2024 Abstracts

The Role of Redox and Wildfire in Shaping the Fate of Soil Carbon and Biogeochemical Cycling


Kelsey Crutchfield-Peters1* (klcp28@lbl.gov), Jasquelin Peña1,2, Peter Nico1, Elaine Pegoraro1, Cristina Castanha1, Margaret S. Torn1


1Lawrence Berkeley National Laboratory, Berkeley, CA; 2University California–Davis, CA



Soils store more carbon globally than the biosphere and atmosphere combined, primarily as soil organic matter (SOM). The Belowground Biogeochemistry Science Focus Area (SFA) is tasked with using manipulation experiments to explore how soil carbon stocks will respond to a changing climate, and in particular to warming. Here researchers lay out two new areas of investigation for the SFA that will improve the understanding of the soil carbon cycle and how soil carbon stocks will respond to future climate conditions.

The majority of reactions that shape SOM decomposability involve electron transfer (or redox) reactions. These reactions are largely driven by microbial metabolisms, including aerobic and anaerobic respiration. However, redox status and dynamics in upland soils are understudied. Additionally, organic matter associations with redox-active minerals and metals also influence SOM decomposition, but the detailed behavior of those associations remains uncertain. To that end, researchers investigate dynamic redox conditions and SOM characteristics throughout the soil profile in a dynamically saturated coastal grassland in Northern California. Researchers report initial results from arrays of custom-made redox electrodes deployed in shallow, intermediate, and deep soil horizons alongside measurements of soil pore water and groundwater chemistry.

In parallel, researchers are launching a new investigation of soil biogeochemistry, including SOM cycling, and plant community recovery after wildfire. Here the team presents the design and initial testing of mobile warming units. These units will be deployed after fire in both a grassland ecosystem and mid-elevation forest during Phase 3 SFA. Once researchers establish baselines in temperature and moisture for control and warmed plots, they will investigate: 1) how SOM and metal cycling are affected by fire and warming, given the loss of vegetation, input of fire-derived mineral ash and pyrogenic carbon, and changes in soil moisture; and 2) how soil warming impacts the recovery of native and planted vegetation in fire-impacted ecosystems.