[Enviro-lunch] Enviro-lunch (4/11): Dr. Michael Rowley on Ca-stabilized soil organic carbon

Tue Apr 5 14:54:22 PDT 2022

[image: image.png]

Hello all,

Next Monday (4/11) Dr. Michael Rowley from Lawrence Berkeley National
Laboratory will present soil organic carbon stabilization by Ca. Please
join us between 12-1 pm (pacific) via zoom.

https://ucmerced.zoom.us/j/175736103

*Title:* Investigating the association of calcium and soil organic matter
in acidic soils at Point Reyes, CA using synchrotron-based and classical
characterisation techniques.

*Abstract*: Organo-mineral associations play an important role in both the
retention and accumulation of soil organic carbon (SOC). Recent studies
have demonstrated a strong link between calcium (Ca) and SOC in a range of
soil types. However, a current paradigm suggests that Ca-mediated
accumulation of SOC is predominantly constrained to soils with carbonates
(pH > 6).

Here we investigated the interaction between SOC and Ca in the acidic soils
of Point Reyes, California using a suite of characterisation methods. Both
SOC (0.6-4 %) and exchangeable Ca (5-8.3 cmolc./kg) content were high in
our samples and were closely correlated in multivariate analyses of our
classical characterisation data set. Linear combination fitting of the Ca
K-edge XANES data revealed that Ca was predominantly associated with
organic matter at our site. Additionally, scanning transmission X-ray
microscopy C K-edge /Ca L-edge near edge X-ray absorption fine structures
spectroscopy analysis showed that Ca had a strong spatial correlation with
C, presenting a higher spatial correlation than Fe. Aromatic and
double-bonded alkyl C dominated the C spectra associated with Ca, differing
from the C associated with Fe or Fe-Ca. These spectral features are
consistent with published spectra of C with a lignin-like nature and were
observed in our soil samples up to 70 cm depths.

It therefore seems that Ca-C association could be linked to the
preservation of lignin degradation products, even at depth in acidic
grassland soils with no carbonate . These observations may begin to
challenge the existing paradigm that Ca-SOC association is limited to soils
with a pH > 6.5.

[image: Mike.jpg]

*Bio: *Mike C. Rowley is a postdoctoral researcher at the Energy
Geosciences Division of Lawrence Berkeley National Laboratory (LBNL),
working in collaboration with the terrestrial ecosystem science scientific
focus area. Mike is a soil biogeochemist and has investigated different
ecosystems around the World. For his MSc. (Res.), Mike investigated the
oxalate-carbonate pathway in Haiti and Mexico, a process through which
oxalate-producing trees, oxalotrophic bacteria, and fungi sequester
atmospheric carbon as calcium carbonate in the soil. Mike then completed
his PhD. at the University of Lausanne, Switzerland. His thesis
investigated the mechanisms through which calcium contributes to soil
organic carbon accumulation at the Nant Valley, Switzerland. Now at LBNL,
Mike is furthering this research topic, investigating the processes through
which calcium complexes soil organic carbon in the soils of California
using synchrotron-based techniques.

Sincerely,

co-host: KJ Min & Manisha Dolui

Faculty coordinator: Asmeret Asefaw Berhe

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Spring 2022 Enviro-Lunch Schedule

*date*

*speaker*

*title*

*1/31*

Mariela Garcia Arrendondo
@ Umass-Amherst

Root-mediated weathering

*2/7*

Michael Philben
@ Hope College

Rethinking carbon and nitrogen isotope fractionation during soil organic
matter decomposition

*2/14*

Alyssa Griffin*
@ UC Davis

The role of coastal marine sediments in carbon cycling from local to global
scales

*2/21*

Presidents’ day

*2/28*

Katherine Heckman
@ USDA

Density fractionation and soil carbon stabilization

*3/7*

Bhavna Arora
@ LBNL

Reactive transport modeling

*3/14*

Darian Smercina
@ PNNL

Free N fixing under switchgrass (Linking microbial scale processes to
ecosystem function)

*3/21*

spring break

*3/28*

Meng Zhao
@ Stanford U

Plant-water relationship (evapotranspiration) modeling

*4/4*

Hannah Naughton
@ LBNL

Root vs. topographic generation of redox anomalies on a subalpine hillslope
and floodplain

*4/11*

Michael Rowley
@ LBNL

Ca-mediated soil organic carbon stabilization

*4/18*

Weiyu Li*
@ Stanford U

Data-driven hydraulic modeling

*4/25*

Daniel Zuleta

@ Smithsonian Institute

Tree mortality in tropical ecosystems

*5/2*

Genevieve Noyce
@ Smithsonian Institute

Greenhouse gas emissions from wetland with climate change
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