Sara Winterfeldt

Doctoral Student

Research areas and keywords


  • microbial ecology, climate change, drought


Soil microorganisms as bacteria and fungi play an important role in regulating the terrestrial C cycle. Microorganisms contribute to C sequestration by their growth and release C to the atmosphere via respiration; thus their activity determine if soils become a sink or source of C. One of the strongest factors controlling microbial activity is moisture and more frequent and intense drought and rainfall events are expected due to climate change. In turn, drying and rewetting induce large C dynamics, hence it is critical to understand the microbial responses underpinning this climate feedback. Yet, how several environmental factors influence microbial responses to moisture fluctuations is still unknown.

The main interest of my PhD is to understand how soil microbial communities and their processes are affected by drying and rewetting events. I am particularly interested in how the environment such as pH, SOM, soil structure, and precipitation shape microbial growth and respiration responses. I want to understand how microbes respond to drying and rewetting across climate gradients as well as environmental gradients. In addition, I want to find out how and if microbial communities adapt to moisture fluctuations and what consequences it has for future global warming. My research will increase our understanding of how drying and rewetting affect terrestrial C cycling and improve ecosystem models to predict climatic scenarios.

To achieve this, I will study microbial growth and respiration responses to drying and rewetting cycles both in field experiments and laboratory microcosms experiments. I will investigate soils with different precipitation regimes using natural climate gradients together with assessing environmental conditions using e.g., pH and SOM gradients. Methods to quantify microbial dynamics at high temporal resolution include radioactive labelled isotopes to measure bacterial and fungal growth rates along with gas chromatograph to measure respiration rates.