Term of Award

Summer 2019

Degree Name

Master of Science in Biology (M.S.)

Document Type and Release Option

Thesis (restricted to Georgia Southern)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.


Department of Biology

Committee Chair

Kerrie Sendal

Committee Member 1

Risa Cohen

Committee Member 2

Checo Colon Gaud


Rising atmospheric levels of CO2 are causing global surface temperatures to climb and sea levels to rise. Coastal wetlands, the buffer environment between the land and the sea, are likely to be threatened by these changes, but the extent is unknown. To better understand the future of coastal environments, two dominant high marsh plant communities, one C3 and one C4, in Edgewater, Maryland were exposed to an experimental warming gradient (ambient, +1.7 °C, +3.4 °C, and +5.1 °C above ambient) using aboveground infrared lamps and belowground heating cables. Open-top chambers were installed within the C3 community to assess whether elevated CO2 (750 to 800ppm) or the combination of warming and elevated CO2 would affect coastal plants. Physiological measurements were taken throughout the 2018 field season (May – July) to determine how plants respond to these conditions. There was a decrease in stomatal conductance over the warming gradient, but the effects on leaf physiological traits were smaller than expected, likely because of the higher than average precipitation that fell in 2018 which allowed plants to maintain high rates of stomatal opening and thus reduce heat stress via evaporative cooling. When I tested the effect of CO2 addition and the warming extremes (ambient and +5.1 °C) on the C3 sedge, I found significant reductions in stomatal conductance in response to both factors. For both C3 and C4 species growing under ambient CO2, I also found a significant positive relationship between chlorophyll fluorescence and stomatal conductance, showing a correlation between declines in stomatal conductance with higher levels of thermal stress, likely due to reductions in evaporative heat loss. A companion laboratory study was set up to mimic the warming gradient in the C3 community using environmental growth chambers, which allowed me to take both morphological and physiological measurements of intact plants. In this experiment, stomatal conductance decreased with warming, and plants grown in the two warmest treatments had the highest proportion of senescence. Together, these results suggest that warming may be harmful to C3 plants by reducing stomatal conductance and increasing thermal stress.

Research Data and Supplementary Material