Date of Award

Fall 2021

Project Type

Dissertation

Program or Major

Earth and Environmental Sciences

Degree Name

Doctor of Philosophy

First Advisor

A. Stuart Grandy

Second Advisor

Gordon B Bonan

Third Advisor

Serita D Frey

Abstract

Ecological processes drive terrestrial biogeochemistry, yet the incorporation of ecology into the Earth system models that we use to understand and project global change remains. My dissertation focuses on expediting the incorporation of ecology into Earth system models, first by laying out a roadmap from initial assessment of ecological insights to eventual ESM incorporation, and then by demonstrating this roadmap using the example of microbially- controlled carbon and nitrogen cycling in soil. The paradigm around SOM formation and loss has shifted in recent decades away from a focus on the chemically recalcitrant leftovers of litter decomposition and towards a paradigm with microbial residues and mineral interactions at its heart. The MIcrobial-MIneral Carbon Stabilization model (MIMICS) was developed as a way of exploring this new paradigm and examining the relationships between environmental drivers, litter chemistry, microbial physiology, and physical and chemical stabilization mechanisms for SOM. In the first chapter of my dissertation, I document a systematic approach to improve ecological process representation in Earth system models, highlighting multiple points along the way where ecological observations and modeling iteratively strengthen one another. In the second chapter, I develop and validate a new version of MIMICS with coupled N cycling using a large litter decomposition dataset. In the final chapter, I examine MIMICS-CN’s representation of the drivers of SOM C:N ratios using a landscape-scale data synthesis and model-data comparison. Together, these chapters describe and demonstrate the process of improving biogeochemical models along the path to ESMs by introducing new process representations of ecological concepts.

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