EGU21-8525
https://doi.org/10.5194/egusphere-egu21-8525
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Investigating the chemical and spatial distribution of root carbon along the root-microbe-mineral pathway

Itamar Shabtai1, Johannes Lehmann1, and Taryn Bauerle2
Itamar Shabtai et al.
  • 1Cornell University, School of Integrative Plant Science , Soil and Crop Sciences, United States of America (is288@cornell.edu)
  • 2Cornell University, School of Integrative Plant Science , Horticulture, United States of America (is288@cornell.edu)

Plants allocate an estimated 11% of the C that they fixate as root exudates, a complex mixture of compounds that helps engineer the plant’s subterranean habitat. Root exudates stabilize soil aggregates, improve water retention, and shape rhizosphere microbial community composition. Exudates are also thought to contribute to the formation of stable mineral-associated organic matter. However, the function and fate of exudates along the soil profile may differ. We hypothesize that in topsoils with highly active microbial populations and mineral surfaces saturated with organic matter, root exudates may be rapidly intercepted and assimilated by soil microbes, and later adsorbed to surfaces as microbial necromass. But in subsoils with low microbial activity, exudates may directly adsorb on unsaturated mineral surfaces. The magnitude of these divergent pathways can shape the role of root exudates in rhizosphere C cycling. However, little is known about how adsorption vs. decomposition processes at the root-soil interface control i) the chemical transformations of C occurring along the root-microbe-mineral pathway, and ii) the spatial distribution and heterogeneity of exuded and processed exudate C. Our objective was to investigate the effect of microbial activity, and reactive mineral surfaces on the spatial distribution and functional group chemistry of root exudates at the root-microbe-mineral interface.

We packed samples from O, A, B, and C horizons collected from a grassland Mollisol, into individual microcosms, and installed a porous microdialysis membrane which served as an artificial root. Through this root, we injected either root exudates collected from maize plants, or dissolved organic carbon extracted from plant litter collected at the site. This comparison allowed us to study the dynamics of organic inputs entering the soil profile from the litter layer vs. directly from the roots. We destructively sampled the microcosms and obtained intact cross sections containing the artificial root and surrounding mineral/pore structures at different time points throughout the experiment. Here, we will present results obtained using synchrotron-radiation FTIR-microscopy of the temporal evolution, and spatial distribution of organic matter functional group chemistry in an artificial rhizosphere.

How to cite: Shabtai, I., Lehmann, J., and Bauerle, T.: Investigating the chemical and spatial distribution of root carbon along the root-microbe-mineral pathway, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8525, https://doi.org/10.5194/egusphere-egu21-8525, 2021.

This abstract will not be presented.