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Decomposition of soil organic matter under a changing climate

a matter of efficiency?

Bölscher, Tobias (2016). Decomposition of soil organic matter under a changing climate. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis agriculturae Sueciae, 1652-6880 ; 2016:85
ISBN 978-91-576-8672-5
eISBN 978-91-576-8673-2
[Doctoral thesis]

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Abstract

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.

Authors/Creators:Bölscher, Tobias
Title:Decomposition of soil organic matter under a changing climate
Subtitle:a matter of efficiency?
Series/Journal:Acta Universitatis agriculturae Sueciae (1652-6880)
Year of publishing :29 September 2016
Volume:2016:85
Number of Pages:53
Papers/manuscripts:
NumberReferences
IBölscher T, Wadsö L, Börjesson G, Herrmann AM (2016). Differences in substrate use efficiency: impacts of microbial community composition, land use management, and substrate complexity. Biology and Fertility of Soils 52, 547-559.
IIBölscher T, Ågren GI, Herrmann AM. Land use alters the temperature response of substrate-use efficiency. (manuscript)
IIIBölscher T, Paterson E, Freitag T, Thornton B, Herrmann AM. Temperature sensitivity of substrate-use efficiency is driven by microbial physiology rather than community composition. (manuscript)
IVHerrmann AM, Bölscher T (2015). Simultaneous screening of microbial energetics and CO₂ respiration in soil samples from different ecosystems. Soil Biology and Biochemistry 83, 88-92.
Place of Publication:Uppsala
Publisher:Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences
ISBN for printed version:978-91-576-8672-5
ISBN for electronic version:978-91-576-8673-2
ISSN:1652-6880
Language:English
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:P Natural resources > P33 Soil chemistry and physics
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 105 Earth and Related Environmental Sciences > Climate Research
(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Soil Science
Agrovoc terms:soil organic matter, degradation, efficiency, climate change, temperature, land use, soil microorganisms, calorimetry, carbon, models
Keywords:soil organic matter, substrate-use efficiency, temperature, land use, microbial community, substrate quality, isothermal calorimetry, carbon modelling
URN:NBN:urn:nbn:se:slu:epsilon-e-3678
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-e-3678
ID Code:13673
Faculty:NJ - Fakulteten för naturresurser och jordbruksvetenskap
Department:(NL, NJ) > Department of Chemistry and Biotechnology (140101-161231)
External funders:FORMAS
Deposited By: Tobias Bölscher
Deposited On:21 Sep 2016 11:16
Metadata Last Modified:21 Sep 2016 11:16

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