Anaerobic Decomposition in a Subarctic Swedish Peatland

• Other Authors: Cory, Alexandra (author), Chanton, Jeffrey P. (professor directing dissertation), Southerland, Sherry A., 1962- (university representative), Spencer, Robert G. M. (committee member), Landing, William M. (committee member), Florida State University (degree granting institution), College of Arts and Sciences (degree granting college), Department of Earth, Ocean, and Atmospheric Science (degree granting department)
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Florida State University 2022
• Subjects: Chemical oceanography; Browning; Subarctic
• Online Access: https://diginole.lib.fsu.edu/islandora/object/fsu%3A883226/datastream/TN/view/Anaerobic%20Decomposition%20in%20a%20Subarctic%20Swedish%20Peatland.jpg

On a global scale, peatlands contain 530 ± 160 Pg carbon, which is equivalent to >50% of the atmospheric pool. The fate of this enormous C reservoir could significantly impact the climate trajectory. Yet, two puzzling phenomena persist regarding C cycling dynamics in Sphagnum-rich peatlands ("bogs"): (1) their extraordinarily slow C mineralization rates; and (2) their high (relative to predicted) CO2:CH4 production ratios. This dissertation investigates three mechanisms thought to contribute to one or both phenomena. It also investigates the effects of temperature on C cycling dynamics within peat bogs and assesses the ability for incubation experiments to predict peatland climate responses. The first mechanism that we investigated involves interactions between phenolic compounds and enzymes. We hypothesized that these interactions would significantly limit C mineralization rates in bogs given that (1) these interactions cause enzyme immobilization and decreased C mineralization rates; and (2) bogs are postulated to contain an abundance of phenolics. The second mechanism that we investigated, "non-enzymatic browning", consists of a series of abiotic reactions involving a metabolite of Sphagnum spp. (galacturonic acid). Given its propensity to expel CO2 and limit bio-available nitrogen, we hypothesized that non-enzymatic browning would elevate CO2:CH4 production ratios and suppress overall decomposition rates in peat bogs. The third mechanism that we investigated, "organic matter hydrogenation", involves the addition of H2 (a biproduct of fermentation) to organic matter. As organic matter hydrogenation has a higher energy yield than methanogenesis (which also uses H2), we hypothesized that this mechanism would elevate bog CO2:CH4 production ratios (via methane inhibition). Using a combination of incubation experiments and field measurements, we determined that the extraordinarily slow C mineralization rates associated with bogs are influenced by both phenolic-enzyme interactions (mechanism 1)—which inhibited ...