EGU2020-3537
https://doi.org/10.5194/egusphere-egu2020-3537
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Dark microbial CO2 fixation in temperate forest soils increases with CO2 concentration

Marie Spohn1, Karolin Müller2, Carmen Höschen3, Carsten W. Müller3, and Sven Marhan2
Marie Spohn et al.
  • 1University of Bayreuth, Bayreuth, Germany (marie.spohn@uni-bayreuth.de)
  • 2University of Hohenheim, Stuttgart, Germany
  • 3Technical University of Munich, Freising-Weihenstephan, Germany

Dark, that is, nonphototrophic, microbial CO2 fixation occurs in a large range of soils.
However, it is still not known whether dark microbial CO2 fixation substantially contributes
to the C balance of soils and what factors control this process. Therefore,
the objective of this study was to quantitate dark microbial CO2 fixation in temperate
forest soils, to determine the relationship between the soil CO2 concentration and
dark microbial CO2 fixation, and to estimate the relative contribution of different
microbial groups to dark CO2 fixation. For this purpose, we conducted a 13C-CO2 labeling
experiment. We found that the rates of dark microbial CO2 fixation were positively
correlated with the CO2 concentration in all soils. Dark microbial CO2 fixation
amounted to up to 320 μg C kg−1 soil day−1 in the Ah horizon. The fixation rates were
2.8–8.9 times higher in the Ah horizon than in the Bw1 horizon. Although the rates of
dark microbial fixation were small compared to the respiration rate (1.2%–3.9% of the
respiration rate), our findings suggest that organic matter formed by microorganisms
from CO2 contributes to the soil organic matter pool, especially given that microbial
detritus is more stable in soil than plant detritus. Phospholipid fatty acid analyses
indicated that CO2 was mostly fixed by gram-positive bacteria, and not by fungi. In
conclusion, our study shows that the dark microbial CO2 fixation rate in temperate
forest soils increases in periods of high CO2 concentrations, that dark microbial CO2
fixation is mostly accomplished by gram-positive bacteria, and that dark microbial
CO2 fixation contributes to the formation of soil organic matter.

Reference

Spohn M, Müller K, Höschen C, Mueller CW, Marhan S. Dark microbial CO2 fixation in temperate forest soils increases with CO2 concentration.
Glob Change Biol. 2019;00:1–10. https ://doi.org/10.1111/gcb.14937

How to cite: Spohn, M., Müller, K., Höschen, C., Müller, C. W., and Marhan, S.: Dark microbial CO2 fixation in temperate forest soils increases with CO2 concentration, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3537, https://doi.org/10.5194/egusphere-egu2020-3537, 2020