Dying - how and where? Microbial necromass quality and process rates in the soil pore space

Microbial necromass - dead biomass - constitutes an important part of soil organic matter.

The factors governing the turnover and stabilization of microbial necromass are not well understood but can strongly feedback to atmospheric CO2 levels.

It is hypothesized that the spatial location and the mode of death are important predictors for its stability, but this has hitherto been difficult to study.

We have recently developed microfluidic soil models that allow us to employ microspatial structures as experimental factors.

We now want to utilize those to study how death pathways – where and how the microbes died - influence microbial necromass stability.

We will establish necromass in-situ by growing microbes in systematically designed microspaces and label them isotopically.

We will re-inoculate the spaces with fresh microbes and measure the speed of isotopic depletion and chemical changes of the first generation necromass via microspectroscopy as a function of their spatial location.

We will further expose microbial communities to different death causes (predation, physical and chemical stress) to study their effect on spatial necromass distribution, organo-mineral interactions and chemical quality. Thirdly, we will study how turbation, a disturbance in the microspatial settings, influences necromass stability.

An increased understanding of the formation of stable organic matter in soils is crucial for improved soil carbon models and recommendations on land use practices.