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ARS Home » Plains Area » Mandan, North Dakota » Northern Great Plains Research Laboratory » Research » Publications at this Location » Publication #311949
Title: High temporal frequency measurements of greenhouse gas emissions from soils

Author
item SAVAGE, K - Woods Hole Research Center
item PHILLIPS, R - Landcare Research
item DAVIDSON, E - Woods Hole Research Center

Submitted to: Biogeosciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2014
Publication Date: 5/21/2014
Publication URL: http://handle.nal.usda.gov/10113/60283
Citation: Savage, K., Phillips, R., Davidson, E. 2014. High temporal frequency measurements of greenhouse gas emissions from soils. Biogeosciences. 11:2709-2720.

Interpretive Summary: The production and transport of carbon dioxide, methane, and nitrous oxide in soils is strongly affected by changes in soil temperature and moisture. We developed new technology to integrate an automated soil respiration system with a newly available quantum cascade laser, which measures carbon dioxide, methane, and nitrous oxide fluxes from soils. The system was tested in early autumn at a forested wetland site in Howland, Maine and in spring at an alfalfa agricultural site near Mandan, North Dakota. The purpose of the test was to provide a range of conditions in which to run the automated system through sensitivity tests. Results indicated that the high temporal frequency of the automated system clearly characterized the transient response of all three gases to precipitation and demonstrated a clear day-night pattern related to temperature. A combination of high-frequency automated and spatially distributed chambers would be ideal for characterizing hot spots and “hot moments” of greenhouse gas fluxes from soils. This new automated method will enable continual, high-frequency, simultaneous measurements of the three most important greenhouse gases from natural and managed landscapes.

Technical Abstract: Carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are the most important anthropogenic greenhouse gases (GHGs). Variation in soil moisture can be very dynamic, and it is one of the dominant factors controlling the net exchange of these three GHGs. Although technologies for high-frequency, precise measurements of CO2 have been available for years, methods for measuring soil fluxes of CH4 and N2O at high temporal frequency have been hampered by lack of appropriate technology for in situ real-time measurements. A previously developed automated chamber system for measuring CO2 flux from soils was con- figured to run in line with a new quantum cascade laser (QCLAS) instrument that measures N2O and CH4. Here we present data from a forested wetland in Maine and an agricultural field in North Dakota, which provided examples of both net uptake and production for N2O and CH4. The objective was to provide a range of conditions in which to run the new system and to compare results to a traditional manual static-chamber method. The high-precision and more-than-10-times-lower minimum detectable flux of the QCLAS system, compared to the manual system, provided confidence in measurements of small N2O uptake in the forested wetland. At the agricultural field, the greatest difference between the automated and manual sampling systems came from the effect of the relatively infrequent manual sampling of the high spatial variation, or “hot spots”, in GHG fluxes. Hot spots greatly influenced the seasonal estimates, particularly for N2O, over one 74-day alfalfa crop cycle. The high temporal frequency of the automated system clearly characterized the transient response of all three GHGs to precipitation and demonstrated a clear diel pattern related to temperature for GHGs. A combination of high-frequency automated and spatially distributed chambers would be ideal for characterizing hot spots and “hot moments” of GHG fluxes.