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Decomposition of so...
Decomposition of soil organic matter under a changing climate : a matter of efficiency?
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- Bölscher, Tobias (författare)
- Swedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för kemi,Department of Chemistry
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(creator_code:org_t)
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- ISBN 9789157686725
- 2016
- Engelska.
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Serie: Acta Universitatis Agriculturae Sueciae, 1652-6880
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Abstract
Ämnesord
Stäng
- Soil organic matter is the largest carbon (C) pool in the terrestrial C cycle, and soil CO₂ emissions surpass anthropogenic emissions from fossil fuel combustion by a factor of nine. Therefore, mechanisms controlling C stabilisation in soils and its feedback to climate change are widely debated. During decomposition, microbial substrate-use efficiency is an important property because it determines the allocation of substrate C to biosynthesis and respiratory losses. High efficiency values indicate that C primarily remains in soils while low efficiency implies that C is primarily lost into the atmosphere. Despite empirical evidence that efficiency is temperature sensitive, traditional Earth system models treat this property as a constant. The aim of this thesis was to improve our mechanistic understanding of drivers regulating substrate-use efficiency with special consideration to climate change. It investigated the impacts of (i) temperature, (ii) microbial community composition and (iii) substrate quality on substrate-use efficiency. Within the thesis, a microbial energetics approach was applied and further developed using isothermal calorimetry. Further, the thesis compared common approaches for measuring microbial substrate-use efficiency, and the implications of the resultant empirical data for projected C stocks were tested using a modelling approach. Substrate-use efficiency was generally temperature sensitive and decreased with increasing temperature. The observed temperature responses were non-linear and varied across land use management systems. The changes in substrate-use efficiency with temperature were driven rather by changes in microbial physiology than by shifts in active microbial communities. Nevertheless, fungi and Gram-negative bacteria tended towards relatively higher efficiencies. Efficiencies varied among utilised substrates, but substrate quality per se was a poor proxy for efficiency. Projected losses from soil C stocks varied across land use management systems and were up to 39 % and 15 % for grassland and forest systems, respectively. Results from the modelling approach confirmed that substrate-use efficiency is one of the factors to which soil C stocks react most sensitively. Findings from this thesis emphasise the importance of furthering our understanding of substrate-use efficiency for reliable climate projections.
Ämnesord
- LANTBRUKSVETENSKAPER -- Lantbruksvetenskap, skogsbruk och fiske -- Markvetenskap (hsv//swe)
- AGRICULTURAL SCIENCES -- Agriculture, Forestry and Fisheries -- Soil Science (hsv//eng)
- NATURVETENSKAP -- Geovetenskap och miljövetenskap -- Klimatforskning (hsv//swe)
- NATURAL SCIENCES -- Earth and Related Environmental Sciences -- Climate Research (hsv//eng)
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