2020 Larson Allmaras Lecture
Emerging Issues in Soil and Water
Post-fire erosion: implications for lateral distribution and persistence of pyrogenic carbon
Speaker: Dr. Asmeret Asefaw Berhe
Professor of Soil Biogeochemistry, and Falasco Chair in Earth Sciences at the Department of Life and Environmental Sciences, University of California, Merced.
Other appointments: Past Chair of the US National Committee on Soil Science at the National Academies; Associate Editor of AGU’s Journal of Geophysical Research – Biogeosciences.
Education: Ph.D. in Biogeochemistry from the University of California (UC), Berkeley; M. Sc. in Resource Development (Political Ecology) from Michigan State University, and B. Sc. in Soil and Water Conservation from University of Asmara, Eritrea. Postdoc: University of California President’s Postdoctoral Fellow at UC Berkeley and UC Davis.
Research focus: biogeochemical cycling of essential elements (esp. carbon, nitrogen, and phosphorus) in the soil system.
Recognitions: recipient of several awards and honors, including the National Science Foundation’s CAREER award, the Geological Society of America’s Bromery Award, and is a member of the inaugural class of the US National Academies of Science, Engineering and Medicine's New Voices in Science, Engineering, and Medicine.
Fire, erosion, and soil carbon (C) dynamics overlap in space and time. Increased rates of erosion typically follow wildfires, and fire-altered or pyrogenic C (PyC, also referred to as black carbon) is redistributed vertically within soil profiles and laterally to lower landform positions along hillslopes, changing its C sequestration trajectory. However, we currently lack sufficient understanding on how and why the interaction of fire and erosional distribution of soil materials control persistence of bulk soil organic matter (SOM) and PyC in dynamic landscapes. In this talk, we present results from wildfires that occurred in the Sierra Nevada Mountains (USA) to demonstrate how the composition (based on stable isotope composition of 13C and 15N, and NMR analysis of OM composition) and magnitude of pyrogenic carbon redistributed by soil erosion varies considerably depending on fire severity and geomorphology of the landscape. Our findings also show that PyC is preferentially transported by erosion in high severity burn slopes, compared to areas affected by low and medium severity fires. Results that I will present in this talk are critical for better integration of biogeochemical and geomorphological approaches to derive improved representation of mechanisms that regulate SOM persistence in dynamic landscapes that routinely experience more than one perturbation.