Agriculture & Climate Change, Canada (Commonwealth Union) – A long held view that trees communicate with each other via fungi has been challenged by researchers as it was indicated that the science those ideas were based on had no solid evidence, as indicated by the University of Alberta (U of A) expert Justine Karst who serves as Associate Professor, Faculty of Agricultural, Life and Environmental Sci – Renewable Resources Dept at the University, U of A.
A perspective that appeared in Nature Ecology & Evolution, Karst and 2 colleagues challenged 3 common claims regarding the capabilities of underground fungi known as common mycorrhizal networks, or CMNs, that link roots of multiple plants underground. Fungi are known as living organisms with examples like moulds, yeast and mushrooms.
CMNs have long been assumed to be underground networks of fungal threads or hyphae that connect the roots of different plants within a particular ecosystem. These networks form when mycorrhizal fungi colonize the roots of multiple plants, allowing them to share resources such as nutrients, water, and carbon.
“It’s great that CMN research has sparked interest in forest fungi, but it’s important for the public to understand that many popular ideas are ahead of the science,” said Associate Professor Karst.
Even though CMNs have had scientific evidence, there was no strong proof of them providing advantages to trees and their seedlings, as indicated by researchers.
In exploring the commonly held views, Associate Professor Karst and co-authors Melanie Jones of the University of British Columbia Okanagan and Jason Hoeksema of the University of Mississippi conducted reviews on evidence from the existing field research.
They discovered that one of the claims, that CMNs are extensive in forests, is not backed by sufficient scientific evidence. There was insufficient evidence in regards to the CMN structure and function in the field, with insufficient forests mapped, as well just 2 studies revealing common fungal connections among trees. If those links continue long enough to be advantageous to the trees is not known, according to Karst and her co-authors.
The 2nd claim, that resources like nutrients are sent by adult trees to seedlings via CMNs and that they enhance the survival and growth, also indicated doubts.
A review of 26 studies, consisting of one that Karst is a co-author, confirmed that even though resources could be moved around underground by trees, CMNs do not necessarily facilitate that flow, and seedlings typically have no advantage from CMN access. In general, their review showed roughly equal proof that linking to a CMN will enhance or hamper seedlings, with neutral effects most commonly indicated.
The 3rd claim, that adult trees prefer to send resources or “warning signals” of insect damage to young trees via the CMN, has no peer-reviewed studies, published, according to Karst and her co-authors.
A single published study they discovered that investigated tree signaling via CMNs in response to insect attack had been an experiment on potted seedlings within a greenhouse. The experiment demonstrated that the part the CMN had in signaling was cut off when roots of neighboring seedlings were able to interact, and “CMNs in forests were absent with no roots according to Associate Professor Karst.
Associate Professor Karst along with her colleagues made recommendations for some approaches to researchers in forming future CMN field studies that may explore alternative explanations and guarantee accurate interpretations of results.
Researchers further indicated that fungi extract nutrients and water from the soil and transfer them to the trees, further guarding roots from pathogens. And by utilizing and retaining carbon from the trees, the fungi is a further advantage to the forest.
“Mycorrhizal fungi are essential for the growth and survival of trees, and have an important role in forest management and conservation practices,” explained Associate Professor Karst, “even if trees are not talking to each other through CMNs.”
