[Enviro-lunch] Rebecca Abney Ph.D. Defense - May 24 10AM

[Asmeret Asefaw Berhe]

Hello all,

Please join us for Ph.D. defense of Rebecca Abney.


*The role of erosion in soil organic matter and pyrogenic carbon dynamics
in fire-prone temperate forests*


Rebecca Abney

Environmental Systems

Adviser: Asmeret Asefaw Berhe



Date: 5/24/17 | Time: 10 AM | Location: SE2 – 302



*Abstract*

 Wildfire and erosion are major perturbations to the carbon cycle in
eroding Sierra Nevada temperate forest landscapes. Pyrogenic carbon (PyC)
is formed due to incomplete combustion during fires, and is an important
component of the soil carbon sink due its relatively longer turnover times
in soil and susceptibility to erosion forces. Erosion of PyC and other soil
organic matter fractions was monitored after two wildfires: the Gondola
Fire, South Lake Tahoe and the Rim Fire, Yosemite National Park.
Significant and preferential erosion of PyC was found after the fires, in
addition to leaching down into the soil profile. The preferential erosion
of PyC, and overall quality of the soil and eroded sediments were
controlled by burn severity. To assess the fate of PyC in eroding and
depositional landform positions, chars formed at different temperatures
were incubated in the same soil collected from different landform
positions. Both charring temperature and landform position played
significant roles in controlling soil respiration, with the lower charring
temperatures and the soil from the depositional landform position having
much higher respiration than higher temperature chars and the soil from the
eroding landform position. The post-fire erosional transport of PyC can act
as a major control on its long-term fate in soil. By modeling the
difference between including eroding and depositional landform positions in
PyC decay models, this can introduce error in measured turnover times of up
to 150 years. Including erosion as a mechanism for loss and gain of PyC in
eroding and depositional landform positions, respectively, is critical for
accurate accounting of PyC within the soil cycle. Understanding the
controls of erosion of PyC allows land managers to mitigate erosional loss
to enhance soil carbon storage.



*Biography*

 Rebecca graduated with a Joint Honours Bachelor’s of Science in
Environmental Biology and Physical Geography from St. Andrews in Scottland.
While studying there, she worked on research projects on the impacts of
land use and land use change on soil carbon cycling through a transect in
the Peruvian Andes. Her current research focuses on the interactive roles
that fire and erosion play as controls on soil carbon cycling. Her projects
include working on the Gondola Fire, near South Lake Tahoe and the Rim Fire
in Yosemite National Park. While studying at UC Merced, Rebecca has given
talks on her work at the American Geophysical Union annual meeting in both
2015 and 2016, in addition to a Critical Zone Observatory conference.

Cheers,
Asmeret

---------------
Asmeret Asefaw Berhe
Associate Professor, Soil Biogeochemistry

Life and Environmental Sciences
University of California, Merced

Office phone: (209) 228-4712
E-mail: AABerhe at UCMerced.edu
Web: http://www.aaberhe.com
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