Graduate Studies

 

First Advisor

Jessica R. Corman

Degree Name

Doctor of Philosophy (Ph.D.)

Committee Members

David Wedin, Keeley MacNeill, Sherilyn Fritz, Steven Thomas

Department

Natural Resource Sciences (Applied Ecology)

Date of this Version

7-2025

Document Type

Dissertation

Citation

A dissertation presented to the Graduate College of the University of Nebraska in partial fulfillment of requirements for the degree of Doctor of Philosophy

Major: Natural Resource Sciences (Specialization: Applied Ecology)

Under the supervision of Professor Jessica R. Corman

Lincoln, Nebraska, July 2025

Comments

Copyright 2025, Daniel Gschwentner. Used by permission

Abstract

The Nebraska Sandhills contain thousands of shallow, groundwater-fed lakes. These lakes are extremely sensitive to environmental and climatic changes due to their isolated hydrological setting and small volume. Building on previous work on the hydrology, geochemistry and long-term climate response of Sandhill lakes, my research considers how ecosystem processes such as primary production, nutrient limitation and water quality respond to short-term environmental and climatic change. In my first data chapter, I highlight that Sandhill lakes are nitrogen (N) but not phosphorus (P) limited and that N:P ratios are poor predictors of nutrient limitation status in Sandhill lakes. In my second chapter, I leverage an extensive remotely sensed lake color dataset to evaluate the utility of remote sensing products as indicators of lake water quality, and I determine how lake water quality has changed over four decades in Sandhill lakes. In my third and fourth chapters I demonstrate that although wildfire ash can supply P to lakes, the effects of wildfire ash as a resource pulse to lake ecosystems are mediated by lake trophic state and nutrient limitation status. In my final data chapter, I use high resolution satellite images to reconstruct lake ice dynamics for Sandhill lakes and determine drivers of lake ice duration. My work contributes to our understanding of lake ecosystem processes in an understudied lake district and provides insights into how Sandhill lakes respond to environmental and climatic changes on short timescales.

Advisor: Jessica R. Corman

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