Response of Baldcypress (Taxodium distichum) at Different Life Stages to Flooding and Salinity

ECU Author/Contributor (non-ECU co-authors, if there are any, appear on document)

Amanda S. Powell (Creator)

Institution

East Carolina University (ECU )

Web Site: http://www.ecu.edu/lib/

Abstract: Baldcypress are dominant trees in forested coastal wetlands. As sea levels rise, it is important to increase our understanding of how increased salinity and flooding will affect forested coastal wetlands. This study combined field observations and a greenhouse experiment to examine the effects of salinity and flooding on baldcypress growth at different life stages: seedlings, young trees, and mature trees. 1) I conducted a greenhouse experiment with flooded and drought conditions and different salinity treatments looking at the growth of seedlings. 2) To assess the response of young trees I examined the diameter at breast height (DBH) and height of >9 year old trees that were planted in a restored wetland across salinity and flooding gradients. 3) I also conducted a regional survey of adult baldcypress growth using increment tree ring cores along a salinity gradient in the Albemarle Sound, North Carolina. In the greenhouse experiment, I found that drought, saltwater, and sulfate had significant negative effects on height over an exposure period of 26 weeks, while drought and saltwater had a significant negative effect on root collar growth. Overall, I found that the presence of saltwater decreased height of baldcypress seedlings by 15% and decreased the diameter at root collar by 21% compared to the control, regardless of hydrology. Seedlings watered with saltwater showed a decrease in biomass of leaves (55%), stems (50%), and roots (71%) compared to seedlings in the control. For the young trees in a wetland restoration site, DBH and tree height were not significantly correlated with water depth. However, DBH and height were negatively correlated with chloride concentrations in soil solution. Height was also negatively correlated with ammonium and total dissolved nitrogen concentration in soil solution, which are known to increase due to increases with salinity. The increment tree ring cores showed that the average tree age for five sites ranged between 94 to 118 years old. I found a trend towards declining growth of adult trees with increasing salinity, but the lack of long-term environmental data and multiple possible stressors on adults trees (droughts, hurricanes, and fires to name a few) make it difficult to isolate the effects of salinity and flooding on adults tree growth. My results suggest that baldcypress trees in this region of North Carolina are more sensitive to increased salinity than to increase flooding. I found lines of evidence for decreased growth of baldcypress trees in response to salinity at the seedling, young adult, and adult stage. I did not find such support for the effects of flooding on growth at the young adult and adult stage. My results suggest that increases in saltwater incursion and sea level rise could lead to decreased growth and/or death of baldcypress trees, which are foundational species in forested coastal wetlands.

Additional Information

Publication

Thesis

Language: English

Date: 2023

Subjects

Ecology;Saltwater incursion;Wetlands;Biology, Ecology

Email this document to