Elevated Temperatures Alter Microbial Communities During In Situ Peat Decomposition

The Science

Peatlands are large carbon sinks with primary production outpacing decomposition of organic matter. Results from the Spruce and Peatland Responses Under Changing Environments (SPRUCE) study show net losses of organic matter and increased greenhouse gas production from peatlands in response to whole-ecosystem warming.

Researchers assessed depth-specific rates and mechanisms of peat decomposition across elevated temperatures using a newly adapted “peat decomposition ladder” approach. After the first 3 years of study, warming (up to +9°C) had little effect on peat decomposition or organic matter quality. Low rates of mass loss (~4.5%) were observed across all treatments. Microbial communities, however, showed increases in diversity as well as alteration of patterns within their interaction networks with warming treatments.

The Impact

Slow decomposition rates are a key characteristic of peatlands that lead to large terrestrial carbon stocks, but these rates are difficult to measure in situ. This research showed decomposition rates were not significantly altered by elevated temperature over the first 3 study years.

Summary

Researchers investigated how warming and elevated carbon dioxide (CO₂) impact peat microbial communities and peat soil decomposition rates. The team characterized microbial communities through amplicon sequencing and compositional changes across 4 depth increments.

Soil depth, temperature, and CO₂ treatment significantly impacted microbial diversity and community composition. Bacterial/archaeal α-diversity increased significantly with increasing temperature, and fungal α-diversity was lower under elevated CO₂ treatments. Transdomain microbial networks showed higher complexity of microbial communities in decomposition ladder depths from the warmed enclosures. The number of highly connected hub taxa within the networks was positively correlated with temperature. Methanogenic hubs were identified in the networks constructed from the warmest enclosures, indicating increased importance of methanogenesis in response to warming.

However, microbial community responses were not reflected in measures of peat soil decomposition as warming and elevated CO₂ had no significant short-term effects on soil mass loss or chemical composition. Regardless of treatment, 4.5% of the original soil mass was lost on average after 3 years. Variation between replicates was high, potentially masking treatment effects. Previous results from the SPRUCE experiment have shown warming is accelerating organic-matter decomposition and CO₂ and methane production. Results suggest warming-induced shifts in microbial communities may be driving these changes.

Principal Investigator

Christopher Schadt
Oak Ridge National Laboratory
[email protected]

Co-Principal Investigator

Paul Hanson
Oak Ridge National Laboratory
[email protected]

Program Manager

Brian Benscoter
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
[email protected]

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
[email protected]

Funding

This research was sponsored by the Biological and Environmental Research program within the U.S. Department of Energy’s Office of Science as part of the Terrestrial Ecosystem Science (TES) Science Focus Area at Oak Ridge National Laboratory.

References