| 1. |
- Soucemarianadin, Laure N., et al.
(författare)
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Two dimensional NMR spectroscopy for molecular characterization of soil organic matter : Application to boreal soils and litter
- 2017
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Ingår i: Organic Geochemistry. - : Elsevier BV. - 0146-6380 .- 1873-5290. ; 113, s. 184-195
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Tidskriftsartikel (refereegranskat)abstract
- Organic soils in boreal ecosystems and peatlands represent a huge global carbon pool and their composition strongly affects soil properties. Nevertheless, the characterization of soil organic matter (SOM) molecular composition, which is essential for elucidating soil carbon processes and turnover, is not easily achieved, and further advances in the area are greatly needed. Two dimensional (2D) liquid state H-1-C-13 nuclear magnetic resonance (NMR) spectroscopy has been used on dimethyl sulfoxide (DMSO) extracts of SOM to achieve molecular level characterization, with signals from many identifiable molecular groups observable. Here we show that a simple and fast sample preparation allows acquisition of 2D H-1-C-13 NMR spectra from extracts of plant litter and organic layers in boreal ecosystems, with fast data acquisition. Our 2D NMR spectra revealed several differences in the DMSO extracts of different tree litter samples, O-horizons of forest soil, peat-forming moss (Sphagnum) and peat. The results mirror established differences between OM in soils and litter of different forest ecosystems (e.g. between deciduous and coniferous litter) but also provide indications for research to untangle previously conflicting results (e.g. cutin degradation in soil or carbohydrate degradation in peat). Thus, combination of 2D NMR methods can greatly improve analysis of litter composition and SOM composition, thereby facilitating the elucidation of their roles in biogeochemical and ecological processes that are critical for foreseeing feedback mechanisms for SOM turnover as a result of global environmental change.
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| 2. |
- Öquist, Mats, et al.
(författare)
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The effect of temperature and substrate quality on the carbon use efficiency of saprotrophic decomposition
- 2017
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Ingår i: Plant and Soil. - : Springer Science and Business Media LLC. - 0032-079X .- 1573-5036. ; 414:1, s. 113-125
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Tidskriftsartikel (refereegranskat)abstract
- Background and aims: Mineralization of soil organic matter (SOM) constitutes a major carbon flux to the atmosphere. The carbon use efficiency (CUE) of the saprotrophic microorganisms mineralizing SOM is integral for soil carbon dynamics. Here we investigate how the CUE is affected by temperature, metabolic conditions, and the molecular complexity of the substrate.Methods: We incubated O-horizon soil samples (with either 13C–glucose or 13C–cellulose) from a boreal coniferous forest at 4, 9, 14, and 19 °C, and calculated CUEs based on the amount of 13C–CO2and 13C–labelled microbial biomass produced. The effects of substrate, temperature, and metabolic conditions (representing unlimited substrate supply and substrate limitation) on CUE were evaluated.Results: CUE from metabolizing glucose was higher as compared to cellulose. A slight decrease in CUE with increasing temperature was observed in glucose amended samples (but only in the range 9–19 °C), but not in cellulose amended samples. CUE differed significantly with metabolic conditions, i.e. CUE was higher during unlimited growth conditions as compared to conditions with substrate limitation.Conclusions: We conclude that it is integral to account for both differences in CUE during different metabolic phases, as well as complexity of substrate, when interpreting temperature dependence on CUE in incubation studies.
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