Carbon feedback from forest soils will accelerate global warming, 26-year study projects
WOODS HOLE, Mass. — After 26 years, the world’s longest-running experiment to discover how warming temperatures affect forest soils has revealed a surprising, cyclical response: Soil warming stimulates periods of abundant carbon release from the soil to the atmosphere alternating with periods of no detectable loss in soil carbon stores. Overall, the results indicate that in a warming world, a self-reinforcing and perhaps uncontrollable carbon feedback will occur between forest soils and the climate system, adding to the build-up of atmospheric carbon dioxide caused by burning fossil fuels and accelerating global warming. The study, led by Jerry Melillo, Distinguished Scientist at the Marine Biological Laboratory (MBL), appears in the October 6 issue of Science.
Melillo and colleagues began this pioneering experiment in 1991 in a deciduous forest stand at the Harvard Forest in Massachusetts. They buried electrical cables in a set of plots and heated the soil 5° C above the ambient temperature of control plots. Over the course of the 26-year experiment (which still continues), the warmed plots lost 17 percent of the carbon that had been stored in organic matter in the top 60 centimeters of soil.
“To put this in context,” Melillo says, “each year, mostly from fossil fuel burning, we are releasing about 10 billion metric tons of carbon into the atmosphere. That’s what’s causing the increase in atmospheric carbon dioxide concentration and global warming. The world’s soils contain about 3,500 billion metric tons of carbon. If a significant amount of that soil carbon is added to the atmosphere, due to microbial activity in warmer soils, that will accelerate the global warming process. And once this self-reinforcing feedback begins, there is no easy way to turn it off. There is no switch to flip.”
Over the course of the experiment, Melillo’s team observed fluctuations in the rate of soil carbon emission from the heated plots, indicating cycles in the capacity of soil microbes to degrade organic matter and release carbon. Phase I (1991 to 2000) was a period of substantial soil carbon loss that was rapid at first, then slowed to near zero. In Phase II (2001-2007), there was no difference in carbon emissions between the warmed and the control plots. During that time, the soil microbial community in the warmed plots was undergoing reorganization that led to changes in the community’s structure and function. In Phase III (2008-2013), carbon release from heated plots again exceeded that from control plots. This coincided with a continued shift in the soil microbial community. Microbes that can degrade more recalcitrant soil organic matter, such as lignin, became more dominant, as shown by genomic and extracellular enzyme analyses. In Phase IV (2014 to current), carbon emissions from the heated plots have again dropped, suggesting that another reorganization of the soil microbial community could be underway. If the cyclical pattern continues, Phase IV will eventually transition to another phase of higher carbon loss from the heated plots.
“This work emphasizes the value of long-term ecological studies that are the hallmark of research at the MBL’s Ecosystems Center,” says David Mark Welch, MBL’s Director of Research. “These large field studies, combined with modeling and an increasingly sophisticated understanding of the role of microbial communities in ecosystem dynamics, provide new insight to the challenges posed by climate change.”
“The future is a warmer future. How much warmer is the issue,” Melillo says. “In terms of carbon emissions from fossil fuels, we could control that. We could shut down coal-fired power plants, for example. But if the microbes in all landscapes respond to warming in the same way as we’ve observed in mid-latitude forest soils, this self-reinforcing feedback phenomenon will go on for a while and we are not going to be able to turn those microbes off. Of special concern is the big pool of easily decomposed carbon that is frozen in Artic soils. As those soils thaw out, this feedback phenomenon would be an important component of the climate system, with climate change feeding itself in a warming world.”
###
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
Very apt having the picture of the experimental grounds blanketed in snow. 🙂
So if bacterial action can release all this carbon, doesn’t the most characteristic feature of bacteria, their rapid doubling and redoubling sequester alot of carbon? Doesn’t the released carbon promote expansion of trees and other plants, raining down more leaves, plankton and other sea creatures produce more calcium Carbonate? Today’s biologists are too activist to be objective. Have they been taught what a mass balance is in a process? A metallurgist or chemist could teach them. If your professor doesn’t know, even wiki can help:
https://en.m.wikipedia.org/wiki/Mass_balance
To prevent this all soil in the world must be convered in reinforced concrete. Let us hurry up and get this done.
Overall, the authors claim was credible, based on the fact that he used scientific research conducted by the University of Chicago’s Department of Ecology, which appeared in an issue of Science, on how soil is contributing to increasing atmospheric carbon dioxide. Upon reading an article titled “Carbon Dioxide Flux from Three Arctic Tundra Types in North-Central Alaska” the claim is supported as the same result is not only seen in Massachusetts, but in a more northerly state Alaska (Poole, 1982). This provides further evidence that it was not the environmental conditions in Massachusetts that were causing carbon to leach from the soil, therefore the claim is valid. The author provided a good comparison on the amount of Carbon that is being emitted from burning fossil fuels to soil, which strengthened his claim that the soil is the primary reason for increasing atmospheric CO2. It would have been interesting and enhanced his claim if further research being conducted to understand the feedback systems involved in leaching CO2 from the soil were mentioned as it as a major factor in contributing to CO2 emissions.