What was your research topic? What results did you get?

During my doctorate studies, I investigated how microorganisms regulate carbon cycling in soil and how understanding this can help us to predict changes in the Earth’s biogeochemistry (e.g. soil nutrients) and climate. Understanding the accelerated changes that the planet is experiencing and using that information to design adaptation and mitigation strategies is an unprecedented priority for humanity.

When microorganisms in soil decompose organic matter, they emit CO₂ into the atmosphere. This process is known as soil respiration. Each year, soils emit approximately 95 trillion tons of carbon to the atmosphere. In the last decades, global soil respiration has been increasing at a rate of 100 million tons of carbon every year. Recent evidence suggests that increases in global soil respiration could be associated with responses of soil microorganisms to global warming and other changes in climate. Understanding these responses can help us to predict how much carbon is going to be emitted from soils in a warmer future and how that is going to affect the Earth’s climate. 

In my thesis, I studied the responses of soil microorganisms to changes in environmental conditions such as temperature and moisture, and the consequences of these responses for soil CO₂ emissions. To do this, I used different laboratory, field, and modeling techniques. Much of my work was focused on understanding how changes in the environment cause microorganisms in the soil to be metabolically active (i.e. eating, growing, and respiring) or inactive (i.e. in a state of dormancy where they do not decompose organic matter and minimize their respiration). In general, I found that rapid changes in soil respiration rates (i.e. respiration pulses after wetting dry soil) are partly caused by activation of dormant microorganisms in the soil and not by rapid changes in the total amount of microorganisms in soil, as is generally assumed.

Together with several collaborators, we modified a mathematical model (such as those used to make climate predictions and inform policies such as those discussed in the Paris agreement) to account for microbial dormancy and found that models that do not consider activation and deactivation of microorganisms in soil underestimate soil CO₂ emissions, especially under warming and drought conditions.

In conclusion, the results of my thesis suggest that climate-driven activation of dormant microorganisms in soil could be contributing to increase global soil respiration and to accelerate global warming. An intensification of global warming, as projected for the following decades, could further stimulate microbial activity and respiration in soil.