Do forest trees really 'talk' through underground fungi?

The notion that forest trees may communicate with one another, exchange nutrients with their seedlings, and even defend them via an underground network of fine fungal filaments is intriguing.

The theory is so interesting that it has gained traction in popular culture and has been termed the "wood-wide web"; nevertheless, University of Alberta researcher Justine Karst warns that the science supporting those theories is unsubstantiated.

Karst and two colleagues challenge three widely held notions about the abilities of underground fungi known as common mycorrhizal networks, or CMNs, which connect the roots of various plants underground. Their arguments are presented in an article that was published in Nature Ecology & Evolution and also includes their own opinions. Molds, yeast, and mushrooms are examples of fungi, which are living creatures.

Karst, an associate professor in the University of Alberta's Faculty of Agricultural, Life & Environmental Sciences, thinks it's excellent that CMN research has sparked interest in forest fungus, but it's crucial for the general public to recognize that many popular beliefs are in advance of the science.

Although the existence of CMNs has been established by science, the researchers argue that there is insufficient proof that these networks are advantageous to trees and their offspring.

Karst and co-authors Melanie Jones of the University of British Columbia Okanagan and Jason Hoeksema of the University of Mississippi examined data from prior field research to assess the validity of the widely held assertions.

They discovered that there is insufficient scientific evidence to support one of the assertions, which is that CMNs are common in forests. With "too few woods surveyed," not enough is known about CMN structure and its role in the field.

The second assertion, that older trees use CMNs to transmit resources like nutrients to seedlings and that doing so increases survival and development, was similarly found to be dubious.

A review of 26 research found that while trees can move resources underground, CMNs don't always facilitate that flow, and seedlings often don't benefit from CMN access. The evaluation included one study on which Karst is a co-author. In general, their analysis found that there was about equal evidence that connecting to a CMN would benefit or harm seedlings, with neutral effects being the most frequently reported.

According to Karst and her co-authors, there is not a single field research that has been peer-reviewed and published that supports the third claim, which states that mature trees preferentially use CMNs to convey resources or "warning signs" of insect damage to young trees.

According to the researchers, exaggerated information can influence and skew the public narrative regarding CMNs, which may have an impact on how forests are managed.

"Because accurate science is essential for making decisions about how forests should be maintained, it is a concern when the science on CMNs in forests is distorted. Without more proof, it is premature to base forest practices and policy on CMNs per se. Additionally, ignoring false information might damage the public's confidence in science."