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Rhizospheric influence on soil respiration and decomposition in a temperate Norway spruce stand

Ekberg, Anna LU ; Buchmann, Nina and Gleixner, Gerd (2007) In Soil Biology & Biochemistry 39(8). p.2103-2110
Abstract
Assessments of terrestrial carbon fluxes require a thorough understanding of links between primary production, soil respiration and carbon loss through drainage. In this study, stem girdling was used to terminate autotrophic soil respiration including rhizosphere respiration and root exudation in a temperate Norway spruce stand. Rates of soil respiration and dissolved organic carbon (DOC) formation were measured in the second year after girdling, comparing an intact plant rhizosphere continuum with an exclusive decomposer system. The molecular and isotopic composition of DOC in the soil solution was analysed with a coupled Py-GC/MS-C-IRMS system to distinguish between the carbon sources of dissolved carbon. Pyrolysis products were grouped... (More)
Assessments of terrestrial carbon fluxes require a thorough understanding of links between primary production, soil respiration and carbon loss through drainage. In this study, stem girdling was used to terminate autotrophic soil respiration including rhizosphere respiration and root exudation in a temperate Norway spruce stand. Rates of soil respiration and dissolved organic carbon (DOC) formation were measured in the second year after girdling, comparing an intact plant rhizosphere continuum with an exclusive decomposer system. The molecular and isotopic composition of DOC in the soil solution was analysed with a coupled Py-GC/MS-C-IRMS system to distinguish between the carbon sources of dissolved carbon. Pyrolysis products were grouped according to their precursor origins: polysaccharides, proteins or of mixed origin (mainly derivates of lignins and proteins). When dead roots became available for decomposition, rates of heterotrophic soil respiration in girdling plots peaked at 6.5 mu mol m(-2) s(-1), comparable to peak rates of total soil respiration (autotrophic and heterotrophic) in control plots, 6.1 mu mol m(-2) s(-1). A significant response of soil respiration to temperature was found in control plots only, showing that an unlimiting supply of organic substrates for microbial respiration may mask any temperature effects. The enhanced decomposition in girdled plots was further supported by the isotopic composition of DOC in soil solution; all three precursor groups became isotopically enriched as the growing season progressed (polysaccharides by 2.3 parts per thousand, proteins by 1.9 parts per thousand, mixed origin group by 2.2 parts per thousand). This indicates a trophic level shift due to incorporation of organic substrate into the microbial food chain. In the control plots' mixed origin fraction, the isotopic composition changed over time from a signature resembling that of lignin (-28.9 parts per thousand) to one similar of the protein fraction (-25.7 parts per thousand). Significant temporal changes of structural DOC composition occurred in the girdling plots only. These results suggest that changes in the microbial community and in decomposition rates occurred in both girdled and control plots in the following ways: (i) increased substrate availability (dead roots) gave rise to generally enhanced performance of the decomposer community in girdled plots, (ii) root-derived exudates probably contributed to enhanced decomposition of recalcitrant lignin in the control plots and (iii) the structural composition of DOC seemed to be more a result of decomposition than of plant root exudation in all plots. (C) 2007 Elsevier Ltd. All rights reserved. (Less)
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author
organization
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type
Contribution to journal
publication status
published
subject
keywords
pyrolysis-GC/MS-IRMS, isotopes, stable C, dissolved organic carbon, forest girdling, soil CO2 efflux, mass spectrometry
in
Soil Biology & Biochemistry
volume
39
issue
8
pages
2103 - 2110
publisher
Elsevier
external identifiers
  • wos:000247295800026
  • scopus:34248512247
ISSN
0038-0717
DOI
10.1016/j.soilbio.2007.03.024
language
English
LU publication?
yes
id
ee0649b4-35a1-4b86-b0df-5183221876ad (old id 648236)
date added to LUP
2007-12-07 14:17:22
date last changed
2017-08-20 04:21:52
@article{ee0649b4-35a1-4b86-b0df-5183221876ad,
  abstract     = {Assessments of terrestrial carbon fluxes require a thorough understanding of links between primary production, soil respiration and carbon loss through drainage. In this study, stem girdling was used to terminate autotrophic soil respiration including rhizosphere respiration and root exudation in a temperate Norway spruce stand. Rates of soil respiration and dissolved organic carbon (DOC) formation were measured in the second year after girdling, comparing an intact plant rhizosphere continuum with an exclusive decomposer system. The molecular and isotopic composition of DOC in the soil solution was analysed with a coupled Py-GC/MS-C-IRMS system to distinguish between the carbon sources of dissolved carbon. Pyrolysis products were grouped according to their precursor origins: polysaccharides, proteins or of mixed origin (mainly derivates of lignins and proteins). When dead roots became available for decomposition, rates of heterotrophic soil respiration in girdling plots peaked at 6.5 mu mol m(-2) s(-1), comparable to peak rates of total soil respiration (autotrophic and heterotrophic) in control plots, 6.1 mu mol m(-2) s(-1). A significant response of soil respiration to temperature was found in control plots only, showing that an unlimiting supply of organic substrates for microbial respiration may mask any temperature effects. The enhanced decomposition in girdled plots was further supported by the isotopic composition of DOC in soil solution; all three precursor groups became isotopically enriched as the growing season progressed (polysaccharides by 2.3 parts per thousand, proteins by 1.9 parts per thousand, mixed origin group by 2.2 parts per thousand). This indicates a trophic level shift due to incorporation of organic substrate into the microbial food chain. In the control plots' mixed origin fraction, the isotopic composition changed over time from a signature resembling that of lignin (-28.9 parts per thousand) to one similar of the protein fraction (-25.7 parts per thousand). Significant temporal changes of structural DOC composition occurred in the girdling plots only. These results suggest that changes in the microbial community and in decomposition rates occurred in both girdled and control plots in the following ways: (i) increased substrate availability (dead roots) gave rise to generally enhanced performance of the decomposer community in girdled plots, (ii) root-derived exudates probably contributed to enhanced decomposition of recalcitrant lignin in the control plots and (iii) the structural composition of DOC seemed to be more a result of decomposition than of plant root exudation in all plots. (C) 2007 Elsevier Ltd. All rights reserved.},
  author       = {Ekberg, Anna and Buchmann, Nina and Gleixner, Gerd},
  issn         = {0038-0717},
  keyword      = {pyrolysis-GC/MS-IRMS,isotopes,stable C,dissolved organic carbon,forest girdling,soil CO2 efflux,mass spectrometry},
  language     = {eng},
  number       = {8},
  pages        = {2103--2110},
  publisher    = {Elsevier},
  series       = {Soil Biology & Biochemistry},
  title        = {Rhizospheric influence on soil respiration and decomposition in a temperate Norway spruce stand},
  url          = {http://dx.doi.org/10.1016/j.soilbio.2007.03.024},
  volume       = {39},
  year         = {2007},
}