Soil researchers quantify an underappreciated factor in carbon release to the atmosphere

November 27, 2017

AMHERST, Mass. - Soil plays a critical role in global carbon cycling, in part because soil organic matter stores three times more carbon than the atmosphere. Now biogeochemist Marco Keiluweit at the University of Massachusetts Amherst and colleagues elsewhere for the first time provide evidence that anaerobic microsites play a much larger role in stabilizing carbon in soils than previously thought.

Further, current models used to predict the release of climate-active CO2 from soils fail to account for these microscopic, oxygen-free zones present in many upland soils, they say.

"Without recognizing the importance of anaerobic microsites in stabilizing soil carbon in soils, models are likely to underestimate the vulnerability of the soil carbon reservoir to disturbance induced by climate or land use change," write first author Keiluweit and colleagues at Stanford, Oregon State University, Lawrence Berkeley National Laboratory and the Institute of Soil Landscape Research, Germany.

Findings add another twist to the ongoing debate, they add, over "the mechanisms controlling long-term stabilization of carbon in soils." Details appear in the current issue of Nature Communications.

Keiluweit explains, "Even though the presence of anaerobic microsites has long been known, this is the first study to assess their impact on Carbon stabilization. Before, they attributed the persistence of the large carbon stocks in upland soils to other stabilization mechanisms. Because these other stabilization mechanisms are likely much less vulnerable to disturbance than anaerobic microsites, our research suggests that the impact of climate or land use change may release greater amounts of carbon from soils than we expected."

He and colleagues expect the new information will propel climate modelers to refine their models to better predict what may happen in the future as soils are disturbed by climate change.

Anaerobic microsites in soil are microscopic habitats lacking oxygen in which microbes are limited in their ability to metabolize soil organic matter into climate-active CO2 that is released to the atmosphere. Without oxygen, their respiration slows or comes to a stop.

For this work, Keiluweit and colleagues conducted controlled laboratory experiments in which they recreated anaerobic microsites and showed how they reduce the metabolism of organic matter and the release of CO2. They also isolated anaerobic microsites in agricultural soils in the field, where they found anaerobic microsites to have the same effect.

They write, "We show that anaerobic microsites are important regulators of soil carbon persistence, shifting microbial metabolism to less efficient anaerobic respiration and selectively protecting otherwise bioavailable, reduced organic compounds such as lipids and waxes from decomposition.

Further, shifting from anaerobic to aerobic conditions leads to a 10-fold increase in volume-specific mineralization rate, illustrating the sensitivity of anaerobically protected carbon to disturbance. Vulnerability of anaerobically protected carbon to future climate or land use change thus constitutes a yet unrecognized soil carbon-climate feedback that should be incorporated into terrestrial ecosystem models."

Keiluweit, assistant professor in UMass Amherst's School of Earth and Sustainability, says the team's next steps include quantifying the amount of anaerobic microsites in different soil ecosystems and assessing how carbon stabilization in them is affected by variables such as the soil hydrologic regime, which is expected to change dramatically due to climate change.
-end-
This work was supported by the U.S. Department of Energy's Office of Biological and Environmental Research, Terrestrial Ecosystem and Subsurface Biogeochemistry programs. Synchroton-based spectroscopy support came from the Canadian Light Source, Canada's national facility at the University of Saskatchewan, Saskatoon. Other analytical support came from the staff at the Pacific Northwest National Laboratory, Richland, Washington.

University of Massachusetts at Amherst

Related Climate Change Articles from Brightsurf:

Are climate scientists being too cautious when linking extreme weather to climate change?
Climate science has focused on avoiding false alarms when linking extreme events to climate change.

Mysterious climate change
New research findings underline the crucial role that sea ice throughout the Southern Ocean played for atmospheric CO2 in times of rapid climate change in the past.

Mapping the path of climate change
Predicting a major transition, such as climate change, is extremely difficult, but the probabilistic framework developed by the authors is the first step in identifying the path between a shift in two environmental states.

Small change for climate change: Time to increase research funding to save the world
A new study shows that there is a huge disproportion in the level of funding for social science research into the greatest challenge in combating global warming -- how to get individuals and societies to overcome ingrained human habits to make the changes necessary to mitigate climate change.

Sub-national 'climate clubs' could offer key to combating climate change
'Climate clubs' offering membership for sub-national states, in addition to just countries, could speed up progress towards a globally harmonized climate change policy, which in turn offers a way to achieve stronger climate policies in all countries.

Review of Chinese atmospheric science research over the past 70 years: Climate and climate change
Over the past 70 years since the foundation of the People's Republic of China, Chinese scientists have made great contributions to various fields in the research of atmospheric sciences, which attracted worldwide attention.

A CERN for climate change
In a Perspective article appearing in this week's Proceedings of the National Academy of Sciences, Tim Palmer (Oxford University), and Bjorn Stevens (Max Planck Society), critically reflect on the present state of Earth system modelling.

Fairy-wrens change breeding habits to cope with climate change
Warmer temperatures linked to climate change are having a big impact on the breeding habits of one of Australia's most recognisable bird species, according to researchers at The Australian National University (ANU).

Believing in climate change doesn't mean you are preparing for climate change, study finds
Notre Dame researchers found that although coastal homeowners may perceive a worsening of climate change-related hazards, these attitudes are largely unrelated to a homeowner's expectations of actual home damage.

Older forests resist change -- climate change, that is
Older forests in eastern North America are less vulnerable to climate change than younger forests, particularly for carbon storage, timber production, and biodiversity, new research finds.

Read More: Climate Change News and Climate Change Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.