Sarah K. Tash

Date of Award

2024

Type

Thesis

Major

Earth and Space Science - Environmental Science Track

Degree Type

Master of Science

Department

Earth & Space Science

First Advisor

Dr. Stacey Blersch

Second Advisor

Dr. Troy Keller

Third Advisor

Dr. Michael Dentzau and Dr. Clifton Ruehl

Abstract

Emergent macrophytes in river systems occupy a narrow habitat for optimal survival. Each plant species adapts to a set of conditions that meets the physiological requirements to grow and reproduce. The influence of hydraulic characteristics on plant morphology is significant within fluvial systems. Macrophytes must be able to withstand swift flowing water and changes in water surface levels in order to compete with other plant species for limited habitat availability. In addition, emergent macrophytes require water levels to be low enough to allow the reproductive portion of plants to remain above water during certain times of the year. Hymenocallis coronaria is an emergent macrophyte found in fragmented and limited populations in Southern rivers. Populations are located along the fall line of the southern states of Alabama, Georgia, and South Carolina. In these states, the geomorphology of riverbeds provides a shallow and swift-moving environment. Anthropogenic alterations along river waterways (e.g., dams) have fundamentally altered the seasonal variation in water flow and sediment transport processes, resulting in declines in population size in a species with a small distribution in ideal conditions. Limited research has been performed on defining the ecoyhydraulic requirements of H. coronaria despite declining populations. Populations along the Flint River in Georgia are an archetypal population, surviving on a river where no artificial flow alterations occur for over 227 miles. Seasonal variation in flow occurs naturally, strongly influenced by precipitation and ground water interflow. This study mapped the elevation points of areas with both present and absent H. coronaria locations, then calculated the relative depth at each point using USGS water surface level data from a nearby gage at Thomaston, Georgia. I found a significant correlation between relative depth of the river and the probability of H. coronaria occurrence. As relative depth increases the probability of the presence of H. coronaria decreases. The population in v Hightower Shoals is found within a relative depth range of 0-1.8m, which could help establish parameters for bulb transplantation in areas where restoration efforts are being conducted. These results can also aid restoration efforts by identifying riverbed conditions that are most desirable and provide recommendations for depth of bulb transplantation for restoration efforts. Determining water surface level fluctuations that are tolerated by H. coronaria will aid in the study of future populations of this endangered plant.

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