Effect of peat quality on microbial greenhouse gas formation in an acidic fen

• Published in: Biogeosciences
• Main Authors: Reiche, M., Gleixner, G., Küsel, K.
• Format: Text
• Language: English
• Published: 2018
• Subjects: Curie Point; permafrost
• Online Access: https://doi.org/10.5194/bg-7-187-2010; https://www.biogeosciences.net/7/187/2010/

Peatlands play an important role in the global carbon cycle and represent both an important stock of soil carbon and a substantial natural source of relevant greenhouse gases like CO 2 and CH 4 . While it is known that the quality of organic matter affects microbial degradation and mineralization processes in peatlands, the manner in which the quality of peat organic matter affects the formation of CO 2 and CH 4 remains unclear. In this study we developed a fast and simple peat quality index in order to estimate its potential greenhouse gas formation by linking the thermo-degradability of peat with potential anaerobic CO 2 and CH 4 formation rates. Peat samples were obtained at several depths (0–40 cm) at four sampling locations from an acidic fen (pH 4.7). CO 2 and CH 4 formation rates were highly spatially variable and depended on depth, sampling location, and the composition of pyrolysable organic matter. Peat samples active in CO 2 and CH 4 formation had a quality index above 1.35, and the fraction of thermally labile pyrolyzable organic matter (comparable to easily available carbon substrates for microbial activity) obtained by thermogravimetry was above 35%. Curie-point pyrolysis-gas chromatography/mass spectrometry mainly identified carbohydrates and lignin as pyrolysis products in these samples, indicating that undecomposed organic matter was found in this fraction. In contrast, lipids and unspecific pyrolysis products, which indicate recalcitrant and highly decomposed organic matter, correlated significantly with lower CO 2 formation and reduced methanogenesis. Our results suggest that undecomposed organic matter is a prerequisite for CH 4 and CO 2 development in acidic fens. Furthermore, the new peat quality index should aide the estimation of potential greenhouse gas formation resulting from peatland restoration and permafrost thawing and help yield more robust models of trace gas fluxes from peatlands for climate change research.