Quantifying the Effects Sizes of Common Controls on Methane Emissions From an Ombrotrophic Peat Bog. Issue 4 (25th April 2023)

• Record Type: Journal Article
• Authors: Taylor, M. A.; Bradford, M. A.; Arnold, W.; Takahashi, D.; Colgan, T.; Davis, V.; Losos, D.; Peccia, J.; Raymond, P. A.
• Is Part Of: Journal of geophysical research. Volume 128:Issue 4(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-04-25
• Subjects: natural climate solutions -- methane -- greenhouse gases -- peat bog -- variability; Geobiology -- Periodicals; Biogeochemistry -- Periodicals; Biotic communities -- Periodicals; Geophysics -- Periodicals; 577.14
• DOI: 10.1029/2022JG007271
• Languages: English
• ISSNs: 2169-8953

Abstract

Abstract: Northern wetlands and bogs are a large source of biogenic methane (CH4 ) to the atmosphere and shape climate. There is then substantial interest in quantifying the effect sizes of controls on bog CH4 emissions. Yet quantification is complicated because wetland emissions are, like the controls that regulate them, spatially and temporarily heterogeneous within individual wetland systems. To account for this heterogeneity, we established 55 measurement plots in a sampling design that had extensive spatial, and repeated temporal, coverage over one ombrotrophic bog. This coverage allowed us to robustly estimate the effect sizes of known environmental controls on CH4 emissions such as temperature, water table depth (WTD), and plant functional composition. As expected, 89% of the cumulative measured flux came from 16% of the plots, with consistently high CH4 emissions over two consecutive growing seasons. Soil temperature exhibited the strongest control on emissions, while WTD and vegetation composition had much smaller relative effects compared to temperature. Interestingly, at high temperatures, WTD was a strong determinant of whether a plot had high versus lower emissions. Despite temperature's large effect size, the controls we measured only explained ∼29% of the variance in CH4 fluxes. Overall, our data confirm observations from other wetlands that CH4 emissions are highly variable at local scales, and yet our data also reveal that effect sizes can be quantified robustly within this heterogeneity. Highly‐replicated, local designs may therefore be useful for generating data that can serve to help refine wetland CH4 emissions uncertainties. Plain Language Summary: Wetlands are an important source of biogenic methane to the atmosphere. However methane emissions from wetland systems are very difficult to predict and model, and even harder to extrapolate given future climate warming. In this study, we measured methane emissions from many plots across an ombrotrophic bog to better constrain the size of the effects of commonly measured environmental controls on methane emissions. We found that soil temperature had a greater effect size than depth to water table and vegetation community on methane fluxes, although at high temperatures, shallow (wetter) water table depth (WTD) compounded high methane fluxes. Given the likelihood of future climate warming, methane emissions from wetlands are likely to increase further. Management of local factors like vegetation and WTD may help limit these methane emissions, but the strong temperature control suggests we should plan to aggressively reduce emissions from industrial sources to avert the wetland feedback to a warming climate. Key Points: Across 55 plots, during repeated measurements over 2 years a subset of 16% had consistently high CH4 emissions Soil temperature had the largest effect size on CH4 fluxes, increasing fluxes ∼11 times with a temperature increase from 0°C to 19°C Water table depth had an additive effect on CH4 emissions as temperature increased, increasing fluxes from 0.04 to 0.42 g CH4 m −2 d −1