Study Provides a Clearer Picture of Soil in the Warming World

According to the latest study made by experts at Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of Zurich, the organic molecules recommended for carbon sequestration in deep soil are very sensitive to disintegration under global warming conditions.

The discovery has ramifications for a fundamental carbon management method that depends on soil and forests as natural carbon “sinks” to counteract global warming.

Forests, grasslands, and rangelands absorb around 25% of global carbon emissions. Plants store carbon in their cell walls and in the soil during photosynthesis. Soils hold twice as much carbon as the atmosphere due to rich carbon reserves from decades ago, and deeper subsoils (greater than 8 inches or 20 centimetres) account for about half of soil carbon.

However, as the world’s population grows, so do our needs for more croplands and wood. According to research, disrupting the natural environment for commercial purposes comes with a cost: the United Nations’ Intergovernmental Panel on Climate Change has cautioned that emissions from deforestation and agriculture account for around one-fifth of worldwide greenhouse gas emissions.

“Our study shows that climate change will affect all aspects of soil carbon and nutrient cycling. It also shows that in terms of carbon sequestration, there’s no silver bullet. If we want soil to sustain carbon sequestration in a warming world, we will need better soil management practices, which can mean minimal disturbance of soils during forest management and agriculture,” 

said Margaret Torn, a senior scientist in Berkeley Lab’s Earth & Environmental Sciences Area and a senior author of the study.

Torn and her colleagues presented the first concrete proof in 2021 that higher temperatures cause a large decline in carbon stores held in deep forest soils – a 33% loss over five years.

Torn and lead author Cyrill Zosso of the University of Zurich present a clearer picture of soil in a warming world in their new study. This is the first study to indicate that rising temperatures cause a considerable decline in soil organic carbon molecules produced by plants during photosynthesis.

The researchers utilised vertical heating rods to continually warm 1-meter-deep (three-foot-deep) areas of soil by 4 degrees Celsius (7 degrees Fahrenheit) during an experiment at the University of California’s Blodgett Forest Research Station in the foothills of California’s Sierra Nevada mountains. That is the amount of warmth predicted by the end of the twenty-first century if greenhouse gas emissions continue to rise.

They discovered that 4.5 years of warming at this temperature resulted in significant changes in carbon stores at a depth of more than 30 centimetres (or nearly 12 inches) below the soil surface.

Zosso identified organic components influenced by heat during spectroscopic studies at the University of Zurich.

The findings were startling: a 17% decrease in lignin (the molecules that give plants stiffness) and a nearly 30% decrease in cutin and suberin (the waxy substances in leaves, stems, and roots that protect plants from infections).

Torn and Zosso were also startled to discover a substantial variation in the quantity of “pyrogenic carbon” in soil samples that had been heated artificially vs those that had not. Pyrogenic carbon is a form of organic carbon found in soil that is derived from burned plants and other organic matter leftovers left over from a wildfire.

Many researchers assume that pyrogenic carbon has the most potential to serve as a very stable form of sequestered carbon. “We found much less pyrogenic carbon in the deep soils when they were heated,” Torn said

“Pyrogenic carbon can stay in the soil for decades or even centuries, but we need to understand its vulnerability to warming or to changes in land management. Our study suggests that this material decomposed just as fast as anything else would when the soil was warmed,” Torn explained. “This shows that when you put material deep into soil where it’s in contact with minerals and microbes, those natural systems will decompose the material over time.”

The researchers intend to resample soil from the study in order to evaluate how nine years of warming affect soil composition and health. A second grassland warming experiment is also planned for the Point Reyes National Seashore in Northern California. “We are also organising all of the world’s deep-soil warming (or whole-soil warming) experiments to share data and know-how, and we are conducting data synthesis to see what we can learn,” Torn explained.

The DOE Office of Science (Office of Biological and Environmental Research) and the Swiss National Science Foundation funded this research.

Lawrence Berkeley National Laboratory, founded in 1931 on the principle that the greatest scientific issues are best solved by teams, and its scientists have received 16 Nobel Prizes. Today, Berkeley Lab researchers work on sustainable energy and environmental solutions, the development of useful new materials, the advancement of computer frontiers, and the investigation of the secrets of life, matter, and the cosmos.

Scientists from all over the world use the Lab’s facilities to conduct their own research. Berkeley Lab is a multi-program national laboratory run by the University of California for the Office of Science of the United States Department of Energy.

DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time.

Source: lbl.gov

 

 

 

 

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