Forests can store as much as 45% of world’s terrestrial carbon but as temperatures rise, release carbon


A new study by a team researchers including U of T Scarborough Professor Myrna Simpson reveals that as global temperatures rise the organic matter in forests appear to be breaking down more quickly, accelerating the release of carbon into the atmosphere. Credit: U of T Scarborough

A carbon sink that can’t be filled

Posted: 07 Jan 2016 07:48 AM PST

As global temperatures rise, the organic matter in forests appears to break down more quickly, which is accelerating the release of carbon into the atmosphere, according to new research.
Forests can store as much as 45 percent of the world’s terrestrial carbon, making them a critical part of the process of regulating climate change. As global temperatures rise, though, the organic matter in forests appears to break down more quickly, accelerating the release of carbon into the atmosphere.

This surprising conclusion comes out of a long-term study that was intended to find means to mitigate global warming, not exacerbate it. “Our question was, ‘How much carbon can the soil hold?'” says UTSC professor of environmental chemistry, Myrna Simpson. “But in our experiments, we found that soil was not the limiting factor. We couldn’t even get to the carbon saturation point.”…”The scientific community widely accepts that soil organic matter chemistry is tied to inputs,” she says. “But we were surprised to see that all of our litter manipulation resulted in accelerated breakdown of organic matter.” Climate change could lead to “more productive” forests — bigger trees and more vegetation. This productivity would naturally increase the amount of litter, and therefore the amount of carbon sinking into the soil in the form of organic matter. But in a paper published recently in the journal Biogeochemistry, Simpson and her co-authors describe how they simulated this change by doubling the amount of litter in sections of the forest in the hope that the soil could absorb more carbon. Instead, the increased litter stimulated bacterial and fungal activity. Organic matter broke down more quickly, eliminating any carbon storage benefit and releasing more CO2 into the atmosphere. “Altering the litter did more harm than good,” Simpson says. “Ours was a human manipulation, but it could as easily be altered through climate change.”…


Oliva Pisani, Serita D. Frey, André J. Simpson, Myrna J. Simpson. Soil warming and nitrogen deposition alter soil organic matter composition at the molecular-level. Biogeochemistry, 2015; 123 (3): 391 DOI: 10.1007/s10533-015-0073-8

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