| 1. |
- Erhagen, Björn, et al.
(författare)
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Temperature response of litter and soil organic matter decomposition is determined by chemical composition of organic material
- 2013
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Ingår i: Global Change Biology. - : Wiley-Blackwell. - 1354-1013 .- 1365-2486. ; 19:12, s. 3858-3871
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Tidskriftsartikel (refereegranskat)abstract
- The global soil carbon pool is approximately three times larger than the contemporary atmospheric pool, therefore even minor changes to its integrity may have major implications for atmospheric CO2 concentrations. While theory predicts that the chemical composition of organic matter should constitute a master control on the temperature response of its decomposition, this relationship has not yet been fully demonstrated. We used laboratory incubations of forest soil organic matter (SOM) and fresh litter material together with NMR spectroscopy to make this connection between organic chemical composition and temperature sensitivity of decomposition. Temperature response of decomposition in both fresh litter and SOM was directly related to the chemical composition of the constituent organic matter, explaining 90% and 70% of the variance in Q10 in litter and SOM respectively. The Q10 of litter decreased with increasing proportions of aromatic and O-aromatic compounds, and increased with increased contents of alkyl- and O-alkyl carbons. In contrast, in SOM, decomposition was affected only by carbonyl compounds. To reveal why a certain group of organic chemical compounds affected the temperature sensitivity of organic matter decomposition in litter and SOM, a more detailed characterisation of the (13) C aromatic region using Heteronuclear Single Quantum Coherence (HSQC) was conducted. The results revealed considerable differences in the aromatic region between litter and SOM. This suggests that the correlation between chemical composition of organic matter and the temperature response of decomposition differed between litter and SOM. The temperature response of soil decomposition processes can thus be described by the chemical composition of its constituent organic matter, this paves the way for improved ecosystem modelling of biosphere feedbacks under a changing climate.
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| 2. |
- Serk, Henrik, 1980-, et al.
(författare)
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CO2 fertilization of Sphagnum peat mosses is modulated by water table level and other environmental factors
- 2021
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Ingår i: Plant, Cell and Environment. - : John Wiley & Sons. - 0140-7791 .- 1365-3040. ; 44:6, s. 1756-1768
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Tidskriftsartikel (refereegranskat)abstract
- Sphagnum mosses account for most accumulated dead organic matter in peatlands. Therefore, understanding their responses to increasing atmospheric CO2 is needed for estimating peatland C balances under climate change. A key process is photorespiration: a major determinant of net photosynthetic C assimilation that depends on the CO2 to O2 ratio. We used climate chambers to investigate photorespiratory responses of Sphagnum fuscum hummocks to recent increases in atmospheric CO2 (from 280 to 400 ppm) under different water table, temperature, and light intensity levels. We tested the photorespiratory variability using a novel method based on deuterium isotopomers (D6S/D6R ratio) of photosynthetic glucose. The effect of elevated CO2 on photorespiration was highly dependent on water table. At low water table (−20 cm), elevated CO2 suppressed photorespiration relative to C assimilation, thus substantially increasing the net primary production potential. In contrast, a high water table (~0 cm) favored photorespiration and abolished this CO2 effect. The response was further tested for Sphagnum majus lawns at typical water table levels (~0 and −7 cm), revealing no effect of CO2 under those conditions. Our results indicate that hummocks, which typically experience low water table levels, benefit from the 20th century's increase in atmospheric CO2.
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