Bacteria and fungi respond differently to multifactorial climate change in a temperate heathland, traced with 13C-glycine and FACE CO2.
It is vital to understand responses of soil microorganisms to predicted climate changes, as these directly control soil carbon (C) dynamics. The rate of turnover of soil organic carbon is mediated by soil microorganisms whose activity may be affected by climate change. After one year of multifactorial climate change treatments, at an undisturbed temperate heathland, soil microbial community dynamics were investigated by injection of a very small concentration (5.12 µg C g(-1) soil) of (13)C-labeled glycine ((13)C2, 99 atom %) to soils in situ. Plots were treated with elevated temperature (+1°C, T), summer drought (D) and elevated atmospheric carbon dioxide (510 ppm [CO2]), as well as combined treatments (TD, TCO2, DCO2 and TDCO2). The (13)C enrichment of respired CO2 and of phospholipid fatty acids (PLFAs) was determined after 24 h. (13)C-glycine incorporation into the biomarker PLFAs for specific microbial groups (Gram positive bacteria, Gram negative bacteria, actinobacteria and fungi) was quantified using gas chromatography-combustion-stable isotope ratio mass spectrometry (GC-C-IRMS). Gram positive bacteria opportunistically utilized the freshly added glycine substrate, i.e. incorporated (13)C in all treatments, whereas fungi had minor or no glycine derived (13)C-enrichment, hence slowly reacting to a new substrate. The effects of elevated CO2 did suggest increased direct incorporation of glycine in microbial biomass, in particular in G(+) bacteria, in an ecosystem subjected to elevated CO2. Warming decreased the concentration of PLFAs in general. The FACE CO2 was (13)C-depleted (δ(13)C = 12.2‰) compared to ambient (δ(13)C = ∼-8‰), and this enabled observation of the integrated longer term responses of soil microorganisms to the FACE over one year. All together, the bacterial (and not fungal) utilization of glycine indicates substrate preference and resource partitioning in the microbial community, and therefore suggests a diversified response pattern to future changes in substrate availability and climatic factors.
Department of Biology, University of Copenhagen, Copenhagen, Denmark.
Louise C
LC
Andresen
Sustainable Soils and Grassland Systems Department, Rothamsted Research-North Wyke, Okehampton, United Kingdom.
Jennifer A J
JA
Dungait
Sustainable Soils and Grassland Systems Department, Rothamsted Research-North Wyke, Okehampton, United Kingdom ; Institute of Bio- and Geosciences, Forschungszentrum Jülich, Jülich, Germany.
Roland
R
Bol
Chemical and Biochemical Engineering, Technical University of Denmark, Kongens Lyngby, Denmark.
Merete B
MB
Selsted
Chemical and Biochemical Engineering, Technical University of Denmark, Kongens Lyngby, Denmark.
Per
P
Ambus
Department of Biology, University of Copenhagen, Copenhagen, Denmark.
Anders
A
Michelsen
D018407:Bacterial Physiological Phenomena; D002245:Carbon Dioxide / Q000737:chemistry*; D002247:Carbon Isotopes; D057231:Climate Change; D005658:Fungi / Q000502:physiology*; D008401:Gas Chromatography-Mass Spectrometry; D005998:Glycine / Q000737:chemistry*; D012988:Soil Microbiology
D002247:Carbon Isotopes; D002245:Carbon Dioxide; D005998:Glycine