Defense Date

2022

Document Type

Thesis

Degree Name

Master of Science

Department

Biology

First Advisor

Julie Zinnert

Second Advisor

Nicholas Cohn

Third Advisor

Christopher Hein

Fourth Advisor

Donald Young

Fifth Advisor

Rima Franklin

Abstract

Under future climate change and sea level rise scenarios, Natural and Nature-Based Features (e.g., dunes) that protect coastal habitat and infrastructure will be exposed to increased wave energy and storm surge. Understanding how these forces will impact coastal dunes is necessary for their continued use as protective features. Coastal dunes develop through feedback between vegetation and sediment deposition, a process complicated by species-specific growth rates and responses to burial. Wave flume studies have tested the effects of dune vegetation on erosion and found multiple plant organs across several functional types to be important for resisting erosion. Although dune building and erosion are known to be mediated by dune vegetation, the amount and distribution of plant belowground biomass within a dune represents a knowledge gap in coastal ecology and geomorphology. Our objectives were to quantify the belowground structure (e.g., plant roots, belowground stems and rhizomes) and aboveground composition of dunes across a range of management styles. To do so, we utilized a geological sampling method (e.g., vibracoring) to sample belowground biomass at depths greater than those represented in the literature across the dune profile at several sites representing multiple management histories. Our study occurred on foredunes of the Outer Banks, North Carolina, a net-erosional barrier island chain with varying levels of human development and management. vii Sites ranged from an unmanaged, undeveloped dune backed by shrub thicket to a dune constructed and planted with Ammophila breviligulata following a beach nourishment in 2017. Living belowground biomass was highly variable across sites and did not exhibit differences between managed and unmanaged dunes or among depths within 90 cm of the sediment surface. Elevation was a significant predictor of living belowground biomass, fine root surface area, soil organic matter content, living cover and species richness. Plant community differences between management histories and among dune positions and sites occurred with larger sampling frequency (e.g. whole dune multiple transect survey) but were not present when considering plant community at coring plots only. The dune face at managed sites was dominated by Ammophila breviligulata, likely as a result of planting efforts by local managers. We also found a strong relationship between total living cover and living belowground biomass at coring plots, a finding that may prove useful in future estimates of living belowground biomass. These results underscore the importance of geomorphology on dune plant communities, with effects on species that may influence erosion resistance. Our findings will be incorporated into future numerical models used to predict dune response to sea-level rise and storms in order to better understand and manage dunes as natural protective features with climate change.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

8-11-2022

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