# Land-use alters the temperature response of microbial carbon-use efficiency

Tobias Bölscher, Göran I Ågren, Anke M Herrmann

► To cite this version:

Tobias Bölscher, Göran I Ågren, Anke M Herrmann. Land-use alters the temperature response of microbial carbon-use efficiency. 6th INTERNATIONAL SYMPOSIUM ON SOIL ORGANIC MATTER, British Society of Soil Sciences; Rothamsted Research, Sep 2017, Harpenden, United Kingdom. hal-04490194

HAL Id: hal-04490194

https://hal.science/hal-04490194v1

Submitted on 5 Mar 2024

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
# Land-use alters the temperature response of microbial carbon-use efficiency

Tobias Bölscher<fnref n="1" />,<fnref n="2" />, Göran I. Ågren<fnref n="3" /> and Anke M. Herrmann<fnref n="1" />,<fnref n="2" />

Microbial soil respiration is a major flux in global carbon dioxide (CO₂) emissions and small changes in the vast flux may seriously modify global climate. The amount of CO₂ released during decomposition of soil organic carbon (C) is determined by the microbial community's carbon-use efficiency (CUE). This property is defined as the fraction of microbial utilized C that is allocated to biosynthesis, with the remaining being respired. Therefore, CUE regulates C sequestration and experimental evidence suggests that it decreases with warming<fnref n="1" /> and varies among land-use systems<fnref n="2" />. Still, most soil C models consider CUE as a constant property. We hypothesized that (i) the temperature response of CUE differs across land-uses and (ii) that such dissimilarities significantly affects projections of soil C stocks under future temperature conditions.

To test our hypotheses, we applied a microbial thermodynamics approach<fnref n="2" />,<fnref n="3" /> using isothermal calorimetry and integrated our findings in a soil C model⁴. Soils were sampled from arable, grassland, ley-farming, and forest research sites exposed to a boreal climate (64°07′N, 19°27′E). The samples were amended with two carbon substrates of different molecular complexity and incubated at a set of temperatures ranging from 5 to 20 °C. CUEs were calculated from cumulative heat production and residual substrate<fnref n="2" /> when 15 % of the added substrate was utilized. Land-use specific temperature response functions were fitted to the CUE data and incorporated into the Q model⁴ using Swedish soils in Northern and Southern Sweden.

In the arable soil system, CUE stayed constant over the range from 5 to 20 °C, while in ley farming, grassland and forest soils CUEs were constant from 5 to 12.5 °C, but decreased non-linear beyond 12.5 °C. The decrease in CUE was most pronounced in forest soil, and our general findings were independent from the substrate amendment. Implementing this hitherto unrecognized phenomenon into the Q model revealed considerably different responses of soil C stocks across land-uses to changes in climate conditions. Our findings emphasize the need to understand temperature responses of microbial CUE. Further studies should establish reliable proxies for CUE which can be exploited in modelling approaches.

**Keywords:** soil organic carbon, carbon-use efficiency, temperature sensitivity, land use, isothermal calorimetry, soil carbon modelling

## References

1. Frey, S.D. et al., 2013. *Nature Climate Change* 3 395-398.

<footnote n="1">¹ Dept. of Soil and Environment, Swedish University of Agricultural Sciences, P.O. Box 7014, SE-750 07 Uppsala, Sweden</footnote>

<footnote n="2">² Dept. of Chemistry & Biotechnology, BioCenter, Swedish University of Agricultural Sciences, P.O. Box 7015, SE-750 07 Uppsala, Sweden</footnote>

<footnote n="3">³ Dept. of Ecology, Swedish University of Agricultural Sciences, P.O. Box 7044, SE-750 07 Uppsala, Sweden</footnote>
2. Bölscher, T. et al., 2016. *Biology and Fertility of Soils* 52(4) 547-559.

3. Herrmann, A.M. et al., 2014. *Environmental Science & Technology* 48(8):4344-4352.

4. Ågren, G.I. and Bosatta, E., 1998. *Theoretical Ecosystem Ecology – Understanding Element Cycling*. Cambridge University Press.