Trace gas fluxes from tidal salt marsh soils: implications for carbon–sulfur biogeochemistry

[摘要] Tidal salt marsh soils can be a dynamic source of greenhouse gases such ascarbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O),as well as sulfur-based trace gases such as carbon disulfide (CS 2 ) anddimethylsulfide (DMS) which play roles in global climate and carbon–sulfurbiogeochemistry. Due to the difficulty in measuring trace gases in coastalecosystems (e.g., flooding, salinity), our current understanding is based onsnapshot instantaneous measurements (e.g., performed during daytime lowtide) which complicates our ability to assess the role of these ecosystemsfor natural climate solutions. We performed continuous, automatedmeasurements of soil trace gas fluxes throughout the growing season toobtain high-temporal frequency data and to provide insights into magnitudesand temporal variability across rapidly changing conditions such as tidalcycles. We found that soil CO 2 fluxes did not show a consistent dielpattern, CH 4 , N 2 O, and CS 2 fluxes were highly variable withfrequent pulse emissions ( >  2500 %, >  10 000 %,and >  4500 % change, respectively), and DMS fluxes onlyoccurred midday with changes >  185 000 %. When we comparedcontinuous measurements with discrete temporal measurements (during daytime,at low tide), discrete measurements of soil CO 2 fluxes were comparablewith those from continuous measurements but misrepresent the temporalvariability and magnitudes of CH 4 , N 2 O, DMS, and CS 2 .Discrepancies between the continuous and discrete measurement data result indifferences for calculating the sustained global warming potential (SGWP),mainly by an overestimation of CH 4 fluxes when using discretemeasurements. The high temporal variability of trace gas fluxes complicatesthe accurate calculation of budgets for use in blue carbon accounting andearth system models.

[学科分类] 大气科学