Date of Award

2026-05-01

Degree Name

Doctor of Philosophy

Department

Environmental Sciences

Advisor(s)

Anthony J. Darrouzet-Nardi

Abstract

Earth's Critical Zone (CZ) plays a key role in sustaining life through carbon, water, and nutrient cycling from the top of the canopy to the groundwater. A key feature of critical zone research is the integration of multiple interdisciplinary techniques. An emerging set of techniques that can add to this approach is the field of metabolomics, the quantification and study of comprehensive metabolite profiles. In this dissertation, I apply metabolomics to address knowledge gaps in dryland critical zone ecosystems, specifically how soil metabolite dynamics influence biogeochemical processes, and with a particular emphasis on phosphorus (P) cycling in the Chihuahuan Desert. I first evaluate the threshold concentration range of organic acids required to mobilize P in a laboratory experiment using field-collected soils from different landforms and vegetation microhabitats, and measure in situ organic acid concentrations to determine whether they reach levels sufficient to release P (Chapter 2). Using these same samples, I then characterize the broader soil metabolite landscape to identify metabolites associated with nutrient limitation, stress responses, and ecological interactions among plants, microbes, and biocrusts (Chapter 3). Finally, I examine soil metabolite responses to experimental P addition in a native grassland to evaluate how metabolite composition shifts under altered nutrient availability (Chapter 4). Together, this dissertation demonstrates how soil metabolite dynamics reveal the biochemical mechanisms linking microsite processes to broader dryland biogeochemistry, extending insights from regional patterns in the Chihuahuan Desert to dryland ecosystems globally and advancing our understanding of biogeochemical processes vital for sustaining Earth's biophysical (CZ) systems and functions.

Language

en

Provenance

Received from ProQuest

File Size

163 p.

File Format

application/pdf

Rights Holder

Kalpana Kukreja

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