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Priming of the decomposition of ageing soil organic matter: concentration dependence and microbial control

Rousk, Johannes LU ; Hill, Paul W. and Jones, Davey L. (2015) In Functional Ecology 29(2). p.285-296
Abstract
The amount of carbon (C) stored in soil is an important regulator for the global climate and soil fertility and is the balance between formation and decomposition of soil organic matter (SOM). Decomposition of SOM can be powerfully affected by labile carbon (C) supplements in, for example, the rhizosphere. A stimulation of SOM mineralisation induced by labile C additions is termed priming', and the mechanisms for this phenomenon remain elusive. The most widely held explanation assigns priming to successional dynamics in r- and K-selected groups within the microbial community; groups which have also been connected with fungal (K-selected) and bacterial (r-selected) decomposers. New evidence has also suggested that recently formed SOM is... (More)
The amount of carbon (C) stored in soil is an important regulator for the global climate and soil fertility and is the balance between formation and decomposition of soil organic matter (SOM). Decomposition of SOM can be powerfully affected by labile carbon (C) supplements in, for example, the rhizosphere. A stimulation of SOM mineralisation induced by labile C additions is termed priming', and the mechanisms for this phenomenon remain elusive. The most widely held explanation assigns priming to successional dynamics in r- and K-selected groups within the microbial community; groups which have also been connected with fungal (K-selected) and bacterial (r-selected) decomposers. New evidence has also suggested that recently formed SOM is particularly sensitive to priming. We investigated (i) the labile C concentration dependence of SOM mineralisation, (ii) the susceptibility of differently aged SOM to priming and (iii) if priming is due to bacterial or fungal growth dynamics. To create an age gradient of traceable SOM, we spiked a pasture soil using C-14 glucose, and subsampled plots 1day, 2months, 5months and 13months after application (i.e. SOM aged 1day - 13months). Glucose (0-4000g C g(-1)) was added in subsequent laboratory experiments, and respiration, SOM mineralisation ((CO2)-C-14 evolution), bacterial growth rates (leucine incorporation) and fungal biomass (ergosterol) were tracked during ca. 1week. Mineralisation of SOM aged 2-13months showed similar labile C concentration dependencies, and priming increased mineralisation of SOM systematically by up to 350%. The glucose treatments induced variable microbial growth responses for differently aged SOM, which were unrelated to the priming effect. That successional dynamics in microbial r- and K-selected groups, or bacterial and fungal decomposers, respectively, underpinned priming was incompatible with the results obtained. An alternative explanation could be that SOM transformation by extracellular enzymes, for subsequent respiration, could be triggered by labile C. In conclusion, labile C primed the mineralisation of 2-13months aged SOM, and the mechanism for this priming was unrelated to microbial growth dynamics. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
global change biology, microbial community dynamics, microbial, decomposer ecology, microbial nutrient mining, priming effect, rhizosphere, soil carbon sequestration, soil organic carbon turnover
in
Functional Ecology
volume
29
issue
2
pages
285 - 296
publisher
Wiley-Blackwell
external identifiers
  • wos:000350051900015
  • scopus:84922629554
ISSN
1365-2435
DOI
10.1111/1365-2435.12377
project
MICCS - Molecular Interactions Controlling soil Carbon Sequestration
Interaction between fungi and bacteria in soil
Microbial carbon-use efficiency
Effect of environmental factors on fungal and bacterial growth in soil
language
English
LU publication?
yes
id
fe4beaf1-7afb-4f98-98c2-fdd2b5f6656f (old id 5305616)
date added to LUP
2015-04-23 16:31:16
date last changed
2017-10-22 03:31:45
@article{fe4beaf1-7afb-4f98-98c2-fdd2b5f6656f,
  abstract     = {The amount of carbon (C) stored in soil is an important regulator for the global climate and soil fertility and is the balance between formation and decomposition of soil organic matter (SOM). Decomposition of SOM can be powerfully affected by labile carbon (C) supplements in, for example, the rhizosphere. A stimulation of SOM mineralisation induced by labile C additions is termed priming', and the mechanisms for this phenomenon remain elusive. The most widely held explanation assigns priming to successional dynamics in r- and K-selected groups within the microbial community; groups which have also been connected with fungal (K-selected) and bacterial (r-selected) decomposers. New evidence has also suggested that recently formed SOM is particularly sensitive to priming. We investigated (i) the labile C concentration dependence of SOM mineralisation, (ii) the susceptibility of differently aged SOM to priming and (iii) if priming is due to bacterial or fungal growth dynamics. To create an age gradient of traceable SOM, we spiked a pasture soil using C-14 glucose, and subsampled plots 1day, 2months, 5months and 13months after application (i.e. SOM aged 1day - 13months). Glucose (0-4000g C g(-1)) was added in subsequent laboratory experiments, and respiration, SOM mineralisation ((CO2)-C-14 evolution), bacterial growth rates (leucine incorporation) and fungal biomass (ergosterol) were tracked during ca. 1week. Mineralisation of SOM aged 2-13months showed similar labile C concentration dependencies, and priming increased mineralisation of SOM systematically by up to 350%. The glucose treatments induced variable microbial growth responses for differently aged SOM, which were unrelated to the priming effect. That successional dynamics in microbial r- and K-selected groups, or bacterial and fungal decomposers, respectively, underpinned priming was incompatible with the results obtained. An alternative explanation could be that SOM transformation by extracellular enzymes, for subsequent respiration, could be triggered by labile C. In conclusion, labile C primed the mineralisation of 2-13months aged SOM, and the mechanism for this priming was unrelated to microbial growth dynamics.},
  author       = {Rousk, Johannes and Hill, Paul W. and Jones, Davey L.},
  issn         = {1365-2435},
  keyword      = {global change biology,microbial community dynamics,microbial,decomposer ecology,microbial nutrient mining,priming effect,rhizosphere,soil carbon sequestration,soil organic carbon turnover},
  language     = {eng},
  number       = {2},
  pages        = {285--296},
  publisher    = {Wiley-Blackwell},
  series       = {Functional Ecology},
  title        = {Priming of the decomposition of ageing soil organic matter: concentration dependence and microbial control},
  url          = {http://dx.doi.org/10.1111/1365-2435.12377},
  volume       = {29},
  year         = {2015},
}