DISSERTATION RESEARCH: Partitioning rhizosphere effects on microbial community structure and carbon cycling across a peatland water table gradient.

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Peatlands, such as bogs, are unique ecosystems that occupy only a small fraction of the Earth's land surface but contain vast quantities of carbon. Peatlands store so much carbon because they are saturated with water, and this creates an anaerobic environment that slows decomposition of complex organic (carbon-containing) substances. Over the next 100 years, heightened drought frequency and severity is projected to reduce water table heights in high latitude peatlands, causing them to emit more carbon gases to the atmosphere. The goal of this project is to identify the effect of water table reduction and associated changes in plant community structure on the microorganisms living in a northern peatland. The release of carbon gasses is controlled by these microorganisms through their decomposition of organic material. The work will provide novel insight into the impact of physical and plant-mediated environmental changes on microbial community structure and activity, and will deepeour understanding of ecosystem responses to climate change. In addition to support the graduate student's doctoral dissertation research, this project will also provide opportunities for Boston University undergraduates to learn laboratory techniques and methods of data analysis, and the research scientists leading this project will develop educational modules related to peatland carbon storage that will be presented at area elementary schools and community festivals.Microbial (bacteria and funga) groups have distinct physiology and developmental histories that will impact their responses to water table decline and contribute to changes in ecosystem carbon and nitrogen cycling. Changes in vascular plant abundance and root biomass associated with water table decline may further impact the microbial environment through increased plant-carbon allocation to mycorrhizal fungal communities. In particular, this research seeks to determine if the physical effect of water table reduction on microbial community composition, enzyme production, and carbon mineralization is amplified by increased vascular plant abundance and carbon allocation to mycorrhizal fungal communities. The research will leverage an ongoing rhizosphere partitioning experiment across a natural water table gradient in Caribou Bog, Maine. Microbial community composition in three rhizosphere communities isolated within root and fungal ingrowth and exclusion cores installed across the water table gradient will be compared to separate the influence ofphysical changes in water table from the biological influence of plants and mycorrhizal fungi. The proposed analyses will complement ongoing microbial functional analyses and identify relationships between microbial activity and composition in response to declines in the water table and in the presence or absence of plant and mycorrrhizal inputs.