Webinaire Axe 2 : Andreas Richter

Head of the Centre for Microbiology and Environmental Systems Science
Head of the Division of Terrestrial Ecosystem Research

Centre for Microbiology and Environmental Systems Science, University of Vienna

Microbial activity and biomass drive soil carbon and nitrogen cycling

 Growth is the foundation of all life, essentially driving the dynamics of ecosystems. Microorganisms tightly regulate their growth to optimize survival in ever-changing environments. The growth of heterotrophic microorganisms involves deconstructing soil organic matter and assimilating organic carbon and nitrogen into biomass, and, upon death, their remains become part of soil organic matter again. Without microbial growth, organic matter turnover would cease, effectively halting the fluxes of matter and energy. Soil biogeochemistry is thus fundamentally driven by the growth and activity of microbial communities.

 In this talk, I will explore the processes that make up microbial growth and propose a theoretical framework for understanding growth dynamics in soil. I will focus on different levels of resolution (from communities to individual populations) and examine different growth components, including cell division and the synthesis of storage compounds. I will also demonstrate how essential growth is for ecosystem-scale nitrogen dynamics. I will argue that to advance our understanding of soil functioning, we must move beyond traditional metrics like carbon use efficiency, microbial respiration, and nutrient mineralization rates. Instead, we should focus on microbial growth as the fundamental unit linking soil microbiomes to matter fluxes.

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