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Dark microbial CO 2 fixation in temperate forest soils increases with CO 2 concentration.

Authors :
Spohn M
Müller K
Höschen C
Mueller CW
Marhan S
Source :
Global change biology [Glob Chang Biol] 2020 Mar; Vol. 26 (3), pp. 1926-1935. Date of Electronic Publication: 2019 Dec 31.
Publication Year :
2020

Abstract

Dark, that is, nonphototrophic, microbial CO <subscript>2</subscript> fixation occurs in a large range of soils. However, it is still not known whether dark microbial CO <subscript>2</subscript> 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 CO <subscript>2</subscript> fixation in temperate forest soils, to determine the relationship between the soil CO <subscript>2</subscript> concentration and dark microbial CO <subscript>2</subscript> fixation, and to estimate the relative contribution of different microbial groups to dark CO <subscript>2</subscript> fixation. For this purpose, we conducted a <superscript>13</superscript> C-CO <subscript>2</subscript> labeling experiment. We found that the rates of dark microbial CO <subscript>2</subscript> fixation were positively correlated with the CO <subscript>2</subscript> concentration in all soils. Dark microbial CO <subscript>2</subscript> fixation amounted to up to 320 µg C kg <superscript>-1</superscript>  soil day <superscript>-1</superscript> 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 CO <subscript>2</subscript> 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 CO <subscript>2</subscript> was mostly fixed by gram-positive bacteria, and not by fungi. In conclusion, our study shows that the dark microbial CO <subscript>2</subscript> fixation rate in temperate forest soils increases in periods of high CO <subscript>2</subscript> concentrations, that dark microbial CO <subscript>2</subscript> fixation is mostly accomplished by gram-positive bacteria, and that dark microbial CO <subscript>2</subscript> fixation contributes to the formation of soil organic matter.<br /> (© 2019 The Authors. Global Change Biology published by John Wiley & Sons Ltd.)

Details

Language :
English
ISSN :
1365-2486
Volume :
26
Issue :
3
Database :
MEDLINE
Journal :
Global change biology
Publication Type :
Academic Journal
Accession number :
31774225
Full Text :
https://doi.org/10.1111/gcb.14937