December 16, 2022 by Teamrat A Ghezzehei

Hooding of Toshi & Manisha

We are thrilled to announce the graduation of two exceptional scholars, Dr. Toshiyuki Bandai and Dr. Manisha Dolui, who have successfully obtained their PhD degrees in Environmental Systems. This remarkable accomplishment marks a significant milestone in their academic journeys, representing years of dedication, hard work, and intellectual growth.

Dr. Toshiyuki Bandai’s dissertation, titled “Inverse modeling of soil moisture dynamics: Estimation of soil hydraulic properties and surface water flux,” explores the vital role of soil moisture in various applications. His research focuses on analyzing soil moisture data using inverse modeling, employing the Richardson-Richards equation (RRE) and innovative techniques from applied mathematics.

Within his dissertation, Dr. Bandai employs physics-informed neural networks (PINNs) to approximate the RRE’s solutions for layered soils. He demonstrates the superior performance of the Peters-Durner-Iden (PDI) model in capturing soil moisture dynamics, particularly in dry conditions. Furthermore, he compares the adjoint method with PINNs for estimating surface water flux from soil moisture measurements, highlighting the robustness of the adjoint method in data-limited scenarios. On the other hand, Dr. Manisha Dolui’s remarkable achievements are equally commendable. Her dissertation, titled “Exploring Soil Erosion Processes in Vulnerable Landscapes,” focuses on understanding the processes and factors influencing soil erosion in environmentally sensitive areas. Dr. Dolui’s research contributes valuable insights into mitigating soil erosion and its implications for sustainable land management practices.

Dr. Manisha Dolui’s dissertation, titled “Variability, Stability, and Vulnerability of Buried Soil Organic Carbon: Differences Along Depositional and Erosional Transects,” explores the dynamics of buried soil organic matter (SOM) in paleosols. Her research investigates the physical and chemical composition of soils along depositional and erosional transects in the Brady paleosol of Nebraska, USA. Through elemental and isotopic analysis, radiocarbon dating, and spectroscopic techniques, Dr. Dolui reveals insights into the distribution, stabilization, and vulnerability of SOM in deeply buried soil layers.

Dr. Dolui’s study further examines the effects of moisture addition on the vulnerability of SOM. The findings demonstrate that changes in soil moisture status can play a crucial role in destabilizing previously protected ancient carbon stocks. This research emphasizes the need to understand the potential release of greenhouse gases due to increased precipitation and accelerated erosion. Dr. Dolui was advised by Prof. Asmeret Asefaw Berhe until May 2022, when she was appointed Director of Office of Sciemce at US Department of Energy.

Congratulations to Dr. Toshiyuki Bandai and Dr. Manisha Dolui on their well-deserved PhD degrees. Their exceptional research contributions broaden our understanding of soil moisture dynamics and the dynamics of buried soil organic carbon, paving the way for further advancements in these fields. We wish them both as they embark on postdoctoral positions at Lawrence Berkeley National Lab and UC Merced, respectively.