The δ13C value of foliage respiration has been considered a constant in the past
and modeling efforts have assumed that the δ13C value of foliage respiration is constant
and is directly related to substrate without any fractionation. Consecutive δ13C
measurements of foliage dark-respired CO2 (δ13Cr) for slash pine trees (Pinus elliottii)
over several diel cycles were used to test the hypothesis that significant variation in
δ13Cr would be observed. δ13Cr values collected in daylight from all time series showed
mid- day 13C enrichment (5 – 10‰) relative to bulk biomass, but values become more 13C
depleted following shading and at night and approach bulk-biomass δ13C values by dawn.
Assimilation model results suggest that respiration during daylight has the potential to
significantly affect ∆13C by as much as 1.6‰, but night dark respiration has little
impact on 24-hour integrated ∆13C (0.1‰). We also sampled methane and CO2 from collapse
scar bogs (transient permafrost degradation features in permafrost peatlands) to test
the hypotheses that microbial respiration and methane production are stimulated by
permafrost degradation and collapse and that the fen-like vegetation (i.e. Carex andxi
Eriophorum) found in collapse scar bogs near the collapsing edge stimulates acetate
fermentation. Our results show that collapse scar bogs have an evolution of spatial
variation in methanogenic pathways that is related to surface vegetation cover type. We
also demonstrate that changes in stable-isotope fractionation caused by shifts from
acetate fermentation and CO2 reduction occur over long time scales (> annual) and are
dependent on changes in wetland morphology and surface vegetation cover. We also used
radiocarbon as a tracer to test the hypothesis that melting permafrost surrounding the
collapse scar bog provides nutrients to the bog-moat location, stimulating the
production of radiocarbon-depleted methane. Our results show that the radiocarbon
content of methane and DIC at these sites is highly variable and may depend on
groundwater input, surface vegetation, and morphological factors associated with the
melting permafrost plateau. We conclude that the younger, more labile, carbon
stimulating acetate fermentation at one of the sites is supplied by the fen-like surface
vegetation, while the older, more recalcitrant, carbon stimulating CO2 reduction at the
other site may be supplied by melting permafrost plateau.. / A Dissertation submitted to the Department of Oceanography in partial fulfillment
of the requirements for the degree of Doctor of Philosophy. / Degree Awarded: Fall Semester, 2005. / Date of Defense: September 16, 2005. / Carbon Stable Isotopes Fractionation Respiration / Includes bibliographical references. / Jeffrey P. Chanton, Professor Directing Dissertation; Yang Wang, Outside Committee Member; Joel E. Kostka, Committee Member; Behzad Mortazavi, Committee Member; William C. Burnett, Committee Member; John W. Winchester, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_168569 |
| Contributors | Prater, James L. (authoraut), Chanton, Jeffrey P. (professor directing dissertation), Wang, Yang (outside committee member), Kostka, Joel E. (committee member), Mortazavi, Behzad (committee member), Burnett, William C. (committee member), Winchester, John W. (committee member), Department of Earth, Ocean and Atmospheric Sciences (degree granting department), Florida State University (degree granting institution) |
| Publisher | Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text |
| Format | 1 online resource, computer, application/pdf |
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