Metabolic Capabilities Mute Positive Response to Direct and Indirect Impacts of Warming Throughout the Soil Profile

Rising global temperatures are expected to intensify soil microbial respiration and add to atmospheric carbon dioxide (CO₂) levels. Although vast amounts of carbon are stored in deep soils below ground, very little is known about how microbes manage carbon decomposition. This study investigated deep soil microbial activity in a unique experiment heating the first meter of soils in situ in Blodgett Experimental Forest in California. By using information gathered from environmental DNA (metagenomics and genomes) and process measurements, this study shows that deep soil microbes grow slowly but continue to release CO₂ when soils warmed and are not impacted by changes in carbon or nutrient availability.

Learning how belowground microbes will respond to higher soil temperatures is essential to scientists’ ability to make long-term predictions about the future of the carbon cycle in a changing climate. This study shows that when warming persists subsoil microbes respond as a constant source of respiration.

There is much uncertainty on the response of soil microbial communities to warming, particularly in the subsoil. This study investigated microbial community and metabolism response to 4.5 years of whole-profile soil warming. Scientists found depth-dependent changes in soil microbes and elevated subsoil microbial respiration with warming without any acclimation. The research shows that these findings potentially allow for continued enhanced microbial respiration rates.

The Terrestrial Ecosystem Science Program of the Office of Biological and Environmental Research, within the U.S. Department of Energy (DOE) Office of Science, under DOE contract DE-AC02-05CH11231 to Lawrence Berkeley National Laboratory. Nicholas Dove was supported by the DOE Office of Science Graduate Student Research Program, which is administered by the Oak Ridge Institute for Science and Education (DE-SC0014664), and postdoctoral development funds were provided by Oak Ridge National Laboratory (ORNL). ORNL is managed by UT-Battelle, LLC, for DOE under contract DE-AC05-00OR22725).