EGU24-8685, updated on 08 Mar 2024
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Insights into the role of the environmental setting versus microbial actors for soil carbon cycling

Daniel Wasner1, Joerg Schnecker2, Xingguo Han3, Aline Frossard3, Erick Zagal Venegas4, and Sebastian Doetterl1
Daniel Wasner et al.
  • 1Soil Resources, Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland
  • 2Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
  • 3Forest Soils and Biogeochemistry, Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Birmensdorf, Switzerland
  • 4Department of Soil and Natural Resources, Faculty of Agronomy, University of Concepción, Concepción, Chile

Soil microbes perform important functions in the soil organic carbon (SOC) cycle and soil microbial decomposition activity is a major determinant of the carbon budget of a soil. It is well-established that soil microbial physiology is directly affected by temperature and moisture. However, it is less clear to what extent the environmental setting (i.e. long-term climatic conditions, soil physicochemistry) vs. the microbial actors (i.e. soil bacterial and fungal community composition) control the cycling of SOC in the absence of strong direct physiological constraints such as temperature and moisture limitation.

To address this knowledge gap, we used 35 grassland topsoils (0 – 10 cm) from 10 WRB major soil groups along a north-south transect in Chile, which ranged from arid steppe to tundra. We compiled climatic data and relevant physicochemical soil properties, together with an in depth characterization of OM quality. We then incubated the soils for 1 week in conditions favorable for microbial activity (20 °C, 50 % of water holding capacity). After incubation, we quantified soil microbial carbon and nitrogen, enzyme kinetics of three groups of relevant extracellular enzymes, basal heterotrophic respiration as well as microbial growth rates and carbon use efficiencies by incorporation of 18O into DNA. In addition, we characterized the microbial actors by DNA extraction and Illumina barcoding of a region of the 16S rRNA gene (bacteria) and a section of the ITS region (fungi). Finally, to investigate how strongly the measured microbial SOC functions were linked with the environmental setting vs. the microbial actors, we applied three different cross-validated regression approaches.

The resulting data highlights the links between environment, microbial community composition and SOC cycle functions under conditions without direct temperature and moisture limitation. Our findings show that the environmental setting controlled the amount of microbial biomass, and in extension biomass dependent SOC cycle functions such as heterotrophic respiration. In  contrast, microbial community composition was a better predictor of SOC cycle functions that are independent of microbial biomass such as carbon use efficiency and relative microbial growth rates. These insights help to disentangle the roles of the environmental setting and the microbial actors in the context of microbial SOC cycle functions.

How to cite: Wasner, D., Schnecker, J., Han, X., Frossard, A., Zagal Venegas, E., and Doetterl, S.: Insights into the role of the environmental setting versus microbial actors for soil carbon cycling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8685,, 2024.