Small Differences in Ombrotrophy Control Regional-Scale Variation in Methane Cycling among Sphagnum-Dominated Peatlands
Large variation in methane emissions among bogs suggests caution in scaling results and associated regional extrapolations.
A detailed biogeochemical and microbial study of three moss-dominated, low-pH peatlands in northern Minnesota, as well as a survey of methane production potentials in 19 peatlands in the Upper Peninsula of Michigan, showed a large difference in methane production and emissions in bog-like peatlands despite initial similarities. These experiments demonstrate that it is common to have high variation in methane cycling in seemingly similar peatlands within a single geographical region.
Caution is urged in extrapolating results from a small number of bog and peatland sites to regional responses in methane dynamics in peatlands due to considerable variability in methane cycling.
There is limited understanding of the variability associated with methane (CH4) cycling among low-pH, Sphagnum moss–dominated peatlands within a geographical region. Here, a team of researchers from the University of Oregon and Chapman University report the results from two studies exploring the controls of CH4 cycling in peatlands from the Upper Midwest (USA). Potential CH4 production and resultant carbon dioxide (CO2):CH4 ratios varied by several orders of magnitude among 19 peatlands in the Upper Peninsula of Michigan. They also more intensively examined CH4 dynamics in three bog-like, acidic, Sphagnum-dominated peatlands in northern Minnesota. Net CH4 flux was lowest in the peatland with well-developed hummocks, and the isotopic composition of the :CH4 along with methanotroph gene expression indicated a strong role for CH4 oxidation in controlling net CH4 flux. These experiments demonstrate that it is common to have high variation in CH4 cycling in seemingly similar peatlands within a single geographical region. Caution should be used when extrapolating data from a single site to the landscape scale, even for outwardly very similar peatlands, and it is best to place manipulative experiments in multiple peatlands to encompass this variability. The macroscale development of peatlands, and concomitantly their microtopography as expressed in the proportion of hummocks, hollows, lawns, and pools, needs to be considered as central controls over CH4 emissions in methane modeling.
University of Oregon
This material is based on work supported by the Office of Biological and Environmental Research, within the U.S. Department of Energy (DOE) Office of Science, under award numbers DE-SC0008092, DE-SC0014416, DE-SC0007144, DESC0012288, and DE-SC0012088; the DOE Office of Science Graduate Fellowship Program (DE-AC05- 06OR23100); and the National Science Foundation under award number DEB-0816575.
Zalman, C. et al. “Small differences in ombrotrophy control regional-scale variation in methane cycling among Sphagnum-dominated peatlands.” Biogeochemistry 139, 155–177 (2018). [DOI:10.1007/s10533-018-0460-z]
Zalman, C. et al. 2018. SPRUCE Small Differences in Ombrotrophy Control Regional-Scale Variation in Methane Cycling among Sphagnum-Dominated Peatlands: Supporting Data. Oak Ridge National Laboratory, Oak Ridge, Tenn., USA.