Plant and Soil

, Volume 376, Issue 1, pp 61–73

Translocation and turnover of rhizodeposit carbon within soil microbial communities of an extensive grassland ecosystem

  • Wajira K. Balasooriya
  • Karolien Denef
  • Dries Huygens
  • Pascal Boeckx
Regular Article

DOI: 10.1007/s11104-012-1343-z

Cite this article as:
Balasooriya, W.K., Denef, K., Huygens, D. et al. Plant Soil (2014) 376: 61. doi:10.1007/s11104-012-1343-z

Abstract

Background and Aims

A substantial amount of photosynthesized plant-C is allocated belowground in grassland ecosystems where it influences the structure and function of the soil microbial community with potential implications for C cycling and storage. We applied stable isotope probing of microbial PLFAs and repeated soil sampling in a grassland over a period of 1 year to assess the role of microbial communities in the cycling of rhizodeposit-C.

Methods

Pulse-labeling with 13CO2 was performed in a grassland site near Gent (Belgium). Soil samples were taken 24 h, 1 week, 1 month, 4 months, 9 months and 1 year following labeling and analyzed for 13C in soil, roots and microbial PLFAs.

Results

C enrichment of PLFAs occurred rapidly (within 24 h) but temporally varied across microbial groups. PLFAs indicative for fungi and gram-negative bacteria showed a faster 13C uptake compared to gram-positive bacteria and actinomycetes. However, the relative 13C concentrations of the latter communities increased after 1 week, while those of fungi decreased and those of gram-negative bacteria remained constant. PLFA 13C mean residence times were much shorter for fungi compared to bacteria and actinomycetes.

Conclusions

Our results indicate temporally varying rhizodeposit-C uptake by different microbial groups, and faster turnover rates of mycorrhizal versus saprotrophic fungi and fungi versus bacteria. Fungi appeared to play a major role in the initial processing and possible rapid channeling of rhizodeposit-C into the soil microbial community. Actinomycetes and gram-positive bacteria appeared to have a delayed utilization of rhizodeposit-C or to prefer other C sources upon rhizodeposition.

Keywords

13C Pulse-labelingRhizodepositionSoil microbial community structureSIP-PLFAMicrobial carbon turnover

Abbreviations

PLFA

Phospholipid fatty acid

FAME

Fatty acid methyl ester

SIP

Stable isotope probing

GC-c-IRMS

Gas chromatography combustion isotope ratio mass spectrometry

MRT

Mean residence time

Copyright information

© Springer Science+Business Media B.V. 2012

Authors and Affiliations

  • Wajira K. Balasooriya
    • 1
  • Karolien Denef
    • 2
  • Dries Huygens
    • 1
    • 3
  • Pascal Boeckx
    • 1
  1. 1.Isotope Bioscience Laboratory—ISOFYSGhent UniversityGhentBelgium
  2. 2.Natural Resource Ecology LaboratoryColorado State UniversityFort CollinsUSA
  3. 3.Institute of Agricultural Engineering and Soil Science, Faculty of Agricultural SciencesUniversidad Austral de ChileValdiviaChile