Peatland Greenhouse Gas Efflux (CO2, CH4) Increases Due to Plant-Microbial Dynamics in Response to Whole Ecosystem Warming
Authors
Jonathan Stelling* (stellingjm@ornl.gov), Melanie Mayes, Paul Hanson, Misha Krassovski, Daniel Ricciuto
Institutions
Oak Ridge National Laboratory, Oak Ridge, TN
URLs
Abstract
Peatlands, although only covering a small portion of the land surface store around one third of soil carbon. This high amount of carbon sequestration is sustained by climate; hydrology and temperature trends sustain high water tables that promote autotrophic carbon fixation and prevent aerobic decomposition. These carbon stores are tied to complex ecosystem processes such as plant and microbial community composition and may be threatened by future warming. To test the sensitivity of these carbon stocks to climate change scenarios researchers utilize the whole ecosystem manipulation of the Spruce and Peatland Under Changing Environments (SPRUCE) experiment in northern Minnesota.
Here researchers present greenhouse gas flux (GHG: carbon dioxide-CO2 and methane-CH4) across experimentally warmed (from +0 to +9°C) and elevated atmospheric CO2 (+500 ppm). Researchers use automated clear-top gas flux chambers to measure changes in net ecosystem exchange (NEE) CO2 and CH4 four times per hour during the growing season of 2022 and 2023. Researchers compare gas flux measurements to a suite of other environmental response variables: photosynthetically active radiation, water table depth, and soil temperature and moisture.
These results show: GHG flux increases with warming soil temperatures, net carbon flux to the atmosphere increases following a linear relationship. Water table depth and temperature preconditions dynamics may cause switch between the dominant gas flux between CO2 and CH4.
In addition, measured CO2 NEE showed that elevated CO2 plots had increased daytime uptake of CO2 during the growing season, possibly due to CO2 fertilization effects. However, this increased uptake was outweighed by increased ecosystem respiration. Furthermore, CH4 flux was more dominant in ambient CO2 levels, indicating complex ecosystem feedback effects.
Future work will be focused on key peatland carbon relationships such as; CO2 fertilization changes to water table and microbial community dynamics, increased individual plant function and plant functional type transitions within experimental plots.