Soil Warming Effects on Methane Production Pathways and Homoacetogenesis in a Northern Minnesota Peatland

Abstract

Peatlands have sequestered one third of terrestrial soil organic carbon while simultaneously emitting the potent greenhouse gas methane, and the response of these ecosystem functions to climate change remains largely unknown. Gaining a mechanistic understanding of the processes underlying anaerobic methane cycling is imperative to this question, especially elucidating the relative importance of the acetoclastic and hydrogenotrophic methane production pathways. Homoacetogenesis, the reduction of carbon dioxide with dihydrogen to acetate, is a highly understudied process due to being viewed as thermodynamically unfavorable, but it may play an important role in anaerobic carbon cycling. Here we show that homoacetogens are strong potential competitors with hydrogenotrophic methanogens, and this effect is most pronounced in deeper and colder peat depths. Our results indicate that a better understanding of understudied processes may be essential in predicting the response of anaerobic carbon cycling in peatlands to climate change. This dissertation contains unpublished co-authored material.