Highly Dynamic Versus Monthly Community Net Carbon Dioxide and Methane Flux Observations for SPRUCE Warming by Elevated Carbon Dioxide Experiment: Comparing Integrated Data


Paul J. Hanson* (hansonpj@ornl.gov), Misha Krassovski, Melanie A. Mayes, Kyle Pearson


Oak Ridge National Laboratory, Oak Ridge, TN



The net flux of carbon dioxide (CO2) and methane (CH4) from the intact peatland community being studied in the SPRUCE experiment is a critical component of the ecosystem carbon budget and a controlling variable that determines the performance of the ecosystem as a landscape source or sink of carbon. In the first 6 years of SPRUCE operations, net flux of these two gases were collected across warming treatments at approximately monthly intervals throughout the active season to capture seasonal dynamics of flux and the relative balance between CO2 and CH4 emissions. These data were integrated over time based on half-hourly environmental data correlated with the observed fluxes and used as a primary input for calculated net ecosystem carbon exchange. Upon the advice of the SPRUCE Advisory Panel members, and with DOE financial support, automated flux chambers capable of subhourly observations of flux were deployed to the SPRUCE treatment plots in 2022 and contrasted with occasional manual, large-collar flux observations. Comparative observations for 2022 showed comparable CO2 and CH4 flux magnitudes between approaches, but also provided clear evidence of transient spikes of CH4 flux often missed by the periodic manual flux observations. This analysis will present these data and integrated flux estimates using each approach and propose improved mechanistic representations for net greenhouse gas fluxes necessary to include the dynamic nature of episodic CH4 release from the peatland.