Upland soils, e.g. a typical farm soil, are considered completely oxic and thus unlimited with respect to microbial carbon oxidation to the greenhouse gas, carbon dioxide. However, upland soils contain up to 85% anaerobic pore space that hinders respiration and potentially exacerbates the release of potent greenhouse gases like methane. Difficulties measuring the spatial and temporal extent of these anaerobic soil spaces, much less their impact on carbon cycling, leads to poor estimations of soil carbon storage and greenhouse gas emissions. This project aims to improve understanding of how nominally oxic soils develop anaerobic microsites and to assess their influence on soil carbon fluxes and transformations relevant to long-term carbon storage. Water-saturated conditions and organic inputs are known to deplete soil oxygen, but the role of roots in forming soil redox microheterogeneity has not yet been tested. Plant roots may enhance local anaerobic microsite prevalence through the production of exudates that fuel microbial respiration and through the formation of larger aggregates capable of hosting anaerobic interiors. The intern will develop a workflow based on laboratory incubations of soils coupled with greenhouse gas and soil carbon measurements to test for the presence of root-associated anaerobic sites and their influence on carbon cycling in hydrologically distinct (i.e. wet vs. dry) soils.
A meadow hillslope field site in the East River valley outside of Crested Butte, CO was chosen to represent a gradient of dry hilltop to wet toeslope elevations and soils were collected from beneath bunchgrasses and from unvegetated soil as a control. The intern will develop a set of incubation treatments, for example aerobic/anaerobic and aggregated/disaggregated soils, to test the hypothesis that plant roots enhance anaerobic microsites through their influence on soil aggregation and that carbon cycling in anaerobic microsites is distinct from that of bulk soil. The incubations will be coupled with collection of volatile organic compounds indicative of microbial metabolisms to be measured on a thermal decomposition gas chromatograph/mass spectrometer and greenhouse gases to be measured by gas chromatography. Soil carbon chemistry and microbial community composition will be examined to corroborate the presence and unique chemistry of anaerobic microsites. The student may have an opportunity to present their findings at a national meeting in 2022 and to co-author a scientific peer-reviewed paper.
The student will help develop an experimental setup for soil incubations in collaboration with the mentor, independently run the incubations, and assist in the collection and interpretation of associated soil carbon, gas and microbial data.
Introductory inorganic and organic chemistry
An interest in biogeochemistry, soil science, microbiology, or the carbon cycle
Commitment to weekly on-site lab work at LBNL