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Fatima Laggoun-défarge - One of the best experts on this subject based on the ideXlab platform.

  • Litter decomposition in peatlands is promoted by mixed plants
    Journal of Soils and Sediments, 2018
    Co-Authors: Fabien Leroy, Sébastien Gogo, Alexandre Buttler, Luca Bragazza, Fatima Laggoun-défarge
    Abstract:

    Purpose The carbon sink function of peatlands is primarily driven by a higher production than decomposition of the litter Sphagnum Mosses. The observed increase of vascular plants in peatlands could alter the decomposition rate and the carbon (C) cycle through a litter mixing effect, which is still poorly studied. Here, we examine the litter mixing effect of a peat Moss ( Sphagnum fallax ) and two vascular plants ( Pinus uncinata and Eriophorum vaginatum ) in the field and laboratory-based experiment. Materials and methods During the laboratory incubation, mass loss, CO_2 production, and dissolved organic carbon concentration were periodically monitored during 51 days. The collected data were then processed in a C dynamics model. The calculated enzymatic activity was correlated to the measured β-glucosidase activity in the litter. In the field experiment, mass loss and CO_2 production from litter bags were annually measured for 3 years. Results and discussion Both laboratory and field experiments clearly show that the litter mixture, i.e., Sphagnum - Pinus - Eriophorum , had a synergistic effect on decomposition by enhancing the mass loss. Such enhanced mass loss increased the water extractable C and CO_2 production in the litter mixture during the laboratory experiment. The synergistic effect was mainly controlled by the Sphagnum - Eriophorum mixture that significantly enhanced both mass loss and CO_2 production. Although the β-glucosidase activity is often considered as a major driver of decomposition, mixing the litters did not cause any increase of the activity of this exo-enzyme in the laboratory experiment suggesting that other enzymes can play an important role in the observed effect. Conclusions Mixing litters of graminoid and Sphagnum species led to a synergistic effect on litter decomposition. In a context of vegetation dynamics in response to environmental change, such a mixing effect could alter the C dynamics at a larger scale. Identifying the key mechanisms responsible for the synergistic effect on litter decomposition, with a specific focus on the enzymatic activities, is crucial to better predict the capacity of peatlands to act as C sinks.

Fabien Leroy - One of the best experts on this subject based on the ideXlab platform.

  • Litter decomposition in peatlands is promoted by mixed plants
    Journal of Soils and Sediments, 2018
    Co-Authors: Fabien Leroy, Sébastien Gogo, Alexandre Buttler, Luca Bragazza, Fatima Laggoun-défarge
    Abstract:

    Purpose The carbon sink function of peatlands is primarily driven by a higher production than decomposition of the litter Sphagnum Mosses. The observed increase of vascular plants in peatlands could alter the decomposition rate and the carbon (C) cycle through a litter mixing effect, which is still poorly studied. Here, we examine the litter mixing effect of a peat Moss ( Sphagnum fallax ) and two vascular plants ( Pinus uncinata and Eriophorum vaginatum ) in the field and laboratory-based experiment. Materials and methods During the laboratory incubation, mass loss, CO_2 production, and dissolved organic carbon concentration were periodically monitored during 51 days. The collected data were then processed in a C dynamics model. The calculated enzymatic activity was correlated to the measured β-glucosidase activity in the litter. In the field experiment, mass loss and CO_2 production from litter bags were annually measured for 3 years. Results and discussion Both laboratory and field experiments clearly show that the litter mixture, i.e., Sphagnum - Pinus - Eriophorum , had a synergistic effect on decomposition by enhancing the mass loss. Such enhanced mass loss increased the water extractable C and CO_2 production in the litter mixture during the laboratory experiment. The synergistic effect was mainly controlled by the Sphagnum - Eriophorum mixture that significantly enhanced both mass loss and CO_2 production. Although the β-glucosidase activity is often considered as a major driver of decomposition, mixing the litters did not cause any increase of the activity of this exo-enzyme in the laboratory experiment suggesting that other enzymes can play an important role in the observed effect. Conclusions Mixing litters of graminoid and Sphagnum species led to a synergistic effect on litter decomposition. In a context of vegetation dynamics in response to environmental change, such a mixing effect could alter the C dynamics at a larger scale. Identifying the key mechanisms responsible for the synergistic effect on litter decomposition, with a specific focus on the enzymatic activities, is crucial to better predict the capacity of peatlands to act as C sinks.

N. Silvan - One of the best experts on this subject based on the ideXlab platform.

  • Physical growing media characteristics of Sphagnum biomass dominated by Sphagnum fuscum (Schimp.) Klinggr.
    International Mire Conservation Group and International Peat Society, 2018
    Co-Authors: A. Kämäräinen, A. Simojoki, L. Lindén, K. Jokinen, N. Silvan
    Abstract:

    The surface biomass of Moss dominated by Sphagnum fuscum (Schimp.) Klinggr. (Rusty Bog-Moss) was harvested from a sparsely drained raised bog. Physical properties of the Sphagnum Moss were determined and compared with those of weakly and moderately decomposed peats. Water retention curves (WRC) and saturated hydraulic conductivities (Ks) are reported for samples of Sphagnum Moss with natural structure, as well as for samples that were cut to selected fibre lengths or compacted to different bulk densities. The gravimetric water retention results indicate that, on a dry mass basis, Sphagnum Moss can hold more water than both types of peat under equal matric potentials. On a volumetric basis, the water retention of Sphagnum Moss can be linearly increased by compacting at a gravimetric water content of 2 (g water / g dry mass). The bimodal water retention curve of Sphagnum Moss appears to be a consequence of the natural double porosity of the Moss matrix. The 6-parameter form of the double-porosity van Genuchten equation is used to describe the volumetric water retention of the Moss as its bulk density increases. Our results provide considerable insight into the physical growing media properties of Sphagnum Moss biomass

Silvan N. - One of the best experts on this subject based on the ideXlab platform.

  • Physical growing media characteristics of Sphagnum biomass dominated by Sphagnum fuscum (Schimp.) Klinggr
    2018
    Co-Authors: Kämäräinen A., Simojoki A., Linden L., Jokinen K., Silvan N.
    Abstract:

    The surface biomass of Moss dominated by Sphagnum fuscum (Schimp.) Klinggr. (Rusty Bog-Moss) was harvested from a sparsely drained raised bog. Physical properties of the Sphagnum Moss were determined and compared with those of weakly and moderately decomposed peats. Water retention curves (WRC) and saturated hydraulic conductivities (K-s) are reported for samples of Sphagnum Moss with natural structure, as well as for samples that were cut to selected fibre lengths or compacted to different bulk densities. The gravimetric water retention results indicate that, on a dry mass basis, Sphagnum Moss can hold more water than both types of peat under equal matric potentials. On a volumetric basis, the water retention of Sphagnum Moss can be linearly increased by compacting at a gravimetric water content of 2 (g water / g dry mass). The bimodal water retention curve of Sphagnum Moss appears to be a consequence of the natural double porosity of the Moss matrix. The 6-parameter form of the double-porosity van Genuchten equation is used to describe the volumetric water retention of the Moss as its bulk density increases. Our results provide considerable insight into the physical growing media properties of Sphagnum Moss biomass.Peer reviewe

Wayde N Martens - One of the best experts on this subject based on the ideXlab platform.

  • thermal decomposition of ammonium jarosite nh4 fe3 so4 2 oh 6
    Journal of Thermal Analysis and Calorimetry, 2006
    Co-Authors: Ray L. Frost, Rachaelanne Wills, Theo J Kloprogge, Wayde N Martens
    Abstract:

    Thermogravimetry combined with mass spectrometry has been used to study the thermal decomposition of a synthetic ammonium jarosite. Five mass loss steps are observed at 120, 260, 389, 510 and 541°C. Mass spectrometry through evolved gases confirms these steps as loss of water, dehydroxylation, loss of ammonia and loss of sulphate in two steps. Changes in the molecular structure of the ammonium jarosite were followed by infrared emission spectroscopy (IES). This technique allows the infrared spectrum at the elevated temperatures to be obtained. IES confirms the dehydroxylation to have taken place by 300°C and the ammonia loss by 450°C. Loss of the sulphate is observed by changes in band position and intensity after 500°C.

  • THERMAL DECOMPOSITION OF JAROSITES OF POTASSIUM, SODIUM AND LEAD
    Journal of Thermal Analysis and Calorimetry, 2005
    Co-Authors: Ray L. Frost, Matt L. Weier, Wayde N Martens
    Abstract:

    Jarosites are a group of minerals formed in evaporite deposits and form a component of efflorescence. As such the minerals can function as cation and heavy metal collectors. Thermogravimetry coupled to mass spectrometry has been used to study three Australian jarosites which are predominantly K, Na and Pb jarosites. Mass loss steps of K-jarosite occur over the 130 to 330 and 500 to 622°C temperature range and are attributed to dehydroxylation and desulphation. In contrast the behaviour of the thermal decomposition of Na-jarosite shows three mass loss steps at 215 to 230, 316 to 352 and 555 to 595°C. The first mass loss step for Na-jarosite is attributed to deprotonation. For Pb-jarosite two mass loss steps associated with dehydroxylation are observed at 390 and 418°C and a third mass loss step at 531°C is attributed to the loss of SO3. Thermal analysis is an excellent technique for the study of jarosites. The analysis depends heavily on the actual composition of the jarosite.