Northern boreal forests are easily recognized for their majestic trees and have been credited with helping to sequester much of the world’s carbon dioxide. It was originally thought that vegetative matter was what was sinking the greenhouse gas. Now, a diverse team of scientists from Sweden have discovered that these great, soaring plants are getting a lot of help from some humble decomposers living in the soil. Their findings, published in the journal Science, revealed that fungi were responsible for up to an incredible 70 percent of soil carbon in certain samples.

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Researchers have long known that boreal forests were able to suck up a good deal of carbon, but were previously unclear as to where it went and how it was absorbed. They had thought that the carbon was carried to the tree’s needles and dropped to the forest floor where decomposition would leech it into the environment. If that were true, they would expect to find the newest carbon deposits close to the surface. However, after taking soil samples from over 30 islands and two small lakes in Sweden, they saw that the new deposits were more likely to be found farther down, pulled to the roots of the trees by fungus. The mycorrhizal fungus has evolved a special relationship with the trees where it colonizes in the roots and assists the tree. The fungus gets access to a more consistent stream of carbohydrates and other sugars, and the tree in return has access to more water and minerals.

The study found that fungi were responsible for 47 percent of soil carbon in large island samples, and an amazing 70 percent in some small island samples. While the scientists are not exactly sure why there was a difference in the numbers, they postulate it is due to varying rates of decomposition. The total amount of carbon stored by the boreal forests is significant, as 11 percent of the earth’s surface is covered in these ecosystems. An estimated 16 percent of the globe’s carbon is held there, and as climate change advances, researchers will be monitoring its expansion due to warmer temperatures. In light of their findings, it is still unclear as how new plants will affect the balance of the world’s carbon. What is becoming more apparent is that the mighty mushroom has has a very important part to play.

+ Science


Images via Wikicommons users Tocekas and Thergothon