parameters. Microscopy indicated the presence of diatoms in all layers which was confirmed by lipid abundance of sterols and long-branch fatty acid methyl esters. Incubation experiments were conducted in light and dark conditions over 24 hours with separate 13C-tagged bicarbonate and acetate additions. Heterotrophic growth rates (acetate uptake; 0.03-0.65%/day) were higher than autotrophic growth

  13. Radon and thoron anomalies along Mat fault in Mizoram, India

    NASA Astrophysics Data System (ADS)

    Jaishi, Hari Prasad; Singh, Sanjay; Tiwari, Raghavendra Prasad; Tiwari, Ramesh Chandra

    2013-12-01

    In this study, radon and thoron concentrations in soil gas has been monitored using LR-115(II) solid state nuclear track detectors since 15th July 2011 to February 2012. The study was carried out along Mat fault in Serchip district, Mizoram, India at two different sites - Mat Bridge (23°18'N, 92°48'E) and Tuichang (23°13'N, 92°56'E). The results obtained have been correlated to the seismic events that occurred within 800 km from the measuring sites over the mentioned period of time. Anomalous behaviour in radon concentrations have been observed prior to some earthquakes. Interestingly, some thoron anomalies were also recorded.

  14. MatMRI and MatHIFU: software toolboxes for real-time monitoring and control of MR-guided HIFU

    PubMed Central

    2013-01-01

    Background The availability of open and versatile software tools is a key feature to facilitate pre-clinical research for magnetic resonance imaging (MRI) and magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) and expedite clinical translation of diagnostic and therapeutic medical applications. In the present study, two customizable software tools that were developed at the Thunder Bay Regional Research Institute are presented for use with both MRI and MR-HIFU. Both tools operate in a MATLAB®; environment. The first tool is named MatMRI and enables real-time, dynamic acquisition of MR images with a Philips MRI scanner. The second tool is named MatHIFU and enables the execution and dynamic modification of user-defined treatment protocols with the Philips Sonalleve MR-HIFU therapy system to perform ultrasound exposures in MR-HIFU therapy applications. Methods MatMRI requires four basic steps: initiate communication, subscribe to MRI data, query for new images, and unsubscribe. MatMRI can also pause/resume the imaging and perform real-time updates of the location and orientation of images. MatHIFU requires four basic steps: initiate communication, prepare treatment protocol, and execute treatment protocol. MatHIFU can monitor the state of execution and, if required, modify the protocol in real time. Results Four applications were developed to showcase the capabilities of MatMRI and MatHIFU to perform pre-clinical research. Firstly, MatMRI was integrated with an existing small animal MR-HIFU system (FUS Instruments, Toronto, Ontario, Canada) to provide real-time temperature measurements. Secondly, MatMRI was used to perform T2-based MR thermometry in the bone marrow. Thirdly, MatHIFU was used to automate acoustic hydrophone measurements on a per-element basis of the 256-element transducer of the Sonalleve system. Finally, MatMRI and MatHIFU were combined to produce and image a heating pattern that recreates the word ‘HIFU’ in a tissue

  15. EVAPORITE MICROBIAL FILMS, MATS, MICROBIALITES AND STROMATOLITES

    SciTech Connect

    Brigmon, R; Penny Morris, P; Garriet Smith, G

    2008-01-28

    Evaporitic environments are found in a variety of depositional environments as early as the Archean. The depositional settings, microbial community and mineralogical composition vary significantly as no two settings are identical. The common thread linking all of the settings is that evaporation exceeds precipitation resulting in elevated concentrations of cations and anions that are higher than in oceanic systems. The Dead Sea and Storrs Lake are examples of two diverse modern evaporitic settings as the former is below sea level and the latter is a coastal lake on an island in the Caribbean. Each system varies in water chemistry as the Dead Sea dissolved ions originate from surface weathered materials, springs, and aquifers while Storrs Lake dissolved ion concentration is primarily derived from sea water. Consequently some of the ions, i.e., Sr, Ba are found at significantly lower concentrations in Storrs Lake than in the Dead Sea. The origin of the dissolved ions are ultimately responsible for the pH of each system, alkaline versus mildly acidic. Each system exhibits unique biogeochemical properties as the extreme environments select certain microorganisms. Storrs Lake possesses significant biofilms and stromatolitic deposits and the alkalinity varies depending on rainfall and storm activity. The microbial community Storrs Lake is much more diverse and active than those observed in the Dead Sea. The Dead Sea waters are mildly acidic, lack stromatolites, and possess a lower density of microbial populations. The general absence of microbial and biofilm fossilization is due to the depletion of HCO{sub 3} and slightly acidic pH.

  16. An assessment of the carbon balance of arctic tundra: comparisons among observations, process models, and atmospheric inversions

    USGS Publications Warehouse

    McGuire, A.D.; Christensen, T.R.; Hayes, D.; Heroult, A.; Euskirchen, E.; Yi, Y.; Kimball, J.S.; Koven, C.; Lafleur, P.; Miller, P.A.; Oechel, W.; Peylin, P.; Williams, M.

    2012-01-01

    Although arctic tundra has been estimated to cover only 8% of the global land surface, the large and potentially labile carbon pools currently stored in tundra soils have the potential for large emissions of carbon (C) under a warming climate. These emissions as radiatively active greenhouse gases in the form of both CO2 and CH4 could amplify global warming. Given the potential sensitivity of these ecosystems to climate change and the expectation that the Arctic will experience appreciable warming over the next century, it is important to assess whether responses of C exchange in tundra regions are likely to enhance or mitigate warming. In this study we compared analyses of C exchange of Arctic tundra between 1990–1999 and 2000–2006 among observations, regional and global applications of process-based terrestrial biosphere models, and atmospheric inversion models. Syntheses of the compilation of flux observations and of inversion model results indicate that the annual exchange of CO2 between arctic tundra and the atmosphere has large uncertainties that cannot be distinguished from neutral balance. The mean estimate from an ensemble of process-based model simulations suggests that arctic tundra acted as a sink for atmospheric CO2 in recent decades, but based on the uncertainty estimates it cannot be determined with confidence whether these ecosystems represent a weak or a strong sink. Tundra was 0.6 °C warmer in the 2000s compared to the 1990s. The central estimates of the observations, process-based models, and inversion models each identify stronger sinks in the 2000s compared with the 1990s. Similarly, the observations and the applications of regional process-based models suggest that CH4 emissions from arctic tundra have increased from the 1990s to 2000s. Based on our analyses of the estimates from observations, process-based models, and inversion models, we estimate that arctic tundra was a sink for atmospheric CO2 of 110 Tg C yr-1 (uncertainty between a

  17. Soil carbon content and CO2 flux along a hydrologic gradient in a High-Arctic tundra lake basin, Northwest Greenland

    NASA Astrophysics Data System (ADS)

    McKnight, J.; Klein, E. S.; Welker, J. M.; Schaeffer, S. M.; Franklin, M.

    2015-12-01

    High Arctic landscapes are composed of watershed basins that vary in size and ecohydrology, but typically have a plant community complex that ranges from dry tundra to moist tundra to wet sedge systems along water body shorelines. The spatial extent of these plant communities reflects mean annual soil moisture and temperature, and is vulnerable to changes in climate conditions. Soil moisture and temperature significantly influence organic matter microbial activity and decomposition, and can affect the fate of soil carbon in tundra soils. Consequently, due to the unique soil carbon differences between tundra plant communities, shifts in their spatial extent may drive future High Arctic biosphere-atmosphere interactions. Understanding this terrestrial-atmosphere trace gas feedback, however, requires quantification of the rates and patterns of CO2 exchange along soil moisture gradients and the associated soil properties. In summer of 2015, soil CO2 flux rate, soil moisture and temperature were measured along a soil moisture gradient spanning three vegetation zones (dry tundra, wet tundra, and wet grassland) in a snow melt-fed lake basin near Thule Greenland. Mean soil temperature during the 2015 growing season was greater in dry tundra than in wet tundra and wet grassland (13.0 ± 1.2, 7.8 ± 0.8, and 5.5 ± 0.9°C, respectively). Mean volumetric soil moisture differed among all three vegetation zones where the soil moisture gradient ranged from 9 % (dry tundra) to 34 % (wet tundra) to 51 % (wet grassland). Mean soil CO2 flux was significantly greater in the wet grassland (1.7 ± 0.1 μmol m-2 s-1) compared to wet tundra (0.9 ± 0.2 μmol m-2 s-1) and dry tundra (1.2 ± 0.2 μmol m-2 s-1). Soil CO2 flux increased and decreased with seasonal warming and cooling of soil temperature. Although soil temperature was an important seasonal driver of soil CO2 flux rates, differences in mean seasonal soil CO2 flux rates among vegetation zones appeared to be a function of the

  18. Variation in Isotopic Biosignatures From Carbonate Rich, Microbial Mats in Saline, Alkaline Lakes on the Cariboo Plateau, B.C.

    NASA Astrophysics Data System (ADS)

    Brady, A.; Slater, G.; Druschel, G.; Lim, D.

    2009-05-01

    Cyanobacteria dominated, carbonate rich microbial mats found in saline, alkaline lakes on the Cariboo Plateau, B.C. represent potential analogues of the evaporative systems that might have occurred on early Earth or Mars. These evaporative lakes generally have pH values > 10, salinities of up to 33 psu and alkalinities of > 15, 000 mg CaCO3/L but differ in other geochemical parameters. The ability to understand natural variations in microbial activity and biosignatures in such modern analogues is central to our understanding of the capabilities and limits of life, the interpretation of the geologic record and potentially one day to the interpretation of astrobiological data. Phospholipid fatty acid (PLFA) profiling, voltammetry, and stable isotope analysis of organic and inorganic carbon pools highlighted the spatial and seasonal variability that exists in modern evaporative microbial mat dominated lakes. Variations in microbial PLFA distribution demonstrated that Cariboo Plateau microbial mat community composition varied seasonally and spatially. Voltammetry results showed that photosynthetic oxygen production occurred in the upper 5 mm of mats resulting in supersaturation of oxygen in surface waters. Depletion of oxygen generally occurred just below 5 mm and sulfide production began at 10 - 15 mm from the mat surface. Isotope analysis (13C) of Cariboo microbial mats showed inorganic (dissolved inorganic carbon) to organic (bulk cell) isotopic discriminations of 23-25 ‰, indicating non-CO2 limited photosynthesis. These results are in contrast to high organic content analogue mats previously reported that show evidence of CO2 limitation. Further, the Cariboo mats demonstrated significant intra- and inter-mat variations in carbonate δ13C values with respect to dissolved inorganic carbon (DIC) ranging from enrichment to 13C-depleted carbonate. In Deer Lake, isotopic enrichment of surface water DIC by 2-3 ‰ above atmospheric equilibrium indicated microbial

  19. Size and mass of grit in gizzards of Sandhill Cranes, Tundra Swans, and Mute Swans

    USGS Publications Warehouse

    Franson, J.C.; Hansen, S.P.; Duerr, A.E.; DeStefano, S.

    2001-01-01

    Because it has been suggested that waterbirds may ingest lost or discarded lead fishing weights as grit, we examined grit in the gizzards of Sandhill Cranes (Grus canadensis), Tundra Swans (Cygnus columbianus), and Mute Swans (Cygnus olor), three species where individuals have been poisoned by the ingestion of lead fishing weights. The greatest proportion (by mass) of grit in gizzards of Sandhill Cranes consisted of particles with a minimum dimension of 2.36-4.75 mm. Grit particles in swans were much smaller, with the most prevalent (by mass) being 0.6-1.18 mm. The greatest dimension of the largest grit particle found in cranes and swans was 17.4 mm and 14.0 mm, respectively. The U.S. Environmental Protection Agency has proposed a ban on lead fishing weights of ???25.4 mm in any dimension. Based on the size of grit particles that we found in gizzards of Sandhill Cranes, Mute Swans, and Tundra Swans, we believe it is unlikely that individuals of those species would ingest, as grit, lead fishing weights larger than 25.4 mm in any dimension. Received 10 January 2001, accepted 28 February 2001.

  20. Size and mass of grit in gizzards of sandhill cranes, tundra swans, and mute swans.

    USGS Publications Warehouse

    Franson, J. Christian; Hansen, Scott P.; Duerr, Adam E.; DeStefano, Stephen

    2001-01-01

    Because it has been suggested that waterbirds may ingest lost or discarded lead fishing weights as grit, we examined grit in the gizzards of Sandhill Cranes (Grus canadensis), Tundra Swans (Cygnus columbianus), and Mute Swans (Cygnus olor), three species where individuals have been poisoned by the ingestion of lead fishing weights. The greatest proportion (by mass) of grit in gizzards of Sandhill Cranes consisted of particles with a minimum dimension of 2.36-4.75 mm. Grit particles in swans were much smaller, with the most prevalent (by mass) being 0.6-1.18 mm. The greatest dimension of the largest grit particle found in cranes and swans was 17.4 mm and 14.0 mm, respectively. The U.S. Environmental Protection Agency has proposed a ban on lead fishing weights of ≤25.4 mm in any dimension. Based on the size of grit particles that we found in gizzards of Sandhill Cranes, Mute Swans, and Tundra Swans, we believe it is unlikely that individuals of those species would ingest, as grit, lead fishing weights larger than 25.4 mm in any dimension.

  1. Reproductive Ecology and Severe Pollen Limitation in the Polychromic Tundra Plant, Parrya nudicaulis (Brassicaceae)

    PubMed Central

    Fulkerson, Justin R.; Whittall, Justen B.; Carlson, Matthew L.

    2012-01-01

    Pollen limitation is predicted to be particularly severe in tundra habitats. Numerous reproductive patterns associated with alpine and arctic species, particularly mechanisms associated with reproductive assurance, are suggested to be driven by high levels of pollen limitation. We studied the reproductive ecology of Parrya nudicaulis, a species with relatively large sexual reproductive investment and a wide range of floral pigmentation, in tundra habitats in interior montane Alaska to estimate the degree of pollen limitation. The plants are self-compatible and strongly protandrous, setting almost no seed in the absence of pollinators. Supplemental hand pollinations within pollinator exclusion cages indicated no cage effect on seed production. Floral visitation rates were low in both years of study and particularly infrequent in 2010. A diversity of insects visited P. nudicaulis, though syrphid and muscid flies composed the majority of all visits. Pollen-ovule ratios and levels of heterozygosity are consistent with a mixed mating system. Pollen limitation was severe; hand pollinations increased seed production per plant five-fold. Seed-to-ovule ratios remained low following hand pollinations, indicating resource limitation is likely to also be responsible for curtailing seed set. We suggest that pollen limitation in P. nudicaulis may be the result of selection favoring an overproduction of ovules as a bet-hedging strategy in this environmental context of highly variable pollen receipt. PMID:22427886

  2. Methane emissions from Alaska Arctic tundra - An assessment of local spatial variability

    NASA Technical Reports Server (NTRS)

    Morrissey, L. A.; Livingston, G. P.

    1992-01-01

    The findings of an extensive midsummer survey of CH4 emissions measurements representing the Alaska Arctic tundra are presented. Variability in rates of emissions was similar in magnitude on local and regional scales, ranging from 0 to 286.5 mg/sq m/d overall and often varying across two orders of magnitude within 0.5 m distances. Primary control on rates of emission was determined by the substrate and position of the water table relative to the surface. Emission rates in the Arctic Foothills ranged from 0.2 mg/sq m/d for tussock tundra to 55.53 mg/sq m/d over wet meadows. Plant-mediated release of CH4 to the atmosphere was directly proportional to green leaf area and represented 92-98 percent of the total emission rates over vegetated sites. The results suggest the current published emission rates may have overestimated the contribution of boreal ecosystems to the global CH4 budget by several fold.

  3. Distinct soil bacterial communities along a small-scale elevational gradient in alpine tundra

    PubMed Central

    Shen, Congcong; Ni, Yingying; Liang, Wenju; Wang, Jianjun; Chu, Haiyan

    2015-01-01

    The elevational diversity pattern for microorganisms has received great attention recently but is still understudied, and phylogenetic relatedness is rarely studied for microbial elevational distributions. Using a bar-coded pyrosequencing technique, we examined the biodiversity patterns for soil bacterial communities of tundra ecosystem along 2000–2500 m elevations on Changbai Mountain in China. Bacterial taxonomic richness displayed a linear decreasing trend with increasing elevation. Phylogenetic diversity and mean nearest taxon distance (MNTD) exhibited a unimodal pattern with elevation. Bacterial communities were more phylogenetically clustered than expected by chance at all elevations based on the standardized effect size of MNTD metric. The bacterial communities differed dramatically among elevations, and the community composition was significantly correlated with soil total carbon (TC), total nitrogen, C:N ratio, and dissolved organic carbon. Multiple ordinary least squares regression analysis showed that the observed biodiversity patterns strongly correlated with soil TC and C:N ratio. Taken together, this is the first time that a significant bacterial diversity pattern has been observed across a small-scale elevational gradient. Our results indicated that soil carbon and nitrogen contents were the critical environmental factors affecting bacterial elevational distribution in Changbai Mountain tundra. This suggested that ecological niche-based environmental filtering processes related to soil carbon and nitrogen contents could play a dominant role in structuring bacterial communities along the elevational gradient. PMID:26217308

  4. Russian Arctic warming and ‘greening’ are closely tracked by tundra shrub willows

    NASA Astrophysics Data System (ADS)

    Forbes, B. C.; Macias Fauria, M.; Zetterberg, P.

    2009-12-01

    Growth in arctic vegetation is generally expected to increase under a warming climate, particularly among deciduous shrubs. We analyzed annual ring growth for an abundant and nearly circumpolar erect willow (Salix lanata L.) from the coastal zone of the northwest Russian Arctic (Nenets Autonomous Okrug). The resulting chronology is strongly related to summer temperature for the period 1942-2005. Remarkably high correlations occur at long distances (>1600 km) across the tundra and taiga zones of West Siberia and Eastern Europe. We also found a clear relationship with photosynthetic activity for upland vegetation at a regional scale for the period 1981-2005, confirming a parallel ‘greening’ trend reported for similarly warming North American portions of the tundra biome. The standardized growth curve suggests a significant increase in shrub willow growth over the last six decades. These findings are in line with field and remote sensing studies that have assigned a strong shrub component to the reported greening signal since the early 1980s. Furthermore, the growth trend agrees with qualitative observations by nomadic Nenets reindeer herders of recent increases in willow size in the region. The quality of the chronology as a climate proxy is exceptional. Given its wide geographic distribution and the ready preservation of wood in permafrost, S. lanata L. has great potential for extended temperature reconstructions in remote areas across the Arctic.

  5. Simulating the effects of climate change and climate variability on carbon dynamics in Arctic tundra

    NASA Astrophysics Data System (ADS)

    Stieglitz, Marc; Giblin, Anne; Hobbie, John; Williams, Matthew; Kling, George

    2000-12-01

    Through a simple modeling exercise, three mechanisms have been identified, each operating at a different timescale, that may govern carbon dynamics in Arctic tundra regions and partially explain observed CO2 flux variability. At short timescales the biosphere reacts to meteorological forcing. Drier conditions are associated with aerobic soil decomposition, a large CO2efflux, and a net ecosystem loss of carbon. Cooler and moister conditions favor slower anaerobic decomposition in soils, good growing conditions, and terrestrial carbon sequestration. At intermediate timescales, periods of terrestrial carbon loss are directly linked to periods of carbon sequestration by the ability of the ecosystem to retain labile nitrogen. Labile nitrogen released to the soil during periods when the tundra is a source of carbon (soil respiration > net primary productivity) is retained within the ecosystem and accessed during periods when carbon sequestration is favored (net primary productivity > soil respiration). Finally, the ability of vegetation to respond to long-term changes in soil nutrient status via changes in leaf nitrogen and leaf area index modulates this dynamic at intermediate to long timescales.

  6. Measurements of NO(x) and NO(y) concentrations and fluxes over Arctic tundra

    NASA Technical Reports Server (NTRS)

    Bakwin, Peter S.; Wofsy, Steven C.; Fan, Song-Miao; Fitzjarrald, David R.

    1992-01-01

    Measurements of the atmospheric concentrations of NO, NO2, total NO(y), and O3 were made during the NASA Arctic Boundary Layer Expedition (ABLE 3A) at a remote location in a tundra bog ecosystem in southeastern Alaska during the growing season (July-August 1988). Concentrations of NO(x) and NO(y) were found to be very low compared to other remote continental sites, indicating that anthropogenic influences were small at this site during this time of year. The NO(y) emission rate from the soil were 0.13 +/- 0.05 x 10 exp 9 molecules/sq cm/s. Direct measurements of the flux of total NO(y) were made for the first time, indicating downward flux of NO(y) at all times of day, with maximum deposition of 2.5 +/- 0.9 x 10 exp 9 molecules/sq cm/s in the afternoon. Deposition of HNO3 appears to dominate the atmosphere/surface exchange of NO(y). The mean dry deposition rate of NO(y) to the tundra was 1.8 +/- 1.0 x 10 exp 9 molecules/sq cm/s.

  7. Arctic Tundra Vegetation Functional Types Based on Photosynthetic Physiology and Optical Properties

    NASA Technical Reports Server (NTRS)

    Huemmrich, Karl F.; Gamon, John; Tweedie, Craig; Campbell, Petya K.; Landis, David R.; Middleton, Elizabeth M.

    2013-01-01

    Non-vascular plants (lichens and mosses) are significant components of tundra landscapes and may respond to climate change differently from vascular plants affecting ecosystem carbon balance. Remote sensing provides critical tools for monitoring plant cover types, as optical signals provide a way to scale from plot measurements to regional estimates of biophysical properties, for which spatial-temporal patterns may be analyzed. Gas exchange measurements were collected for pure patches of key vegetation functional types (lichens, mosses, and vascular plants) in sedge tundra at Barrow AK. These functional types were found to have three significantly different values of light use efficiency (LUE) with values of 0.013+/-0.001, 0.0018+/-0.0002, and 0.0012+/-0.0001 mol C/mol absorbed quanta for vascular plants, mosses and lichens, respectively. Discriminant analysis of the spectra reflectance of these patches identified five spectral bands that separated each of these vegetation functional types as well as nongreen material (bare soil, standing water, and dead leaves). These results were tested along a 100 m transect where midsummer spectral reflectance and vegetation coverage were measured at one meter intervals.

  8. Object-based Mapping of the Circumpolar Taiga-Tundra Ecotone with MODIS Tree Cover

    NASA Technical Reports Server (NTRS)

    Ransom, Kenneth J.; Montesano, Paul M.; Nelson, Ross F.

    2011-01-01

    The circumpolar taiga-tundra ecotone was delineated using an image segmentation based mapping approach with multi-annual MODIS Vegetation Continuous Fields (VCF) tree cover data. Circumpolar tree canopy cover (TCC) throughout the ecotone was derived by averaging MODIS VCF data from 2000 - 2005 and adjusting the averaged values using linear equations relating MODIS TCC to Quickbird-derived tree cover estimates. The adjustment helped mitigate VCF's overestimation of tree cover in lightly forested regions. An image segmentation grouped pixels representing similar tree cover into polygonal features (objects) that form the map of the transition zone. Eachfeature represents an area much larger than the 500m MODIS pixel to characterize thepatterns of sparse forest patches on a regional scale. Comparisons of the adjusted average tree cover data were made with (1) two existing tree line definitions aggregated for each 1deg longitudinal interval in North America and Eurasia and (2) Landsat-derived Canadianproportion of forest cover for Canada. The adjusted TCC from MODIS VCF shows, on average, greater than 12% TCC for all but one regional zone at the intersection with independently delineated tree lines. Adjusted values track closely with Canadian proportion of forest cover data in areas of low tree cover. Those polygons near the boreal/tundra interface with either (1) mean adjusted TCC values between 5-20% , or (2) mean adjusted TCC values <5% but with a standard deviation > 5% were used to identify the ecotone.

  9. Prevalence, transmission, and genetic diversity of blood parasites infecting tundra-nesting geese in Alaska

    USGS Publications Warehouse

    Ramey, Andy M.; Reed, John A.; Schmutz, Joel A.; Fondell, Tom F.; Meixell, Brandt W.; Hupp, Jerry W.; Ward, David H.; Terenzi, John; Ely, Craig R.

    2014-01-01

    A total of 842 blood samples collected from five species of tundra-nesting geese in Alaska was screened for haemosporidian parasites using molecular techniques. Parasites of the generaLeucocytozoon Danilewsky, 1890, Haemoproteus Kruse, 1890, and Plasmodium Marchiafava and Celli, 1885 were detected in 169 (20%), 3 (<1%), and 0 (0%) samples, respectively. Occupancy modeling was used to estimate prevalence of Leucocytozoon parasites and assess variation relative to species, age, sex, geographic area, year, and decade. Species, age, and decade were identified as important in explaining differences in prevalence of Leucocytozoonparasites. Leucocytozoon parasites were detected in goslings sampled along the Arctic Coastal Plain using both historic and contemporary samples, which provided support for transmission in the North American Arctic. In contrast, lack of detection of Haemoproteus and Plasmodiumparasites in goslings (n = 238) provided evidence to suggest that the transmission of parasites of these genera may not occur among waterfowl using tundra habitats in Alaska, or alternatively, may only occur at low levels. Five haemosporidian genetic lineages shared among different species of geese sampled from two geographic areas were indicative of interspecies parasite transmission and supported broad parasite or vector distributions. However, identicalLeucocytozoon and Haemoproteus lineages on public databases were limited to waterfowl hosts suggesting constraints in the range of parasite hosts.

  10. Pan-Arctic ice-wedge degradation in warming permafrost and its influence on tundra hydrology

    NASA Astrophysics Data System (ADS)

    Liljedahl, Anna K.; Boike, Julia; Daanen, Ronald P.; Fedorov, Alexander N.; Frost, Gerald V.; Grosse, Guido; Hinzman, Larry D.; Iijma, Yoshihiro; Jorgenson, Janet C.; Matveyeva, Nadya; Necsoiu, Marius; Raynolds, Martha K.; Romanovsky, Vladimir E.; Schulla, Jörg; Tape, Ken D.; Walker, Donald A.; Wilson, Cathy J.; Yabuki, Hironori; Zona, Donatella

    2016-04-01

    Ice wedges are common features of the subsurface in permafrost regions. They develop by repeated frost cracking and ice vein growth over hundreds to thousands of years. Ice-wedge formation causes the archety