Graduation Year

2020

Document Type

Thesis

Degree

M.S.

Degree Name

Master of Science (M.S.)

Degree Granting Department

Marine Science

Major Professor

Brad Rosenheim, Ph.D.

Committee Member

Joseph M. Smoak, Ph.D.

Committee Member

Christopher Smith, Ph.D.

Keywords

activation energy distributions, blue carbon, Ramped PyrOx, root exudates, Ten Thousand Islands

Abstract

Mangrove forests have higher rates of carbon storage per unit area than any other coastal or terrestrial habitat, largely due to their significant soil stocks. More effort has been placed on quantifying mangrove soil carbon stock, the amount of carbon stored in the upper meter of mangrove soils, than identifying the processes governing in situ soil organic carbon (SOC) cycling and stabilization. An understanding of the mechanisms related to carbon transport and stability is necessary to constrain current wetland carbon stocks and to determine how sea level rise will impact future carbon stores. This study uses a variety of radiometric chronometers (210Pb, 137Cs, and 14C) paired with stable carbon isotopes, elemental analysis, downcore lignin profiles, and activation energy distributions to provide insight into mangrove SOC dynamics. Using these methods, I have identified a transport mechanism whereby young carbon is advected downward in pore waters and stabilized in the particulate form. I estimate over the last 120 years, the downward advection of carbon has led to the storage of 184 Tg of carbon in mangrove soils globally. In addition, I investigated the source of young carbon and the influence source played in long-term SOC stability. My data suggest young carbon is sourced from root exudates which are transported in pore waters and stabilized through microbially processing. Calculations of turnover time revealed differences in the timescale of carbon storage between sites that varied in tidal influence, with a longer turnover time at a site with inundated soils, but minimal tidal influence. This suggests inundation serves to enhance stability but is not the ultimate mechanism governing mangrove SOC stability.

Download

Share

COinS