A major contributor to the current uncertainty regarding how carbon cycling in peatlands will respond to climate warming is the incomplete understanding of the production, storage and emission of free phase gas (FPG), a previously under-appreciated source of methane and carbon dioxide emissions to the atmosphere. It is increasingly clear that FPG production, storage and emission are regulated by hydraulic forcing, as well as the mechanical properties of the peat, i.e. that the carbon and water cycles in a peatland are intimately connected. The focus of this project is field-scale hydrological and hydrogeophysical research to further investigate the importance of recently invoked ?shallow? versus ?deep? peat models for the production, storage and emission of FPG in northern peatlands. Specific objectives of the project include [1] quantifying vertical variations in storage and release of methane with depth over a minimum six month time period at each of three locations within a peatland, [2] determining the hydrological forcing mechanisms that drive releases from both deep and shallow gas, [3] estimating spatial variations in storage and release as a function of subsurface heterogeneity, and [4] quantifying relative contributions of shallow versus deep gas to methane emissions from a northern peatland. This research will be conducted by coupling hydrogeological methods with novel chamber, geophysical and geodetic sensing technologies sensitive to FPG production, storage and emissions. The field site is Caribou Bog, a well-studied multi-unit peatland complex in central Maine. Empirical predictive models and simple mechanistic models will be developed to assess the relative importance of key forcing mechanisms on FPG emissions. Time-frequency analysis of time-series datasets will also be employed to improve understanding of likely forcing components regulating production, storage and release of FPG. This research will significantly advance our understanding of hydrological controls on FPG dynamics in northern peatlands, with important implications for the response of peatland carbon dynamics to climate change.
Northern peatlands globally cover more than 350 million ha and contain about one third of the terrestrially stored carbon. The fate of this carbon in response to continued climate warming is highly uncertain. Peatlands are also a source of atmospheric methane, a potent greenhouse gas that contributes to climate warming. This research will provide fundamental scientific knowledge needed to advance the understanding of the cycling of methane in peatlands, and how peatland hydrology controls the emission of methane from peatlands to the atmosphere. The work has direct societal relevance given the concerns about the environmental and economical affects of climate warming. In this project, Lois Stokes Alliance for Minority Participation undergraduate students will be exposed to a hands-on interdisciplinary research among three institutions. Furthermore, an international community of graduate students will participate in a student-focused session on methane cycling in northern peatlands at American Geophysical Union meetings. Community outreach in the vicinity of the Caribou Bog will occur via annual guided tours using the Orono Bog Boardwalk that served +30,000 visitors in 2009.
Peatlands are one of the largest natural producers of biogenic gases including methane and carbon dioxide, two greenhouse gases that contribute to global warming. Recent research over the last decade has shown that production, storage and emission of biogenic gas from peat soils is most likely regulated by hydraulic forcing, as well as the mechanical properties of the peat, suggesting that the carbon and water cycles in peat soils are intimately connected. The focus of this project is field-scale hydrogeophysical research in a northern peatland in Maine (Caribou Bog) to further investigate the importance of recently invoked "shallow" versus "deep" peat models for the production, storage and emission of biogenic gases in northern peatlands and the role of certain environmental variables such as atmospheric pressure for the rapid release of biogenic gas from peat soils. The outcomes of this three year project include evidence that: 1) changes in atmospheric pressure drive changes in the vertical distribution of free phase gas in peat soils and regulate methane ebullition from peat soils to the atmosphere, however differences exist between shallow and deep peat as reflected in a negative linear relation between changes in biogenic gas content and changes in atmospheric pressure for shallow peat soils and a positive linear relation for deeper soils; 2) peat structure plays a major role in the spatial distribution of biogenic gases in peat soils. These results highlight the variability in biogenic gas accumulation and distribution across peatlands and suggest that the nature of the peat matrix has a key role in defining how biogenic gas accumulates within and is released to the atmosphere from peat soils; and 3) autonomous GPR measurements show promise for better constraining temporal gas dynamics in peat soils, particularly as related to biogenic gas production and rapid releases (i.e. ebullition). Results from this research have resulted so far in three published peer-reviewed journal articles, nine published abstracts in conferences (mainly at the American Geophysical Union, AGU Fall Meeting), and one MS thesis. A student-based session on Carbon release and storage in peatlands organized at the 2012 AGU Fall meeting provided partial support through this grant to a total of 17 students that presented their research during both an oral and a poster session. Also, a total of 4 students from FAU (3 of them undergraduates) were involved in summer research and were engaged in a highly interdisciplinary summer field campaign in a unique natural environment where they were able to learn different methods applied to Carbon studies in peatlands including methods related to near-surface geophysics, hydrology or terrestrial-based LIDAR and interact with students and faculty from the two other institutions involved in this project (i.e. Rutgers University and University of Maine).
