1,2,4,1- 1Centre for Microbiology and Environmental Systems Science, Division of Terrestrial Ecosystem Research, University of Vienna, Vienna, Austria (crottensteiner93@gmail.com)
- 2Vienna Doctoral School of Microbiology and Environmental Science, University of Vienna, Vienna, Austria
- 3Centre for Microbiology and Environmental Systems Science, Division of Microbial Ecology, University of Vienna, Vienna, Austria
- 4Department of Ecology, University of Innsbruck, Innsbruck, Austria
Global warming increases the probability and frequency of droughts, with major consequences for soil carbon cycling. Soil microorganisms are particularly sensitive to drought because decreasing soil water content imposes osmotic stress and restricts the diffusion of substrates, enzymes, and metabolites. Previous studies have shown that drought reduced bacterial growth rates by more than half, whereas fungal and actinobacterial growth was comparatively resistant. However, in a future climate where droughts are projected to become more frequent, soils will be exposed to repeated drought events, and it remains unclear how drought history shapes microbial growth and carbon allocation during subsequent drought.
Here, we investigate how recurrent summer drought affects microbial growth, respiration, and storage compound synthesis in a unique long-term field experiment in an alpine grassland. Plots (n=4) have been exposed to 1, 3, 7, or 17 consecutive years of summer drought using rain-out shelters, with ambient plots as controls. We applied 2H-vapor-FAME-SIP (deuterium water-vapor stable isotope probing) to quantify microbial growth based on PLFAs (phospholipid fatty acids) and microbial carbon storage based on NLFA (neutral lipid fatty acid) and PHB (poly-3-hydroxybutyrate) production. Microbial respiration was determined by infrared gas analysis and microbial biomass by the chloroform-fumigation-extraction method.
Our results show that microbial respiration progressively declines with drought history. At peak drought, respiration was reduced by 44% after a single summer drought. This reduction intensified to 62%, 66%, and 75% after 3, 7, and 17 years of recurrent summer drought, respectively. This pattern indicates a strong drought legacy effect, consistent with the formation of ecological memory which increasingly constrains microbial activity. We will also present results from microbial growth and storage compound synthesis measurements and discuss how microbial carbon allocation patterns change with drought history.
By linking drought history to microbial growth, respiration, and storage compound synthesis, this study reveals how repeated drought alters carbon allocation of soil bacteria and fungi, with consequences for soil carbon persistence and carbon–climate feedbacks under global change.
This study is part of FWF COE7 “Microbiomes drive planetary health”.
How to cite: Rottensteiner, C., Waschulin, V., Woebken, D., Bahn, M., and Richter, A.: Recurrent drought imprints ecological memory on microbial carbon allocation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17390, https://doi.org/10.5194/egusphere-egu26-17390, 2026.
