The CO2 flux of two peatlands in northern Alberta was examind during the 2004 growing season using eddy covariance measurements of net ecosystem exchange (NEE), chamber measurements of total ecosystem respiration, and empirical models driven by meteorological inputs. The two ecosystems, a poor fen and an extreme-rich fen, differed significantly in plant species composition, leaf area index, aboveground biomass and surface water chemistry. The mean diurnal pattern of NEE at the peak of the season was similar between the sites, however, the extreme-rich fen had a higher photosynthetic and respiratory capacity than the poor fen. Over the 6 month study, the poor fen was shown to accumulate between 2 to 3 times more carbon than the extreme-rich fen despite having a lower photosynthetic capacity. The evergreen nature of the poor fen site allowed for a longer season of net CO2 uptake than the deciduous species that dominated the extreme-rich fen. / xii, 126 leaves : ill. (some col.) ; 29 cm.

Thesis: Ph. D., Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 213-240). / Life is ubiquitous in the environment and an important mediator of Earth's carbon cycle, but quantifying the contribution of microbial biomass and its metabolic fluxes is difficult, especially in spatially and temporally-remote environments. Microbes leave behind an often scarce, unidentifiable, or nonspecific record on geologic timescales. This thesis develops and employs novel geochemical and genetic approaches to illuminate diagnostic signals of microbial metabolisms. Field studies, laboratory cultures, and computational models explain how methanogens produce unique nonequilibrium methane clumped isotopologue (1 3CH3D ) signals that do not correspond to growth temperature. Instead, [Delta]13CH3D values may be driven by enzymatic reactions common to all methanogens, the C-H bond inherited from substrate precursors including acetate and methanol, isotope exchange, or environmental processes such as methane oxidation. The phylogenetic relationship between substrate-specific methyl-corrinoid proteins provides insight into the evolutionary history of methylotrophic methanogenesis. The distribution of corrinoid proteins in methanogens and related bacteria suggests that these substrate-specific proteins evolved via a complex history of horizontal gene transfer (HGT), gene duplication, and loss. Furthermore, this work identifies a previously unrecognized HGT involving chitinases (ChiC/D) distributed between fungi and bacteria (~650 Ma). This HGT is used to tether fossil-calibrated ages from within fungi to bacterial lineages. Molecular clock analyses show that multiple clades of bacteria likely acquired chitinase homologs via HGT during the late Neoproterozoic into the early Paleozoic. These results also show that, following these HGT events, recipient terrestrial bacterial clades diversified ~400-500 Ma, consistent with established timescales of arthropod and plant terrestrialization. Divergence time estimates for bacterial lineages are broadly consistent with the dispersal of chitinase genes throughout the microbial world in direct response to the evolution and expansion of detrital-chitin producing groups including arthropods. These chitinases may aid in dating microbial lineages over geologic time and provide insight into an ecological shift from marine to terrestrial systems in the Proterozoic and Phanerozoic eons. Taken together, this thesis may be used to improve assessments of microbial activity in remote environments, and to enhance our understanding of the evolution of Earth's carbon cycle. / by Danielle S. Gruen / Ph. D.

Accurate estimation of Net Primary Productivity (NPP), which is a key component of the terrestrial carbon cycle, is very important in studies of global climate. Ecosystem models have been used for NPP estimates. Determining how much each source of uncertainty contributes to modeled NPP is veiy important before ecosystem models can be used with confidence over larger areas and time periods. This research has systematically evaluated the boreal ecosystem productivity simulator (BEPS) carbon model in mountainous terrain, Kananaskis, Alberta. After parameterization of the model, sensitivity analysis was conducted as a controlled series of experiments involving sensitivity simulations with BEPS by changing a model input value in separate model runs. The results showed that NPP was sensitive to most model inputs measured in the study area, but that the most important input variables for BEPS were LAI and forest species. In addition, the NPP uncertainty resulting from topographic influence was approximately 3.5 %, which is equivalent to 140 kg C ha"1 yr"1. This suggested that topographic correction for the model inputs was also important for accurate NPP estimation. Using the topographically corrected data, the carbon dynamics were simulated, and average annual NPP production by forests in Kananaskis was estimated at 4.01 T ha"1 in 2003. / xix, 117 leaves : col. ill. ; 29 cm.

Indiana University-Purdue University Indianapolis (IUPUI) / Long term no-till (NT) farming can improve the CH4 oxidation capacity of agricultural lands through creation of a favorable soil environment for methanotrophs and diffusive gas transport. However, limited data is available to evaluate the merit of that contention. Although the potential for biological CH4 oxidation may exist in NT soils, restricted diffusion could limit expression of that potential in fine-textured soils. A study was conducted to assess the CH4 oxidation potential and gaseous diffusivity of soils under plow till (PT) and NT for > 50 years. Intact cores and composite soils samples (0-10 and 10-20 cm) were collected from NT and PT plots located at a well-drained site (Wooster silt loam) and at a poorly-drained (Crosby silt loam) site in Ohio. Adjacent deciduous forest soils were also sampled to determine maximum rate expected in undisturbed soils in the region. Regardless of study sites and soil depth, CH4 oxidation rate (measured at near ambient CH4) and oxidation potential (Vmax, measured at elevated CH4) were 3-4 and 1.5 times higher in NT than in PT soils, respectively. Activity in the NT soils approached (66-80 %) that in the forest soils. Half saturation constants (Km) and threshold for CH4 oxidation (Th) were lower in NT (Km: 100.5 µL CH4 L-1; Th: 0.5 µL CH4 L-1) than in PT soils (Km: 134 µL CH4 L-1; Th: 2.8 µL CH4 L-1) suggesting a greater affinity of long-term NT soils for CH4, and a possible shift in methanotrophic community composition. CH4 oxidation rates were lower in intact soil cores compared to sieved soils, suggesting that CH4 oxidation was limited by diffusion, a factor that could lead to lower field-measured CH4 uptake than suggested by biological oxidation capacity measured in the laboratory. Regardless of soil drainage characteristic, long-term NT resulted in significantly higher (2-3 times) CH4 diffusivity (mean: 2.5 x 10-3 cm2 s-1) than PT (1.5 x 10-3 cm2 s-1), probably due to improved soil aggregation and greater macro-pores volume in NT soils. Overall, these results confirm the positive impact of NT on the restoration of the biological (Vmax, Km and Th) and physical (diffusivity) soil attributes essential for CH4 uptake in croplands. Long-term implementation of NT farming can therefore contribute to the mitigation of CH4 emission from agriculture.