The rise in atmospheric carbon dioxide (CO 2 ) concentration is a primary catalyst for global warming, and an estimated one fifth of the atmospheric CO 2 originates from soil sources. This is partially attributed to the activity of microorganisms, including bacteria, fungi, and other microorganisms that decompose organic matter in the soil utilizing oxygen, such as deceased plant materials. During this process, CO 2 is released into the atmosphere. Scientists refer to it as heterotrophic soil respiration.
Based on a recent study published in the scientific journal Nature Communications, a team of researchers from ETH Zurich, the Swiss Federal Institute for Forest, Snow and Landscape Research WSL, the Swiss Federal Institute of Aquatic Science and Technology Eawag, and the University of Lausanne has reached a significant conclusion. Their study indicates that emissions of CO 2 by soil microbes into the Earth's atmosphere are not only expected to increase but also accelerate on a global scale by the end of this century.
Using a projection, they find that by 2100, CO 2 emissions from soil microbes will escalate, potentially reaching an increase of up to about forty percent globally, compared to the current levels, under the worst-case climate scenario. “Thus, the projected rise in microbial CO 2 emissions will further contribute to the aggravation of global warming, emphasising the urgent need to get more accurate estimates of the heterotrophic respiration rates,” says Alon Nissan, the main author of the study and an ETH Postdoctoral Fellow at the ETH Zurich Institute of Environmental Engineering.
Soil moisture and temperature as key factors
These findings do not only confirm earlier studies but also provide more precise insights into the mechanisms and magnitude of heterotrophic soil respiration across different climatic zones. In contrast to other models that rely on numerous parameters, the novel mathematical model, developed by Alon Nissan, simplifies the estimation process by utilising only two crucial environmental factors: soil moisture and soil temperature.
The model represents a significant advancement as it encompasses all biophysically relevant levels, ranging from the micro-scales of soil structure and soil water distribution to plant communities like forests, entire ecosystems, climatic zones, and even the global scale. Peter Molnar, a professor at the ETH Institute of Environmental Engineering, highlights the significance of this theoretical model which complements large Earth System models, stating, "The model allows for a more straightforward estimation of microbial respiration rates based on soil moisture and soil temperature. Moreover, it enhances our understanding of how heterotrophic respiration in diverse climate regions contributes to global warming."
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