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  1. Article ; Online: Seasonal controls override forest harvesting effects on the composition of dissolved organic matter mobilized from boreal forest soil organic horizons

    K. L. Bowering / K. A. Edwards / S. E. Ziegler

    Biogeosciences, Vol 20, Pp 2189-

    2023  Volume 2206

    Abstract: Dissolved organic matter (DOM) mobilized from the organic (O) horizons of forest soils is a temporally dynamic flux of carbon (C) and nutrients, and the fate of this DOM in downstream pools is dependent on the rate and pathways of water flow as well as ... ...

    Abstract Dissolved organic matter (DOM) mobilized from the organic (O) horizons of forest soils is a temporally dynamic flux of carbon (C) and nutrients, and the fate of this DOM in downstream pools is dependent on the rate and pathways of water flow as well as its chemical composition. Here, we present observations of the composition of DOM mobilized weekly to monthly from O horizons in mature forest and adjacent harvested treatment plots. The study site was experimentally harvested, without replanting, 10-years prior to this study. Thus, the treatments differ significantly in terms of forest stand and soil properties, and they interact differently with the regional hydrometeorological conditions. This presented an opportunity to investigate the role of forest structure relative to environmental variation on soil DOM mobilization. On an annual basis, fluxes of total dissolved nitrogen (TDN) and dissolved organic nitrogen (DON) were largest from the warmer and thinner O horizons of the harvested (H) treatment compared to the forest (F) treatment; however, neither phosphate nor ammonium fluxes differed by treatment type. On a short-term basis in both H and F treatments, all fluxes were positively correlated to water input, and all concentrations were positively correlated to soil temperature and negatively correlated to water input. Soil moisture was negatively correlated to the C : N of DOM. These results suggest common seasonal controls on DOM mobilization regardless of harvesting treatment. Optical characterization of seasonally representative samples additionally supported a stronger control of season over harvesting. The chemical character of DOM mobilized during winter and snowmelt: lower C : N, higher specific ultraviolet absorbance and lower molecular weight of chromophoric DOM (CDOM; higher spectral slope ratio) were representative of relatively more decomposed DOM compared to that mobilized in summer and autumn. This shows that the decomposition of soil organic matter underneath a consistently deep snowpack is a ...
    Keywords Ecology ; QH540-549.5 ; Life ; QH501-531 ; Geology ; QE1-996.5
    Subject code 550
    Language English
    Publishing date 2023-06-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: Soil organic matter diagenetic state informs boreal forest ecosystem feedbacks to climate change

    A. N. Myers-Pigg / K. Kaiser / R. Benner / S. E. Ziegler

    Biogeosciences, Vol 20, Pp 489-

    2023  Volume 503

    Abstract: The fate of soil organic carbon (SOC) in boreal forests is dependent on the integrative ecosystem response to climate change. For example, boreal forest productivity is often nitrogen (N) limited, and climate warming can enhance N cycling and primary ... ...

    Abstract The fate of soil organic carbon (SOC) in boreal forests is dependent on the integrative ecosystem response to climate change. For example, boreal forest productivity is often nitrogen (N) limited, and climate warming can enhance N cycling and primary productivity. However, the net effect of this feedback on the SOC reservoir and its longevity with climate change remain unclear due to difficulty in detecting small differences between large and variable carbon (C) fluxes needed to determine net changes in soil reservoirs. The diagenetic state of SOC – resulting from the physicochemical and biological transformations that alter the original biomolecular composition of detrital inputs to soil over time – is useful for tracing the net response of SOC at the timescales relevant to climate change not usually discernible from fluxes and stocks alone. Here, we test two hypotheses using a mesic boreal forest climate transect: (1) the SOC diagenetic state is maintained across this climosequence, and (2) the maintenance of the SOC diagenetic state is a consequence of coupled soil C and N cycling, signifying the role of enhanced N cycling supporting SOC inputs that maintain SOC stocks within the warmer-climate forests. Shifts in nonvascular to vascular plant inputs with climate observed in these and other boreal forests highlighted the need to carefully separate biogeochemical indicators of SOC source from those signifying diagenetic alteration. We thus evaluated and applied lignin biomarkers to assess the diagenetic alteration of SOC in these boreal forest organic soils and directly compared the lignin diagenetic state with that of soil organic nitrogen (SON) assessed through amino acid composition. The lignin diagenetic state remained constant across the climate transect, indicating a balance between the input and removal of lignin in these mesic boreal forests. When combined with previous knowledge of these forest ecosystems, including the diagenetic state of SON and direct measures of C fluxes and stocks, the results ...
    Keywords Ecology ; QH540-549.5 ; Life ; QH501-531 ; Geology ; QE1-996.5
    Subject code 550 ; 333
    Language English
    Publishing date 2023-02-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article ; Online: Dissolved organic carbon mobilized from organic horizons of mature and harvested black spruce plots in a mesic boreal region

    K. L. Bowering / K. A. Edwards / K. Prestegaard / X. Zhu / S. E. Ziegler

    Biogeosciences, Vol 17, Pp 581-

    2020  Volume 595

    Abstract: Boreal forests are subject to a wide range of temporally and spatially variable environmental conditions driven by season, climate, and disturbances such as forest harvesting and climate change. We captured dissolved organic carbon (DOC) from surface ... ...

    Abstract Boreal forests are subject to a wide range of temporally and spatially variable environmental conditions driven by season, climate, and disturbances such as forest harvesting and climate change. We captured dissolved organic carbon (DOC) from surface organic (O) horizons in a boreal forest hillslope using passive pan lysimeters in order to identify controls and hot moments of DOC mobilization from this key C source. We specifically addressed (1) how DOC fluxes from O horizons vary on a weekly to seasonal basis in forest and paired harvested plots and (2) how soil temperature, soil moisture, and water input relate to DOC flux trends in these plots over time. The total annual DOC flux from O horizons contain contributions from both vertical and lateral flow and was 30 % greater in the harvested plots than in the forest plots (54 g C m −2 vs. 38 g C m −2 , respectively; p =0.008 ). This was despite smaller aboveground C inputs and smaller soil organic carbon stocks in the harvested plots but analogous to larger annual O horizon water fluxes measured in the harvested plots. Water input, measured as rain, throughfall, and/or snowmelt depending on season and plot type, was positively correlated to variations in O horizon water fluxes and DOC fluxes within the study year. Soil temperature was positively correlated to temporal variations of DOC concentration ([DOC]) of soil water and negatively correlated with water fluxes, but no relationship existed between soil temperature and DOC fluxes at the weekly to monthly scale. The relationship between water input to soil and DOC fluxes was seasonally dependent in both plot types. In summer, a water limitation on DOC flux existed where weekly periods of no flux alternated with periods of large fluxes at high DOC concentrations. This suggests that DOC fluxes were water-limited and that increased water fluxes over this period result in proportional increases in DOC fluxes. In contrast, a flushing of DOC from O horizons (observed as decreasing DOC concentrations) occurred during ...
    Keywords Ecology ; QH540-549.5 ; Life ; QH501-531 ; Geology ; QE1-996.5
    Language English
    Publishing date 2020-02-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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    Inter-library loan at ZB MED

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  4. Article ; Online: Short- and long-term temperature responses of soil denitrifier net N 2 O efflux rates, inter-profile N 2 O dynamics, and microbial genetic potentials

    K. M. Buckeridge / K. A. Edwards / K. Min / S. E. Ziegler / S. A. Billings

    SOIL, Vol 6, Pp 399-

    2020  Volume 412

    Abstract: Production and reduction of nitrous oxide ( N 2 O ) by soil denitrifiers influence atmospheric concentrations of this potent greenhouse gas. Accurate projections of the net N 2 O flux have three key uncertainties: (1) short- vs. long-term responses to ... ...

    Abstract Production and reduction of nitrous oxide ( N 2 O ) by soil denitrifiers influence atmospheric concentrations of this potent greenhouse gas. Accurate projections of the net N 2 O flux have three key uncertainties: (1) short- vs. long-term responses to warming, (2) interactions among soil horizons, and (3) temperature responses of different steps in the denitrification pathway. We addressed these uncertainties by sampling soil from a boreal forest climate transect encompassing a 5.2 ∘ C difference in the mean annual temperature and incubating the soil horizons in isolation and together at three ecologically relevant temperatures in conditions that promote denitrification. Both short-term exposure to warmer temperatures and long-term exposure to a warmer climate increased N 2 O emissions from organic and mineral soils; an isotopic tracer suggested that an increase in N 2 O production was more important than a decline in N 2 O reduction. Short-term warming promoted the reduction of organic horizon-derived N 2 O by mineral soil when these horizons were incubated together. The abundance of nirS (a precursor gene for N 2 O production) was not sensitive to temperature, whereas that of nosZ clade I (a gene for N 2 O reduction) decreased with short-term warming in both horizons and was higher from a warmer climate. These results suggest a decoupling of gene abundance and process rates in these soils that differs across horizons and timescales. In spite of these variations, our results suggest a consistent, positive response of denitrifier-mediated net N 2 O efflux rates to temperature across timescales in these boreal forests. Our work also highlights the importance of understanding cross-horizon N 2 O fluxes for developing a predictive understanding of net N 2 O efflux from soils.
    Keywords Environmental sciences ; GE1-350 ; Geology ; QE1-996.5
    Subject code 333
    Language English
    Publishing date 2020-08-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article ; Online: Soil profile connectivity can impact microbial substrate use, affecting how soil CO 2 effluxes are controlled by temperature

    F. A. Podrebarac / S. A. Billings / K. A. Edwards / J. Laganière / M. J. Norwood / S. E. Ziegler

    Biogeosciences, Vol 18, Pp 4755-

    2021  Volume 4772

    Abstract: Determining controls on the temperature sensitivity of heterotrophic soil respiration remains critical to incorporating soil–climate feedbacks into climate models. Most information on soil respiratory responses to temperature comes from laboratory ... ...

    Abstract Determining controls on the temperature sensitivity of heterotrophic soil respiration remains critical to incorporating soil–climate feedbacks into climate models. Most information on soil respiratory responses to temperature comes from laboratory incubations of isolated soils and typically subsamples of individual horizons. Inconsistencies between field and laboratory results may be explained by microbial priming supported by cross-horizon exchange of labile C or N. Such exchange is feasible in intact soil profiles but is absent when soils are isolated from surrounding depths. Here we assess the role of soil horizon connectivity, by which we mean the degree to which horizons remain layered and associated with each other as they are in situ, on microbial C and N substrate use and its relationship to the temperature sensitivity of respiration. We accomplished this by exploring changes in C : N, soil organic matter composition (via C : N, amino acid composition and concentration, and nuclear magnetic resonance spectroscopy), and the δ 13 C of respiratory CO 2 during incubations of organic horizons collected across boreal forests in different climate regions where soil C and N compositions differ. The experiments consisted of two treatments: soil incubated (1) with each organic horizon separately and (2) as a whole organic profile, permitting cross-horizon exchange of substrates during the incubation. The soils were incubated at 5 and 15 ∘ C for over 430 d. Enhanced microbial use of labile C-rich, but not N-rich, substrates were responsible for enhanced, whole-horizon respiratory responses to temperature relative to individual soil horizons. This impact of a labile C priming mechanism was most emergent in soils from the warmer region, consistent with these soils' lower C bioreactivity relative to soils from the colder region. Specifically, cross-horizon exchange within whole soil profiles prompted increases in mineralization of carbohydrates and more 13 C-enriched substrates and increased soil respiratory responses ...
    Keywords Ecology ; QH540-549.5 ; Life ; QH501-531 ; Geology ; QE1-996.5
    Subject code 550
    Language English
    Publishing date 2021-08-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  6. Article: Increasing chloride concentration causes retention of mercury in melted Arctic snow due to changes in photoreduction kinetics

    Mann, E.A / A. Steffen / N.J. O'Driscoll / S.E. Ziegler

    Journal of environmental sciences (China). 2018 June, v. 68

    2018  

    Abstract: Mercury (Hg) in the Arctic is a significant concern due to its bioaccumulative and neurotoxic properties, and the sensitivity of Arctic environments. Previous research has found high levels of Hg in snowpacks with high chloride (Cl−) concentrations. We ... ...

    Abstract Mercury (Hg) in the Arctic is a significant concern due to its bioaccumulative and neurotoxic properties, and the sensitivity of Arctic environments. Previous research has found high levels of Hg in snowpacks with high chloride (Cl−) concentrations. We hypothesised that Cl− would increase Hg retention by decreasing Hg photoreduction to Hg(0) in melted Arctic snow. To test this, changes in Hg photoreduction kinetics in melted Alert, NU snow were quantified with changing Cl− concentration and UV intensity. Snow was collected and melted in Teflon bottles in May 2014, spiked with 0–10μg/g Cl−, and irradiated with 3.52–5.78W·m−2 UV (280–400nm) radiation in a LuzChem photoreactor. Photoreduction rate constants (k) (0.14–0.59hr−1) had positive linear relationships with [Cl−], while photoreduced Hg amounts (Hg(II)red) had negative linear relationships with [Cl−] (1287–64pg in 200g melted snow). Varying UV and [Cl−] both altered Hg(II)red amounts, with more efficient Hg stabilisation by Cl− at higher UV intensity, while k can be predicted by Cl− concentration and/or UV intensity, depending on experimental parameters. Overall, with future projections for greater snowpack Cl− loading, our experimental results suggest that more Hg could be delivered to Arctic aquatic ecosystems by melted snow (smaller Hg(II)red expected), but the Hg in the melted snow that is photoreduced may do so more quickly (larger k expected).
    Keywords aquatic ecosystems ; bottles ; chlorides ; melting ; mercury ; neurotoxicity ; polytetrafluoroethylene ; snow ; snowmelt ; snowpack ; Arctic region
    Language English
    Dates of publication 2018-06
    Size p. 122-129.
    Publishing place Elsevier B.V.
    Document type Article
    ZDB-ID 1092300-7
    ISSN 1878-7320 ; 1001-0742
    ISSN (online) 1878-7320
    ISSN 1001-0742
    DOI 10.1016/j.jes.2018.01.006
    Database NAL-Catalogue (AGRICOLA)

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    In stock of ZB MED Bonn / Germany

    Z 7630: Show issues

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  7. Article ; Online: Biochemical and structural controls on the decomposition dynamics of boreal upland forest moss tissues

    M. Philben / S. Butler / S. A. Billings / R. Benner / K. A. Edwards / S. E. Ziegler

    Biogeosciences, Vol 15, Pp 6731-

    2018  Volume 6746

    Abstract: Mosses contribute an average of 20 % of boreal upland forest net primary productivity and are frequently observed to degrade slowly compared to vascular plants. If this is caused primarily by the chemical complexity of their tissues, moss decomposition ... ...

    Abstract Mosses contribute an average of 20 % of boreal upland forest net primary productivity and are frequently observed to degrade slowly compared to vascular plants. If this is caused primarily by the chemical complexity of their tissues, moss decomposition could exhibit high temperature sensitivity (measured as Q 10 ) due to high activation energy, which would imply that soil organic carbon (SOC) stocks derived from moss remains are especially vulnerable to decomposition with warming. Alternatively, the physical structure of the moss cell-wall biochemical matrix could inhibit decomposition, resulting in low decay rates and low temperature sensitivity. We tested these hypotheses by incubating mosses collected from two boreal forests in Newfoundland, Canada, for 959 days at 5 °C and 18 °C, while monitoring changes in the moss tissue composition using total hydrolyzable amino acid (THAA) analysis and 13 C nuclear magnetic resonance (NMR) spectroscopy. Less than 40 % of C was respired in all incubations, revealing a large pool of apparently recalcitrant C. The decay rate of the labile fraction increased in the warmer treatment, but the total amount of C loss increased only slightly, resulting in low Q 10 values (1.23–1.33) compared to L horizon soils collected from the same forests. NMR spectra were dominated by O-alkyl C throughout the experiment, indicating the persistence of potentially labile C. The accumulation of hydroxyproline (derived primarily from plant cell-wall proteins) and aromatic C indicates the selective preservation of biochemicals associated with the moss cell wall. This was supported by scanning electron microscope (SEM) images of the moss tissues, which revealed few changes in the physical structure of the cell wall after incubation. This suggests that the moss cell-wall matrix protected labile C from microbial decomposition, accounting for the low temperature sensitivity of moss decomposition despite low decay rates. Climate drivers of moss biomass and productivity, therefore, represent a ...
    Keywords Ecology ; QH540-549.5 ; Life ; QH501-531 ; Geology ; QE1-996.5
    Language English
    Publishing date 2018-11-01T00:00:00Z
    Publisher Copernicus Publications
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  8. Article: Mercury in Arctic snow: Quantifying the kinetics of photochemical oxidation and reduction

    Mann, E.A / M.L. Mallory / S.E. Ziegler / R. Tordon / N.J. O'Driscoll

    Science of the total environment. 2015 Mar. 15, v. 509-510

    2015  

    Abstract: Controlled experiments were performed with frozen and melted Arctic snow to quantify relationships between mercury photoreaction kinetics, ultra violet (UV) radiation intensity, and snow ion concentrations. Frozen (−10°C) and melted (4°C) snow ... ...

    Abstract Controlled experiments were performed with frozen and melted Arctic snow to quantify relationships between mercury photoreaction kinetics, ultra violet (UV) radiation intensity, and snow ion concentrations. Frozen (−10°C) and melted (4°C) snow samples from three Arctic sites were exposed to UV (280–400nm) radiation (1.26–5.78W·m−2), and a parabolic relationship was found between reduction rate constants in frozen and melted snow with increasing UV intensity. Total photoreduced mercury in frozen and melted snow increased linearly with greater UV intensity. Snow with the highest concentrations of chloride and iron had larger photoreduction and photooxidation rate constants, while also having the lowest Hg(0) production. Our results indicate that the amount of mercury photoreduction (loss from snow) is the highest at high UV radiation intensities, while the fastest rates of mercury photoreduction occurred at both low and high intensities. This suggests that, assuming all else is equal, earlier Arctic snow melt periods (when UV intensities are less intense) may result in less mercury loss to the atmosphere by photoreduction and flux, since less Hg(0) is photoproduced at lower UV intensities, thereby resulting in potentially greater mercury transport to aquatic systems with snowmelt.
    Keywords iron ; melting ; mercury ; photooxidation ; snow ; snowmelt ; ultraviolet radiation ; Arctic region
    Language English
    Dates of publication 2015-0315
    Size p. 115-132.
    Publishing place Elsevier B.V.
    Document type Article
    ZDB-ID 121506-1
    ISSN 1879-1026 ; 0048-9697
    ISSN (online) 1879-1026
    ISSN 0048-9697
    DOI 10.1016/j.scitotenv.2014.07.056
    Database NAL-Catalogue (AGRICOLA)

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    In stock of ZB MED Cologne/Königswinter

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