New Research on Carbon Cycling in the Mojave Desert
PhD candidate Anna Abramova and Professor Ronald Amundson in Hilgard Hall. Photo by Mathew Burciaga.
On the surface, the Mojave Desert may appear harsh and removed from the global carbon cycle, but its mineral-rich soils are deeply engaged in a significant carbon exchange. A new study published in Science Advances reveals a daily cycle where carbon dioxide (CO₂) is absorbed at night and released during the day, challenging the traditional understanding of soil carbon exchange, which primarily focuses on biological processes.
Key Findings:
- Carbon Adsorption Cycle: At night, cooler temperatures cause atmospheric CO₂ to bond with minerals in the soil through adsorption. When temperatures rise during the day, the CO₂ is released back into the atmosphere.
- New Perspectives: Lead author Anna Abramova suggests this cycle provides an alternative viewpoint on how soils interact with atmospheric carbon. Unlike the well-studied soil respiration—where plants convert CO₂ into energy—this process highlights a physical interaction between soil and gas.
Berkeley researchers in the Mojave. Photo courtesy of Ronald Amundson.
Unexpected Discoveries:
- Ronald Amundson, senior author of the study, explained that the team initially monitored the Mojave Desert’s soil sensors to examine CO₂ behavior. They found a net influx of CO₂ into the soil at night, a process not explained by biological activity.
- Jennifer Mills’ earlier findings indicated that nighttime CO₂ levels in soil dropped significantly, further supporting the idea that adsorption was occurring.
Laboratory Validation:
To assess the adsorption capacities of Mojave soils, researchers conducted three years of lab work, experimenting with soil samples at various temperatures and CO₂ concentrations. Abramova successfully measured how much CO₂ could be absorbed, confirming the findings from field data.
Abramova used liquid nitrogen to study adsorption rates. Photo by Mathew Burciaga.
Global Implications:
The team estimates that 1 to 3 gigatons of carbon flow into and out of desert soils globally each year, which represents a significant portion of annual human emissions. This adsorption process, which has also been suggested to occur in places like Antarctica and Mars, offers new dimensions for understanding carbon cycling in various ecosystems.
Future Directions:
Abramova plans to investigate whether the adsorption process differs among soils with varying levels of organic carbon or minerals. Additionally, the study offers a perspective that could refine current carbon models and contribute to innovative climate solutions.
Funding for this important research was provided by the California Energy Commission and the U.S. Department of Energy.
