2024 Abstracts

Microbial Community Dynamics During 3 Years of in situ Peat Decomposition at the SPRUCE Experiment in Northern Minnesota


Christopher W. Schadt1,2* (schadtcw@ornl.gov), Spencer Roth1, Natalie A. Griffiths2,3, Randall K. Kolka4, Keith C. Oleheiser2,3, Alyssa A. Carrell1, Dawn M. Klingeman1, Angela Seibert5, Jeffrey P. Chanton6, Paul J. Hanson2,3, Melanie Mayes2,3, Daniel Ricciuto2,3


1Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN; 2Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN;  3Climate Change Science Institute, Oak Ridge National Laboratory, Oak Ridge, TN; 4Northern Research Station, USDA Forest Service, Grand Rapids, MN; 5Department of Geosciences, Boise State University, Boise, ID; 6Department of Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, FL



Peatlands ecosystems act as major global carbon sinks, as primary production outpaces organic matter decomposition resulting in massive soil carbon deposits that account for greater than one third of all soil carbon. Prior investigations as part of the Spruce and Peatland Response Under Changing Environments (SPRUCE) experiment have shown that warming treatments are altering peatland biogeochemistry, greatly increasing the efflux rates of both carbon dioxide (CO2) and methane (CH4) from the ecosystem manipulation chambers. In order to better understand microbial dynamics contributing to these changes, the team deployed a series of depth specific decomposition bags attached to rigid frames (e.g., peat ladders) in triplicate across the temperature and CO2 treatment enclosures for 3 years. At harvest the team characterized Bacteria, Archaea, and Fungi community dynamics through amplicon sequencing and measured peat mass and peat chemistry changes. These results showed that microbial communities were significantly affected across soil depths, temperature and temperature x CO2 treatments in the experiment and that diversity increased with temperature treatments. Microbial communities also showed greater degrees of complexity and across network analyses and an increase in highly connected hub taxa with increasing temperatures that included methanogens. Despite this, peat soil decomposition showed no significant effects on soil mass loss or chemical composition after 3 years in situ incubation, with only ~4.5% mass loss overall. These results are planned to be revisited from additional peat ladders that were deployed at the same time as researchers wrap up the final years of the SPRUCE experiment. This and previous studies from the SPRUCE experiment have now shown that warming is accelerating microbial community change, organic-matter decomposition, and subsequently CO2 and CH4 production from these globally important carbon reservoirs, raising the overall level of concern for climate change driven positive feedback loops from these ecosystems.