Underneath the ground exists a vast “social network” that connects trees and other plants to each other.
This subterranean network is formed of roots, fungi and bacteria that provide trees with nutrients. It also plays an important role in the storage and cycling of carbon, with implications for climate change.
Scientists recently mapped this vast network of fungi for the first time on a global scale. Their results were published May 15 in the journal Nature.
To create this map of the mycorrhizal fungal network, researchers used the publicly available Global Forest Initiative database to access data on 1.1 million forest inventory plots. This included information on over 28,000 tree species in more than 70 countries.
The researchers’ results provide insight into how the underground fungal ecosystems function and how they vary in different climates throughout the world.
Mycorrhizal fungi are those that live in a symbiotic — mutually beneficial — relationship with a plant. Researchers identified two main groups associated with trees: ectomycorrhizal fungi that live around the tree’s roots and arbuscular fungi that penetrate the tree’s roots.
Arbuscular fungi live in warm tropical forests, where the climate promotes decomposition of leaf litter. This breakdown of organic matter is accompanied by a release of carbon into the atmosphere, which promotes faster carbon cycling in those regions.
Ectomycorrhizal fungi live in temperate and boreal regions. These areas are drier and colder, so leaf litter decomposition occurs at a much lower level. Carbon removed from the atmosphere by trees in these regions — and turned into leaves — is locked up for a longer time as organic material in the ground.
The different mycorrhizal fungi live on specific types of trees that are suited for the climates in those regions. Researchers found that although trees with ectomycorrhizal fungi represent only two percent of all plant species, they account for about 60 percent of all trees on the planet.
However, rising temperatures linked to climate change will likely cause a decline in ectomycorrhizal trees and an increase in arbuscular trees. A global shift toward the faster carbon-cycling arbuscular fungi could increase the level of carbon in the atmosphere — with a potential acceleration of climate change.
Although localized climate plays a big part in determining how fast leaf litter decomposes, the researchers found that feedback effects between the trees and fungi are also likely involved.
The researchers write in the paper that future research could also include plants other than trees, as well as non-forested biomes. This would give a better understanding of the global distribution of plant and fungal relationships.
Study author Thomas Crowther, Ph.D., told BBC News that this information could help scientists figure out how to restore ecosystems that are threatened by climate change and other human-caused environmental changes.
“I see the mycelium as the Earth's natural Internet, a consciousness with which we might be able to communicate. Through cross-species interfacing, we may one day exchange information with these sentient cellular networks. Because these externalized neurological nets sense any impression upon them, from footsteps to falling tree branches, they could relay enormous amounts of data regarding the movements of all organisms through the landscape.”
― Paul Stamets, Mycelium Running: How Mushrooms Can Help Save the World