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Microbial control of soil organic matter mineralization responses to labile carbon in subarctic climate change treatments

Rousk, Kathrin LU ; Michelsen, Anders and Rousk, Johannes LU (2016) In Global Change Biology 22(12). p.4150-4161
Abstract

Half the global soil carbon (C) is held in high-latitude systems. Climate change will expose these to warming and a shift towards plant communities with more labile C input. Labile C can also increase the rate of loss of native soil organic matter (SOM); a phenomenon termed ‘priming’. We investigated how warming (+1.1 °C over ambient using open top chambers) and litter addition (90 g m−2 yr−1) treatments in the subarctic influenced the susceptibility of SOM mineralization to priming, and its microbial underpinnings. Labile C appeared to inhibit the mineralization of C from SOM by up to 60% within hours. In contrast, the mineralization of N from SOM was stimulated by up to 300%. These responses occurred rapidly and... (More)

Half the global soil carbon (C) is held in high-latitude systems. Climate change will expose these to warming and a shift towards plant communities with more labile C input. Labile C can also increase the rate of loss of native soil organic matter (SOM); a phenomenon termed ‘priming’. We investigated how warming (+1.1 °C over ambient using open top chambers) and litter addition (90 g m−2 yr−1) treatments in the subarctic influenced the susceptibility of SOM mineralization to priming, and its microbial underpinnings. Labile C appeared to inhibit the mineralization of C from SOM by up to 60% within hours. In contrast, the mineralization of N from SOM was stimulated by up to 300%. These responses occurred rapidly and were unrelated to microbial successional dynamics, suggesting catabolic responses. Considered separately, the labile C inhibited C mineralization is compatible with previously reported findings termed ‘preferential substrate utilization’ or ‘negative apparent priming’, while the stimulated N mineralization responses echo recent reports of ‘real priming’ of SOM mineralization. However, C and N mineralization responses derived from the same SOM source must be interpreted together: This suggested that the microbial SOM-use decreased in magnitude and shifted to components richer in N. This finding highlights that only considering SOM in terms of C may be simplistic, and will not capture all changes in SOM decomposition. The selective mining for N increased in climate change treatments with higher fungal dominance. In conclusion, labile C appeared to trigger catabolic responses of the resident microbial community that shifted the SOM mining to N-rich components; an effect that increased with higher fungal dominance. Extrapolating from these findings, the predicted shrub expansion in the subarctic could result in an altered microbial use of SOM, selectively mining it for N-rich components, and leading to a reduced total SOM-use.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
bacterial growth, biogeochemistry, fungal growth, microbial ecology, nitrogen cycling, nitrogen limitation, soil carbon sequestration, the priming effect
in
Global Change Biology
volume
22
issue
12
pages
12 pages
publisher
Wiley-Blackwell
external identifiers
  • scopus:84995704288
  • wos:000387813300026
ISSN
1354-1013
DOI
10.1111/gcb.13296
language
English
LU publication?
yes
id
07211abc-9ce2-404b-b0fa-8a92703f1ad3
date added to LUP
2016-12-02 12:43:19
date last changed
2017-09-24 05:03:53
@article{07211abc-9ce2-404b-b0fa-8a92703f1ad3,
  abstract     = {<p>Half the global soil carbon (C) is held in high-latitude systems. Climate change will expose these to warming and a shift towards plant communities with more labile C input. Labile C can also increase the rate of loss of native soil organic matter (SOM); a phenomenon termed ‘priming’. We investigated how warming (+1.1 °C over ambient using open top chambers) and litter addition (90 g m<sup>−2</sup> yr<sup>−1</sup>) treatments in the subarctic influenced the susceptibility of SOM mineralization to priming, and its microbial underpinnings. Labile C appeared to inhibit the mineralization of C from SOM by up to 60% within hours. In contrast, the mineralization of N from SOM was stimulated by up to 300%. These responses occurred rapidly and were unrelated to microbial successional dynamics, suggesting catabolic responses. Considered separately, the labile C inhibited C mineralization is compatible with previously reported findings termed ‘preferential substrate utilization’ or ‘negative apparent priming’, while the stimulated N mineralization responses echo recent reports of ‘real priming’ of SOM mineralization. However, C and N mineralization responses derived from the same SOM source must be interpreted together: This suggested that the microbial SOM-use decreased in magnitude and shifted to components richer in N. This finding highlights that only considering SOM in terms of C may be simplistic, and will not capture all changes in SOM decomposition. The selective mining for N increased in climate change treatments with higher fungal dominance. In conclusion, labile C appeared to trigger catabolic responses of the resident microbial community that shifted the SOM mining to N-rich components; an effect that increased with higher fungal dominance. Extrapolating from these findings, the predicted shrub expansion in the subarctic could result in an altered microbial use of SOM, selectively mining it for N-rich components, and leading to a reduced total SOM-use.</p>},
  author       = {Rousk, Kathrin and Michelsen, Anders and Rousk, Johannes},
  issn         = {1354-1013},
  keyword      = {bacterial growth,biogeochemistry,fungal growth,microbial ecology,nitrogen cycling,nitrogen limitation,soil carbon sequestration,the priming effect},
  language     = {eng},
  month        = {12},
  number       = {12},
  pages        = {4150--4161},
  publisher    = {Wiley-Blackwell},
  series       = {Global Change Biology},
  title        = {Microbial control of soil organic matter mineralization responses to labile carbon in subarctic climate change treatments},
  url          = {http://dx.doi.org/10.1111/gcb.13296},
  volume       = {22},
  year         = {2016},
}